On Thursdays plan launch there were holds placed on the countdown because of a boat offshore in a restricted area, and wind gusts exceeding launch limits. Finally the launch was scrubbed due to problems with fill/drain valves for the liquid hydrogen propellant, and the rendezvous planar window closed. Liquid hydrogen is tricky stuff to work with. In order for hydrogen to become a liquid, and not boil off, it must be pressurized, and cooled to ~ -423*F.. There are aspects of low-temperature phenomenon that morph liquid hydrogen in to what is called a superfluid. The atoms of a superfluid arrange themselves in very pronounced linear pairs. (Similar to what occurs in a superconductor.) Once the liquid transposes to this unique state of matter (Yes, there are many more states of matter than the common solid/liquid/gas.) the superfluid will leak through conventional containment components impervious to other normal liquids. Hence, conventional welding seams techniques for tanks are insufficient. As well as conventional plumbing, connections...and valve designs. Here is a clip demonstrating the unique properties of superfluidity. The video shows liquid Helium. Superfluidity occurs in hydrogen at a higher temp.
Posted on: Mon, 08 Dec 2014 11:46:42 +0000
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