Proton-K

Did You Know?

• The Proton-K's first stage guidance system was open-loop, requiring significant propellant reserves.
• The rocket's propellants are hypergolic, igniting on contact without an ignition system.

Vehicle description

The baseline Proton-K was a three-stage rocket, with thirty launches in this configuration. It carried all of the Soviet Union's Salyut space stations, all Mir modules except the Docking Module (launched on the US Space Shuttle), and the Zarya and Zvezda modules of the International Space Station. It was intended for Chelomey's crewed TKS spacecraft, launching four uncrewed test flights before cancellation, and for the unrealised 20-ton LKS spaceplane. Like other Universal Rocket family members, it used hypergolic propellants—unsymmetrical dimethylhydrazine and nitrogen tetroxide—which ignite on contact, can be stored at ambient temperatures, and avoid cryogenic boil-off, though they are corrosive and toxic. The Russian Government paid for cleanup of residual propellant in spent stages. Components were built near Moscow and railed to the pad. The first stage had a central oxidiser tank and six outrigger fuel tanks, separating as one piece from the second stage via a lattice interstage. The second stage ignited before first-stage separation, with the first stage's top insulated for structural integrity. The first stage used six RD-253 engines, designed by Valentin Glushko, each a single-chamber engine with staged combustion cycle and open-loop guidance requiring reserve propellant. The third stage used an RD-0210 engine and four vernier nozzles for steering, stage separation, and ullage, with ducts channelling vernier exhaust before separation; its guidance system also controlled the first and second stages.