RS-25 Engine

Overview
Key Features
Resources
Related

Powering Deep Space Exploration

Aerojet Rocketdyne is the prime contractor for the flight proven, high-performance RS-25 engines used to propel America’s next-generation heavy lift launch vehicle, NASA’s Space Launch System (SLS). Four RS-25 engines located at the bottom of the core stage will power the rocket on its eight and a half minute climb to space with more than 2 million pounds of thrust.

Key Features

The RS-25 evolved from Aerojet Rocketdyne’s Space Shuttle Main Engine (SSME) that successfully powered 135 flights of the Space Shuttle. The engine underwent five major upgrades during its life on Shuttle, each time incorporating the modern technologies and innovations – and each time demonstrating major improvements in safety and reliability. Between the shuttle program and the SLS program, the RS-25 and SSME engines have collectively experienced more than 1.1 million seconds of use.

The RS-25 is a staged-combustion engine cycle powered by liquid hydrogen and liquid oxygen, making it one of highest performing engines the nation has ever produced. The SSME engines on the Shuttle typically operated at 491,000 pounds vacuum thrust (104.5-percent of rated power level). The required power level for the RS-25 engines that will fly on the SLS is 512,000 pounds vacuum thrust (109 percent of rated power level) to augment the vehicle's heavy lift capability. Future evolutions will have even higher thrust capabilities.

Aerojet Rocketdyne has begun developing a new generation of RS-25 engines for when the 16 engines remaining from the Space Shuttle program are used. These engines are targeting a 30% cost reduction from the engines that flew on the Space Shuttle and will feature the latest in advanced manufacturing techniques, including 3-D printing.

Engine Specifications

Propellants

Thrust
(109% Power Level)

Specific Impulse
(109% Power Level)

Dimensions

Fuel: Liquid hydrogen
Oxidizer: Liquid Oxygen
Mixture Ratio (O/F): 6.0

Vacuum: 512,300 lb.
Sea Level: 418,000 lb.
Chamber Pressure: 2,994 psia

Vacuum: 452 sec.
Sea Level: 366 sec.

Length: 168 in.
Diameter: 96 in.
Weight: 7,775 lb.
Area Ratio: 69:1

Resources

Videos




Press Releases

RS-25 engine inspection inside the engine assembly room at Aerojet Rocketdyne's Stennis Space Center Facility (August 2015).
RS-25 development engine 0525 in the A-1 test stand at NASA's Stennis Space Center in Mississippi (August 2015).
Technicians inspect the RS-25 controller (provides for comm between the SLS vehicle & the engine, relays commands to the engine, transmits data back to the SLS vehicle to regulate thrust & fuel mixture ratio & monitor the engine's health & status). 8/15
June 28, 2019 - Aerojet Rocketdyne delivered four RS-25 engines for integration with NASA’s Space Launch System core stage from its facility at NASA’s Stennis Space Center to NASA’s Michoud Assembly Facility
Nov. 6, 2019 - Four RS-25 engines attached to the core Stage for NASA’s Space Launch System rocket for NASA’s Artemis I mission to the Moon. Image courtesy of NASA.
NASA conducts a hot fire test Jan. 16, 2021, of the core stage for the agency’s Space Launch System rocket on the B-2 Test Stand at Stennis Space Center near Bay St. Louis. Credit: NASA
NASA conducts a hot fire test Jan. 16, 2021, of the core stage for the agency’s Space Launch System rocket on the B-2 Test Stand at Stennis Space Center near Bay St. Louis. Credit: NASA
The core stage for the first flight of NASA’s SLS rocket is seen in the B-2 Test Stand during a scheduled eight minute duration hot fire test, Saturday, Jan. 16, 2021, at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. Credit: NASA

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