The space plane will be cheaper than the current shuttle series
Nasa has revealed its first set of mission criteria for the Orbital Space Plane (OSP) - the series of space vehicle expected to replace the space shuttle from 2012.
The new spacecraft's primary function will be to ferry crews to and from the International Space Station (ISS) and serve as a lifeboat if the station has to be evacuated.
At present the ISS has a Soyuz spacecraft attached to it to transport the crew for emergencies.
The safety of manned space missions has been in the spotlight following the loss of the space shuttle Columbia, which broke up on re-entry on 1 February killing its crew of seven.
The US space agency has grounded its remaining three shuttles Atlantis, Endeavor and Discovery while an investigation is carried out.
Little cargo space
The new OSP will be launched using a rocket, and much like the current shuttle series, land like a plane upon its return to earth.
It will be smaller than the shuttle and be used to carry crews of at least four to the ISS.
There will be less emphasis on cargo payloads, although it will be able to carry cargo in an emergency.
The loss of Columbia has added pressure to the programme
It is planned that the OSP will be able to deliver injured or sick ISS crew members to "definitive medical care" within 24-hours.
The craft will be cheaper and easier to prepare than the current space shuttle, which takes a minimum of three to four months to ready for launch.
"The Orbital Space Plane system will give us the flexibility needed to safely and efficiently get crew to and from orbit and to provide crew rescue and logistical support to the International
Space Station," Nasa's deputy administrator Frederick Gregory said.
Under the newly released requirements the OSP must:
- Provide rescue capability for no less than four ISS crew members by 2010
- Provide transfer to the ISS for at least four crew members by 2012, at a higher safety rate than the current shuttle series
- Ensure the safe delivery of ill or injured ISS crew, with or without space suits, to medical facilities within 24-hours
- Provide for rapid separation from the ISS under emergency conditions
- Provide a safer lifeboat option than the current Soyuz craft
- Require less time to prepare and be cheaper than the current shuttle series.
- Have better orbit manoeuvrability
"These initial requirements help to outline a comprehensive system that will significantly complement the capabilities of our
existing Space Shuttle fleet," Mr Gregory said.
The OSP will ferry crews to the ISS
The programme to build a spacecraft to succeed the space shuttle series is called the Space Launch Initiative.
Nasa intends to spend $4.8bn over the next few years on the programme, with a new launch vehicle expected to go into production by 2006 and into service by 2010.
Last April Nasa announced that it had narrowed the number of possible concepts for the new vehicle to just 15.
President George W Bush has already asked the US Congress for about $1bn to fund the project - the request was made before the Columbia disaster.