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Nukes Not the Best Way To Stop Asteroids, Says Apollo Astronaut
MajorTom writes "Right now, we are not tracking many of the asteroids that could destroy earth. But within the next decade, new telescopes will make that possible, and leave us with the tough decision of what to do about objects with an alarming chance of hitting our planet. Last year, NASA said that the best option is to nuke them. This week, Apollo astronaut Rusty Schweickart, explained that there are far better options, and he has started an organization to prove that they can work."
Move it into orbit and mine it.
He's saying pushing or pulling an asteroid is better than hitting it with a nuclear weapon, but the interesting thing is that he's claiming NASA issued its pro-nuclear statement last year in response to political pressure to put nuclear weapons in space.
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Not really. Let's say that the most we can do with a nuke is slow the asteroid down by 1 f/sec. Doesn't sound like much, does it? but if you do it 30 days before impact, that shifts the asteroid back almost 491 miles. If you have six months, it's over 2000 miles. Considering that the Earth is a moving target, that might be enough to ensure a miss. You're not trying to blow up the asteroid, you're just trying to nudge it into a slightly different orbit that doesn't impact the Earth, and if you have time, it doesn't take very much.
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AIUI, you have to have the blast very close to the surface, if not actually on it. The radiation from the blast will be enough to vaporize some small amount of the asteroid. That vapor will leave the asteroid very quickly in the direction the blast came from and the rest of it will move in the other direction, although very slowly. I agree that it's not going to be as effective as it would be in atmosphere, but there will be some acceleration from it, and as I pointed out in another post, it doesn't take very much if you can give it enough time to work.
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You don't get karma points for "funny" ratings, so some mods will give an exceptionally funny post an "insightful" rating instead. As Taco said, you have to be wise, not a wise-ass.
You don't get karma for "underrated" either, which is why that's not used instead.
Personally, I just rate the first 5 posts on idle as "overrated". It works out great. I get to ditch the mod points as fast as I can and statistically, I'm modding the posts correctly.
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Nukes are big lumps of dV, ion engines are small streams of dV. There's a range of options in between. Small, continuous thrust over time can equal large, impulse thrust over a few seconds.
It all depends on when you can identify and engage the celestial body under discussion. The less warning, the shorter the time you have to apply the necessary dV for the effect you want. The effect you want is a change in velocity vector, and how you need to change the moving body to go faster | slower | different direction depends entirely on the orbital mechanics of the individual event. Work the problem when you find out about it.
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Actually, I remember seeing some documentary on national Geographic (iirc), where they explored this exact topic.
The problems with nuking asteroids are (apparently) the inherent danger of radioactive fragments falling to earth and of course the fact that asteroids aren't actually solid --- they usually consist of a lot of small pieces of rock, hence making it hard to actually do anything to them with force. Of course, these weren't the only problems, but they're the ones I can remember. Might have been the same guy as the one from TFA pointing it out --- I'm not sure. Also, I'm a linguist, so my knowledge of astronomy and nukes is limited.
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The residual radiation from a nuclear blast is pretty much zero after a week. Ask any physicist who has visited Hiroshima or Nagasaki (i.e. me ;o) ). The idea that debris from a nuclear explosion is permanently radioactive (and maybe glows green!) comes from fiction.
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Actually wouldn't it be easier to just not build the better telescopes. That way things don't change. Outta sight, outta mind!
I think we've got the 'getting it up there' part figured out already...
Not if your payload includes a million ton pusher plate. The only way we could launch an orion would be to fly it as a pulse rocket directly from the ground. Which is how it was done in Footfall.
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Even then, if you do the math on how much of the fragments will be radioactive (and how much) and how much of this will become embedded in bed rock (or deep in the oceans), I really doubt the radioactivity caused by the nuclear blast will have much effect. And depending on where the unfragmented asteroid hits, there's also a chance that the ejecta from that impact will include massive stores of radioative waste from the nuclear power industry.
We do not live in the 21st century. We live in the 20 second century.
Weapons effects are extremely interesting and useful. The first effect to know about is that stuff survives amazingly close to a nuclear explosion. The second effect is that you can "tune" a fission bomb to direct its energy output largely in one direction. (Don't jump on me, this is in the open literature now.) Which gives a different method of dealing with asteroids; a series of powerful, but not shattering, plasma "slaps" to change its orbit.
Send a spacecraft armed with lots of quite small fission weapons that are set up to direct their weapons effects mostly in one direction and with a very basic, robust guidance system. Each one needs to get tossed out, line up with the asteroid, trigger, and "slap" it with high-speed plasma. Enough "slaps" change its orbital characteristics. You don't try to shatter it.
Each fission weapon looks like this: Wrap up a small (5 kt?) fission core with something like polyethylene or anything that absorbs prompt soft X-rays. Anything that has mass. The onboard computer works with guidance (my guess would be aims for a laser point on the asteroid, but who knows), the guidance just lines it up properly with the asteroid, and triggers the fission.
Position it so that when it goes off, the plasma of the polyethylene (and the former physics package, etc), moving around 2.5 million miles per hour, strikes the asteroid. You don't try to break the asteroid up -- far from it. You go for a series of "slaps" with very hot material. As the physics formula says, Mass times Velocity Squared -- and here you have all kinds of velocity.
As Lew Allen proved, with his famous tests with steel spheres just a few feet from ground-zero of a nuclear test survive just fine, and they are accelerated quite briskly. This was one basis of Project Orion later on.
It would be quite interesting to model this against some asteroid sizes and get an idea of what would be required to change the trajectory. We certainly have enough plutonium cores laying around.
Just an interesting thought.
Thanks,
Dave Small
It was a nefarious excuse to put nuclear weapons in space.
Unfortunately, it looks like a hidden agenda is behind quite a bit of space policy.
Space solar power (now abandoned) was another attempt at getting weapons into space: collecting solar energy in space makes no economic sense, but it does make sense as an excuse to get a giant, city busting energy weapon into space.
Nuclear propulsion is another such attempt: it makes no sense for solar system exploration, but it does make sense as an excuse to get atom bombs into space.