[ExI] (NASA.gov) NASA to chronicle close Earth flyby of asteroid (fwd)
pharos at gmail.com
Sat Feb 16 23:29:10 UTC 2013
On Sat, Feb 16, 2013 at 10:33 PM, spike wrote:
> Regarding your notion of a physical impact, this might transfer some
> momentum, and here's how you estimate how much: find the speed of sound in
> the rock, take the closing speed and calculate a cone going aft from impact
> site outward along the path of the impact. Then calculate a cone with the
> longitudinal axis being the closing velocity and both transverse axes being
> the speed of sound in the rock. So if you have a closing speed of about 10
> km/sec and you estimate the speed of sound in the rock at about a km/sec,
> the half-angle of the cone is about 6 degrees. So now the total momentum
> transfer to the rock is calculated by estimating the surface area of that
> cone, multiplying by the sheer strength of the rocky material. That would
> give you an area times a force per unit area, from which you estimate a
> force. You know the time span during which the force is being applied, so
> we might be able to estimate the momentum transfer with that. You end up
> with a conic shaped hole in the rock, the size and shape of the impactor on
> the impact side, an opening at perhaps 6 degrees going aft. The rest of the
> rock scarcely notice that anything has happened.
Although DA14 missed earth by about 17,000 miles, in keyhole terms it
missed by just 14 minutes. So just a small speedup or slowdown is
sufficient to make an asteroid miss earth.
Apparently Los Alamos has had a super computer running simulations of
nuking an asteroid and they think it will probably work OK, if no
earlier intervention is possible.
They came up with ten possible fixes:
Strap Solar Sails to It
Point Mirrors at It
Strap a Rocket to It
Tow It with Gravity
Have Robots Munch on It
Brace for Impact!
But earth could do with having more powerful space tech available, to
make these solutions more viable.
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