The International Space Station

At the time of this writing, manned space activity is almost entirely focused on the construction of the ISS in low Earth orbit (LEO). As the name implies, this is an international project involving the space agencies of the United States (NASA), Europe (ESA), Japan (JAXA), Canada (CSA), and Russia (RKA). Its orbit is a near-circular LEO with an inclination of 52 degrees, and a height of about 350 km (220 miles), although the altitude varies a little due to the effects of air drag. When completed in 2010, the mass of the station will be an impressive 450 metric tonnes, and Figure 10.3 shows its final configuration.

The construction began in 1998, and more than 40 assembly flights will have been required to complete the station's construction, the majority of these being Space Shuttle flights. Once completed, the largest overall dimension will be about 110 m (360 feet), the total available electrical power will be on the order of 100 kW, and the pressurized volume accessible to the six crew members will be around 1000 cubic meters (35,000 cubic feet). Beyond completion, the projected lifetime of the station is 6 years, so that it will be scheduled for a controlled de-orbit and atmospheric reentry around the year 2016.

Another impressive statistic is the anticipated cost of the project, about $130 billion, and it is this statistic that has drawn the most attention from the station's critics. The substance of most of this criticism is founded on the belief that the huge budget for the ISS could be better spent on unmanned spacecraft, such as observatories and interplanetary probes. The argument goes that the return in terms of science of unmanned exploration would be much greater, and it is easy to have sympathy for this point of view. The main science research goals of the ISS include astronomy and Earth observation, but we can see (from Chapter 2) that the ISS orbit is not ideal for either of these activities. Other research areas focus on experiments that require one or more of the unusual conditions, mostly related to microgravity, present on the station. These include the continued study of the effects of weightlessness on people, and studies in physics and chemistry, such as materials science. The argument between the two camps has been quite acrimonious at times. One outspoken opponent of manned space exploration is Bob Park, a professor of physics and formally the chair of the Department of Physics at the University of Maryland. His view is rather extreme, but nevertheless sums up the strength of feeling in opposition to the ISS among some American scientists. Park states, "NASA must complete the ISS so it can be dropped into the ocean on schedule in finished form"! (Park points out on his personal Web site that the views he expresses are his own and not those of the University of Maryland.)

My own feelings about the ISS are mixed. I have to admit that I have always thought it to be a very expensive project that is looking for a purpose to justify the cost. It can be argued that nations involved in programs like the ISS gain economic benefit through the development of a high-tech industrial sector, with the associated highly skilled work force. It is certainly the case that there are spin-offs from space technology development, and I am referring to more than just the much-quoted old chestnut—the Teflon frying pan! There is certainly economic benefit to be gained from space industry research and development spinning-off into commercial industry. But generally I would guess that the level of benefit in economic terms is very likely to be less than the investment. So I have to take an alternative tack in justifying expensive manned space programs like the ISS. The fact that the mission ends around 2016 also implies that the ISS will not be a part of the orbital infrastructure in aid of a return-to-the-Moon program or a manned mission to Mars. On the other hand, unlike Bob Park, I am fundamentally a supporter of manned space exploration, and the ISS provides a learning opportunity before more adventurous manned space activity is undertaken. Again my impatience comes to the fore, as progress seems so painfully slow. On reflection, if I were asked to draw up a list of reasons to justify the ISS program, they might be something along the lines of:

• Providing a permanent manned presence in space, and learning how to be there.

• Learning how to build large structures in orbit.

• Learning how to manage large, expensive, complex, and multinational space projects, so that they can be run in an efficient and cost-effective manner.

• Providing inspiration to young people to encourage them to become involved in space engineering and science.

Most of these learning activities will be required in order to take the next steps in leaving Earth and exploring the solar system. I believe that the lessons learned in the ISS program are vital in equipping us for those next steps. However, I am also sure that opponents of manned space activity will still insist that these lessons do not justify the price tag.

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