Fregat

Fregat (Frigate) is a Russian restartable upper stage developed for use with the Soyuz launch vehicle. Built by the science and production association NPO Lavochkin, it serves as a flexible propulsion and guidance unit that can perform a sequence of engine burns after separation from the launcher to achieve precise orbital injections and complex satellite deployments. The stage is autonomous, containing its own guidance, navigation, and control systems, as well as a thruster-based attitude control system to manage orientation during flight.

The primary role of Fregat is to enable post-separation maneuvers such as orbit insertion, orbit raising, plane changes, and phasing burns that allow multiple satellites to be released into potentially different orbits from a single launch. Its restart capability and autonomous operation provide mission planners with greater flexibility and reliability for diverse payload configurations, including government, commercial, and international satellites.

Fabrication and deployment have supported a broad range of missions on the Soyuz-2 family, with Fregat serving as the standard upper stage on many launches since the early 2000s. Through successive refinements, the Fregat family has evolved to handle more demanding mission profiles and target orbits, while maintaining compatibility with Soyuz launch infrastructure.

See also: Soyuz launch vehicle, NPO Lavochkin, Upper stage, Russian space program.