Many happy returns
A re-usable lunar lander could be used for the Moon missions NASA plans to carry out from 2015 under President Bush's space plan.
The lander would operate between the Moon's surface and an orbiting space station, eliminating the need for a new vehicle for each Moon trip.
David Smith, Boeing's lead engineer for its Crew Exploration System (CES), said the vehicle could take four astronauts to the lunar surface.
The astronauts' spacecraft would be self-assembled in low earth orbit before travelling to the lunar space station, from where the crew would descend to the surface on the reusable excursion vehicle, arriving at an awaiting module where they will live.
Smith said that his team does not have a final design for the lander, as the question of whether or not to build a lunar space station has yet to be resolved.
But if a station is built, the astronauts, in space suits, could descend in an 'open' lander, rather like the Apollo excursion module trainer, he said.
'You could use something like the trainer if you had an orbiting lunar space station, and astronauts had the appropriate protection during transit. There's a whole bunch of approaches for the lunar landing vehicle, which would be a unique part [of the system].
'We're trying to use this common module approach to CES, and the lunar excursion vehicle could be more of a deviant from that than the others.'
The common module approach is central to Boeing's CES, which comprises a crew control module, crew living quarters module, resource module and an autonomous cargo vehicle.
These modules will travel to the Moon together as the Trans Lunar Insertion (TLI) vehicle, and then separate into an orbiting lunar space station and a Moon base.
The Moon-orbiting space station would be a warehouse for supplies needed by the Moon habitat module, which would arrive ahead of the astronauts. In the Apollo programme the lunar excursion module was also used as the living quarters module and was a closed, pressurised vehicle.
Another departure from the Apollo programme's approach is the decision not to use hydrogen and oxygen-powered fuel cells. Instead the Moon's space station and the TLI spacecraft will use solar arrays.
A faulty fuel cell caused the explosion on board the service module of Apollo 13, forcing the moon landing to be abandoned.
The new heavy lift Delta IV rocket will be used to launch all the modules into low earth orbit, from where the assembled spacecraft will go to the Moon.
The rocket, which will have its maiden launch this July, is capable of lifting 52,000lb (23,500kg) into low Earth orbit. The two engine systems needed for the TLI craft will require two Delta IV launches, while the TLI's resource and crew control modules would go up in a single launch.
Boeing and a consortium led by Lockheed Martin are in competition for the Moon technology contracts. Both companies had been working on the Orbital Space Plane.
This will now be replaced by a Crew Exploration Vehicle - the crew control module in Boeing's system.
Other vehicles and modules for the Moon missions will be ordered by NASA in due course. Boeing may have an advantage as it was the prime contractor for the Apollo programme and International Space Station. Many of the other companies that provided technology for Apollo are now part of Boeing.