RL10 Engine

Nearly six decades of reliably powering space exploration and national security

For nearly 60 years, Aerojet Rocketdyne’s RL10 engine has played a vital role in placing hundreds of military, government and commercial spacecraft into Earth’s orbit and beyond. The engine has helped send spacecraft to explore every planet in our solar system, including Voyager 1 and Voyager 2, the first spacecraft to reach interstellar space.

Today, multiple variants carry the RL10’s legacy forward as the launch industry’s “workhorse,” powering the upper stages of United Launch Alliance’s (ULA) Atlas V and Delta IV Heavy rockets. Two RL10 engines power the upper stage of ULA’s new Vulcan Centaur rocket.

RL10 engines also help power NASA’s Space Launch System (SLS) rocket, designed to carry astronauts to deep-space destinations aboard the Orion exploration spacecraft. A single RL10 powered the Interim Cryogenic Propulsion Stage on Artemis I, an un-crewed test flight of SLS and Orion. Four RL10 engines will support the more powerful Exploration Upper Stage that is being developed for future versions of SLS.

Aerojet Rocketdyne has developed and is working to qualify a modern version of the engine known as the RL10C-X that includes major components built using 3-D printing technology. Incorporating 3D printing into the manufacturing process will reduce lead times and cost while maintaining the outstanding performance and reliability customers have come to expect.

Key Features

Program Milestones

1959 First RL10 test
1963 First successful Atlas Centaur flight (two RL10 engines powered upper stage)
1964 Saturn S-4 Launch (six RL10 engines powered upper stage)
1993 First DC-X "Delta Clipper" flight (four RL10A-5 engines powered vehicle)
2002 First Atlas V flight (two RL10A-4-2 engines powered Centaur upper stage)
2009 400th RL10 engine flight
2010 Demonstrated deep-throttling from 104 percent of rated power down to 5.9 percent (an unprecedented thrust range of 17.6:1)
2013 RL10 marks 50 years of service
2014 First flight of RL10C-1
2020 500th RL10 engine flight
2021 First operational use of an RL10 engine equipped with 3D-printed components
2022 A single RL10 powered the Interim Cryogenic Propulsion Stage on the first SLS mission

Specifications

RL10 Model	RL10B-2 RL10C-2-1	RL10A-4-2	RL10C-1	RL10C-1-1	RL10C-X	RL10C-3
Launch Vehicle:	Delta IV	Atlas V	Atlas V	Atlas V, Vulcan Centaur	Vulcan Centaur	SLS Exploration Upper Stage
Thrust:	24,750 lbf	22,300 lbf	22,890 lbf	23,825 lbf	24,120 lbf	24,340 lbf
Weight:	664 lbs	370 lbs	420 lbs	415 lbs	510 lbs	508 lbs
Fuel:	Liquid hydrogen	Liquid hydrogen	Liquid hydrogen	Liquid hydrogen	Liquid hydrogen	Liquid hydrogen
Oxidizer:	Liquid oxygen	Liquid oxygen	Liquid oxygen	Liquid oxygen	Liquid oxygen	Liquid oxygen
Nominal Mixture Ratio:	5.88:1	5.5:1	5.5:1	5.5:1	5.5:1	5.7:1
Specific Impulse:	465.5 sec	451.0 sec	449.7 sec	453.8 sec	460.9 sec	460.1 sec
Length:	86.5" (stowed) 163.5" (deployed)	90"	86"	96.7"	130.4"	124.3"
Nozzle Diameter:	84.5"	46"	57"	62"	73.7"	73"