Storable propellant alternatives from asteroid organics

Background

The rq-0-14 resolution identified storable propellants from asteroid organics as a fallback pathway if cryogenic LH2/LOX storage proves too challenging at L4/L5. Carbonaceous chondrite asteroids contain 1-5% organic compounds including hydrocarbons, amino acids, and nitrogen-bearing molecules. These could potentially serve as feedstock for storable propellants such as hydrazine derivatives, ammonium dinitramide (ADN), or simple hydrocarbon fuels that avoid the cryogenic storage problem entirely.

Why This Matters

If cryogenic boiloff management (rq-0-30) proves impractical or prohibitively power-intensive, storable propellants become the critical fallback. The performance penalty (lower Isp) would need to be weighed against:

• Elimination of active cryogenic cooling power requirements
• Indefinite storage without boiloff losses
• Simpler propellant transfer operations
• Compatibility with different thruster types

This decision affects transport vehicle engine selection, mission delta-V budgets, and the entire propellant logistics architecture.

Key Considerations

• Asteroid organic content varies significantly by type and individual body
• Synthesis pathways from raw organics to usable propellants are complex
• Storable propellants typically offer 250-320s Isp vs. 450s for LH2/LOX
• Toxicity of traditional storables (hydrazine, NTO) complicates handling
• Green storable alternatives (ADN, HAN) have less flight heritage
• Chemical processing complexity may exceed water electrolysis

Research Directions

1. Asteroid organic inventory: Characterize the organic compounds available in carbonaceous chondrite feedstock and identify which propellant synthesis pathways are thermodynamically favorable.

2. Synthesis complexity assessment: Compare the processing chain complexity for storable propellant production against water electrolysis + cryogenic storage, including mass, power, and crew requirements.

3. Performance impact modeling: Calculate mission delta-V penalties for switching from LH2/LOX to storable propellants across Phase 0-1 mission profiles.

4. Green storable propellant feasibility: Evaluate whether ADN or HAN-based propellants can be synthesized from asteroid-derived feedstock.

5. Hybrid propellant architecture: Assess a dual-propellant strategy using storable propellants for stationkeeping/low-delta-V operations and reserving cryogenics for high-performance asteroid retrieval missions.