One step beyond

Space, as the saying goes, is the final frontier. At least, it is for tourists. And while Virgin Galactic’s SpaceShipTwo is probably the best-known craft aiming to take paying customers for the ultimate joy-ride into the zone of zero-gravity and terrific views, Europe’s premier player in space, EADS Astrium, is determined it will not be the only one.

Astrium has the Spaceplane, its own concept for a space tourism craft, in an advanced stage of development. It is based around a different concept of flight than SpaceShipTwo and the company hopes it will be ready for its first flight in 2011 — two years after Virgin Galactic’s planned maiden flight.

While SpaceShipTwo’s design looks like a cross between a shuttlecock and a catamaran, Astrium’s Spaceplane has a more conventional appearance. Without the viewing portholes it looks similar to a business jet. This, explained Hugues Laporte-Weywada, the company’s deputy chief technology director and senior designer, follows on from his decision to go for a single-stage spaceplane concept.

Unlike SpaceShipTwo, which is conveyed to high altitude below a purpose-designed jet carrier and is equipped only with a rocket engine, the Spaceplane carries both jet turbofan and rocket engines and will make the entire journey under its own power.

‘We came to the conclusion that if we were to develop a two-vehicle configuration, we’d have to design the specific carrier from scratch, and that’s quite expensive; the carrier has good aerodynamic performance at lower velocities, while the spacecraft isn’t trimmed for that. The separation is somewhat problematic, as well.’

Laporte-Weywada also believes that, as well as making the concept simpler, the single-vehicle model has certain safety advantages. ‘We can at any point go back to the previous configuration of our vehicle, and come safely back into land,’ he said. ‘There is no stopping point where we would have to decide to jettison or not.’

The plan is for the Spaceplane to take off under jet power from a conventional airport. The turbofans will carry it to an altitude of 12km in 45min, at which point its rocket engine will ignite and burn for 80sec, sufficient to accelerate the craft up to the edge of the atmosphere, about 50km up. The plane’s momentum will then carry it up to its maximum altitude of 100km and back down to the edge of the atmosphere in a parabolic arc, during which the passengers will experience zero gravity for about 3min. Like SpaceShipTwo, the craft is suborbital — the lowest satellite orbits are around 200km — but still high enough to be considered a trip into space.

The atmosphere will brake the craft as it descends, unpowered, back down to about 15km. Here the flightplan differs again from SpaceShipTwo — and from any previous reusable spacecraft. Rather than gliding all the way back to a landing, the jet engines will re-ignite and fly the craft down for a conventional landing at the airport.

Laporte-Weywada claims this is a more practical concept than Virgin Galactic’s model. ‘It’s a more advanced vehicle with respect to future missions,’ he claimed. ‘As it’s a single, moderately-sized vehicle, it leads the way towards high-speed transportation systems, which won’t be multiple-stage concepts. They’ll be like airliners, which  you step onto at one end of the journey and off at the end.’

The flightplan dictates the design. The wings, set far back along the fuselage, are suited to withstanding the harsh acceleration of the rocket phase of the flight. Their wide span, along with the forward canard winglets just behind the cockpit, give the plane good gliding aerodynamics as it re-enters the atmosphere.

The interior of the craft, created by Australian designer Marc Newsom, is intended to give the four passengers — each of whom will pay some €200,000 (£158,000) for their trip — the most comfortable ride possible.

Newsom described the seats as ‘high-tech hammocks’, pivoting around the point where they are attached to the fuselage so that their position relative to the earth, while they are seated, always remains the same. Once in the weightless section of the flight, the seats rotate at right-angles to the axis of the fuselage to maximise the amount of space inside the cabin for the passengers to float around.

The rocket for the vehicle is derived from existing technology, based on a scaled-down version of the Vulcain engine, the main propulsion system for the Ariane 5 launcher. This, however, is hydrogen-fuelled. ‘We looked at hydrogen fuel, but we would require a very large volume of fuel,’ said Laporte-Weywada. ‘We decided instead to modify the engine so that it could burn methane.’

Unlike Ariane’s engine, the Spaceplane has to be reusable, and Astrium is aiming for a design that can fly 30 times.

‘We are in an experimental phase for the rocket propulsion system,’ said Laporte-Weywada. ‘We’ve already done some testing on the main injection and cooling systems at our site near Munich, which are the main areas of innovation in the design. But we’ll develop the engine in parallel with the development of the whole vehicle.’

Critics of the Spaceplane’s design — including SpaceShipTwo designer Burt Rutan — have said the ship’s two different operating modes and propulsion systems will cause problems. Rutan claimed the plane is much heavier than SpaceShipTwo so will require more rocket power, and fuel, to kick the whole mass beyond the atmosphere. There is also the issue of the exposure of the jet engines to vacuum, then to the heat of re-entry. Will they restart reliably?

Laporte-Weywada does not think there will be a problem. The short duration of the trip into space — the whole journey lasts just over an hour — means the engines will not undergo the prolonged ‘cold soak’ of an orbital voyage, so their function will not be compromised.

‘And we don’t have any thermal problem in re-entry,’ he added. ‘The energy that has to be dissipated, the braking energy, is not high enough to need any specific type of thermal material, like the ceramic tiles on the Shuttle. We’re flying from a much lower altitude and at a lower speed [than an orbital re-entry], so the thermal energy is much, much lower.’

Laporte-Weywada is confident the turbofans will restart once the Spaceplane is safely back in the atmosphere. ‘We do have to see what is the behaviour of the engine in this situation, with very low air pressure, and we’ll address that step by step,’ he said. ‘But the first indications are showing that we should have no difficult points on reusability.

‘There could be other ways to restart, such as repressurising the engine. In any case, if the engines do not restart, the craft has a very good aerodynamic profile for gliding, and we could easily glide all the way back in to land.’

Laporte-Weywada is keen to point out that, although the Spaceplane is being conceived as a pleasure craft, there are other potential applications.

‘We could perform experiments in weightlessness in a wide volume, with a much longer duration than current weightless planes — they only have a 20sec duration of zero gravity,’ he said. ‘Observation could be another application — you could carry telescopes very far out of the atmosphere for relatively quick observations of earth or the stars.’

Despite this, Astrium is not seeking public funding for the development of the Spaceplane, which the company estimates will cost €1bn. ‘Our business plan shows that investors at the beginning would be repaid by the revenues we’ll gather from the demand for these flights,’ Laporte-Weywada said. The market has been estimated at some 5,000 passengers a year by 2020, and Astrium plans to secure 30 per cent of this, which would require a fleet of 20 Spaceplanes.

Above all, Laporte-Weywada said, the Spaceplane should be considered as a demonstrator for the technology.

‘It’s the forerunner for future spacecraft, just as the Wright Brothers’ flyer was a forerunner of Concorde and the A380,’ he said. ‘And we should remember that when air travel started, tickets were very, very expensive but now it is commonplace and most people can afford it. This is the way these technologies, and these markets, develop.’