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NASA’s Double Asteroid Redirection Test Is a Smashing Success
- ur-whale 4y agoMmmh, differential equations for N-bodies system have notorious tendencies towards chaos and/or easily getting out of chaotic attraction basins. For that reason, I'm not entirely sure that playing cosmic bowling with stuff floating around in the solar system is such a good idea ...
- ohyoutravel 4y agoI suppose the calculus might change when it’s between the earth getting smashed and the potential unintended consequences of cosmic bowling.
- baq 4y ago'bowling' is hardly a good analogy here, though. it's more like pea shooting at huge rocks, though in this case it turned out that the rock in question isn't held together particularly well.
- xvedejas 4y agoWhen the relevant timescales are short, and most of the bodies are small (so, weakly interacting), this is not so big an issue mathematically.
- ghaff 4y agoThat probably assumes that cosmic bowling doesn't happen all the time and that we're disrupting some finely-tuned system that has kept earth (mostly) safe for billions of years.
- QuadmasterXLII 4y agoGoin on the hn-gell-man chart
- ealexhudson 4y agoMore like cosmic pool, and we have Dave Cinzano Bianco Lister.
- JaimeThompson 4y agoLie Mode Who?
- spenczar5 4y agoHi, I work on N-body orbit determination software for asteroid detection and planetary defense (for example, https://github.com/moeyensj/thor https://github.com/moeyensj/thor). Ask me anything. You're right that orbit determination is unstable over long runs, and very sensitive to initial conditions. But the good news is that the solar system is big. Most trajectories do not intersect with the earth's location. So perturbing an orbit that we think has a small chance of hitting us tends to be safe. Also, of course, after deflection, any object is going to be monitored really closely for a long time.
- pageandrew 4y agoSince DART crashed into Dimorphos, changing its orbit around Didymos rather than its orbit around the sun, isn’t there almost no cause for concern because Didymos is still on the same non-intersecting orbit around the sun? Is the concern that Dimorphos’s slightly different orbit could pull Didymos slightly off course in its orbit around the sun, thereby causing it to potentially intersect with Earth at some point in the future, where it wouldn’t have prior to DART. Can we quantify how much Dimorphos’s new orbit has affected Didymos’s orbit? Is that calculable?
- nighthawk454 4y agoHey, this is a bit tangential, but is Barnes-Hut still used in modern n-body simulations? Some of the math has huge crossover with machine learning and dimension reduction, but it’s rarely traced back to the source in literature. Thanks! (I’ll also check out the GitHub repo you linked but I haven’t read it fully yet)
- Hendrikto 4y agoMaybe a bit off topic, but: * What language is that software written in? * What was the hardest problem you had to solve, while working on it?
- spenczar5 4y agoMostly Python and Fortran. See for example https://github.com/oorb/oorb https://github.com/oorb/oorb. The hardest problems are always the social ones. How do you get uptake of a new method, how do you get funding, how do you politely tell a collaboration they are doing the wrong thing, etc. But if you mean pure technical stuff - the hardest problem I had to solve was rethinking some of the inner loops of the THOR algorithm. The problem was essentially to speed up a Hough transform in 6D space. Lots of time spent profiling CPU cache timings to get that fast.
- originalvichy 4y agoGlad to hear. As crazy as it sounds, I believe that the biggest apology we can give to the planet's inhabitants is using our creations to shield Earth from a potentially catastrophic asteroid that could wipe out vast amounts of life. Yes, this "repayment" to Earth's biosphere is dulled by the fact that we created weapons decades ago that could wipe out more life than a relatively small asteroid could, but developing and fine tuning these redirection methods is the least we could do to protect this planet's life.
- r3trohack3r 4y agoOver 75% of life on earth is behind us (4.2bn years). Humanity’s on a track to save life on earth from the complete extinction event coming in 400M to 800m years. Humans are the first (and very likely only) golden ticket our planet has printed to get life off of this rock. We are heading to the stars, and we will bring life with us. Humans are awesome.
- barbazoo 4y agoIt's crazy humans have evolved in less than 0.1% (300k years) of that lower range. Most of our time is still ahead of us.
- Maursault 4y ago> It's crazy humans have evolved in less than 0.1% (300k years) of that lower range. What you mean and what you are suggesting are two different things. Homo sapiens evolved from a similar species less than 300K years ago, not in less than 300K years! It took 62.5M years for humans to evolve from the small mammals that survived the impact that killed the dinosaurs. It was a mere 2.3M years ago when the first humans walked the earth, a species we now call Homo habilis.
- barbazoo 4y agoYou're right, what I meant was that our species, homo sapiens branched off not that long ago, about 300k years. From what we were then to what we are now in an astronomical blink of an eye. And given the exponential growth of development and innovation in the last couple thousand years. And to think we still 400k years to go on earth is just mind boggling.
- sbaiddn 4y agoIn highschool we used an air hockey table to come to the same conclusion: the laws of Newton are valid.
- cj 4y agoI would wager that Isaac Newton would have been hesitant to claim that an asteroid’s trajectory could be modified by humans.
- IshKebab 4y agoProbably not if he knew humans could launch rockets into space.
- hypertele-Xii 4y agoLiterally Newton's Third Law: For every action there is an equal and opposite reaction. This was the guy who figured out exactly that if the asteroid can modify your trajectory, you can modify its.
- sbaiddn 4y agoBecause he ignored the possibilities of rockers, or because he didn't believe his laws are valid in the planetary scale?
- zamadatix 4y agoThe mission was really about two things: 1) Does this design actually function as expected when we go to use it 2) How much deflection actually occurs. The second may sound like something you can answer with Newton but as the article points out: > “The amount of momentum that you put in the target is exactly equal to the momentum that the spacecraft came in with.” But if ejecta flies off the asteroid after impact, physics dictates that the asteroid can get an extra boost, said Cheng. “You end up with a bigger deflection.”... That’s a full 33 minutes shorter than its original orbital period, a finding that implied that a substantial amount of ejecta was produced.
- sbaiddn 4y ago
- curtisblaine 4y agoStab in the dark, but can't this be used as a weapon? Covertly redirect an adequately small asteroid near to the capital city of your enemy, act horrified at the unlucky "natural disaster" that happened, maybe even send help in a gesture of distension...
- zamadatix 4y agoThe technology used here is nowhere near accurate enough to do something like target a specific city (or country) accurately but as a larger concept, sure. You'd have other hurdles to accomplish too though like making sure nobody comes to suspect a specific secret launch you did was at play and that nobody notices the asteroid needs to be deflected after impact.
- moloch-hai 4y agoIt is many orders of magnitude easier to turn a scheduled hit into a miss than the reverse.
- hypertele-Xii 4y agoLiterally the plot of ongoing sci-fi show The Expanse (can recommend).
- webdoodle 4y agoAlso the plot of Starship Troopers, though alien insects launched the meteor, not humans.
- avaldez_ 4y agoI've always thought the meteorite strike was a black flag operation from the Federation to justify war with the bugs because the bug's planet it's at the opposite side of the galaxy and the meteorite wasn't traveling at FTL.
- loeg 4y agoWell, not to spoil it, but not exactly. In the books and show, which are both fantastic, the characters flinging rocks are not other Earth nations; they live in spaceships / space stations / small moons beyond the asteroid belt, for the most part. The asteroid attacks on Earth are indiscriminate, not targeted.
- zamadatix 4y agoGoogle search has a fun easter egg for this mission: https://www.google.com/search?q=Double+Asteroid+Redirection+Test https://www.google.com/search?q=Double+Asteroid+Redirection+... Some love and care was even put into making sure the page looks right when scrolled far enough that it needs to go back to normal.
- quakeguy 4y agoWell, this is just awesome.
- QuadrupleA 4y agoNice :) Gives me a brief bit of nostalgia about how Google used to be.
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- junon 4y agoCute but also super annoying when you want to actually get results. Scrolling far enough on mobile, you can't get the results to stay on the page.
- thro1 4y agoI'm neither sure what the results want (same as designer) - when I woke up lucky to have same dimensions, I had an impression they were to innonsence to adapt in this direction. ( I only wanted to read one more story before going to bed, possibly wonder.. - and it throw me of into.. twisted.. space ? I.. missed what I wanted read.)
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- dtgriscom 4y agoIt took me a while to find it; you have to click the "See results about 'Double Asteroit Redirection Test'" link.
- karaterobot 4y ago> “We needed to understand the Didymos-Dimorphos system before we changed it" As I understand it, one of the big research questions NASA wanted to answer was whether, if they shot the asteroids, the pieces would just fly off to the side of the screen and then wrap around again to the other side.
- pcblues 4y agoI hope this gets the golf-claps it deserves for an As teroids reference :)
- reverseblade2 4y agoPerhaps, human technology is needed in order to prevent a catastrophic asteroid impact. But life, never puts all eggs into a single basket. And that's precisely why we have cockroaches.
- deleted 4y ago[deleted]
- worldsayshi 4y agoAs far as we know Earth is its only basket.
- phkahler 4y agoNo mention of the actual change is speed, only its orbital period around its partner. Also no mention of changes in the orbit of the pair around the sun. It's cool to have both, but the bigger picture is more important even though the effect is certainly less impressive sounding.
- Retric 4y agoThe prediction was Dimorphos would slow between 1.75 cm/s and 2.54 cm/s ~0.05 mph. However, it is easier to measure orbital period vs velocity so we might not have velocity yet.
- nsilvestri 4y agoYou can derive it yourself. Dimorphos's orbital eccentricity is pretty low, meaning you can use: mean_orbital_velocity = 2 * pi * semimajor_axis / period As for the orbit around the sun, the parent body Didymos is about 100x more massive, so any change in the center of mass from this impact will have, in the short term, negligible effects on their orbit around the sun.
- sega_sai 4y agoNo, that is not correct thing to use, as the semimajor axis will change as well. What is needed is the third Kepler law. The semimajor axis will be period^(2/3). And then speed will be period^(-1/3). Thus if period was changed here by roughly 5%, the speed changed by 1.6%
- arlort 4y ago> Also no mention of changes in the orbit of the pair around the sun It would be worrying if there were as that's not what the test was supposed to achieve nor measure
- ch_ase 4y agoI was always wondering how far they knocked it off its original path. As in, if it were on a path to hit Earth and we impacted it at the same distance away, how far would it miss Earth by?
- russdill 4y agoBasically no change in it's orbit around the sun, it's gravitationally bound to a much larger asteroid.
- dtgriscom 4y ago... but the pair's orbit was changed by some amount. How much?
- zamadatix 4y agoEven assuming it wasn't part of a larger system it's hard to give a useful answer for this without a specific orbit and timing. The Δv here was ~2 cm/s which isn't much but what that means in encounter distance depends on the other variables more than it depends on the impact. If you've ever tried to set up encounters or dock in KSP you know what I mean!
- LargeTomato 4y agoThese HN comments are pretty disappointing. So many people clearly did not read the article or have jumped to seemingly silly conclusions.
- themitigating 4y agoI didn't down vote you but could you be more specific? I think many people are speaking in hypotheticals , what if it worked and such
- fuzzythinker 4y agoOther deflection methods: https://en.wikipedia.org/wiki/Asteroid_impact_avoidance https://en.wikipedia.org/wiki/Asteroid_impact_avoidance
- baby 4y agoWhat's the next big threat? Solar flares?
- throw_m239339 4y ago> What's the next big threat? Solar flares? ourselves.
- Vik_Vasylyev-1 4y agoDear colleagues and amateurs, are you sure it was “a Smashing Success»?... Briefings, emotional interviews, impressive photos, PR-type publications - all this can be important for discussions and conclusions in politics, but not in science. Before the appearance of publications in peer-reviewed journals with detailed data and analysis of the collision consequences for Dimorphos`s orbit, there is nothing to discuss seriously and essentially. The following must also be taken into account. One million kilograms of ejected fragments is only less than one percent of the total mass of the target. Since the ejection was "fan-shaped", its effect was most likely extremely insignificant, especially with a completely inelastic reaction for impulse transmission to Dimorphos, which is a loose pile of rubble, stones and dust, but not a monolithic rock. Finally, during photometric and radar observations, nature can played a «cruel joke» with observers who used the mutual eclipses of Didymos and Dimorphos to determine of its orbit changes. The matter is that an asymmetric and optically dense ejection of large asteroid fragments could partially remain in the orbit together with Dimorphos for a long time. With a small value of its first cosmic velocity around of 4 cm/s, this is quite probable and is confirmed by video animation: https://www.youtube.com/watch?v=bfqVqOl9S9w https://www.youtube.com/watch?v=bfqVqOl9S9w. In turn, this could lead to optical-geometric distortions in the measurements of the difference between the moments of mutual eclipses due to the displacement of the photometric center with respect to the center of gravity. Using only different types of eclipses, occurring after 6 hours, lead to distortions of around 30 minutes, which could be interpreted as a real change in orbital period.
- moron4hire 4y ago> Briefings, emotional interviews, impressive photos, PR-type publications - all this can be important for discussions and conclusions in politics, but not in science. What proof do you have?
- Fatnino 4y agoYour video clearly shows a cloud of ejecta leaving the system. I don't see a clump breaking off and staying in orbit.
- Vik_Vasylyev-1 4y ago