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RS-25 Engine

Overview

Four RS-25 engines located at the bottom of the core stage 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 and SLS programs, the RS-25 and SSME engines have collectively compiled more than 1.1 million seconds of firing time.

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 of vacuum thrust (104.5-percent of rated power level). The required power level for the RS-25 engines on SLS is 512,000 pounds vacuum thrust (109 percent of rated power level). Future evolutions will have even higher thrust capabilities.

Aerojet Rocketdyne, a segment of L3Harris Technologies, 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

PropellantsFuel: Liquid hydrogen
Oxidizer: Liquid Oxygen
Mixture Ratio (O/F): 6.0
Thrust
(109% Power Level)
Vacuum: 512,300 lb.
Sea Level: 418,000 lb.
Chamber Pressure: 2,994 psia
Specific Impulse
(109% Power Level)
Vacuum: 452 sec.
Sea Level: 366 sec.
DimensionsLength: 168 in.
Diameter: 96 in.
Weight: 7,775 lb.
Area Ratio: 69:1

Resources

  • RS-25 Propulsion System Data Sheet

    RS-25 Propulsion System Data Sheet

  • Rs-25 Incredible Facts

    RS-25 Incredible Facts

Featured News

Aerojet Rocketdyne Races to the Moon with High-Performance RS-25 Engines

Editorial | 10. 20. 2023

Aerojet Rocketdyne Races to the Moon with High-Performance RS-25 Engines

Aerojet Rocketdyne Races to the Moon with High-Performance RS-25 Engines

Aerojet Rocketdyne Races to the Moon with High-Performance RS-25 Engines

Editorial | 10. 20. 2023

Aerojet Rocketdyne Races to the Moon with High-Performance RS-25 Engines

Image for Artemis II Editorial 092223

Editorial | 09. 25. 2023

RS-25 Engines with Different Histories Will Share Common Future on Artemis II

Aerojet Rocketdyne, an L3Harris Company

Press release | 07. 28. 2023

L3Harris Completes Aerojet Rocketdyne Acquisition

Engines 2057 and 2054 are two of the four engines that will fly on NASA’s Artemis III mission. All four RS-25 engines that will power NASA’s Space Launch System for the Artemis III mission are ready to fly and awaiting integration at Aerojet Rocketdyne’s facility located at NASA’s Stennis Space Center

Press release | 04. 18. 2023

Aerojet Rocketdyne Delivers Propulsion for Artemis III Mission

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