Pathfinder For Spacelab

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It was hoped that data from VCAP would provide practical experience of using electron accelerators on later missions, particularly Spacelab-1. Plans were also afoot in conjunction with the Italian Space Agency to build a revolutionary 'tethered satellite', which would be trawled through the upper-atmospheric plasma on the end of a 20-km-long conducting cable. The first tethered satellite mission took place in 1992, several years later than planned, and it flew again on board Columbia in February 1996. Such tethers, researchers argued, could provide a steady supply of electrical power for future spacecraft.

Several other OSS-1 experiments were also intended as forerunners of more advanced versions planned for later Spacelab missions. Two instruments - the US Naval Laboratory's Solar Ultraviolet and Spectral Irradiance Monitor (SUSIM) and Columbia University's Solar Flare X-ray Photometer (SFXP) - were devoted to observations of radiation emitted from the Sun, to better understand the processes responsible for them and their impact on Earth. To support them, the flight plan called for Lousma and Fullerton to orient Columbia to aim her payload bay directly at the Sun for several protracted periods of time.

In fact, positioning the Shuttle in a series of different attitudes also satisfied another in a long list of tasks that needed to be completed before the vehicle could be

Gordon Fullerton manoeuvres the PDP around Columbia's tail fin during STS-3.

declared operational. During their eight days in space, the astronauts oriented her in four 'inertial' attitudes to place different parts under maximum solar heating. Columbia spent 30 hours with her tail facing the Sun, 80 hours with her nose aimed at the Sun and 36 hours with her open payload bay facing the Sun. The men also performed several 'barbecue rolls' to passively thermal-condition the whole spacecraft.

During the course of these tests, Lousma and Fullerton exposed the payload bay to its coldest-yet environment as Columbia's tail was pointed at the Sun. The temperatures in the bay were so low that 'outgassed' condensation formed on the aft flight deck windowpanes! When this had been done, the radiators were stowed and latched and the port-side door was closed. In general, the doors performed as advertised under intensely cold conditions, with the exception of a problem when a 'latched' indication was not received for one of the aft bulkhead latches. A spell of passive thermal conditionings quickly resolved this.

The week aloft enabled the two men to indulge in taking photographs of Earth. This mission had, according to oceanographer Bob Stevenson, given them an opportunity to photograph a virtually cloud-free China and one of their shots almost got them into diplomatic hot water after landing. ''Jack and Gordon were invited to China to speak to a huge audience [in] some auditorium,'' Stevenson said later, ''and they showed this picture of [a] lake. It was such a beautiful picture that they had it enlarged and matted and framed and they signed it off to the Premier of China [as a gift]. When they got to this picture, [there was] silence. When [the talk] was over, there was [subdued] clapping and they didn't know what to think about this. So they turned to the [US] ambassador and said 'We want to give the picture to the Premier', and he grabs the picture, looks at it [and says] 'I think let's hold this for a while'. When they were leaving the stage, they said 'What's the problem?' [The ambassador replied] 'Well, see that built-up area [on the photo]? That's a secret nuclear facility in China that they didn't know anybody even knew about!' ''

Lousma and Fullerton, it seemed, had inadvertently photographed the top-secret site while taking their Earth-observation photographs and, as Stevenson said later, ''Jack wasn't sure [he] was going to come home [alive]!'' After the flight, Stevenson and colleague Paul Scully-Power would arrange with a Chinese friend to put some important-looking comments and signatures in Mandarin on a blown-up copy of the photograph and presented it to Lousma and Fullerton. The faked inscription read: ''If you damn Yankees ever come over China again ...''

Meanwhile, as the astronauts continued to put Columbia through her paces, each of the OSS-1 experiments gathered its own treasure trove of scientific and engineering data. In addition to the instruments already mentioned, the pallet carried the Space Shuttle Induced Atmosphere (SSIA), Thermal Canister Experiment (TCE), Contamination Monitor Package (CMP) and - a boon for Britain's space ambitions - the University of Kent's Microabrasion Foil Experiment (MFE). The latter marked the first experiment built by researchers outside the United States to fly on board the Shuttle.

In effect, it was a square section of about 50 layers of tin foil. During the mission, it 'operated' in an entirely passive mode, measuring the numbers, chemical composition and density of tiny micrometeoroids in low-Earth orbit. Following Columbia's landing, the foil was removed from its place on top of the cube-shaped TCE and laboratory analysis enabled scientists to determine not only the depths to which the micrometeoroids had penetrated it, but, consequently, also their impact velocities. Heavier particles punched right through the foil and often left debris, while lighter icy ones left craters.

The TCE, to which the foil experiment was attached, was built by NASA's Goddard Space Flight Center in Greenbelt, Maryland, and evaluated a novel method of protecting scientific instruments from extremes of heat and cold - from 200 Celsius to minus 100 Celsius - in Earth orbit. It used a series of heat pipes which maintained several 'dummy' instruments at specific temperatures under various thermal loads and radiated waste heat into space. The canister actually performed better in orbit than it had done in ground tests and would later be used in the electronics module on the ASTRO-1 payload.

It also provided useful data for an ambitious experiment slated for Spacelab-2, which sought to better comprehend the physical properties of a peculiar substance known as 'superfluid helium' - the coldest-known liquid - and demonstrate its viability as a cryogenic coolant for future high-energy astronomical instruments. The Spacelab-2 experiment would build on data gathered during STS-3 by evaluating the behaviour of this strange liquid and testing a prototype containment vessel for it.

Within NASA, OSS-1 was known as the agency's Pathfinder mission. In many ways, several of its experiments would later find applications on 'operational' Shuttle missions and would fly late into the 1990s and beyond. Its last two pallet-mounted experiments (SSIA and CMP) assessed the impact of clouds and plumes of waste particles ejected from the spacecraft on scientific instruments. The first measured the brightness of particles emitted from the Shuttle, while CMP consisted of two mirrors - coated with magnesium fluoride over aluminium, commonly used in ultraviolet detectors - whose sensitivity was very carefully determined before and after the mission.

Scientific activity was also pursued inside Columbia's cabin, with several important experiments housed in middeck lockers. These were tended by Lousma and Fullerton throughout the mission. One of these experiments utilised a new, filing-cabinet-sized facility known as the Plant Growth Unit (PGU), which was so large that a middeck locker had to be removed in order to make room for it. The unit contained all the equipment necessary - growth lamps to provide 14 hours of artificial 'sunlight' each day, timers, temperature sensors, batteries, fans and a datastorage system - to grow almost a hundred plants in the weightlessness of space.

One of the key objectives of the PGU experiments on STS-3 was to test whether 'lignification' was a response to gravity or a genetically determined process with little environmental influence. Lignin is a structured polymer, which allows plants to maintain a vertical posture, despite the effects of gravity, and is thus highly important for the plant's ability to grow properly. The experiments tended by Lousma and Fullerton tried to find out if lignin was reduced in the microgravity environment and if this caused plants to lose strength and 'droop'.

Earlier experiments on board Skylab and the Russian Salyut space stations throughout the 1970s had revealed that the strange conditions in Earth orbit did indeed cause root and shoot growth to become disorientated, as well as increasing their mortality rates. However, little was known about the physical changes within them. Understanding how plants behave and grow in the absence of gravity was -and, with President George W. Bush's new vision for trips to the Moon and Mars, still is - essential for long-duration missions, in which astronauts will need to grow their own foodstuffs.

Chinese mung bean, oat and slash pine seedlings were chosen for STS-3 because all three could grow in closed chambers and under relatively low lighting conditions. Additionally, pine is a 'gymnosperm', which means that it is capable of synthesising large amounts of lignin, and it was believed that its growth was directly affected by gravity. Unlike the mung bean and oat seedlings, which were germinated only hours before Columbia's launch, the pine samples were germinated several days earlier.

The seedlings were used in three experiments. One looked at whether lignification was influenced by gravity or determined genetically within the plant. Several of the mung beans did indeed experience orientation problems, although the oats appeared to suffer no ill effects either on Earth or in space. The flight seedlings were all much shorter in stature than the ground control samples, but overall their levels of lignin reduction were only a few percent more than those grown on Earth. As such, although the results did point towards a reduction of lignin in space-grown plants, the difference was deemed statistically insignificant.

The second experiment used the mung beans and oats for chromosomal studies, revealing much fragmentation and breakage and confirming that their root cells had been affected by exposure to microgravity. A third experiment investigated how the organisation of the plants' gravity-sensing tissues, including the root cap, was affected by spaceflight. Within hours of Columbia's landing, the seedlings were removed from the PGU, immersed in fixative, thin-sectioned and stained for light and electron microscopy.

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