> Terry W. Colvin wrote: Now, they find 100-kilometer
> craters on a regular basis. ...knowing that one day one will be on a
> collision course. Not to worry, say the modern-day Technocrats, we will
> launch nuclear-armed rockets that will nudge such cosmic threats into
> harmless trajectories.
> ...These Pollyannas are presumptuous.
> Comment. We are doomed---but not right away.
Way too Eeyore, Terry. The important thing is to find the object long
enough in advance. If we have 30 years notice (like the earth grazer
that was identified a couple years ago, to swing by a couple million
km from Earth in 2026) then we only need to produce a delta vee
of a meter per second in the impacting body to have it pass a safe
million km from Earth.
OK can we push a 10 km diameter pile of rubble to produce
a 1 meter per second delta vee? I think so. Use the density
numbers you quoted, 1.3 g/cm, and assume a shotgun pellet
cloud of rubble. Total mass about 10^15 kg. Surface gravity
would be about .3 millimeters/sec^2. So long as you dont accelerate
the mass any faster than .3 mm/sec^2, then loose stuff on the
surface shouldnt float away.
So if we managed to set up some thrusters on the surface to
accelerate the rubble pile at one thousanth that number,
3E-7 m/sec^2, it would pick up the necessary delta vee in
about a year. That would require the thrusters to produce
about 300 million newtons. This doesnt sound too far out
of the question.
Considering the nuclear ion thrusters already in existence,
I would think we could land a bunch of them on the surface
of an Earth-threatener and turn them all on. Especially if
the fate of humanity were at stake. Tigger would take on
that task. Wooo hooo! spike
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