Monopropellant rocket
The attitude control rocket motors for satellites and space probes are often very small, 25 mm (0.98 in) or so in diameter, and mounted in groups that point in four directions (within a plane).
If the propulsion system must produce large amounts of thrust, or have a high specific impulse, as on the main motor of an interplanetary spacecraft, other technologies are used.
A concept to provide low Earth orbit (LEO) propellant depots that could be used as way-stations for other spacecraft to stop and refuel on the way to beyond-LEO missions has proposed that waste gaseous hydrogen—an inevitable byproduct of long-term liquid hydrogen storage in the radiative heat environment of space—would be usable as a monopropellant in a solar-thermal propulsion system.
[6] Solar-thermal monopropellant thrusters are also integral to the design of a next-generation cryogenic upper stage rocket proposed by U.S. company United Launch Alliance (ULA).
The ACES Integrated Vehicle Fluids option eliminates all hydrazine and helium from the space vehicle—normally used for attitude control and station keeping—and depends instead on solar-thermal monopropellant thrusters using waste hydrogen.
[9] Although his initial work was on submarine propulsion the same jets of oxygen produced by for combustion in gas turbines could be directed through a nozzle to generate thrust.
Not intended for space flight the rocket would provide hot and high takeoff capability to the de Havilland Comet 1 the first commercial jet airliner.
[9] In the United States, when NASA began studying monopropellants at the Jet Propulsion Laboratory (JPL) the properties of the existing propellants demanded that the thrusters be impractically large.
This system is based on a hydroxylammonium nitrate (HAN)/water/fuel monopropellant blend which is extremely dense, environmentally benign, and promises good performance and simplicity.
[16] The EURENCO Bofors company produced LMP-103S as a 1-to-1 substitute for hydrazine by dissolving 65% ammonium dinitramide, NH4N(NO2)2, in 35% water solution of methanol and ammonia.
