Liquid Hydrogen
Liquid Hydrogen is the Liquid state of Hydrogen. It is obtained by cooling Hydrogen down to -255.15 °C (-425.47 °F) (condensation point - 3 °C).
Usage
Liquid Hydrogen is used as fuel for the Hydrogen Engine, the most powerful Rocket engine.
It is required to reach Starmap Destinations located at and beyond the 170,000 km band, including the Temporal Tear.
Spaced Out! has its own version of the Hydrogen Engine, which is the final rocket engine unlocked and the most generally powerful: it has the greatest engine power, height allowance (tied with the Petroleum Engine), and electrical power generation (tied with the Steam Engine). It has the greatest range among Large Liquid Fuel Tank-using engines at 16 hexes per tank, though with one tank it has less range than a Radbolt Engine.
Production
Liquid Hydrogen is produced by cooling Hydrogen from its gas state using Super Coolant. Its production is one of the end-game challenges.
- Take note of the freezing point too; it is only a few degrees away from the vaporization point. As such, using Liquid Hydrogen to reliably cool Hydrogen is near impossible.
Transportation
Due to its extremely limited temperature range, moving liquid hydrogen is as much of a challenge as producing it. Barring access to large amounts of Insulation, any liquid hydrogen which remains stationary inside a pipe system will quickly exchange heat with the surrounding pipes, damaging them and being released into the environment if it crosses its boiling point. It is therefore extremely important to stop liquid hydrogen from backing up in pipes - usually by ensuring it runs on a closed loop, where the final step in a pipeline is simply feeding it back into the hydrogen condenser.
- Pipe contents will not overheat or freeze if they contain 1kg or less of liquid (1/10 of capacity). A Liquid Valve set to 1kg/s will prevent pipes of any material from freezing so long as the hydrogen keeps circulating.
- Insulated Liquid Pipes made of Ceramic or Insulation can handle a full loop of 10kg/s hydrogen without cracking. It may be necessary to supercool the hydrogen to -261 °C if using Ceramic.
- Any loop can alternate between LH and Super Coolant packets in order to maintain a low pipe temperature, but this may still be susceptible to cracking if exposed to extreme heat (e.g. bunker tiles, pipes buried in regolith, or rocket exhaust).
Pumping liquid hydrogen in one direction (as opposed to a loop) is best done by placing Radiant Liquid Pipes in a sealed vacuum and pre-cooling them using Super Coolant, or running them through a reservoir of Super Coolant with an additional cooling source (e.g. a counterflowing coolant pipe).
