Crystal Growth Research

Elsewhere in the 10,310-kg USML-2 module were several other experiments modified or improved in the wake of their first flight three years earlier. ESA's Glovebox, for example, had been outfitted with a much larger working area and better lighting for this mission, during which it supported no fewer than seven separate investigations. Experiments on USML-1 had yielded protein crystals of much higher quality than had ever been achieved previously, and by 21 October video from the Spacelab was showing a busy Sacco getting the first zeolite investigations up and running.

Zeolites are used on Earth for the purification of fluids in life-support systems, as well as in the petroleum-refining process and in waste-management and biological fields. In effect, they act as 'molecular sieves' to separate out specific molecules from solutions and might someday allow gasoline, oil and other petroleum products to be refined far less expensively. In addition to operating experiments in the Spacelab module, Sacco tended to his own Zeolite Crystal Growth (ZCG) furnace in Columbia's middeck, which processed 38 sample containers as part of efforts to create large, near-perfect crystals.

Results from USML-1 had already shown that zeolite crystals whose nucleation and growth were carefully controlled from the start of the experiment achieved a much higher level of perfection than Earth-grown ones. ''We want to learn more about how zeolites nucleate and grow and learn more about their structure, so we can apply that knowledge to different processes on Earth,'' said ZCG team member Nurcan Bac of Worcester Polytechnic Institute in Massachusetts. ''For instance, one of the zeolites in this experiment is widely used by the petroleum industry to 'crack' heavy oils into gasoline. If we can increase the efficiency of this type of zeolite, we could get more refined petroleum products from the same amount of crude oil.'' Sacco agreed, pointing out that such experiments could lead to major breakthroughs in the future, thus ''pointing us in the right direction for space station research''.

Other investigations crammed into lockers in the middeck included a new container known as the Diffusion-controlled Crystallisation Apparatus for Micro-gravity (DCAM), which pioneered a method of autonomously running long-duration protein crystal growth experiments on board the International Space Station. During USML-2, more than 1,500 protein samples were processed, despite a requirement to lower Columbia's cabin temperature early in the mission when one of the experiments' thermoelectric coolers overheated slightly.

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