RS-27A

The RS-27A is a liquid-fuel rocket engine developed in 1980s 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.

RS-27A

RS-27A Engine on Delta II
Country of origin	United States
Date	1989
Designer	Rocketdyne
Manufacturer	Rocketdyne, Pratt & Whitney Rocketdyne
Application	Booster
Predecessor	RS-27
Status	Retired
Liquid-fuel engine
Propellant	LOX / RP-1
Cycle	Gas Generator
Configuration
Chamber	1
Performance
Thrust, vacuum	1,054.2 kN
Thrust, sea-level	890.1 kN (200,102 lbf)
Thrust-to-weight ratio	102.47
Chamber pressure	4.8MPa (700 psia)
Specific impulse, vacuum	302 seconds (2.96 km/s)
Specific impulse, sea-level	255 seconds (2.50 km/s)
Burn time	265 Sec
Dimensions
Length	3.78 m (12.40 ft)
Diameter	1.70 m (5.58 ft)
Dry weight	1,147 kg (2,528 lb)
Used in
Delta 7000, first stage[1]

The RS-27A main engine is neither restartable nor throttleable. In addition to its main engine, it includes two vernier engines to provide vehicle roll control during flight.[3] When used as the main booster propulsion system for the Delta II family of launch vehicles, has an operational duration of 265 seconds. The last RS-27A engine was used for the ICESat-2 launch on 15 September, 2018.