TEPCO Rose

[PamW]

31. I'll have to send this to my colleague..

FBaggins,

I will have to send this to a Lab colleague who is one of the top experts in the field of asteroid deflection using nuclear weapons.

If the asteroid is a real "planet killer" like the one that killed the dinosaurs, or if we get a comet like the Shoemaker-Levy 9 comet that bombarded Jupiter several years ago where we don't have 20 to 40 years of advanced notice to deflect the comet; nuclear weapons are the best and only hope.

I just saw a program out of Australia that considered the nuclear option in terms of blasting the comet / asteroid to bits. You don't want / need to do that; you want to deflect it.

You want to put the object into an orbit that doesn't intersect the Earth's orbit. Every orbit is characterized by its energy. For example, let's take the simplest case of a circular orbit. The acceleration of an object in circular orbit is v^2/r ( velocity squared over radius ). If the object is going to be in stable orbit, then the acceleration of the object in orbit has to equal the acceleration of gravity, g. Thus the condition for circular orbit is v^2/r = g. Now let's multiply top and bottom of the fraction by the mass m of the object. Doing so is equivalent to multiplying by 1. 2 ( 1/2 mv^2 ) / mr = g. The quantity in parentheses is the kinetic energy of the object, E. So we can rewrite this as:

2E/mr = g

Now if you want to increase the orbital radius r; you have to increase the orbital energy by the same percentage so that the above equation remains valid for the new orbit.

So if you want to deflect an asteroid to a higher orbit that doesn't cross the Earth's orbit; you have to give it some more energy. If we are going to deflect the object; we have to supply the energy.

These objects are big and we are talking about large amounts of energy. Additionally, we have to transport that energy to space; and we can't lift massive objects to space. It takes big rockets to get Shuttles and capsules into orbit. It took the Saturn V to lift a 3rd stage that was powerful enough to send a little Apollo command / service module and LEM to the moon.

So we need a lot of energy in a light package. The best we have for that is nuclear weapons.

You don't blow up the asteroid. You blow up the nuclear weapon NEAR the asteroid. The radiation from the bomb will vaporize part of the objects surface, and that will blow off. The reaction to that blow off accelerates the object away from the bomb. That's how we put a lot of energy into a comet or asteroid.

http://education.llnl.gov/sos/lecture/427/

http://education.llnl.gov/sos/lecture/427/bios

I'll make sure Dave gets a copy of the above. Thanks.

PamW