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In rocketry, the only reaction mass is the propellant, so the specific impulse is calculated using an alternative method, giving results with units of seconds. Specific impulse is defined as the thrust integrated over time per unit weight-on-Earth of the propellant: [9] =, where
Solid fuel rockets have lower specific impulse, a measure of propellant efficiency, than liquid fuel rockets. As a result, the overall performance of solid upper stages is less than liquid stages even though the solid mass ratios are usually in the .91 to .93 range, as good as or better than most liquid propellant upper stages.
As noted the specific impulse of monopropellants is lower [3] [15] than bipropellants and can be found with the Air Force Chemical Equilibrium Specific Impulse Code tool. [16] One newer monopropellant under development is nitrous oxide, both neat and in the form of nitrous oxide fuel blends.
Other propellants of interest include argon, bismuth, iodine, magnesium, zinc and adamantane. Hall thrusters are able to accelerate their exhaust to speeds between 10 and 80 km/s (1,000–8,000 s specific impulse), with most models operating between 15 and 30 km/s. The thrust produced depends on the power level.
Ammonium perchlorate composite propellant (APCP) is a solid rocket propellant. It differs from many traditional solid rocket propellants such as black powder or zinc-sulfur , not only in chemical composition and overall performance but also by being cast into shape, as opposed to powder pressing as with black powder.
Specific impulse (usually abbreviated I sp) is a measure of how effectively a rocket uses propellant or jet engine uses fuel. By definition, it is the total impulse (or change in momentum) delivered per unit of propellant consumed [4] and is dimensionally equivalent to the generated thrust divided by the propellant mass flow rate or weight flow rate. [5]
The Soviet Union fielded its first solid-fuel ICBM, the RT-2, in the early 1970s, followed by France's development of its S3, also known as SSBS, a medium-range ballistic missile. China started ...
the term in brackets is known as equivalent velocity, = ˙. The specific impulse is the ratio of the thrust produced to the weight flow of the propellants. It is a measure of the fuel efficiency of a rocket engine. In English Engineering units it can be obtained as [7]