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Predicting When Space Junk Will Come Home To Earth

Posted by Soulskill on from the not-in-my-back-yard-unfortunately dept.

Following up on recent news of a NASA satellite falling from the sky and a German satellite that did the same, new submitter blais writes "NPR has an interesting interview about space junk falling back to Earth — and the odds of it possibly hitting someone. I thought it might be of interest to the other space nerds out there. Quoting: '... it's very difficult to know exactly when a satellite's going to come down. The Earth's atmosphere is hard to model. It's very thin up there, 100 miles or more up, but it exists. And sometimes it's a little bit denser, sometimes not, and the satellite might be tumbling, and so it makes it very difficult to know exactly when it's ... going to come down."

31 of 43 comments (clear)

  1. Zat's not my department by Mantrid42 · · Score: 2

    Vunce ze rockets are up, who cares vhere zey come down?

    1. Re:Zat's not my department by perpenso · · Score: 3, Informative

      Vunce ze rockets are up, who cares vhere zey come down?

      My understanding of history is that the famous rockets scientists implied by your accent were very much concerned with where the rockets came down.

    2. Re:Zat's not my department by Spy+Handler · · Score: 3, Funny

      WVB: "it vill go up like a cannonball, und come down like a... cannonball, vid a parachute to spare ze life of the speceeman inside"

      LBJ: "Spaceman?"

      WVB: "Spe-ci-men!"

      LBJ: "Well what kind of a spe-ci-men?"

      WVB: "A tough one. Responsive to orders... I had in mind a jimp."

      LBJ: "A Jimp? What in the hell is a jimp??"

      WVB: "Jimp... a jimpanzee, senator!"

    3. Re:Zat's not my department by perpenso · · Score: 2

      You might reconsider who is having the woosh moment. That satirist who penned the original was essentially making the same point as I. :-) Out of context the original intent is easily missed.

    4. Re:Zat's not my department by perpenso · · Score: 2

      And you might want to reconsider as well. Lehrer wrote that when Von Braun was NASA's chief designer. It was a joke about how VB used to do the V2, and now he was working for NASA designing moon rockets.

      Yes, I was aware of all that. :-)

  2. There is a reason... by tyldis · · Score: 1

    There is a reason that the international norm when decommissioning a satellite you put it in an orbit which makes it reenter and disintegrate within 25 years. It's hard to get it to reenter controlled and switch it off at the same time.

    1. Re:There is a reason... by jd · · Score: 2

      Never quite understood the idea of remotely switching a satellite off when de-orbiting it. You'd want to switch off any non-command channel transmitter, sure, as that could interfere with other satellites, but there's no obvious reason to switch off any command channel stuff and this isn't the sort of crash you want to be able to reboot from. Now, I'll throw in one proviso in there - you DO want the computer system switching off once the thermal conditions go out of range, as you don't want a partially-functioning system sending random messages that could mess with the trajectory. But you absolutely want to have the satellite on a controlled descent for as long as possible (ideally via a mix of ground control and on-board computer, since you don't want control lost if the link is lost).

      --
      It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
    2. Re:There is a reason... by tyldis · · Score: 1

      You are required to (a)deplete the fuel tanks and (b)disconnect the batteries.

      I think
      (a) is to reduce the potential damage in case of a collision
      (b) is to stop the satellite from reactivating itself due to solar storms and the like

    3. Re:There is a reason... by dgatwood · · Score: 1

      Only on older satellites that don't need that power/fuel for a controlled deorbit. For most satellites, you'd ideally fire those thrusters at the right time to plant it in the ocean like they did with Mir, Skylab, etc.

      AFAIK, current launch rules (at least in the U.S.) require that a satellite be designed to support a controlled deorbit unless the satellite is small enough to completely burn up on reentry. So eventually, this should cease to be a significant problem. It's just a shame that those rules weren't in place when these birds went up.

      --

      Check out my sci-fi/humor trilogy at PatriotsBooks.

  3. I don't see the problem by jd · · Score: 1

    You run the simulation through a CFD package, compare the prediction with reality, and tweak the parameters for the upper atmosphere accordingly. Keep crashing satellites until you consistently get good results. Problem solved.

    --
    It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
    1. Re:I don't see the problem by Frenzied+Apathy · · Score: 1

      Gee! Hey, that's a great idea!

      How come NASA and the rest of the international space industry didn't think of that!?!?!

      --
      The cake is a lie.
  4. obviously by Hatta · · Score: 4, Insightful

    It's a non-linear dynamic system. Of course it's going to be chaotic.

    --
    Give me Classic Slashdot or give me death!
    1. Re:obviously by poofmeisterp · · Score: 1

      It's a non-linear dynamic system. Of course it's going to be chaotic.

      Chaotic. + or - 1%.

  5. Was anybody ever killed by space junk? by mapkinase · · Score: 4, Informative

    According to NPR, Lottie Williams of Tulsa, Oklahoma, is the only person to have ever actually been hit by space junk. In 1997, she was hit on the shoulder by a piece of what was thought to be the Delta II rocket.

    --
    I do not believe in karma. "Funny"=-6. Do good and forbid evil. Yours, Oft-Offtopic Flamebaiting Troll.
    1. Re:Was anybody ever killed by space junk? by Oswald+McWeany · · Score: 1

      I think some of the rednecks that get probed in UFOs have been "hit" by "space junk".

      --
      "That's the way to do it" - Punch
    2. Re:Was anybody ever killed by space junk? by edxwelch · · Score: 1

      > she was hit on the shoulder by a piece of what was thought to be the Delta II rocket.

      That must have hurt

    3. Re:Was anybody ever killed by space junk? by Deadstick · · Score: 1

      I think it was a leather or fabric material, some kind of strap.

      rj

    4. Re:Was anybody ever killed by space junk? by jzancanaro · · Score: 1

      To Point out the Obvious fact that People are Missing. The SpaceShuttle Columbia Distingrated and Fell over The Southern US and nobody was hit by anything and the only near miss was when one of the Main Engines fell in a lake Missing some fisherman by a Few Hundred yards.

    5. Re:Was anybody ever killed by space junk? by mjr167 · · Score: 1

      Sure... you drop one thing out of the sky without hitting anyone, therefor nothing falling out of the sky will ever hit anyone.

    6. Re:Was anybody ever killed by space junk? by mapkinase · · Score: 1

      Also, it could have been slowed down by trees or structures before hitting the victim.

      --
      I do not believe in karma. "Funny"=-6. Do good and forbid evil. Yours, Oft-Offtopic Flamebaiting Troll.
  6. The problem is weather, solar and atmospheric by perpenso · · Score: 2

    You run the simulation through a CFD package, compare the prediction with reality, and tweak the parameters for the upper atmosphere accordingly. Keep crashing satellites until you consistently get good results. Problem solved.

    There is solar "weather" in space that can affect an orbit. There is weather and turbulence in the upper atmosphere. It is not a static environment where we can refine our parameters for greater accuracy.

    1. Re:The problem is weather, solar and atmospheric by jd · · Score: 2

      The whooshing sound you hear is the incredibly large number of theoretical satellites you'd need to be able to model the upper atmosphere (plus the fact that you can't treat the extreme upper atmosphere as a fluid).

      Yes, the space weather affects things, but we monitor that increasingly. It can be modeled. Not in fine detail, but in aggregate, as indeed can the weather. You may not be able to compute the exact trajectory (you can actually prove you can't, since it's a chaotic system) but you can improve your estimation of the probability of any individual trajectory.

      --
      It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
  7. No one could have predicted by Fr05t · · Score: 1

    No one could have predicted when Duke Nukem Forever would arrive.

  8. Re:I don't understand by scharkalvin · · Score: 1

    Oh like Salvage - One?

  9. There's nothing to worry about by Anonymous Coward · · Score: 1

    With extensive simulation, I've found that there is about a 71% probability any falling object will land in the ocean.

    1. Re:There's nothing to worry about by Anonymous Coward · · Score: 1

      Actually your simulation doesn't account for the trajectories that most sattelites follow...

  10. Re:I don't understand by Anonymous Coward · · Score: 1

    Yes, like that. I think that was a documentary show from the late 1970s, I believe? I wonder what happened? Was there a crash in the price of space gold so the market disappeared? The other documentaries I've seen show how easy it is to get into space, you don't even need special clothes, and there is artificial gravity. Although I'm not sure why you'd go into space to get a few grams of gold if you have the money and resources to build the Enterprise in the first place. But space has its own logic.

  11. Watch out for toilet seats by Quila · · Score: 1

    I can't believe all these posts and no Dead Like Me reference yet.

  12. I am a trained volunteer by Chapter80 · · Score: 1

    When I was much younger, I underwent extensive training in destroying falling near-earth objects. I would love to use that training to secure a high paying job protecting our civilian and military population.

    The training that I received is discussed here, with screen shots.

  13. Re:Design for it by mjr167 · · Score: 2

    I think the problem is that all the space junk is ALREADY in space. There is far more crap orbiting the planet than operational satellites. AGI has a nice plugin for Google Earth that plots all the space junk and it looks like a swarm of bees attacking the planet.

  14. hey, I know that guy! by The+Bad+Astronomer · · Score: 1

    So I'm reading that quotation about modeling the atmosphere, thinking, "That sounds familiar". When I get halfway through I realize, hey! I said that! That's when I finally look at the source and realize it's NPR, the interview I did on Science Friday. That made me LOL.

    --
    *** Phil Plait, aka The Bad Astronomer http://www.badastronomy.com