Steam Engine

The Steam Engine is a rocket engine used to launch rockets into space and recover rare resources. It is powered by Steam rather than solid fuel or oxidizer, and unlike more advanced rocket engines it does not require a fuel tank or an oxidizer tank. Steam must be piped into the engine from the rocket’s plumbing, so it is best treated as part of the rocket’s heat-management system as much as part of its propulsion system.

Because Steam is a gas that condenses when it cools, the fuel supply needs careful handling. Insulated Gas Pipes are the safest option when routing Steam to the engine, and the path should be kept as short as possible until better insulation becomes available late in the game. Once fueling is complete, any excess Steam should be vented from the pipes. Even Ceramic insulated pipes can eventually crack if the Steam loses enough heat and condenses inside them, because the pipe itself still absorbs heat from the gas.

A workable alternative is to use normal Gas Pipes made from a thermally reactive material such as Mafic Rock. These pipes quickly approach thermal equilibrium with the Steam, which reduces the risk of condensation. If the pipe temperature stays above Steam’s effective condensation point of 96.4 °C and the pipe is in a vacuum with no outside heat exchange, the Steam will not condense and damage the pipe.

Cool Steam Vents can provide enough Steam to run the engine, but the Steam usually needs to be heated before use. Building a chamber with Insulated Tiles and adding heat-generating devices can keep the Steam hot. Thermo Regulators can be used to cool hydrogen for other purposes while helping maintain the Steam supply. Since Cool Steam Vents are often far from the surface, any added heating should take the delivery distance into account.

The Steam Engine has limited range compared with stronger rocket engines. A rocket using only a Steam Engine can reach destinations up to 10,000 km away. Combining it with a Solid Fuel Thruster extends the reachable range to 20,000 km. In practice, this makes the Steam Engine a useful early rocket option for shorter interplanetary trips, especially when the available payload mass is tight.

A few practical notes:

• The engine will not accept fuel if it is entombed under Regolith.
• It does not take Wrong Element Damage and immediately ejects the gas instead.
• A rocket using a Steam Engine as its only power source can launch with a relatively small amount of Steam compared with other launch types.
• Steam Engines are often used with steam-based recovery setups, where launch exhaust is collected for water or power, though their low Steam temperature makes direct power return modest compared with a Hydrogen Engine.