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The Artemis H2 leak has been quoted in %. I believe 4% is the stated limit. I assume that measurement is vol % of H2 in air but I haven't seen any real definition of the parameter. What is the rationale behind this number?

I suspect that this might be the lean flammability limit of H2 in air but it might also be some indirect measure of a leak rate into the region/volume where it is measured. I would also like to know whether this parameter is a "not to exceed" or whether is is an average over some time period: i.e., how is the parameter applied?

thanks for any insights. tom kosvic

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  • $\begingroup$ During the recent cryogenic fueling test, the launch team modified the parameter to "10% or more than 5 minutes above 4%, whichever occurs first", so it is clearly not a hard and fast rule. The rationale for loosening the constraint was that they wanted more time and more data to observe how the leak behaves, and the argument for why it is safe to do so was that there was no ignition source since this was purely a fueling test. $\endgroup$ Sep 25 at 22:21

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