SABRE (rocket engine)

SABRE (Synergetic Air Breathing Rocket Engine) was a concept under development by <a href="/facts/Reaction_Engines_Limited/X5lDckBh">Reaction Engines Limited</a> for a <a href="/facts/Hypersonic/QUsQbhur">hypersonic</a> <a href="/facts/Precooled_jet_engine/PfGMWtvB">precooled</a> hybrid <a href="/facts/Engine/p0m7aXaW">air-breathing</a> <a href="/facts/Rocket_engine/XT5gaFAb">rocket engine</a>. The engine was designed to achieve <a href="/facts/Single-stage-to-orbit/4qPbu35V">single-stage-to-orbit</a> capability, propelling the proposed <a href="/facts/Skylon_(spacecraft)/b8YIGYjn">Skylon</a> <a href="/facts/Spaceplane/oMJNJPy7">spaceplane</a> to low Earth orbit. SABRE was an evolution of <a href="/facts/Alan_Bond_(engineer)/5sBURCBz">Alan Bond</a>'s series of <a href="/facts/Liquid_air_cycle_engine/ySDzpQd0">LACE</a>-like designs that started in the early/mid-1980s for the <a href="/facts/HOTOL/do33C6Pf">HOTOL</a> project. Reaction Engines went into bankruptcy in 2024 before completing the project.
The design comprised a single <a href="/facts/Combined_cycle/WgEIh89p">combined cycle</a> rocket engine with two modes of operation. The air-breathing mode combined a turbo-<a href="/facts/Gas_compressor/I0vV0Tx2">compressor</a> with a lightweight air <a href="/facts/Precooled_jet_engine/PfGMWtvB">precooler</a> positioned just behind the <a href="/facts/Inlet_cone/4sEVTE72">inlet cone</a>. At high speeds this precooler would cool the hot, ram-compressed air, which would otherwise reach a temperature that the engine could not withstand, leading to a very high <a href="/facts/Overall_pressure_ratio/dFVVlj2X">pressure ratio</a> within the engine. The compressed air would subsequently be fed into the rocket <a href="/facts/Combustion_chamber/FNqjDrN8">combustion chamber</a> where it would be ignited along with stored <a href="/facts/Liquid_hydrogen/Vpk3Gb8P">liquid hydrogen</a>. The high pressure ratio would allow the engine to provide high thrust at very high speeds and altitudes. The low temperature of the air would permit light alloy construction to be employed and this allow a very lightweight engine—essential for reaching orbit. In addition, unlike the LACE concept, SABRE's precooler would not <a href="/facts/Liquid_air/soClHXAx">liquefy the air</a>, thus letting it run more efficiently.
After shutting the inlet cone off at <a href="/facts/Mach_number/Ee01MIgw">Mach</a> 5.14, and at an altitude of 28.5 km (17.7 mi), the system would continue as a <a href="/facts/Staged_combustion_cycle_(rocket)/eINPGPr5">closed-cycle</a> high-performance rocket engine burning <a href="/facts/Liquid_oxygen/qnI0KDTb">liquid oxygen</a> and <a href="/facts/Liquid_hydrogen/Vpk3Gb8P">liquid hydrogen</a> from on-board fuel tanks, potentially allowing a hybrid <a href="/facts/Spaceplane/oMJNJPy7">spaceplane</a> concept like <a href="/facts/Skylon_(spacecraft)/b8YIGYjn">Skylon</a> to reach orbital velocity after leaving the atmosphere on a steep climb.
An engine derived from the SABRE concept called <a href="/facts/Reaction_Engines_Scimitar/8AnH3hY7">Scimitar</a> has been designed for the company's <a href="/facts/Reaction_Engines_A2/9gzDEcHb">A2</a> <a href="/facts/Supersonic_transport/vtbRALKG">hypersonic passenger jet</a> proposal for the <a href="/facts/European_Union/6GYcR8qM">European Union</a>-funded <a href="/facts/LAPCAT/cdKtvvUG">LAPCAT</a> study.

SABRE (rocket engine) open-in-new

SABRE (rocket engine)