To Boldly Go ... Bush Tells Nasa to Build New Shuttle for Mars

President George Bush yesterday unveiled plans to replace the ageing space shuttle with a Nasa spacecraft designed for manned missions to Mars as well as the moon.

The craft, known as the Crew Exploration Vehicle (CEV), would be ready by 2015, and by 2020 would take astronauts to the moon to build a manned station, according to a new presidential directive to the US space agency.

The mission to Mars would come 10 years later. Meanwhile, the red planet will continue to be explored by robots, following the Spirit rover which was due to embark on a trip across the Mars surface last night in search of signs of water.

Speaking at Nasa HQ in Washington yesterday, President Bush said: "Today we set a new course for America's space project ... We will build new ships to carry man forward into the universe to gain a foothold on the moon and prepare for new journeys to worlds beyond our own."

While work is underway on the CEV and on a new generation of rockets to take it into deep space, the shuttle programme will be phased out. It will continue to ferry people and supplies to the International Space Station orbiting the earth.

But once the station has been completed over the next five to six years, and the US fulfils its obligations to its 15 partner nations in the project, the three surviving shuttles will be retired. The savings from the shuttle programme would be channelled to the CEV. Meanwhile, it will be developed with incremental increases to Nasa's existing $15bn budget. One billion dollars will be added next year, an extra $12bn over the coming five years.

It is not yet clear what the CEV would look like. Some proposals envisage another reusable craft with wings like the shuttle. Others would return to the single-use capsules that first took people into space. "It is going to look totally different to what the space shuttle looks like today," Sean O'Keefe, head of Nasa, told CNN. "So we have to get about the business of developing that capability right away."

He said the new craft would be a robust, modular system, which could be tailored to suit the ambitions and budgets of future exploration plans.

Critics allege that it is little more than a stunt, aimed at an election year. They point out Mr Bush's father also announced a Mars mission when president in 1989, but the scheme was rejected by Congress when Nasa priced it at $400bn. The tag on the new initiative is considerably less, but space experts argue that, even with savings from the shuttle and space station, the budget is unrealistic. "The first year after Kennedy announced the Apollo programme, the Nasa budget was doubled," said Senator Bill Nelson, a former astronaut. "And in the second year it was doubled again. That's not realistic today. But 5% a year increases are not going to get us to the moon."

Mr O'Keefe said the budgeted increases were only intended as seed money to develop concepts, but the project would signify a more ambitious phase for manned exploration, limited to low earth orbit since the last visit to the moon, the 1972 Apollo 17 mission. "I think what the president has touched on is an important aspect of what is part of our human makeup - which is to be explorers," the Nasa administrator said. "It is part of what defines great nations and great objectives."

The Bush plan could leave a gap of up to five years after retirement of the shuttle and before the CEV was ready, during which Nasa would have no manned craft. There was a similar, nine-year gap between the end of the Apollo programme and the launch of the shuttle in 1981. Nasa officials said the Bush initiative came from the investigation of the Columbia crash last February, which focused scrutiny on the longevity of the fleet and what should replace it. Nasa released a number of conceptual designs at the end of last year.