Hydrogen Storage (IF)

Hard Science-Fiction Setting

H₂ Storage Styles

Assume ~25% ship mass tied up in H₂ + tankage. These are flavor-forward, not rules.

• Dewar Spheres (baseline) — Rigid, multilayer-insulated cryo spheres buried in the hull. Pros: lowest boil-off, clean plumbing. Cons: big spheres eat layout; hydrogen embrittles everything.
• Densified/Slush LH₂ — Sub-cooled liquid with suspended micro-ice. Pros: ~10–15% more density, less boil-off. Cons: mixing hardware; slush clumps if cooldown is botched.
• Cryo-Compressed H₂ (CCH₂) — Cold gas at hundreds of bar (≈70–100 K, 250–350 bar). Pros: much better volumetric density than plain LH₂; smaller tanks. Cons: heavy pressure vessels; ugly failure modes.
• Balloon Farm — External inflatable cryo bladders under a sunshade, held in a micrometeoroid net. Pros: absurd volume per kg of structure. Cons: pinholes, ice frosting, “snowing hydrogen”; cinematic in a chase.
• Dirigible Tanks (rigid shell + internal bladders) — Zepp-style honeycomb shells stuffed with thin H₂ bladders. Pros: micrometeoroid-tolerant; swap bladders like cartridges. Cons: many fittings = many leak paths.
• Torus Tanks — A ring tank around the non-spinning spine. Pros: doubles as a bumper/Whipple layer; short plumbing runs. Cons: complicates spin-separation and docking.
• Foam-Core Cryo — Integral Al–Li tanks with structural foam/aerogel inside. Pros: kills slosh, damps pressure spikes, good impact tolerance. Cons: hard to inspect/repair; trapped contamination.
• Capillary/Wick Tanks — Porous liners hold LH₂ by surface tension. Pros: easy propellant management in micro-g; no slosh. Cons: sensitive to contamination; lower effective capacity.
• Shadow Keel — Long shaded spine radiating to deep space; H₂ circulates in narrow capillaries along it. Pros: passive cooling, striking silhouette. Cons: vulnerable to side hits; thermal gradients warp frames.
• Saddle Drop-Tanks — Jettisonable LH₂ pods bolted outside for the outbound leg. Pros: cheap Δv now, toss the mass later; great “cut ’em loose!” moment. Cons: staging complexity; debris politics.
• Tethered Cryo Barges — Uncrewed H₂ pods on short tethers; reel in to refuel, cut loose in combat. Pros: isolates risk; easy swap at depots. Cons: tangles, plume heating, easy targets.
• Boil-Off RCS — Accept steady boil-off and pipe it to cold-gas thrusters. Pros: nothing wasted; stealthy micro-impulses. Cons: reveals you as tanks warm; logistics clock always ticking.
• Cold-Sink Integration — Run superconductors/radiators off the LH₂ loop. Pros: one cryo plant, double duty. Cons: heat spikes force emergency venting at the worst time.
• Micro-Sphere Beds (niche) — Glass microspheres loaded with H₂ under heat/pressure, released by heating. Pros: very safe, puncture-tolerant. Cons: poor mass/volume efficiency; good for suits/skiffs, not liners.

Flavor Notes

• Leaks are invisible plumes; find them by frost crusts and “snow.”
• Venting leaves a sunlit sparkly cone that screams “we’re here.”
• Embrittlement creeps: old ships groan, welds pop, fittings whistle.
• Crash drill: “Shade the farm, isolate the loop, dump the pods.”