[ExI] META: Overposting (psychology of morals)

Kelly Anderson kellycoinguy at gmail.com
Tue Mar 1 05:26:03 UTC 2011

On Mon, Feb 28, 2011 at 7:11 AM, Ben Zaiboc <bbenzai at yahoo.com> wrote:
> Kelly Anderson <kellycoinguy at gmail.com> stated:
>> Of all potential mega disasters we could face,
>> asteroid hits
>> are the most easily preventable... (compared to such things
>> as super
>> volcanos, subduction earthquakes and tsunamis and the like,
>> where we
>> are simply powerless at this point.)
> That's an interesting assertion.

Tell the History Channel. I got the idea that it was possible from them.

> I presume you mean this in the same way that we might say "Of all the coronal mass
> ejections in the galaxy, the ones produced by our own sun are the most easily preventable"?
> At this point in history, I think our ability to protect ourselves from a dinosaur-killer asteroid is
> doubtful, to say the least.

Not at all. If we find it in time. That's why the NEO program is so
very important.

1) We have now successfully landed space craft on asteroids (or at
least crashed into them).
2) There are several competing mechanisms for tugging an asteroid into
a slightly different orbit including:
 a) A gravity tug (suggested by two NASA astronauts) where a space
ship of sufficient mass parks itself on one side of the asteroid, and
accelerates away from the asteroid whenever it gets too close, thus
giving it a gravitational tug into a new slightly different orbit
(paper referenced later)
 b) Reflecting light onto one side of the asteroid
 c) blowing big asteroids into smaller ones. (kind of hazardous)
 d) deflecting the asteroid by installing a mass accelerator that
shoots out pieces of the asteroid in a single direction with great
 e) There are several other proposals, some far fetched, some that
might just do the job.
 f) all of the above.

If the asteroid is slightly deflected ten years prior to an earth
strike, it will miss the earth. A very small deflection would be
enough. Let's do some trig...

Assume the average speed of an asteroid to be 20,000 miles per hour.
In ten years, an asteroid would travel 1,752,000,000 miles. (It might
need a new pair of shoes.)
The diameter of the earth is 7926.28 miles. Assuming the worst case,
that the asteroid was headed exactly towards the center of the earth,
we would need to deviate at most half of that (plus a little for
safety), say 4000 miles.
If I did my math right, the arctan(4000/1,752,000,000) = 1.303 x
10^-12 degrees. Or 2.28310502 × 10^-6 if Google did my math right. :-)
In any case, "not so much, really." Let's work with Google's number,
since it's bigger. The worst case.

Physics was too many years ago for me to finish the math, although I
tried for an hour or two. We may or may not be able to generate this
with current technology. But if there were a real asteroid with our
name on it, we would spend billions to figure it out (under ANY
political system :-)

Two guys way smarter than me wrote this paper though... that does
finish the math and physics.

I guess it IS rocket science... my head hurts.

>From the paper:
"Thus, in the example above, a 20 ton gravitational tractor can
deflect a typical 200m asteroid, given a lead time of 20 years. The
thrust and total fuel requirements of this mission are well
within the capability of proposed 100kW nuclear-electric propulsion
systems, using
about 4 tons of fuel to accomplish the typical 15 km/sec rendezvous
and about 400 Kg
for the actual deflection."	

I assume they are talking about some kind of Ion Thruster running on
nuclear power.

Then they talk about the specific real asteroid 99942 Apophis (2004
MN4), which will do a close swing by in 2029 and has a slight chance
of subsequently hitting earth in 2035 or 2036. It is 320 meters
across. They propose a mechanism for this special case that doesn't
even need the new nuclear propulsion system.

While this isn't easy, it sounds easier than poking a fork into a
super volcano. If something were heading our way, I think we would
give it a try. In the most probable case, we would get hundreds or
perhaps thousands of years of warning if we knew where all the
asteroids were in the solar system.

What I don't understand in the proposal is why they think they need to
take the 20 metric tons with them. (They do assume this because they
talk about the fuel requirements of getting the 20 tons there.) Why
not harvest the required mass from the asteroid itself and just take
the engines and a big bag to hold the asteroid parts with you? Load
up, then pull... For a thousand years, if necessary...


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