Giant steps

Manned lunar bases are a mouthwatering prospect for scientists that could further our understanding of space and provide a springboard to Mars. Richard Fisher reports.

While the footprints of Neil Armstrong have remained quietly preserved on the lunar surface for 30 years, they may soon be erased in a flurry of activity, as the world’s space agencies get ready to return men to the moon within the next 15 years. But this time the plan is to stay there, and build an infrastructure that could lead to a fully fledged moon base.

Conceptual lunar bases have been on the drawing board since before Apollo. In 1959 the US Army produced a detailed technical design of a base, Project Horizon. But the concepts and academic papers have never been translated into hardware and funded programmes.

However, this has been a pivotal year, and the events of the past few months may decide who will plant their flag next. In the wake of president Bush’s January pledge to provide the funds to return to the moon and eventually head for Mars, the US aerospace heavyweights have been competing for a chance to develop the necessary spacecraft and technologies for NASA.

Meanwhile, ESA’s Smart-1 probe was due to begin its lunar orbit this week, kicking off the first return of detailed surface data to use for later missions, and ESA’s Aurora roadmap features the moon as a stepping stone to Mars. China has also said it intends to send an unmanned vehicle by 2010.

But NASA is leading the drive. In late September it awarded 11 aerospace groups six-month contracts worth a total of $54m (£29m) to develop plans and concepts for transport to the moon, orbiters and subsequent surface infrastructure.

Boeing, Northrop Grumman, Lockheed Martin and eight others including Orbital Sciences, Schafer and Raytheon presented their early ideas for spacecraft, orbital refuelling stations and bases, and are refining them before NASA calls for proposals early next year.

The agency is calling it Project Constellation and is planning an orbital ‘fly-off’ in 2008 to test the capability of each chosen group’s Crew Exploration Vehicle (CEV) – the replacement for the space shuttle. It is touted by many as the biggest contract NASA will hand out in the next five years, worth $5bn (£2.75bn).

NASA envisages three ‘spiral’ stages of development. With Spiral One the plan is to get the CEV into orbit by 2014, while Spiral Two’s aim is to send a small crew to stay on the lunar surface by 2018. But the ultimate goal, Spiral Three, is to consolidate a permanent base and explore the surface by around 2022.

Last week Boeing and Northrop Grumman announced they would collaborate on Project Constellation. Boeing, despite its space pedigree with Apollo and the International Space Station, will take a back seat to Northrop in the first stage of building the CEV. Chuck Allen, Boeing’s vice-president for space exploration systems, said the company wanted to concentrate on completion of the ISS and returning the space shuttle to flight, but will take over in the latter stages. Orbital Sciences and

Schafer said that they would like to work with others as part of a larger team, while Transformational Space and Lockheed Martin intend to present their own bids.

Lockheed Martin is the main competitor to the Boeing-Northrop collaboration, and the two groups offer divergent ideas. While Northrop’s concept is vague, Boeing’s idea of a refuelling ‘gateway’ station at the L1 Lagrange point, where earth and moon gravity is equal, contrasts with Lockheed’s proposal to travel directly from earth orbit to lunar orbit.

Keith Reiley, lead systems engineer for Boeing Exploration, said that there are many advantages to a station at L1. ‘Because you’re at L1 you can land anywhere on the moon,’ he said. ‘Later on we plan to establish a refuelling station there, allowing other parties to collaborate and not crowd the critical path to the moon. You could also scavenge and store unused fuel there.’

Boeing’s moon lander could be used by other groups to move back and forth between the moon and L1. ‘We’re putting in gateways to allow commercial groups or other space agencies to contribute by providing logistics at certain stages,’ said Reiley. ‘NASA could have the option of buying fuel by the kilogram and have it delivered by a commercial company to L1 or low-Earth orbit.’ However, Lockheed argues that it would be cheaper and easier simply to adopt a more direct approach.

John Stevens, director for space exploration architecture studies at Lockheed Martin Space Systems, said that his team plans to assemble the parts of the CEV and lander in Earth orbit and then travel from there.

‘We are using an approach much like Apollo, travelling from low-Earth-orbit to a lunar orbit. We’ve found it’s more efficient to do that in terms of mass,’ he said.

A further difference in opinion has emerged in the choice of location for the base. While Lockheed proposes a permanent base at the equator, Boeing envisages an outpost at the south pole. Each site has its own set of engineering challenges. At the equator the outpost would have to cope with temperatures from around -150°C at night to 110°C in the day.

Plus the equatorial night lasts around 14 days, so a base would have to be powered by nuclear generators, or at least need a way to store solar energy.

The pole is the preferred option for many groups, not just Boeing. ESA’s Prof Bernard Foing, Smart-1 lead scientist, said that the poles are better in terms of resources as well as power supply. ‘They have reserves of water in ice,’ he said. ‘There are regions of the poles that see the sun all year long, and stay stable at about -20°C. You could have constant solar power. And also you can see the Earth at all times.’

But despite the poles’ potential for solar power, Boeing is planning to use nuclear energy. And Lockheed said that, while its early missions will use solar power alongside fuel cell storage, it is likely that it will also eventually have a more robust nuclear power source.

Meanwhile, Stevens suggested that finding a suitable location for a permanent base at the pole may prove difficult. ‘There are some locations where the sun shines 80 per cent of the time, but in the shadowed areas where we want to explore for hydrogen resources, it can be down to -220°C. It will be difficult to send people there,’ he said. ‘The nice thing about an equatorial base is that it directly faces Earth and you can escape from the surface fairly readily.’

Equatorial bases could also offer more interesting science and would be a better location for astronomical investigations. The long day-night cycle problem at the equator is also an issue exploration teams will need to contend with on Mars, added Stevens.

Boeing wants to mine ice at the pole to generate fuel, leading to a filling station at L1 that could fuel spacecraft to travel elsewhere in the solar system. ‘The fuel that we suggested in our option is cryogenic hydrogen-oxygen, which could be easily manufactured on the moon if we find ice,’ said Reiley.

Lockheed plans to set up a large-scale resource production facility at the equator to exploit the materials there, and go on expeditions to the poles for hydrogen. ‘First we will produce oxygen, which is readily available from minerals,’ said Stevens. ‘Second, we would get hydrogen from the poles, and third we would produce nitrogen as a by-product of oxygen. Once you have these, you have constituents for air and water for life support, as well as propellants.’

NASA researchers are separately investigating the potential of a roving lunar base on legs or wheels that could settle the pole/equator debate. Dr Marc Cohen, head of the Habot Project, told The Engineer that with funds the technology could meet the deadline for a manned return to the moon.

Meanwhile, Lockheed and the Boeing-Northrop collaboration is investigating possible designs for bases. At first a lunar outpost will likely consist of interconnected habitation modules, as constituents of the lander or as inflatable structures, with remote solar or nuclear power sources and landing sites a few kilometres away.

Lockheed aims to pioneer its lunar operations using robotic rovers radiating thousands of miles from its equatorial base as early as 2010. These would explore the surface controlled from Earth or acting autonomously years before astronauts arrived around 2018, and could find the best place to land, optimising the time spent on manned missions, said Stevens.

‘Our first outpost would consist of a habitation module, with small bulldozers for trenching work and to shift lunar regolith (slabs of moon rock) around,’ he added. ‘Every time you bring a new habitat you could plug it into existing architecture. It would have similar aspects to the space station but some parts would be buried under regolith to protect from radiation.’

Any outpost will need shielding technologies to protect astronauts and electronics from harmful galactic and solar radiation. A number of teams are working on more efficient ways to protect outposts in future, for example electrostatic shields, as The Engineer reported last month.

There are a number of other technological challenges, according to Boeing’s Reiley. ‘You need a logistics system that is simple and efficient – providing spares, food and water that isn’t too expensive,’ he said. ‘Other issues include coping with lunar dust and how you deal with it over an extended time where it can build up.’

A key factor still undecided is the launcher size, which will greatly influence the eventual lunar architecture. The view in the lunar base community is that a heavy-lift launcher is necessary, but today there are no launchers of this size in service and NASA has yet to commit to developing one. Dr Peter Eckart, author of The Lunar Base Handbook, said today’s only option, the space shuttle, is simply insufficient.

‘The space shuttle only gets around 20 tonnes into low-Earth orbit, which means virtually nothing to the lunar surface, maybe a couple of hundred kilos, maybe a tonne,’ he said. ‘If we’re really serious about pursuing an exploration programme to the moon and Mars we need a launch system capable of bringing 100t into low-Earth orbit. The ISS is a disaster because we don’t have that capability – they’re talking about not finishing it and it’s all due to the fact that there isn’t the appropriate launcher.’

All aerospace groups are hedging their bets until NASA makes a decision, with their proposals taking into account heavy-lift launchers or medium-lift (around 40-60t) with a multi-stage assembly in orbit. NASA has undergone an extensive reorganisation over the past few months as part of the new exploration vision, but the dust has yet to settle and it is unsure how the lunar programme will develop.

President Bush has remained quiet on the issue of funding since January, and while the ISS is absorbing a large chunk of NASA’s budget there will be little free cash to pursue extensive lunar programmes. Once ISS is completed – and providing its political paymasters give the go-ahead – NASA could be in a position to put Project Constellation into top gear.

This year has seen small but significant steps towards a return to the Moon – the giant leap will surely come.


Why return to the moon?

The key justification is to use the moon as both a stepping stone to Mars and as a platform to develop the necessary technologies. Astronauts could practise long-term isolation, landers and rovers could be refined and the reliability ofequipment could be proved.

However, whether a permanent base should be built is widely debated because of the huge costs. So most agree that a stepwise approach is best. Dr Peter Eckart, author of The Lunar Base Handbook, said that unlike the Apollo landing, the reasons for staying are complex. ‘This time it is a different question. I don’t think the “why” question has been convincingly answered. Each reason I have heard is nice but none carries the weight of a clear justification.’

Dr Wendell Mendell, manager of NASA’s office for human exploration science at Johnson Space Centre, said that NASA needs to look beyond using the moon as a technology testbed for Mars missions. ‘NASA’s interest seems to be transient. The assets we develop on the moon may be abandoned, but in reality what we learn there should be utilised rather than left to rot,’ he said. ‘NASA requires an exit strategy that needs to be defined at the very beginning and it should partner with someone with a long-term interest in the moon.’

From an academic point of view the construction of a permanent base could offer researchers insights into how the moon and rocky planets like Earth formed, and allow better astronomical observation. Many also believe the moon has commercial potential, either for tourism or to be mined for resources, such as oxygen or hydrogen that could be used for life support or spacecraft propellant to send missions further into the solar system.

So if a permanent lunar base is to justify itself, a joint effort between industry, space agencies and governments will be needed.</b>