Editing Robots and Vehicles (section)

=== Spacecraft Propulsion ===
The most important part of any spacecraft is its engine, and the most important features of any engine are the exhaust velocity, which determines how much fuel the rocket requires to reach a given speed, and the engine’s thrust, which determines how high the acceleration can be. Any rocket that has a thrust of less than approximately twice the gravity of a planet or moon cannot take off from that planet or moon. Sample thrusts and gravities are listed on the Escaping Gravity Wells table.
'''Hydrogen-Oxygen Rocket (HO):''' Though optimized with improved engine design and light-weight materials, these are essentially the same primitive rockets that humanity used to first reach the moon in the 20th century. These are rarely used and only common with groups too poor or primitive to safely manufacture metallic hydrogen.
'''Metallic Hydrogen Rocket (MH):''' Metallic hydrogen is a solid form of hydrogen created using exceedingly high pressures. Although naturally unstable, it can be stabilized with carefully controlled electrical and magnetic fields, and these field generators are an integral part of every metallic hydrogen fuel tank.
By selectively reducing these fields near the exhaust nozzle, small amounts of metallic hydrogen can be made to swiftly and explosively revert to conventional hydrogen gas, propelling the rocket with great force in an easily controlled fashion. Metallic hydrogen engines are used in most planetary landers and short range vehicles.
'''Plasma Rocket (P):''' This drive heats hydrogen into plasma and accelerates it using a powerful electrical field. This type of rocket was very common in the mid 21st century, but has been superseded by fusion rockets and is only used in older and more primitive spacecraft, notably scum barges.
'''Fusion Rocket (F):''' Similar to a plasma rockets, fusion rockets require significantly higher temperatures and pressures, and the rocket also produces large amounts of power for the spacecraft. Fusion rockets are now the most common form of propulsion for spacecraft designed for long-distance voyages.
'''Anti-Matter Rocket (AM):''' Anti-matter rockets work mixing small amounts of anti-matter into the hydrogen fuel, producing enormous amounts of energy and an exceptionally fast and powerful exhaust. These rockets typically carry a heavily shielded magnetically contained anti-matter storage vessel carrying a mass of anti-matter equal to 1% of the mass of the hydrogen fuel used by the rocket. The magnetic containment vessels needed to safely contain antimatter usually weight at least 10 times the mass of the antimatter used.
Though anti-matter storage is exceptionally safe, the vast energy release possible if there was an accident means that anti-matter rockets are forbidden from coming closer than 25,000 km from any inhabited planet or moon. Also, very few habitats will allow an anti-matter rocket to dock with them, and instead require the spacecraft to remain at least 10,000 km away and for all cargo and passengers to be transferred using a small craft like a small LOTV. Anti-matter is exceedingly expensive to produce and so anti-matter rockets are only used in military vessels and in fast couriers designed to carry critical cargoes across the solar system in short periods of time.
{| class="wikitable"
! colspan="2" |Escaping Gravity Wells
|-
|''Spacecraft Engine''
|''Thrust (in Gs)''
|-
|Hydrogen-Oxygen Rocket
|4+
|-
|Metallic Hydrogen
|3
|-
|Plasma Rocket
|0.01
|-
|Fusion Rocket
|0.05
|-
|Antimatter
|0.2
|-
|Rocket Buggy
|0.5
|-
|''Planets, Moons, Etc.''
|''Gravity''
|-
|Earth
|1
|-
|Europa
|0.13
|-
|Jupiter
|2.53
|-
|Luna
|0.17
|-
|Mars
|0.38
|-
|Mercury
|0.38
|-
|Neptune
|1.14
|-
|Pluto
|0.06
|-
|Saturn
|0.91
|-
|Titan
|0.14
|-
|Uranus
|0.89
|-
|Venus
|0.9
|}