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Space Science

NASA's Deep Impact 314

Posted by timothy
from the metric-bathtub-or-imperial dept.
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."
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NASA's Deep Impact

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  • Hit when? (Score:5, Funny)

    by ceeam (39911) on Sunday November 28, 2004 @08:37AM (#10936585)
    July 4 this year?! What a coincidence - it's the date the project I'm working on now should be finished to.
    • Will it coincide with an Alien attack and the president flying into it to plant a virus ?.
    • They must be using a different calendar.
  • by Linker3000 (626634) on Sunday November 28, 2004 @08:37AM (#10936586) Journal
    ...where the bullet misses its target and curves back round to origin.

    Don't miss guys - and watch out for Hubble!
    • ... 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.
  • by FireFury03 (653718) <slashdotNO@SPAMnexusuk.org> on Sunday November 28, 2004 @08:40AM (#10936591) Homepage

    Would it not be cheaper/better to drop a lump of high explosive on it rather than a heavy lump of copper?
    • by imsabbel (611519) on Sunday November 28, 2004 @08:43AM (#10936602)
      You want to analyse the comet, which you can do by looking at the emission lines of the cloud forming after the impact, ect.
      An explosive is normally composed of chemically very reactive components, that can react with each other and the material of the comet, making it very hard to discern what WAS there and what was created by the blast.
      • Forgot one thing: (Score:5, Insightful)

        by imsabbel (611519) on Sunday November 28, 2004 @09:03AM (#10936666)
        Look at the numbers:
        The impact power of the copper rod is 4+ tonnes of TNT. IF you wanted to double the blast, you would have to send more than 4 tonnes of explosives.
        at 30km/s+, the kinetic energy of the material is bigger than the chemical energy of explosives.
        The added energy just doesnt matter anymore because it would be difficult to time the blast, plus the softness of the explosives would reduce the impact penetration.
      • by p_trekkie (597206) on Sunday November 28, 2004 @11:03AM (#10937043) Homepage
        Another reason they are doing a kinetic impact is because they want to judge the structure of the comet. Right now, scientists don't really know if the comet's consistency is that of a fluffy snowball or a hard chunk of ice. If you used explosives, you would have melting of the ice, whatever its consistency, and would get less information about the construction of the comet. Once possibility is that the comet might be loosely packed enough that the impactor goes in one side and flies out the other....

        Also, I'm surprised the article submitter didn't include a link [umd.edu] to the mission website.....
    • Explosive will heat up the comet, leave pollution, and make analysis of the dust very hard....
    • by HeghmoH (13204) on Sunday November 28, 2004 @09:03AM (#10936669) Homepage Journal
      The lump of copper is 820 pounds, and will be equivalent to 5 tons of TNT. If you sent an 820-pound lump of TNT, you would get an explosion of about 5.4 tons of TNT. An extra .4 tons-TNT increase, in exchange for a vastly more dangerous mission and chemical contamination is not a good trade.

      At these speeds, the kinetic energy is so great that chemical explosives are nearly pointless.
      • by Mod Me God Five (832071) on Sunday November 28, 2004 @09:20AM (#10936713)
        And millions of years from now the aliens invezstigating the comet will scratch their heads thinking 'why is there a piece of copper the size of a bathtub on this comet'. Far greater amusement factor.
      • The lump of copper is 820 pounds, and will be equivalent to 5 tons of TNT. If you sent an 820-pound lump of TNT, you would get an explosion of about 5.4 tons of TNT. An extra .4 tons-TNT increase, in exchange for a vastly more dangerous mission and chemical contamination is not a good trade.

        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 hy

      • by luna69 (529007) *
        Ok, sorry in advance for being nitpicky but I enjoy this sort of thing. Mea culpa.

        A quick calculation shows that the OP figure of 4.7 tons of TNT is high by about 0.12 ton TNT equiv.:

        KE = 0.5 * 370kg * (23000mph)^2 = 1.956E17 ergs

        1 ton TNT = 4.26E16 ergs (rough, but fairly good approx.)

        1.95E17 ergs / (4.26E16 ergs) = 4.58 ton TNT equiv.
      • At these speeds, the kinetic energy is so great that chemical explosives are nearly pointless
        Which is why, if alien wanted to destroy civilisation on Earth, they wouldn't come firing with laser guns like in most sci-fi flicks, but just slowly accelerate a bunch of moderate size asteroids over the course of some decades/centuries.
      • Whoa slow down. So let me get this straight 820 pds TNT = 5.4 tonnes of TNT?

        Dude you need the metric system SO BAD!

        However 820 pounds is quite a bit of weight to throw up there and accelerate around, isn't a satellite like 1kg these days?

        They must be really looking for something, fossil fuels? But they won't have any Arab's to bomb, I don't think the U.S. government will go for it.
    • by f4llenang3l (834942) on Sunday November 28, 2004 @09:29AM (#10936741)
      I don't think the emission lines would actually provide much of a problem, it would be pretty easy to filter out the gaseous emissions of the explosives... I think the greater problem would be the unpredictability of the momentum problem if you added a chemical explosion. With a solid projectile, you can expect to learn a lot about the comet simply by what happens to the path of the intercepting projectile- ie shooting the snowball example. But, if you shoot a snowball with an RPG, or an iceball with an RPG, it's a lot harder to look at the resulting dispersion and tell what the target was made of after the fact.
    • by Odin's Raven (145278) on Sunday November 28, 2004 @10:22AM (#10936887)
      Would it not be cheaper/better to drop a lump of high explosive on it rather than a heavy lump of copper?

      Given NASA's budget, copper made more sense. Finding themselves unable to afford chemical or nuclear explosives, NASA employees have spent the last four years collecting stray pennies - checking under seat cushions in taxis, keeping a watchful eye on the sidewalks and streets near their offices, and so on and so forth. Also, twice a year they held bake sales in the Vistor's Center where purchases had to be paid for entirely in pennies. Since they also lacked the budget to purchase a safe, or even a large piggy bank, one enterprising employee scrounged an old bathtub from a nearby dump, and placed it in the hall outside the Deep Impact lab for people to toss the pennies into. (Which is why the project is using the new "size of a bathtub" metric instead of the international "Volkswagon" unit of measurement.)

    • Hmmm let's see a bathtube sized piece of copper or 4.7 million tons of TNT as in 4.7 mega tons. A "lumb" of high explosive at that weight equivalence is called a nuke, and the odds of that happening are about zero.
  • by Ramsey-07 (737166) on Sunday November 28, 2004 @08:41AM (#10936593)
    ....But hitting a rock on Independance day sounds like a bad idea, what if it's an Alien's rock?

    We can't just keep going around the Solar system bashing things up that's not ours!
    • by lxt (724570) on Sunday November 28, 2004 @08:44AM (#10936604) Journal
      To be honest, I think I many more people wouldn't mind the White House being destroyed by aliens this time around... :)
  • Silly question... (Score:5, Interesting)

    by Anonymous Coward on Sunday November 28, 2004 @08:43AM (#10936601)
    Why copper?

    Is it because Tempel 1 is known to not contain any copper itself, so it makes the spectral signature easier to read?

    • Re:Silly question... (Score:2, Informative)

      by MoonFog (586818)
      Nobody's sure what will happen next. There's a small chance the impactor will blow the 2-½-mile-long comet to smithereens, or simply bore through it like a bullet through a snowball. More likely, scientists say, it will blast open a crater the size of a football stadium. It all depends on what Tempel 1 is made of, and how sturdily it is composed. Which is exactly what scientists hope to learn.

      In essence it appears they don't know jack shit what it really contains.
      • Comets are usually ice and frozen gases (dry ice, ammonia ...etc.)

        Heavy metals are very rare in comets . Also copper over iron , because copper is much more rarer than iron . Aluminium or Iron would be too common , silver/gold would be better than copper - but who can afford that :)
        • Heavy metals are very rare in comets

          Shame they didn't take this opportunity to rid the home world of an equal weight of plutonium.*

          *No, actually I do not wish to hear about what would happen if the rocket blew up during liftoff, and neither do I wish to hear about what would happen to somebody attempting to assemble that much plutonium into a single piece, or if the Bad Guys got hold of it prior to launch, or the terrible health effects on the poor techs who have to work with it, or ...... ah, fuckit.

    • Re:Silly question... (Score:5, Informative)

      by XenonDif (670717) on Sunday November 28, 2004 @09:49AM (#10936783)
      to quote NASA:

      "The impactor is made primarily of copper (49%) as opposed to aluminum (24%) because it minimizes corruption of spectral emission lines that are used to analyze the nucleus."

      http://deepimpact.jpl.nasa.gov/tech/impactor.html [nasa.gov]

    • Nasa should get funding from the NRA (National Rifle Assoc.) and Smith and Wesson. This will be the largest bullet ever made!
  • by Anonymous Coward on Sunday November 28, 2004 @08:44AM (#10936608)
    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.

  • by rseuhs (322520) on Sunday November 28, 2004 @08:48AM (#10936619)
    ... to step up and tell us that we can't do that and we are destroying nature.

  • 23,000 mph (Score:5, Insightful)

    by ari_j (90255) on Sunday November 28, 2004 @08:48AM (#10936623)
    The article doesn't state if this velocity is relative to Cape Cod or relative to the comet. It makes a big difference.
  • Maybe next... (Score:3, Interesting)

    by Tropaios (244000) <tropaiosNO@SPAMyahoo.com> on Sunday November 28, 2004 @08:50AM (#10936629)
    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.
    • by freeweed (309734) on Sunday November 28, 2004 @11:46AM (#10937212)
      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.
  • Sadly (Score:5, Funny)

    by eclectro (227083) on Sunday November 28, 2004 @08:52AM (#10936634)

    Our comets are now under attack. Please join the Society for the Preservation of Comets, before it's too late.

    Hopefully together we can make a difference. It's time to stop these bigoted scientists from damaging comets with bathtub size copper slugs, just "to see what will happen."

    Without comets, there would be no space snowballs. This must stop.

  • by zecg (521666) on Sunday November 28, 2004 @08:54AM (#10936641)
    ...NASA is lying. The comet is actually heading straight for Earth and the best plan they have is to launch a copper bathtub filled with Bruce Willis.
  • by Anonymous Coward on Sunday November 28, 2004 @09:02AM (#10936660)
    Was to scour the earth and gather together the meanest ex-con alcoholic drilling team humankind has to offer, and land them on the comet with a couple of nuclear warheads for this experiment.

    Unfortunately, the MPAA sent a cease and desist order to NASA informing them that this would be infringing on the IP of one of their client's copyrighted movies.

    Hence, plan B involves throwing a bathtub at the comet instead. Go NASA!

  • Weapon test? (Score:3, Interesting)

    by datadriven (699893) on Sunday November 28, 2004 @09:07AM (#10936677) Homepage
    Is this a test of a planetary defence system? Imagine if the dinosaurs could have had one of those.
  • End of the Earth? (Score:2, Interesting)

    by miaDWZ (820679)
    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.
  • by Da w00t (1789) * on Sunday November 28, 2004 @09:12AM (#10936692) Homepage
    ... and play asteroids? 8-)
    > . . O
    I can just see the "bullet" hitting the asteroid, but .. we've only got one bullet, so how in the heck are we going to deal with the bits of asteroid from the big one? I mean, the entire point of firing up on the asteroid in the first place was to vaporise it. They think one shot will do it? C'mon, we all know from experience that you have to break it down to advnace to the next level.
  • I've loved astronomy on a casual basis since childhood and I think it's important to mankind. I'm not one of those people who thinks we should abandon NASA spending because there are still underprivilidged marmasets living in a swamp somewhere or whatever.

    But isn't this kind of, uh... wrong? Possibily destroying a comet? It seems so destructive to possibly break apart something that's been circling our sun for millions of years.

    I understand that comets are more like "dirty snowballs" than things of infinite beauty, and I can definitely understand the scientific reasons for this mission because they're going to get all kinds of data that they couldn't get otherwise.

    This seems kind of wrong to me, though.
    • by f4llenang3l (834942) on Sunday November 28, 2004 @09:24AM (#10936726)
      It seems so destructive to possibly break apart something that's been circling our sun for millions of years.
      Have you looked out your window recently?
    • by JerkBoB (7130) on Sunday November 28, 2004 @10:01AM (#10936814)
      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.
      • 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.

        Where did I imply that I was in favor of strip-mining (or any other destructive process involving) the Earth?

        And how does the Deep Impact mission have anything to do with mining? If you knew anything about the makeup of comets, you'd know that they're basically dirty snowballs. Not "lumps of raw material" yo
        • by JerkBoB (7130) on Sunday November 28, 2004 @12:16PM (#10937338)
          If you knew anything about the makeup of comets, you'd know that they're basically dirty snowballs.

          Actually, we don't really know everything about the makeup of comets. In fact, that's the whole point of this mission: to find out more about what makes up comets. Our best guesses, based on data gathered during previous flybys and deductive reasoning, indicate that comets are mostly frozen water and some rocks mixed in, but we don't really know because we've never seen the inside of one.

          Anyhow, it's not as if we're randomly blasting apart any and every comet that comes our way. We're not nuking Halley's Comet or anything.

          As far as the mining issue is concerned, Deep Impact doesn't have anything to do with mining, directly. However, it adds to a body of research which could be used in the future. Even if comets typically don't have much more than water and some rocks, what better way to get a heck of a lot of water to Luna than to figure out a way to divert a comet into a lunar orbit? What if we need to figure out a way to divert/destroy a comet that's coming in too close for comfort? Etc. etc. It's empirical data that could be used in the future. It's not just fireworks, as you seem to be implying.

          The intent of my post was not to question your intelligence, but I had to address what seemed to me to be a somewhat short-sighted and unimaginative perspective.
    • 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 plane
      • 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 somethin
    • There are, depending on who you ask, at least several billion comets in the solar system. *One* of them won't be missed. And they aren't like archeological sites, where every one is unique, either.
  • by Grey Ninja (739021) on Sunday November 28, 2004 @09:25AM (#10936728) Homepage Journal
    What happens if the comet doesn't like being shot with the world's biggest bullet, and decides to come after us? Has NASA factored this into their plans?
  • NASA Website (Score:5, Informative)

    by themo0c0w (594693) on Sunday November 28, 2004 @09:27AM (#10936735)

    This project has been around since 2001; probably a dup /. article somewhere... Anyway, here is the NASA website, which gives more details on the mission.

    http://deepimpact.jpl.nasa.gov/ [nasa.gov]

  • The geeks at NASA never really grew up: Their jobs are all about neat toys and breaking things.

    Amazing that despite all our centuries of civilized sophistication the best way to figure out how things work is still to break them. Kids break clocks. Cooks break locks. NASA breaks giant icy rocks.

  • With our track record for slamming into things we should bounce off and hitting things we should miss, I'm certain that it would be one of the few missions to miss the thing we should hit...

    Captains additional: Does this mean we can add 'bath tub' to the ISO weights and measures along with VW Beetle, football field and 18 wheel truck?

  • 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.
    • Pieces of comet on the moon will be intermingled with moon materials and a variety of meteorites. Too polluted to get meaningful data. Furthermore, the heat from the collision with the moon, and the passage of time, would drive off volatile components.


      That said, there is value from the "defense" standpoint - defense against comets colliding with earth. This experiment may give some indication of how much of a shattering effect throwing things at a comet will have.

  • by Performaman (735106) <Peterjones@gmai[ ]om ['l.c' in gap]> on Sunday November 28, 2004 @12:03PM (#10937277)
    I once spoke to someone who works on the Deep Impact project, and he said that, after the Mars Polar Odyssey crashed, their motto became "Deep Impact: We're Supposed to Crash."
  • Units (Score:3, Funny)

    by Simon Garlick (104721) on Sunday November 28, 2004 @12:27PM (#10937393)
    So, the ton of TNT is now a unit of force?
  • Uh! (Score:2, Funny)

    by radpole (39181)
    I hope the aliens onboard the spaceship inside the comet don't mind.
  • Kill it!!!! (Score:5, Funny)

    by Anonymous Coward on Sunday November 28, 2004 @01:14PM (#10937612)
    Leave it to Americans to come up with a plan along the lines of: "Wonder what that's made of... lets blow it up!"
  • All they have to do is get the Genesis team to try to gently land the copper bullet onto the comet.
  • I'm sure they must be doing this, but I hadn't read of anyone speculating. This would be an excellent opportunity to direct the slug in, to change the comet's path slightly, and then measure the resultant path and check on their accuracy.

    I'm pretty sure we're going to need that capability sooner or later.

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