SABRE (rocket engine)

SABRE
A version of the SABRE engine designed in the 1990s
Country of originUnited Kingdom
DesignerReaction Engines Limited
ApplicationSingle-stage-to-orbit
Associated LVSkylon
PredecessorRB545
StatusResearch and development
Liquid-fuel engine
PropellantAir or liquid oxygen / liquid hydrogen[1]
CycleCombined cycle precooled jet engine and closed cycle rocket engine
Performance
Thrust, vacuumApprox. 2,940 kN (660,000 lbf)[citation needed]
Thrust, sea-levelApprox. 1,960 kN (440,000 lbf)[citation needed]
Thrust-to-weight ratioUp to 14 (atmospheric)[2]
Specific impulse, vacuum460 seconds (4.5 km/s)[3]
Specific impulse, sea-level3,600 seconds (1.0 lb/(lbf⋅h); 35 km/s)[3]

SABRE (Synergetic Air Breathing Rocket Engine[4]) is a concept under development by Reaction Engines Limited for a hypersonic precooled hybrid air-breathing rocket engine.[5][6] The engine is designed to achieve single-stage-to-orbit capability, propelling the proposed Skylon spaceplane to low Earth orbit. SABRE is an evolution of Alan Bond's series of LACE-like designs that started in the early/mid-1980s for the HOTOL project.[7]

The design comprises a single combined cycle rocket engine with two modes of operation.[3] The air-breathing mode combines a turbo-compressor with a lightweight air precooler positioned just behind the inlet cone. At high speeds this precooler cools the hot, ram-compressed air, which would otherwise reach a temperature that the engine could not withstand,[8] leading to a very high pressure ratio within the engine. The compressed air is subsequently fed into the rocket combustion chamber where it is ignited along with stored liquid hydrogen. The high pressure ratio allows the engine to provide high thrust at very high speeds and altitudes. The low temperature of the air permits light alloy construction to be employed and allow a very lightweight engine—essential for reaching orbit. In addition, unlike the LACE concept, SABRE's precooler does not liquefy the air, letting it run more efficiently.[2]

After shutting the inlet cone off at Mach 5.14, and at an altitude of 28.5 km,[3] the system continues as a closed-cycle high-performance rocket engine burning liquid oxygen and liquid hydrogen from on-board fuel tanks, potentially allowing a hybrid spaceplane concept like Skylon to reach orbital velocity after leaving the atmosphere on a steep climb.

An engine derived from the SABRE concept called Scimitar has been designed for the company's A2 hypersonic passenger jet proposal for the European Union-funded LAPCAT study.[9]

  1. ^ "Reaction Engines Limited Engine Names" (PDF). Reaction Engines Limited. Archived from the original (PDF) on 5 March 2012.
  2. ^ a b "The Sensitivity of Precooled Air-Breathing Engine Performance to Heat Exchanger Design Parameters" (PDF). Reaction Engines Limited. 29 March 2007. p. 189. Archived from the original (PDF) on 23 June 2013. Retrieved 9 August 2010.
  3. ^ a b c d "Skylon Users' Manual" (PDF). Reaction Engines Limited. 18 January 2010. pp. 4, 3. Archived from the original (PDF) on 18 April 2016. Retrieved 2 August 2010.
  4. ^ "SABRE – Synergetic Air Breathing Rocket Engine". Reaction Engines Limited. Archived from the original on 19 December 2018. Retrieved 18 December 2018.
  5. ^ "A Comparison of Propulsions Concepts for SSTO Reusable launchers" (PDF). Reaction Engines Limited. pp. 114, 115. Archived from the original (PDF) on 15 June 2011. Retrieved 2 August 2010.
  6. ^ "Flight Applications". Reaction Engines.
  7. ^ "Alan Bond Interview". Vimeo. Retrieved 19 December 2017.
  8. ^ "UK's Sabre space plane engine tech in new milestone". BBC News. 8 April 2019.
  9. ^ "Reaction Engines has reached a number of high profile milestones". Reaction Engines. 2018. Retrieved 8 April 2019.