Water Vapor Condenser / Cold Trap
Paragon ICICLE-Class Freeze-Distillation Cold Trap
A water vapor cold trap is a cryogenically cooled vessel that captures sublimated lunar water vapor by direct deposition onto surfaces maintained between 88 and 150 K. Operating in the lunar vacuum, the unit freezes vapor into ice before it escapes into space, while selectively venting non-water volatiles like hydrogen and carbon monoxide. In lunar permanently shadowed regions where ambient temperatures range from 88 to 110 K, the copper-finned trap recovers up to 5 kilograms of water per 24-hour cycle at over 95 percent efficiency, though surface fouling from co-condensing ammonia and carbon dioxide necessitates periodic thermal bake-outs.
Cryogenically-cooled condenser surface that captures sublimated water vapor from the sublimation chamber by deposition (vapor → ice → liquid water) at low temperatures (~150 K target), simultaneously achieving coarse purification via the ICICLE 'freeze distillation' principle.
Purpose
Recover the water vapor produced upstream into a captured solid/liquid phase before it can escape to vacuum, with selective deposition that rejects most non-water volatiles for purer downstream electrolysis feedstock.
Context
Pulls vacuum on L3-ISR-ICE-SUBL chamber and L3-ISR-EXC-AUG vapor port; delivers captured water to L3-ISR-ICE-CONT containment vessel for melting and transfer to L1-WTR. Uses cooling from L1-CRY infrastructure or passive radiative loss to PSR ambient.
Principles
- ▸Vapor deposition: water vapor at 150–200 K condenses directly to ice on cold surface (skipping liquid phase)
- ▸ICICLE freeze-distillation: cold-trap geometry optimized for high water retention and low non-water volatile retention (Paragon SDC)
- ▸Capture efficiency >95% achievable with proper geometry and sufficient cooling capacity
- ▸Periodic warm-up cycle melts captured ice → liquid water transferred to storage; trap then re-cooled for next cycle
- ▸Multiple condensers in parallel for continuous operation: one capturing while another off-loading
- ▸Cooling sources: passive radiator to PSR ambient (88-110 K), active cryocooler tapping L1-CRY, or thermal mass
Typical implementations
- ▸Paragon ICICLE Cold Trap (ICES-2024-109, ICES-2023-136, ICES-2022-105) — purpose-built lunar water capture
- ▸NASA RFC water-recovery cold traps (Apollo, Shuttle heritage)
- ▸Industrial freeze-drying lyophilizers (terrestrial analog)
- ▸Atmospheric water harvesting cold traps (terrestrial)
- ▸ESA PROSPECT volatile capture module (Luna-27)
- ▸LUWEX integrated capture chamber (Adv Space Res 2026)
Lunar considerations
- ▸PSR ambient 88-110 K is naturally below water deposition temperature — passive radiative cooling viable in shadowed siting
- ▸Cold-trap surface fouling from accumulated CO/CO2/NH3 reduces capture efficiency over time — periodic warm-up bake-out
- ▸Cycle time: 24-hour fill cycle then heated transfer; aim for 90% duty cycle
- ▸Non-water volatiles (H2, He, CO, N2) pass through cold trap to L3-ISR-VOL-TRAP
- ▸Cold-trap mass scales with throughput; sized for full water-production rate of upstream stages
- ▸Long-mission cycle endurance: >10,000 freeze-thaw cycles required
Specifications
Functional
| primary function | Capture water vapor via cold-surface deposition and periodic transfer to liquid storage |
| inputs | Water vapor stream from L3-ISR-ICE-SUBL, Cooling from L1-CRY cryocooler tap or passive radiator, Periodic warm-up heater power for ice transfer |
| outputs | Liquid water delivered to L3-ISR-ICE-CONT containment vessel, Non-water vapor flow-through to L3-ISR-VOL-TRAP, Capture efficiency, fouling, cycle-state telemetry |
| capture efficiency percent | 95 |
| operating temperature k | 88, 150 |
| warm up temperature c | 30 |
| vapor throughput kg per hour | 1.5 |
| trap capacity kg water | 5 |
| cycle time hr fill transfer | 24 |
| design cycles | 10000 |
| cooling power required w | 100 |
Physical
| mass kg | 30 |
| dimensions | 500 × 400 × 400 mm cryogenic vessel |
| materials | 316L stainless inner trap surface (water-compatible), Copper finned cold-trap geometry for high surface area, MLI + vacuum jacket for thermal isolation, Outer aluminum jacket, Sintered metal filters at inlet/outlet, Optional cryocooler cold-finger interface |
| operating temperature k | 88, 320 |
| vacuum compatibility | True |
Operational
| power consumption w | 100 |
| power consumption w warmup | 500 |
| thermal range k | 88, 320 |
| lifetime years | 15 |
| mtbf hours | 50000 |
Interfaces
Provides
- Captured liquid water after warm-up cycle
- Non-water volatile pass-through stream
- Capture efficiency, cycle state, fouling indicators
Requires
- Water vapor stream
- Cooling power ~100 W at 100 K (active mode)
- Passive radiator path (passive mode)
- Warm-up heater (~500 W during transfer)
Cite this entry
Lunar Ark Codex. "Water Vapor Condenser / Cold Trap" (L3-ISR-ICE-COND). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-ISR-ICE-COND
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.