There’s something of the optimistic, heroic post-war spirit to SKYLON, the reusable spaceplane under development by Reaction Engines of Abingdon, Oxfordshire. Although it needs no pilot, Dan Dare would surely have been just the man for the job. The SKYLON vehicle is named after the Powell and Moya-designed Skylon needle that floated above the 1951 Festival of Britain and – weirdly – the spacecraft has a similar shape and scale to the sculpture even if the way it challenges gravity is based on more advanced British technology.
Far from being a piece of nostalgic design, the SKYLON is an important proposition for space travel and could be in commercial service by 2020. Delivering 12 tonnes into orbit, it will be ready to fly again within two days of a mission, and capable of 200 flights over its lifetime. At 82m long, it is longer than a Boeing 747, but its wingspan is a mere 25m. Its fuselage is only 6.25m across and with a black aeroshell skin of fibre-reinforced ceramic, it’s a sleek, dramatic form. However, the design of the truss-framework structure is purely functional, minimising atmospheric drag. Most of the fuselage is occupied by two liquid hydrogen tanks, with the payload bay between them.
So far, everything in orbit has got there on multi-stage rockets – even the ‘reusable’ Space Shuttle sheds vast booster rockets that are strapped on to launch it. SKYLON, however, takes off and lands all in one piece. What it could deliver to orbit includes geosynchronous satellites (which remain fixed relative to the Earth), supplies to the International Space Station, Solar Power Satellites, or even a module for 25 people. ‘SKYLON can support anything that is foreseeable in the near- and mid-term future,’ comments Dr Mark Hempsell, the Future Programmes Director at Reaction Engines.
Reaction Engines, as the name suggests, is primarily interested in building engines. The company was set up in 1989 by engineer Alan Bond, leader of an earlier British Aerospace spaceplane design called HOTOL. After the British government withdrew its funding from HOTOL, Bond set about designing a better spaceplane with Reaction Engines’ co-founders Richard Varvill and John Scott-Scott, both ex-Rolls Royce engineers. Initially, they used Amstrad personal computers to crunch numbers. What emerged was not just the new SKYLON design, but its key element – a revolutionary engine called SABRE. It performs as an air-breathing jet up to a speed of Mach 5, then switches during flight into a rocket, conventionally burning hydrogen and oxygen. What makes SABRE’s performance so efficient is a unique system that uses helium to cool incoming air by 1150?C while in air-breathing mode, so it can be compressed and burnt with hydrogen. The unusual way the exterior curves slightly, like a banana, is a design feature that points the air intake directly into the engine during ascent.
Currently, the engine development is part-funded by the European Space Agency, but the mechanical structure of SKYLON is privately funded. Eventually, Reaction Engines would license the vehicle design to be built and operated by others, so the company could concentrate on engine technologies. That hasn’t stopped Reaction Engines though from pursuing what it calls ‘advanced studies’ based on SKYLON’s capabilities.
Bond has an unusual track-record with what may seem flights of fancy. In the 1970s, he led a project for the British Interplanetary Society to design a space probe to reach a nearby star. The work gained much respect for its grounding in what was feasible. Research Engines’ concepts don’t go that far, but they have explored possible scenarios for the infrastructure that would be built around the SKYLON. These include an Orbital Base Station, which is a vast open cylindrical frame – effectively an orbiting shipyard. Large spacecraft built in it could go to Mars, and Reaction Engines has a plan for such a mission in 2028.
However, Bond shares an understanding with American space entrepreneurs that there must be a market for what he offers. ‘It is essential to get space transportation into the same economic framework as all other human activity, if human aspirations for a future involving the off-Earth resources of the solar system are to be realised,’ he says. ‘SKYLON is only a beginning and other propulsion systems and transport architecture will rapidly follow’. Bond cannot predict the future, but anticipates a day when ‘we will not be tied to this one piece of flotsam left over from the formation of the Sun.’
SKYLON has a long way to go before it flies. Perhaps the biggest fear is the sort of funding dry-up that led to the cancellation of previous British space projects. Bond says ‘I lament the loss of the opportunity HOTOL afforded the UK and the terrible attrition of highly skilled and talented people that the nation consigned to the “scrap-heap” during the 1980s.’ Nowadays, he is more confident, and says that ‘we have no complaints about the level of support and interest we currently enjoy.’
