The company conducted research into space propulsion systems, centred on the development of the Skylon re-usable SSTO spaceplane.

[7] In January 2023 the company announced that it had raised a further £40m from backers including the United Arab Emirates Strategic Development Fund.

[8][9] At the end of October 2024, after unsuccessful attempts to raise more money from investors,[10] the company ceased operations, laying off the majority of staff and entering administration.

In February 2009, the European Space Agency announced that it was partially funding work on Skylon's engine to produce technology demonstrations by 2011.

[14] Commenting on work undertaken at TF2 in Colorado, in April 2019, Reaction Engines announced that it had successfully tested the precooler technology for supersonic conditions needed to prevent the engine from melting,[15] and in October 2019, Reaction announced that it successfully validated its precooler for hypersonic (Mach 5) conditions.

However they felt SSTO as a first application was a very high risk development path and proposed that a Two Stage to Orbit (TSTO) vehicle was a more realistic first step.

[citation needed] In 2016 AFRL released two TSTO concepts using SABRE in the first stage: The first 150 feet (46 m) long carrying an expendable upper stage in an underside opening cargo bay capable of delivering around 5,000 pounds (2,300 kg; 2.3 t) to an orbit of 100 nautical miles (190 km), the second 190 feet (58 m) long carrying a reusable spaceplane on its back, capable of delivering around 20,000 pounds (9,100 kg; 9.1 t) to an orbit of 100 nautical miles (190 km).

[20] The engine, SCIMITAR, has precooler technology which is somewhat similar to SABRE, but does not have the rocket features, and was optimized for higher efficiency for atmospheric flight.

[21] Further studies refined the concept, with an initial configuration to be fitted with five ejector seats, for four passengers and one crew, similar to the first four Space Shuttle spaceflights.

The structure iwas based on a cylinder, designed to allow space inside the cylindrical section for the construction and repair of various spacecraft.

The cylindrical structure would also provide space for habitation modules with docking ports, manipulator arms, and propellant farms to refuel an interplanetary spacecraft.

The concept arose to confirm the capability of the Skylon launch vehicle that it could enable large human exploration to the Solar System's planets.

It was conceived to be assembled from two parts, each sized to fit inside the Skylon payload bay, it would be launched from the Skylon and would also be an integral part for the construction of the Orbital Base Station as well as the Reaction Engines Troy and the retrieval of the Earth Departure Stage from the Precursor mission of the Troy mission.