Multi-Stage Cryogenic Volatile Trap
Cascaded Cryotrap Bank for CO/CO2/N2/H2/He Capture
The multi-stage cryogenic volatile trap is a 50 kg, four-stage bank of sequentially cooled condensation vessels (operating at 200 K, 88 K, 20 K, and 4 K) that selectively captures and separates volatile species—including carbon dioxide, nitrogen, hydrogen, and helium—from heated regolith vapor. Operating at vapor pressures of 1 to 10 Pa, the system exploits permanently shadowed lunar environments where an 88 K ambient temperature allows passive condensation of heavier species. However, capturing volatile hydrogen and helium requires active cryocooling delivering 30 W at 20 K and 5 W at 4 K, while vacuum-jacketed sorbent beds must endure repeated thermal regeneration cycles.
Cascade of cryogenic cold traps at progressively colder temperatures (200 K → 70 K → 20 K → 4 K) that sequentially condense different volatile species from the heated regolith outlet stream: CO2 first, then CO/N2, then H2, then He.
Purpose
Selectively capture each volatile species into its own collection vessel using temperature-staged condensation — much more energy-efficient than condensing all species at the coldest temperature, and naturally provides species separation.
Context
Receives vapor stream from L3-ISR-ICE-COND (non-water pass-through) and from L3-ISR-VOL-HEAT (high-T volatiles); separated species delivered to L3-ISR-VOL-SEP for final purification and L3-ISR-VOL-STORE for storage. Cooling tap from L1-CRY infrastructure.
Principles
- ▸Condensation temperature for each species at trap pressure (~1-10 Pa): H2O ~150 K, CO2 ~140 K, NH3 ~150 K, CO ~70 K, N2 ~75 K, CH4 ~85 K, H2 ~20 K, He ~4 K
- ▸Cascade trap: warmer trap removes higher-condensing species first, then colder traps capture progressively lighter gases — reduces total cryogenic energy demand
- ▸Cryosorption on activated carbon or zeolite at 70-100 K captures CO/CO2/N2 with high capacity per surface area
- ▸Active cryocoolers (Stirling, pulse-tube) provide cooling power down to 4 K; PSR ambient provides passive cooling to ~88 K
- ▸Periodic warm-up cycle releases captured gas into storage vessel; trap then re-cooled
- ▸He-3/He-4 separation via thermal diffusion or selective adsorption — Joule-Thomson valve at 4 K
Typical implementations
- ▸ESA PROSPECT ProSPA cold trap series for volatile analysis (Luna-27)
- ▸NASA MSL Sample Analysis at Mars (SAM) cryogenic concentration
- ▸JWST cryogenic instruments (4 K passive radiator + active cooler)
- ▸Industrial cryogenic air separation (linear cascade)
- ▸Helium-3 cryogenic separation R&D (academic, terrestrial)
- ▸Apollo helium-3 study (Wittenberg & Cameron 1986)
Lunar considerations
- ▸PSR ambient temperature ~88 K is below CO/CO2/N2 condensation — passive cold traps viable for these species
- ▸H2 and He capture requires active cryocooling — large energy cost; trade-off vs. value
- ▸Multiple parallel trap banks for continuous operation (one capturing while another off-loading)
- ▸Cryosorbent material (activated carbon, zeolite) regenerated by thermal cycling — finite cycle life
- ▸Long mission requires sorbent replacement via L1-MNT
- ▸He-3 is high-value (potential fusion fuel) but extraction depends on volatile inventory at south pole site
Specifications
Functional
| primary function | Selective species capture via cryogenic temperature cascade |
| inputs | Multi-species vapor stream from L3-ISR-ICE-COND / L3-ISR-VOL-HEAT, Cooling power from L1-CRY (active stages), Passive PSR cold for higher-T stages |
| outputs | Separated CO/CO2/N2 streams to L3-ISR-VOL-SEP, Separated H2 stream to L3-ESS-FC-H2TK (high-value), Separated He stream to L3-ISR-VOL-STORE (with optional He-3 enrichment), Trap state telemetry |
| trap stages | 4 |
| stage temperatures k | 200, 88, 20, 4 |
| capture efficiency percent per stage | 95 |
| cooling power required w at 4k | 5 |
| cooling power required w at 20k | 30 |
| cycle time hr | 24 |
| design cycles | 10000 |
Physical
| mass kg | 50 |
| dimensions | Cascade of 4 vessels, total envelope 1.0 × 0.5 × 0.5 m |
| materials | 316L stainless inner trap surfaces, Activated carbon / zeolite cryosorbent beds, MLI + vacuum jacket for each stage, Outer aluminum jacket, Cryocooler cold-finger interfaces (Stirling/pulse-tube), Stainless gas-routing manifold with cryo valves |
| operating temperature k | 4, 320 |
| vacuum compatibility | True |
Operational
| power consumption w | 200 |
| thermal range k | 4, 320 |
| lifetime years | 15 |
| mtbf hours | 50000 |
| sorbent replacement interval years | 5 |
Interfaces
Provides
- Separated species streams
- Recovered H2 (ISRU augmenting electrolysis)
- He / He-3 to dedicated storage
Requires
- Non-water vapor pass-through
- High-temperature volatile vapor
- Active cooling at 4 K and 20 K
- Passive radiator path
Cite this entry
Lunar Ark Codex. "Multi-Stage Cryogenic Volatile Trap" (L3-ISR-VOL-TRAP). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-ISR-VOL-TRAP
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.