R-Stoff

Tonka (also TONKA-250 and R-Stoff) is the name given to a German-designed rocket propellant first used in the Wasserfall missile; it has also more recently been used by North Korea but found its greatest applications (under the name TG-02) in the Soviet Union, for example, in the propulsion projects of the A.M. Isayev Chemical Engineering Design Bureau.

Its name is a reference to the tonka bean; as it was invented during the Second World War, it has no connection to the similarly named toys.

Its composition is approximately 50% triethylamine and 50% xylidine, with the most common oxidizer used to burn it, nitric acid or its anhydrous nitric oxide derivatives(classified as the AK-2x family in the Soviet Union). In a similar manner to the chemically related nitric acid /aniline(Benzamine) propellant combination used in the USA's first indigenous sounding rockets, the WAC Corporal and Aerobee, this fuel-oxidizer combination is likewise hypergolic(spontaneously ignites upon mixing, with little delay). The combination has a maximum practical Isp of approximately 216-248 at sea level, with the latter figure stated as a specification for the R-21 (missile)(The Soviet Union's first Submarine Launched Ballistic Missile) which was first fielded in 1963.

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