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originally posted by: Spacespider
Just because these plans now exist does not mean the spacecraft will ever get built. NASA scientists declined to give a cost estimate for a mission, citing the sensitivity of pricing information
While they having a bright Idea.. we could get blown to bits..
Get to work NASA !
It depends on the size, mass, composition, trajectory, and amount of lead time. The problem with using nuclear weapons is that they produce a rather large but short-term impulse. As an analogy, imagine a paper grocery sack that is full of heavy items. We must pick it up in just the right way, and not to quickly, or we’ll tear the paper. We don’t want to “stop” the asteroid, and we don’t want to blow it into a lot of little pieces, either.
What we want to do is to change its velocity so that its projected trajectory no longer intersects with the Earth’s.
In general, some number of small pushes would be better than one push, and the longer ahead of time, the more a small change in velocity has on the trajectory. So, if nuclear explosions are to be used, more than likely it would be a series of fairly small ones, at intervals, to provide a series of impulses with minimal damage to the asteroid, and also to allow time to evaluate the effects on the trajectory.
One thing that must be considered is that the thrust vector must be directed through the center of gravity, and in the desired direction.
In addition, asteroids have some rate of tumble, which can be very complex and means that anything placed on the surface of the asteroid must take that into consideration—a daunting challenge indeed, because the timing of an impulse would be critical and have only certain moments of opportunity.
Detonation of the device(s) some distance away in the right direction from the asteroid would reduce the effect on the asteroid’s tumble rate, but it would also greatly affect the overall amount of impulse effect. This is because impulse is the product of mass and velocity. The nuclear device, in and of itself, including the spacecraft carrying it, contains very little mass, albeit at a very high velocity.
However, the radiation energy impinging on the asteroid would heat up the surface and cause matter to be ejected, resulting in thrust, but the control of the direction would be very complex. The bottom line is that the reaction mass needed to influence the trajectory of the asteroid must come from somewhere, and that is going to have be from the asteroid itself. Hence the device must be a surface-based “groundburst,” so that the ejected mass (perhaps thousands or even millions of tons) produces the necessary thrust, and again at the precise time and location to have the desired effect.
originally posted by: intrptr
a reply to: swanne
NASA, in association with NNSA and several other departments, have just announced an official governmental plan to use nuclear heads to "protect against asteroids".
Thats not a viable option. The object may fragment, come at us in shotgun spread pattern, actually increasing the odds of something hitting us, not lessening it.
originally posted by: Bhadhidar
And radiation, not very effective against an asteroid that has been bathed in radiation (cosmic rays) it’s entire life.
originally posted by: 5StarOracle
I dont see nukes as the best solution to suck a problem...
What would be wrong with a space craft that could attach itself to an incoming body and with thrust alter it's path?
originally posted by: mbkennel
originally posted by: 5StarOracle
I dont see nukes as the best solution to suck a problem...
What would be wrong with a space craft that could attach itself to an incoming body and with thrust alter it's path?
Nothing, other than difficulty, expense, energy source and fuel for momentum transfer. If you can over come those, then it's a better solution.