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RD-253 engine series for Proton's first stage The original first stage of the Proton rocket was propelled by six RD-253 engines developed at OKB-456 design bureau (now NPO Energomash) in Moscow and led by Valentin Glushko. Each engine had a thrust on the ground of 150 tons. Like the engines on two upper stages of the Proton rocket, RD-253 burned highly toxic unsymmetrical dimethylhydrazine as a fuel mixed with nitrogen tetroxide as an oxidizer.
A full-scale demo version of the RD-253 engine. Specifications of RD-253 engine:
On the first stage of the Proton rocket, RD-253 was installed in a movable suspension system that allowed to swivel each individual engine around a single axis. Combined movement of all six engines enabled the flight control system of the rocket to steer the vehicle along its prescribed trajectory. In 1986, specifically for the launch of core module of the Mir space station, the thrust of RD-253 engine was increased by seven percent. It was achived thanks to a minor modification to the propellant flow control valves. Since then, engines incorporating this change have undergone extensive additional qualification firings, in order to approve them for use in standard production vehicles. From 1987 to 1993, NPO Energomash developed a more powerful version of the engine, designated RD-275, which has been used on the first stage of the Proton rocket until 2007, when the improved RD-276 model was introduced. The engines were mass produced at PPO Motorostroitel (also known as Permskie Motory or PAO Proton-MP) in the city of Perm. During a visit to Perm of Roskosmos haed Dmitry Rogozin, a poster on wall of the Proton PM exhibit hall indicated that the production of the engines at the company was first set up in 1962, of three years before the first launch of the Proton rocket.
An engine from the RD-253 series in production circa 2016. As late as 2017, Proton's first stage engines still used non-Russian components, most likely produced in Ukraine, and NPO Energomash promised to certify Russian-built replacements in 2018. In September 2018, Acting Director at PAO Proton PM Dmitry Shenyatsky, quoted by RIA Novosti, said that four final RD-276 engines would be produced and tested by the company in the first quarter of 2019. However, the final test was actually conducted on November 14, 2019, Roskosmos announced. According to the State Corporation, Proton PM manufactured more than 90 sets of the RD-276 variants and conducted around 770 firing tests. According to industry sources, by that time, 77 sets of engines flew on Protons and more than 13 sets still remained for future launches. In total, the company had produced more than 3,000 engines for different variants of the rocket, Roskosmos said. In the December 2019 issue of the company's newspaper, Proton PM confirmed that the production of the RD-276 engines had been finished and one engine in the final pair had been transferred to GKNPTs Khrunichev in November 2019. One more was apparently shipped in early 2020. In April 2021, Head of NPO Energomash Igor Arbuzov said that the RD-276 production line in Perm had been mothballed in operational readiness, however, there had been no decision to resume their production at the time.
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