Rocket researchers investigating space flight in the 1920s and 1930s knew that old-fashioned fireworks rockets weren’t really the way of the future for their work, and turned instead to liquid propellants to build the large rocket vehicles they wanted. By the mid-1960s, they had developed liquid-propellant rocket engines powerful enough to put men on...
The US space shuttle’s orbital propulsion system uses storables, and when the orbiter lands a crew in protective clothing has to go out and “safe” it before anyone else is allowed to get near. The nasty behaviour of storables means higher cost, and they are also now generally regarded as environmentally unacceptable and avoided...
In addition to the normal tripropellant approach, researchers have been looking at chemical additives that will increase the specific impulse generated by conventional bipropellant systems. These increases are achieved by adding high-energy chemicals in order to increase Isp, thrust, and safety. This is not unlike adding chemicals to your car’s fuel tank in order...
There are many chemical reactions that result in a higher specific impulse than the 423 seconds that is provided by the LH2/LOX workhorse. However, many of these are unacceptable as rocket propellants because the exhaust is not a gas. Tripropellant technologies are an attempt to use these reactions by adding a third component (usually...
The bipropellant that is most often used in interplanetary spacecraft with relatively small engines is nitrogen tetroxide / monomethyl-hydrazine, commonly referred to as NTO/MMH. This combination yields an Isp of 317 lbf-s/lbm. NASA seeks to improve performance to 326 lbf-s/lbm by using of a rhenium-alloyed thrust chamber, which will allow both higher operating temperatures...
A wide range of different liquid propellant combinations have been used for liquid rocket engines, and many combinations are possible. Unusual fuels include ammonia and ethanol (grain alcohol), and there have been some odd combinations of more conventional propellants, such as LOX-UDMH or HTP-RP. Liquid diatomic fluorine (LF2) has been considered as an oxidizer...
The most common monopropellant in use is hydrazine. It is passes through a catalyst bed, where it decomposes into nitrogen and ammonia and delivers a specific impulse of about 230 lbf-s/lbm. Propulsion systems of this sort are well suited to pulsed operations of short duration, such as small spacecraft attitude control. (Adams, 1994) NASA...
Since we have already developed many different types of chemically-fueled propulsion systems, one might wonder why we need to advance these technologies. Historically, there has been a demand for improvements in many areas, such as safety, reduced mass, and of course increased specific impulse (Isp). Modern chemical propulsion systems utilize from one to three...