[Rockhounds] Terraforming Mars might be impossible? for now

[Alan Silverstein]

> It's OK to dream big, but don't forget that it's just a dream at the
> moment...

Sure.  I put my notion out there -- explore, evacuate, bombard, return
-- just as a novel out-of-the-box concept to keep in mind.

> I want to hear more about how we harness the sun's energy to
> accurately move massive bodies 2.7 AU out from the sun's surface...

Not sure if you keep up with various pubs like I do, such as Science
News, Sky & Telescope, and the Planetary Report...  But I see that we've
dreamed up quite a few creative ideas for how to modify asteroid orbits
(of course mainly intended for collision avoidance).  None of them yet
proven of course, but I think one test mission is in the works?  Anyway,
just from memory, here's a summary of possibilities that I can recall:

- Nuclear or other explosions, the brute force approach.

- "Laser bees" or other methods using co-orbiting satellies to direct
  solar energy onto hot-spots that act like low-thrust, long-term rocket
  engines, blasting reaction mass off the object.

- "Gravity tractors" where a sufficiently massive co-orbiting satellite
  propels itself, and tugs on the asteroid.

- Directed YORP effect (however you do it) turning the object into a
  crude solar sail using solar photons.

Of course in all cases, the smaller (less massive) the target, the
better.  Hydrating/oxygenating a whole planet, even a small one like
Mars, would take a lot of raw mass, but possibly this can be done using
a large number of smaller objects, each of which is easier to shuffle
around.  In each case, depending on how patient you can be, it doesn't
require a lot of oomph to redirect the orbit.  Yeah there's the angular
momentum problem; people don't realize it can be harder to hit the sun
than to escape the solar system; but you don't need to fully circularize
the orbit (more delta-v), just ellipticize it enough to intersect.
(Beyond that, though, I'm too far removed my undergrad days at Caltech
to actually do the math, sorry.  :-)

What was that sci-fi story years ago where a protagonist worked
backwards from the desired result to play billiards with the Kuiper
Belt?  One point there was that you don't have to massively redirect
every single object, if you can swing it right, you can do some elegant
momentum transfers, where one object, say, hits Mars, while another goes
farther out, or escapes completely.

Cheers,
Alan Silverstein