Eclss Assessment

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)

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)