Re: Surviving your star's red giant phase


BOTE calculation here.

MEarth = 6x10^24 kg

Let us say we need a delta-V of 10 km/s to move it to the safer orbit.

Say further that every time a 1 kg swarm-bot passes, it drops 10 km/s
of delta-V. Earth, in turn, gains that much energy. We need only make
6x10^24 passes, and our work is done! We have 500 million years to
work with, so a mere 1.2 x 10^18 passes per year will do it.

....hmmm. Assume 1% of our swarm can make a pass in any given year; the
other 99 years are spent solar-sailing back to a higher orbit,
regaining those lost 10 km/s of delta V. This means a constant
acceleration of about one one-millionth of a gee, which doesn't seem
unreasonable.

So, the total number of swarm-bots will be 1.2 x 10^20. This gives the
swarm the total mass of a biggish asteroid... it's about half the mass
of Pallas.

To my mild surprise, this seems remotely plausible.

Interesting note: We have the swarm-bots flying past the planet at the
rate of around a hundred trillion per hour. They probably come fairly
close -- 1000 km or less -- to get the best momentum transfer. So,
what with the sails, they're going to be visible.

Assuming that they organize themselves into a few most-efficient
orbits, the result would be ropes of light following the planet around.
I don't think they'd be visible by daylight, but at night it would be
like several brighter, narrower Milky Ways coming down from infinity,
swooping across the sky, and then soaring back up again... the visible
evidence of the long-term project to keep the planet habitable.

Am I completely whack here?


Doug M.

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Relevant Pages

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