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NASA's Deep Impact
NivenMK1 writes "The Seattle Times has an interesting article on NASA's plan to nail the comet Tempel 1 with a chunk of copper the size of a bathtub on July 4 this year. This copper 'bullet' is intended to strike the comet at approximately 23,000 mph and hit with a force equivalent to 4.7 tons of TNT.
Scientists hope to discover what exactly the comet is made of and what changes have occurred to the outer layers with reference to the core."
Would it not be cheaper/better to drop a lump of high explosive on it rather than a heavy lump of copper?
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Why copper?
Is it because Tempel 1 is known to not contain any copper itself, so it makes the spectral signature easier to read?
Are there any possible issues like destruction of important "environments"(if a comet could be called an evironment) if the comet is blown to pieces by this experiment? I mean, is it possible that important microorganisms or other important/rare/valuable occurences may be destroyed if this comment is blown up? It kind of reminds me of some of the unintended consequences of mans earlier forays into new environments on earth. I just wonder if these kind of scenarios have been considered.
They'll develop a working missile defense system. All kidding aside how hard is it going to be to position this giant copper bullet in the path of a speeding comet? How acurately can they predict the comets path (whenever I here about near earth passes they are always given in wide ranges as to how near they actually came). So maybe I just naieve but the idea that we could hurl a giant block of metal into a comet traveling 23,000 miles per hour millions of miles away, I feel like a kid again at the wonderment.
Is this a test of a planetary defence system? Imagine if the dinosaurs could have had one of those.
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Am I the only one who feels this is the start to a disaster movie?
"The year is 2004, and the scientists of the day decide to crack open a comet with a bullet the size of a bathtub. But then the unthinkable happens. The comet bullet causes the comet to change path and come right towards Earth and there is nothing we can do to stop it. Will all Earth will be destroyed? Will our hero be able to save the world? There is only one way to find out..."
Coming to cinemas everywhere this Summer.
Possibily destroying a comet? It seems so destructive to possibly break apart something that's been circling our sun for millions of years.
Interesting set of priorities there... As for me, I can't wait until we get our act together enough to start mining all of those eons-old lumps of raw material instead of strip-mining our planet.
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You could make this "hands off" argument for anything. Moon rovers/landings, mars rovers, etc.
The question is, "Should we remain in ignorance to keep things pristine?"
Historically the answer is no and ethically it seems to be working pretty well. Comets that pass through our system number what? In the tens of thousands? More? I don't think this is as controversial as you might think, especially considering we've dropped all sorts of detritus and other "bullet-like" techniques (crashing stuff into planets) for science.
Something else is going on. They can pick pieces of comet out of the moon if they wanted it. No point in blowing money on this unless it's for defense. Copper my ass.
... or where the bullet nudges the comet just enough to perturb its orbit in such a way that it hits earth 15 years from now. I for one would very much like to know more about why this won't happen. It seems to me that the comet's unknown composition would render any predictions of the effect on its orbit meaningless.
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You could make this "hands off" argument for anything. Moon rovers/landings, mars rovers, etc. The question is, "Should we remain in ignorance to keep things pristine?"
Sure, you definitely have to run the risk of dirtying things up a bit in order to study them in most cases. I think that landing spacecraft on other planets is an acceptable tradeoff for the knowledge we gain.
It's the destructive nature of the Deep Impact study that made me pause. We've never really gone out and just smashed something in our solar system to bits before. The scientific gains might definitely outweigh the cost (agree with this mission or not, I can't wait to see the results) but it's not a step to be taken lightly and I hadn't seen that aspect of the mission touched upon in the coverage I've seen.
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How acurately can they predict the comets path (whenever I here about near earth passes they are always given in wide ranges as to how near they actually came).
You hear about near-Earth passes, as you call them, because they're always the first time we've noticed said object getting close to the Earth. This comet (and many others, plus asteroids, etc) has a pretty well-known orbit around the Sun. We have plenty of observations and can accurately predict where it's going to be at any given point in time (barring things like orbital changes due to outgassing, disintegration, etc).
There's another object in the sky that we can do this with: the Moon. It's VERY close to Earth, yet we can be pretty safe in saying it ain't about to hit us. Lots of observations == confidence in a body's motion.
The "scary" ones you hear about are new objects we've never seen before, and all of sudden they look like they're coming "close". Once we get enough observations of them, we can calculate their orbits, and you pretty much never hear about them again.
Endless arguments over trivial contradictions in books written by ignorant savages to explain thunder in the dark.
Hitting comet vs. Missile defense:
You left out the most important factor:
5. Comet has no acceleration except from (reliable) gravity. Missile has onboard thrusters that can push the object in unpredictable ways, such as to specifically evade the attack.
It's true that there are occasional comets which give of thrust, but that happens when they're close enough to a star to heat up and blast steam.
3.Comet is in a microgravity enviroment, bullet could stop and wait for comet vs. warheads
That's a pointless idea. In the depths of the solar system the concept of "stopping" is barely meaningful. The only way an object could "stop" would be to enter a stable orbit, which is still basically moving. Otherwise you'd still need "constant thrust" to fight gravity. It's far better to use a single-curve trajectory than to try and alter it like that.
Besides, you get more destructive power from a faster hit.
True, but if you send up an 820lb nuclear warhead you will get a much better fire cracker. Megatons baby, that's what I'm talking about, thousands of your piddly little copper lumps have I in a few pounds of Pu and hydrogen.
So you have to wonder when nations will start nuclear fireworks displays. People want bread, wine and circus. Science has to have it's element of circus to be funded. I hate myself for realizing that. Nations like to intimidate, and traditional fireworks displays included cannons and other military devices. Ah to be entertained by brute intimidation. When it happens, you know that the world is drifting back to feudalism.
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No, but the metric kilotonne of TNT is the standard unit for equivalent explosive energy. So when you hear people going on about how an explosive has the same energy content as X kt of TNT, they're really using the right unit. Explosions are complicated, so more fundamental measures like joules and such aren't really useful.