Getting the solution concentration and its proportion to precipitant just right is a tinkering game, demanding trial after trial until the perfect combination is found. Until now, the expense of designing flight-qualified apparatus for growing the crystals has been high, and only a few samples have been accommodated on each mission, which severely limited the opportunity for testing crystallization conditions. Their idea was to seal protein and virus solutions and liquid precipitants in small tubes, flash-freezing each to keep the liquids separate, group the tubes in bundles, and place them in an aluminum cylinder inside of an aluminum dewar. The dewar would then be filled with liquid nitrogen, which would maintain the flash-frozen tubes of solution and precipitant, preventing the two from mixing. The contents of the tubes thaw, and the very slow inter-diffusion of precipitant and solution begins.
Crystals form without any interference from the container, other crystals, or turbulent flows.
The experiment takes up little space and uses few budget dollars. Not only does the dewar experiment eliminate the expense of the complex flight apparatus, it also allows for the testing of many more samples than on previous missions. We would like to optimize conditions for a particular protein. Normally, that is an empirical process in which you set up a lot of samples and see which perform best. Because we can fly so many samples in one dewar, we can use it as a mechanism for optimizing conditions quickly and cheaply.