Fire, depressurization, refuge and internal emergency response
Prepare for events that immediately threaten the crew: fire, pressure loss, smoke, compartment isolation and internal evacuation.
Mastery objectives
- identify the functions, interfaces and degraded scenarios specific to the subject
- repeat simple calculations and verify units, assumptions and margins
- turn a principle into a verifiable procedure or decision
- connect the subsystem to human, energy and logistics constraints
1. Spacecraft fire combines combustion, toxicity and loss of function
In a pressurized volume, fire is not only a heat source. It creates smoke and contaminants, can damage wiring and fluid lines and may force the crew to abandon a compartment. Detection, warning and extinguishing therefore have to be designed together with ventilation and respiratory protection. An extinguisher that can only be reached through the fire is not a real safety barrier.
2. Detect early without training the crew to ignore alarms
Sensors must detect smoke, heat or combustion products early enough to matter, while excessive false alarms destroy trust. Procedures include rapid confirmation, localization, ventilation actions and respiratory protection. An alarm should tell the crew what is happening, where it is happening and what first action is expected.
3. Depressurization: locate, isolate and count useful seconds
A leak may be slow or rapid. Response depends on volume, leak rate and the time required to close a hatch or enter a refuge. Pressure compartments and isolatable doors turn a large base into manageable volumes. Differential-pressure measurements and makeup-gas flow help distinguish a real leak from a failed sensor.
4. Refuge: survive while diagnosis continues
A refuge needs breathable atmosphere, carbon-dioxide control, water, communications, power and medical capability for its design duration. Its purpose is to create time to inspect the damaged area, decide on repair or wait for another option. A refuge is therefore a small autonomous life-support system, not merely a strong room.
5. Internal evacuation and an injured crewmember
A crewmember may be unable to move without assistance. Routes, openings and equipment must support assisted transport, stretchers or suited extraction. Procedures assign roles and muster points so that nobody is forgotten inside an isolated module.
6. After the flame: contamination and safe return to service
Extinguishing visible fire is not the end of the event. The crew must measure atmosphere, inspect wiring, materials and structure, identify the initiating cause and decide which equipment can safely be re-energized. Restoration should be staged and documented because partially damaged hardware can become the cause of the next incident.
7. Detection: a sensor is not a decision
A smoke, pressure or temperature detector must not be mistaken for a complete diagnosis. A pressure change can result from leakage, an airlock cycle or a deliberate operation; particles can trigger an optical detector without an established fire. Emergency logic should combine several cues, timestamp them and relate them to operational context. A useful alarm states what was detected, where, for how long, which confirmations exist and what automatic action has already occurred. Procedures must also include contradictory sensors, because opening a door or stopping ventilation at the wrong time can create an additional hazard.
8. Isolation: stop propagation without trapping the crew
Closing a bulkhead or valve appears simple until people, power, air or an evacuation route depend on that path. Isolation should be designed as a sequence: identify the compartment, confirm occupant location, transfer indispensable functions, close propagation paths and verify that the healthy zone remains stable. Depressurization adds a physical constraint because differential pressure can make a door impossible to open until pressures are equalized. Rescue paths must therefore match pressure physics and the actual capacity of the refuge.
9. Recovery after an incident: restore service without erasing evidence
After extinguishing a fire or sealing a leak, immediate restart is not the next objective. Pressure stability, toxic products, temperature, electrical integrity and hidden damage must first be checked. Alarm logs, valve states, sensor measurements and damaged parts should be preserved for causal analysis. In a distant settlement this investigation partly substitutes for immediate outside expertise. It should lead to a configuration action such as inspecting similar components, changing a procedure, adding protection or modifying training. Return to normal operation is therefore the final step of an learning loop, not simply the end of the emergency.
10. Worked example: time to a pressure threshold
An 80 m³ module loses an average 0.8% of initial pressure per minute in a simplified teaching model. Reaching a 10% loss therefore takes 10/0.8 = 12.5 min. If the crew needs 6 min to confirm the leak, equip one person and isolate the compartment, only 6.5 min of time margin remain. The example shows why localization and isolation must be rapid.
Calculated case study: sizing an emergency refuge oxygen reserve
TEACHING ASSUMPTION — A refuge must support four people for two days. For the exercise, oxygen use is set to q = 0.84 kg per person per day, followed by a 30% margin. This value is only a teaching input and must be replaced by the mission design value.
Let n be the number of people; q oxygen mass per person per day in kg/(person·day); d duration in days; m the dimensionless margin; and M oxygen mass in kg.
M = n × q × d = 4 × 0.84 × 2 = 6.72 kg. With m = 0.30, M_plan = 6.72 × 1.30 = 8.736 kg, or about 8.74 kg.
This is only a first consumables balance. A real refuge must also handle pressure, storage, regulation, CO₂ removal, humidity, temperature, leakage and the possibility of remaining isolated longer than planned.
11. Exercise
Write the first five minutes of response to smoke detected in the workshop while one crewmember is missing from the muster point. State who confirms the alarm, who protects atmosphere, who locates the person and under what conditions a search is abandoned.
12. Reasoned solution
A robust sequence confirms the alarm with several cues, locates the crew, preserves a refuge route, isolates ventilation and power where that reduces risk, then closes the compartment and checks neighbouring-zone stability. Simply shutting every door without checking crew location or pressure differential can create another hazard.
13. Validation mini-project
Build a combined fire-and-leak emergency analysis covering detection, barriers, breathing equipment, isolation, refuge, casualty handling, communications, restoration and end-of-alert criteria.
Fire and pressure loss are time-critical because the habitat itself is the survival system
Inside a Martian habitat, fire is more than visible flame. It can consume oxygen, release toxic products, damage electrical insulation, contaminate filters and destroy the functions needed to control the atmosphere. The immediate objective is therefore not simply “extinguish the fire.” The crew must detect the event, stop energy and airflow that feed propagation when appropriate, protect breathing, isolate the affected volume and preserve at least one safe refuge.
Depressurization creates another race against time. The rate of pressure loss depends on leak area, pressure, temperature and flow regime, but operations teams usually need a simpler question first: how much time remains before a declared threshold is crossed? Pressure trend, acoustic detection and compartment isolation turn an uncertain leak into a bounded emergency. The procedure should tell crews which doors or valves can be closed without trapping someone on the wrong side.
Refuge design changes the emergency from immediate evacuation of the whole settlement into controlled survival while diagnosis continues. A refuge needs atmosphere, carbon-dioxide removal, thermal control, communication, lighting, medical capability, water and sanitation for the stated duration. Physical seats alone do not define capacity. Refuge readiness should be exercised with the actual crew and emergency supplies.
After an incident, recovery is a technical investigation. Smoke residue can poison sensors, water can damage electronics, overheated structures can lose strength and emergency isolation can leave systems in unusual configurations. Returning to service requires inspection, cleaning, testing and configuration records. If the crew restores everything quickly but destroys the evidence of cause, the same failure can recur.
Four emergency concepts that determine whether the crew gains time or loses it
Early detection
Recognition of abnormal heat, smoke, gas composition, pressure trend or other signatures early enough that local control remains possible.
Isolation
Deliberate separation of a compartment, energy source or flow path to stop propagation while preserving viable escape and refuge routes.
Refuge
Protected compartment that can independently support occupants for a defined emergency duration.
Recovery evidence
Measurements, logs, photographs and component condition preserved so the cause and extent of damage can be established before return to normal service.
Calculation laboratory
Formula 1 — simple time to a pressure threshold
Quantitative mini-lessons
Time to pressure threshold
- 1 — Concrete question
- What does “t_pressure = (P0 - P_min) / r_loss” compute in “Time to pressure threshold”?
- 2 — Intuition without symbols
- Under a constant-rate approximation, available time is allowable pressure drop divided by loss rate.
- 3 — Quantities
- t_pressure: time before reaching threshold [min]; P0: initial pressure [kPa]; P_min: minimum allowable pressure [kPa]; r_loss: assumed constant pressure-loss rate [kPa/min]
- 4 — Formula
- t_pressure = (P0 - P_min) / r_loss
- 5 — Read aloud
- Read “t_pressure = (P0 - P_min) / r_loss” by naming every operation, subscript and grouping explicitly.
- 6 — Symbols and meaning
- t_pressure: time before reaching threshold [min]; P0: initial pressure [kPa]; P_min: minimum allowable pressure [kPa]; r_loss: assumed constant pressure-loss rate [kPa/min]
- 7 — Pronunciation
- The “Read aloud” line above is the oral reference for “Time to pressure threshold”. Any subscript, exponent or grouping that changes the meaning of the relation should be spoken explicitly.
- 8 — Units
- t_pressure [min]; P0 [kPa]; P_min [kPa]; r_loss [kPa/min]
- 9 — Convention
- For “Time to pressure threshold”, substitute values without changing the reference frame, time basis, system boundary or sign convention halfway through the calculation. Stated units: t_pressure [min]; P0 [kPa]; P_min [kPa]; r_loss [kPa/min].
- 10 — Why this operation
- In “Time to pressure threshold”, division relates a quantity to a reference, duration or capacity; the denominator must belong to the same case and remain non-zero.
- 11 — Assumptions
- The relation “t_pressure = (P0 - P_min) / r_loss” applies here only to the scenario described by the card. Inputs must be mutually consistent and satisfy the physical assumptions associated with “Time to pressure threshold”.
- 12 — Independent check
- A second method or inverse relation should recover the same order of magnitude.
- 13 — Numerical case
- With P0 = 70 kPa, P_min = 55 kPa, r_loss = 3 kPa/min: t_pressure = (70 - 55) / 3 = 5 min.
- 14 — Why the calculation works
- The numerical case applies “t_pressure = (P0 - P_min) / r_loss” directly to the stated values. The calculation is meaningful because the quantities are substituted into the same relation before the result is interpreted for “Time to pressure threshold”.
- 15 — Verification
- Quick check: multiplying the result by the denominator should reconstruct the numerator of “Time to pressure threshold” within rounding.
- 16 — Mental estimate
- Before calculating “Time to pressure threshold” precisely, round the inputs to one useful digit and predict the sign and order of magnitude. The detailed result should remain consistent with that estimate.
- 17 — Interpretation
- Treat this time as a prioritization estimate, never as a guarantee that leak flow remains constant.
- 18 — What the result does not prove
- For “Time to pressure threshold”, the number obtained answers only the model “t_pressure = (P0 - P_min) / r_loss” under the stated scenario. It does not by itself validate the input data or the model outside those conditions.
- 19 — Sensitivity
- Vary one input at a time around the nominal case to identify what drives the result of “Time to pressure threshold” and whether that variation can change the mission decision.
- 20 — Guided and autonomous exercises
Guided exercise. Recalculate this scenario: With P0 = 68 kPa, P_min = 56 kPa, r_loss = 2 kPa/min: t_pressure = (68 - 56) / 2 ?
Detailed guided correction — open after trying
With P0 = 68 kPa, P_min = 56 kPa, r_loss = 2 kPa/min: t_pressure = (68 - 56) / 2 = 6 min. The decision must then be checked against the module margins and assumptions.
Autonomous exercise. Recalculate this scenario: With P0 = 62 kPa, P_min = 50 kPa, r_loss = 1.5 kPa/min: t_pressure = (62 - 50) / 1.5 ?
Autonomous correction — open after trying
With P0 = 62 kPa, P_min = 50 kPa, r_loss = 1.5 kPa/min: t_pressure = (62 - 50) / 1.5 = 8 min. The decision must then be checked against the module margins and assumptions.
- 21 — Mission decision
- Treat this time as a prioritization estimate, never as a guarantee that leak flow remains constant.
Refuge oxygen endurance
- 1 — Concrete question
- What does “T_O2 = Q_O2 / (N_crew × q_O2)” compute in “Refuge oxygen endurance”?
- 2 — Intuition without symbols
- Refuge duration depends on usable stock divided by total crew consumption.
- 3 — Quantities
- T_O2: oxygen endurance [j]; Q_O2: usable oxygen mass [kg]; N_crew: crew count [personnes]; q_O2: use per person per day [kg/personne/j]
- 4 — Formula
- T_O2 = Q_O2 / (N_crew × q_O2)
- 5 — Read aloud
- Read “T_O2 = Q_O2 / (N_crew × q_O2)” by naming every operation, subscript and grouping explicitly.
- 6 — Symbols and meaning
- T_O2: oxygen endurance [j]; Q_O2: usable oxygen mass [kg]; N_crew: crew count [personnes]; q_O2: use per person per day [kg/personne/j]
- 7 — Pronunciation
- The “Read aloud” line above is the oral reference for “Refuge oxygen endurance”. Any subscript, exponent or grouping that changes the meaning of the relation should be spoken explicitly.
- 8 — Units
- T_O2 [j]; Q_O2 [kg]; N_crew [personnes]; q_O2 [kg/personne/j]
- 9 — Convention
- For “Refuge oxygen endurance”, substitute values without changing the reference frame, time basis, system boundary or sign convention halfway through the calculation. Stated units: T_O2 [j]; Q_O2 [kg]; N_crew [personnes]; q_O2 [kg/personne/j].
- 10 — Why this operation
- In “Refuge oxygen endurance”, division relates a quantity to a reference, duration or capacity; the denominator must belong to the same case and remain non-zero.
- 11 — Assumptions
- The relation “T_O2 = Q_O2 / (N_crew × q_O2)” applies here only to the scenario described by the card. Inputs must be mutually consistent and satisfy the physical assumptions associated with “Refuge oxygen endurance”.
- 12 — Independent check
- Multiplying the result by the denominator should reconstruct the numerator.
- 13 — Numerical case
- With Q_O2 = 4.8 kg, N_crew = 6 personnes, q_O2 = 0.8 kg/personne/j: T_O2 = 4.8 / (6 × 0.8) = 1 j.
- 14 — Why the calculation works
- The numerical case applies “T_O2 = Q_O2 / (N_crew × q_O2)” directly to the stated values. The calculation is meaningful because the quantities are substituted into the same relation before the result is interpreted for “Refuge oxygen endurance”.
- 15 — Verification
- Quick check: multiplying the result by the denominator should reconstruct the numerator of “Refuge oxygen endurance” within rounding.
- 16 — Mental estimate
- Before calculating “Refuge oxygen endurance” precisely, round the inputs to one useful digit and predict the sign and order of magnitude. The detailed result should remain consistent with that estimate.
- 17 — Interpretation
- Never claim this endurance without also checking CO2, water, heat, power and sanitation.
- 18 — What the result does not prove
- For “Refuge oxygen endurance”, the number obtained answers only the model “T_O2 = Q_O2 / (N_crew × q_O2)” under the stated scenario. It does not by itself validate the input data or the model outside those conditions.
- 19 — Sensitivity
- Vary one input at a time around the nominal case to identify what drives the result of “Refuge oxygen endurance” and whether that variation can change the mission decision.
- 20 — Guided and autonomous exercises
Guided exercise. Recalculate this scenario: With Q_O2 = 7.2 kg, N_crew = 6 personnes, q_O2 = 0.8 kg/personne/j: T_O2 = 7.2 / (6 × 0.8) ?
Detailed guided correction — open after trying
With Q_O2 = 7.2 kg, N_crew = 6 personnes, q_O2 = 0.8 kg/personne/j: T_O2 = 7.2 / (6 × 0.8) = 1.5 j. The decision must then be checked against the module margins and assumptions.
Autonomous exercise. Recalculate this scenario: With Q_O2 = 8.4 kg, N_crew = 5 personnes, q_O2 = 0.84 kg/personne/j: T_O2 = 8.4 / (5 × 0.84) ?
Autonomous correction — open after trying
With Q_O2 = 8.4 kg, N_crew = 5 personnes, q_O2 = 0.84 kg/personne/j: T_O2 = 8.4 / (5 × 0.84) = 2 j. The decision must then be checked against the module margins and assumptions.
- 21 — Mission decision
- Never claim this endurance without also checking CO2, water, heat, power and sanitation.
Planned oxygen mass
- 1 — Concrete question
- What does “M_O2_plan = N_crew × q_O2 × d_refuge × (1 + m_margin)” compute in “Planned oxygen mass”?
- 2 — Intuition without symbols
- Planned stock starts from nominal consumption and then adds an explicit margin.
- 3 — Quantities
- M_O2_plan: planned oxygen mass [kg]; N_crew: crew count [personnes]; q_O2: use per person per day [kg/personne/j]; d_refuge: target refuge duration [j]; m_margin: fractional margin [sans dimension]
- 4 — Formula
- M_O2_plan = N_crew × q_O2 × d_refuge × (1 + m_margin)
- 5 — Read aloud
- Read “M_O2_plan = N_crew × q_O2 × d_refuge × (1 + m_margin)” by naming every operation, subscript and grouping explicitly.
- 6 — Symbols and meaning
- M_O2_plan: planned oxygen mass [kg]; N_crew: crew count [personnes]; q_O2: use per person per day [kg/personne/j]; d_refuge: target refuge duration [j]; m_margin: fractional margin [sans dimension]
- 7 — Pronunciation
- The “Read aloud” line above is the oral reference for “Planned oxygen mass”. Any subscript, exponent or grouping that changes the meaning of the relation should be spoken explicitly.
- 8 — Units
- M_O2_plan [kg]; N_crew [personnes]; q_O2 [kg/personne/j]; d_refuge [j]; m_margin [sans dimension]
- 9 — Convention
- For “Planned oxygen mass”, substitute values without changing the reference frame, time basis, system boundary or sign convention halfway through the calculation. Stated units: M_O2_plan [kg]; N_crew [personnes]; q_O2 [kg/personne/j]; d_refuge [j]; m_margin [sans dimension].
- 10 — Why this operation
- In “Planned oxygen mass”, multiplication combines the factors that directly build the requested quantity; the factors must describe the same case.
- 11 — Assumptions
- The relation “M_O2_plan = N_crew × q_O2 × d_refuge × (1 + m_margin)” applies here only to the scenario described by the card. Inputs must be mutually consistent and satisfy the physical assumptions associated with “Planned oxygen mass”.
- 12 — Independent check
- A second method or inverse relation should recover the same order of magnitude.
- 13 — Numerical case
- With N_crew = 4 personnes, q_O2 = 0.84 kg/personne/j, d_refuge = 2 j, m_margin = 0.3 sans dimension: M_O2_plan = 4 × 0.84 × 2 × (1 + 0.3) = 8.736 kg.
- 14 — Why the calculation works
- The numerical case applies “M_O2_plan = N_crew × q_O2 × d_refuge × (1 + m_margin)” directly to the stated values. The calculation is meaningful because the quantities are substituted into the same relation before the result is interpreted for “Planned oxygen mass”.
- 15 — Verification
- Quick check: for any non-zero factor, dividing the result by that factor should recover the other expected contribution in “Planned oxygen mass”.
- 16 — Mental estimate
- Before calculating “Planned oxygen mass” precisely, round the inputs to one useful digit and predict the sign and order of magnitude. The detailed result should remain consistent with that estimate.
- 17 — Interpretation
- Size storage and distribution to the planned value, not nominal demand without margin.
- 18 — What the result does not prove
- For “Planned oxygen mass”, the number obtained answers only the model “M_O2_plan = N_crew × q_O2 × d_refuge × (1 + m_margin)” under the stated scenario. It does not by itself validate the input data or the model outside those conditions.
- 19 — Sensitivity
- Vary one input at a time around the nominal case to identify what drives the result of “Planned oxygen mass” and whether that variation can change the mission decision.
- 20 — Guided and autonomous exercises
Guided exercise. Recalculate this scenario: With N_crew = 6 personnes, q_O2 = 0.8 kg/personne/j, d_refuge = 1.5 j, m_margin = 0.25 sans dimension: M_O2_plan = 6 × 0.8 × 1.5 × (1 + 0.25) ?
Detailed guided correction — open after trying
With N_crew = 6 personnes, q_O2 = 0.8 kg/personne/j, d_refuge = 1.5 j, m_margin = 0.25 sans dimension: M_O2_plan = 6 × 0.8 × 1.5 × (1 + 0.25) = 9 kg. The decision must then be checked against the module margins and assumptions.
Autonomous exercise. Recalculate this scenario: With N_crew = 5 personnes, q_O2 = 0.84 kg/personne/j, d_refuge = 3 j, m_margin = 0.2 sans dimension: M_O2_plan = 5 × 0.84 × 3 × (1 + 0.2) ?
Autonomous correction — open after trying
With N_crew = 5 personnes, q_O2 = 0.84 kg/personne/j, d_refuge = 3 j, m_margin = 0.2 sans dimension: M_O2_plan = 5 × 0.84 × 3 × (1 + 0.2) = 15.12 kg. The decision must then be checked against the module margins and assumptions.
- 21 — Mission decision
- Size storage and distribution to the planned value, not nominal demand without margin.
Internal evacuation margin
- 1 — Concrete question
- What does “M_evac = t_available - t_egress” compute in “Internal evacuation margin”?
- 2 — Intuition without symbols
- The decision depends on the difference between time to hazard and the time actually needed to place people in safety.
- 3 — Quantities
- M_evac: evacuation margin [min]; t_available: time available before hazardous condition [min]; t_egress: time required to evacuate [min]
- 4 — Formula
- M_evac = t_available - t_egress
- 5 — Read aloud
- Read “M_evac = t_available - t_egress” by naming every operation, subscript and grouping explicitly.
- 6 — Symbols and meaning
- M_evac: evacuation margin [min]; t_available: time available before hazardous condition [min]; t_egress: time required to evacuate [min]
- 7 — Pronunciation
- The “Read aloud” line above is the oral reference for “Internal evacuation margin”. Any subscript, exponent or grouping that changes the meaning of the relation should be spoken explicitly.
- 8 — Units
- M_evac [min]; t_available [min]; t_egress [min]
- 9 — Convention
- For “Internal evacuation margin”, substitute values without changing the reference frame, time basis, system boundary or sign convention halfway through the calculation. Stated units: M_evac [min]; t_available [min]; t_egress [min].
- 10 — Why this operation
- In “Internal evacuation margin”, subtraction measures a margin or difference between comparable quantities expressed in the same frame.
- 11 — Assumptions
- The relation “M_evac = t_available - t_egress” applies here only to the scenario described by the card. Inputs must be mutually consistent and satisfy the physical assumptions associated with “Internal evacuation margin”.
- 12 — Independent check
- Adding the margin back to the subtracted term should reconstruct the initial state.
- 13 — Numerical case
- With t_available = 12.5 min, t_egress = 6 min: M_evac = 12.5 - 6 = 6.5 min.
- 14 — Why the calculation works
- The numerical case applies “M_evac = t_available - t_egress” directly to the stated values. The calculation is meaningful because the quantities are substituted into the same relation before the result is interpreted for “Internal evacuation margin”.
- 15 — Verification
- Quick check: adding the subtracted term back to the result should reconstruct the starting quantity in “Internal evacuation margin”.
- 16 — Mental estimate
- Before calculating “Internal evacuation margin” precisely, round the inputs to one useful digit and predict the sign and order of magnitude. The detailed result should remain consistent with that estimate.
- 17 — Interpretation
- Low margin requires reducing detection, donning or isolation delays.
- 18 — What the result does not prove
- For “Internal evacuation margin”, the number obtained answers only the model “M_evac = t_available - t_egress” under the stated scenario. It does not by itself validate the input data or the model outside those conditions.
- 19 — Sensitivity
- Vary one input at a time around the nominal case to identify what drives the result of “Internal evacuation margin” and whether that variation can change the mission decision.
- 20 — Guided and autonomous exercises
Guided exercise. Recalculate this scenario: With t_available = 8 min, t_egress = 5 min: M_evac = 8 - 5 ?
Detailed guided correction — open after trying
With t_available = 8 min, t_egress = 5 min: M_evac = 8 - 5 = 3 min. The decision must then be checked against the module margins and assumptions.
Autonomous exercise. Recalculate this scenario: With t_available = 6 min, t_egress = 5.2 min: M_evac = 6 - 5.2 ?
Autonomous correction — open after trying
With t_available = 6 min, t_egress = 5.2 min: M_evac = 6 - 5.2 = 0.8 min. The decision must then be checked against the module margins and assumptions.
- 21 — Mission decision
- Low margin requires reducing detection, donning or isolation delays.
Extinguishing-agent endurance
- 1 — Concrete question
- What does “T_agent = Q_agent / q_use” compute in “Extinguishing-agent endurance”?
- 2 — Intuition without symbols
- Agent quantity yields useful duration only relative to the planned discharge rate.
- 3 — Quantities
- T_agent: available discharge duration [min]; Q_agent: usable extinguishing agent [kg]; q_use: mean use rate [kg/min]
- 4 — Formula
- T_agent = Q_agent / q_use
- 5 — Read aloud
- Read “T_agent = Q_agent / q_use” by naming every operation, subscript and grouping explicitly.
- 6 — Symbols and meaning
- T_agent: available discharge duration [min]; Q_agent: usable extinguishing agent [kg]; q_use: mean use rate [kg/min]
- 7 — Pronunciation
- The “Read aloud” line above is the oral reference for “Extinguishing-agent endurance”. Any subscript, exponent or grouping that changes the meaning of the relation should be spoken explicitly.
- 8 — Units
- T_agent [min]; Q_agent [kg]; q_use [kg/min]
- 9 — Convention
- For “Extinguishing-agent endurance”, substitute values without changing the reference frame, time basis, system boundary or sign convention halfway through the calculation. Stated units: T_agent [min]; Q_agent [kg]; q_use [kg/min].
- 10 — Why this operation
- In “Extinguishing-agent endurance”, division relates a quantity to a reference, duration or capacity; the denominator must belong to the same case and remain non-zero.
- 11 — Assumptions
- The relation “T_agent = Q_agent / q_use” applies here only to the scenario described by the card. Inputs must be mutually consistent and satisfy the physical assumptions associated with “Extinguishing-agent endurance”.
- 12 — Independent check
- Multiplying the result by the denominator should reconstruct the numerator.
- 13 — Numerical case
- With Q_agent = 12 kg, q_use = 1.5 kg/min: T_agent = 12 / 1.5 = 8 min.
- 14 — Why the calculation works
- The numerical case applies “T_agent = Q_agent / q_use” directly to the stated values. The calculation is meaningful because the quantities are substituted into the same relation before the result is interpreted for “Extinguishing-agent endurance”.
- 15 — Verification
- Quick check: multiplying the result by the denominator should reconstruct the numerator of “Extinguishing-agent endurance” within rounding.
- 16 — Mental estimate
- Before calculating “Extinguishing-agent endurance” precisely, round the inputs to one useful digit and predict the sign and order of magnitude. The detailed result should remain consistent with that estimate.
- 17 — Interpretation
- Keep reserve for re-ignition or a second fire instead of using all nominal capacity on the first engagement.
- 18 — What the result does not prove
- For “Extinguishing-agent endurance”, the number obtained answers only the model “T_agent = Q_agent / q_use” under the stated scenario. It does not by itself validate the input data or the model outside those conditions.
- 19 — Sensitivity
- Vary one input at a time around the nominal case to identify what drives the result of “Extinguishing-agent endurance” and whether that variation can change the mission decision.
- 20 — Guided and autonomous exercises
Guided exercise. Recalculate this scenario: With Q_agent = 8 kg, q_use = 1 kg/min: T_agent = 8 / 1 ?
Detailed guided correction — open after trying
With Q_agent = 8 kg, q_use = 1 kg/min: T_agent = 8 / 1 = 8 min. The decision must then be checked against the module margins and assumptions.
Autonomous exercise. Recalculate this scenario: With Q_agent = 15 kg, q_use = 2.5 kg/min: T_agent = 15 / 2.5 ?
Autonomous correction — open after trying
With Q_agent = 15 kg, q_use = 2.5 kg/min: T_agent = 15 / 2.5 = 6 min. The decision must then be checked against the module margins and assumptions.
- 21 — Mission decision
- Keep reserve for re-ignition or a second fire instead of using all nominal capacity on the first engagement.
Refuge-place margin
- 1 — Concrete question
- What does “M_refuge = C_refuge - N_crew” compute in “Refuge-place margin”?
- 2 — Intuition without symbols
- Refuge capacity must be compared with the population that may converge on it during the emergency scenario.
- 3 — Quantities
- M_refuge: remaining refuge places [places]; C_refuge: available refuge capacity [places]; N_crew: people requiring refuge [personnes]
- 4 — Formula
- M_refuge = C_refuge - N_crew
- 5 — Read aloud
- Read “M_refuge = C_refuge - N_crew” by naming every operation, subscript and grouping explicitly.
- 6 — Symbols and meaning
- M_refuge: remaining refuge places [places]; C_refuge: available refuge capacity [places]; N_crew: people requiring refuge [personnes]
- 7 — Pronunciation
- The “Read aloud” line above is the oral reference for “Refuge-place margin”. Any subscript, exponent or grouping that changes the meaning of the relation should be spoken explicitly.
- 8 — Units
- M_refuge [places]; C_refuge [places]; N_crew [personnes]
- 9 — Convention
- For “Refuge-place margin”, substitute values without changing the reference frame, time basis, system boundary or sign convention halfway through the calculation. Stated units: M_refuge [places]; C_refuge [places]; N_crew [personnes].
- 10 — Why this operation
- In “Refuge-place margin”, subtraction measures a margin or difference between comparable quantities expressed in the same frame.
- 11 — Assumptions
- The relation “M_refuge = C_refuge - N_crew” applies here only to the scenario described by the card. Inputs must be mutually consistent and satisfy the physical assumptions associated with “Refuge-place margin”.
- 12 — Independent check
- Adding the margin back to the subtracted term should reconstruct the initial state.
- 13 — Numerical case
- With C_refuge = 8 places, N_crew = 6 personnes: M_refuge = 8 - 6 = 2 places.
- 14 — Why the calculation works
- The numerical case applies “M_refuge = C_refuge - N_crew” directly to the stated values. The calculation is meaningful because the quantities are substituted into the same relation before the result is interpreted for “Refuge-place margin”.
- 15 — Verification
- Quick check: adding the subtracted term back to the result should reconstruct the starting quantity in “Refuge-place margin”.
- 16 — Mental estimate
- Before calculating “Refuge-place margin” precisely, round the inputs to one useful digit and predict the sign and order of magnitude. The detailed result should remain consistent with that estimate.
- 17 — Interpretation
- Provide margin when injury, visitor load or an unavailable berth can change actual occupancy.
- 18 — What the result does not prove
- For “Refuge-place margin”, the number obtained answers only the model “M_refuge = C_refuge - N_crew” under the stated scenario. It does not by itself validate the input data or the model outside those conditions.
- 19 — Sensitivity
- Vary one input at a time around the nominal case to identify what drives the result of “Refuge-place margin” and whether that variation can change the mission decision.
- 20 — Guided and autonomous exercises
Guided exercise. Recalculate this scenario: With C_refuge = 6 places, N_crew = 6 personnes: M_refuge = 6 - 6 ?
Detailed guided correction — open after trying
With C_refuge = 6 places, N_crew = 6 personnes: M_refuge = 6 - 6 = 0 places. The decision must then be checked against the module margins and assumptions.
Autonomous exercise. Recalculate this scenario: With C_refuge = 12 places, N_crew = 9 personnes: M_refuge = 12 - 9 ?
Autonomous correction — open after trying
With C_refuge = 12 places, N_crew = 9 personnes: M_refuge = 12 - 9 = 3 places. The decision must then be checked against the module margins and assumptions.
- 21 — Mission decision
- Provide margin when injury, visitor load or an unavailable berth can change actual occupancy.
- Starting question
- If pressure is falling at an approximately steady measured rate, how much time remains before a declared minimum threshold?
- Read aloud
- Read: “time equals initial pressure minus minimum pressure, divided by pressure-loss rate.”
- Symbols, pronunciation and meaning
- P0 is current pressure; Pmin is the action threshold; r is measured pressure decrease per unit time; t is estimated remaining time.
- Units
- If pressure is in kilopascals and r is kilopascals per minute, the result is minutes.
- Origin and status of values
- Use measured local pressure trend only when it is reasonably stable over the short planning interval. The threshold comes from the approved emergency rule.
- Why this operation
- Subtraction gives how much pressure can still be lost before the threshold. Division by loss rate converts that remaining pressure margin into time.
- Substitution and calculation
- At 70 kPa, threshold 55 kPa and loss rate 3 kPa/min: t = (70 − 55) / 3 = 15 / 3 = 5 min.
- Calculator entry
- Enter (70 − 55) ÷ 3. Keep parentheses around the pressure difference.
- Mental estimate
- Fifteen kilopascals at three kilopascals each minute is five minutes, so the result is immediately reasonable.
- Independent check
- Multiply 5 min × 3 kPa/min = 15 kPa; subtract from 70 and recover 55 kPa.
- Physical or operational interpretation
- Five minutes is not five minutes of free work. It is the simplified time to the stated threshold if the leak rate does not worsen.
- Plain-English translation
- The crew has about five minutes before crossing 55 kPa under the measured constant-rate approximation.
- Variation / sensitivity
- If leak rate doubles to 6 kPa/min, estimated time falls to 2.5 min. Pressure-loss acceleration therefore matters strongly.
- Limit / assumption
- Real gas discharge is not generally linear. The formula is a short-horizon operational estimate and must be replaced by better modelling when data or conditions require it.
Formula 2 — refuge oxygen reserve duration
- Starting question
- How long can a known usable oxygen reserve support a refuge occupancy under a declared per-person consumption rate?
- Read aloud
- Read: “oxygen duration equals usable oxygen quantity divided by number of people times consumption per person.”
- Symbols, pronunciation and meaning
- QO2 is usable oxygen quantity; N is occupants; q is oxygen consumption per person per unit time; T is support duration.
- Units
- If Q is in kilograms and q in kilograms per person per day, N × q is kilograms per day and T is days.
- Origin and status of values
- Reserve quantity must be usable after regulator/pressure limits. Consumption rate is a planning assumption that should reflect emergency activity and system design.
- Why this operation
- Multiplication gives total crew consumption rate. Division asks how many such time blocks fit inside the usable reserve.
- Substitution and calculation
- For 4.8 kg usable O2, 6 people, and 0.8 kg/person/day: crew demand = 6 × 0.8 = 4.8 kg/day, so T = 1 day.
- Calculator entry
- Enter 4.8 ÷ (6 × 0.8). Keep the crew consumption product in parentheses.
- Mental estimate
- The reserve equals exactly six individual daily allocations, so one crew-day is expected.
- Independent check
- Multiply 1 day × 6 × 0.8 kg/person/day and recover 4.8 kg.
- Physical or operational interpretation
- Oxygen is only one refuge limit. Carbon-dioxide removal, heat, water and sanitation may end safe occupancy earlier.
- Plain-English translation
- The stated oxygen reserve supports six occupants for about one day at the assumed rate.
- Variation / sensitivity
- If occupancy falls to four people, oxygen-only duration becomes 1.5 days. If exertion raises q, duration decreases.
- Limit / assumption
- This is a consumable balance, not a complete atmosphere model. It ignores leakage, oxygen already in the cabin and system control behaviour unless those are included in Q.
Mission reasoning: detect, isolate, shelter and recover without creating a second emergency
Make detection actionable
A detector should lead to a defined response based on location, confidence and consequence. Multiple independent indicators can reduce false-alarm burden, but waiting for perfect certainty can waste the interval in which a small event remains controllable.
Isolate with occupant awareness
Closing a hatch can stop smoke or pressure loss while trapping a crewmember beyond the barrier. Emergency displays should show personnel location and planned escape/refuge options. Isolation authority must account for people as well as fluid topology.
Control energy sources
Electrical faults, batteries, heaters, oxygen-enriched local conditions and process chemicals can sustain fire. Procedures should identify what can be de-energized locally without disabling essential detection, lighting or refuge systems.
Treat breathing atmosphere as contaminated until verified
Visible flame extinction does not prove the compartment is safe. Carbon monoxide, particulates and decomposition products may remain. Re-entry requires measurements, protective equipment and a ventilation/filtration plan tied to actual sensor limits.
Preserve refuge independence
A refuge that depends on the same power bus, ventilation duct or data controller as the damaged zone may not be independent. Emergency readiness should test shared dependencies and identify what happens after one cross-cutting failure.
Recover through controlled configuration
After safing, every bypass, closed valve, tripped breaker and portable supply should be recorded. Return to service needs staged functional tests so the crew does not unknowingly restore the same hazardous path that initiated the event.
Emergency exercises — trade seconds for survivable configuration
Exercise A — Pressure trend
A compartment is at 68 kPa and losing 2 kPa/min. The action threshold is 56 kPa. Estimate time.
Reveal the reasoned solution
(68 − 56) / 2 = 6 min under the constant-rate approximation. The crew should use the trend to prioritize isolation and egress, not treat six minutes as guaranteed because leak flow can change.
Exercise B — Fire alarm with no flame
Two smoke sensors alarm in an equipment bay but the camera shows no visible flame. Should the crew ignore the alarm?
Reveal the reasoned solution
No. Hidden smouldering, electrical decomposition or sensor contamination are possible. Apply the approved verification/isolation procedure, inspect other indicators and protect the crew while avoiding unnecessary actions that could spread smoke.
Exercise C — Blocked hatch
The preferred isolation hatch would trap one crewmember in the affected zone. What should the procedure provide?
Reveal the reasoned solution
A preplanned alternate egress or local refuge option, personnel-location awareness and authority rules for delaying or sequencing isolation. Emergency isolation must not assume every person is already on the safe side.
Exercise D — Refuge oxygen
A refuge has 7.2 kg usable oxygen for six people at 0.8 kg/person/day. What is oxygen-only duration?
Reveal the reasoned solution
Crew use is 4.8 kg/day. 7.2 / 4.8 = 1.5 days. Verify that carbon-dioxide scrubbing, water, heat and sanitation also support at least that duration before claiming 1.5-day refuge capacity.
Exercise E — Post-fire return
Flame is extinguished and pressure is normal. May the crew immediately return to nominal operation?
Reveal the reasoned solution
Not automatically. Verify atmosphere toxicity/particulates, electrical insulation, structural and thermal damage, sensor function, filter contamination and the configuration of emergency isolations. Preserve evidence and perform staged return-to-service tests.
Exercise F — False alarm burden
Frequent nuisance alarms cause crews to delay response. What system-level fix is needed?
Reveal the reasoned solution
Investigate sensor placement, thresholds, contamination, maintenance and alarm logic while preserving real detection sensitivity. Training crews to ignore alarms is not a safe solution; the alarm system must earn trust through quality and prioritization.
Interactive beginner glossary
Emergency vocabulary below links detection, isolation, breathing protection, refuge capability and controlled recovery.
- fire — Uncontrolled combustion that can produce heat, flame, smoke, toxic gases and loss of equipment function.
- smoke — Airborne mixture of particles and gases generated by combustion or thermal decomposition.
- carbon monoxide — Toxic gas produced by incomplete combustion that interferes with oxygen transport in the body.
- depressurization — Loss of gas from a pressurized volume causing pressure to fall.
- leak rate — Rate at which gas, liquid or another resource escapes across an unintended opening or boundary.
- pressure threshold — Declared pressure value that triggers a specific protective action or operational state.
- isolation — Separation of a compartment, flow path or energy source to limit propagation of a hazard.
- compartment — Defined enclosed region that can be separated from neighbouring regions for pressure or hazard control.
- refuge — Protected area capable of sustaining occupants independently for a defined emergency duration.
- safe haven — Another term for a protected location used to shelter crew when the primary area is unsafe.
- egress — Movement from a hazardous area toward a safer compartment or exit route.
- internal rescue — Recovery of an injured or trapped person within the pressurized habitat or connected modules.
- self-rescue — Actions a threatened person can perform to reach safety without requiring another rescuer to enter the hazard.
- fire load — Amount and type of combustible material available to contribute energy and smoke to a fire.
- ignition source — Energy source capable of initiating combustion or damaging material so combustion begins.
- overcurrent protection — Electrical protective device or function that interrupts excessive current to limit damage and fire risk.
- smoke detector — Sensor intended to detect combustion aerosols or related signatures before conditions become severe.
- gas detector — Instrument that measures concentration of selected gases associated with atmosphere quality or hazards.
- false alarm — Alarm that occurs when the declared hazardous condition is not present, even though the detector may be responding to another stimulus.
- nuisance alarm — Repeated nonhazardous alarm that burdens operators and can reduce confidence in the alerting system.
- breathing protection — Equipment or procedure that supplies or filters breathable gas when the surrounding atmosphere is unsafe or uncertain.
- portable extinguisher — Locally carried device that applies an extinguishing agent to a limited fire under specified conditions.
- fire suppression — System or action intended to control or extinguish combustion.
- ventilation isolation — Closure or rerouting of airflow to prevent smoke or contamination spreading through ducts.
- pressure decay — Observed reduction in pressure over time, used to characterize leakage or system behaviour.
- emergency reserve — Consumable or capability intentionally held for abnormal or survival conditions.
- return to service — Controlled process of proving a repaired or recovered system is safe to resume its intended function.
- post-incident inspection — Examination performed after an emergency to identify damage, contamination and conditions affecting safe recovery.
- root cause — Underlying technical or organizational mechanism that explains why the event occurred and whose correction reduces recurrence.
- reconstruction — Systematic rebuilding of event sequence from logs, evidence, telemetry and witness information after an incident.
Operational depth: emergency capability exists only if the crew can execute it under degraded conditions
Exercise with doors and suits, not slides
Refuge and internal-rescue drills should use real hatch timing, protective equipment, lighting and communications. Paper procedures routinely underestimate movement, visibility and dexterity penalties.
Track who is where
Personnel location becomes critical during rapid isolation. Badge systems, check-in discipline or role boards can help, but the crew needs a fallback method when the tracking system itself fails.
Test shared dependencies
Refuge fans, scrubbers, detectors and communications should be mapped against electrical buses and control networks. A refuge that loses all essential functions with one upstream failure is a room, not a robust safe haven.
Protect emergency equipment from the hazard it serves
Extinguishers, breathing protection and leak kits must remain reachable when the primary hazard blocks the normal route. Distributed equipment reduces the chance that one compartment event removes every response tool.
Use staged re-entry
After an incident, remote sensors or protected reconnaissance can precede unprotected human entry. Re-entry criteria should specify atmosphere, temperature, electrical state and structural concerns rather than rely on appearance.
Turn every event into configuration learning
An incident can reveal unexpected airflow, alarm delays or access constraints. Corrective actions should update drawings, procedures, training and interface assumptions so the next crew inherits the knowledge rather than the same hidden trap.
Applied emergency cases: isolation, refuge and post-incident recovery
Applied emergency case — pressure trend should drive action before exact leak location is known
If pressure decay is accelerating, operators may not have time to locate the hole before taking protective action. The crew can close preplanned compartment boundaries, verify personnel locations and compare pressure trends on each side. This transforms a settlement-wide problem into a smaller search area. Acoustic tools, gas tracers or thermal methods can follow once survival margin is protected. The key is sequencing: diagnose enough to isolate safely, then investigate with more precision. A procedure that requires exact leak localization before any isolation may consume the only minutes in which the crew can preserve atmosphere and avoid exposing multiple modules to the same pressure loss.
Applied emergency case — smoke movement follows ventilation, not intuition
A small fire can contaminate distant modules if fans or ducts carry smoke away from the source. Emergency logic should know which dampers close automatically, which fans stop, and which flows must continue to protect refuge areas. Simply turning off all ventilation may create other hazards, including loss of carbon-dioxide control or thermal management. Crews need a map of airflow states and the ability to verify that isolation actually occurred. After suppression, filters and ducts may contain contaminants even where surfaces look clean. Recovery therefore includes ventilation inspection and controlled purge, not merely reopening the room where the flame was found.
Applied emergency case — batteries may require different firefighting logic
Electrical storage systems can produce heat, toxic products and re-ignition behaviour that differs from ordinary solid combustibles. The response plan should reflect the specific battery chemistry, enclosure, detection and cooling or isolation capability installed in the habitat. Operators need to know which extinguishing agents are compatible and how to monitor for continued heating after visible flame stops. This is an example of why generic “fire procedure” language is insufficient. Hazard-specific annexes can share command structure and refuge logic while still giving technically appropriate actions for batteries, electrical cabinets, oxygen-related incidents or chemical process areas.
Applied emergency case — internal rescue must not create two casualties
A rescuer entering a smoky or depressurizing area needs a defined protection level, communication path, retrieval strategy and stop condition. The emotional pressure to reach a colleague can override normal caution, so rescue rules should be rehearsed before the event. If atmosphere is uncertain, breathing protection and isolation may be required even when the casualty is visible only a few metres away. A second team should monitor time, atmosphere and route status. The purpose is not bureaucratic delay; it is ensuring that one trapped person does not become two or three because rescuers entered an environment whose hazards were not controlled.
Applied emergency case — refuge duration is controlled by the first limiting resource
An oxygen calculation can show thirty hours while carbon-dioxide sorbent lasts twenty, battery power eighteen and water forty. The refuge rating is then constrained by the shortest verified duration unless another recovery path exists. Emergency planning should therefore maintain a resource table for each refuge and update it when supplies, occupancy or equipment configuration change. Drills can reveal additional limits such as noise, heat or sanitation. This prevents the common error of advertising a refuge by one impressive storage figure. Survival duration is a system property created by all essential resources and by the ability to monitor them under emergency conditions.
Applied emergency case — post-incident evidence belongs to operations, not only investigators
A scorched connector, tripped breaker state or smoke pattern may explain the event, but well-intentioned cleanup can erase that evidence. The recovery leader should identify what can be photographed, bagged, logged or electrically captured before disturbance, while still removing immediate hazards. Telemetry clocks and crew observations should be preserved in a common timeline. The objective is practical prevention: understanding whether the initiating mechanism was overload, contamination, maintenance damage, software command or something else. A successful emergency response ends not when pressure is normal, but when the settlement has restored capability and reduced the chance of repeating the same failure.
Applied emergency case — drills should deliberately remove expected resources
A realistic exercise can declare one hatch blocked, one radio failed or one refuge fan unavailable. This tests whether the emergency plan contains genuine alternatives or simply assumes every supporting system works during the very event meant to challenge it. Crews should practice moving a casualty, accounting for personnel, isolating ventilation and establishing a safe atmosphere with degraded information. Observers then measure timing and identify where decisions stalled. The resulting corrections may involve equipment placement, interface labels, software displays or authority rules. Repeating the drill after changes is the only way to show that the improvement exists in practice rather than only in a revised document.
Operational review checklist
- Detect fire, smoke and pressure loss early with actionable alarms.
- Know personnel location before isolating compartments when possible.
- Preserve at least one viable egress or refuge path.
- Control energy and ventilation sources without disabling essential safety functions.
- Size refuge capacity by life support and duration, not seats alone.
- Keep emergency equipment accessible from more than one hazard zone.
- Treat post-fire atmosphere as unsafe until measured and cleared.
- Record all emergency configuration changes and temporary bypasses.
- Perform staged inspection and functional testing before return to service.
- Preserve logs and evidence long enough to identify and correct root cause.