ECLSS Assessment Skill (Life Support)

Read CONVENTIONS.md at the repo root before proceeding.

This skill sizes the Environmental Control and Life Support System for crewed vehicles and habitats. ECLSS is the system that keeps humans alive — it manages atmosphere, water, waste, and thermal comfort inside the pressurized volume.

Before You Begin

Ask the user (if not already known):

1. Crew size and mission duration? (These two numbers drive everything)
2. Open-loop or closed-loop? (Open = consumables carried from Earth; Closed = recycling. Short missions (<2 weeks) typically open-loop; long missions require closure.)
3. Cabin atmosphere? (Sea-level: 101.3 kPa, 21% O₂ / 79% N₂. Low-pressure: 55.2 kPa, 34% O₂ — reduces structural mass but changes fire risk. EVA-compatible: 56.5 kPa, 34% O₂ — eliminates pre-breathe.)
4. Gravity environment? (Microgravity, partial-g lunar/Mars, or sustained-g rotation — affects fluid management, fire behavior, and ECLSS hardware selection.)
5. What design phase?

Applicable Phases

• Primary: Phase A (consumables vs. regenerative trade), Phase B (subsystem sizing)
• Supporting: Phase C (detailed design), Phase D (crew qualification testing)

Metabolic Reference Rates (Per Crew-Member Per Day)

Parameter	Value	Notes
O₂ consumption	0.84 kg/day	~840 L at STP
CO₂ production	1.00 kg/day	Respiratory quotient ~0.87
Metabolic water production	0.35 kg/day	From respiration
Drinking water	2.0 kg/day	Minimum; 2.5 nominal
Food (dry mass)	0.6 kg/day	~2500 kcal/day
Hygiene water	1.5-4.0 kg/day	Sponge bath vs. shower
Solid waste	0.11 kg/day
Metabolic heat	120 W average	70W resting, 300W+ exercise

Reference: NASA-STD-3001 (Crew Health), BVAD (Baseline Values and Assumptions Document).

Analysis Domains

1. Atmosphere Management

• O₂ supply: Stored gas (high-pressure tanks), stored liquid (cryogenic), electrolysis (water → O₂ + H₂), SFOG (Solid Fuel Oxygen Generator — emergency backup).
  • Electrolysis sizing: $P_{elec} = \dot{m}{O_2} \cdot E{spec}$ where $E_{spec}$ ≈ 12-15 MJ/kg O₂.
• CO₂ removal:
  • Open-loop: LiOH canisters (~0.9 kg LiOH per kg CO₂ removed). Simple, proven, but consumable.
  • Regenerative: CDRA (Carbon Dioxide Removal Assembly) using zeolite beds — ISS heritage. Recovers CO₂ for Sabatier or venting.
  • Partial CO₂ level target: <5.3 mmHg (0.7 kPa) for long-duration; <7.6 mmHg for short missions.
• N₂ makeup: Leak rate replacement (~0.05-0.1 kg/day for ISS-class modules) + airlock losses.
• Trace contaminant control: Activated charcoal + catalytic oxidizer for VOCs, CO, NH₃.

2. Water Recovery

• Open-loop: Carry all water. Mass = crew × rate × duration. Gets prohibitive beyond ~2 weeks.
• Closed-loop water recovery:
  • Urine processing: Vapor compression distillation (VCD) or ISS WPA — ~85-93% recovery.
  • Humidity condensate: Collected from cabin air. ~1.0-1.5 kg/person/day.
  • Total water recovery: ISS achieves ~90% overall closure.
• Water quality: Potable (iodine or silver biocide), hygiene, technical (coolant loops — separate circuit).
• Mass savings from closure: $\Delta m = m_{water,daily} \times duration \times crew \times (1 - recovery_rate)$

3. Thermal & Humidity Control (Cabin)

• Cabin temperature: 18-27°C (65-80°F) nominal range.
• Humidity: 25-75% relative humidity. Target 40-60% for comfort.
• Metabolic heat removal: $Q_{crew} = N_{crew} \times 120W$ average, plus equipment waste heat in cabin.
• Cabin air circulation: Minimum 0.08 m/s airflow to prevent CO₂ pockets in microgravity.
• Interface with thermal-assessment: Cabin heat rejection adds to spacecraft radiator load.

4. Habitable Volume

• Minimum: NASA-STD-3001 recommends minimum volume per crew-member based on mission duration:
  • <2 weeks: 2.5 m³/person (capsule-class)
  • 2 weeks - 6 months: 10 m³/person
  • 6 months - 3 years: 25 m³/person (quality of life, exercise, private space)
• Functional zones: Sleep, hygiene, galley, exercise, work, stowage, EVA airlock.
• Noise: <60 dBA continuous (sleep areas <50 dBA).
• Radiation shelter: Area where crew retreats during solar particle events — additional shielding.

5. Consumables vs. Regenerative Trade

The break-even for regenerative systems:

• Regenerative equipment mass ($m_{equip}$) + power penalty vs. consumable mass ($m_{cons/day} \times duration$).
• Break-even duration: $t_{break} = m_{equip} / m_{cons/day}$
• Rule of thumb: Electrolysis + CDRA + WPA pays for itself in mass beyond ~15-30 days for 4 crew.

Output Format

1. ECLSS Sizing Report (eclss_report.md): Subsystem sizing, consumables manifest, regeneration rates, closure percentages.
2. Consumables Budget: Mass per day and total mission consumables (O₂, N₂, LiOH, water, food).
3. Power & Thermal Load: ECLSS power demand and heat rejection to power-assessment and thermal-assessment.
4. 🟢 / 🟡 / 🔴 status: Habitability and consumable margin status.

Interface

• Reads from: /requirements/, /analysis/thermal-assessment/ (cabin heat loads), /analysis/power-assessment/ (available power for electrolysis/CDRA), /analysis/structural-assessment/ (pressurized volume)
• Writes to: /analysis/eclss-assessment/
• Consumed by: systems-engineering-assessment (mass/power/thermal roll-up), cost-modeling (consumables cost), isru-assessment (in-situ O₂/H₂O production can supplement ECLSS)