The bittersweet episode at NASA a few months ago, which saw the Space Shuttle triumphantly return to flight only to be immediately grounded again amid further concerns about safety, has reopened debate about the value of the American manned space program. The binary black holes for NASA budget dollars that are the Space Shuttle and the International Space Station, are set to be exacerbated by the additional imposition of President Bush’s “Renewed Spirit of Discovery” plan for manned missions to the Moon and Mars.
Bush’s plan, outlined in the Vision for Space Exploration, entails three main steps. The first is to complete the International Space Station as soon as possible, with a deadline of 2010. At this stage, the Space Shuttle will be retired. It will be replaced by a newly-developed Crew Exploration Vehicle, which is to be designed by 2008 and operational by 2014, the second key principle. Thirdly, and perhaps most importantly, the plan advocates the use of the CEV to conduct manned missions to the Moon and Mars.
The plan has received mixed reactions from the scientific and spaceflight community, perhaps mainly because it does not allocate a significantly increased budget to NASA to match the agency’s greatly expanded goals. Most of the funding will instead be stripped from unmanned science programs such as Beyond Einstein, a series of probes designed to test several theories of cosmology. The news that NASA would no longer service the Hubble Space Telescope, which has provided invaluable data to astronomers for many years, only served to heighten the sense among many scientists that a new emphasis on manned flight is going to come at too great a cost. In a recent issue of New Scientist (Vol.187 No. 2513, p.21), Michael Le Page argues that whatever benefits they may have, manned interplanetary missions are simply not worth “cancelling dozens of missions to more exotic and intriguing destinations [or] losing more space-based observatories in the mould of Hubble … Science and exploration are the big losers.”
Before the merit of the plan can be decided, however, it is necessary to determine exactly what the space program should achieve. Unmanned space observatories like Hubble may be of immense importance to astronomy, but have little direct impact on most of humankind. Probes to help us determine the nature of black holes and distant galaxies are valuable if we aim to accumulate knowledge for its own sake, but less so if the space program is primarily designed to assist people back on Earth. As long as missions are taxpayer-funded, it would seem sensible that they should be providing some sort of direct benefit to those citizens. But this is not necessarily an endorsement of the Vision over the current use of unmanned probes as NASA’s prime tool for exploration. It is not clear that dollar-for-dollar, manned missions provide much more public utility (including scientific knowledge) than unmanned ones. Indeed, some have suggested that the manned space program is really little more than a public relations exercise, designed to give the American public a sense of nationalistic adventure and excitement so that they will continue to support allocating budget dollars to space – and the more scientifically useful unmanned missions.
So do we need a manned space program? Does that program need to send humans to the Moon or Mars, or is the current emphasis on Earth orbit sufficient to yield the most cost-effective provision of useful knowledge? For a start, it would seem that we will have to revisit the Moon one day. The advantages of establishing a permanent presence on the Moon are too great to ignore. The low-gravity, complete-vacuum environment is likely to enable the production of many new materials, aided by the plentiful raw materials of the lunar surface. There are vast expanses of land for solar energy collection, undimmed by clouds and, for some polar regions, permanently in sunshine. Using electromagnetic rail guns to launch manufactured products (such as space station modules) from the surface of the Moon into Earth orbit is also far more efficient than launching them by rocket from Earth. Additionally, the dark side of the Moon would be an excellent venue for conducting radio astronomy, because of the lack of atmosphere, clouds and radio interference.
These tasks cannot all be performed by unmanned robots, so at some stage we will have to return to the Moon. Is there an advantage in waiting? Not unless the pace of development in artificial intelligence speeds up markedly in the near future. In all cases, it makes sense to extract the benefits the Moon can bring as soon as possible, because they will reduce the cost of future space infrastructure. Unless we develop much smarter robots soon, which would mean there is a less compelling case for sending humans, that means manned missions are a necessity.
One aspect of the plan which has drawn less opposition is the retirement of the Space Shuttle. Most within the spaceflight community seem to recognise that the Shuttle, despite being an impressive work of engineering and design, failed to live up to its promises of high reusability and low expense; additionally, it is also increasingly unsafe for the astronauts that travel in it. A possible root cause for the Shuttle’s inefficiency is that it attempts to be a general-purpose vehicle – aiming to carry out satellite launches, crew transfers, and space-based experiments. Trying to fulfil all of these different uses, it achieves none of them optimally.
For satellite launches, the reason for failure is that satellites do not necessitate a reusable craft that can re-enter the Earth’s atmosphere. The Shuttle provides extra functionality that is not required, and does so at the cost of extra weight, fuel and expense. There is little point in hoisting a 109-ton shuttle to orbit, using a 750-ton fuel tank, just to place a 30-ton satellite there. This is why most of the world’s satellite launch business has been poached by the European Space Agency’s unmanned Ariane rockets, whose lower running costs enable lower prices to be charged of the customer. It would seem that launching satellites or space station modules to orbit would be much better accomplished with unmanned rockets than with the shuttle. Crew transfer is a field that obviously requires a more complex, safe vehicle than a satellite launch rocket. But within the parameters of reentry-capable craft, there is much more room for specialisation than exists with the Shuttle. By eliminating unneeded segments such as the Canadian arm, a vehicle designed solely for ferrying astronauts could be made much lighter than the Shuttle. Consequently, it would use less fuel and thus be cheaper. This search for a more efficient personnel transfer craft seems to be the main rationale for the development of the CEV. Additionally, the ongoing success of private efforts to develop reusable spacecraft, such as the entrants to the X-Prize and its winner SpaceShipOne, is proof that alternative crew launch vessels can be more successful than the Shuttle.
Finally, in terms of providing a platform for conducting space-based experiments, the Shuttle’s time is coming to an end. The completion of the International Space Station will provide a permanent platform for conducting science in microgravity. Despite the budget blowouts that have attended its construction, the ISS will be scientifically valuable and largely eliminate any role the Shuttle might have in this field. Additionally, it may become increasingly possible to send the experiments up in unmanned craft, and conduct them from the ground, using remote control. This would enable the researchers to carry out their own experiment, rather than providing instructions to astronauts; it would also greatly save on costs.
It would seem that there are few experiments which could not be carried out by automated systems, given the enormous budgetary incentives for making this work. This is especially true given that there is only an extremely minimal communications delay between the ground and Earth orbit, compared to that experienced with probes in the outer reaches of the solar system. This means that ground-based remote control of these systems is a more feasible measure than it is for interplanetary exploration. Accordingly, the systems can be much more flexible, as humans are ultimately making all the decisions and operating the experiment in real-time. Such control methods may become increasingly widespread as we develop further experience with virtual reality and tele-operation techniques, which are sure to progress as the Internet becomes increasingly central to the operation of global business. Of course, some of the most vital space experiments will always require manned involvement, as they involve studying the effects of prolonged microgravity on human physiology – knowledge that will be vital as we do move into space in decades to come.
At a time when public disillusionment with the whole space program is an increasing danger, the value of the Vision for reinvigorating NASA – in the eyes of the public, if not the astronomical community – cannot be neglected. It would be a sad state of affairs if an American population tired of repeated failures in manned flight and no longer captivated by the astronomical imagery of Hubble or Pathfinder, and also well aware of the ballooning budget deficit, no longer had the heart to support any significant space program. Although it may impact on discovery in the short term, the Vision for Space Exploration should prevent such an occurrence, and ultimately reduce the costs of all space-based science in the future; for that reason, it is a positive step.
Addendum
I have, to an extent, reconsidered my position on this issue. I still think
the Space Shuttle should be retired, and its replacement should be a series
of specialised craft rather than another attempt at a multipurpose workhorse;
and also that remote experiments may be a highly useful cost-saving measure.
I still think that manned expeditions to the Moon and Mars will be beneficial
and indeed vital to our exploration of space. But to some degree, it's a
chicken-and-egg problem - do we need to build a presence in near-orbital
space before we aim for colonies on the Moon, or will the lunar resources
that such colonies will bring enable us to build more in Earth orbit at
lower costs? I am inclined to believe the latter, but perhaps a compromise
approach would be best, and continuing to build orbital craft for some years
before lunar colonisation is attempted would be the most economic approach.
Alternatively, advocates of space elevators have suggested that one could
be quite easily built for less than the $100 billion allocated to the Vision
for Space Exploration, and this would undoubtedly provide the greatest long-term
ability to cheaply lift items to Earth orbit.
