Consider a ramjet a simple design of no moving parts which works efficiently at speeds around Mach 3 with a upper limit of Mach 6. Nasa had already tested X-43A, a scramjet at hypersonic speeds which is much lighter then conventional rockets because it does not carry oxidizer. Despite a 8 year program costing 230 million dollars it was a successful pioneering piece of technology of which seems to break record speeds.
it size was 12 feet by 5 feet, it also requires a craft to carry the test jet to workable speeds before launching.
The scramjet offers a possible solution to the requirements of escaping the atmosphere by reaching mach 6. The momentum of a vehicle alone could help escape the earths gravitational pull. But without the additional continued thrust in the vacuum of space, it is likely the craft will be drawn back to back to earth. The best current solution is a multi-engine configuration to power the craft to for each environment. This can be a heavy solution to this problem, as weight can be a limiting factor to a aircraft as well as a space craft.
Only recently has a new piece of technology that could solve the multi-environment problem by modifying current rocket technology to allow the burning of hydrogen fuel. Alan Bond had begun work on rocket engines in 1982 with a view to overcoming the inadequate characteristics of existing rocket-based expendable launch vehicles. Within this work Alan realised that the use of heat exchangers within rocket engine cycles can greatly increase their efficiency by allowing them to use atmospheric air to burn in the combustion chambers when flying in the atmosphere like a jet (rather than using heavy liquid oxygen stored in on-board tanks) and extracting heat where it causes a problem whilst using that heat to power the turbo machinery in the engine.
These new Synergetic Air-Breathing Rocket Engines (SABRE) would be suitable for powering modified aircraft directly into Earth orbit and it was subsequently found that in a reconfigured form they would be able to propel aircraft at cruise speeds of up to five times the speed of sound. The key enabling technology that needed to be developed to make these new engines viable was lightweight heat exchangers.
Inspired by the miniaturisation of the silicon chip, and understanding that heat exchangers were far from reaching their physical limit in terms of miniaturisation, developing high power lightweight heat exchangers and understanding the design of the new engines and vehicles that they enable became the focus of Alan Bond and subsequently REL (Reaction Engines Limited). Reaction Engines Ltd ('REL') was founded in 1989 by Alan Bond and the principal two engineers from Rolls Royce behind the RB545 engine programme, John Scott-Scott and Richard Varvill.
There were many problems to be solved for Reaction Engines Ltd at hypersonic speeds such as cooling the oxygen from 1000 degrees to manageable temperatures as well as water vapor forming and freezing in the heat exchange. All main problems seem to be resolved and currently a prototype is being tested and working.
The new atmosphere breathing rocket engine can reduce the fuel payload for the oxidizer, which will only be required for the vacuum of space. The liquid hydrogen will still be required but allows longer run times and is quite clean and cheap to run, also it is reusable for space travel.
Most of the funding for the skylon project is supplied by private investment, which suggests that the commercial sector will be able to provide cheap and affordable global travel. Flight times across the world would be reduced to 4 hours, also this type of vehicle can make space tourism a real possibility. Imagine that a craft can fly over 200 miles in orbit to a space station using liquid hydrogen and oxygen. The cost of orbiting to space will be reduced to a fraction of the current price from current technologies. The future of space might be the exploration of other planets. But the technology to fly to low orbit has just become a reachable low cost achievement.
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