RL10

RL-10

An RL-10 at the London Science Museum.
Country of origin	United States of America
First flight	1962 (RL-10A-1)
Designer	MSFC/Pratt & Whitney
Manufacturer	Pratt & Whitney Rocketdyne
Application	Upper stage engine
Associated L/V	Atlas Titan Delta IV Saturn I
Status	In production
Liquid-fuel engine
Propellant	Liquid oxygen / Liquid hydrogen
Mixture ratio	5.85:1
Cycle	Expander cycle
Configuration
Nozzle ratio	250:1
Performance
Thrust (Vac.)	110 kN (25,000 lbf)
Isp (Vac.)	465.5 seconds
Burn time	700 seconds
Dimensions
Length	4.14 m (13.6 ft) (nozzle extended)
Diameter	2.13 m (7 ft 0 in)
Dry weight	277 kg (610 lb)
Used in
Centaur S-IV DCSS
References
References	[1]
Notes	Performance values and dimensions are for RL-10B-2.

The RL-10 is a liquid-fuel cryogenic rocket engine used on the Centaur, S-IV and DCSS upper stages. Built in the United States of America by Pratt & Whitney Rocketdyne, the RL-10 burns cryogenic liquid hydrogen & liquid oxygen propellants, with each engine producing 64.7–110 kN (14,545–24,729 lb_f) of thrust in vacuum depending on the version in use. The RL-10 was the first liquid hydrogen rocket engine to be built in the United States, and development of the engine by Marshall Space Flight Center and Pratt & Whitney began in the 1950s, with the first flight occurring in 1961. Several versions of the engine have been flown, with two, the RL-10A-4-2 and the RL-10B-2, still being produced and flown on the Atlas V and Delta IV.

The engine produces a specific impulse (I_sp) of 373-470 seconds in a vacuum and has a mass ranging from 131–317 kg (290–700 lb) (depending on version). Six RL-10A-3 engines were used in the S-IV second stage of the Saturn I rocket, one or two RL-10 engines are used in the Centaur upper stages of Atlas and Titan rockets and one RL-10B-2 is used in the upper stage of Delta IV rockets.

History

The RL10 was first tested on the ground in 1959, at the Santa Susana Field Laboratory (SSFL) of North American Aviation. It was first flown in 1962 in an unsuccessful suborbital test;^[2] the first successful flight took place on November 27, 1963.^[3][4] 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.^[5]

Improvements

The RL10 has been upgraded over the years. One current model, the RL10B-2, powers the Delta IV second stage, as well as the Delta III second stage. It has been significantly modified from the original RL10 to improve performance. Some of the enhancements include an extendable nozzle and electro-mechanical gimbaling for reduced weight and increased reliability. Current specific impulse is 464 s (equivalent to an exhaust velocity of 4.55 km/s).

Variants

Specifications

Original RL10

• Thrust (altitude): 15,000 lbf (66.7 kN)^[7]
• Burn Time: 470 s^[7]
• Design: Expander cycle^{[citation needed]}
• Specific impulse: 433 s (4.25 kN·s/kg)^{[citation needed]}
• Engine weight - dry: 298 lb (135 kg)
• Height: 68 in (1.73 m)
• Diameter: 39 in (0.99 m)
• Nozzle expansion ratio: 40 to 1
• Propellants: LOX & LH2
• Propellant flow: 35 lb/s (16 kg/s)
• Contractor: Pratt & Whitney
• Vehicle application: Saturn I / S-IV 2nd stage - 6-engines
• Vehicle application: Centaur upper stage - 2-engines

Current design

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

RL10B-2 Specifications

• Thrust (altitude): 24,750 lbf (110.1 kN)^[16]
• Design: Expander cycle^[17]
• Specific impulse: 464 s (4.55 kN·s/kg)^[16]
• Engine weight - dry: 610 lb (277 kg)^[16]
• Height: 163 in (4.14 m)^[16]
• Diameter: 87 in (2.21 m)^[16]
• Expansion ratio: 250 to 1
• Mixture ratio: 5.85 to 1 ^[16]
• Propellants: Liquid oxygen & liquid hydrogen^[16]
• Propellant flow: Oxidizer 41.42 lb/s (20.6 kg/s), fuel 7.72 lb/s (3.5 kg/s)^[16]
• Contractor: Pratt & Whitney
• Vehicle application: Delta III, Delta IV second stage (1 engine)

A flaw in the brazing of an RL10B-2 combustion chamber was identified as the cause of failure for the May 4, 1999, Delta III launch carrying the Orion-3 communications satellite.^[18]

RL10A-4-2

The other current model, the RL10A-4-2, is the engine used on Centaur upper stage for Atlas V.^[16]

Other rockets using RL10

Four modified RL10A-5 engines, all of them with the ability to be throttled, were used in the McDonnell Douglas DC-X.^{[citation needed]}

The DIRECT version 3.0 proposal to replace Ares I and Ares V with a family of rockets sharing a common core stage, recommends the RL10 for the second stage of their proposed J-246 and J-247 launch vehicles.^[19] Up to seven (7) RL10 engines would be used in the proposed Jupiter Upper Stage, serving an equivalent role to the Ares V Earth Departure Stage.

Future use of the RL10

Several potential uses of enhanced versions of the RL10 engine have been proposed:

Manned lunar missions

In 2005 NASA announced the decision to use an Apollo-like spacecraft configuration for the proposed Orion spacecraft. At that time NASA decided that the descent stage of the new Lunar Surface Access Module (LSAM) would be powered by liquid hydrogen and liquid oxygen. The original plan called for the ascent stage to use liquid methane and liquid oxygen, but that has changed^[when?] and the ascent stage will now also use LH2/LOX.^{[citation needed]}

Because of the choice of propellents, along with the need to land the spacecraft in the polar regions of the Moon from an equatorial orbit, NASA decided to use the RL10 as the main powerplant for the descent stage engine.^{[citation needed]} Current specifications call for four RL10 engines to be used on the descent stage and a single RL10 for the ascent stage. Currently, the RL10B-2 engines used on the Delta III and Delta IV can thrust at 20% of maximum thrust. Because of the need for the LSAM to hover above the lunar surface, along with providing a smooth landing, the new RL10 engines must be able to thrust as low as 10%. The use of the RL10 will allow NASA to keep costs on the lunar program down by using existing hardware, albeit modified to enhance performance or allow for manned spaceflight.^{[citation needed]}

Common Extensible Cryogenic Engine

The CECE at full throttle.

The Common Extensible Cryogenic Engine (CECE) is a testbed to develop RL10 engines that throttle well. NASA has contracted with Pratt & Whitney Rocketdyne to develop the CECE demonstrator engine.^[20] In 2007 its operability (with some "chugging") was demonstrated at 11-to-1 throttle ratios.^[21] In 2009 NASA reported successfully throttling from 104 percent thrust to eight percent thrust, a record for an engine of this type. Chugging was eliminated by injector and propellant feed system modifications that control the pressure, temperature and flow of propellants.^[22]

Advanced Common Evolved Stage

As of 2009^[update], an enhanced version of the RL10 rocket engine was proposed to power the upper-stage versions of the Advanced Common Evolved Stage (ACES), a long-duration, low-boiloff extension of existing ULA Centaur and Delta Cryogenic Second Stage (DCSS) technology.^[23] Long-duration ACES technology is explicitly designed to support geosynchronous, cislunar, and interplanetary missions as well as provide in-space propellant depots in LEO or at L₂ that could be used as way-stations for other rockets to stop and refuel on the way to beyond-LEO or interplanetary missions. Additional missions could include the provision of the high-energy technical capacity for the cleanup of space debris.^[24]

See also

• Spacecraft propulsion
• RD-0146
• XCOR/ULA aluminum alloy nozzle engine, under development in 2011 ff.
• Rocketdyne
• Pratt & Whitney Rocketdyne

References

Wikimedia Commons has media related to: RL10

Notes

Bibliography

• Connors, Jack (2010). The Engines of Pratt & Whitney: A Technical History. Reston. Virginia: American Institute of Aeronautics and Astronautics. ISBN 978-1-60086-711-8. 

External links

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

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