Sublimation Chamber
Sealed Vacuum-Insulated Reactor for Ice-to-Vapor Sublimation
A sublimation chamber is a sealed, vacuum-insulated reactor that extracts water vapor from heated icy regolith at temperatures between 150 and 350 °C and pressures of 0.1 to 100 Pa. Internal baffles and screens isolate liberated vapor from dry solid tailings over a 30-minute residence time, achieving 80 percent water recovery. Operating on the lunar surface imposes severe mechanical and thermal constraints: fine regolith dust risks clogging vapor lines, necessitating 5 µm sintered metal filters, while abrasive particles degrade inlet and discharge seals. Additionally, batch processing subjects the structure to continuous cyclic temperature swings across 5,000 design cycles.
Sealed insulated reactor chamber where heated icy regolith from L3-ISR-ICE-HEAT undergoes ice-to-vapor sublimation under controlled vacuum/temperature conditions, with internal baffles to maximise vapor liberation and separator screens to retain solid tailings.
Purpose
Contain the sublimation process under conditions that maximise water yield (vapor pressure × residence time) while keeping solid regolith and downstream condenser flows isolated; provide the time and space needed for the slow diffusion of water vapor out of pore network of heated regolith.
Context
Receives heated regolith from L3-ISR-ICE-HEAT; outputs water vapor stream to L3-ISR-ICE-COND; outputs dry tailings to L3-ISR-ICE-CONT containment. Pilot-scale tests demonstrate >80% water recovery from icy regolith with proper residence time.
Principles
- ▸Sublimation rate governed by Hertz-Knudsen equation: J = α × P_eq / sqrt(2π × M_w × R × T)
- ▸Equilibrium vapor pressure of water-ice rises steeply with temperature: 1 Pa at 173 K, 100 Pa at 213 K, 10 kPa at 273 K
- ▸Vapor must diffuse out of regolith porosity — characteristic time scale = L² / D_eff (typical hours for cm-scale grains)
- ▸Internal stirring or particle agitation accelerates effective diffusion by exposing fresh particle surfaces
- ▸Internal baffle geometry separates vapor extraction from solid tailings retention
- ▸Operating pressure 0.1–100 Pa maintained by L3-ISR-ICE-COND condenser pull — chamber acts as buffer between thermal stage and cold trap
Typical implementations
- ▸NASA Glenn Pilot-Scale Drilling Thermal Method (ScienceDirect Acta Astronautica 2022) — 80% recovery in continuous-flow chamber
- ▸Paragon ICICLE deployed-tent sublimation volume (ICES 2024-109)
- ▸LUWEX integrated water extraction reactor (Adv Space Res 2026)
- ▸Apollo-era thermogravimetric analysis of returned samples — heritage characterization
- ▸Industrial sublimation reactors (food, pharma) — mature terrestrial analog
Lunar considerations
- ▸Vacuum environment already provides the low-pressure condition — chamber needs only thermal sealing
- ▸Dust ingress to vapor-extraction port mitigated by sintered metal filter (5 µm)
- ▸Chamber must withstand cyclic temperature swings as batches of regolith flow through
- ▸Long-life seals at chamber inlet (regolith feed) and outlet (tailings discharge) — rotary lock chambers or piston feeders
- ▸Sublimation efficiency depends on regolith ice form (granular ice grains vs. cemented matrix) — design must accommodate both
- ▸Vapor cold-spot prevention: chamber walls always above local condensation temperature to avoid wasting cold-trap capacity
Specifications
Functional
| primary function | Provide controlled environment for ice-to-vapor sublimation from heated regolith |
| inputs | Heated regolith (200–350 °C) from L3-ISR-ICE-HEAT, Vacuum condition maintained by L3-ISR-ICE-COND pull, Heat from external heater (maintain wall temperature) |
| outputs | Water vapor stream to L3-ISR-ICE-COND (~1 kg/hr nominal), Dry regolith tailings to L3-ISR-ICE-CONT, Process telemetry: chamber pressure/temperature, vapor flow rate |
| chamber volume l | 50 |
| operating pressure pa | 0.1, 100 |
| operating temperature c | 150, 350 |
| regolith residence time min | 30 |
| sublimation efficiency percent | 80 |
| vapor flow rate kg per hour max | 2 |
| design thermal cycles | 5000 |
Physical
| mass kg | 35 |
| dimensions | 500 × 400 × 400 mm reactor + integrated thermal jacket |
| materials | Inconel 625 inner liner (corrosion-resistant), 316L stainless outer shell, Sintered Inconel filter at vapor port (5 µm), MLI + aerogel insulation between liners, Particle agitator: tungsten-carbide-tipped impeller, Rotary or piston feed/discharge seals |
| operating temperature c | -180, 350 |
| vacuum compatibility | True |
Operational
| power consumption w aux | 100 |
| thermal range c | -180, 350 |
| lifetime hours | 5000 |
| mtbf hours | 3000 |
Interfaces
Provides
- Water vapor at 1-100 Pa
- Dry regolith tailings
- Chamber pressure/temperature/flow
Requires
- Heated icy regolith
- Agitator drive + sensors (~100 W)
- Wall temperature maintenance heat
Cite this entry
Lunar Ark Codex. "Sublimation Chamber" (L3-ISR-ICE-SUBL). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-ISR-ICE-SUBL
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.