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NASA Space

NASA's DART Spacecraft Hits Target Asteroid in First Planetary Defense Test (reuters.com) 105

Posted by msmash from the moving-forward dept.
NASA's DART spacecraft successfully slammed into a distant asteroid at hypersonic speed on Monday in the world's first test of a planetary defense system, designed to prevent a potential doomsday meteorite collision with Earth. From a report: Humanity's first attempt to alter the motion of an asteroid or any celestial body played out in a NASA webcast from the mission operations center outside Washington, D.C., 10 months after DART was launched. The livestream showed images taken by DART's camera as the cube-shaped "impactor" vehicle, no bigger than a vending machine with two rectangular solar arrays, streaked into the asteroid Dimorphos, about the size of a football stadium, at 7:14 p.m. EDT (2314 GMT) some 6.8 million miles (11 million km) from Earth. The $330 million mission, some seven years in development, was devised to determine if a spacecraft is capable of changing the trajectory of an asteroid through sheer kinetic force, nudging it off course just enough to keep Earth out of harm's way. Whether the experiment succeeded beyond accomplishing its intended impact will not be known until further ground-based telescope observations of the asteroid next month. But NASA officials hailed the immediate outcome of Monday's test, saying the spacecraft achieved its purpose.
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NASA's DART Spacecraft Hits Target Asteroid in First Planetary Defense Test More

NASA's DART Spacecraft Hits Target Asteroid in First Planetary Defense Test

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  • Nuke It (Score:4, Interesting)

    by nukenerd ( 172703 ) on Tuesday September 27, 2022 @05:23AM (#62917265)
    The asteroid's change of course will be determined by the law of conservation of momentum. The effect is limited by the speed and mass of the impacting spacecraft-missile. Surely the speed of the impacting mass would be increased by orders of magnitude if it contained in its centre a nuke that exploded at the moment of impact. Half the debris of the missile would be blown back uselessly, but the other half would hit the asteroid at a speed many times higher than its travelling speed and therfore with much higher momentum.

    If the asteroid broke up that would be even better. The smaller pieces would be put onto random different courses with no more likelihood of hitting Earth than any other debris in the solar system, and would be smaller even if they did.

    • The asteroid's change of course will be determined by the law of conservation of momentum. The effect is limited by the speed and mass of the impacting spacecraft-missile.

      The laws will be obeyed, yes, but if the asteroid's surface is made of loose rocks/dust then they can be blown upwards from the surface and significantly alter the effects of the impact.

      • Re:Nuke It (Score:4, Interesting)

        by burtosis ( 1124179 ) on Tuesday September 27, 2022 @10:02AM (#62917789)
        The gravitational force is so unbelievably low you would be able to pick up house sized boulders with your hands given enough time and ability to grip on. Jumping would exceed escape velocity which is a whopping 0.2 feet per second by my napkin calculation. Anything “blown off” in the conventional sense where it’s faster than watching paint dry isn’t ever going to come back to that asteroid. I would be greatly surprised if the entire spheroid pile of debris wasn’t sloshing around for hours or days before settling back down after impact.
      • So this test only tells us about this astroid.

        • So this test only tells us about this astroid.

          Correct; the test tells us about the effects on this asteroid (and others like it), but other asteroids may be different.

          But one data point is better than none.

        • Fortunately not. Nobody was sure which kind of asteroid it was before we got close-up pictures, but DART's pre-impact photography clearly shows it's a rubble pile asteroid, [science.org] similar to Bennu [wikipedia.org], Itokawa [wikipedia.org] and Ryugu. [wikipedia.org] These are all rubble pile asteroids, and, incidentally, also pretty big ones that orbit very near Earth's orbit, making them of obvious interest for planetary defense. As the landing to sample Bennu showed, we have a lot to learn about these "rubble piles," e.g. the probe that landed on Bennu found th

    • Re: (Score:3)

      by Sique ( 173459 )
      The law of the conservation of momentum still applies. Thus, the center of mass of the asteroid particles will still point the same way than the asteroid before the explosion. You would need to create a very one-sided explosion to actually transfer some momentum to the asteroid. You could for instance bore a hole into the asteroid, and then put the explosive device into the hole, close the hole with some projectile and then ignite it. The projectile then will cause a repulsive force when driven out of the h

      • Re:Nuke It (Score:4, Informative)

        by Entrope ( 68843 ) on Tuesday September 27, 2022 @06:49AM (#62917379) Homepage

        The law of the conservation of momentum still applies. Thus, the center of mass of the asteroid particles will still point the same way than the asteroid before the explosion.

        Your second sentence is only true if no external force is being applied. In the hypothetical, external force -- in the form of a nuclear explosion -- is being applied. Conservation of momentum says that the combined system must follow the same (weighted-)average trajectory, but that would include some bits flying at very high speeds away from the point of the explosion.

        • Re: (Score:2)

          by Sique ( 173459 )
          The problem is that a central explosion adds zero momentum. Instead of a single object heading towards Earth you would have a cloud of objects heading towards Earth, but with the same total mass and the same total impulse. Only if you manage to increase the size of the cloud to dimensions larger than Earth, you at least get a partial miss. Instead, it makes more sense to change the trajectory of the object, and for that, you need either an impact (as DART tested) or an explosion which is not central, like a

          • The idea is to nudge it a tiny fraction of a degree. The longer before impact, the more this adds up over the insane distances to miss the Earth.

          • True but if the central detonation imparts velocity significantly beyond the escape velocity of the impacted object (which will be dynamic as it expands) then you just created a cloud that will presumably be many many times the diameter of the earth by the time it gets here successfully avoiding the impact. It’s not very efficient nor plausible given the masses involved, realistically this is like a fly hitting a semi-trailer window - the semi is going to be unscathed and you better be doing it year

          • Re: (Score:2)

            by Entrope ( 68843 )

            The explosion wouldn't likely be central unless the asteroid is small enough to be disintegrated by the explosion (leaving mostly small fragments). A large asteroid would make it hard to safely burrow to the center.

          • The problem is that a central explosion adds zero momentum.

            Right; you don't want a central explosion (unless you are absolutely sure you can fragment it into pieces too small to worry about, and you can't be sure of that.). You want an off-center explosion, displaced from the center in the direction you want to move away from.

          • ... Instead of a single object heading towards Earth you would have a cloud of objects heading towards Earth, but with the same total mass and the same total impulse. Only if you manage to increase the size of the cloud to dimensions larger than Earth, you at least get a partial miss. ...

            The centre of gravity of the cloud of objects would still be heading towards Earth (but on a slightly deflected axis), but it would be a debris cloud of very large diameter* by the time it reached Earth. Most of it would miss us to join all the other space rocks in the Solar System. The bits that would hit us would be relatively few and small. If there were a very large bit left it would miss us anyway because that was always Plan A (Plan A was the non-disintegration, Plan B the disintegration you are w

      • The law of the conservation of momentum still applies.
        Yes.

        Thus, the center of mass of the asteroid particles will still point the same way than the asteroid before the explosion.
        Nope. You should play some billiard, once at least. Or watch bowling.

    • Re:Nuke It (Score:5, Interesting)

      by splutty ( 43475 ) on Tuesday September 27, 2022 @07:23AM (#62917423)

      And now we have 100's of small radioactive meteorites coming at us instead. Congratulations.

      • Not coming at us. All the debris will have vastly different orbits, so it is unlikely that even a single one of them will hit us. Space is big, and the idea is to hit the asteroid when it's still far away. But even if some of the pieces do hit us, they will just carry a tiny bit of radioactive material, much less that what you'd find if you just dug up some dirt in your garden. Yes, I read somewhere that an average garden contains about a kg of uranium in the top meter of its soil, of course that's a very c

      • Re:Nuke It (Score:5, Funny)

        by cstacy ( 534252 ) on Tuesday September 27, 2022 @10:13AM (#62917813)

        And now we have 100's of small radioactive meteorites coming at us instead. Congratulations.

        Almost all of which will land in Kansas (not too far from the Kent farm).

      • On seeing the impact, Bruce Willis was lost for words. Aphasia sucks!

    • Re: (Score:2)

      by Hentes ( 2461350 )

      The kinetic energy of a nuclear weapon moving at escape velocity is bigger than the energy it could unleash when it detonates. Nuclear weapons don't make much sense simply because impactors are more powerful.

      • The dart space craft is 1,345 lbs and when it impacted it was traveling about 14,000mph giving it roughly 12 billion joules of kinetic energy on impact. The small nuke dropped on Hiroshima was about 12 times more and the largest ones are a million times more than that. So you are wrong by many orders of magnitude when comparing energy. It’s not easy to transfer the energy of a nuclear weapon to the kinetic energy of an object to be deflected which is why detonating a nuke above the surface and abla

        • Re: (Score:2)

          by Hentes ( 2461350 )

          That "small nuke" was also seven times heavier. And I'm not sure where you got the 14,000mph from, the escape velocity of Earth is 11 km/s (25000 mph), and you need to go at least that fast in order to escape the gravitational well and be able to hit anything. Little Boy moving at that speed would have had 266 GJ of kinetic energy.

          • Several times heavier and a difference of 2x speed for 4x more energy still won’t cut it or barely equal. Modern nukes aren’t nearly so weight intensive, no one was saying that, I was using as even a stupid lower bound was beyond in terms of energy. I’m going to just go out on a limb here and suggest you don’t understand orders of magnitude, nor the physics involved.

          • It was also the first ever utilized fission bomb in history with a grossly inefficient warhead (about 1.5 percent.) [howstuffworks.com] That's efficiency of fissile materiel, to say nothing of 1945 technology applied to the rest of the bomb. This is also ignoring that it was a fission, rather than a fusion bomb. With fusion, a small fission bomb is used to generate the temperatures and pressures necessary to initiate fusion in a larger bomb attached to it, resulting in destructive power-per-kilogram greater than fission bombs

        • The dart space craft is 1,345 lbs and when it impacted it was traveling about 14,000mph giving it roughly 12 billion joules of kinetic energy on impact. The small nuke dropped on Hiroshima was about 12 times more and the largest ones are a million times more than that.

          Umm, no. The Hiroshima bomb was around 15,000,000,000,000 joules, or about 1000x the yield of this impactor.

          It should also be noted that we've never set off a bomb that was 1,000,000x as powerful as the Hiroshima bomb. In the range of 10,00

        • Re: (Score:2)

          by ceoyoyo ( 59147 )

          I wasn't aware we'd made multi-teraton nukes. Are you sure you're supposed to be posting that information on Slashdot?

      • They just let anybody post on this site don't they?

    • The asteroid's change of course will be determined by the law of conservation of momentum.

      It's a little more complex than that. The momentum of the impacting spacecraft is transferred to the asteroid, yes, that part is easily calculated. In addition, however, the impact releases a lot of energy, and this energy blows a large amount of material off of the surface of the asteroid. That ejecta produces an equal and opposite reaction. The rocket thrust from this actually effects a larger change of momentum than the spacecraft's impact.

      The effect is limited by the speed and mass of the impacting spacecraft-missile.

      And the nature of the surface.

      Surely the speed of the impacting mass would be increased by orders of magnitude if it contained in its centre a nuke that exploded at the moment of impact.

      The technique here would be to exp

      • By the way, a great video showing stuff blowing off the surface from the ATLAS telescope, here: https://twitter.com/fallingsta... [twitter.com]

      • But better would be to see the asteroid coming with years or decades of advanced warning, when a small nudge instead of a large nuke would be sufficient to deflect it.

        A little bit of simple math tells me that if you can slow the asteroid down by 1 meter/second, one year before potential impact, the point where the asteroid crosses the Earth's orbit will be shifted by 31,556.736 kilometers, almost three times the Earth's diameter.

        • The diameter of the Earth is 12,742km.

          Holy fucking shit is this site just full of dunderheaded intellectual retards now or what!?

          • Holy fucking shit is this site just full of dunderheaded intellectual retards now or what!?

            Unless you're including yourself in that group, you might want to do the math and find out that I'm roughly right.
    • Comment removed based on user account deletion

      • If you don't need nukes, why renegotiate a whole bunch of international treaties nobody wants to renegotiate?

        When I said "Nuke it" I was referring to a real threatening asteroid, not this experiment which I understand was only to test guidance technology. If a big life-extinguishing asteroid were detected heading for Earth, we would be using any best means to stop it, international treaties or not.

      • Dimorphos is about 170m in diameter, or roughly the size of a football stadium. It weighs approximately 5 million tons. DART impacting it is like a bug splattering against a windshield. Normally it would be difficult to even detect the effect it might have on the asteroid's trajectory (its speed is expected to change by roughly 0.002m/s), but this one happens to orbit another asteroid so the scientists hope they will be able to detect a change in its orbital period.

    • The momentum of any surviving missile parts would be utterly inconsequential in comparison to the nuclear explosion itself. The primary way a nuke would be used to move an asteroid is by vaporizing a bunch of rock (and/or possible volatiles within), which expands into space and pushes the asteroid in the opposite direction. It's safest not to shatter the whole thing. You don't want any fragments hitting Earth because even a small fragment will hit like a nuclear bomb - see the Chelyabinsk impact as an examp

    • Nope. The center of mass of all parts would continue on same trajectory as before the blowing up. Many smaller parts hitting the atmosphere would be way worse than one large object of same mass. This idea has been dismissed long time ago.

    • Surely the speed of the impacting mass would be increased by orders of magnitude if it contained in its centre a nuke that exploded at the moment of impact.

      The idea you are pursuing here - finding ways to convert the radiation energy released by a thermonuclear weapon into kinetic energy to generate effects in space - has fortunately already been studied by NASA! It's called the Casaba Howitzer. [wikipedia.org] In effect, it is a nuclear shaped charge that efficiently converts a bomb's radiation energy into kinetic energy, specifically, a blast of tungsten plasma. For obvious reasons it is a popular warhead choice in science fiction.

      Even better, the howitzer's effects can be

  • hypersonic? (Score:2, Insightful)

    by VeryFluffyBunny ( 5037285 )
    Did know they measured velocity in relation to the speed of sound in a vacuum. How many times the speed of sound in a vacuum is hypersonic?

    • Re: (Score:2)

      by splutty ( 43475 )

      That was my first thought when reading the first line as well..

      "Hypersonic" is a completely meaningless term in space, just state a proper speed!

      • Re: (Score:2)

        by Jhon ( 241832 )

        Maybe they meant parsecs? They slammed in to it going "12 parsecs"?

        Was the asteroid named Kessel?

      • Well, not completely meaningless.. From Wiki [wikipedia.org]:

        Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum. But no vacuum is truly perfect, not even in interstellar space, where there are still a few hydrogen atoms per cubic meter.

        In an ideal gas, the speed of sound is proportional to the square root of the temperature. At the space background temperature of 3K, the speed of sound would be about 34m/s. So, 'hypersonic' means something, but it isn't that fast.

        I do long for the day when science writers learn to use standard units like furlongs per fortnight!

    • Re: (Score:1)

      by Entrope ( 68843 )

      Sound doesn't travel in space. How fast is three or five times zero?

      Or... you could not be daft, and infer they were referencing the speed of sound in (something like) Earth's atmosphere at standard temperature and pressure.

      • Re: (Score:2)

        by Jhon ( 241832 )

        "Or... you could not be daft..."

        This is Slashdot. How can the audience *NOT* notice this? It would be 'daft' to assume it "hypersonic" in space would be ignored.

        • Re: (Score:2)

          by Entrope ( 68843 )

          There's an important difference between noticing it and whining about it.

          • Re: (Score:2)

            by Jhon ( 241832 )

            "There's an important difference between noticing it and whining about it."

            Just as there's an important difference between whining about it and ridiculing it. What do you expect nerds to do?

            • Re: (Score:2)

              by Entrope ( 68843 )

              Ideally? Either a mature reaction or ridicule that is actually funny.

              In practice, as demonstrated here? Unfunny and technically inaccurate whinging.

    • Interplanetary space is not a vacuum. Plenty of plasma there. Doubt it was hypersonic compared to that plasma.

      • Re: (Score:2)

        by ceoyoyo ( 59147 )

        It would be pretty impressive if it was. The speed of sound in the interplanetary medium is somewhere between 10 and 100 km/s.

  • Chosen Target was Impressive (Score:5, Interesting)

    by syntap ( 242090 ) on Tuesday September 27, 2022 @06:06AM (#62917303)

    The summary doesn't give the target choice enough credit... this wasn't some random, lonely floating asteroid they picked. The destination was actually an asteroid system, with a much larger asteroid orbited by the target asteroid. They studied the orbital period of the target, so the "before" and "after" orbital periods will definitively tell if there was any difference made. Lots of great tech here, including target-lock on the correct asteroid to hit.

    This was an absolute pleasure to watch, the joy in the room reminded me of the Pathfinder landing.

    As for nukes, the more features you have on a craft you have, the more that can break and fail the mission. It may be neat to re-launch Dart with a nuke at the same asteroid once its new orbital period is established to see what happens. I had just watched Elon Musk on Jay Leno's Garage, where he talked about airplane-like re-usability being the goal... boosters and Starship getting caught, refueled, and relaunched same-day. Perhaps in a couple of decades we could launch multiple "rammer crafts" at an approaching asteroid, with further "corrective rams" quickly launchable.

    • Re: (Score:2)

      by gtall ( 79522 )

      Unless the nuke fails to achieve orbit somehow and falls back to Earth. Then we get nuclear debris from the nuke splattered about. Yum.

      • Unless the nuke fails to achieve orbit somehow and falls back to Earth. Then we get nuclear debris from the nuke splattered about. Yum.

        It's Florida. No great loss except for Florida man.

      • You do know that we've used nuclear material for power sources for some deep space probes for decades, right?

        Like...Voyager, for instance...

        • The Voyagers (and all American RTG-powered spacecraft) use Pu-238, which is non-fissile, and emits alpha particles only in its entire decay chain. And the RTG is built to withstand reentry in Earth's atmosphere. One did reenter as part of the Apollo 13 LEM, and it arrived intact at the bottom of the ocean.

          A bomb is a different proposition, mainly because the bomb material is less benign if it were to be released. We've built bombs that can withstand reentry, but those are made for suborbital reentry at lowe

          • We have already had them burn up in the upper atmosphere [latimes.com], realistically several because of national secrets. Finely and uniformly dispersed about the planet, the atoms are like little prizes in my every breath, bite of food, drink, and home. At this amount it’s not a problem, but it adds up and does not subtract out even when it’s already relatively dilute. Just because it would take a lot more doesn’t justify tolerate letting it burn up, they should be banned from earth orbits at a min
      • You don't arm the nuke until its at escape velocity. If its in a standard warhead, its designed to survive reentry.

      • We've already had something like that happen - Kosmos 954. [wikipedia.org] Total clean-up bill submitted to the Soviet Union by Canada was 6 million dollars - about 42.5 million in today's dollars. That won't even buy you a single F-16 if you include the leather seats and entertainment package. Frankly, as long as Boeing isn't launching the damn thing, I'll take the risk.

    • Well, one would think that NASA had enough practice impacting Mars already.
    • The advantage of nukes is the energy available 1 ton at 10Km/s (typical interplanetary speeds) is 5x10^10 Joules, 1 megaton is 5x10^15 Joues, so you have about 100,000X as muich energy available to deflect the asteroid

      If its a large rock, you can send a series of nukes, spaced ~10,000km apart. First one is detonated at a distance to get spectroscopy of the surfae material, and to a minor course correction. Later nukes are detonated as close as practical to evaporate surface material but not shatter

      • Wish I had mod points for you. It's constantly staggering to me how many people can't grasp this basic orders of magnitude problem.

  • What makes this most believable news of EVER is the fact that there has not been MOON in the sky here at Helsinki for ~3 months. Also to bring slightly frightening side note is that VENUS is at NORTH midnight when it should be WEST.

  • Things not to say to the DART team (Score:4, Funny)

    by ghostlibrary ( 450718 ) on Tuesday September 27, 2022 @08:58AM (#62917609) Homepage Journal
    Things not to say to the DART team: "Sorry your spacecraft crashed", "So, what's the spacecraft going to do next?" and "So this asteroid is moseying along, minding it's own business, and you did WHAT?"

  • NASA's DART spacecraft successfully slammed into a distant asteroid at hypersonic speed

    And what exactly is the speed of sound in a vacuum?

    • I figured they were referring to the popular Sega video game character.
    • I think it's pretty obvious what it's referring to, but I have a different beef - how much of that velocity was imparted orthogonal to the impact trajectory?

      If something is coming straight towards you, the easiest angle to hit it with a projectile is head on, but that won't turn it away from you. You want to hit it on the side to deflect it away from you, which is much different and harder.

      In 3d space where it's two ellipsoid-ish trajectories meeting at a certain time this is not quite so true since me

      • I think it's pretty obvious what it's referring to, but I have a different beef - how much of that velocity was imparted orthogonal to the impact trajectory?
        If something is coming straight towards you, the easiest angle to hit it with a projectile is head on, but that won't turn it away from you.

        Everything in space, including the Earth, is moving.

        If you slow an asteroid with a trajectory centered on the Earth just a little, so that it arrives four minutes later... it will miss the Earth by one Earth radius.

        (Note that this also changes the orbit slightly, lowering the perihelion (*if you hit it against its orbital velocity near aphelion, which is where you'd be most likely to aim). So the impact also diverts sideways, not just delaying the asteroid (in fact, depending on where in the orbit the impac

    • If only there was another term we use for high velocities. You know, one that has to do with the motion of astronomical bodies impacting earth at a high speed. Maybe even having connotations of success and power.

  • Is it really hypersonic speed if it's in space? Where hypersonic is the measure of mach5+, and mach speeds are a measure compared to the density of air, so it's not precise but rather relative, it means it's almost impossible to ever hit any mach speed in space, thus you also cannot hit hypersonic, no?

  • Another video (Score:3)

    by Voice of satan ( 1553177 ) on Tuesday September 27, 2022 @09:59AM (#62917781)

    I guess you have all seen the video of the close up of the probe but this is another one see from outside:

    https://twitter.com/fallingsta... [twitter.com]

    Observed by ATLAS, which is meant to track asteroids.

    https://atlas.fallingstar.com/... [fallingstar.com]

    Yes, there are ATLAS observatories which have nothing to do with Fallout !

  • ...what we did to her son, and she's really pissed at Earth. She was last spotted shouting "Dino's two! dino's two!"

  • And no wildcat oil drillers who put Gatling guns on the Shuttle were needed.

    As someone on faceplant noted, "take that asteroid, that's one for the dinosaurs!"

  • #TheFifthElement #4K #Endscene
    The Fifth Element 4K HDR | Ending scene

    https://www.youtube.com/watch?... [youtube.com]

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