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 Template:Convert 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.<ref name="Aerojet Rocketdyne 2" />

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 (I_sp) in the range of Template:Convert in a vacuum. Mass ranges from Template:Convert depending on the version of the engine.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref>Template:Cite encyclopedia</ref>

The RL10 was first tested on the ground in 1959, at Pratt & Whitney's Florida Research and Development Center in West Palm Beach, Florida.<ref>Connors, p 319</ref><ref name="gunter.centaur">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The first successful flight took place on November 27, 1963.<ref name="Sutton 2005">Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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<ref name="Norbert">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and the Titan program included Centaur D-1T upper stages powered by two RL10A-3-3 Engines.<ref name="Norbert" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Four modified RL10A-5 engines were used in the McDonnell Douglas DC-X.<ref name="astro-dcx">Template:Cite encyclopedia</ref>

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref name="direct_v3_specs">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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

File:Common Extensible Cryogenic Engine.jpg

The CECE at partial throttle

In the early 2000s, NASA contracted with Pratt & Whitney Rocketdyne to develop the Common Extensible Cryogenic Engine (CECE) demonstrator. CECE was intended to lead to RL10 engines capable of deep throttling.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In 2007, its operability (with some "chugging") was demonstrated at 11:1 throttle ratios.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In 2010, the throttling range was expanded further to a 17.6:1 ratio, throttling from 104% to 5.9% power.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Early 2010s possible successor

In 2012 NASA joined with the US Air Force (USAF) to study next-generation upper stage propulsion, formalizing the agencies' joint interests in a new upper stage engine to replace the Aerojet Rocketdyne RL10.

"We know the list price on an RL10. If you look at cost over time, a very large portion of the unit cost of the EELVs is attributable to the propulsion systems, and the RL10 is a very old engine, and there's a lot of craftwork associated with its manufacture. ... That's what this study will figure out, is it worthwhile to build an RL10 replacement?" {{#if:Dale Thomas, Associated Director Technical, Marshall Space Flight Center<ref name=FG2012/>|{{#if:|}}

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From the study, NASA hoped to find a less expensive RL10-class engine for the upper stage of the Space Launch System (SLS).<ref name=FG2012/><ref name=NASA-2012-04/>

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 (EELV) that were the primary methods of putting US government satellites into space.<ref name="FG2012">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A related requirements study was conducted at the same time under the Affordable Upper Stage Engine Program (AUSEP).<ref name="NASA-2012-04">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Improvements

The RL10 has evolved over the years. The RL10B-2 that was used on the DCSS had improved performance, an extendable carbon-carbon nozzle, electro-mechanical gimbaling for reduced weight and increased reliability, and a specific impulse of Template:Convert.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=pwr_rl10b-2.pdf/>

As of 2016, Aerojet Rocketdyne was working toward incorporating additive manufacturing into the RL10 construction process. The company conducted full-scale, hot-fire tests on an engine that had a printed main injector in March 2016.<ref>Template:Cite press release</ref> Another project by Aerojet Rocketdyne was an engine with a printed thrust chamber assembly in April 2017.<ref>Template:Cite press release</ref>

Applications

Current

• Centaur III: The single engine centaur (SEC) version uses the RL10C-1,<ref name="Aerojet Rocketdyne 2" /> while the dual engine centaur (DEC) version retains the smaller RL10A-4-2.<ref name="EA10A1" /> An Atlas V mission (SBIRS-5) marked the first use of the RL10C-1-1 version. The mission was successful but observed unexpected vibration, and further use of the RL10C-1-1 model is on hold until the problem is better understood.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> The engine was used again successfully on SBIRS-6.

• Centaur V stage: On May 11, 2018, United Launch Alliance (ULA) announced that the RL10 upper stage engine had been selected for its Vulcan Centaur rocket following a competitive procurement process.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> Early versions of the Centaur V will use the RL10C-1-1,<ref name="Aerojet Rocketdyne 2" /> but later versions will transition to the RL10C-X.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Vulcan flew its successful maiden flight on January 8, 2024.<ref>Template:Cite news</ref>

• Interim Cryogenic Propulsion Stage: The Interim Cryogenic Propulsion Stage or ICPS is used for the SLS and is similar to the DCSS, except that the engine is an RL10B-2 and it is adapted to fit on top of the 8.4 meter diameter core stage with four RS-25 Space Shuttle Main Engines.

In development

• Exploration Upper Stage: The Exploration Upper Stage will use four RL10C-3 engines.<ref>Template:Cite news</ref>

Cancelled

• OmegA Upper Stage: In April 2018, Northrop Grumman Innovation Systems announced that two RL10C-5-1 engines would be used on OmegA in the upper stage.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> Blue Origin's BE-3U and Airbus Safran's Vinci were also considered before Aerojet Rocketdyne's engine was selected. OmegA development was halted after it failed to win a National Security Space Launch contract.<ref name="SpaceNews 2020">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

• Advanced Cryogenic Evolved Stage: Template:As of, an enhanced version of the RL10 was proposed to power the Advanced Cryogenic Evolved Stage (ACES), a long-duration, low-boiloff extension of existing ULA Centaur and Delta Cryogenic Second Stage (DCSS) technology for the Vulcan launch vehicle.<ref name="aiaa20096566">Template:Cite journal</ref> Long-duration ACES technology is intended to support geosynchronous, cislunar, and interplanetary missions. Another possible application is as in-space propellant depots in LEO or at Template:L2 that could be used as way-stations for other rockets to stop and refuel on the way to beyond-LEO or interplanetary missions. Cleanup of space debris was also proposed.<ref name="aiaa20100902">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

Table of versions

Version	Status	First flight	Dry mass	Thrust	Isp (ve), Template:Abbr	Length	Nozzle diameter	T:W	Template:Abbr	Expansion ratio	Chamber pressure	Burn time	Associated stage	Notes
Template:Nowrap	Retired	1962	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	52:1	5:1	40:1	Template:Cvt	430 s	Centaur A	Prototype <ref name="Norbert" /><ref name="EA10A1">Template:Cite encyclopedia</ref><ref name="S2S" /><ref name="GSPAC">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
Template:Nowrap	Retired	1963	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	51:1	5:1	57:1	Template:Cvt	470 s	Centaur B/C/D/E	<ref name="EA10A3">Template:Cite encyclopedia</ref>
Template:Nowrap	Retired	1964	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt		51:1	5:1	40:1	Template:Cvt		S-IV	<ref name="Norbert" /><ref name="Sutton 2005" />
Template:Nowrap	Retired	1992	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	56:1	5.5:1	84:1	Template:Cvt	392 s	Centaur IIA	<ref name="Norbert" /><ref name="EA10A4">Template:Cite encyclopedia</ref>
Template:Nowrap	Retired	1993	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	46:1	6:1	4:1	Template:Cvt	127 s	DC-X	<ref name="Norbert" /><ref name="EA10A5">Template:Cite encyclopedia</ref>
Template:Nowrap	Retired	1998	Template:Cvt	Template:Convert	Template:Convert	Stowed: Template:Cvt Deployed: Template:Cvt	Template:Cvt	40:1	5.88:1	280:1	Template:Cvt	5m: 1,125 s 4m: 700 s	DCSS ICPS	Succeeded by RL10C-2.<ref name="EA10B2">Template:Cite encyclopedia</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
Template:Nowrap	Retired	2000	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	Template:Cvt	61:1		84:1	Template:Cvt	740 s	Centaur IIIA	<ref name="Norbert" /><ref name="EA10A41">Template:Cite encyclopedia</ref>
Template:Nowrap	Active	2002	Template:Cvt	Template:Convert	Template:Convert	Template:Cvt	Template:Cvt	61:1		84:1	Template:Cvt	740 s	Centaur IIIB Centaur SEC Centaur DEC	Used for Starliner launches.<ref name="Norbert" /><ref name="EA10A42">Template:Cite encyclopedia</ref><ref name="Aerojet Rocketdyne" />
Template:Nowrap	Cancelled	Template:N/a	Template:Cvt	Template:Cvt	Template:Cvt		Template:Cvt	30:1		250:1		408 s	Centaur B-X	<ref name="EA10BX">Template:Cite encyclopedia</ref>
CECE	Demonstrator project	Template:N/a	Template:Cvt	Template:Cvt, throttle to 5–10%	>Template:Cvt	Template:Cvt		43:1					N/A	citation	CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
Template:Nowrap	Retired	2014	Template:Cvt	Template:Convert	Template:Convert	Template:Cvt	Template:Cvt	57:1	5.5:1	130:1			Centaur SEC Centaur DEC	citation	CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref><ref name="Aerojet Rocketdyne">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
Template:Nowrap	Active	2021	Template:Cvt	Template:Convert	Template:Convert	Template:Cvt	Template:Cvt	57:1	5.5:1	155:1		Atlas: 842 s Vulcan: 1,077 s	Centaur SEC Centaur V	citation	CitationClass=web }}</ref>
Template:Nowrap	Retired	2022	Template:Cvt	Template:Convert	Template:Convert	Stowed: Template:Cvt Deployed: Template:Cvt	Template:Cvt	37:1	5.88:1	280:1			DCSS	citation	CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>
Template:Nowrap	Delivered, not yet flown	2026 (expected)		Template:Cvt	Template:Cvt	Stowed: Template:Cvt Deployed: Template:Cvt	2.15 m (7 ft 1 in)	37:1	5.88:1	280:1			ICPS	citation	CitationClass=web }}</ref>
Template:Nowrap	Delivered, not yet flown	2028 (expected)	Template:Cvt	Template:Convert	Template:Convert	Template:Cvt	Template:Cvt	48:1	5.7:1	215:1			EUS	<ref name="Norbert" /><ref name="Aerojet Rocketdyne 2" /><ref name="sls-update" />
Template:Nowrap	Cancelled	Template:N/a	Template:Cvt	106 kN (23,825 Template:Lbf)	Template:Cvt	2.46 m (8 ft 0.7 in)	1.57 m (4 ft 9 in)	57:1	5.5:1				OmegA	<ref name="Aerojet Rocketdyne 2" /><ref name="SpaceNews 2020" />
Template:Nowrap	Template:Nowrap	2025 (expected)	Template:Cvt	107.29 kN (24,120 Template:Lbf)	Template:Cvt	3.31 m (130.4 in)	1.87 m (73.7 in)	47.29:1	5.5:1				Centaur V	citation	CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>

Partial specifications

All versions

• Contractor: Pratt & Whitney
• Propellants: liquid oxygen, liquid hydrogen<ref name="pwr_rl10b-2.pdf" />
• Design: expander cycle<ref name="Sutton1998">Template:Cite journal</ref>
• Ignition: electric spark.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

RL10A

File:RL-10 rocket engine.jpg

RL10A information and overview

• Thrust (altitude): 15,000Template:Nbsplb-f (66.7 kN)<ref name="S2S">Template:Cite book</ref>
• Specific impulse: Template:Convert
• Engine weight, dry: 298 lb (135 kg)
• Height: 68Template:Nbspin (1.73Template:Nbspm)
• Diameter: 39Template:Nbspin (0.99Template:Nbspm)
• Nozzle expansion ratio: 40 to 1
• Propellant flow: 35 lb/s (16 kg/s)
• Vehicle application: Saturn I, S-IV 2nd stage, 6 engines
• Vehicle application: Centaur upper stage, 2 engines

RL10B-2

File:Second stage of a Delta IV Medium rocket.jpg

Second stage of a Delta IV Medium rocket featuring an RL10B-2 engine

• Thrust (altitude): 24,750 lbf (110.1 kN)<ref name="pwr_rl10b-2.pdf">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• Specific impulse: Template:Convert<ref name="pwr_rl10b-2.pdf" />
• Engine weight, dry: 664 lb (301.2 kg)<ref name="pwr_rl10b-2.pdf" />
• Height: 163.5Template:Nbspin (4.14Template:Nbspm)<ref name="pwr_rl10b-2.pdf" />
• Diameter: 84.5Template:Nbspin (2.21Template:Nbspm)<ref name="pwr_rl10b-2.pdf" />
• Expansion ratio: 280 to 1
• Mixture ratio: 5.88 to 1 oxygen:hydrogen mass ratio<ref name="pwr_rl10b-2.pdf" />
• Propellant flow: fuel, 7.72 lb/s (3.5 kg/s); oxidizer 45.42 lb/s (20.6 kg/s)<ref name="pwr_rl10b-2.pdf" />
• Vehicle application: Delta III, Delta IV second stage (1 engine)

Gallery

• Rl-10engine.jpg

  RL10A-1

• RL-10 with cutaway.JPG

  RL10A-3S

• 500px photo (140471371).jpeg

  RL10A-4

• RL-10onstand.jpg

  RL10A-4-2

• RL-10B-2 engine during nozzle extension testing.jpg

  RL10B-2

Engines on display

• An RL10A-1 is on display at the New England Air Museum, Windsor Locks, Connecticut<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• An RL10 is on display at the Museum of Science and Industry, Chicago, Illinois<ref name="histspace">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• An RL10A-1 is on display at the Cernan Earth and Space Center, River Grove, Illinois
• An RL10 is on display at the U.S. Space & Rocket Center, Huntsville, Alabama<ref name="histspace" />
• An RL10 is on display at Southern University, Baton Rouge, Louisiana<ref>Template:Cite press release</ref>
• Two RL10 engines are on display at US Space Walk of Fame, Titusville, Florida<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}Template:Cbignore</ref>

• An RL10 is on display at the Cox Science Center and Aquarium, West Palm Beach, Florida.
• An RL10 is on display in the Aerospace Engineering Department, Davis Hall at Auburn University.Template:Citation needed
• An RL10A-4 is on display at the Science Museum in London, UK.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• An RL10 is on display at the Museum of Life and Science in Durham, NC
• An RL10 is on display at the San Diego Air & Space Museum in San Diego, CA.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• An RL10B-2 is on display outside the Discovery Cube Orange County in Santa Ana, CA.

See also

• Spacecraft propulsion
• RL60
• MARC-60
• RD-0146
• XCOR/ULA aluminum alloy nozzle engine, under development in 2011

Bibliography

• Template:Cite book

External links

• RL10B-2 at Astronautix
• Spaceflight Now article
• Spaceflight Now article