BRAND-new moon shot, brand-new technology – right? You may be looking forward to ground-breaking, futuristic spacecraft and hardware, but the reality will almost certainly be much more prosaic. For reasons of safety and cost, NASA is looking to go retro, reviving and updating 1960s concepts to get people to the moon and back, and thumbing through old blueprints for ways to provide lunar settlers with shelter.
NASA won’t decide on the specifics of this latest moon shot for some time. “I think we’ve got to avoid getting fond of a design,” said NASA administrator Sean O’Keefe soon after Bush’s announcement. But the basic options for a future mission appear to be mapped out, and one thing is clear: NASA’s existing space infrastructure isn’t going to be any use.
At first glance it might seem sensible to use the international space station and the space shuttles as stepping stones to the moon. The moon-bound crew would first hop to the ISS on the shuttle, and then board a hypothetical lunar shuttle to take them into lunar orbit, before taking a landing craft to the moon’s surface. Unfortunately this wouldn’t work, says Robert Strong, director of the Near Earth Object Foundation and the Sir Arthur C. Clarke NEO Observatory in Wheeling, West Virginia. “The ISS is in the wrong orbit for going to the moon,” he says. “It is not a way station to the moon, Mars and beyond. Politics gave us the ISS with no destination beyond itself.”
Advertisement
The problem is that its orbit is tilted relative to the Earth’s equator to make it accessible to Soyuz capsules launched from the Baikonur cosmodrome in Kazakhstan. The moon, however, orbits roughly around the Earth’s equator. It would be possible to change the ISS’s orbit to put the moon within reach, but that would stop the Russians reaching the station.
Hence the need for new designs – or rather, old ones. According to numerous space experts, NASA’s best option for a moon mission and beyond is to revive ideas used in the Apollo missions of the 1960s and 1970s.
In other words, going back to expendable, modular capsules. 91ɫƬators believe that the crew exploration vehicle (CEV), the new manned spacecraft announced by Bush, will probably be an expendable craft similar to the Apollo command and service module of the late 1960s (see Graphic). NASA contractors have already started designing expendable capsules to take crew to the ISS, and the concept won support from Congress after the Columbia disaster.
Like the command and service modules, the CEV would be launched into low-Earth orbit on top of a rocket, and at the end of the mission the remaining section of it would re-enter Earth’s atmosphere and splash down into the ocean (see “Blast from the past”). For a mission to the moon, the CEV could simply be fitted with a detachable lunar module to take astronauts down to the lunar surface and back again, plus the engines necessary to push it from Earth orbit into lunar orbit.
But NASA sees the CEV as more than just a craft to ferry astronauts to the moon and back. With different rocketry and landing modules, the core vehicle could equally well carry people to the space station, Mars (see “Destination Mars”), or any other destination beyond Earth orbit, such as an asteroid. Although NASA says no firm decision has been taken on the design, and hasn’t ruled out developing a reusable craft rather than an expendable one, a spokesman confirmed that the agency would be looking at technologies developed in the past. “But we won’t be confining ourselves to those”, he added.
Whatever the final design, NASA will have to make some pretty snappy decisions. The CEV will be built and tested in unmanned flight by 2008, according to NASA administrator Sean O’Keefe, and should be ready for a manned mission by 2014.
One upshot of the CEV programme is that it would displace the proposed orbital space plane, which was announced in November 2002. The space plane was envisioned as a successor to the shuttles and would have provided transport to and from the ISS. The CEV would render this vision obsolete, though the development work that has already been done on the space plane will become part of the CEV programme.
But why go back to the Apollo configuration? The simple answer is that it worked, and safely. The colossal Saturn V rocket that launched the missions off Earth had a success rate of 10 out of 10. The Apollo command module, which housed the crew, was separate from the service module that contained the engine. This is what allowed the Apollo 13 astronauts to survive the explosion in their service module. The Apollo capsule also had its own escape rocket, which would have instantly propelled the command module and crew to safety if a Saturn rocket had exploded during blast-off. And the capsule was safer than the shuttle on re-entry. “Why reinvent a wheel that was so well planned and worked so well?” asks Strong.
The shuttle, in contrast, houses crew and engines together, and is surrounded by its booster tanks at take-off. This makes it an extremely dangerous place to be if the fuel tanks explode, as they did in the 1986 Challenger disaster. The shuttle’s only escape route is a pole that can be deployed outside the main entry hatch, allowing astronauts to slide to safety in the event of an emergency – clearly not much use after lift-off.
As for the rocketry in this latest moon shot, NASA is again harking back to the tried-and-tested Saturn V rocket, whose payload of 118 tonnes makes it the most powerful rocket ever built. However, a modern moon rocket won’t be quite the same as the model of 40 years ago. Although it will be liquid-fuelled like its predecessor, Strong says it will probably use “new rocket motors, hybrid fuels, and myriad technologies undreamed by the Apollo designers a half a century past”. And the old aluminium structure could be replaced by lighter, stronger composites.
But Saturn V may not be so easy to reinvent, according to David Miller, an aerospace expert at the University of Oklahoma. “The Saturn V was designed in the early 1960s, and my guess is that there are no readily accessible plans – and certainly not in any kind of format that we could make use of,” he says. Also, Miller adds, Saturn V’s designers are either long-retired or dead. “We don’t have the set of experienced rocket engineers we had at that time.”
NASA does have a couple of alternatives, however. One is a heavy-lift version of the space shuttle known as Shuttle C, which was proposed in 1984 but never built. It would be able to hoist a 68-tonne payload into low- Earth orbit, compared with 25 tonnes for a standard shuttle. That larger payload could conceivably consist of a CEV and all the other paraphernalia needed for a moon landing, plus the engines necessary to push these from Earth orbit into lunar orbit.
Also under consideration is the idea of building a craft in space, or “Earth-orbit rendezvous”, as NASA calls it. In this scenario, a fleet of off-the-shelf rockets such as Boeing Delta IVs or Lockheed Martin Atlas Vs would send the necessary components for a moon voyage into low-Earth orbit. Once there, astronauts would assemble the craft for blast-off to the moon.
Earth-orbit rendezvous was considered by NASA in 1962 but rejected as too dangerous and time-consuming. Building a ship in orbit would mean constructing a space station to work from, and then making multiple space walks, which hadn’t even been attempted back then. Now, though, the rendezvous plan is a distinct possibility. “In the past 40 years we’ve learned a lot about rendezvous, docking and assembly,” says Brian Chase, executive director of the National Space Society, a Washington DC-based lobby group.
Assuming we can successfully send settlers to the moon, what then? They would have to live in some kind of semi-permanent housing, possibly for months on end, with supplies shipped from Earth. Constructing such a habitat poses serious challenges. Temperatures on the moon range from 100 °C at midday to −150 °C at night. Gravity is one-sixth of Earth’s and radiation levels are dangerously high. And, of course, it is utterly airless. Earth’s nearest celestial neighbour would be the most hostile environment ever settled by humans.
A settlement wouldn’t be built until 2015 at the earliest, but prototypes have already been designed and built. TransHab is a multi-storey inflatable habitat shaped like a giant bagel which provides accommodation for up to six astronauts. It was designed by Lockheed Martin in the 1990s as a crew compartment for the ISS, or possibly a module for a hypothetical Mars-bound spacecraft. At least three prototypes were built. These had several outer layers, including one of Kevlar, the same material used in bulletproof vests.
Although the project was cancelled after work began on the ISS, TransHab has obvious benefits as a lunar habitat. It can be can folded away and stowed for easy transport to the moon, and once inflated it would be tough enough to protect its residents from meteoroids and radiation. And according to Miller, additional TransHabs could be sent up and connected to one another to allow the colony to expand. The complex could also be made more permanent by covering the modules with lunar soil.
Supplying the colony would be the hardest part. “Basically, we can’t make anything on the moon,” says Louis Friedman, executive director of the Planetary Society in Pasadena, California. That means a steady stream of supply ships from Earth. But lunar residents will eventually have to become self-sufficient (see “Gas, food, lodging”).
There are myriad other hurdles to overcome. For one thing, the capacity of an Apollo-size capsule is three, which probably won’t be enough for an extended lunar mission. Experience on the Mir space station and the ISS indicates that a small crew would be kept busy repairing and maintaining the habitat and have virtually no time to do anything else. What’s more, NASA has performed training simulations in cold, remote places, and found that when it comes to long periods of isolation, more is merrier. “The larger the group the better, from the point of view of sanity,” Miller adds.
Whatever the fine details, reviving tried-and-tested ideas seems to be the key philosophy. And if NASA is to turn the vision into a reality, there’s one old idea it probably needs above any other. Can the agency rediscover The Right Stuff?
Blast from the past
What might a 21st-century mission to the moon look like? If it’s anything like the Apollo lunar missions of the 1960s and 70s, it will probably use a concept called lunar-orbit rendezvous. Here’s how it worked.
A three-stage, liquid-fuelled Saturn V rocket blasted off carrying the crew and modules, burning the first two stages and part of the third just to reach low-Earth orbit. Once everything was checked and OK’d the third stage then reignited and propelled the cargo – the command and service modules, three-member crew and lunar module – out of Earth orbit and onto a trajectory towards the moon, 384,000 kilometres away.
En route the astronauts jettisoned the rocket’s third stage. Once in lunar orbit, two astronauts crawled inside the two-stage lunar lander and descended to the moon’s surface, leaving a single astronaut to orbit in the command and service module. When the moonwalking pair had finished they blasted off in the lunar module’s upper portion, leaving the base of the lander behind, and docked with the command and service module in lunar orbit.
The trio then jettisoned the remainder of the lunar module and blasted off for home. A couple of days later they entered Earth orbit, discarded the service module and re-entered the atmosphere inside the command module. That final section splashed down in the Pacific Ocean, where an aircraft carrier plucked it from the sea. Of the 110 metres of rocket that blasted off from Cape Canaveral around a week before, less than 4 metres came back.
All of this technology is now obsolete. But it looks as though it is due for a comeback. Phil Scott
Gas, food, lodging
Would you eat tomatoes grown in a vat of urine? Long-term residents of a moon base may have to get used to the idea. And that’s not all. They may also have to learn to like blue food, and drink water that they know for sure has already passed through them several times.
Building a self-sufficient life-support system is an absolute must for long-term manned missions to the moon. Although food could initially be carried up on regular service missions, experts agree that if the moon base is to last more than 18 months, shipping supplies will become too expensive. This means building a colony that, once established, needs little or no external input. The basics – water, breathable air, energy and food – will have to come from the local environment, and as much waste as possible will have to be recycled.
Assuming there’s water on the moon the first three will be relatively easy. But growing food is not.
One thing is clear: moon residents will have to give up meat. “We’re not going to take pigs, cows or chickens up with us. You’re going to be a vegetarian whether you like it or not,” says Mike Dixon at University of Guelph in Ontario, Canada, who is sponsored by the European Space Agency to study potential foods for manned missions.
Crops will obviously require a greenhouse of some kind, but no one knows whether moon dust contains enough nutrients to grow plants in. So hydroponic systems in which the crops’ roots sit in a fluid bath are the most likely option. To this end, Russian scientist Alexander Tikhomirov is breeding plants that can grow in more or less untreated urine. Other researchers are exploring the potential of growing crops in dried faeces.
Dixon believes that genetic modification will be crucial to growing crops successfully in space. “We’re not getting off the planet without GMOs,” he says. But it’s not the reduction in gravity that the plants need help coping with. It is the crops’ pressure and temperature sensitivity that must be adjusted. “Conventional products will not produce adequate harvests. They won’t like it enough. We are modifying them for pressure sensitivities and reduced energy requirements,” he says.
One novelty in the astronauts’ diet might be blue-green algae, which is easy to grow and highly nutritious – 60 per cent protein, compared with 40 per cent in soya beans. “We are comparing harvesting technologies and recipes for several varieties of blue-green algae,” says Christophe Lasseur, head of life support systems at ESTEC, the European Space Agency’s research centre in Noordwijk, the Netherlands. “It could be eaten raw in a salad, or cooked like flour.” But Dixon is sceptical it will catch on with the crew. “Psychologically it sucks. Have you ever eaten a blue-green burger? You’ll drive the crew round the bend,” he says. “As a last-ditch survival solution maybe, but I don’t think you can put enough salt on a blue-green algae burger to make it palatable.”
On the ISS water is already recycled to drinking standard. “But for psychological reasons we send up drinking water instead,” says Marc Heppener, head of the ISS research division at the European Space Agency. But cosmonauts on MIR had to drink recycled water, and it seems that moon astronauts wouldn’t have any choice either. David Cohen
