Engine Model: RD-550. Manufacturer Name: RD-550. Designer: Glushko. Developed in: 1963-70. Application: experimental upper stage engine. Propellants: Lox/30% Beryllium+Pentaborane in 70% Hydrazine. Thrust(vac): 98.060 kN (22,045 lbf). Isp: 400 sec. Chambers: 1. Country: Russia. Status: Developed 1963-70. Toxic exotic propellant engine studied by Glushko in 1963-1970. The specific impulse would have been between 360 and 400 seconds. This was one of the category B engines that had to be developed by OKB-456 Filial 1 because test of the extremely toxic propellants was impossible at Khimki. The notes to Korolev's memoirs report a different propellant combination was considered in 1963, in the earliest design stage of the engine: H2O2/Hydrazine with 30% beryllium additive only.
Bibliography:- Vetrov, G S, S. P. Korolev i evo delo, Nauka, Moscow, 1998.