New test for space 'lifeboat'

The US space agency Nasa has conducted a second, successful flight test on the X-38 Crew Return Vehicle (RCV).

The spacecraft, designed to be used as a lifeboat for the International Space Station (ISS), was dropped from underneath the wing of a B-52 bomber. A similar test was conducted about a year ago.

The RCV flew freely for about 10 seconds before a parafoil was deployed to guide the craft to its landing point. Following this successful test at Nasa's Dryden Flight Research Centre, California, the prototype vehicle will now be redesigned to look like an 80% scale model of the eventual spacecraft.

Low-cost option

The X-38 will be the first new, manned spacecraft to travel to and from orbit that has been built in the past two decades.

In the early years of the ISS, a Russian Soyuz spacecraft will be attached to the station as an emergency lifeboat. But, as the size of the crew aboard the station increases, the Soyuz will no longer be large enough - a return vehicle like the CRV that can accommodate up to seven passengers will be needed.

X-38 Project Manager John Muratore says the project has two real purposes: "The first is to prove that we can build a low-cost crew return vehicle for the Space Station.

"The second, more general purpose is to prove that we can build human spacecraft for far less than ever before."

"The original crew return vehicle project was costed as much as $2bn back in the late 1980s, but under the X-38 project, we're going to build and test-fly two prototypes in space for $90m."

Commercial equipment

The X-38 can be built relatively cheaply because it uses tried and trusted technology. Its shape, for example, uses a so-called lifting body concept originally developed by the US Air Force's X-24A project in the mid-1960s.

The X-38 flight computer is commercial equipment that is already in use in aircraft, and the flight software operating system is a commercial system already in use in many aerospace applications.

A special coating that had already been developed by Nasa is planned for use on the X-38 thermal tiles to make them much more durable than the tiles used on the Space Shuttle.

The X-38's primary navigational equipment, the Inertial Navigation System/Global Positioning System, is a unit already in use on military aircraft.

Emergency procedure

If there is ever an emergency aboard the Space Station, the X-38 will swing into action.

The crew, possibly injured, will scramble inside, seal the hatch behind them and press the undock button. Then there will be little for them to do - the return to Earth will be automatic.

Following the jettison of a rocket pack called the deorbit engine module, the X-38 will glide to Earth unpowered, just like the Space Shuttle.

In the lower part of the atmosphere, it will use a steerable parafoil parachute to land, a technology recently developed by the US Army. Its landing gear consists of skids rather than wheels.

Further tests on the X-38 are planned for late 2000. It should begin operations aboard the International Space Station in 2003.