Re: Earth-grazing asteroids as a military resource

On 6/03/2025 8:28 am, Dave Platt wrote:

In article <vq8jtq$299g5$1@dont-email.me>,
Bill Sloman  <bill.sloman@ieee.org> wrote:
 

Silly suggestion. You'd have to plan your wars 30 years in advance,
and you couldn't sign a peace treaty with the thing a week away from
hitting earth.

>
You wouldn't have just one of them, and the trick would be to have a
bunch of them in orbits that could easily (and quickly) shifted from
earth grazing to earth impacting. You might mot be able to shift it back
into earth grazing in a week, but you could probably get it to hit the
Pacific ocean rather than your enemy's territory.
>

We can launch a nuke in 20 minutes.

>
And everybody can see where it came from. Junk in the asteroid belt is
anonymous, and an asteroid hitting the earth will vapourise anything
that might otherwise have been traceable back to you.

 If you're planning to maintain anonymity and convincing deniability
(as your final statement suggests) then you aren't really in a position
to use the asteroid as a bargaining chip in a war, are you?
 You can't contact your enemy's leader and say "Well, an asteroid that
we have absolutely nothing to do with, and have no power over, is
going to smash your capital city in a few weeks... unless you make
peace with us.  Then, we promise to pray to the Flying Spaghetti
Monster to divert it to a place where it will only kill a lot of fish
and cause tsnuamis that flood numerous uninvolved nations.  That
won't be our fault since we have no control over it."
 In addition to that... if you really want a bunch of them moved into
Earth-grazing orbits, it'll require a truly huge industrial effort to
loft the necessary number of "engines" to divert them into those
orbits (e.g. by gravity-tug effect, ablative lasers, etc.).

I haven't done the calculations - but then again neither have you.
My guess is that sort of ion drives that you'd use wouldn't be all that big, and you'd power them with solar cells. They'd need to keep pushing for quite a while. The first stage would be to stop the asteroid tumbling and get it spinning on an axis that more or less pointed at the sun so that the solar cells could stay illuminated for most of the time.
You might have ship up more reaction mass from time to time. Using theasteroid mass as your reaction mass might be practicable, but it would be an additional complication.

Do you really expect that any nation can do such a thing, and not have it
detected and traced back to the nation in question?  Outer space is
a lot more "visible" than something like the Manhattan Project was.

But there is a lot of it, and most of the action would be happening a long way away from the earth - more than 93 million miles, on average.

A counter to this sort of gambit would be for the targeted nation
to make it clear that their own retaliatory counter-force (ICBMs,
atomic-tipped cruise missiles, etc.) has been put into a deadman
switch of sorts, and will be launched if the asteroid strikes.

Which only works if you can correctly identify the source of the threat.

It'd be just another round of "Mutually Assured Destruction", without
a bunch of the existing safeguards (two-man firing rule, the ability
to hit a destruct switch up until the last moment, etc.) to stave off
Armageddon.
 That's not to say that somebody military won't propose it... but
I doubt that it will fly.

In the same way that the Germans thought that an atomic bomb was impracticable.
--
Bill Sloman, Sydney