Comet in September 2015

Originally posted by humy
Oh yes, I remember the evolutionary absurd cute cuddly bears with their strangely poorly evolved body form for walking or running despite the fact they seemed to do a lot of both, and with the their silly sounding childish noises they make for communication that strangely doesn't sound like it actually consists of any words, and their heroic fight against the " ...[text shortened]... o anything very physical let alone deadly fighting.

What a totally ridiculous script.

The Force was with them.

You just have to keep saying that to yourself.

Originally posted by twhitehead
How 'biblically huge' exactly? according to Wikipedia, the Chelyabinsk meteor, released the energy equivalent of 500 kilotons of TNT.
The only reason it caused serious damage - consisting of mostly broken windows, is because it exploded. Had it been composed of smaller pieces, there would have been practically no significant side effects at ground level ...[text shortened]... ig hole in the ground.
Please show at least back of hand calculation to justify that claim.[/b]

We are talking about multi-kilometer wide asteroids/comets.

What conversation are you having?

Originally posted by sonhouse
I used 3 grams/cm^3 for the mass, and came up with about 500 million tons for a 1 Km diameter rocky asteroid. I thought millions of trillions of tons was a bit off🙂 Take a look at an aircraft carrier, 100,000 tons and it is about 1200 feet long, about 360 meters, or .36 km. You couldn't fit more than ten or twenty of them inside a 1 km asteroid. I think your numbers are a bit off.

My bad. I just re looked at the calculation and found a few extraneous zeros in the radius [which I then cubed]. 😕

Still, I still get a DeltaV in the 100th's to 10th's of a mm/s of off equivalent thrust.

Bearing in mind that the Earth is ~13,000km across, a dead on hit would need to be deflected by
at least 6,500km. And bearing in mind that Earth's gravity is going to pull it in from a distance out
so you have to deflect it far enough away that it doesn't just get pulled back in.
[A glancing blow would need less deflection, however the deflection needed to avoid the object being pulled in
by Earth's own gravity is going to be larger than one Earth radius, so I am using that as the minimum]

A hundredth of a mm/s will get you 6,500km over ~750 days. which means that these multi-megaton
nukes need to hit >~2 years away from impact.

While vaporising some of the asteroid/comet will add thrust, a large shock-wave could blast materiel off
the far side of the asteroid/comet, which will act as a counter thrust.

Deep internal detonations will have almost no effect as the blast will be roughly omnidirectional,
and you need epically huge nukes [that we don't posses] to overcome the internal gravitational binding
energy of a multi km object.



There is a reason that every time they do a documentary on asteroid deflection the first thing they say is
we've looked at deflecting these with nukes and then decided to do something [almost anything] else.

If we see one weeks/months out, nukes are going to do nothing other than make it radioactive, and change
where it hits.

Originally posted by humy
Oh yes, I remember the evolutionary absurd cute cuddly bears with their strangely poorly evolved body form for walking or running despite the fact they seemed to do a lot of both, and with the their silly sounding childish noises they make for communication that strangely doesn't sound like it actually consists of any words, and their heroic fight against the " ...[text shortened]... o anything very physical let alone deadly fighting.

What a totally ridiculous script.

I think you may be over-thinking this.

Originally posted by Soothfast
The Force was with them.

You just have to keep saying that to yourself.

As someone once observed: Star Wars makes much more sense if you replace all references to "The Force" with "The Scriptwriter".

Originally posted by googlefudge
My bad. I just re looked at the calculation and found a few extraneous zeros in the radius [which I then cubed]. 😕

Still, I still get a DeltaV in the 100th's to 10th's of a mm/s of off equivalent thrust.

Bearing in mind that the Earth is ~13,000km across, a dead on hit would need to be deflected by
at least 6,500km. And bearing in mind that Eart ...[text shortened]... s out, nukes are going to do nothing other than make it radioactive, and change
where it hits.

Another way to look at the issue is to view the asteroid as a resource. Send out a hundred robot craft with powerful lasers, cut the sucker up in pieces and ship it all to Earth and sell the resultant bounty in metals and maybe diamonds🙂

Originally posted by sonhouse
Another way to look at the issue is to view the asteroid as a resource. Send out a hundred robot craft with powerful lasers, cut the sucker up in pieces and ship it all to Earth and sell the resultant bounty in metals and maybe diamonds🙂

Very unlikely to find diamonds [other than diamond dust] in asteroids as they never had
the crushing pressures and high temperatures needed to slowly form large diamonds.

But yes they have lots of rare earth metals, which are very valuable on Earth.
And they have lots of water Ice, which is vary valuable in space.