First stage of a Delta II rocket.jpg
First stage of a Delta II rocket, including an RS-27
Country of originUnited States
SuccessorRS-27A, RS-56
Liquid-fuel engine
PropellantLOX / RP-1
CycleGas Generator
Thrust, vacuum1,023 kN (230,000 lbf)
Thrust, sea-level971 kN (218,000 lbf)
Chamber pressure4.9 MPa (49 bar)
Specific impulse, vacuum295 seconds (2.89 km/s)
Specific impulse, sea-level264 seconds (2.59 km/s)
Burn time274 Sec
Length3.63 m (11.9 ft)
Diameter1.07 m (3.51 ft)
Dry weight1,027 kg (2,264 lb)
Used in
Delta 2000, 3000, 5000, 6000, first stage[1]

The RS-27 was a liquid-propellant rocket engine developed in 1974 by Rocketdyne to replace the aging MB-3 in the Delta. Incorporating components of the venerable MB-3 and the H-1 designs, the RS-27 was a modernized version of the basic design used for two decades. It was used to power the first stage of the Delta 2000, 3000, 5000, and the first model of the Delta II, the Delta 6000.

The RS-27 was a modified Rocketdyne H-1 built to power the first stage of the Saturn I and Saturn IB and replaced the MB-3 engine that had been used on previous versions of the Delta launcher. NASA had a large supply of surplus H-1 engines in the early 1970s, as the Apollo program was ending.[2][3] In addition to its main engine, the RS-27 included two vernier engines to provide vehicle roll control during flight.[4] RS-27 was later developed into the RS-27A and RS-56.[5][6]


  1. ^ "Delta". Astronautix. Archived from the original on August 17, 2013. Retrieved March 5, 2015.
  2. ^ "RS-27". Astronautix. Archived from the original on October 11, 2011. Retrieved March 5, 2015.
  3. ^ Kyle, Ed. "Extended Long Tank Delta". Retrieved March 5, 2015.
  4. ^ J. K. Ganoung; H. Eaton (April 1, 1981). "The Delta Launch V The Delta Launch Vehicle- P ehicle- Past, Pr ast, Present, and F esent, and Future". The Space Congress Proceedings. 18: 6-6. Retrieved March 12, 2023.
  5. ^ "Atlas IIA(S) Data Sheet". Space Launch Report. Retrieved 9 January 2016.
  6. ^ "RS-27A". Astronautix. Archived from the original on 5 August 2014. Retrieved 10 January 2016.