From: Spike Jones (spike66@attglobal.net)
Date: Wed Mar 14 2001 - 22:21:06 MST
hal@finney.org wrote:
> Mike Lorrey writes:
> > A new NASA program is the Ultra Long Duration Balloon, which can carry
> > up to 1600 kg at an altitude minimum of 33.5 km for periods of up to 100
> > days. What is the mass fraction required to launch from the 33.5 km
> > altitude at the equator and gain a 200 km orbit? (btw: what is the
> > equation to use to calculate mass fractions? Spike, can you post up your
> > spreadsheet?
>
> I don't know the answer, but I do know that getting to altitude is a small
> part of the problem of reaching earth orbit. LEO velocity is 7.5E3 m/s.
> Putting 1 kg into this orbit takes 1/2 mv^2 or 2.8E7 Joules. Raising 1 kg
> by 33.5 km adds 9.8 * 33.5E3 Joules or 3.3E5 Joules, just over 1% of the
> needed energy to reach orbit. So you haven't gained much. Hal
Hal is right. I will post the spreadsheet to you directly Mike, I
dont think we can post spreadsheets to extropians. Or what?
Unfortunately getting up high doesnt help as much as I would
have hoped. As Doug pointed out, the savings is in more optimized
nozzle shape and lower weight payload fairings. spike
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