[ExI] one way ticket to mars
Eugen Leitl
eugen at leitl.org
Tue Apr 23 16:45:24 UTC 2013
On Tue, Apr 23, 2013 at 09:11:27AM -0700, spike wrote:
> I agree the ion engine is feasible, even current technology. But my
I've seen ITO/InP on Kapton is claimed to have 2 kg/kW.
http://apl.aip.org/resource/1/applab/v95/i22/p223503_s1?isAuthorized=no
So if they need 200 MW, that'd take 200 t.
> argument is that it doesn't do as much as they say. You still need chemical
> propulsion to get to LEO to assemble the ion engines, and I figure you might
But that time is not part of travel, since the crew sits
there terraside, twiddling their thumbs until craft is ready
for departure.
> need chemical propulsion to get out of the earth's gravity well in a
> reasonable amount of time. Even then, with that marvelous Isp the nuclear
It's not nuclear, it's electric, solar-powered.
There are some data on nuclear VASIMR
http://web.mit.edu/mars/Conference_Archives/MarsWeek04_April/Speaker_Documents/VASIMREngine-TimGlover.pdf
There are some fusion-assisted propulsion plans, but I
think it's too speculative at this point
http://www.technewsworld.com/story/77758.html
> rockets offer, the optimal mission assuming humans aboard is far waaay
> longer than 30 to 40 days. Every scenario I ran optimized in an orbit not
> far from a standard Hohmann transfer, perhaps a little over 5 months being
> the shortest practical mission, and even then you hang your lives on the
> system working perfectly at the other end for Mars insertion. 30 to 40
The problem with photovoltaic is that you only have half power at Mars.
> days, no way.
>
> My assumptions went up to Isp of about 1200 m/sec, much beyond which your
VASIMR VX-200 claims an Isp of 5000 s.
http://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket
Zubrin doesn't like Ad Astra, but they've replied to his criticisms
with http://www.adastrarocket.com/VASIMR_development_AdAstra_15July2011.pdf
> energy consumption goes nuts, and the total thrust is way low for the very
> high Isp systems. The really shorty missions, anything less than about 5
> months, require high total thrust at the far end, otherwise you die of
> boredom and starvation on your way out to Jupiter, waving a sad goodbye to
> Mars, damn. {8-[
>
> But you make a good point: I need to get out all those spreadsheets I made
> 15 yrs ago, update them and start calculating again, see if anything will
> change my mind. Already something has: China and India are going into space
> stuff bigtime, and they have buttloads of money to dump into it. Those two
> guys may work together, and if they do, you have a couple billion proles
> from which to choose rocket scientists.
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