There are few engineers who wouldn’t relish the chance to design the spacecraft that could take people to the Moon for the first time in decades, and then on to Mars.
After spending 19 years investigating the problems of conquering space, David Smith, Boeing’s exploration concepts lead engineer at the aerospace giant’s famous Phantom Works, has been given the job of his life. Boeing has just released its concepts for meeting President Bush’s ambitious space plans, known as Project Constellation.
Smith’s team developed the design concepts for the Crew Exploration System (CES) which Boeing hopes will be adopted by NASA to make those plansa reality.
Discussing the new era of manned space flight that could lie ahead, Smith sets out a vision of building, stage by stage, an infrastructure that will serve our ambitions for many years ahead.
It also becomes clear that space exploration’s past, present and future are inextricably linked, forming a connection from the triumphs of the first Apollo Moon landings to the more recent shuttle tragedies.
Smith’s career began after Apollo ended. To many in the space industry, after the Challenger and Columbia shuttle disasters and the continuing wrangling over the International Space Station, the prospects for manned space flight seemed grim. But Constellation with its modular approach is a new opportunity for space engineers.
‘For me personally it’s great,’ said Smith. ‘It’s in contrast to the previous great political goals of having a space station or going to the Moon in one fell swoop. It enables us to establish an infrastructure to last. As an engineer it’s exciting to know that we can actually now do it the way we would like to do it.’
Smith happily admits that his own company and NASA take advice from former Apollo programme engineers. Boeing even has engineers from the first lunar project still on its payroll. For example, a former Saturn rocket designer is now implementation manager for Boeing’s Orbital Space Plane (OSP) work, and NASA brought in some Apollo veterans specifically to look at its OSP plans.
‘Our current approach is very Apollo-like,’ said Smith. ‘We are certainly re-using the operational approach. In fact, [for the OSP capsule] we’ve looked at a lot of the Apollo drawings, for instance how the capsule was attached to the service module.’
Of course, in most respects the current engineers are operating in a vastly different landscape, with access to technologies that their forebears could only dream of. ‘The computer technology is so enhanced now that your digital watch is probably smarter than the original computer on Apollo,’ said Smith.
They also face some very different challenges. Unlike Apollo, the new generation of spacecraft will not be disposable, single-use vehicles. For example, in the cargo vehicle that forms one of the craft within the CES concept an ablative heat shield is being considered. Such a shield erodes slowly due to the heat of re-entry, and could either be used on a craft with an entirely replaceable shield or one that was designed to re-enter the Earth’s atmospheres a limited number of times.
This idea of limited reusability fits in with the long-held goal of the space community of reducing costs by not having to build a new vehicle or rocket for every mission. Another big difference from the 1960s approach is the decision to use solar arrays instead of fuel cells. Thankfully, there are ‘off-the-shelf’ technologies that have been used for years on the Shuttle and International Space Station (ISS). Smith and his colleagues will benefit from these in meeting the challenges of Constellation.
‘There’s the computing infrastructure, the data, the avionics boxes, the power systems and the environmental control systems. In fact, for the cargo vehicle side there is very little new development required for most of the sub-system infrastructure because it’s already been brought to state of the art with the ISS.’The challenge now will be to get that equipment, originally designed for low-Earth orbit, to operate deeper into space.
‘Maybe we’re going to be running it longer, or in a different kind of environment with more radiation or colder because we’re not close to Earth,’ said Smith. ‘But the basic infrastructure has already been established by ISS and Shuttle.’
If the technology will be different, at least the road to the Moon is one well trodden by Apollo. ‘The springboard will be similar to Apollo,’ said Smith. ‘Most of our rendezvousing and proximity operations will be done in low-Earth orbit, where you establish the basic vehicle and then travel to the Moon.’
However, establishing that vehicle and getting the modules into orbit will require new rockets. Boeing has just released images of its new Delta IV heavy-variant rocket, which has three boosters and is due for launch in July. The booster design is from Boeing’s existing Delta IV medium version, launched successfully last year. Could it do the job?
‘The Delta IV Heavy, as it is today, is maybe sufficient,’ said Smith. ‘But to go to the Moon I think you’d certainly want to increase your heavy capability. We know that the current Delta IV Heavy can be made more efficient, and could carry significantly more without having to add more boosters. To go to Mars you might need a new rocket altogether.’
The rockets will need all the capability they can muster, because for CES they will have to place into orbit the crew control module, crew habitat module, resource module and the autonomous cargo vehicle. The rocket can carry 23,000kg into low-Earth orbit and none of the CES modules, individually, are heavier than that.
However, three Delta IV flights will be required to install the constituent parts of the trans-lunar insertion (TLI) vehicle into low-Earth orbit: one for each of the two engines, and a third for the crew and resource modules. Smith would like to see that number reduced with better rockets.
‘The goal is to minimise the number of flights to assemble this vehicle,’ he said. ‘That [three launches] is the starting point and we hope to do better. So you would build a TLI stage in orbit. That would take either your crew vehicle or your cargo vehicle directly from low-Earth orbit to either the L1 point or a lunar orbit’.
The L1 point is also known as the Langrange point. This is a location in space between the Earth’s and Moon’s gravitational forces where an object can stay in position without the need for thrusters to counter the pull of either. The L1 point could be important in any future Mars mission, allowing a huge spacecraft to be constructed in space for the long trip to the red planet.
For the more immediate Moon mission, Smith’s team is pondering the benefits of a lunar space station in terms of getting people down to the Moon. Under this scenario, Smith conceives a lunar lander ‘excursion’ vehicle that simply sorties between the surface of the Moon and the orbiting station. Another vehicle would take the crew back to Earth or low-Earth orbit. The reusable excursion module is yet to be designed.
The lander would take the crew down to lunar living quarters that are waiting for them on the surface. The living quarters module would have just enough rocket power to land once. It would be a variant of the cargo vehicle with an inflatable section in which astronauts would live temporarily. It is not designed to be a permanent base.
A permanent Moon base may come, and that will present a whole set of new problems for engineers to overcome. Smith has enough on his plate getting people there, but can’t wait for the challenge to begin.