RS-68

RS-68
An RS-68 engine undergoing hot-fire testing at NASA's Stennis Space Center during its developmental phase.
Country of originUnited States
First flight20 November 2002 (2002-11-20)
Last flight9 April 2024 (2024-04-09)
DesignerRocketdyne
Manufacturer
ApplicationFirst stage engine
Associated LVDelta IV · Delta IV Heavy
StatusRetired
Liquid-fuel engine
PropellantLOX / LH2
CycleGas-generator
Configuration
Nozzle ratio21.5:1
Performance
Thrust, sea-levelRS-68: 2,950 kN (660,000 lbf)
RS-68A: 3,137 kN (705,000 lbf)[1]
Thrust-to-weight ratioRS-68: 45.3:1
RS-68A: 47.4:1
Chamber pressure1,488 psi (10.26 MPa)
Specific impulse, vacuumRS-68: 410 s (4.0 km/s)
RS-68A: 411.9 s (4.039 km/s)[2]
Dimensions
Length5.20 m (17.1 ft)
Diameter2.43 m (8 ft 0 in)
Dry massRS-68: 6,600 kg (14,560 lb)
RS-68A: 6,740 kg (14,870 lb)[1]

The RS-68 (Rocket System-68) was a liquid-fuel rocket engine that used liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator cycle. It was the largest hydrogen-fueled rocket engine ever flown.[3]

Designed and manufactured in the United States by Rocketdyne (later Pratt & Whitney Rocketdyne and Aerojet Rocketdyne). Development started in the 1990s with the goal of producing a simpler, less costly, heavy-lift engine for the Delta IV launch system. Two versions of the engine have been produced: the original RS-68 and the improved RS-68A. A third version, the RS-68B, was planned for the National Aeronautics and Space Administration's (NASA) Ares V rocket before the cancellation of the rocket and the Constellation Program in 2010.

  1. ^ a b "DELTA IV". United Launch Alliance. Archived from the original on 20 July 2014. Retrieved 13 July 2014.
  2. ^ "Delta IV User's Guide" (PDF). United Launch Alliance. June 2013. Archived (PDF) from the original on 10 July 2014. Retrieved 13 July 2014.
  3. ^ "ATK Propulsion and Composite Technologies Help Launch National Reconnaissance Office Satellite" (Press release). Alliant Techsystems. 19 January 2009. Archived from the original on 22 February 2014.