An RL10 at the U.S. Space & Rocket Center with cutaway showing tubing through the bell
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Country of origin | United States of America |
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First flight | 1962 (RL10A-1) |
Designer | Pratt & Whitney/MSFC |
Manufacturer |
Pratt & Whitney Space Propulsion Pratt & Whitney Rocketdyne Aerojet 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 | 5.5 or 5.88:1 |
Cycle | Expander cycle |
Configuration | |
Nozzle ratio | 84:1 or 280:1 |
Performance | |
Thrust (vac.) | 110 kN (25,000 lbf) |
Isp (vac.) | 450–465.5 seconds (4.413–4.565 km/s) |
Burn time | 700 seconds |
Dimensions | |
Length | 4.14 m (13.6 ft) w/ nozzle extended |
Diameter | 2.13 m (7 ft 0 in) |
Dry weight | 277 kg (611 lb) |
Used in | |
Centaur S-IV DCSS |
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References | |
References | |
Notes | Performance values and dimensions are for RL10B-2. |
The RL10 is a liquid-fuel cryogenic rocket engine used on the Centaur, S-IV and DCSS upper stages. Built in the United States by Aerojet Rocketdyne (formerly by Pratt & Whitney Rocketdyne), the RL10 burns cryogenic liquid hydrogen and liquid oxygen propellants, with each engine producing 64.7 to 110 kN (14,545–24,729 lbf) of thrust in vacuum depending on the version in use. The RL10 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 RL10A-4-2 and the RL10B-2, still being produced and flown on the Atlas V and Delta IV.
The engine produces a specific impulse (Isp) of 373 to 470 s (3.66–4.61 km/s) in a vacuum and has a mass ranging from 131 to 317 kg (289–699 lb) (depending on version). Six RL10A-3 engines were used in the S-IV second stage of the Saturn I rocket, one or two RL10 engines are used in the Centaur upper stages of Atlas and Titan rockets and one RL10B-2 is used in the upper stage of Delta IV rockets.
The RL10 was first tested on the ground in 1959, at Pratt & Whitney's Florida Research and Development Center in West Palm Beach, Florida. It was first flown in 1962 in an unsuccessful suborbital test; 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. The RL10 was designed for the USAF from the beginning as a throttleable motor for the Lunex lunar lander, finally putting this capability to use twenty years later in the DC-X VTOL vehicle.