The engine produced 15.83 kilonewtons (3,560 lbf) of thrust with a specific impulse of 266 seconds in vacuum, and burned for 45 seconds, enough for the deorbit. It had a main fixed combustion chamber and four small verniers to supply vector control. It was housed in the service module and had two toroidal tanks for pressurization.[5][6][7]
It was designed by OKB-2, the Design Bureau led by Aleksei Isaev, for the Vostok program. The braking engine for the first crewed spacecraft was a difficult task that no design bureau wanted to take.[citation needed] It was considered critical, as a failure would have left a cosmonaut stranded in space. A solid motor was considered, but the ballistic experts predicted a 500-kilometer (270-nautical-mile) landing error, versus a tenth of that for a liquid engine. It took the coordinated efforts of Boris Chertok and Sergei Korolev to convince Isaev to accept the task.[8]