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Science, Maths & Technology

Are Manned Missions Worth It?

Updated Saturday, 25th December 2004

Professor David W Hughes compares the benefits of sending probes to explore the solar system against the value that manned missions could offer

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No substitute for the trip - Apollo 14 team member on the moon. Image: NASA/JSL Copyrighted  image Icon Copyright: NASA/JSL

When it comes to the manned exploration of space we seem to be advancing extremely slowly. This has been one of the great disappointments of my life. I was encouraged, as a child in the 1950s, both by reading Dan Dare (Pilot of the Future) in the Eagle comic, and listening to BBC radio’s Journey into Space programme. Here science fiction spacemen travelled all over the solar system and beyond. Seeing twelve men walk on the surface of the Moon between July 1969 and December 1972 gave me high hopes; a permanently manned base on the Moon maybe by 1980? the first footsteps on Mars by 2000? It wasn’t to be. Today the only ‘action’ is the International Space Station which is being assembled at a piteously slow rate at an altitude of less than 500 km, in an orbit confined to a belt encircling the Earth between 57o north and south. It will eventually take 30 USA shuttles and 40 Russian launch missions for completion. Then this 400 tonne craft will house a crew of six and provide 1200 m3 of living-room, habitable for a planned life of 10 years.

What has gone wrong? Why is progress so slow? Where is the ambition and drive? Human spaceflight certainly has a high media impact when the projects are new but it has always been seen as being in direct competition with less spectacular big-science research, and in competition with robotic space missions. As time passes and things become more established human spaceflight has difficulty maintaining the public interest, and thus the political support, and, even more importantly, the access to the huge funding that it requires. In the USA the cost of the Shuttle (the Space Transportation System to give it its full title) and the International Space Station regularly accounts for about half NASA’s annual budget. Human spaceflight is now a political ‘hot potato’ and suffers from stop-go funding often timed to suit political election deadlines.

There are three main problems.

The huge expense is the first. The USA’s Apollo programme was costing as much in a week as the price of a new huge earth-bound optical telescope. Stop Apollo for a month and you could have funded four new 5.2-m Mount Palomar telescopes. (You could, however, point out that Vietnam War cost the USA seven times more than the 9 billion dollar Apollo programme.)

Secondly today’s human spaceflight project, the International Space Station is just a staging-post, and it is difficult to get too excited about.

Thirdly there is the nagging feeling that robotic planetary exploration can do the job nearly as well as humans, and much, much cheaper and safer. If the three remote robots that have been driven around the surface of Mars can be effectively controlled from Earth and used to spy-out, select and analyse interesting rocks and features, why does a human actually have to be there standing on the surface. Remember that the planet-exploring human will also be somewhat removed from reality, cocooned in a life-supporting space suit, insulated from the heat and cold, and the dangerous, poisonous and inadequate atmosphere. It is not as if you can actually kneel down on the planetary surface and run your fingers through the soil. Even if you are convinced that there is no effective substitute for human observation it does not follow that the human has actually to be physically present. Someone sitting in an Earth-based control centre might do.

In the Apollo program much was made of the importance of the human involvement. Jim Irwin found the Genesis Rock sitting on top of a grey mound at the Apollo 15 site. Jack Schmitt, the only trained field geologist-astronaut, discovered orange soil underfoot close to Apollo 17. May be robots would have missed these. Apollo 13 showed how humans can react to the unexpected If something breaks they have a chance of being able to mend it. Robots are (as yet) very poor at repairing themselves.

But think of the problems. Humans are big; they use up 30 kg of raw material every day. And they have to be kept in a very precisely controlled environment. Too much heat or too much cold and they die. Very soft landings are required as are very, gentle take offs. Robots are not like that. Initially we humans will also need to take everything with us. In the future we might possibly find some water on Mars and Moon but there is no food and no free oxygen. Humans have to be kept healthy in space, and mentally active. Unlike robots, they cannot be switched off. Even though Valeri Polyakov lived in the Mir space station under zero-gravity conditions for 438 days, prolonged exposure to zero-gravity is still life-threatening. When weightless muscle and bone mass has been found to decrease by 1 % per month. And again, unlike with robots, ethics dictates that you cannot just send someone out there and not bring them back alive. Suicide missions are unthinkable. And to cap it all humans are extremely difficult to sterilise. It is highly likely that we would contaminate Mars when we started to wander over its surface and this could destroy the life-evidence that we are seeking.

The dangers to humans of bringing Mars soil into the landing craft must also not be underestimated. And returning Mars samples to Earth might be life-threatening to our population.

Apart from the rather unexciting low Earth orbit there are only two space places that humans can reasonably go to in the near future, these being the Moon and Mars. The Moon is easy. We have done the hard part; we have already shown it is possible to get there. All we have to do now is to return and stay. But if we stay for a month, near the lunar equator, we know that the ambient temperature will increase at lunar mid-day to a blood boiling 111°C, and then drop fourteen days latter, at lunar midnight to an oxygen-liquefying 170°C. Astronauts will have to dig themselves into lunar caves and insulate themselves from this violent temperature variation by covering their landing craft with deep layers of lunar soil.

Mars is much more difficult to get to than the Moon. This planet never gets closer to Earth than 56 million kilometres, and when it is behind the Sun is a huge 400 million kilometres away. A trip to Mars would take about 180 days, and a similar time is needed to get back. If Mars is visited when near conjunction, i.e. when Mars is on the same side of the Sun as Earth, one would most likely have to wait some 550 days until the next conjunction to come back. In this case the total trip time is about two and a half years. Mars is frosty-cold, the atmosphere is hostile and thin and its lack of oxygen and ozone means that the surface is exposed to dangerous levels of ultra-violet radiation. But at least Mars has a gravitational field that is 38 % of the Earth’s and it does go round every earth day or so. Another problem with the human exploration of Mars is the nagging thought that one could send about a hundred robot probes to Mars for the cost of a single manned mission

Still a long way to go: Titan's surface. Image: NASA/JPL Copyrighted  image Icon Copyright: NASA/JPL

When it comes to the human exploration of space one has really to put scientific considerations to one side. Some think that we, homo sapiens, need to go. Humanity needs a frontier to challenge the spirit of innovation and individualism, a remote frontier to instil vigour and to accelerate the rate of technological innovation. And space is it, the final frontier. And in effectively exploring anywhere you need the human mind, with its acuteness, inquisitiveness and inventiveness, a mind that is quick to find expedients, and a mind that is free of preconceived and pre-programmed prejudices. Only at the frontier do we find the gate through which we can escape the fetters of the past. Just as our distant ancestors broke away from the confines of the Mediterranean sea, we have to break away from the gravitational bondage of planet Earth. The fact that with modern technology Mars and the Moon can be colonised means that is inevitable that we have to go there sometime. It is not a matter of ‘if’, it is merely a matter of ‘when’.

We might quote the electioneering President George W. Bush. He said the “cause of exploration and discovery is not an option we choose; it is a desire written in the heart.” You might only really inspire the younger members of society towards science in general and space science in particular if you can generate interest by involving humans and risking humans.

You might consider the damage that we are doing to our planetary environment and conclude that human space flight could easily become essential if we want the human race to survive. But how will we go about it. The International Space Station illustrates the advantages of friendly cooperation between nations, whereas the Apollo Mission to the Moon underlined the importance of bitter rivalry and a race.

600 million people, a 1/6th of world’s population, watched Neil A. Armstrong set foot on the Sea of Tranquillity. Was it really “one small step for (a) man; One giant leap for mankind”. We have already waited over 35 years since the first moon step. We are clearly going to have to wait even longer to see if mankind can really make the leap.





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