RP-1 (rocket propellant 1)
RP-1 (rocket propellant 1) is a highly-refined, special grade of kerosene used in a wide variety of rocket engines. Together with liquid oxygen, it provides, or has provided, the propellant for the first stages of rockets such as the Atlas, Thor, Delta, Titan I, and Saturn 1B and V.
RP-1's formulation stemmed from a program begun in 1953 by Rocketdyne to improve the engines being developed for the Navaho and Atlas missiles. Prior to that a large number of petroleum-based rocket propellants had been used. Robert Goddard had begun with gasoline, and other experimental engines had been powered by kerosene, diesel oil, paint thinner, and jet-fuel kerosene. The wide variation in physical properties among fuels of the same class led to the identification of narrow-range petroleum fractions, embodied in 1954 in the standard United States kerosene rocket fuel RP-1, covered by Military Specification MIL-R-25576. In Russia, similar specifications were developed for kerosene under the specifications T-1 and RG-1. RP-1 is a kerosene fraction, obtained from crude oil with a high napthene content which is subjected to further treatment, including acid washing and sulfur dioxide extraction.