NASA has unveiled full details of their plan to send astronauts to the Moon and Mars. The Agency says it will spend US$104 billion to put humans back on the Moon by 2018. The first trip will send four astronauts to the lunar surface for a seven-day visit. That's much more ambitious than previous Apollo missions, during which two astronauts spent up to three days on the Moon.

"Think of it as Apollo on steroids," says NASA chief Mike Griffin, who presented the Exploration Systems Architecture Study to White House officials on 14 September, and to the wider public today.

Although President George W. Bush outlined his 'Vision for Space Exploration' on 14 January 2004 in very broad terms, this study pins down how NASA will actually make the vision work on a realistic budget.

Observers were most interested in the details revealed today for the new Crew Exploration Vehicle (CEV), which will be NASA's flagship once the Shuttle fleet retires in 2010.

Two aerospace consortia are working on proposals for this craft: Lockheed Martin Corporation lead one group, and the Northrop Grumman Corporation and Boeing head the other. Both teams will now tweak their early CEV designs to fit the detailed requirements unveiled by NASA. A final design will be chosen in early 2006.

Bigger and better

The CEV will look like a larger version of the Apollo craft, with a cone-shaped command module that will carry astronauts safely back to Earth using parachutes, rather than gliding in like the shuttle. It will sport solar panels for power while it is in space, and its engines will burn a mixture of liquid methane and liquid oxygen. Previous craft have burned other liquid fuels, but experts hope that methane and oxygen might one day be harvested from other worlds or moons for refuelling.

Each craft should be able to make five to ten trips before being retired, says Griffin, and they should be abut ten times safer than the space shuttle system. This is because the CEV will sit on top of a modified solid rocket booster, keeping the astronauts well out of the way of any falling debris. It will also boast an 'escape tower' that should allow the crew to bail out in the event of a launch failure.

The craft should be ready by 2012, and will initially ferry up to six astronauts to and from the International Space Station. An unmanned version of the CEV could also be used to deliver cargo.

But getting to the Moon will be slightly more complicated. NASA plans to first haul a heavy load of a lunar lander and accompanying rocket into orbit around the Earth. This requires them to start working on new engines capable of hauling this 125 tonne load. Astronauts would then use the lighter CEV to get up to the lunar lander, and use the rocket to cart them to the Moon. Then, as in the Apollo missions, they would leave the CEV to make the descent to the surface. After their week's stay, astronauts would then return to the CEV for their journey home to Earth.

Moonwalking

The mission plan aims to leave as much equipment on the lunar surface as possible, to help build future Moon bases. It also allows access to anywhere on the Moon, unlike the Apollo missions that were restricted to equatorial regions.

This means that astronauts could explore the Moon's poles, where water ice probably nestles in shadowed craters. Exploiting the Moon's natural resources is essential if NASA is to have a permanently manned base there. Once the programme is up and running, Griffin anticipates two Moon mission each year.

"We didn't set out to make this look like Apollo," says Griffin. The marked similarities between the missions "demonstrate that by and large the Apollo folk got it right," he says.

Griffin also insists that the project does not require any extra cash beyond the normal NASA budget. "This is not about taking money from the science programme for human spaceflight," he adds.