Blast in space?

mheslep

What might be required so that the asteroid is fragmented into parts small enough to burn up in earth atmosphere?

DaveC426913

Very difficult to ensure it ALL gets reduced to small enough pieces. And simulations show that it is possible the many smaller hits could have a much worse effect than one large one.

This the the riskiest of all options.

Morbius

Bob,

The kinetic energy delivered to the asteroid is NOT NEGLIGIBLE. In fact, by ablating the surface of the asteroid, the amount of kinetic energy / momentum imparted to the asteroid beats anything that a rocket or "impactor" can do by orders of magnitude.

As was stated in the article on Dr. Dearborn that I referenced earlier - if the object is large or the time scale to deflect it is short - then nuclear weapons are our ONLY methodology, and our only hope.

Dr. Gregory Greenman

Morbius

You carry it on a missile. The majority of the work is to get to Earth orbit. For the Moon mission, getting to Earth orbit required the large first and second stages of the Saturn V.
The energy to get from Earth orbit to the Moon was delivered by the relatively modest third stage.

We have missiles that can carry a multiple warhead payload to high, but suborbital trajectory. If we reduced the payload to a single warhead, we can send the warhead a great distance.

The distance is many miles. The optimal distance is a certain fraction of the object's "diameter". I don't think the warhead is going to be in danger of being damaged before detonation, and those warheads were made to be reliable.

Dr. Dearborn shows scenes from Armageddon in his seminars as an example of what NOT to do.

Dr. Gregory Greenman

Morbius

Joe,

Kinetic kill vs nuclear weapon was very heavily studied by LLNL back in the 1990s.

The nuclear weapon can deliver orders of magnitude more energy than can a kinetic kill.

The idea is we want to change the orbit of the asteroid, and that takes energy. If the asteroid is large, we have no way with our chemical rockets to put enough energy into a kinetic kill vehicle to be able to deflect a very large asteroid.

Again, for very large asteroids, or very short time for deflection; the nuclear weapon is the ONLY viable option. It beats kinetic impactors, "gravity tractors"... hands down.

One of the other problems with kinetic kill is that many of the asteroids are what are called "rubble piles". They are not one rock, but a bunch of rocks held loosely together by mutual gravity. A kinetic kill will deflect the rock it hits in a rubble plie, but won't deflect the bulk of the others. The only force between the impacted rock and some of the others is gravity, and gravity is too weak for the short time scale to impart enough momentum.

Dr. Gregory Greenman

Morbius

NO - your feeble attempt above is "spin". If you "think" that what you posted is exactly what I did - then you still don't understand it. Shall we recall what you posted in post #9:

If a nuke is detonated in the near perfect vacuum of space, there isn't anything more than the matter contained within the bomb itself that will expand."

This is WRONG since you state "there isn't anything more than the matter contained within the bomb itself that will expand".

I CORRECTED that by saying there is a lot more to a nuclear explosion in space than just the expansion of bomb debris. There is one hell of a lot of energy contained in the accompanying radiation wave.

More to the point, it's the energy of that radiation, and not the energy of the expanding debris that is used to deflect asteroids. So you left out the most important part about deflecting asteroids, and now you arrogantly say that your representation is exactly the same as what I am saying.

Dr. Gregory Greenman

Morbius

Dr Dearborn calculates the optimal height for maximal effect, and if memory serves the optimal distance is measured in miles and not feet.

Dr. Gregory Greenman

Joseph Chikva

So, your statement is to explode nuke warhead carried on interceptor missile after hit?

If so:
• What deceleration that warhead will experience after hit before explosion?
• And admissible deceleration for reliable operation of mechanisms?

And I doubt that existing MCBMs can be used. I am sure that new interceptor should be developed. That would not be a problem on base of just today's technology. But that will be a new missile much more agile than MCBM.

Joseph Chikva

Ok, thanks.

Morbius

Joe,

Not at all. You don't have to hit the asteroid. You want to explode it a few miles above the surface, so you arrange for the missile's trajectory to pass just in front of, or just behind ( depending on what new orbit is desired ) and you detonate the warhead at the proper time.

There's no "hitting" the asteroid involved.

Dr. Gregory Greenman

Drakkith

As Morbius said there is no need to hit the asteroid. Current warheads are already equipped with the ability to detonate at different altitudes either based on time or proximity/impact. Actually, the cruise missiles I work on have impact fuzes in the nose for a ground burst detonation option. It is trivial to time the detonation right down to milliseconds or less.

Joseph Chikva

Ok, Greg,
I understood that from your second another post. Thanks.
Very little amount of energy can be delivered in that case. Was that calculated?

Joseph Chikva

I know something about warheads, fuses, as well as proximity, point detonating, delay modes. Thanks.
As some times ago proposed to my country’s Government to produce modern fuses here in Georgia http://www.fuchs.co.za/technology/

Drakkith

Why would very little energy be delivered? I'd venture a guess and say that if you got really close you could get 40%+ of the energy of the nuke transferred to the asteroid.

Joseph Chikva

From what do you get numbers?
Not only in this case.
Radiation propagated to all directions (4pi steradian).
Distance to asteroid a few miles.
Bob mentioned asteroid’s mass M = 8.6 x 10^7 tonnes (metric tons).
It corresponds ~1.1 x 10^7 m3 of volume if asteroid is from iron and about 10^8 if from ice.
If asteroid spherical the diameter should has an order of a few hundred meters.
And if even if 100% radiation energy absorption much less than 40%. But some energy will be reflected.

Drakkith

Hrmm, I guess I should have been more specific. I meant that if a nuke is detonated above the surface of an asteroid, at least 50% of the blast will simply go into space above. The other 50% should interact with the asteroid somehow. I took 10% away simply because I don't think exactly 50% will hit the asteroid due to the altitude of the blast. Some should get radiated close to the asteroid but barely miss it.

Joseph Chikva

If you have an interest you can estimate that on base of provided by me data.
That is an elementary geometry exercise.
I am too lazy for that.
But think that on a few orders lower than you guess.