Re: How to really terraform (part 1)
From: Sander Vesik (sander_at_haldjas.folklore.ee)
Date: 06/18/04
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Date: Fri, 18 Jun 2004 02:36:11 +0000 (UTC)
James Nicoll <jdnicoll@panix.com> wrote:
> In article <1087465212.256455@haldjas.folklore.ee>,
> Sander Vesik <sander@haldjas.folklore.ee> wrote:
> >Christopher James Huff <cjameshuff@earthlink.net> wrote:
> >> In article <1087344582.784451@haldjas.folklore.ee>,
> >> Sander Vesik <sander@haldjas.folklore.ee> wrote:
> >>
> >> > Thats not a problem - they don't have to pay in advance, money transfer
> >> > orders move more or less as fast in space as they do back here on earth -
> >> > at lightspeed (minus delays in communication medium and equipment).
> >>
> >> Assuming the government and companies survive. The only way this could
> >
> >The acceleration and power-feed phase would not last longer than exit
> >from Solar system. in fact, it make sense for it not to.
>
> I'm not sure 60-100 AU is enough distance for a massive
> object like a generation ship to get to 0.02 C.
>
Well, I guess I consider the solar system to be larger than you do, by about
five to ten times.
> Hmmm.
>
> S = 1/2 at^2
> V = at or t = V/a
> so
> S = 1/2 a [V^2/a^2] or 1/2 V^2/a
> a = 1/2 V^2/S
>
> If S = 1.5^13 m and V = 6x10^6 m/s
> a = 1.2 m/s/s
Well, taking it to be a cool 500AU instead we get an acceleration of
0.24 m / s^2. Which is much softer and more achievable.
>
> That's a hell of an acceleration for a big ship.
>
> Call it 100,000 tonnes dry, and 400,000 tonnes fueled
> and if Vexhaust ~ delta vee, we're talking something like
> 1.5x10^15 watts.
1 m^2 of solar panel at earths distance gets 1300w, assuming 15%
conversion thats 200 W / m^2 so we need about 7,500,000 sq km
of solar panel. That is only about 5% of Earth's surface area
so nothing really radical. Could well be built in Earth orbit
from Lunar materials and kept in HEO indefinately.
No need for truly huge power stations on solar centric orbits
>
> Of course by its nature, interstellar flight involves
> huge amounts of power.
Yes, but we have got this bloody big fusion reactor out of which
output nothing but an extremely infestimal amount gets used.
>
> >> work is with an extremely cheap and low-maintenance solar power
> >> satellite, and then you have problems like pseudo-eco-terrorists who
> >> think humanity shouldn't spread destroying your power station. The risks
> >> of your power source being turned off before you reach your destination
> >> just seem far too great. I don't think such a mission should rely on
> >> beamed power for more than a couple decades.
> >
> >INtrestellar power beaming doesn't work well anyways.
> >
> No?
I would have hoped so. Domn't want anybody to start using earth as a
big rectenna just becasue they find humans annoying ;-)
>
> People who are into beaming power using microwaves are willing
> to assume we can make arrays many km across. If we can use much shorter
> wavelengths, an array of the same size has a much longer reach. Blue
> light gives you D1D2 of about 1.6x10^10 m^2 over 4.3 ly. Those are
> big (two arrays 130 km in diameter, say, or one 1000 km in diameter and
> one 16 km in diameter or some other useful combination) but not entirely
> unthinkable, given the technological context.
>
Yes. You could also send one such "ahead" and only beam power half way. Will
also help with more distant stars.
-- Sander +++ Out of cheese error +++
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