Over the nine days of the D-2 (Deutschland-2) mission - 10 years after the first Spacelab mission, and Spacelab's ninth manned flight - film of the crew will be broadcast live as they work in a pressurised laboratory in the shuttle's cargo bay. In return for an investment of about dollars 370m - and with aid from Nasa, the European Space Agency (ESA), Japan and France - German universities, research institutes and industry have been able to fly most of the 90 experiments they planned.
The diversity of their research exemplifies the range of scientific disciplines eager to investigate the effects of microgravity. One German team is studying 200 tadpoles and fish larvae in an attempt to prove that young animals require the influence of gravity in order to develop a sense of balance.
Another group will be testing a high- precision robot arm, equipped with laser distance measuring devices, tactile sensors and stereo television cameras. The robot, which will attempt to build a small tower of cubes and to retrieve an object floating in microgravity, will be operated under remote control by astronauts or by scientists on the ground.
Researchers are also interested in the use of microgravity to create improved alloys and crystals. Small furnaces in Spacelab will produce materials such as large, high-quality semiconductors of gallium arsenide, important to the electronics industry.
D-2 will also carry an experiment called Anthrorack, the most advanced medical research facility ever flown in space. Investigations will be made into the impact of weightlessness on human organs, including deterioration of muscles and loss of calcium from bones. During the D-1 mission in 1985, results showed that cell multiplication in space is cut by 90 per cent. This suggests that the disease-fighting human immune system almost shuts down in orbit; this would have serious implications for long flights in space.
Scientists on the ground will be able to intervene in the experiments; for instance, the processes of heat transfer and cooling in transparent fluids will be monitored by holography, the technique used to create three-dimensional images on credit cards. Researchers at the Oberpfaffenhofen control centre, near Munich, will be able to transmit new commands themselves, or ask the crew to take various actions.
Such hefty investment and apparent enthusiasm for microgravity research mask a debate about the economic and scientific worth of such experiments. Even in Germany, government officials have expressed disappointment about the returns.
Such views are supported by the Fraunhofer Institute, which believes that the possibility of developing spin- offs from space research does not justify the high cost of the flights. At the same time, budget constraints have led to one third of Germany's sponsored Spacelab missions being offered to ESA and the international community.
Britain, one of the leading members of ESA, contributes only 1 per cent towards the microgravity budget. Heinz Wolff, director of the Institute for Bioengineering at Brunel University and an enthusiastic supporter of microgravity research, says one reason for the apparent lack of interest is the domination of the scientific community by 'big science' specialists. He admits that the high expectations of the early Eighties have not been fulfilled, but argues that it is not realistic to expect big breakthroughs after only a few hundred hours in orbit. 'It's like an expedition up the Amazon: a one and only chance to explore,' he says.
His views are supported by Joel Kearns, programme manager in Nasa's Division of Microgravity Science and Applications. 'Spacelab was ready to become much more productive in 1985, then came the Challenger disaster.' The shuttle flew three microgravity missions last year, he points out, and a Space Life Sciences flight is planned later this year. 'We're still in the exploration and discovery phase.' Professor Wolff believes that spin-offs from biology and materials sciences may include a cure for osteoporosis.
One key question is how to measure value for money (about 1 per cent of Nasa's budget goes on microgravity). John Pike, space policy director for the Federation of American Scientists, says the potential commercial applications of microgravity research have decreased in the past 10 years, as the experiments have tended to focus on pure science.
And what of the cost of Spacelab? Mr Pike believes that the dollars 100m average expenditure of a mission is acceptable in view of the possible breakthroughs in pure science and the outside chance of commercial profits.
One of the main problems is the short duration of flights. Many scientists and industrialists have tried to find a cheaper alternative that would produce four-week flights and not require human monitoring. ESA has developed its Eureca platform for launch from the shuttle; Russia's low-cost Photon satellites have become increasingly popular; and new generations of retrievable capsules are being developed in Europe, Japan and America.
However, not all the research involved is suitable for automated monitoring, and Mr Kearns emphasises that Spacelab is the only way of conducting interactive experiments between the earth and space.
Spacelab seems secure in the short term - two or three flights a year are in the pipeline - but if the plans to have Freedom, the dollars 30bn International Space Station, in orbit by the year 2000 do not go ahead, Spacelab's future will become bleaker.
Mr Pike says that 'only by flying a number of Spacelab missions over the next few years can Nasa find a use for Freedom.' However, as Freedom is being subjected to cuts and redesigns by the US Congress, the links between the projects seem to be growing more tenuous. 'It is entirely possible that Freedom will be cancelled this year,' Mr Pike says.
But what about Nasa's international partners? 'That will be too bad,' he says. 'They will get over it in a couple of centuries.'
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