FLUG REVUE February 2004: ISS faces tough problems

INTERNATIONAL SPACE STATION HIT BY CUTBACKS

By Mathias Gründer

The station must be built! As if swearing an oath, leading representatives of the participating nations' space agencies keep stressing this. Of course it must be built, since too many intellectual and material resources have already flown into the project, too many people from all over the world are working on it, too much finished hardware is already completed, just waiting to be launched and assembled in orbit. The station must be built since, after all, it stands as a symbol of co-operation between states and organisations which not so long ago were embittered enemies, as a proof that mankind can work together peacefully at the beginning of the third millennium A.D..

But the present burning issue is whether it is actually possible to build the station to completion, and if so, how? What technical options can be utilised, and how much will it cost? No one has an answer to this last question, even if solutions have been proposed for the others. Yet everything depends on when the three remaining Shuttles will resume service. If, immediately following the Columbia disaster, March 2004 was named as the earliest date for them to fly again, since then the flight schedule has changed virtually every month, and at present no one at NASA dares to forecast when flying operations can really be expected to resume.

Despite this, the crew for the first mission after the suspension of flights was announced in November 2003. The members of Atlantis mission STS-114 will include space novice Charles Camarda, a specialist in thermal protection, and over a series of three extravehicular activities (EVAs) simulated attempts will be made to repair heat shield tiles in various places on the orbiter and also to replace stabilising gyros on the ISS. The jobs originally planned for mission STS-114, the transportation of material with the Multi-Purpose Logistics Module (MPLM), and the actual replacement of one stabilising gyro, have been postponed to the next mission, STS-121, which will be flown by Discovery.

At the same time the NASA administration has announced that it may take the three remaining shuttle orbiters out of service once assembly of the ISS is complete. The possible date of decommissioning is stated as mid-2013, by which time the bulk of the experiments and the size of components will no longer require the capacity of the shuttles. At present they are still working on the assumption of one safety flight after resumption of the programme, seven missions to complete the US involvement in the ISS and some five flights per year up to 2009 to fulfil international obligations.

“LIFEBOAT” AVAILABLE FROM 2008?

From 2008 the orbital space plane, which at present exists only on the drawing board, should be available to the resident crew as a “lifeboat”, while two years later a two-way transfer vehicle should be ready for action. But after 2013 there will cease to be any powerful US space launch vehicles capable of transporting large payloads into earth orbit. At present they are keeping an open mind on the possibility of unmanned, remotely controlled use of one of the orbiters. But for all these proposals there is as yet neither a time frame nor cost framework.

Meanwhile the engineers are working feverishly on modifications to the shuttle orbiters, based on the requirements laid down by the investigation board into the crash of Columbia. Time is of the essence, for at present it is hardly possible to carry out any proper research in the ISS. For one thing, there are not enough experiments on board, and the emergency two-man crew can hardly do any more than keep the complicated edifice working.

One of the requirements was that future shuttle launches should take place only by day so that extensive photographic documentation could be collected and any problems in the launch phase identified promptly. However, this requirement could be met in future by the deployment of two modified Martin WB-57 aircraft. Stationed at Ellington Field near the Johnson Space Center in Houston, Texas, these planes have been used for high-altitude research missions since the early 1960s and can be flown as high as 18.3km. With their night-capable camera equipment, they could accompany the orbiter in the initial phase of its climb and photograph every movement of the system. If such a system had been in service at the time of the Columbia mission, the fact that a piece of insulating foam had broken free from the Shuttle's external tank and struck the leading edge of the left wing might have been detected promptly. No information was issued regarding the cost of using the aircraft regularly, but the safety of the shuttles and its crews must be worth the additional expense.

NASA is not the only organisation preoccupied with the future of its depleted fleet of reusable launch vehicles. Industry is also involved in the race to resume the launches. In October 2003, for example, ATK Thiokol Propulsion announced the completion of a series of tests on enhanced solid booster rockets for the shuttles. The five-segment boosters are 8.38 metres longer than the previous four-segment boosters and produce a thrust of 16.01MN each, compared with 13.84MN in the present configuration. With this extra thrust, the payload capacity of a Shuttle could be significantly increased. Moreover, the safety reserves would be bigger, as an orbiter could achieve a sufficiently high orbit and still have sufficient reserves to abort the mission, even if the main engines have been jettisoned during the ascent. However, the test series was not the product of a contract let by NASA, and NASA management has not yet expressed any opinion on the matter. At the present time, moreover, it is not clear what effect increasing the thrust would have on the strength of the airframe.

For the time being ISS operations are just ticking over, and the fact that this is possible at all is entirely due to the Russians with their “outmoded” space technology. Without their involvement, it would have been necessary to give up manning of the rump station already. Instead, the Russian Soyuz spacecraft and Progress cargo ships are keeping the project alive, at least for the time being. In April 2004 the next resident crew will set off to relieve the present crew, and ESA will use the opportunity to send its Dutch astronaut, André Kuipers, into orbit for a week.

In the long term, however, even this economy regime is unsustainable, as the biggest problem is how to supply the astronauts with drinking water. Only the Russian section of the station has a closed water circulation system including reprocessing: in the American section, waste water is simply spilled overboard. This extravagance is now turning into a problem that has to be taken seriously. Another problem is that the available space on board is slowly filling up, as rubbish bags which normally would have been carried back to Earth by the Shuttles are blocking the way. Only recently, on instructions from Mission Control, the astronauts had to clear an access path to the fire extinguishers, which had gradually disappeared under the rubbish.

While on the ground all efforts are focused on the resumption of flying operations so that assembly of the space laboratory can continue, the station, which is now five years old, is presently in hibernation. To raise it from its slumbers is the most important challenge facing international manned spaceflight this year.

From page 36 of FLUG REVUE 2/2004

Last updated 10 January 2004

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