Chapter 6

🌱 Lunar Base Life Support

Essentials of Life Support

For humans to live on the Moon, the following four things are essential (values from WIA-SPACE-011 §5.4, §6.1.2, §6.2.1, and §6.3.1):

1. Oxygen Supply System

Oxygen Generation

Water Electrolysis

• Method: H₂O → H₂ + O₂
• Yield: 1 kg of water → 0.89 kg of oxygen
• Equipment: PEM electrolyzer or alkaline electrolyzer
• Efficiency: >90%, with at least 0.84 kg of oxygen per person per day and a 7-day high-pressure oxygen backup (§6.1.2)

Carbon Dioxide Removal

A person exhales about 1 kg of CO₂ per day, the removal capacity required by §6.1.3. If it is not removed, the CO₂ concentration reaches dangerous levels; the standard caps it at 0.5% (5000 ppm).

Method 1: Chemical Absorption

• Lithium hydroxide (LiOH): 2LiOH + CO₂ → Li₂CO₃ + H₂O
• Single-use; used on the Apollo spacecraft

Method 2: 4-Bed Molecular Sieve

• Adsorbs CO₂ with zeolite
• Regenerable by vacuum/heating
• Currently in use on the ISS

Method 3: Sabatier Reactor

• CO₂ + 4H₂ → CH₄ + 2H₂O
• Converts CO₂ into methane and water
• The water is electrolyzed again to recover oxygen
• A key step toward closing the oxygen loop (§6.1.3 allows either this or a 4-bed molecular sieve)

2. Water Recycling

The Water Cycle

The standard sets a minimum water recovery rate of 95% (§6.2.2). In 2023, NASA reported that the ISS water recovery system had reached about 98% recovery.

Recycling Systems

1. Urine Processing (Urine Processor Assembly, UPA)

• Separates water from urine by distillation
• Recovery rate: 85-90% (§6.2.2)
• Residue: discharged or treated as concentrated waste

2. Humidity Condensate Recovery

• Condenses airborne moisture (breath, sweat)
• Target: 100% recovery of condensate (§6.2.2); on the ISS, condensate is processed by the Water Processor Assembly of the Water Recovery System (WRS)

3. Water Purification

• Multi-stage filtration: removes particles
• Ion exchange: removes minerals
• UV sterilization: inactivates microorganisms
• Final inspection: confirms potable quality
• Storage: a 30-day emergency supply (§6.2.2)

3. Food Supply

Early Stage: Supply from Earth (2026-2030)

• Freeze-dried food
• Shelf-stable for 2-5 years, about 2 kg per person per day (§6.3.1)
• Mass: about 730 kg per person per year, a major logistics cost at current delivery prices

Mid Stage: Hybrid (2030-2040)

• 50% supplied from Earth, 50% grown locally (§6.3.2)
• Fresh vegetables grown in greenhouses
• Vitamins and protein supplied from Earth

Long Term: Self-Sufficiency (2040+)

• More than 90% produced locally (§6.3.3)
• Cultivation of vegetables, grains, and fruit
• Cultured meat or fish farming

4. Lunar Greenhouse

Design

• Size: 20-50 m² per person in the transition phase, rising to 50-100 m² per person for self-sufficiency (§6.3.2-6.3.3)
• Structure: Inflatable or modular
• Lighting: LED (red/blue, optimized for photosynthesis)
• Temperature: 18-24°C
• Humidity: 60-80%

Cultivated Crops

The crop list follows §6.3.3; growing periods are typical terrestrial values.

Crop	Growing Period	Nutritional Value	Priority
Lettuce	30 days	Vitamins A, C	High
Tomato	60-90 days	Vitamin C, lycopene	High
Potato	90-120 days	Carbohydrates, potassium	Very high
Wheat	120 days	Carbohydrates, protein	Medium
Soybean	90-120 days	Protein, fat	High

Hydroponics

• Grows plants in a nutrient solution instead of soil
• Uses much less water than soil-based farming
• Fast growth rate
• Fewer pests and diseases

5. Environmental Control and Life Support System (ECLSS)

System Composition

Subsystem	Function	Criticality
Atmosphere control	Oxygen supply, CO₂ removal	Top priority
Temperature control	Cooling/heating	Top priority
Humidity control	Dehumidification/humidification	High
Pressure control	Maintaining cabin pressure	Top priority
Fire detection/suppression	Safety	High
Air purification	Contaminant removal	High

Atmospheric Composition

• Oxygen: 21% (Earth level; §6.1.1)
• Nitrogen: 78%
• Pressure: 101.3 kPa (1 atm)
• CO₂: < 0.5% (5000 ppm or less)
• Humidity: 40-60%

6. Waste Management

Solid Waste

• Recycling: Separation and reuse of plastics and metals
• Incineration: Burning combustibles to recover energy
• Composting: Converting organic matter into fertilizer

Liquid Waste

• Urine: water recovered by the UPA
• Laundry water: reused after filtration
• Laboratory wastewater: stored after chemical treatment

7. Emergency Response

Life Support Backup

• Oxygen tanks: 7 days of emergency oxygen (§11.2)
• Water storage: 30 days of drinking water
• Food reserves: 90 days of emergency food
• Backup power: Batteries + generators

Failure Response

• At least N+1 redundancy for all critical systems (§11.1)
• Real-time monitoring and alarms
• Automatic switchover to backup systems
• Stock of spare repair parts

Conclusion

The lunar base life support system builds on the experience of the ISS, but aims for a higher closed-loop rate and the use of local resources. Dependence on Earth will be high at first, but the base will gradually increase its independence and develop into a largely self-sufficient base. The next chapter covers the day-to-day operations of the lunar base.