Re: Colonizing a Neutron Star

Logan Kearsley wrote:
Quite some time ago (
http://groups.google.com/group/rec.arts.sf.science/browse_frm/thread/ca7037c
587195f83/b8e53951254d164d ) I proposed the idea of Tide World- a megascale
space habitat that makes use of tidal forces to generate gravity at either
end- and noted that a neutron star would be an ideal place to build one,
since you can get large tides over fairly short distances, but then I never
really went anywhere with that.

Interesting idea! I'd be curious about how the numbers work out, how big can you make it assuming, say, carbon nanotubes for structural material?

Hmm, it's got to be long-axis oriented, and 1g at the habitable ends, so the maximum length of self-supporting CNTs is, what, a few thousand kilometers? so I suppose that would be the maximum size scale you'd be looking at; maybe an order of magnitude smaller by the time you've handled the asymmetry?

I'm wondering now, though, how exactly one might go about building a space
habitat around a neutron star. I like using a tide world both just because
you can, and because that provides an excuse to have some really long
tethers involved which could be used for generating large amounts of
electricity as the neutron star's magnetic field sweeps by. I expect you
could get some electricity out of the radiation environment- young, hot ones
will be glowing a bit in visible light if nothing else works out- but mining
the star's rotational kinetic energy via its magnetic field would provide
enormously more power.

*nods* This has been proposed in other environments, including Earth and gas giants. Alas, it doesn't work; if primary rotates slower than satellite, energy for tether electricity comes from orbit of satellite, which ends up crashing into primary. If primary rotates faster, energy comes from rotation of primary which is fine except angular momentum transfers to satellite, which drifts further and further away.

But lots of energy from radiation environment, even not so young neutron stars quoted at several times 10^5 K, which makes them area for area maybe a hundred million times brighter than a conventional star. Need to make sure close enough to get 1g tides doesn't also mean close enough for neutron star's heat output to vaporize the habitat! Might end up needing to pick an extremely old neutron star, don't know if universe is old enough for any to have cooled enough.

Another thought comes to mind. If you've got an old, quiet neutron star, and
maybe a convenient gas giant hanging around, would it be possible to feed
hydrogen onto the surface at just the right rate to keep up a continuous
fusion burn, as opposed to setting off cyclic nova events as the hydrogen
envelope builds up?

I don't know, but material hitting the surface of a neutron star will deliver much more kinetic than nuclear energy, so if not, use nuclear "ash", anything that's too heavy to go boom.

--
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Relevant Pages

  • Colonizing a Neutron Star
    ... end- and noted that a neutron star would be an ideal place to build one, ... habitat around a neutron star. ... I like using a tide world both just because ... electricity as the neutron star's magnetic field sweeps by. ...
    (rec.arts.sf.science)
  • Re: Colonizing a Neutron Star
    ... habitat around a neutron star. ... electricity as the neutron star's magnetic field sweeps by. ... If it's primarily to get easy artificial gravity, ...
    (rec.arts.sf.science)
  • Re: Colonizing a Neutron Star
    ... I dunno. ... I haven't gotten to the purpose yet. ... Nobody expects a habitat around a ... neutron star. ...
    (rec.arts.sf.science)