« Last post by Robotbeat on Today at 03:59 pm »
Liquid helium can easily be stored in a small mobile dewar, so I donít understand what you mean by the VAB not being able to handle LHe. Not knowing the precise configuration, I canít rule out the idea of isolating the parts of the valve and seal and just using a small amount of liquid helium. The temperature difference in absolute terms is small compared to LHe and LH2, so there wonít be much additional contraction (etc).The boiling point of He is 4.222 K. It is unlikely that the VAB can handle liquid He. It's even more unlikely that the SLS can handle liquid He. Am I missing something?I still wonder if they could try a liquid helium test in the VAB. Or at least chill the gaseous helium to liquid hydrogen temperature.Two more questions: they've decided now but are not actually rolling back until 11pm (ET). Does that leave a window to change the decision if the NHC updates today move the storm away from KSC, or is this decision final and something else is causing the wait until 11pm?
Also, upon rolling back, will they do more leak-related inspections or will it just be "get the SLS out of the way of the hurricane, change FTS batteries, back to pad"? And if it's the latter, how soon can it be back on the pad?
There's a whole bunch of on-pad work that needs to be completed to secure SLS to the ML before the roll-back can begin.
They can (and most likely will) do further leak checks in the VAB, but that is done with gaseous helium. The problems are happening when the QD plate is contracting from thermal cooling from the cryogenic liquid hydrogen. Flowing liquid hydrogen through the system can only be done out on the pad.
I would presume they will do a full checkout of the SLS in the VAB, as well as fix anything that needs fixing, before they will roll it out. The pad itself would also need to be checked for any wind related damages before roll out.
And chilling gaseous helium to LH2 temperature would just involve boiling off liquid helium and running it through a heat exchanger (or just a length of tubing) until the temperature was just right.
Actually, storing lots of gaseous helium for testing is probably safer as LHe than with very high pressure tanks.