Hydrogen Engine

The Hydrogen Engine is a late-game rocket engine that uses hydrogen as fuel and is capable of sending rockets farther than Steam Engines or Petroleum Engines. In Spaced Out!, it is the most powerful engine available, making it well suited for long-range trips and for rockets carrying many modules. Like other high-tier engines, it provides 600 W of power through a rocket electrical port.

Its main advantage is range, but it also has a very useful property during maintenance: the engine itself contains no stored material, so it can be dismantled in a pinch to recover steel or other construction resources. This makes it more flexible than fuel tanks or oxidizer tanks, which cannot be removed without losing their contents or causing refueling problems. The same practical consideration applies to rockets using Petroleum Engines.

The Hydrogen Engine produces a very large amount of extremely hot steam during both takeoff and landing. Each trip releases roughly 4–5 tonnes of steam at above 1800 °C, for a total of about 9 tonnes of steam and around 70 million kDTU of heat per launch cycle. This exhaust output does not depend on how far the rocket travels, so even short trips produce the same thermal load.

That heat is dangerous to nearby infrastructure. It can damage liquid hydrogen pipes, melt most refined metals, and boil common liquids. Rocket platforms and rocket parts do not exchange heat with fluids, so the rocket itself will not melt from contact with its own exhaust, but loading and unloading ports, power wiring, automation wiring, and metal tiles can be destroyed unless they are made of Steel. Because of this, exposed launch infrastructure usually needs insulation or active cooling if it is expected to survive repeated launches.

The exhaust can also be turned into a major resource stream instead of being wasted. A common approach is to enclose the launch path with Drywall or Tempshift Plates and Insulated Tiles, then use Mechanized Airlocks to close the chamber as soon as the rocket launches or lands. Captured exhaust can be condensed by a Steam Turbine into water, or its heat can be harvested for power by larger steam-based setups.

A round trip’s exhaust can be electrolyzed into roughly 1 tonne of hydrogen and 8 tonnes of oxygen, which is enough hydrogen to refill a single liquid fuel tank and far more oxygen than a typical rocket fleet can use. If the steam is processed efficiently, the heat alone can produce a substantial amount of energy, making a properly built exhaust recovery system potentially resource-positive.

• The engine is strong enough that its exhaust heat is often the bigger design challenge than its fuel use.
• Exhaust recovery works best when the launch shaft spans the full height of the asteroid, allowing steam to be captured and condensed efficiently.
• If you only need to reclaim materials quickly, dismantling the engine is viable because it does not store fuel internally.
• Steel is the safest material for nearby launch infrastructure, especially for ports, wiring, and tiles exposed to exhaust heat.