Re: A Stooopid idea (really: what temperature is liquid hydrogen)
In reply to #2241 A Stooopid idea (really: what temperature is liquid hydrogen) by Jo Jaquinta
In TML V15#3 msg 2241 Jo Jaquinta [email removed] writes: ... > They all have ship's suits (tailored vacc suits). It says they can > withstand temperatures up to -110C. So given the large storage tanks of > liquid hydrogen he was thinking of encouraging her to take a dip. > So the question is what temperature is hydrogen fuel [or methane or > whatever] stored at? How long could Annie swim before it became more than > invigorating [she has lots of her own insulation]? Hmm. LH2 has a density of about 70Kg/m^3, LH2O about 1g/cm^3 = 1000Kg/m^3 , thus LH2O is about 14 times denser than LH2 -- it's also much more viscous than LH2, although I don't have those numbers handy. I suspect than Annie would dive into the LH2 tank, fall like a rock to the bottom, and rupture her suit. At the very least, she'd be trapped at the bottom of the tank, in a -110C vac suit, in a -240C liquid. BRR! BTW, why are the low-temp numbers for vac suits so very low? After all, the big problem in space is getting *rid* of body heat, not conserving it -- the vacuum outside the suit is at a very low temperature, but it's also a darn good insulator! :-) I suspect that the -110C rating corresponds to a much lower rate of *heat loss* than one would experience immersed in LH2. Thus Annie would probably be Anniesicle before she even hit bottom... It's hard to say what temperature the LH2 would actually be stored at, but I can't think of any good reason why it would be deliberately kept much cooler than its boiling point, cited above. With a pressurized system, the system might well reach equilibrium with the cabin temperature and still contain some liquid, in which case Annie could sit down there for quite a while, unless the pressure was enough to squish her the moment when she somehow got into the tank without depressurizing it -- I haven't calculated this. See the recent PBEM summary for what might happen if she does somehow accidentally release a tremendous quantity of gaseous LH2 into the oxygenated atmosphere in the process of getting into the tank :-). All in all, I don't like Annie's chances on this one :-) :-). Bart Massey [email removed]