// PROPULSION SYSTEMS AND ENGINE TECHNOLOGY TERM
Restartable Upper Stage
A restartable upper stage is a section of a rocket, typically equipped with its own engine, that can ignite multiple times once in space. This capability allows it to perform various maneuvers, such as placing multiple satellites into different orbits or traveling to distant destinations.
TECHNICAL DEFINITION
A Restartable Upper Stage is a sophisticated chemical propulsion system integrated into a multi-stage launch vehicle, characterized by its ability to execute multiple in-space engine ignitions. This enables complex orbital maneuvers, precise deployment of diverse payloads into distinct orbital planes, and extended mission profiles essential for satellite constellations, geostationary transfers, and deep-space injection.
BACKGROUND
The Centaur is a family of rocket-propelled upper stages that has been in use since 1962. It is currently produced by United Launch Alliance (ULA) in two main versions. The 3.05 m (10 ft) diameter Centaur III (also known as the Common Centaur) serves as the second stage of the retiring Atlas V rocket, and the 5.4 m (17.7 ft) diameter Centaur V is used as the second stage of the Vulcan Centaur rocket. Centaur was the first rocket stage to use hydrolox propellant—liquid hydrogen (LH2) and liquid oxygen (LOX)—a high-energy combination well suited for upper stages but difficult to handle because both propellants must be stored at extremely low cryogenic temperatures.
READ MORE ON WIKIPEDIASYNONYMS & ALIASES
- Multi-start upper stage
- Multiple ignition stage
- In-space restartable engine
- Restartable stage
- Orbital maneuvering stage
USAGE NOTE
This technology is critical for missions requiring precise orbital adjustments, deploying multiple satellites into different planes, or injecting probes onto interplanetary trajectories after an initial burn.
DEVELOPERS
Organizations developing technology related to Restartable Upper Stage.
SpaceX develops and operates the Falcon 9 and Falcon Heavy rockets, whose Merlin Vacuum engine-powered upper stages are designed for multiple restarts to precisely deliver payloads to various orbits, including direct GEO insertions.
ULA's Centaur upper stage, powered by the Aerojet Rocketdyne RL10 engine, is renowned for its multi-restart capability, enabling complex mission profiles for Atlas V and the upcoming Vulcan Centaur launch vehicles.
ArianeGroup develops the Ariane 6 launcher for ESA, featuring the Vinci engine on its upper stage. The Vinci engine is specifically designed for multiple restarts and extended mission durations for complex satellite deployments.
Rocket Lab's Electron launch vehicle utilizes a 'Kick Stage' equipped with the 3D-printed Curie engine, which is capable of multiple restarts to deliver small satellites to precise, unique orbits and conduct in-space maneuvers.
Blue Origin is developing the New Glenn heavy-lift orbital launch vehicle. Its upper stage will be powered by the BE-3U engine, designed with restart capability for complex orbital deployments and space exploration missions.
Aerojet Rocketdyne is a leading developer of advanced propulsion systems, including the RL10 engine family, which powers restartable upper stages on numerous launch vehicles such as ULA's Atlas V and Vulcan Centaur.
Roscosmos, through entities like the Lavochkin Association, develops and operates the Fregat upper stage, widely used with Soyuz rockets. Fregat is renowned for its high reliability and multi-restart capability, allowing for intricate orbital maneuvers and deployment sequences.
MHI, in collaboration with JAXA, develops and operates the H3 launch vehicle. Its second stage employs the LE-5B-2 and LE-9 engines, designed with restart capabilities to facilitate flexible payload deployment and complex orbital missions.