An assessment report by the European Space Agency (ESA) has found that there are 'no impediments or critical items have been identified' which could impede the development of the revolutionary Skylon concept orbital spaceplane. The ESA report, commissioned by the UK Space Agency, also agreed with the objectives of the proposed next stage of the development programme.

The Skylon concept, designed by British company Reaction Engines Limited (REL), is an unpiloted reusable single-stage-to-orbit spaceplane which can take off from a conventional runway. The Skylon uses two air breathing engines which employ liquid hydrogen with atmospheric air up to Mach 5.5 and on-board liquid oxygen beyond that to orbital velocities.

The next stage in development is for Reaction Engines to conduct a demonstration of the engine's pre-cooler technology later this summer.

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The ESA report said: "In summary, the ESA evaluation of the SABRE engine design has not identified any critical items that are a block to future developments. Both the SABRE cycle and the engine components have been assessed as well as the frost control mechanism." Commenting on the next stages of development, the report added: "In the course of the assessment activities ESA has not identified any critical topics that would prevent a successful development of the engine."

Dr David Parker, Director of Technology, Science and Exploration at the UK Space Agency, said: “Both Sabre and Skylon are exciting new technologies that could transform access to space.

“ESA’s positive assessment should give everyone increased confidence that Reaction Engines is on the right track. We are looking forward to the upcoming technology tests with interest.”