Hydrogen Reactant Storage Tank
Cryogenic / High-Pressure Composite H2 Storage Vessel with MLI
Carbon-fiber-overwrapped composite vessel storing hydrogen as either supercritical fluid (~30 bar, 20 K) or warm high-pressure gas (~300 bar, ~250 K) — depending on architecture — with multi-layer insulation (MLI), broad-area cooled shield, and parasitic-load cryocooler tap to keep boil-off below 0.01–0.05 %/day.
Purpose
Hold the entire lunar-night hydrogen reactant inventory between charge and discharge cycles with minimal mass loss and sufficient discharge rate for the L3-ESS-FC-STACK across 336 hours of operation.
Context
Fed by L3-ESS-FC-ELEC at 30 bar gaseous H2; output to L3-ESS-FC-STACK at regulated 5–10 bar via L3-ESS-FC-BOP. Thermally tied to L1-TCS (passive radiator) and L1-CRY (active cryocooler tap if cryogenic architecture chosen). Sized to hold ~85 kg H2 (10 kWe × 330 hr / 55 kWh/kg / 0.7 efficiency).
Principles
- ▸Liquid hydrogen density 70.85 kg/m³ at 20 K, 1 atm; supercritical fluid 30 bar, 32 K is similar density without two-phase complications
- ▸Gaseous H2 at 300 bar, 290 K: density ~20 kg/m³; 700 bar: ~40 kg/m³ — higher pressure improves volumetric density at cost of tank mass
- ▸Multi-layer insulation (MLI) typical: 30 layers aluminized Mylar separated by Dacron netting; vacuum jacketed; conductive heat flux 0.1–0.5 W/m² at 80 K outer / 20 K inner
- ▸Boil-off rate for MLI-insulated cryotanks 0.01–0.05 %/day on Earth, lower in lunar vacuum (no convection)
- ▸Composite Type-IV/V tanks: HDPE or all-composite liner with carbon-fiber-epoxy overwrap; burst safety factor 2.25, fatigue rated 10,000+ cycles
- ▸Hydrogen embrittlement of metallic liners requires either non-metallic liners (Type IV/V) or carefully selected austenitic steels
Typical implementations
- ▸Space Shuttle External Tank LH2 storage: aluminum-lithium 2195, foam insulation
- ▸Centaur upper-stage LH2 tank: stainless steel pressurized membrane
- ▸Toyota Mirai 700-bar Type-IV composite tank (terrestrial automotive H2)
- ▸ULA ACES (Advanced Cryogenic Evolved Stage) — long-duration LH2 storage with thermodynamic vent
- ▸NASA Cryogenic Boil-Off Reduction System (CBRS) — combined MLI + cryocooler
- ▸Lockheed Martin lunar lander LH2 storage concepts
Lunar considerations
- ▸Lunar vacuum eliminates convective heat ingress; MLI is highly effective
- ▸Direct solar heating mitigated by deploying tank in lunar regolith trench or shading by Ark structure
- ▸Cold-soaked night-side surface (-173 °C) is colder than tank interior at warm-gas storage — passive radiator effective during night
- ▸Cryogenic architecture requires active cryocooler (~50 W cooling at 20 K) tapped from L1-CRY infrastructure
- ▸High-pressure warm-gas alternative avoids cryocooler but increases tank mass and reduces volumetric density
- ▸Micrometeoroid + dust shielding: ~1 mm aluminum bumper plus 10 cm regolith berm reduces impact risk over 100 years
Specifications
Functional
| primary function | Store H2 reactant inventory between charge and discharge cycles |
| inputs | Pressurized H2 from L3-ESS-FC-ELEC (30 bar), Cryocooler cold finger from L1-CRY (if cryogenic architecture), Pressure / temperature telemetry interfaces |
| outputs | Regulated H2 supply to L3-ESS-FC-STACK via L3-ESS-FC-BOP, Tank pressure, temperature, mass-gauge telemetry, Pressure-relief venting (safety only) |
| capacity kg h2 | 100 |
| internal volume m3 | 1.4 |
| operating pressure bar | 30 |
| burst pressure bar | 67 |
| operating temperature k | 20, 35 |
| max boil off percent per day | 0.05 |
| design lifetime years | 25 |
| fatigue pressure cycles | 10000 |
Physical
| mass kg | 120 |
| dimensions | 1.5 m diameter × 1.2 m length (cylindrical, hemispherical end caps) |
| materials | HDPE liner (Type IV) or all-composite liner (Type V), T700 / T800 carbon-fiber overwrap with epoxy resin, 30-layer MLI blanket (aluminized Mylar + Dacron spacer), Outer vacuum jacket: 6061-T6 aluminum with sealed weld, Cryocooler thermal strap: high-purity copper or graphite fiber, Boss/valve interfaces: 316L stainless steel with metal seals |
| operating temperature k | 20, 35 |
| exterior temperature c | -180, 130 |
| vacuum jacket pressure torr | 1e-05 |
| ultimate load g | 6 |
Operational
| power consumption w cooling | 50 |
| thermal range k | 20, 35 |
| lifetime years | 25 |
| mtbf hours | 250000 |
| expected h2 loss kg per year | 18.25 |
Interfaces
Provides
- Regulated H2 supply at 5–10 bar
- Tank pressure/temperature/mass telemetry
Requires
- H2 charging at 30 bar
- Cold-finger interface for active cooling (~50 W at 20 K)
- Outer-jacket radiator path to deep space
- Anchored mounting in shaded trench / berm
Cite this entry
Lunar Ark Codex. "Hydrogen Reactant Storage Tank" (L3-ESS-FC-H2TK). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-ESS-FC-H2TK
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.