Space

Space is the uppermost domain in From the Depths.

Gravity
Gravity starts decreasing linearly at 700m altitude an reaches zero at 1300m. For balance-reasons, gravity re-enables above 1800m altitude, reaching sea-level strength at 2500m, and further increasing with altitude.

Air
Air density starts decreasing exponentially at 275m, and reaches zero at 1200m.

Despite the lack of atmosphere, there is still drag in space.

Ion Thruster
The Ion Thruster (under the Air category) is one of only two types of thruster to work in space, the other being the steam jet (found in steam). They can also work in the atmosphere and underwater, but are less efficient than other thrusters for doing so. Compared to (simple) Jet Engines, Ion Thrusters have 60% of the power efficiency and 30% of the thrust density, which correspond to a a break-even altitude of 380 m and 440 m respectively. They produce no heat in comparison to jets meaning that they are an option for stealth planes. Due to their low power output it is recommended to only use them on lightweight craft.

Steam Jet (Link to engine)

The most power dense thruster in the game, working equally well in all environments, water, air, and space, producing 10000 thrust while consuming 5000 steam/sec at max power, making it the most fuel inefficient thruster in the game as well.