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Tail of an Thor XLT Stage with the RS-27 A engine.jpg
RS-27A Engine on Delta II
Country of origin USA
Date 1989
Designer Rocketdyne
Manufacturer Rocketdyne, Pratt & Whitney Rocketdyne
Application Booster
Predecessor RS-27
Status In use
Liquid-fuel engine
Propellant LOX / RP-1
Cycle Gas Generator
Chamber 1
Thrust (vac.) 1,054.2 kN
Thrust (SL) 890.1 kN (200,102 lbf)
Thrust-to-weight ratio 102.47
Chamber pressure 4.8MPa (700 psia)
Isp (vac.) 302 seconds (2.96 km/s)
Isp (SL) 255 seconds (2.50 km/s)
Burn time 265 Sec
Length 3.78 m (12.40 ft)
Diameter 1.07 m (3.51 ft)
Dry weight 1,147 kg (2,528 lb)
Used in
Delta 7000, first stage[1]

The RS-27A is a liquid-fuel rocket engine developed by Rocketdyne for use on the first stage of the Delta II and Delta III launch vehicles. It provides 1.05 meganewtons (240,000 lbf) of thrust burning RP-1 and LOX in a gas-generator cycle. The engine is a modified version of its predecessor, the RS-27;[2] its thrust nozzle has been extended to increase its area ratio from 8:1 to 12:1, which provides greater efficiency at altitude. The earlier RS-27 was derived from surplus Rocketdyne H-1 engines used in the Saturn 1B launcher.[3]

The RS-27A main engine is neither restartable nor throttleable. In addition to its main engine, the RS-27A includes two vernier engines to provide vehicle roll control during flight. The RS-27A has a run duration of 265 seconds.


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