I have always had an admiration for people who combine technical expertise with a creative imagination. Among these is Barnes Wallis, the English aeronautical engineer most famous for inventing the bouncing bomb used to destroy German dams in the second world war. After the war Wallis worked on many pioneering aircraft projects. The problem for Wallis was that he was so brilliant that his ideas were often a little too far ahead of their time for others to be able to believe in them.
At the same time as the development of Concorde, he had a plan to develop an aircraft that could fly non-stop from Britain to Australia. He envisaged that it would fly at mach 5 at around 120,000 feet. But in order for an aircraft designed for this speed to fly slow enough to land on a conventional runway he proposed that it would change shape through huge flaps to make it aerodynamically perfect from a take off at 100 mph through to 4000 mph.
The one thing this concept lacked - and it was a big problem - was an engine. An engine capable of being effective from stand-still through to 4000mph didn't exist. Wallis talked about an engine that could convert from a turbofan to a turbojet, and I'm sure that had this project been given the go-ahead then Wallis would have found a solution.
However, such an engine has now been developed. Reaction Engines, based in Oxfordshire, have worked on a project that began as HOTOL in the 1980s which was a proposal for a reusable unmanned satellite launcher. Funding for HOTOL was cancelled by the Thatcher government (no surprise there) but work on the engine continued. The innovation is that the engine uses oxygen from the air up to about 20 miles negating the requirement to use liquid oxygen for this stage of the flight. The reduction in weight thus carried means the craft could take off like an aircraft and fly directly into space, achieving a step-change in low-Earth orbital access. (HOTOL = HOrizontal Take Off and Landing).
The secret is the special heat exchanger which cools the incoming air extremely rapidly to enable it to mix with the liquid hydrogen fuel. Above 20 miles where the air becomes too thin the engine becomes a rocket engine using stored liquid oxygen.
Reaction Engines have also proposed an engine that operates as an air-breathing HOTOL engine at high speed whilst having the capability of a larger bypass ratio to enable it to operate at slower speeds for a conventional take off and landing.
Reaction Engines have proposed an airliner to go with this, but it looks nothing like as radical as Barnes Wallis's proposals for his shape-changing Universal Aircraft. A Barnes Wallis universal aircraft powered by a jet engine from Reaction Engines would be one of the biggest step-changes in flight ever. Technology today just doesn't have the wow factor of witnessing first-hand the space race or the first take-off of Concorde. Witnessing the first flight of an airliner capable of flying around the world in four hours would render the latest Ipad launch a total bore.
Of course, no one in the UK will be prepared to risk any money on this and it is telling that they have just opened a US subsidiary, in that country where investors seem to have more of a gung-ho spirit. In twenty years time when the first Reaction Engines-powered aircraft rolls off a production line in American we'll all be thinking here in England "how did we let that one slip away". Same old story. But Wallis's great vision of what is possible will finally be realised.