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Re: Physics help (I found it!)

At 11:51 PM 5/20/96, Timothy van der Linden wrote:
>>> Kelly:
>>>>No, my Explorer design doesn't use on board fuel for accell out of the sol
>>>>system, or return decel.  A bigger problem Is I forgot the 2e7 exaust
>>>>velocity was for a He3 system which obviously isn't very feasable for 17
>>>>years of onboard storage.  (Liquid helium is incredibly good at geting
>>>>out of
>>>>sealed containers.)  I havent bothered to try to figure out the numbers for
>>>>Li6 fueled system yet.  But I remembered they sounded bad.
>>>Keep in mind that the temperature where Helium becomes fluid and the
>>>temperature where Helium becomes superfluid are not the same, there is a
>>>difference of about 2 degrees between them.
>>I think maybe Kelly was refering to the half-life of tritium, rather than the
>>superfluid properties.
>Why then is he worring about liquid Helium being incredibly good at getting
>out of sealed containers?

No, I was just worried about keeping the stuff in the tanks for 20 years,
and of course the weighnt of the tank itself.  One distinct advantage of
lithium is that it is a solid metal at room temp.  So It doesn't boil off
or need a tank.  However since Li produces about 75% of the power per Kg
(1.596 E14 vs 2.059 E14).  This would obviously take a big hit out of the
spec impulse.



Kelly Starks                       Internet: kgstar@most.fw.hac.com
Sr. Systems Engineer
Magnavox Electronic Systems Company
(Magnavox URL: http://www.fw.hac.com/external.html)