RL10


The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to of thrust per engine in vacuum. RL10 versions were produced for the Centaur upper stage of the Atlas V and the DCSS of the Delta IV. More versions are in development or in use for the Exploration Upper Stage of the Space Launch System and the Centaur V of the Vulcan rocket.
The expander cycle that the engine uses drives the turbopump with waste heat absorbed by the engine combustion chamber, throat, and nozzle. This, combined with the hydrogen fuel, leads to very high specific impulses in the range of in a vacuum. Mass ranges from depending on the version of the engine.

History

The RL10 was the first liquid hydrogen rocket engine to be built in the United States, with development of the engine by Marshall Space Flight Center and Pratt & Whitney beginning in the 1950s. The RL10 was originally developed as a throttleable engine for the USAF Lunex lunar lander. The engine was electric spark ignited.
The RL10 was first tested on the ground in 1959, at Pratt & Whitney's Florida Research and Development Center in West Palm Beach, Florida. The first successful flight took place on November 27, 1963. For that launch, two RL10A-3 engines powered the Centaur upper stage of an Atlas launch vehicle. The launch was used to conduct a heavily instrumented performance and structural integrity test of the vehicle.Multiple versions of this engine have been flown. The S-IV of the Saturn I used a cluster of six RL10A-3S, a version which was modified for installation on the Saturn and the Titan program included Centaur D-1T upper stages powered by two RL10A-3-3 Engines.
Four modified RL10A-5 engines were used in the McDonnell Douglas DC-X.
A flaw in the brazing of an RL10B-2 combustion chamber was identified as the cause of failure for the 4 May 1999 Delta III launch carrying the Orion-3 communications satellite.
The DIRECT version 3.0 proposal to replace Ares I and Ares V with a family of rockets sharing a common core stage recommended the RL10 for the second stage of the J-246 and J-247 launch vehicles. Up to seven RL10 engines would have been used in the proposed Jupiter Upper Stage, serving an equivalent role to the Space Launch System Exploration Upper Stage.

Common Extensible Cryogenic Engine

In the early 2000s, NASA contracted with Pratt & Whitney Rocketdyne to develop
the Common Extensible Cryogenic Engine demonstrator. CECE was intended to lead to RL10 engines capable of deep throttling. In 2007, its operability was demonstrated at 11:1 throttle ratios. In 2009, NASA reported successfully throttling from 104 percent thrust to eight percent thrust, a record for an expander cycle engine of this type. Chugging was eliminated by injector and propellant feed system modifications that control the pressure, temperature and flow of propellants. In 2010, the throttling range was expanded further to a 17.6:1 ratio, throttling from 104% to 5.9% power.

Early 2010s possible successor

In 2012 NASA joined with the US Air Force to study next-generation upper stage propulsion, formalizing the agencies' joint interests in a new upper stage engine to replace the Aerojet Rocketdyne RL10.
From the study, NASA hoped to find a less expensive RL10-class engine for the upper stage of the Space Launch System.
USAF hoped to replace the Rocketdyne RL10 engines used on the upper stages of the Lockheed Martin Atlas V and the Boeing Delta IV Evolved Expendable Launch Vehicles that were the primary methods of putting US government satellites into space. A related requirements study was conducted at the same time under the Affordable Upper Stage Engine Program.

Improvements

The RL10 has undergone multiple upgrades over the decades. The RL10B-2, used on the DCSS, incorporated an extendable nozzle made from carbon–carbon, electro-mechanical gimbaling to reduce weight and increase reliability, and achieved a specific impulse of.
Beginning in the 2000s, Aerojet Rocketdyne introduced 3D printing into RL10 production. The RL10C-1-1 was the first engine to include a 3D-printed component, featuring a nickel superalloy main injector. Building on that experience, in 2015 the company began developing a more extensive upgrade that employed an additively manufactured copper thrust chamber. According to the company, the new process reduced chamber fabrication time from approximately 20 months to 4–6 months compared with earlier hand-fabricated stainless steel chambers, enabling production of up to one engine per week rather than one per month. This variant, designated RL10C-X during development, entered production as the RL10E-1 and is planned for use on United Launch Alliance’s Vulcan Centaur rocket, scheduled for its first flight in 2025.

Applications

Current

In development

Cancelled

Table of versions

VersionStatusFirst flightDry massThrustSpecific impulse, LengthNozzle diameterT:WExpansion ratioBurn timeAssociated stageNotes
196252:15:140:1430 sCentaur APrototype
196351:15:157:1470 sCentaur B/C/D/E
196451:15:140:1482 sS-IV
199256:15.5:184:1392 sCentaur IIA
199346:16:14:1127 sDC-X
1998Stowed:
Deployed: 		40:15.88:1280:15m: 1,125 s
4m: 700 s		DCSS
ICPS		Succeeded by RL10C-2.
200061:184:1740 sCentaur IIIA
200261:184:1740 sCentaur IIIB
Centaur SEC
Centaur DEC		Used for Starliner launches.
30:1250:1408 sCentaur B-X
CECE, throttle to 5–10%>43:1
201457:15.5:1130:1Centaur SEC
Centaur DEC		Succeeded by RL-10C-1-1.
202157:15.5:1155:1Atlas: 842 s
Vulcan: 1,077 s		Centaur SEC
Centaur V		Current standard engine for Atlas V and Vulcan Centaur.
2022Stowed:
Deployed: 		37:15.88:1280:1DCSS
2026 Stowed:
Deployed: 		2.15 m 37:15.88:1280:1ICPSConversion of C-3
2028 48:15.7:1215:1EUS
2.46 m 1.57 m 57:15.5:1OmegA
2025 47.29:15.5:1Centaur VAdditive manufacturing

Engines on display