RD-550

Glushko exotic rocket engine. Experimental upper stage engine. Developed 1963-70. Propellants LOx/30% Beryllium+Pentaborane in 70% Hydrazine.

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.