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 110 kN 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 efficiency, with in-service variants achieving specific impulses (Isp) of up to 465.5 s (4.565 km/s) in a vacuum. Mass ranges from 131 to(-) depending on the version of the engine.[2][3]

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.[4] The engine was electric spark ignited.[5]

The RL10 was first tested on the ground in 1959, at Pratt & Whitney's Florida Research and Development Center in West Palm Beach, Florida.[6][7] The first successful flight took place on November 27, 1963.[8][9] 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.[10]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[11] and the Titan program included Centaur D-1T upper stages powered by two RL10A-3-3 Engines.[11][12]

Four modified RL10A-5 engines were used in the McDonnell Douglas DC-X.[13]

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.[14]

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.[15] 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 (CECE) demonstrator. CECE was intended to lead to RL10 engines capable of deep throttling.[16] In 2007, its operability (with some "chugging") was demonstrated at 11:1 throttle ratios.[17] 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.[18] In 2010, the throttling range was expanded further to a 17.6:1 ratio, throttling from 104% to 5.9% power.[19]

country of origin	United States
first date	1962 (RL10A-1)
manufacturer	Aerojet Rocketdyne
purpose	Upper stage engine
associated	Atlas,Delta III,Delta IV,Saturn I,SLS,Titan IIIE,Titan IV,Vulcan Centaur Canceled: DC-X,OmegA,Shuttle-Centaur,EUS
status	In production
type	liquid
oxidiser	LOX
fuel	LH2
mixture ratio	5.88:1
cycle	Expander cycle‡R1R‡
nozzle ratio	84:1 or 280:1
thrust(vac)	110.1 kN
specific impulse vacuum	465.5 isp
length	4.15 m w/ nozzle extended
diameter	2.15 m
dry weight	301 kg
used in	Centaur, DCSS, S-IV
notes	Performance values and dimensions are for RL10B-2.

History

Common Extensible Cryogenic Engine

Early 2010s possible successor

Applications

Current

Cancelled

Table of versions

Gallery

Engines on display

See also

Bibliography

External links

References

Improvements