Part of this project requires an engine that can work both as a rocket engine and a normal air-breathing engine (a hybrid approach essentially).
This would reduce the amount of oxidizer required to send stuff into space, and could greatly reduce the cost of sending things into space.
Now, some key experimental parts of the engine have been built, and are to be tested in public at the Farnborough Air Show in the UK in July.
For more information, as well an overview of the engine and Skylon project, check out the BBC link."
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