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Aviation History
1992
1992 - 0084.PDF
Canada's payload specialist Roberta Bondar trains for experiments Germany has provided the Biorack to calculate the potential hazards . of cosmic rays to humans and to biological experi ments in space by assessing damage to single layers of bacteria and fungus spores, cress seeds and shrimp eggs. Japan's Radia tion Monitoring Container Device will also measure radiation levels inside the Shuttle and study the effects of cosmic radiation on similar biological specimens. Producing a more nearly perfect crystal or a new material is a precise operation, and scientists are just beginning to characterise processes in microgravity that affect materi als production in space. Gravity-related effects such as convection, buoyancy and sedimentation limit the perfection of some materials, and these effects are reduced or do not exist in microgravity. The IML mission will operate several crystal-growth and other materials sciences experiments, several of which have flown on Shuttle before. INVESTIGATIONS The Protein Crystal Growth experiment by NASA will involve 120 investigations, capi talising on experience gained by the previ ous Shuttle missions, STS26 and 29. On STS26, the largest crystal of gamma- interferon, a protein that stimulates the human immune system and is used to treat certain cancers, was grown. Crystals of this and of isocitrate lysae, a plant enzyme, and an other enzyme called elas- tase, produced a better quality and resolution, while a protein called canavalin from the jack bean, a plant of great nutritional value, formed single crystals instead of the crystal clusters usu ally produced on Earth. Germany's Cryostat will provide a tempera ture-controlled environ ment for growing protein crystals under two differ ent thermal conditions. Three experiments will assess the growth of beta-galactosidase, bacteriorhodopsin, cana valin and catalase. NASA's Fluids Experi ment System will con duct two investigations into image flows during materials processing of triglycine sulphate — the crystals of which have technological potential as infra-red detectors for military systems and as tronomical telescopes — and an ammonium chlo- raide and water solution which models the freezing of advanced alloys. The principal investigator of NASA's Va pour Crystal Growth System, Lodewijk van den Berg, operated it during its first space trip in 1985 aboard Spacelab 3. This time, van den Berg will be ground-based, watch- the results of Japan's Organic Crystal Growth Facility will be used to grow superconductors — metals or alloys which conduct electric current with no resistance, and which are key components of computers, communica tions satellites and electrical devices. Inves tigators are particularly interested in a crystal composed of two charge transfer complexes, tetrathiafalvelene and nickel, which acts like a metal superconductor. SIMPLE PHYSICS ESA's Critical Point Facility will utilise simple physics to assess materials process ing potential. The boiling temperature of all fluids depends on the pressure. Raise the pressure, and the fluid will boil at a higher temperature and be denser when it changes to vapour. The difference between the liquid and vapour density decreases as pressure and temperature increase until, at the critical point, there is no difference in the density of the fluid in the liquid and vapour states. At the critical temperature and pressure, regions of the fluid fluctuate rapidly between liquid and vapour in a wavelike manner. In addition to conducting the science investigations, the IML crew will film scenes in and outside the Shuttle using the IMAX camera, which gives audiences on the Earth an impression of what it is like "being there". The IMAX camera and projector use a film frame ten times the size of a 35mm film. The screen for the film can be ten times the area of a conventional cinema screen, up to seven stories high, so that audiences can "be there", seated in rows of seats with a specially designed steep incline. They will certainly be more comfortable than those IML crew members who have to ride the rotating/oscillating seat in Spacelab, guinea pigs in experiments which put sea sickness out of date. Z.I ing his investigations into the growth of mercury iodide crystals, which can have practical use as sensitive X-ray and gamma-ray detectors. Van den Berg grew a crystal in lOOh on Spa celab 3 which was of better quality than those pro duced on Earth. Another experi ment, from CNES, is called Mercury Iodide Crystal Growth. It uses a furnace to make the crystal evapo rate and condense in a cooler part of the container. Materials processing experiments will include crystal growth in space 34 FLIGHT INTERNATIONAL 15 - 21 January, 1992
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