Hermann Oberth

Chapter 1 · 1894 – 1906 Jules Verne’s Cannon

During the winter of 1905–1906, in Schässburg, a small town in Transylvania, an eleven-year-old boy read two novels by Jules Verne, From the Earth to the Moon and Around the Moon. In them, three travelers shut themselves inside a shell that a giant cannon, the Columbiad, fires at the Moon. Hermann Oberth was not satisfied with the story. He took a pencil and checked the figures. Sixty years later, before an astronautical congress, he would begin the account of his life with that winter.

A doctor’s son in Transylvania

Hermann Julius Oberth was born on June 25, 1894, in Hermannstadt, the town Romanians call Sibiu. Transylvania then belonged to Austria-Hungary. His family were Transylvanian Saxons, a German-speaking population settled there since the Middle Ages. His father, Julius Oberth, was a physician and surgeon. His mother, Valerie, née Krasser, was the daughter of a doctor who also wrote, Friedrich Krasser.

Two years after Hermann’s birth, the family moved to Schässburg, today Sighișoara, where the father ran the hospital. The child grew up in a house where science was talked about. Oberth would remember a friend of his father’s, Dr. Fritz Kraus, the town physician, “a man with an incredible amount of knowledge”: the conversations between the two doctors, he wrote, were always of the greatest interest. The boy also read Kosmos, a popular science magazine, every month. He cared about these details. In 1958, someone had written that he had acquired little general education by the age of thirty. He answered with that note, nine years later.

Checking Jules Verne

Verne states that the shell must leave the cannon at twelve thousand yards per second to escape the Earth. Is that true? At eleven, Oberth did not know calculus, the tool mathematicians use for this kind of problem. So he invented a method within his reach.

The difficulty is that gravity weakens as one moves away from the Earth. Oberth cut the journey into small intervals. Over each one, gravity changes so little that it can be treated as constant. He then made two calculations. In the first, he took for each interval the strongest gravity, the one at the start. In the second, the weakest, the one at the end. The true answer necessarily lies between the two results. And Verne’s figure did fall between the two bounds. The flight time given by the novelist was correct, too.

The boy had just rediscovered, alone, what is called escape velocity: the speed an object must be given so that it never falls back to Earth, about eleven kilometers per second.

Twenty thousand times his weight

The second calculation was less kind to Jules Verne. The cannon in the novel is three hundred meters long. To go from zero to eleven thousand meters per second over so short a distance, the shell must undergo an enormous acceleration. Oberth calculated it. Each passenger would be crushed by a force greater than twenty thousand times his own weight.

Verne had foreseen the difficulty. He had placed under the travelers a “water buffer” meant to cushion the shock. Oberth understood that it was useless. Even if skin and bones were protected, the organs inside the body would not withstand such pressure. The cannon would kill its passengers before they left the barrel.

Something else was needed, then. A machine that gathers its speed little by little, over several minutes, and keeps pushing once outside the atmosphere, where there is no air to lean on. Verne himself gives the idea without meaning to: in the novel, the travelers carry powder rockets to slow their fall onto the Moon.

“I saw no other way”

Oberth did not fall in love with the rocket. He said so plainly in 1967. He was driven to it, almost against his will. He disliked the rocket for two reasons. It may explode. And it demands a quantity of fuel out of all proportion to the rest of the craft: to carry a small cabin, one needs an immense tank. But no other means allows a slow climb and a push in a vacuum. “I saw no other way,” he summed up.

That was the starting point. At eleven, in a provincial town of an empire that would soon cease to exist, a schoolboy had shown that Verne’s cannon is impossible and that the rocket is the only road to the Moon. He still had to understand how a rocket moves. That was the subject of his thinking in the years that followed.

Sources: H. Oberth, “My Contributions to Astronautics” (paper read at the 18th International Astronautical Congress, Belgrade, September 1967), in First Steps Toward Space, Smithsonian Annals of Flight no. 10, 1974, p. 129 and note 7; entry “Oberth, Hermann,” Kulturstiftung der deutschen Vertriebenen; biographical entries collected by Encyclopedia.com.

Chapter 2 · 1906 – 1912 The Boat and the Pole

A boat touches the shore of a lake. A man jumps onto the bank. At the same instant, the boat moves backward. The man has gone one way, the boat the other. Every schoolboy in Schässburg had seen that. Hermann Oberth recognized in it the principle of the machine that would go into space. He only had to show that the boat would also move back if there were no water, no bank, and no air.

Cutting a pole into pieces

The reasoning he followed was a child’s, and he told it just so in 1967. Imagine, he said, a long pole floating in space. A pilot sits at one end. He cuts off a piece of the pole and throws it backward. The piece goes one way. The pilot and the rest of the pole go the other, a little more slowly because they are heavier. The pilot does it again. With each piece thrown, his speed increases.

Does the piece need to strike something for this to work? No. What pushes the pilot is the act of throwing, not the arrival of the piece. Whether the projectile then meets a wall, some air, or nothing at all changes nothing: it has already left.

Last step: the pieces of wood can be replaced by objects as small as one likes, down to the molecules of a gas. A rocket is a pole that cuts itself into billions of pieces and throws them behind it at high speed. It needs no air to lean on. So it moves forward in a vacuum.

“A pound of propellant remains a pound of propellant”

The idea seems simple today. It was not so for the adults of the time. Oberth related that engineers and professors maintained, years later, that reaction cannot work in a vacuum. As late as 1927, a colonel who headed the German rocket station in East Prussia wanted to prove to him that space travel was impossible: in a vacuum, he said, the gases expand so much that they lose their mass. Oberth answered that a pound of propellant remains a pound of propellant, whether it is packed in a tank or scattered in space. Propellant is what a rocket burns and expels in order to move.

From these discussions he drew a sentence he kept all his life: what counts is not the quantity of knowledge a person has, but what he does with it.

A school with small headlights

Oberth attended secondary school in Schässburg, at the Bischof-Teutsch-Gymnasium. It was a school turned toward literature and ancient languages more than toward science. He gave it an image that has stayed famous: the school was like a car whose front headlights are very small, but which lights up very well the road already traveled.

He did learn there, between 1910 and 1912, the calculus he had lacked at eleven. He also bought himself a book, Mathematik für Jedermann, mathematics for everyone, by August Schuster. With these tools, he could redo properly the calculations of his childhood.

Lacking a laboratory, he worked on paper. He said so directly: as a student, he had few opportunities to experiment, and so he tackled the theoretical problems. As early as 1910, he was looking for the equations that describe a rocket’s trajectory, that is, the way its speed and altitude change while the engine burns, the air slows it, and gravity holds it back. He would finish that work only in 1929. Nineteen years for a single problem: that gives the measure of his tenacity.

The body first

One question concerned him as much as the equations. A rocket can start less brutally than a shell, but it must still accelerate hard for several minutes. Then, with the engine cut, its passengers weigh nothing. Can a human being stand both? No one knew in 1910. No airplane flew fast enough, no machine made it possible to try.

A doctor’s son, Oberth took the question seriously. For him, a ship that killed its crew was no better than Verne’s cannon. So he went looking for the answer with the means at hand. In Schässburg, those means came down to a diving board, a bottle, and the pool of the swimming school.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, Smithsonian Annals of Flight no. 10, 1974, pp. 129–130.

Chapter 3 · 1911 The Schässburg Swimming Pool

On a cold morning in the fall of 1911, Hermann Oberth was alone in the pool of the Schässburg swimming school. He was seventeen. He dived and crossed underwater. In the middle of the pool, something went wrong: he no longer knew which way was up. He swam toward what he took to be a wall. It was the bottom. He came close to drowning. When he surfaced, he had understood what a man would feel in a ship whose engine has just stopped.

The half-full bottle

The experiments had begun earlier, at the diving board. A body in free fall weighs nothing while it falls: that was the only way, in 1911, to do away with gravity for a fraction of a second. So Oberth jumped into the water holding a half-filled bottle, neck down, and watched what the liquid did during the fall. He saw it leave the bottom and float freely in the glass.

He tried again with other liquids and described these trials in his 1929 book. With mercury, the liquid metal gathers into a ball in the middle of the flask and touches the glass at only one point. With water, the opposite happens: the liquid climbs along the walls and pushes the air to the center. He notes that the trial succeeds only if the walls are already wet; otherwise the water has no time to rise. He tried again with pebbles lying at the bottom of a flask of water: they lift off the bottom. And a stone he let go of while jumping stayed beside him, motionless relative to his body, all the way to the water.

To make up for air friction, he specifies, one must hold the flask above one’s head and then bring it downward during the fall. The detail shows the care he took. This was no bather’s game.

What the flask teaches the engineer

These schoolboy observations have a very practical consequence, which he drew himself. In a ship in free flight, the fuel does not stay at the bottom of the tanks. It spreads over the walls and leaves a bubble of vapor in the middle. If the engine is to be restarted in space, the pipe that draws the liquid must therefore not open at the center of the tank: it would find only gas there. Oberth wrote this in 1929. Engineers would meet the problem again thirty years later, when real engines had to be restarted in orbit.

He also drew from it an answer to his doctor’s question. A few seconds without weight do no harm. He concluded that a man can stand weightlessness.

The bottom taken for a wall

There remains the fall morning. Underwater, the weight of the body is almost canceled by the buoyancy of the liquid. Oberth lost all bearings. He was not falling, he was not rising, nothing showed him the vertical. He headed for the bottom, believing he was reaching the edge.

Afterward he thought over what had happened, as he had thought over Verne’s cannon. He deduced that our sense of orientation rests on three pieces of information: an organ of the inner ear, the tensions in our muscles, and the pressure our weight exerts on the skin, under the feet or against a seat. Underwater, that morning, these bearings had failed him. He had lived through, he would say, the psychological experience of weightlessness.

He remembered it when he wrote. In the short story he slipped into his 1929 book, the narrator, once the engine is cut, discovers that what he took for the left is the right, and that he is lying in quite a different position than he believed. It is the Schässburg pool, carried halfway to the Moon.

A method

These episodes have one thing in common. Oberth had neither laboratory nor funding. He took an everyday phenomenon, a jump, a bottle, a swim underwater, and put a precise question to it. He said so later about teaching: space travel rests on simple principles that we meet every day and, for that very reason, do not notice.

In 1912, he passed his school-leaving examination. His father wanted a doctor. Hermann left for Munich to study medicine. According to his biographers, he also attended physics lectures at the nearby technical institute. The rockets stayed in his notebooks.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 131–132; H. Oberth, Wege zur Raumschiffahrt (1929), NASA translation Ways to Spaceflight, TT F-622, 1972, pp. 138–140, 144–146, and 416; biographical entries (Kulturstiftung der deutschen Vertriebenen, New Mexico Museum of Space History).

Chapter 4 · 1910 – 1914 What the Formulas Say

Between the Schässburg school and the University of Munich, Hermann Oberth found three results. None requires an experiment. All come out of a few lines of algebra. The first says how fast a rocket should climb. The second says how much fuel it must carry. The third says why it must be stacked in several stages. He would not publish them until 1923.

Neither too fast nor too slow

A rocket rising vertically fights two opponents. The first is its weight. As long as the engine burns, part of the thrust serves only to keep it from falling back. The longer the climb lasts, the more fuel is wasted on that task. So one should climb fast.

The second opponent is the air. Its resistance grows as the square of the speed: twice as fast, four times the drag. So one should climb slowly, at least in the low, dense layers.

Between these two opposing demands, there is a speed that costs the least. Oberth found it: in vertical ascent, it is the speed at which air resistance exactly equals the rocket’s weight. He called it the most advantageous velocity. It increases with altitude, since the air thins out.

From this he drew a severe remark about his predecessors. All rockets built before 1920, he wrote, flew too fast. They were also too small. A cannonball is slowed less by the air than a rifle bullet, because its weight increases faster than its surface. A big rocket therefore crosses the atmosphere at lower cost than a small one. To go into space, one must think big.

The number 2.718

Second result. Take again the pole cut into pieces. What speed does the pilot reach in the end? It depends on only two things: the speed at which he throws the pieces, and the share of the pole he has sacrificed.

Oberth established the rule. For a rocket to gain a speed equal to that of its gases, it must weigh, full, 2.718 times what it weighs empty. This number, which mathematicians write e, turns up wherever a quantity shrinks in proportion to itself. To gain twice the speed of the gases, this ratio must be multiplied by itself: 7.389. For three times, about 20. The ratio between full mass and empty mass is called the mass ratio.

The rule is harsh, but it forbids nothing. It says that with gases fast enough and a rocket light enough when empty, any speed can be reached. Professors would later maintain the opposite. Oberth cites two of them, Kirchberger and von Dallwitz-Wegner, for whom the fuel does not even contain enough energy to lift its own weight out of the Earth’s gravitational field. The error lies in forgetting that the fuel does not travel all the way: it is burned and left behind en route, and it is the remainder that climbs.

Stages

Third result, which follows from the second. An empty tank is dead weight. If it is kept, it must go on being pushed. If it is dropped, the rocket that remains is lighter, and the same fuel gives it more speed. So a small rocket can be set on top of a big one. The big one burns, separates, and falls back. The small one lights up already possessing the speed acquired.

For Oberth, stages were not a separate invention. They come straight out of the mass-ratio formula. He would be astonished that a scholar as titled as Councillor Lorenz, of whom more later, declared he had never understood the principle.

He did not know, at that date, that others had found the same thing. In Russia, a schoolteacher in Kaluga, Konstantin Tsiolkovsky, had published the rocket equation in 1903. In the United States, a physicist in Worcester, Robert Goddard, obtained a patent for a multistage rocket in 1914. Oberth would hear of the second only in 1922, of the first only in 1924. Three men, in three countries, had reached the same point without knowing one another.

The formula and the calculating machine

In 1967, when computers were already calculating trajectories to the Moon, Oberth defended his old formulas. A machine, he said, gives a number for one particular case. A formula gives the general relation: it shows at a glance what happens if one changes the speed of the gases, the weight of the structure, or the burning time. It was thanks to the formula that he knew, years before touching an engine, what had to be pursued and what could be set aside.

He also had an image for the rocket of those years. It was, he said, like a gifted but poor boy with a small job in a large firm. No one suspects what he could do.

In 1914, war broke out. The medical student from Munich was called up.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 130–131; Ways to Spaceflight (1929, NASA trans. 1972), chapters 7 and 8; for Goddard, The Papers of Robert H. Goddard, vol. I.

Chapter 5 · 1914 – 1918 The Hospital, the Scopolamine, and the Ministry

In the fall of 1917, in the middle of the war, a medical sergeant sent the German Ministry of Armament the design of a long-range rocket. The device would burn alcohol and liquid air. The file included a mathematical appendix. In the spring of 1918, the manuscript came back to its author. The expert who had read it wrote that, according to experience, such rockets do not fly farther than seven kilometers.

From the infantry to the hospital

Called up in 1914 into the Austro-Hungarian army, Hermann Oberth served first in the infantry. On the Carpathian front, a piece of shrapnel wounded him in the abdomen. Once recovered, he was assigned to the medical service and spent the rest of the war at the hospital in Schässburg, his own town. In 1917, his brother Adolf died.

He said himself that for three years he had access to the drugs of a hospital and of a military pharmaceutical depot. For a young man who had been wondering since 1911 what weightlessness does to the brain, it was an opportunity. He would use it on the only experimental subject he had: himself.

Floating for hours

A jump from the diving board removes weight for only a second. Oberth wanted to know what happens afterward. So he sought to deceive his senses for long enough. The method he describes is as follows. He took substances that numb the organ of balance, lodged in the inner ear. Then he submerged himself, eyes closed, breathing through a tube. The water carried his body and removed the pressure on the skin. Deprived of his three bearings, he had the sensation of floating without weight, and could prolong it for hours.

In his 1929 book, he names one of these substances: scopolamine, an alkaloid drawn from certain plants. He adds at once that at the necessary dose it is already dangerous. He says he had known its effect since 1916 and had proposed it at that time as a remedy for seasickness.

He noted what he felt. In a jump, the absence of weight first causes a very brief fright; it does not appear when the sensation fades gradually, as under the effect of drugs. Then comes a drawing feeling in the chest, which disappears in about half a minute. The brain seemed to him to work very fast: the first two minutes, he writes, seem like four hours. Pain is dulled. He felt no nausea. Later came drowsiness. He adds a commonsense observation: with repetition, all these impressions fade. Perhaps, he concludes, weightlessness has no effect at all once it has become habitual.

These trials were nothing like a laboratory measurement, and he acknowledged it: our knowledge, he writes, is still very fragmentary. But he kept two convictions from them. A man can live without weight during a flight of a few days. For a flight of several weeks, it will be better to recreate gravity by spinning the cabin at the end of a long cable. On this point he stated a rule he would repeat: the aim of technology is to give man, in space, conditions that correspond to his nature.

The rocket of 1917

Meanwhile, the war dragged on. Oberth thought his rocket could be of use. In the fall of 1917, he sent the German Ministry of Armament a complete design. He described it thus fifty years later: a long-range rocket burning ethyl alcohol mixed with water, together with liquid air, somewhat similar to the V-2 of 1942, but larger and less complicated. The calculations were attached.

The answer came in the spring of 1918. The examiner did not discuss the equations. He relied on what he knew of the army’s powder rockets: they do not exceed seven kilometers. And he added, according to Oberth, that given the Prussian thoroughness with which the rocket station worked, nothing better could be hoped for.

The argument amounts to saying that a thing is impossible because it has not yet been done. Oberth would meet it often. In 1944, the German army would fire at London alcohol and liquid-oxygen rockets with a range of three hundred kilometers. He would take no simple pride in that, as we shall see.

Mathilde

In the summer of 1918, Hermann Oberth married Mathilde Hummel. The reference entries do not agree on the day: June 6 for one, July 6 for another. They would have four children, Julius, Erna, Ilse, and Adolf.

A few months later, Austria-Hungary collapsed. Transylvania was joined to Romania. Oberth, without having left his town, changed countries. His father lost his post as chief physician when Romanian became the official language. Hermann was twenty-four, with an unfinished medical degree, a rejected rocket design, and notebooks full of formulas. He would soon give up medicine.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 131–132; Ways to Spaceflight (1929, NASA trans. 1972), pp. 141–146; Hermann-Oberth-Raumfahrt-Museum (Feucht), “FAQ zur Person Oberth”; biographical entries (Encyclopedia.com; New Mexico Museum of Space History; Kulturstiftung der deutschen Vertriebenen). The date of the marriage differs from one entry to another.

Chapter 6 · 1919 – 1922 From Medicine to Physics

On May 3, 1922, from Heidelberg, a twenty-seven-year-old student wrote to an American professor he had never met. He had learned from a newspaper, he said, that he was not alone in working on the rocket. He asked Professor Goddard, of Worcester, to send him his publications. And he added a sentence that sums him up entirely: only the common work of scholars of all nations can solve this great problem.

Four universities

After the war, Hermann Oberth switched from medicine to physics. In 1919 he enrolled at the University of Klausenburg, the city Romanians call Cluj. Then he left for Germany: Munich, Göttingen, Heidelberg. These were then among the best universities in the world for mathematics and physics. His first son, Julius, was born in 1919. His daughter Erna was born in 1922.

He arrived with his notebooks. He had the equations of ascent, the mass-ratio rule, the principle of stages, his notes on the human body, and the 1917 design.

Closed doors

He approached, he said, German physicists and engineers. In vain.

In 1967, he came back to this failure at length. He describes the university professor as an overburdened man who has no time to examine every new idea brought to him. It should be added that the space rocket belongs at once to mechanics, chemistry, astronomy, and medicine: it falls within no specialist’s field.

Oberth drew a practical conclusion. Since scholars would not listen to him of their own accord, they had to be made to. And the only way to make them was to interest the public. If the newspapers talked about space travel, the professors would have to take a position. That decision explains everything that follows: the book, the pictures of the future he slipped into it, and even the cinema.

The letter from Worcester

It was in this context that he wrote to Robert Goddard. In 1919 the American had published, at the Smithsonian, a paper titled A Method of Reaching Extreme Altitudes. Newspapers around the world had retained a single page of it, the one where he considers sending a charge of flash powder to crash on the Moon. It was through that press echo that Oberth learned of his existence.

Goddard sent him the paper. On June 12, 1922, Oberth thanked him and promised to mention it in an appendix to his own work. He kept his word. The copy would be destroyed during the bombings of the Second World War.

What did he find in those pages? An experimental confirmation. Goddard had run small powder rockets in a chamber emptied of its air, and had measured the thrust. It is as strong in a vacuum as in the atmosphere. The pole cut into pieces, which the Schässburg schoolboy had imagined, was thus verified in the laboratory. Oberth said so in his books: the American physicist Goddard directly measured the thrust in a vacuum, by ingenious experiments.

A rejected thesis

That same year, Oberth submitted his work as a doctoral thesis at Heidelberg. The manuscript set out the theory of the liquid-propellant rocket and showed that a craft, and then human beings, can be sent beyond the atmosphere.

The thesis was rejected. Oberth related how it was returned to him. The man he dealt with was Councillor Max Wolf, the Heidelberg astronomer. Wolf explained that he could not accept it as an astronomy thesis: the subject belonged mainly to physics and medicine. But he handed him a certificate. In it he attested that the work was scientifically correct and ingenious.

That paper would matter. A doctorate would have opened a university career. Max Wolf’s certificate opened something else: a publisher’s door.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 132–133 and 136; letters from H. Oberth to R. H. Goddard (May 3 and June 12, 1922), The Papers of Robert H. Goddard, vol. I; Ways to Spaceflight (NASA trans. 1972), p. 4; biographical entries (Kulturstiftung der deutschen Vertriebenen; Encyclopedia.com).

Chapter 7 · 1923 Ninety-Two Pages

In 1923, the firm of R. Oldenbourg, in Munich, published a booklet of ninety-two pages. Its title: Die Rakete zu den Planetenräumen, the rocket into planetary space. The author, an unknown from Transylvania, had shown the publisher the certificate of the astronomer Max Wolf. He had also, according to his biographers, paid for the printing himself. In Worcester, Robert Goddard received his copy on July 19.

Four statements

The book opens with four statements, which reappear at the head of the 1929 edition. With the present state of science and technology, it is possible to build machines that can rise higher than the atmosphere. If perfected, these machines can attain such speeds that they no longer fall back to Earth and can even leave its attraction. They can be built so that human beings can ride in them, apparently without danger to their health. Finally, under the economic conditions of the day, it will pay to build them.

All the rest of the book serves to prove these four sentences. The order is that of a demonstration, not of a novel: first the laws, then the machine, then the uses.

Three parts

The first part is mathematical. It contains what Oberth had established since 1910: the most advantageous velocity for crossing the air, the ratio between full mass and empty mass, the gain brought by stages.

The second part describes a specific machine, which he calls Model B. It is a two-stage sounding rocket, meant to carry instruments to very high altitude. The lower stage burns alcohol diluted with water, together with liquid oxygen. The upper stage burns liquid hydrogen. Oberth does not settle for an overall drawing. He describes the chamber where the mixture burns, the nozzle through which the gases leave, the pumps, the tanks, the instruments.

The third part looks further. It presents Model E, a crewed ship, and what could be done with it: stations in orbit around the Earth, a telescope outside the atmosphere, a giant mirror that would send sunlight back to the ground. Oberth knew these pages would surprise. He admitted it in the foreword to the second edition: there, he says, he makes fantastic claims, of a kind seldom found in a scientific work, although they cannot be refuted.

Why so much detail

The original manuscript was more modest. Oberth wanted only to demonstrate that travel in space is possible. Then he imagined the answer he would get: it may be possible in theory, but technology cannot build that. So he added the technical solutions, one by one. For each foreseeable objection, an engineer’s reply.

He nevertheless kept some cards in hand. He acknowledged it in 1967: he kept certain ideas to himself so as to remain useful, later, as a consulting engineer. The swiveling engine, which steers the rocket by tilting its nozzle, does not appear in the book. Nor does the best distribution of mass among the stages: he wrote that down only in 1941, in a secret memorandum. Other finds are in the drawings without being commented on, such as the bell-shaped nozzle and the cooling of the wall by a thin layer of liquid.

The Cluj diploma

What Heidelberg had refused, Romania accepted. In 1923, Oberth submitted his work to the University of Cluj and passed the state examination that gave him the right to teach. He became a teacher of mathematics and physics in Transylvania, first in Schässburg, then at the secondary school in Mediasch, the town Romanians call Mediaș. He would stay there, with interruptions, until 1938.

Here, then, is the situation at the end of 1923. The book that founds the theory of spaceflight in Europe has just appeared. Its author has no German doctorate, no laboratory, no patron. He earns his living teaching schoolboys in a small Romanian town. To do experiments, he has only his salary.

He had one weapon left: the book itself. Ninety-two pages is not much. But they would be read in Vienna, Berlin, Moscow, Paris, and Worcester, and none of those readers would forget them.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 133 and 136; Ways to Spaceflight (NASA trans. 1972), p. 1 and foreword to the second edition (May 1925); I. Sänger-Bredt and R. Engel, in First Steps Toward Space, pp. 217–221; letter from R. H. Goddard to Nature (September 9, 1924), The Papers of Robert H. Goddard, vol. I; biographical entries (Kulturstiftung der deutschen Vertriebenen; Encyclopedia.com).

Chapter 8 · 1923 The Solutions of a Man Without a Workshop

“It was no work of witchcraft,” Hermann Oberth said in 1967 of the inventions announced in his book. His formulas showed him what to pursue and what could be ignored. Without ever having built an engine, he described in 1923 nearly every part of a modern rocket. Here is how he got there, step by step.

Liquids, because the gases must leave fast

Everything starts from the mass-ratio rule. The faster the gases leave, the less fuel is needed to reach a given speed. The black powder of fireworks rockets gives slow gases. So substances are needed that release far more energy when they burn: alcohol or hydrogen, with oxygen. To carry enough of them in a small volume, they must be carried as liquids. Oberth therefore chose liquid propellants. A propellant is each of the two products a rocket burns together.

A thin wall, cooled by the fuel

The same rule demands a rocket that is very light when empty. Yet the flame of an oxygen engine exceeds the melting point of ordinary metals. The obvious solution would be to line the chamber with firebrick, like a furnace. Oberth rejected it: too heavy.

He proposed the opposite. The chamber would be of thin sheet metal, and the fuel itself would cool it before being burned in it. In his book, he describes a double wall. The liquid flows between an inner partition and the jacket, heats up there, partly vaporizes, and enters the chamber along the walls. This vapor forms a veil that insulates the metal from the burning gases. The heat taken from the wall is not lost, since it returns to the chamber with the fuel.

Two historians of the rocket engine, Irene Sänger-Bredt and Rolf Engel, have drawn up the account. They credit Oberth with the idea of film cooling, that veil of liquid along the wall. And they note that it was not carried out until 1938 and 1939, on the big engines at Peenemünde. It took fifteen years to build what he had written.

Pumps

For the gases to leave fast, the pressure in the chamber must be high. If the liquids are pushed toward the chamber by pressurizing the tanks, the tanks must withstand that pressure, and so be thick, and so heavy. Oberth separated the two: low-pressure tanks, light, and pumps that take the liquid and force it into the chamber. Large rockets would do the same.

Water in the alcohol, and the “Oberth effect”

Another way to spare the chamber: lower the flame temperature. Oberth added water to the alcohol. The flame is cooler, the engine holds. A little speed is lost, but one gains an engine that does not melt.

With hydrogen, he made a subtler discovery. If more hydrogen is put in than is needed to burn all the oxygen, the excess does not burn. It merely heats up. Since hydrogen is the lightest of gases, this surplus escapes very fast. The chamber temperature falls, and the exhaust velocity does not diminish. The Frenchman Robert Esnault-Pelterie would call this the “Oberth effect.”

Oberth states that he verified it in the 1920s. In Transylvania he could obtain neither liquid hydrogen nor liquid oxygen, and had no means of liquefying them. So he worked with gases, on a simple burner. He says he obtained exhaust velocities of 3,900 to 4,000 meters per second. He wrote about it to friends in Vienna. A professor at that city’s technical university had the reply sent that he must be a fraud: by his calculations, 3,200 meters per second could not be exceeded. In his 1929 book, Oberth answers a Viennese professor, Karl Wolf, who set the limit lower still: this critic, he writes, simply forgot the excess hydrogen. It must be noted that we know of these measurements only through him.

The list

The rest fits in a list, which he drew up himself in 1967. Burn heavy fuels in the lower stage and light fuels above. Stiffen the tanks by a slight internal pressure, like a balloon: the engineer Karel Bossart would apply this idea to the American Atlas rocket. Bring the stages back to the ground by parachute. Measure the acceleration in flight to cut the engines at the desired speed. Entrust steering to a gyroscope that commands control surfaces. Paint the cabin black on one side and leave it shiny on the other, to regulate its temperature by turning it toward the Sun. Purify the air in a spiral tube placed in the shade, where impurities condense in the cold. Train and select the travelers in a centrifuge with an arm thirty-five meters long.

To this he added, in the third part, the giant space mirror. About that one he would be frank: he put it in the book to offer the reader something sensational.

A man alone, without a workshop, thus drew on paper the rocket that thousands of engineers would build. What he could not do, and he would find it out the hard way in 1929, was make it with his own hands.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 133–136; Ways to Spaceflight (NASA trans. 1972), pp. 49–51; I. Sänger-Bredt and R. Engel, “The Development of Regeneratively Cooled Liquid Rocket Engines in Austria and Germany, 1926–42,” in First Steps Toward Space, pp. 218–221 and 228.

Chapter 9 · 1923 – 1944 Worcester Reads Munich

On August 1, 1923, in Worcester, Massachusetts, Robert Goddard opened the booklet he had just received from Germany. He found in it, he noted, practically the same theory as his own. He wrote that he would not be surprised if research soon became a kind of race. Between the American and the teacher from Transylvania, a twenty-year misunderstanding began.

What Goddard read

Goddard had been working since 1909 on the idea of a hydrogen and oxygen rocket. In 1914 he had obtained patents on the multistage rocket and on the liquid-propellant rocket. In 1919 he had published his paper at the Smithsonian. Since 1921 he had been trying, alone in his laboratory at Clark University, to burn liquid oxygen in a chamber. He had published nothing about those trials.

And now a stranger was setting out, in black and white, the liquid-propellant rocket, stages, pumps, crewed flight. That stranger had written to him fourteen months earlier to ask for his paper. Goddard made the connection. In August 1923, he gave the trustees of his university an eight-page report. The last four pages are devoted to Oberth’s book: in them he notes, point by point, what he himself had proposed or tried before. In December, he presented a short note to a scientific meeting in Cincinnati. He said he did it in self-defense.

In 1924, the journal Nature published a review comparing the two men. Goddard replied on September 9. He recalled his dates: a serious interest since 1899, hydrogen and oxygen considered in 1909, liquids published in a patent of 1914 and tested in 1921. He specified that Oberth had written to him on May 3, 1922, and that the book had reached him on July 19, 1923.

What Oberth wrote

On Oberth’s side, the texts say something other than borrowing. He always dated his ideas from before 1922: Verne’s cannon in 1905, the equations in 1910, the alcohol-rocket design sent to the ministry in 1917. That last point precedes by two years Goddard’s paper, which in any case dealt only with powder rockets.

In his books, he cites the American and gives him his due. He credits him with the experimental proof that thrust acts in a vacuum. He recalls that Goddard obtained, with nitrocellulose powder, gases ejected at 2,400 meters per second. He discusses one of his ideas for stabilizing a rocket by spinning it. He announces that he will speak of him at greater length in a second volume, which never appeared.

In 1967, he summed the matter up in one sentence. Between 1922 and 1928, he said, he finally learned that he was not alone. Goddard is the first name on the list.

Two ways of working

The sources do not allow one to say that Oberth took anything from Goddard. They show two men who reached the same conclusions through the same laws of physics. They also show two opposite methods, and it was this opposition that fed the American’s bitterness.

Goddard built and kept silent. He published only what he had verified on the test stand, and showed his machines to no one. On March 16, 1926, he would fly the first liquid-propellant rocket in history, in a field at Auburn. He would say almost nothing about it for ten years.

Oberth calculated and published. He had no workshop, but he put everything on the table: the equations, the diagrams, the uses, the dreams. His book was made to be discussed, criticized, taken up. And it was. Within a few years, German-speaking Europe was covered with books, lectures, and amateur societies that claimed him as their source.

Goddard took it badly. In June 1927, after reading Oberth and his popularizers, he noted that in each of these books America’s contribution was belittled. In April 1930, he wrote to a journalist that Oberth had made only two tests, both failures, and that the film studio financing him had stopped paying. That was accurate, as we shall see. As late as 1944, he sent a friend a photostat of the 1922 letter. Like a good New England Yankee, he added, he had kept the envelope too.

The division

In hindsight, each brought what the other lacked. Goddard proved, piece by piece, that the liquid-propellant rocket works. Oberth showed everyone what it would be for and how to calculate it. The rocket that, in 1942, would climb for the first time to the threshold of space was built by pupils of the second, with solutions that the first had almost all tried before them.

Oberth, for his part, never wavered from the sentence in his first letter: the problem can be solved only by the common work of scholars of all nations. The rest of the century would prove him right in an unexpected way, through a war and then a rivalry between two empires.

Sources: The Papers of Robert H. Goddard, vols. I–III (notes of August 1, 1923; report to the Clark trustees, August 1923; letter to Nature, September 9, 1924; diary, June 6, 1927; letter to W. Kaempffert, April 18, 1930; letter to G. E. Pendray, November 14, 1944); chapter on Goddard in First Steps Toward Space; H. Oberth, Ways to Spaceflight (NASA trans. 1972), pp. 4, 50, and 269; “My Contributions to Astronautics” (1967), pp. 131 and 136. See also, on this site, the biography of Robert Goddard.

Chapter 10 · 1924 – 1927 “I Was Not Alone”

In 1925, in Mediasch, Professor Oberth received from Russia a book printed in Kaluga the year before. The author’s name was Konstantin Tsiolkovsky. Oberth did not read Russian. One of his pupils, Arzamanoff, a Russian émigré, helped him translate. He then discovered that a provincial schoolteacher had written the rocket equation twenty years before him.

The popularizers

The 1923 book is dry. It is full of formulas, and its author did nothing to soften them. Other pens would carry it to the general public. Oberth names them himself: Max Valier, Otto Willi Gail, Willy Ley, Karl August von Laffert, Felix Linke.

Max Valier, a Tyrolean, published as early as 1924, with the same publisher, Der Vorstoss in den Weltenraum, the advance into space. Willy Ley, a young Berliner, brought out Die Fahrt ins Weltall, the journey into space, in 1926. Otto Willi Gail wrote novels, among them The Shot into the Universe and The Stone from the Moon, in which ships built on Oberth’s principles go to the Moon and to Venus. Oberth liked the second well enough to quote several pages of it in his own book, correcting the errors of physics in footnotes.

The plan conceived at Heidelberg was working. The public was taking an interest in space travel, and the scholars would have to respond.

Kaluga, Essen, Berlin

Fame also taught him that he had predecessors and companions. After Goddard in 1922, here was Tsiolkovsky. Oberth heard his name for the first time in 1924. The following year, the old Russian scholar sent him his book, The Rocket into Cosmic Space. Oberth always acknowledged that priority. He noted that Tsiolkovsky himself had been recognized only after 1924.

In Essen, a city engineer, Walter Hohmann, had calculated for his own pleasure the trajectories that lead from one planet to another with the least fuel. He had not dared publish, for fear of ridicule. Seeing that such far-out ideas could be printed, he made up his mind. His book, Die Erreichbarkeit der Himmelskörper, the attainability of the celestial bodies, appeared with Oldenbourg in 1925. Oberth regarded it as fundamental and defended it against its critics. Hohmann’s trajectories are still used today to plan flights to Mars.

In 1926, Oberth finally learned of the existence of Hermann Ganswindt. This Berlin inventor had proposed, in 1895 according to Oberth, a ship driven by reaction; a helicopter and a freewheel are also owed to him. Oberth wrote a bitter sentence about him in 1929: Germany possesses the peculiar gift of producing great men and then letting them perish through neglect.

Other readers made themselves known. In Vienna, a civil engineering student, Eugen Sänger, reworked the book’s calculations and became convinced they had to be taken seriously: he would devote his life to the rocket plane. In Prague, the inventor Ludvík Očenášek corresponded with Oberth and received him. In Paris, Robert Esnault-Pelterie, a pioneer of aviation, discovered the book through his readers’ letters.

The second edition

In May 1925, in Mediasch, Oberth signed the foreword to a second edition. In it he explains why he wanted to draw the attention of wide circles: it was the only way to hope for the means and the opportunity to continue his work. He also defends the value of the subject for teaching. The rocket, he writes, rests on simple principles that we meet every day and no longer notice. A teacher can use it to lead his pupils to clarify what they think they know. He quotes the Greek word Aristotle uses for wonder, the source of all science.

It is a schoolteacher speaking. He taught mathematics and physics in Mediasch, he had a wife and children, and he went on with his calculations. His daughter Ilse was born in 1924.

Breslau, June 5, 1927

On June 5, 1927, in Breslau, a few enthusiasts founded an association: the Verein für Raumschiffahrt, the Society for Space Travel. Among the founders were Max Valier and the engineer Johannes Winkler. The society published a monthly magazine, Die Rakete, the rocket. The aim was simple: to raise money to move from books to tests.

Oberth became a member. He wrote in its pages and answered his critics there. Two years later, he would be its president. Around this society would gather, in Berlin, the young men who built Germany’s first liquid-propellant rockets: Rudolf Nebel, Klaus Riedel, Rolf Engel, and a schoolboy named Wernher von Braun.

In four years, the author of a booklet rejected by the university had become the center of a movement. He still lacked the essential thing: an engine that worked.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 131, 136 and notes 12–16 and 20; Ways to Spaceflight (NASA trans. 1972), foreword to the second edition (May 1925) and pp. 148–149, 424–435; I. Sänger-Bredt and R. Engel, in First Steps Toward Space, pp. 217, 219, and 229; chapters on Esnault-Pelterie and on Očenášek, same volume; biographical entries.

Chapter 11 · 1927 – 1928 The Objections

On May 7, 1927, the journal of the Association of German Engineers published an article titled “The Possibility of Space Travel.” Its author, Councillor H. Lorenz, was the association’s second chairman. His conclusion was negative. Two supplements followed in August. Hermann Oberth asked to reply in the same journal. He was refused. He would have to do it in the small magazine of the Breslau society.

Councillor Lorenz

Oberth told the story of this controversy forty years later with undiminished liveliness. Lorenz, he says, invented one objection after another. In one calculation, he had forgotten that propellants possess not only chemical energy: they also have the energy of their motion, since they travel with the rocket before being burned. In another, he had integrated over the wrong intervals, a mistake for which, Oberth notes, he would probably have failed one of his own students. Finally, he rejected the trajectory inclined toward the east, which Oberth recommends in order to benefit from the Earth’s rotation: every sensible human being, Lorenz wrote, understands that a rocket is most efficient when it always thrusts straight up.

Why such persistence? Oberth offers an explanation: Lorenz had once said that spaceflight was impossible, and did not want to retract.

The reply appeared in Die Rakete in November and December 1927, under the title “Is Space Travel Possible?” The two men also debated face to face before the Scientific Society for Aeronautics. The physicist Theodore von Kármán, who would become one of the fathers of jet propulsion in the United States, left an account of it in his memoirs.

The colonel, the major, and the professors

Lorenz was not alone. Oberth kept the list of his opponents.

There was the colonel from East Prussia, already met, for whom gases lose their mass in a vacuum. There was a major from the Ministry of Armament, who still insisted to him in 1928 that rockets flying farther than artillery shells would be of no military interest. There was Professor von Dallwitz-Wegner, who wrote that a man jumping from a train moving at a hundred kilometers an hour undergoes a change of speed of thirty meters per second squared: he was confusing speed with acceleration. There was Professor Karl Wolf, of Vienna, for whom the speed of the gases could not exceed two kilometers per second.

And there was Professor Kirchberger. In 1928, the industrialist Fritz von Opel ran a car propelled by powder rockets. The machine wastes nearly all its energy, because a rocket works well only when it moves about as fast as its gases leave. Opel knew that. Kirchberger, however, measured the car’s efficiency, carried it over into a calculation for a space rocket, and concluded that space travel is impossible. Or at least, Oberth slips in, that he himself could not have invented it.

Opel and publicity

Opel’s rocket car inspired mixed feelings in him. When he met the industrialist, the latter said at once: Professor, do not judge me only by the rocket car; I do serious work, too. Opel was only after publicity, and he got it. Public interest was greatly stimulated. Oberth, who had himself staked everything on the public, could not hold it against him.

He was harder on Max Valier, who had pushed Opel in that direction. In his 1929 book, he writes that hundreds of thousands of marks had been blown into the air at Valier’s instigation without bringing anyone closer to the rocket plane, whereas fewer than ten thousand would be enough for him to finance the preliminary tests of a liquid-propellant engine.

Danzig, June 4, 1928

Oberth did not only defend himself. On June 4, 1928, at the convention of the Scientific Society for Aeronautics, in Danzig, he proposed building a machine. It was the centrifuge he had already called for in his 1923 book: a long metal arm turning on rails, with a small car at the end where the subject sits. The radius must exceed sixty meters, so that the person feels a nearly vertical force and not a spinning. One would know at last what a human body can stand, and for how long.

He attached a financing idea that is just like him: if the apparatus stood in the Vienna amusement park or a similar place, there would always be people willing to pay a few pence for a ride. Railway engineers objected that the wheels would not stand such speed. He answers them in his book, point by point. Nothing indicates that the machine was built. The centrifuges in which astronauts would train, thirty years later, would use the same principle.

What he kept from it

Oberth came out of these years of quarrels disappointed. He said so without disguise. Until then, he had had a kind of worship of research, and had considered German scientists the best in the world. He was amazed, he says, to discover in some of them the lack of general education, the indifference to new ideas, the vanity and self-complacency.

That wound never closed. In 1967, he used it to defend, before an astronautical congress, causes that scientists reject: a German pastor’s Atlantis, parapsychology, unidentified flying objects. His reasoning amounts to this: they were wrong about me, so perhaps they are wrong about them. The reasoning is no proof, and this book will return to it.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 130–131, 136–138 and notes 2, 3, and 19; Ways to Spaceflight (NASA trans. 1972), pp. 49–50, 133, 136–138, and 406.

Chapter 12 · 1928 – 1929 Ways to Spaceflight

In September 1928, in Mediasch, Hermann Oberth signed the foreword to the third edition of his book. The ninety-two pages of 1923 had become more than four hundred. The text had changed so much that the publisher advised a new title. It would be Wege zur Raumschiffahrt, ways to spaceflight. At the front, a dedication: to Thea von Harbou and Fritz Lang.

A book recast

The work appeared in 1929 with Oldenbourg, in Munich and Berlin. It has twenty-two chapters in four parts. The first sets out the reaction principle and describes the machine. The second contains the physics: the speed of the gases, the mass ratio, the most advantageous velocity, what the human body can stand, the ascent calculations, energy, steering, landing. The third deals with construction, with Model B and its variants. The fourth lists the uses, from the meteorological rocket to travel to other planets, and ends with an electric spaceship.

In the foreword, Oberth explains what he added. Since 1923, he writes, notable work had appeared on rocket theory, and he did not want to leave it unconsidered. He pays particular tribute to the book the Frenchman Robert Esnault-Pelterie had just devoted to the exploration of the very high atmosphere by rockets, which he considers one of the most important on the subject. He also included an account of his own work and a reply to objections.

Finally he thanks the man who read the proofs, Alexander Scherschevsky, a Russian student living in Berlin, who pointed out obscure passages and enriched the book with several additions. Scherschevsky would be his assistant during the tests of 1929.

Three objections, three answers

The foreword sets the tone. In a few lines, Oberth dispatches three criticisms he considers less than serious.

He is told that a parachute may not open when a ship returns. He answers that before reentering the atmosphere the passengers weigh nothing: they can arrange the parachute by hand in the required position.

He is told that a spaceship is as dangerous as a powder magazine in which one handles an open flame. He answers that it carries no explosives, only flammable liquids kept in separate tanks.

He is told, lastly, that reaction cannot act in a vacuum, because the gases expand there without limit and lose their mass. One recognizes the colonel from East Prussia. Oberth no longer even answers.

He announces a second volume, which was to deal with history, experiments, and these minor objections. That volume never saw the light of day.

The Paris prize

In 1928, news came from France. Robert Esnault-Pelterie and the banker André Louis-Hirsch had just founded, under the auspices of the Société astronomique de France, an international astronautics prize. It was the first time a learned society recognized that this new science had a future. Oberth sent his manuscript. The jury crowned it in the very first year. The award was announced at the society’s general assembly on June 5, 1929.

Esnault-Pelterie explained the choice. Oberth, he said, was the first to show that it is technically possible to eject a rocket’s gases at more than four thousand meters per second. The Frenchman himself took up the mathematical demonstration in his major book of 1930.

Oberth added an epilogue of a few lines on the last page. Ten years after the war, a French jury had just honored a German-language author. He was moved, and said so simply. Frankly, he writes, he did not believe that in France such a prize would be awarded to a German, the more so since good French, Russian, Italian, and English works were at hand. He finds it encouraging to see that science and education are able to bridge national differences. And he promises, to thank the Société astronomique de France, to work in his turn for science and education, and to judge a man only by his achievements.

“The paper is patient”

This thick book is not a cold treatise. Oberth argues in it, mocks, tells stories. He knows he is describing machines no one has built, and says so with humor. About the parachute landing of a stage, he writes: the paper is patient, and in this book certainly no accident will happen.

He also distinguishes, with care, three kinds of statements: suppositions, ascertained knowledge, and basic considerations. When he speaks of the speed needed to reach Mars, he calculates. When he speaks of what will be found there, he warns that he is supposing.

German readers later nicknamed it the bible of astronautics. The chapters that follow go through its liveliest pages: the human body, a flight around the Moon, the space suit, the station, the mirror, the Moon, and Mars.

Sources: H. Oberth, Wege zur Raumschiffahrt (Munich and Berlin, R. Oldenbourg, 1929), NASA translation Ways to Spaceflight, TT F-622, 1972: dedication, foreword (September 1928), table of contents, pp. 409, 507, and 576; chapter on Robert Esnault-Pelterie in First Steps Toward Space, p. 11 and notes 40–42; I. Sänger-Bredt and R. Engel, same volume, pp. 225–226.

Chapter 13 · The 1929 book What the Body Can Stand

A diver leaves the board, crosses the air, and enters the water feet first. In a fraction of a second, his speed drops almost to zero. Hermann Oberth watched the scene frame by frame, on sport films that had just been sent to him. On the screen he measured the distance covered from one frame to the next, using the swimmer’s height as his ruler. From that he deduced the force the body had undergone. It was far greater than had been thought.

“Counter-pressure”

Chapter 9 of his book is a doctor’s son’s chapter. It deals with a quantity he calls counter-pressure. This is the force with which our seat, or the ground, presses on us. When we are at rest, it equals our weight. In an accelerating rocket, it increases: we feel two, three, four times heavier. With the engine cut, it disappears: we weigh nothing. Today one would say he is counting g’s.

The question is twofold. Up to what counter-pressure does a man hold out? And what becomes of him when there is none at all?

How many times his weight

For the first question, Oberth gathers everything he can find. Divers, first: by his measurements on film, the deceleration on entering the water is one and a half to two times greater than the accepted figures. He warns that his measurements are rough and that it would be worth repeating them with slow-motion shots. Then aviators, who take heavy loads in tight turns. And tests made in Breslau by a certain Wittkuhn, on rotating machines.

He concludes that a man lying down can stand several times his weight without harm during the few minutes the ascent lasts. In passing he settles a score with Max Valier, who had written that the heart would not be equal to the task. That is nonsense, he replies, and he demonstrates it. The blood circulates in a closed loop. The extra work needed to raise it on one side is given back on the other, where it descends. He compares the system to a pump circulating water in a circular pipe: its effort hardly depends on gravity.

Slow is worse than abrupt

Oberth then observes something subtler. Not all accelerations are equal for our nerves. A weak, hesitant acceleration is more unpleasant than a strong, clean one. An elevator stopping, a boat rising on a wave bring on nausea. A jump into the water, far more violent, does not. He compares this to tickling: a light touch tickles more than a firm pressure.

He applies the remark to Opel’s rocket car. If its drivers were so affected, it was not because it started too hard. It was almost, he writes, because it started too gently: its acceleration fell right in the unpleasant zone. A real rocket will have to avoid it.

He also notes the part played by the mind. An acceleration one expects is easier to bear, and easier still one that one has the impression of wanting. A voluntary dive does not have the effect of an involuntary fall. Hence an old rule he quotes: when working on a roof, climbing a mountain, or flying, do not reflect on your position.

Without weight

For the second question, he returns to his Schässburg experiments, the flask of mercury, the stone let go during the jump, the hours spent underwater. He adds a distinction that remains correct.

A few hours or a few days without weight can do no harm, he writes. We live as well lying down as standing, on our back as on our stomach: our body does not depend on a direction of gravity, unlike plants. But if weightlessness lasted for weeks, muscles and ligaments would weaken for lack of use, and the return to Earth would become dangerous. The physicians of orbital stations would observe exactly that, from the 1970s on.

His remedy fits in a sentence. For a long voyage, the cabin will be connected to the rest of the ship by a cable, and the whole will rotate. Centrifugal force will replace gravity. The cable will have to be very long, so that the rotation is slow and the passengers do not notice it.

An error of Jules Verne’s

He ends by returning to his first teacher. In Around the Moon, the travelers float inside the shell only for a moment, at the point where the Moon’s attraction balances the Earth’s. That is wrong, Oberth explains. One floats as soon as the engine stops, wherever one is, and however strong gravity may be. The cabin and its occupants fall together, at the same speed. Nothing presses on anything anymore.

He illustrates this with a small drawing: a figure released at the same time as a frame of laths stays in the middle of the frame throughout the fall. It is the jump from the Schässburg diving board, put down neatly on paper.

Finally he asks for help. Our knowledge of these effects, he writes, is still very fragmentary, and he would be thankful for any information. He only wanted to show that the question can be prepared without waiting for the first flight.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), chapter 9, pp. 116–150.

Chapter 14 · The 1929 book The Flight of the Luna

In the middle of his treatise, between two chapters of formulas, Hermann Oberth stops. Before discussing his crewed ship, he writes, he would like to give the reader a vivid description of a flight in space. He then reproduces long excerpts from a short story he had composed. In it a passenger tells of his trip around the Moon aboard a rocket christened Luna. The account is fiction, and Oberth presents it as such. But every detail in it serves to explain a law of physics.

Calcutta, automobiles without fumes

The narrator is a professor in charge of the astronomical observations. The pilot is a mechanical engineer named Müller. The rocket is thirty-five meters long and ten in diameter. It consists of an alcohol rocket carrying two hydrogen rockets, and it can reach thirteen kilometers per second. Before taking men, it flew uncrewed to an altitude of 4,200 kilometers, to test its automatic control apparatus. Then Müller went up alone to 5,000 kilometers.

The departure takes place in India, from the sea. Oberth imagines liquid hydrogen and oxygen plants set up on the upper Brahmaputra. Arriving in Calcutta, the narrator is surprised to see so many automobiles that make neither fumes nor noise. Müller explains that the plants could not stand idle between two launches. So the hydrogen was sold to industry, and the city’s cars now run on hydrogen engines. Demand is such, he says, that the plants have to be enlarged almost every month.

Filling the tanks

A steamer, the Tagore, tows the rocket out to sea. It floats lying flat on the water. First, freshly vaporized hydrogen is blown through its tanks, to cool them little by little. Oberth takes the opportunity for a lesson: if an icy liquid were poured all at once into a lukewarm tank, the metal would burst like a hot glass under cold water. As the tanks fill, the rear sinks and the rocket rights itself, until it stands upright in the sea, covered with a thick layer of ice.

The two men shut themselves in the cabin. It is almost dark inside: a little daylight enters through the periscopes. Müller adjusts the control gyroscopes to within a second of arc. They stretch a hammock across the middle of the cabin and lie down on it. The metal, chilled by the hydrogen, rings like a hundred bells under the boiling of the liquids, and the waves rock the rocket.

Five minutes

Ignition is electric. A jolt, and the rocket rises from the water. A mechanism bursts the shell of ice, which falls back into the sea like the breakup of a river. The thrust presses the narrator into the hammock. Through the periscope he sees a crater ringed with foam on the sea, where the gases strike. Twenty-five seconds later, the rocket passes through the clouds. One more minute, and the peaks of the Himalayas rise on the horizon, more than a thousand kilometers away.

The alcohol rocket is exhausted and drops away. The first hydrogen rocket takes over. The narrator feels as if he were on the back of a huge beast trying to get up, and the pumps sound like its breathing. Then comes the last stage, the one their lives depend on: the best engineers worked on it for nearly a year. The narrator no longer feels himself accelerating. He only feels very heavy and very thin.

The engine stops. Two seconds later, he is floating in the middle of the cabin, with the feeling of coming out of a doze. What he took for the left is the right.

A brown sky

The two men roll up the hammock and uncover the windows. The Sun is a blinding disk in a completely black sky. Shielding his eyes, the narrator gradually sees the stars, brighter than on the darkest night. The background of the sky does not look blue-black to him as it does at home, but brownish, like a sooty porcelain plate. On one side, the Earth bulges like an enormous boiler and takes up a third of the sky. On the other, the Sun is surrounded by an elongated glow, the zodiacal light, and by rays, the corona, which is seen from the Earth only during eclipses.

Later, the Earth is no more than a disk. Oberth describes it with a painter’s care: the rim an intense red, edged with a fine blue border; the auroras set on the poles like crowns; the blue oceans, the dark green tropics, the yellow deserts, the pale green steppes; and over it all, white clouds that look, from there, like pollen on a flower. No one, in 1929, had seen this. The first photograph of the whole Earth would be taken nearly forty years later.

The soup, the pill, and the drop of water

Life on board gives rise to scenes of comedy, all of them instructive. Soup is drunk by sucking it through wide aluminum tubes from spherical, almost closed containers. The narrator, his throat tight with the emotion of the first flight, cannot swallow. Müller slips a pill into his mouth and puts a bottle of raspberry juice to his lips. The professor asks for a tumbler. Müller laughs and hands him one: go on, try pouring. The water refuses to come out, then gushes, bounces off the glass, and scatters into round drops that fly about the cabin like a swarm of mosquitoes.

Müller then catches a ball of water on the tips of his wet fingers and lets it float in front of him: this, he says, is the model of a celestial body. He runs a rubber comb through his hair to electrify it and brings it close. The drop begins to circle the comb in an elongated ellipse. There you have, he concludes, Kepler’s laws.

At night, one sleeps by slipping an arm and a leg into two leather loops fixed to the wall. The narrator dreams he is an antediluvian monster that has swallowed the Earth.

Up and down

On the third day, some fifty thousand kilometers from the Moon, he measures their position: they will pass five hundred kilometers too close. The error is corrected by giving the rocket a push of 1.35 meters per second. The maneuver takes barely a minute. But during that minute, the engine has pushed. When it stops, the narrator no longer finds the sky where he left it. The Moon, which was above, is now below. Yet nothing has turned. For him, he writes, the Earth would be “below” again only at the moment the Luna rocked once more on the ocean.

Oberth annotated his own story. In footnotes he points out his faults as a novelist: the pilot and the astronomer should not explain to each other what each already knows, but without that the reader would understand nothing. He notes that when he wrote it he did not yet know the best ascent trajectory. And he adds that he would already be able to build a rocket half the size.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), chapter 19, pp. 410–424.

Chapter 15 · The 1929 book The Space Divers

In Hermann Oberth’s short story, the pilot Müller says to his passenger: it would be well if you put on your diver’s suit and stepped out with me, to learn to move about in space. The two men dress, open the door, and let themselves float beside the rocket, held by a cord. The year is 1929. The first time a man went outside in space was 1965.

A diver’s suit

Oberth does not use the words space suit. He speaks of divers and divers’ suits, because the only model he has is the harbor diver. The problem is the same, in reverse. The diver must resist the pressure of the water crushing him. The space diver must contain the air that tends to inflate him in a vacuum.

In the technical chapter, he specifies his idea. The suit will have to stand an inside pressure of one atmosphere. He would make it of thin, polished sheet metal, on the principle of deep-sea diving equipment but much lighter. For hands, claws. On the feet, hooks to hold on to the cables and rings fixed to the hull. The joints would be wrapped in canvas lined with rubber. To test it before departure, it would be enough to slip it inside a larger diving suit and pump out the space between the two.

In the short story, the version is more supple: rubber covered with thin strips of shining tin, to keep it from bursting, and a helmet half of which is transparent.

Breathing, talking, moving

Should the diver be supplied with air through a hose, as at sea? Oberth finds that impractical. He prefers a cylinder of compressed or liquid air carried on the back, enough to breathe for an hour to an hour and a half. The exhaled air passes through a tube filled with caustic potash, which absorbs the carbon dioxide.

He adds a trick. If the diver lets a little air escape through a valve, the reaction pushes him the other way. He thus has a small engine with which to steer. One of his popularizers, von Laffert, had even suggested reaction pistols. American astronauts would try such a pistol in 1965.

The diver does not float free. He is connected to the cabin by a hemp cable. Telephone wires are woven into the cable, since a vacuum does not carry sound. The two men in the story talk to each other that way, over the wire.

The cabin: a thermos

Once outside, Müller shows the passenger around the exterior of the cabin. One side is covered with black paper, the other is shiny metal. In a vacuum, the Sun does not heat space, but it heats the objects it strikes, and black surfaces more than shiny ones. By turning more or less of the black toward it, the temperature can be set at will. Near the Earth, the black side is turned to the Sun. Closer to the Sun, one would do the opposite.

The professor recognizes the principle of the vacuum flask: a shiny wall surrounded by vacuum loses almost no heat. Today’s satellites regulate their temperature in the same way, with light or dark coatings.

A black pipe winds along the shaded side, then along the sunlit side. This is the air distiller. A small pump pushes the cabin air into it. In the shade, it is extremely cold: water vapor and impurities condense there before nitrogen and oxygen do, and stay in the pipe. The purified air then warms up on the sunny side and returns. When the pipe is clogged, it is unscrewed and turned toward the Sun: the deposit evaporates into space.

A telescope without a tube

Under the Luna’s parachute a large concave mirror is stowed. From the cabin, it is moved away on three steel wires wound on drums. It serves as the objective of a telescope whose eyepiece stays on board.

Oberth explains why space is the best of observatories. On Earth, a telescope must be rigid, and therefore massive, because it bends under its own weight. It needs a blackened tube against stray light. It depends on the time of day and on the weather. Above all, the air trembles, and the stars twinkle: beyond a certain magnification, nothing can be made out. The large telescope in Chicago, he notes, is “too strong” for the canals of Mars.

In space, none of this. No weight: three wires are enough to hold the mirror. No diffused light: no tube. No air: the images are sharp. The mirror need not even be in one piece. It can be carried up in sections and assembled by the divers. The novelist Gail had imagined a magnification of ten thousand. Too timid, Oberth replies: he expects a million.

He also answers an astronomer, Plassmann, for whom the atmosphere of Mars would blur the view in any case. No, he says: a sheet of tracing paper laid on a picture leaves it legible, whereas the same sheet held before the eyes hides everything. Air is a hindrance when it is near the observer, not when it is near the object.

Best of all would be to set the instrument up on a small asteroid, Eros for example, which would serve as a base with no air and no noticeable gravity. One could then look into whether the planets are inhabited or habitable, and whether distant stars themselves have planets.

The Hubble Space Telescope was placed in orbit in 1990, a few months after Oberth’s death. Its successor, the James Webb Space Telescope, was launched in 2021 with a mirror in eighteen segments, unfolded in space.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), chapter 19, pp. 417–420 and 449–457. For the modern reference points: NASA (Alexei Leonov’s spacewalk of March 18, 1965; Edward White’s hand-held maneuvering unit, June 3, 1965; the Hubble and James Webb telescopes).

Chapter 16 · The 1929 book A Small Moon

“Space vehicles on the largest scale can be put in orbit around the earth. They then represent a small moon, so to speak.” With these two sentences, Hermann Oberth opens chapter 20 of his book. In it he describes what we call a space station. He gives it a name, observer station, an altitude, a crew, and a list of trades.

Building up there

Such a station does not need to be able to land. It stays up. Small rockets shuttle to and from the Earth and bring it people and equipment. It can therefore be enlarged and rebuilt on the spot, piece by piece, to suit its task. That is exactly how the International Space Station was assembled, between 1998 and 2011.

To live there for long, one needs weight. Oberth takes up his remedy again: two cabins connected by a cable ten to twenty kilometers long, rotating about each other. He justifies that length on psychological grounds. With a short radius, one would have to spin fast to obtain a gravity comparable to the Earth’s, and the passengers would be seasick. So he sets aside, while finding it very beautiful, the proposal of an author who signs himself Noordung: an inhabited wheel with a radius of scarcely a hundred meters. He likewise sets aside the rotating drum Ganswindt had imagined.

Where to put it

Many authors, he notes, want to place the station at the point where the Moon’s attraction offsets the Earth’s. That is a mistake. An object placed there would not stay put: at the slightest deviation, it would be carried off. The position is unstable.

Near the Earth, by contrast, the orbit is stable. Work must be done to move up as well as down. And the disturbances due to other bodies are weaker there and easier to correct. Oberth proposes an altitude of 700 to 1,200 kilometers.

In passing he forestalls a naive question: what keeps the station from falling? Its speed, he answers. Centrifugal force is enough. The Moon does not fall to Earth, although there is no body above it to draw it upward.

What would be done there

The list of uses takes two pages, and today it reads like a satellite catalog.

Observing the Earth. With their instruments, Oberth writes, the occupants could make out every detail on the ground. They could photograph unexplored countries. He cites Tibet.

Communicating. The station would relay light signals from one point of the globe to another, and connect regions the telegraph does not reach or that a breakdown has cut off from the world. Distant expeditions would stay in contact with their homeland.

Aiding navigation and saving lives. The station would see every iceberg and warn ships. The tragedy of the Titanic, in 1912, could have been prevented in this way, he writes. It would find the shipwrecked and lost aviators. He names Nungesser and Coli, who vanished in 1927 trying to cross the Atlantic, and the explorer Roald Amundsen, who vanished in the Arctic in 1928.

Forecasting the weather. He does not consider it impossible to follow by telescope the movement of high and low pressure areas and the direction of the winds. The weather over the whole Earth would then be kept constantly in view.

Informing armies. Oberth does not hide it. The strategic value of such a post is obvious, he says, especially over regions with little cloud, whether the state that owns it is itself at war or sells its reports to the belligerents at a high price.

A filling station

The last use is the most important for anyone who wants to go farther. The station can serve as a fuel depot. In the shade, hydrogen and oxygen keep there for as long as one likes.

A ship leaving from there already has the station’s speed, close to eight kilometers per second. It has no more air to cross and no strong thrust to withstand. It can therefore be built light, in whatever shape one wants. Oberth imagines a large sphere of very thin sheet metal, manufactured on the spot and filled with fuel, which a small, solidly built rocket pushes ahead of it while drawing from it as it goes. On arriving near another body, the small rocket descends alone to the surface. The sphere stays in orbit and waits. On the return, the two join up again.

Forty years later, the Apollo flights applied this division: a small vehicle goes down to the Moon while the main ship waits in orbit with the fuel for the return. And several current plans for the voyage to Mars rely on refueling in Earth orbit, as described here.

Waste

Oberth even thinks about garbage. In a ship, it is thrown out through an airlock. Around a station, it would stay in orbit and become so many small celestial bodies. So the question, he writes, must be taken seriously. His solution: the disposal device gives the objects such an impulse that their trajectory brings them back into the upper atmosphere, where they burn up like meteors. For the people living below, he adds, it would be only a pretty spectacle without further consequences.

Space debris has since become one of the agencies’ major concerns. The rule they impose on satellites at the end of their life is that of 1929: bring them back down so that they burn up.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), chapter 20, pp. 478–481, and p. 449. For the modern reference points: NASA (assembly of the International Space Station, the Apollo program).

Chapter 17 · The 1929 book The Sodium Mirror

Hermann Oberth took a piece of sodium, that soft, silvery metal kept under kerosene because it catches fire on contact with water. He rubbed a piece of wood with it, under kerosene, to see what thickness of metal is enough to make a mirror. That is the experiment he reports in support of the most outsized of his projects: a mirror a hundred kilometers wide, in orbit around the Earth.

A net stretched by rotation

The principle is simple. A large circular net of metal wires turns slowly on itself. The rotation stretches it, as it stretches a twirling skirt. In the meshes are fixed facets of very thin sheet metal, each of which can be oriented by electric currents controlled from the station.

By adjusting the facets, all the reflected light can be concentrated on a single point on the ground, or spread over vast regions, or sent off into space when it is not needed.

The metal chosen is sodium. It is light, it can be rolled, it shines like silver, and in a vacuum nothing attacks it since there is no oxygen. Rockets would carry it up in blocks. Up there, it would be put through a rolling mill to make sheets five thousandths of a millimeter thick. Men in divers’ suits would assemble and polish the pieces. The whole would weigh ten grams per square meter.

Melting the pack ice

What would it be for? Oberth lists the uses. Keeping the sea route to Spitsbergen or to the ports of northern Siberia free of ice. Making vast lands of the Far North habitable by spreading a diffused light over them. Preventing, in our latitudes, the spring and fall frosts that destroy the fruit and vegetable crops of whole provinces. He goes so far as to imagine starting or stopping certain winds by heating a region the night before.

He puts figures on it. One hectare of mirror would cost at most 3,500 marks, transport included, and would make three hectares of polar land arable. A mirror a hundred kilometers in diameter would come to three billion marks at the most. He foresees years of construction, at the rate of a hundred metric tons of sodium carried up every week.

He also corrects a novelist. Otto Willi Gail had described a giant mirror that concentrated light on one hectare. Impossible, Oberth replies: each facet, however small, sends back an image of the Sun that has a minimum size, as in a camera obscura. Seen from a thousand kilometers, that spot is ten kilometers wide. To heat strongly, the mirror must therefore be placed as close to the Earth as possible.

“Unfortunately”

Then comes the paragraph that gave the project its bad reputation. Oberth introduces it with the word “unfortunately.” Such a mirror, he writes, would also have high strategic value. Munitions factories could be blown up, tornadoes and thunderstorms produced, marching troops and their reserves destroyed, whole cities burned. So it is not excluded, he concludes, that a civilized state will carry out this invention in the foreseeable future, the more so since a large part of the invested capital would also bear interest in peacetime.

These lines date from 1929. They are not a weapon plan: Oberth had neither rocket nor station. Yet they say something about him. He saw no objection to war money financing the conquest of space, and he used it as an argument. The following decade would show where that reasoning leads.

The admission

Immediately afterward, he addresses the reader with a candor rare in a scientific work. He could have, he says, kept to the most sober calculations. But to create the respect his idea needed, without which it would never be realized, he felt impelled to draw a few pictures of the future at the end of the book, and he set up some fantastic claims. For all that, he said nothing that might not be possible by the science of the day.

In 1967, he said it again more bluntly: he had put the mirror in the book to offer the reader something sensational.

He then spends twenty pages defending his mirror against every objection. Would the pressure of light push it out of its orbit? He calculates that pressure and shows that it can be used to steer it. Would cosmic dust tarnish it? The facets would be passed through the rollers again from time to time. Would clouds stop the light? Not all of it.

“Only dreams of the future”

He concludes in a tone that is his alone. Enough, he writes, these are only dreams of the future. Bold ones? Perhaps. But we have already seen bolder ideas realized. Who would have believed in 1894 that, a few years later, one would see through a person by means of Röntgen rays? The year 1894 was that of his own birth.

He acknowledges that the project would require enormous energy and enormous sums. But a hundred times more energy and a thousand times more money were spent during the Great War, he says. In a single year, the nations of Europe spend more on smoking and drinking than the whole mirror would cost. War and narcotics are quite unnecessary things, and more money is spent on them than on anything useful. Should not mankind, for once, save something for constructive work?

The sodium mirror was never built. In 1993, Russian engineers deployed in orbit a twenty-meter mirror of aluminized plastic film, stretched by rotation, and for a moment swept a spot of light across Europe. The experiment was called Znamya.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), chapter 20, pp. 481–506; “My Contributions to Astronautics” (1967), in First Steps Toward Space, p. 136. The Russian Znamya 2 experiment (February 4, 1993) is mentioned as a reference point.

Chapter 18 · The 1929 book Landing Like a Snowflake

“The rocket must land as gently as a snowflake.” Hermann Oberth wrote that sentence in 1929, forty years before a crewed craft touched the Moon. He describes the descent: first brake most of the speed, then come down at an almost uniform rate, stop one meter above the ground, and finish “centimeter by centimeter.” The pilots of the Apollo lunar module would do more or less that.

Two questions

Chapter 21 is titled “Trips to Strange Celestial Bodies.” Oberth opens it by admitting that so much is being said on the subject that he feels bound to answer, if only the letters he receives. He asks two questions, and he will ask them for each body. Are these flights possible, there and back? And if so, do they have a purpose?

The tally of speeds

To reach the Moon, a rocket must leave the vicinity of the Earth at 10,380 meters per second at least. It then just gets to the point where the Moon’s attraction outweighs the Earth’s, and the trip takes about ninety-seven hours.

Just is too close, Oberth remarks. At that limiting speed, the rocket arrives almost at a standstill at the point of balance. An error of a few millimeters per second at departure then changes the arrival time by hours. Now the Moon moves about one kilometer per second along its orbit: it covers its own diameter in under an hour. One would miss it. So one must leave a little faster, at 10,500 meters per second. For Fritz Lang’s film, he adds in a footnote, he even chose 10,700.

The rocket then falls toward the Moon and reaches it at about three kilometers per second. Since the Moon has no atmosphere, braking can be done only with the engine. One must leave again at the same speed, then return. Oberth draws up the table, item by item: 11,200 meters per second to leave the Earth, losses included; 3,027 to brake on arrival; 873 lost during the careful descent; 3,030 to leave again; 1,000 in reserve, because the pilot is only a human being and can make blunders. Total: 19,130 meters per second.

With gases ejected at 4,000 meters per second, that requires a rocket 134 times heavier at departure than on arrival. It is enormous, but not impossible: three hydrogen rockets stacked together would be enough. So much for the first question.

Sand and naked rock

What will one land on? Oberth reasons it out. The lunar ground goes from more than one hundred fifty degrees Celsius in sunlight to extreme cold in shadow. Brittle rocks must have shattered there like a glass into which hot water is poured. The horizontal areas are therefore probably covered with fine sand and dust, like the deserts of the Earth. And the rocket’s gases will no doubt blow that sand aside, so that the craft touches down on naked rock.

Both predictions were good. The astronauts of 1969 found a fine dust, and they saw the descent engine drive it off in low, flat sheets.

He also worries about the strength of the craft. Its hull is thin sheet metal that the cold of liquid hydrogen has made brittle. It needs resilient legs, and a very gentle arrival. Hence the snowflake.

Making the fuel on the spot

Oberth then slips in an idea he would take up again for Mars. If the first expedition finds enough water on the Moon, the next one will not have to carry the fuel for the return. In its place it will load a sunlight motor, an apparatus for splitting water into hydrogen and oxygen, a refrigerating machine to liquefy them, and a large insulated tank. This equipment would stay on the spot and serve the following expeditions, which would bring other equipment. Thus, little by little, a station would be built on the Moon.

He adds honestly that he does not believe enough water will be found there. Some astronomers attributed the light patches in a few craters to hoarfrost. He doubts it: if there were water in any notable quantity, the surface would change its appearance far more. We know today that there is ice at the bottom of polar craters that are always in shadow. Plans for a lunar base intend to use it exactly as he describes.

What to go there for

There remains the second question. Oberth rejects the idea that one should visit only bodies where one can live as on Earth. No one can live at the North Pole, he writes, and yet it is explored. Our usual living conditions are not found in mine pits, and thousands of miners go down into them every day, precisely because something else is found there than on the surface. If all technical aids were forbidden, one could not even spend the winter in Europe.

On the Moon, one will protect oneself against the cold of the night by reflecting surfaces, against the lack of air by the diver’s suit, against the heat of the rocks by insulated soles, against the Sun by parasols.

Science would gain a great deal. The Moon is made of the same materials as the Earth, but its surface has undergone neither air nor water. By comparing, one would know what air and water have done to ours. Shafts far deeper than on Earth could be dug there, since everything weighs six times less.

Finally he glimpses a practical interest. According to a then recent theory, the Moon’s craters were dug by meteorites. These bodies contained heavy metals, which stayed on the surface instead of sinking as they did into the still molten Earth. They could therefore be mined, and sent to Earth by an electromagnetic gun, far shorter than the one that would be needed here. The installation would be made easier, he remarks, by the fact that the Earth always stays at the same place in the lunar sky.

Against “cosmic ice”

He uses the chapter to warn his readers against a theory then much in vogue in Germany, the glacial cosmogony of Hörbiger and Fauth, according to which the Moon and the planets are covered with ice. Valier and Gail believed in it. Oberth takes it apart in a paragraph: when the Sun rises over a region of the Moon, the heat radiation it sends back increases, and from this a temperature of 150 to 180 degrees is deduced. At such a temperature there can be no talk of ice. He advises laymen not to read Hörbiger’s book, whose false notions, he says, are just as forceful as its merits.

In the end, he does not think chemical rockets will ever make this trip. He hopes it will be reserved for his electric spaceship. On that point he was wrong: in July 1969, it was indeed a three-stage chemical rocket, two of whose stages burned liquid hydrogen and oxygen, that took men to the Moon. He was present at the launch.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), chapter 21, pp. 507–518. For the modern reference points: NASA (the Apollo program; water ice in the Moon’s polar craters).

Chapter 19 · The 1929 book Mars, Seen from Mediasch

“The space-ship does not need to take along fuel for the return trip; it is sufficient to take along machines for manufacturing the fuel on Mars itself.” The sentence appears on page 546 of the American translation of Hermann Oberth’s book. It dates from 1929. Sixty years later, the engineer Robert Zubrin would make it the heart of his Mars Direct plan. In 2021, a device the size of a car battery, carried on the Perseverance rover, produced oxygen from Martian air for the first time.

The road

Oberth devotes eighteen pages of his chapter on other worlds to Mars. He begins, as always, with the numbers. Mars orbits the Sun one and a half times farther out than the Earth, on a slightly oval orbit. The most economical route is the one Walter Hohmann calculated: a half-ellipse that leaves the Earth’s orbit by grazing it and joins that of Mars in the same way.

He calculates what this route costs. To leave, a propulsion of about 13,300 meters per second is needed. On arrival, the ship meets Mars with a difference in speed of two to three kilometers per second, which must be canceled. Oberth counts first on the planet’s atmosphere. But he knows the air of Mars is thin, and he reserves the last 400 to 700 meters per second for the engine. It is the problem the engineers of the Jet Propulsion Laboratory would face at every landing: too much air to ignore, not enough to rely on.

To leave again, the gravity of Mars must be overcome, far weaker than ours: he gives 4.96 kilometers per second for the escape velocity. The return requires about 6.7 kilometers per second in all, since the Earth’s atmosphere takes care of the final braking. The round trip therefore costs some twenty kilometers per second. That is, he notes, somewhat more than a trip to the Moon. Only somewhat more: the remark still surprises those who come upon it today.

Waiting

The difficulty of Mars is not the expenditure; it is time. The two planets are well placed relative to each other only at long intervals. The cheapest voyage obliges one to wait on Mars, for almost half a Martian year, until the Earth comes back into a good position. Oberth sees at once what this implies for the propellants. Keeping hydrogen and oxygen liquid for a year, he writes, is another matter.

He then considers a fast voyage. With twenty-five kilometers per second, the round trip would take four to six months. But he prefers another solution, the one that opens this chapter.

The factory on Mars

There is very likely water on Mars, he judges, and the sky there is clear. So the raw material and the energy of the Sun are available on the spot. It is enough to bring the machines. The gain is at least six kilometers per second on the voyage’s budget, which greatly reduces the size of the rocket leaving the Earth.

He draws three consequences. The expedition could stay on Mars as long as it wished, since its return fuel is being made while it works. The total duration would be one to two years. And once such a station is established, Mars would become, as regards fuel, the easiest of all bodies to reach.

Oxygen for breathing would be drawn from the Martian air by distillation. Drinking water would be produced on the spot. Provisions, on the other hand, would come from Earth. He gives two reasons: we do not know at all whether Mars is inhabited, and its plants, if there are any, would probably be too laden with salts to nourish human beings.

The Mars he imagines

Here one must separate what Oberth calculates from what he believes. His trajectory calculations remain correct. His planet, however, is that of the astronomers of 1929, and it is largely wrong.

He thinks the air pressure there is about half ours. It is in fact one hundred to two hundred times lower than on Earth. He thinks that air probably contains oxygen. It is made almost entirely of carbon dioxide. He speaks of salt water on the surface and of moist seasons. No liquid water lasts on the ground of Mars.

On other points, his good sense keeps him from error. Human beings, he writes, will probably not be able to breathe the air on Mars. He would already be satisfied if the pressure were great enough to make divers’ suits dispensable, and if it were enough to carry air tanks on the back, tanks which, fortunately, would not weigh much there. He warns that precautions will have to be taken against the cold of the nights.

He explains the red color by hydrated iron oxide, the same that colors the sand of our deserts. That is the right explanation. He rejects the idea, held by the supporters of glacial cosmogony, of a Mars entirely covered with ice: the atmosphere there is too dry, and the map of the planet has not changed in seventy years. And he remembers that what is sometimes taken for mist could well be dust clouds.

The canals, the Martians

In 1929, many readers still believed in the canals of Mars and in their builders. Oberth is clear. The idea that these lines are the work of thinking beings seems to him definitively disproved. They may be an optical illusion. As for the gray or green patches that the astronomer Pickering took for vegetation, the question, he says, is unclarified.

Is there life? He answers with a doctor’s image. Life need not be present wherever it could occur: a sterilized tin can contains everything microbes need, and there are none in it. He does not believe that germs could have traveled from the Earth to Mars through space, as the chemist Arrhenius supposed. He doubts still more a human-like intelligence. If highly advanced Martians existed, he remarks, the planet would look quite different.

His conclusion is one of complete honesty: we can affirm with a good conscience that we can say absolutely nothing about the living world of Mars.

These pages also contain remarks on the evolution of species and of human societies, marked by the ideas of his time, in which he uses the vocabulary of “race hygiene.” They have no scientific value, and they foreshadow aberrations that will be discussed later.

Why go

The only thing that can be promised, Oberth writes, is that the first expedition will settle the old controversies. After it, one will know whether further trips have a purpose. He even ventures this sentence, astonishing in a man who devoted his life to spaceflight: it is possible that the first expedition to Mars will be the last for centuries.

He then amuses himself by financing it. A benefactress, Madame Guzman, bequeathed one hundred thousand francs to the Paris Academy of Sciences, to reward whoever established communication with another planet. If that money had been invested, instead of sleeping in an envelope at the bottom of a safe, it would pay for the expedition, he calculates. And public interest in Mars is such that the slightest object brought back, a flask of air, a little water, a pebble, would fetch a fortune from museums and collectors.

Behind the joke, the program is accurate. Bringing back samples of Martian air and rock is today one of the major goals of the space agencies.

A rule of conduct

The chapter ends with two paragraphs one would gladly quote in full. If Mars is uninhabited, Oberth writes, the first expedition should attempt acclimatization trials there, with terrestrial organisms from similar climates, those of Central and Northern Asia for example. That would open a new domain to life, and much would be learned by watching those organisms adapt.

But if Mars is already inhabited, its natural life would have to be guarded and preserved unchanged. Its study would be epoch-making for the life sciences.

In 1929, in Mediasch, a schoolteacher had just stated the principle that space agencies apply under the name of planetary protection: do not contaminate a world that might harbor life. In the same breath he raised, without resolving it, the question that still divides those who dream of Mars. Should life be brought there, or should the planet be left as it is?

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), chapter 21, section “Mars,” pp. 529–547. For the modern reference points: NASA (the atmosphere of Mars; Perseverance’s MOXIE experiment, first oxygen production on April 20, 2021; planetary protection); R. Zubrin, the Mars Direct plan (1990).

Chapter 20 · The 1929 book Venus, the Electric Wind, and the Last Sentence

Hermann Oberth’s book ends with a ship that burns nothing. A concave mirror concentrates sunlight on a boiler. The steam turns a turbine. The turbine drives an electrical machine. And the electricity drives backward, at tens of kilometers per second, a “wind” of charged particles. It is the last chapter, the twenty-second. It closes on a sentence its author could have taken as his motto.

Venus, “the most rewarding”

Before coming to it, Oberth reviews the other bodies. Venus, he writes, could be the most difficult but also the most rewarding to explore. Its size is almost that of the Earth. Its atmosphere is thicker than ours. Through the telescope, it offers only a uniform white surface on which not the slightest detail can be recognized: a thankless object for the observer, he notes. The dark spots some claim to see there are only a glare effect, and they disappear when the instrument is better.

He ventures an estimate of the temperature. He attributes to the white veil, which he takes for mist, a moderate temperature, and thinks the ground is somewhat warmer. He does not believe the atmosphere contains much carbon dioxide. On both points he is badly wrong: Venus is wrapped in carbon dioxide, and its surface exceeds 450 degrees Celsius. But his reasoning contains the key to the error. If the air of Venus held much carbon dioxide, he writes, the planet could be considerably warmer than his calculation indicates. He named the greenhouse effect, then set it aside.

He also admits what is not known. In 1929 no one knew whether Venus rotates on its axis or always turns the same face to the Sun, as the Italian astronomer Schiaparelli thought. So he studies both cases, and for the second describes winds he puts at hundreds of kilometers per hour.

By stages, each of which pays

How is all this to be financed? Oberth takes up a line of reasoning from the Austrian Guido von Pirquet, whom he quotes at length. Some works are of no use until they are finished: a bridge, a tunnel. Others can be built in pieces, each of which is useful in itself. The rocket belongs to the second kind.

First stage: a meteorological rocket, which lifts instruments to a hundred kilometers and more, and brings them back by parachute. Second stage: a long-distance rocket, to cover hundreds of kilometers. Third stage: a craft capable of circling the Moon. Fourth stage: the crewed ship. Each stage has its own value and pays for itself. It hardly matters, then, if the project halts for a few years along the way.

Oberth doubts that the meteorological rocket would yield revenue. He believes, on the other hand, in the mail rocket. Just think, he writes, what it means: to send letters in the original from Berlin to Moscow in less than half an hour, or from Europe to America. The mail rocket never existed. But the sequence he describes, sounding rocket, missile, lunar probe, crewed flight, is indeed the one history followed, and it was the armies, not the post office, that paid for the second stage.

The electric spaceship

The chemical rocket has a limit. Its gases hardly leave at more than four kilometers per second, because they draw their energy from the fuel itself. To go far, enormous masses of fuel are needed.

So Oberth seeks to separate the energy from the matter ejected. Energy, in space, is free: the Sun supplies it. If it is used to accelerate a very small quantity of matter to a very high speed, ten to forty kilometers per second, the result is a weak thrust, but one that lasts for months and consumes almost nothing. On Earth, he remarks, energy costs more than matter, and one saves on energy. In space, it is the reverse.

He describes the machine in detail: the cylindrical boiler, set spinning so that the water presses against the wall, the turbine, the electrostatic machine, the wire-grid electrodes. He specifies that he does not want to project electrons alone, too light to push, but a wind of gas particles. For this he chooses elements that can be drawn from the rocks of the Moon or the asteroids.

Such a ship cannot take off from a planet: its thrust is too weak. It shuttles between orbits. Small rockets provide the link with the ground. Oberth even imagines a power station in orbit that would send its energy, by a beam, to craft climbing toward it.

The ion engine, which applies this principle, first flew in space in 1964. Today it propels distant probes and many satellites. Oberth devoted a whole book to it in 1963.

“Nothing is impossible”

After the stations exchanging beams of energy, after a cable raised above the atmosphere and traveled by elevators, the author stops. The last sentence of the book takes two lines: “Whether all this will work, I do not know. But nothing is impossible on earth; one must only discover the means with which it can be carried out.”

The whole man is there. He has just covered more than four hundred pages with close calculation, and he concludes that he does not know. He has built nothing, and he asserts that everything can be built. In the months that followed, he was to be given, for the first time in his life, money, a workshop, and a deadline. It would not be a university or a ministry. It would be a film studio.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), pp. 403–406 (economic stages, after G. von Pirquet), 547–556 (Venus), and chapter 22, pp. 557–576. For the modern reference points: NASA (temperature and atmosphere of Venus; SERT-1 ion engine test, July 20, 1964).

Chapter 21 · 1928 – 1929 Woman in the Moon

A photograph taken at the UFA studios, near Berlin, shows a small group in front of a set. There is the set builder, a cameraman, a young actor. There is the director, Fritz Lang. Beside him stands a schoolteacher from Romania, Hermann Oberth. And in the same picture are Hermann Ganswindt, the old forgotten inventor, and Willy Ley, the young popularizer. In 1928, German cinema had decided to go to the Moon, and it had summoned those who knew how.

The filmmaker and the novelist

Fritz Lang was then one of the most famous directors in Germany. He had just made Metropolis. His wife, the novelist Thea von Harbou, wrote his screenplays. Their new project was titled Frau im Mond, woman in the Moon: an expedition leaves by rocket to look for gold on the far side of our satellite.

Lang wanted the rocket to be real, or at least plausible. He met Oberth in July 1928, and Oberth signed a contract with UFA as scientific adviser. Shooting took place at the Neubabelsberg studios from October 1928 to June 1929. Oberth left his school in Mediasch for a time and came to Berlin. It was to those two, Thea von Harbou and Fritz Lang, that he dedicated his major book, which appeared the same year as the film.

What Oberth put into the film

His contribution was specific, and he noted it himself, in the course of the pages of his treatise.

He did the preliminary calculations for the flight. The script required a start in central Germany and a landing on the Moon. He determined the ascent trajectory and the departure speed: 10,700 meters per second, a little more than strictly necessary, to be sure of not missing the Moon.

The ship in the film has several stages. The lower stages are bundles of small rockets, light enough for each to come down on its own parachute. He had steering fins added in the engine’s jet: it is the system that would be found on real rockets, where vanes immersed in the gases orient the craft. The film also shows the Earth as it would be seen from the ship, with its size and its position among the stars. Oberth reproduced three of these images in his book, to show how a pilot knows at a glance whether he is on the right course.

The audiences of 1929 thus saw on the screen what the Luna story told: a giant multistage rocket, a crew lying down to bear the acceleration, passengers floating, held by straps. The ship in the film starts from a basin filled with water, as the one in the story started from the sea.

One scene has remained. To build tension before the launch, Lang runs numbers across the screen, in descending order, down to zero. The invention of the countdown is commonly credited to this film.

The rocket for the premiere

The production had another idea, a publicity one: to launch a real rocket on the day of the premiere. Oberth received money to build it. For a man who had been asking for years for the means to experiment, the offer could not be refused. In the book he was finishing, he had just written that he would need less than ten thousand marks for the preliminary tests.

He had a few months. He had never built an engine. He surrounded himself with two assistants. The first was Alexander Scherschevsky, the Russian student who had read his proofs. The second was Rudolf Nebel, a former wartime aviator. A launch rack was built for the rocket at Horst, on the Baltic coast.

The rocket would not fly. The next chapter tells why.

October 15, 1929

The premiere took place on October 15, 1929, at the Ufa-Palast am Zoo, a large Berlin theater. No rocket rose that evening. According to the historian Uwe W. Jack, Oberth was not in the audience. The film was silent, at a time when talking pictures were taking over.

Its influence lay elsewhere. It showed a wide public a multistage rocket piloted by human beings. It circulated among the young enthusiasts who would surround Wernher von Braun. In June 1931, the film was shown in Boston. Robert Goddard was invited to the premiere. He did not go.

Oberth, for his part, had obtained what he had decided to seek at Heidelberg seven years earlier: the public. He still had to face what he had not foreseen, the workshop.

Sources: H. Oberth, Ways to Spaceflight (1929, NASA trans. 1972), dedication and pp. 250, 266, 282–283, 406, 509, and 524; “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 137–139 (photographs of the filming, Willy Ley and F. I. Ordway collections); I. Sänger-Bredt and R. Engel, same volume, pp. 224–226; The Papers of Robert H. Goddard, vol. II (invitation of June 3, 1931). U. W. Jack, biography of Oberth (raketenflugplatz-berlin.de); shooting and premiere dates: film records (UFA, 1929).

Chapter 22 · Fall 1929 The Explosion

In the fall of 1929, on the grounds of the UFA studios, a test went wrong. Gasoline and liquid oxygen met in a narrow space and detonated. Hermann Oberth came out of it alive. He would say later that the explosion almost shattered his nerves. It also taught him, in a fraction of a second, the one thing he still did not know about combustion in a rocket engine.

A theorist in a workshop

Oberth had a few months to build a rocket able to fly before the press. He had no engine. He had never worked with liquefied gases: in Transylvania, he could not obtain them. His calculations told him what the machine must do. They did not tell him how to drill an injector, weld a tank, or regulate a feed of oxygen at minus one hundred eighty-three degrees Celsius.

He acknowledged it in 1967 with disarming candor. The affair, he said, was nevertheless disgraceful. First, he was not a trained mechanic. Henry Ford was right when he said that one should not invent an engine one could not assemble with one’s own hands. “Let me tell you, that man was right.”

The sources do not allow the detail of those weeks to be reconstructed. We know from Willy Ley that a launch rack was built for the rocket at Horst, on the Baltic. We know from a letter of Robert Goddard’s that two tests failed and that the studio stopped paying. And we know from Rudolf Nebel that the supposedly fireproof linings fitted to the chambers burned up one after another.

What the explosion showed

Until then, one question had troubled Oberth secretly. It was, he said, the only question of physics left to him. In a rocket chamber, the liquids have only an instant to burn before they are driven out through the nozzle. Would they burn fast enough? If they burned only halfway, his whole theory would stay on paper.

The accident brought him the answer. It proved to him that gasoline and liquid oxygen can burn, in a narrow space, much faster than he had thought. And he understood why. A burning drop of fuel is not consumed tidily from the outside in. It tears itself into finer droplets, which tear themselves apart in turn. The surface offered to the flame multiplies, and combustion races. This is what he calls the atomization of burning droplets.

The practical consequence was immediate. If the drops divide of their own accord, everything can burn in a very short chamber. He at once designed a new injector.

Three weeks

A man with steady nerves, Oberth says, would have stopped everything to recover. He did not want to give up the exceptional opportunity he had been given to experiment. He went on. Fourteen days after the explosion, he had his slit injector and his nozzle. Seven days later, his cone-shaped chamber was ready to fire.

Historians of the rocket engine have found the trace of these two steps. The first is the Spaltdüse, the slot nozzle, which gave two and a half kilograms of thrust. The second is the Kegeldüse, the cone nozzle: a small cone-shaped chamber. Oberth had the arrangement patented in Germany.

With that, he says, the door to space travel was pushed open. The phrase is a little strong for so small an engine. But he would receive for it the certificate of the first firing, in Europe, of a gasoline and liquid-oxygen engine, and the first rockets of the Berlin group would descend from it.

The “blunders”

Yet something is missing from the account, and Oberth says so himself. Under the effect of tension and taut nerves, he committed, he admits, several grave blunders, especially in his treatment of people. He says no more. He names no one.

One can only note the facts. On October 3, 1929, Oberth was still asking the ministry for permission to make a test launch on the Baltic coast between the 10th and the 20th of the month. The rocket was not ready on October 15. The studio withdrew. At the end of December, Oberth left for Mediasch. Nebel, for his part, carried on: the Horst launch rack would be reused as raw material for the big test stand of the young men of Berlin.

In the fall of 1929, Oberth was thirty-five. He had just discovered what Robert Goddard, on the other side of the Atlantic, had been facing since 1921: the distance between a correct calculation and a machine that works. He drew from it a lesson in modesty and a small cone-shaped chamber. He still had to prove, before someone official, that it worked.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, pp. 139–140 and notes 21–23; U. W. Jack, biography of Oberth (raketenflugplatz-berlin.de); I. Sänger-Bredt and R. Engel, same volume, pp. 221 and 224 (after W. Ley and R. Nebel, Raketenflug, 1932); letter from R. H. Goddard to W. Kaempffert, April 18, 1930, The Papers of Robert H. Goddard, vol. II.

Chapter 23 · July 23, 1930 Seven Kilograms of Thrust

On July 23, 1930, at Berlin-Plötzensee, on the grounds of the Government Institute for Chemistry and Technology, a small cone-shaped engine was fixed to a makeshift rack. The institute’s director, Dr. Ritter, looked on. Hermann Oberth had come back from Mediasch for this demonstration. Around him four assistants were busy: Rudolf Nebel, Klaus Riedel, Rolf Engel, and an eighteen-year-old who had just received his school-leaving diploma, Wernher von Braun. The gasoline was opened, the liquid oxygen was opened, the engine was lit.

Ninety-six seconds

The engine burned for ninety-six seconds in all. It reached a maximum thrust of about 7.7 kilograms. For 50.8 seconds, it held a nearly constant thrust of seven kilograms.

These figures are tiny. Seven kilograms is the weight of a large cat. But they were measured and certified by an official body, whose role is comparable to that of a national bureau of standards. And they proved three things: liquid oxygen and gasoline can be brought into a chamber, burned there steadily for nearly a minute, and made to yield a stable thrust.

The engine held because it was spared. It had no cooling circuit: its wall simply absorbed the heat. To keep it from melting, it was fed far more oxygen than is needed to burn the gasoline, nearly twice the ideal proportion. The flame is cooler, the efficiency poorer. Cooling by the fuel, which Oberth had described as early as 1923, would have to wait.

Dr. Ritter recommended that this work be supported by the body that then financed German research. Oberth received a certificate: that of the first firing, in Europe, of a gasoline and liquid-oxygen rocket engine.

The photograph

A photograph, dated August 5, 1930, by the Smithsonian and July 23 by the historian Uwe W. Jack, shows the group on the same grounds. From left to right one sees Rudolf Nebel, Dr. Ritter, a Mr. Bermüller, Kurt Heinisch, then Oberth half hiding an unidentified man, then Klaus Riedel in a white coat, and Wernher von Braun. Two or three other faces have no name.

The picture became famous because of the youngest. The eighteen-year-old graduate would be, thirty-nine years later, the man who sent Americans to the Moon. Oberth said it simply in 1967: he had been helped by students of the Technical University of Berlin, and among them was Wernher von Braun, who has since made space travel a reality.

The master leaves

That summer was also one of mourning. On May 17, 1930, Max Valier had been killed in Berlin by the explosion of a liquid-propellant engine he was testing. In May, the Society for Space Travel, which had moved its activities to Berlin, had exhibited its rockets on the Potsdamer Platz and then in a department store. Oberth was its president in 1929 and 1930.

But he did not stay. His teaching post was in Romania. In September 1930, according to an American reference entry, he had resumed teaching in Mediasch.

That same month, on September 27, Rudolf Nebel obtained from the city of Berlin, for a token rent of ten marks a year, a former munitions depot in Reinickendorf. He christened it the Raketenflugplatz, the rocket airfield. Willy Ley left an amused description of it: concrete barracks with thick walls, a guardhouse cluttered with rotted lumber that took a full day to clear, and where Nebel and Riedel set up their bachelor household.

The heirs

It was there, without Oberth, that everything continued. Nebel’s first rocket, the Mirak, took over the cone nozzle. It pushed barely more than its own weight, then exploded. So did the second. In the spring of 1931, someone, probably Riedel, had the idea of giving up iron and linings for a chamber of light metal, cooled by a liquid. On May 14, 1931, a small rocket rose to sixty meters. A few months later, others reached a kilometer and a half.

During the winter of 1931, Riedel thought of replacing gasoline with a mixture of alcohol and water, as Oberth had proposed, to lower the chamber temperature. It was that mixture which, ten years later, would feed the army’s big rocket.

For the army was watching. On October 1, 1932, Wernher von Braun entered the service of Army Ordnance, under the direction of Walter Dornberger. In 1934, the Raketenflugplatz was closed. The amateurs were dispersed. The German rocket had become a military secret.

The teacher from Mediasch was not part of it. He was a Romanian citizen.

Sources: I. Sänger-Bredt and R. Engel, “The Development of Regeneratively Cooled Liquid Rocket Engines in Austria and Germany, 1926–42,” in First Steps Toward Space, pp. 217–225 (W. Ley’s chronology, 1932; R. Nebel, Raketenflug, 1932); H. Oberth, “My Contributions to Astronautics” (1967), same volume, pp. 139–140 (photograph of August 5, 1930, F. I. Ordway collection); U. W. Jack, biography of Oberth (raketenflugplatz-berlin.de); New Mexico Museum of Space History, entry “Hermann J. Oberth.”

Chapter 24 · 1930 – 1938 The Locksmith of Mediasch

In 1932, a teacher nearing forty, winner of an international prize, author of the book from which Europe’s rocket builders had learned their trade, sat for a workman’s examination. Hermann Oberth earned his certificate as a locksmith and mechanic. He had taken the lesson of Berlin to heart: one should not invent an engine one cannot put together with one’s own hands.

Back at school

Mediasch is a small town in Transylvania, on the Târnava River. There Oberth returned to his class at the Stephan Ludwig Roth secondary school, to his wife Mathilde, and to their four children. The youngest, Adolf, had been born in 1928.

With his certificate in hand, he added the teaching of practical engineering to his mathematics and physics courses. Later, he says, he also learned design engineering. He was equipping himself, ten years late, for the trade he had invented on paper.

He went on writing. In 1930 a book of quite another kind appeared, Forschung und Jenseits, research and the beyond. His taste for the questions the science of his day left aside therefore did not date from his old age.

The king and the rocket

Romania took an interest in him. An American reference entry states that in 1931 he obtained a Romanian patent for a liquid-propellant rocket. According to the historian Uwe W. Jack, King Carol II received him in audience at the end of April 1932 and asked the military flying school to help him. Oberth then designed a high-altitude rocket. He also worked on a radio-guided powder rocket whose fuel was based on ammonium nitrate.

A German reference entry adds that around this time he declined offers from Moscow and from the king of Bulgaria. We know no more, and none of these leads left a known rocket.

What was happening without him

While he taught, history was moving elsewhere, and fast.

In Berlin, the young men of the Raketenflugplatz flew their small rockets until 1933. The German army, which the Treaty of Versailles forbade heavy artillery but not rockets, recruited the best of them. Wernher von Braun, the eighteen-year-old assistant, defended a thesis in 1934 that was kept secret and soon, at twenty-five, headed the design office of an immense test center built at Peenemünde, on the Baltic. After the Nazis came to power, in January 1933, German publications on rockets ceased. Robert Goddard noticed it from New Mexico: since National Socialism, he wrote in 1940, nothing more has appeared, and it would not be reasonable to believe Germany has given up.

At Peenemünde, engines of twenty-five tons of thrust were being built. They burned alcohol diluted with water, together with liquid oxygen. The chamber was cooled by the fuel, and in 1938 the veil of liquid along the wall was rediscovered there. These were, one by one, the solutions of the 1923 book. The historians Irene Sänger-Bredt and Rolf Engel would write it plainly: the technology of the big German rocket included all the essential details of Oberth’s suggestions for the first stage of his Models B and E.

The author of those suggestions was not invited. He was a foreigner. A Romanian citizen could not be admitted into a secret armament program of the Reich.

A milieu

A word must be said about the world he lived in. The Transylvanian Saxons had been, since 1918, a German minority in a Romanian state. The museum that bears Oberth’s name, in Feucht, has examined what can be known of his commitments at that time. It concludes that no verified source attests membership in a party. It considers it probable that he belonged to the Selbsthilfe, a savings cooperative founded in 1922 or 1923, which after 1930 became a political movement won over to National Socialist ideas. No political activity on his part is documented for those years.

What he himself said, later, of his hopes at that time will be quoted in its place. It is enough to note here that as early as 1917, it was to a Ministry of Armament that he had proposed his rocket.

The contract

In December 1937, Oberth signed a contract with the Deutsche Versuchsanstalt für Luftfahrt, the German aeronautical research institute, which came under the Air Ministry. He was offered what he had been waiting for since 1923: a research post and a test site. In 1938, he left the Mediasch school for the Technical University of Vienna. Austria had just been annexed by Germany.

Sources: H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, p. 139; I. Sänger-Bredt and R. Engel, same volume, pp. 221–228; U. W. Jack, biography of Oberth (raketenflugplatz-berlin.de); Hermann-Oberth-Raumfahrt-Museum (Feucht), “FAQ zur Person Oberth” (as of June 30, 2023); New Mexico Museum of Space History; Kulturstiftung der deutschen Vertriebenen; letter from R. H. Goddard to W. Atwood, July 10, 1940, The Papers of Robert H. Goddard, vol. III.

Chapter 25 · 1938 – 1945 Under the Name of Fritz Hann

In the summer of 1941, a new employee arrived at the army’s test center at Peenemünde, on the island of Usedom. His papers bore the name Friedrich Hann. It was an alias. The man’s name was Hermann Oberth. He was forty-seven. The center’s technical director, who was twenty-nine, had been his assistant in Berlin. The newcomer was given patents to read.

Vienna and Felixdorf

The three preceding years had been disappointing. In Vienna, where he arrived in 1938, Oberth worked for German aviation. His tests took place on the military grounds at Felixdorf, south of the city. An American reference entry sums up the result: for lack of adequate facilities and staff, he could accomplish nothing significant.

The Oberth museum in Feucht specifies the reason for his being kept aside. Oberth was still a Romanian citizen, and that was enough to close Peenemünde to him, where the real rocket was being built. In July 1940, he was transferred to the Technical University of Dresden, to study a propellant pump. That same year, he and his family took German nationality.

Reading patents

At Peenemünde, he was finally let in. But the A-4 rocket, the one propaganda would call the V-2, had already been designed. A large team was working on it under Wernher von Braun’s direction. No one needed one more theorist. The Feucht museum says it clearly: a mathematician and physicist, not an engineer, Oberth took no part in designing the V-2.

His task was to examine patents and technical documents, to spot what might be of use. He also wrote studies. The most important dates from 1941 and is titled Über die beste Teilung von Stufenaggregaten, on the best division of multistage rockets. It is the secret memorandum he spoke of in 1967: in it he finally put in writing the calculation he had kept to himself in 1923, the one that says how to share the mass among the stages to go as fast as possible. Another report proposes defending the German sky against bombers with large remote-controlled powder rockets.

On October 3, 1942, an A-4 flew successfully for the first time and climbed to the threshold of space. The first of the four statements of 1923 was verified: a machine had risen higher than the atmosphere. Oberth had no direct part in that launch.

According to the German reference entries, he criticized the program. He considered the V-2 too complicated and too costly for its military effect. In 1943, he was employed for a time at the supersonic wind tunnel. In December, he obtained a transfer to WASAG, an explosives company located at Reinsdorf, near Wittenberg, to work there on the powder antiaircraft rocket he had recommended.

What the V-2 was

It must be recalled what the weapon was to which his name remains attached, even from a distance. From September 1944 on, more than three thousand V-2s were fired at London, Antwerp, and other cities, and killed thousands of civilians there. They were assembled in an underground factory in the Harz by prisoners of the Dora concentration camp, a very great number of whom died of exhaustion, hunger, and ill-treatment. The machine that opened the road to space came out of that.

Oberth neither directed that program nor designed that rocket. But he had supplied its theory, he had proposed a long-range rocket to a war ministry as early as 1917, and he came of his own free will, in 1938, to work for the aviation of the Third Reich.

Julius and Ilse

The war took two of his four children. His eldest son, Julius, a soldier, was reported missing in 1943.

His daughter Ilse was twenty. She was a rocket technician. She worked in Upper Austria, at Redl-Zipf, on a stand where V-2 engines were tested. That stand, code-named “Schlier,” was set up in a subcamp of the Mauthausen concentration camp. On August 28, 1944, just after a test, an explosion wrecked it. It killed twenty-seven people. Ilse Oberth was among them.

A manuscript of thirteen hundred pages, which Oberth had devoted to spaceflight, disappeared in the disorder of the war.

Moosburg

In April 1945, the Red Army was approaching Wittenberg. Oberth left Reinsdorf and headed south. He reached Moosburg, in Bavaria, where the Americans arrested him. He was interned for a few months. In August 1945, he was released. The denazification procedure classified him as “not affected”: he had never been a member of the Nazi Party or of any of its organizations.

He rejoined his family in Feucht, a market town southeast of Nuremberg, where it had settled in 1943 in an old residence, the Pfinzing castle. He was fifty-one.

At the same moment, Wernher von Braun and more than a hundred Peenemünde engineers, who had surrendered to the Americans, were leaving for the United States. The Soviets took other specialists. No one came looking for Hermann Oberth. He had not built the V-2, and it was the V-2 the victors wanted.

Sources: Hermann-Oberth-Raumfahrt-Museum (Feucht), “FAQ zur Person Oberth” (as of June 30, 2023); U. W. Jack, biography of Oberth (raketenflugplatz-berlin.de); Austria-Forum, entry “Oberth, Hermann”; entries of the New Mexico Museum of Space History, Encyclopedia.com, and the Kulturstiftung der deutschen Vertriebenen; H. Oberth, “My Contributions to Astronautics” (1967), p. 133; I. Sänger-Bredt and R. Engel, in First Steps Toward Space, p. 228; for Ilse Oberth and Redl-Zipf, the German and English Wikipedia entries (to be confirmed from archival sources); for the V-2 and the Dora camp, Smithsonian National Air and Space Museum and the Mittelbau-Dora Memorial.

Chapter 26 · 1945 – 1955 The Gardener of Feucht

In July 1948, a fifty-four-year-old man crossed the Swiss border without a visa. He was in financial need. In ruined Germany, he had earned his living as a gardener. Three years earlier, the victors had divided his pupils among themselves. He was looking for an employer. His name was Hermann Oberth, and learned societies in Paris, London, and Stuttgart were in the process of making him an honorary member.

Honored and unemployed

The contrast was complete. On one side, recognition. As early as 1946, according to the list of his distinctions, he was made an honorary member of an astronautics section in Paris. In 1948, the Society for Space Research in Stuttgart made him its honorary president. In 1949, the British Interplanetary Society in London and societies in Denmark and the United States added his name in turn. In 1950, a medal bearing his name was created.

On the other side, nothing. Occupied Germany was no longer allowed to build rockets. The Peenemünde engineers were in Texas or in the Soviet Union. Oberth, whom no one had recruited, lived in Feucht with his family. According to the historian Uwe W. Jack, he worked for a time as a gardener.

Switzerland

It was need, according to the German reference entries, that drove him to cross into Switzerland in the summer of 1948. There he obtained two contracts from the Confederation’s military technical service, in Bern, to study powder antiaircraft rockets. He then wrote for the aviation journal Interavia and advised a private company.

His situation remained precarious. He was only tolerated. The Swiss authorities themselves helped him look for a position elsewhere, in Argentina, Brazil, Spain. Nothing came of it.

La Spezia

In October 1950, he left for Italy. The Italian navy engaged him at La Spezia to develop a powder antiaircraft rocket, the very one he had been proposing in Germany in 1943. His son Adolf, now a chemist, helped him compose the powder mixtures. Adolf Oberth would later make his career in California, with a major American maker of rocket engines.

The project was abandoned in 1953. Oberth returned to Feucht. He was fifty-nine.

Men in space

He still had his pen. In 1954, Menschen im Weltraum, men in space, appeared in Düsseldorf, subtitled “new projects for rockets and space travel.” In it he took up again, a quarter century later, the great ideas of 1929: the station, the telescope, the space suit, the electric spaceship. He enlarged his space mirror still further, which now reached one hundred to three hundred kilometers in diameter, and imagined making its materials on the Moon.

He also took an interest in energy on Earth. As early as 1947, he designed installations to produce energy and water in deserts. In 1953, he proposed a solar power plant to irrigate arid land and desalinate seawater. It was the beginning of a concern that would never leave him.

In that same year, 1954, the German Inventors’ Association awarded him its Diesel Medal in gold, in Nuremberg.

Another reading of the sky

The year 1954 also saw the appearance, in a mass-circulation American Sunday supplement, The American Weekly, of an article under his name. On October 24, he stated there that flying saucers are real and that they are spaceships from another solar system.

The sentence is surprising from the man who wrote in 1929 that absolutely nothing can be said about the living world of Mars, and who doubted that an intelligence like ours exists elsewhere. It would often be quoted, and often held against him. He would often return to the subject.

The letter from America

In 1955, everything changed. Wernher von Braun was directing, in Alabama, for the U.S. Army, the development of large rockets. He had his former teacher invited. In May, according to Uwe W. Jack, the call reached Feucht.

At sixty-one, Hermann Oberth left for the United States. He was going to work, for the first time in his life, in a center where the machines he had described were actually being built.

Sources: U. W. Jack, biography of Oberth (raketenflugplatz-berlin.de); entries of the Kulturstiftung der deutschen Vertriebenen, Encyclopedia.com, and the Austria-Forum; for Switzerland, The American Weekly, the list of distinctions, and Adolf Oberth: the German and English Wikipedia entries (tertiary sources, to be confirmed); H. Oberth, Menschen im Weltraum (Düsseldorf, 1954).

Chapter 27 · 1955 – 1962 Huntsville and San Diego

“7 July 1955: Professor Hermann Oberth, an internationally known authority on space-flight rocketry, arrived for duty at Redstone Arsenal.” The sentence appears in the U.S. Army’s official chronology. Redstone Arsenal is in Huntsville, Alabama. It was there that the rocket was being built that would put the first United States satellite into orbit. The head of development was named Wernher von Braun.

The pupil turned boss

The roles had been reversed for good. In 1930, in Berlin, a recent school graduate assisted a famous professor. In 1955, the graduate directed thousands of people, and the professor was his employee. It was at his request that Oberth had been hired.

Oberth was assigned to the Technical Feasibility Studies Office of the Army’s Ordnance Missile Laboratories. In 1956, the Army created the Army Ballistic Missile Agency. He moved there, to the Research Projects Office headed by Ernst Stuhlinger, another Peenemünde veteran, a physicist and specialist in electric propulsion. There Oberth was in charge of “special fields.”

He was asked for what he could do better than anyone: look far ahead. He took part in a study on the development of space technology over the next ten years.

Three decisive years

He arrived at the right moment to see, from the inside, the world tip over. The Redstone chronology gives the stages.

On September 20, 1956, a Jupiter-C rocket reached such a speed that it could have put its last stage into orbit, had that been authorized. On August 8, 1957, another Jupiter-C brought back an intact nose cone from space, the first ever recovered. On October 4, 1957, the Soviet Union launched Sputnik. On November 8, the Secretary of Defense ordered the agency to prepare a satellite launch. On January 31, 1958, a Jupiter-C placed Explorer 1, the first American satellite, in orbit.

The second of the four statements of 1923 was verified in its turn: a machine had reached such a speed that it no longer falls back. Thirty-five years had passed since the Munich booklet. Its author was on the premises.

The return

He did not stay. As early as May 8, 1957, the Army announced that Professor Oberth planned to return to Germany later that year. According to the New Mexico Museum of Space History, he resigned in November 1958 and went back to Feucht.

The sources consulted for this book do not give his reasons. He was sixty-four.

The moon car

He then published a small book, translated in New York in 1959 by his old popularizer Willy Ley, who had emigrated to the United States: Das Mondauto, The Moon Car.

The machine he describes in it looks like nothing else. It is a sort of tower mounted on a single leg, itself set on a tracked chassis. The crew cabin is at the top, surmounted by a large gyroscope that keeps the whole upright and by a solar power plant that supplies the current. The vehicle drives. And when it meets a crevasse or a crater wall, it jumps: its leg is a gas cylinder that throws it into the air, to more than a hundred meters high by his calculations, which the low lunar gravity allows.

“My moon car can be built, of that I am sure,” he writes. No one built it. The vehicles that traveled over the Moon from 1970 on had wheels and did not jump. But one finds in it the constant trait of his mind: start from the real conditions of the place, here a gravity six times weaker and ground cut up with holes, and design the machine that takes advantage of them instead of suffering them.

Convair

He crossed the Atlantic one last time to work. In November 1961, the Convair company, in San Diego, California, engaged him for nine months as a consulting engineer. Convair built the Atlas, the first American intercontinental missile, which was also used to launch the first American astronauts into orbit.

The Atlas has a peculiarity every engineer knows. Its tanks are so thin that they cannot stand up by themselves. They keep their shape only when inflated by a slight pressure, like a balloon. That idea, applied by the engineer Karel Bossart, Oberth had proposed in his 1923 book. He recalled it in 1967.

In 1962, at sixty-eight, he retired. He had twenty-seven years left to live, and he would spend them on something quite other than rockets.

Sources: U.S. Army, Redstone Arsenal Historical Information, “Significant Dates in Redstone Arsenal’s Space History” (entries for July 7, 1955; May 8, 1957; and 1956–1958); New Mexico Museum of Space History, entry “Hermann J. Oberth”; U. W. Jack, biography of Oberth; H. Oberth, The Moon Car, translated by W. Ley (New York, Harper, 1959); “My Contributions to Astronautics” (1967), p. 134 and notes 9 and 10; description of the moon car after the German Wikipedia entry.

Chapter 28 · 1962 – 1987 The Shadows

In 1962, the Federation of Expellees, which brings together the Germans driven out of Eastern Europe after the war, made Hermann Oberth an honorary member. He gave his thanks. According to the German Wikipedia entry devoted to him, he then spoke this sentence: “I had hoped to find a rocket weapon that could have smashed the shameful Treaty of Versailles. I did not succeed.” An honest biography cannot pass over this side in silence.

The party

In 1965, at seventy-one, Oberth joined the National Democratic Party of Germany, the NPD, founded the year before. It is a far-right party, in which former Nazis were to be found. That same year he published a pamphlet whose title states its purpose: The Courage of Truth — My Path to the NPD.

He left the party in 1967. The museum that bears his name in Feucht has summarized what is known. He left, the museum writes, because the party was radicalizing and he realized he was being used as a figurehead. The criticism of his contemporaries was sharp, and he drew the consequences.

The matter does not end there. The museum states that the NPD and neighboring organizations went on, after 1967 and even after his death, invoking his name, and that his family tried several times to oppose this in court.

Other ties

The German reference entries note other facts, which must be cited with their limits. Oberth signed a declaration by a far-right grouping that called for a general amnesty for Nazi war criminals. He was an honorary member of a cultural association of the same persuasion, which awarded him a prize in 1987. In 1981, in Passau, he received a “European Freedom Prize,” endowed with ten thousand marks, from the hands of Gerhard Frey, head of another far-right party, the Deutsche Volksunion.

At his death, an aid organization for former Nazis, the Stille Hilfe, presented him as a loyal supporter and donor. The Feucht museum checked. It found trace of only a few small donations, of ten or twenty marks, and considers the phrase greatly exaggerated.

The same museum recalls two facts that point the other way. Oberth was never a member of the Nazi Party or of any of its organizations. And the denazification procedure of 1945 classified him among those not affected.

What he wrote

His books of those years no longer speak of rockets. In 1959 came Stoff und Leben, matter and life, reflections on the modern picture of the world. In 1966, a Catechism of the Uranides asks whether our religions have a future. In 1976, Kakokratie denounces what he calls, with a word drawn from Greek, the rule of the worst, which he holds to be “world enemy number one.” In 1983, he wrote a voter’s primer for a world parliament.

He set himself the aim, in his own words, of working so that the world may become better, more just, and more beautiful. He names three dangers for humanity: ignorance, especially in politics; incitement to hatred; and this “kakocracy.” One recognizes the man of the 1927 quarrels, convinced that the mediocre push aside the best. These reflections led him, for a time, into the company of people who had put that kind of idea in the service of the worst.

It will be remembered that the 1929 book already contained, in the course of the chapter on Mars, pages of ideology in which “race hygiene” and the name of Oswald Spengler appear. The slope was an old one.

The saucers

The other aberration is less serious and stranger. From his 1954 article on, Oberth maintained publicly that unidentified flying objects are ships of extraterrestrial origin. He called their occupants the “Uranides.” He published in a specialized review a text titled “They Come from Outer Space.” In 1967, in Mainz, he took part in a congress of a German society for the study of UFOs.

In September 1967, in Belgrade, before the International Astronautical Congress, he mixed this cause into the account of his life. After recalling the errors of Councillor Lorenz, he ranked among the victims of the same blindness a pastor who believed he had rediscovered Atlantis, researchers in parapsychology, and those who study UFOs.

The reasoning is faulty, and his own life shows it. What finally proved him right against Lorenz was not his protests. It was calculations anyone could redo, an engine measured on the stand in 1930, a rocket in 1942, a satellite in 1958. None of the causes he defended in 1967 has ever produced proof of that kind. Having been wrongly rejected is not enough to be right.

Holding both

The writer Rolf Hochhuth drew from this life a tragedy, Hitler’s Dr. Faust, about the scientist who wanted the Moon and served the war. The title is too strong for a man who did not design the V-2. But the question it asks is the right one.

The Feucht museum has chosen, for its part, to publish what it knows, including what is uncomfortable, and to date the state of its knowledge. That is also the choice of this book. The man who wrote, in 1929, that the life of Mars would have to be guarded and preserved unchanged is the same man who joined, in 1965, a far-right party. One must neither erase the second sentence to keep the first, nor throw away the first because of the second.

Sources: Hermann-Oberth-Raumfahrt-Museum (Feucht), “FAQ zur Person Oberth” (state of knowledge as of June 30, 2023); German and English Wikipedia entries “Hermann Oberth” (1962 speech, list of writings and distinctions, 1981 prize, Mainz congress: tertiary sources, to be confirmed); H. Oberth, “My Contributions to Astronautics” (1967), in First Steps Toward Space, p. 138; Ways to Spaceflight (1929, NASA trans. 1972), pp. 537–544.

Chapter 29 · 1969 – 1989 The Witness

On July 16, 1969, at Cape Kennedy, Florida, a rocket one hundred ten meters tall left the ground. It carried three men toward the Moon. It had three stages. The last two burned liquid hydrogen and oxygen. Among the guests of honor was a seventy-five-year-old man who had described this machine in 1923, in a booklet the university had not wanted. Hermann Oberth watched Apollo 11 leave.

Sixty-four years after Jules Verne

He was eleven when he redid the calculations of From the Earth to the Moon and concluded that the cannon would kill its passengers. Verne had placed his cannon in Florida. It was from Florida that the rocket rose, slowly at first, accelerating for long minutes, as he had understood it must.

The third statement of 1923 had been verified since 1961: human beings can ride in these machines without danger to their health. That day, all the rest came true: the liquid-propellant rocket, stages, hydrogen, braking by engine above an airless surface, the small craft that goes down while the ship waits in orbit, the diver’s suit with its air supply on the back.

The man directing the construction of the rocket was Wernher von Braun, the school graduate of 1930. Oberth had written it two years earlier: among the students who had helped him in Berlin was the one who has since made space travel a reality.

The Feucht museum

Honors had accumulated. In 1961, the Federal Republic awarded him a high distinction of its Order of Merit. In 1963, the German Rocket Society took his name: it was henceforth called the Hermann-Oberth-Gesellschaft. That same year, the Technical University of Berlin made him an honorary doctor. Forty-one years after Heidelberg’s refusal, he finally had his German doctorate.

In 1971, the society bearing his name opened a museum of astronautics in Feucht. A model of the 1930 cone nozzle is shown there. It is one of the first museums in Europe devoted to space.

Romania remembered him too. In 1972, the University of Cluj, the one that in 1923 had accepted the work refused in Germany, made him an honorary doctor. In 1974, for his eightieth birthday, the Romanian state decorated him. In Mediasch, a school bears his name.

In 1982, the Academy of Sciences of the Soviet Union awarded him the Tsiolkovsky Medal. The name of the Kaluga schoolteacher, whose book he had received in 1925, came back to him in the form of a distinction. Of the three men who had found alone, before 1914, the laws of spaceflight, he was the only one to have seen human beings go into space. Tsiolkovsky died in 1935, Goddard in 1945.

The kite and the mirror

He went on inventing. After the oil shock of 1973, he returned to the question of energy. In 1977, he published Das Drachenkraftwerk, the kite power plant: the idea of going to find the wind where it is strongest and steadiest, very high in the atmosphere. In 1978, he took up one last time, under the title Der Weltraumspiegel, the space mirror project of his youth. In it he estimated that it could be realized between 2018 and 2038. And he asked that it serve only peace.

Between 1979 and 1984, his correspondence appeared in Bucharest, in two volumes.

One last launch

On October 30, 1985, he was ninety-one. He attended the liftoff of the space shuttle Challenger. The mission carried a European laboratory, and its scientific program was directed from Germany. On board, among others, was the German physicist Ernst Messerschmid, whose flight suit is now on display at the Feucht museum.

The shuttle does not look like Model E. It comes back gliding and lands on a runway. But Oberth had written in 1929, about his ship’s parachute, that he would do everything possible to arrive at a machine able to land in gliding flight.

December 1989

Hermann Oberth died during the night of December 28, 1989, in a Nuremberg hospital, at ninety-five. Some encyclopedias give the date as the 29th.

He died at the end of a year that had undone the world of his youth and that of his old age. The Berlin Wall fell on November 9. In Romania, the communist regime collapsed a few days before his death.

His daughter Erna watched over his papers until her own death, in 2012. In 1997, a crater on the Moon was given his name. An asteroid bears it too.

Sources: U. W. Jack, biography of Oberth (raketenflugplatz-berlin.de); entries of the Kulturstiftung der deutschen Vertriebenen, Encyclopedia.com, the New Mexico Museum of Space History, and the Austria-Forum; H. Oberth, “My Contributions to Astronautics” (1967), p. 140; Ways to Spaceflight, p. 409; for the list of distinctions, the works of 1977–1984, the launch of October 30, 1985, and the names given to a crater and an asteroid: the German and English Wikipedia entries; NASA (Apollo 11; mission STS-61-A/Spacelab D1). The death date of December 29 is that of the Encyclopædia Britannica and of ESA.