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B Chinese not sure where space station will land

  1. Sep 22, 2016 #1

    wolram

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    The Chinese are not in control of there space station and do not know where it will land.

    Chinese officials are no longer in control of the Tiangong-1 space station. Video provided by Newsy

    They say the rocket motors may not burn up on reentry,

    https://www.sciencedaily.com/videos/9838fa11cf2e851cdf0c28671ecefd8a.htm
     
    Last edited by a moderator: Sep 22, 2016
  2. jcsd
  3. Sep 22, 2016 #2
  4. Sep 24, 2016 #3

    Imager

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    Shades of 1979, can they rename it Skylab II?
     
  5. Sep 24, 2016 #4

    fresh_42

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    Bad idea. Skylab made history by the first time having two nations met in space.
    There is nothing even near that can be said of Tiangong.
     
  6. Jan 8, 2018 #5
    Today (Jan. 8, 2018), China said in the newspaper that they have all satellites under control. In fact, China has been getting these objects from the obit to the Gobi desert as calculated and China has plenty of experience about where to have the orbiting body to be falling. Having the rover soft-landed on the moon surface at the precise location already, and planning to do the same in the far side of the moon, there is no issue for China to control the earth orbit body. China has the world fastest supercomputer that must be helping to do all space program.
     
  7. Jan 8, 2018 #6

    sophiecentaur

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    I was thinking that they were mean, not having it fly over UK. Now, I'm not so sure. :wink:
     
  8. Jan 8, 2018 #7
  9. Jan 9, 2018 #8

    stefan r

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    Tiangong1 did not go to the moon. It does not matter how much computer you have. When you lose communication you lose control.
     
  10. Jan 9, 2018 #9
    A little late to this, but- Skylab was manned by three all American crews in 1973 and 1974. The Apollo–Soyuz Test Project, in July, 1975, was the first meeting of two nations in space.
     
  11. Jan 9, 2018 #10
    Well, they confirmed in the news that they are all under good control. So, where was this new coming from? Just ask Chinese if you want to know.
     
  12. Jan 9, 2018 #11
    Gobi desert then, and if it doesn't behave, then somewhere in the west pacific ocean northeast of Australia.
     
  13. Jan 10, 2018 #12

    mfb

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    Orbital mechanics is something a phone can do today.
    To control where something deorbits, you have to be able to fire the thrusters. Where is a confirmation that this can be done?
    To estimate where something deorbits if you don't have access to thrusters, you have to model the atmosphere, and the largest uncertainties are from imperfect knowledge of the atmospheric conditions.
     
  14. Jan 10, 2018 #13
    Forty years ago we were doing it with an 8-bit processor, clocked at 1.77MHz, with 16k of RAM, with code written in BASIC The biggest problem was obtaining fresh elsets.
     
  15. Jan 10, 2018 #14
  16. Jan 11, 2018 #15

    OmCheeto

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    Good job catching that snapshot image of the re-entry date: May 2nd
    Today, two days later, the date has been changed by a month: April 4th

    2018.01.10.10pm.pst.forec_37820U.jpg
     
  17. Jan 11, 2018 #16

    mfb

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  18. Jan 11, 2018 #17
    Physics Forums copies the file and stores it as a local attachment but other sites keep the external link so refreshing the page updates the forecast image. The reentry dates now seem to range between April and May.
     
  19. Jan 11, 2018 #18

    mfb

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    The prediction will become much more accurate closer to the actual deorbit date - predicting the density of the upper atmosphere months in advance is not really reliable.
     
  20. Jan 11, 2018 #19
  21. Jan 11, 2018 #20
    Since China has such a fast computer maybe they can use it to track the thousands of space debris they intentionally created when they crashed two satellites into each other in 2007. They created the mess, now they can clean it up.
     
  22. Mar 30, 2018 #21

    OmCheeto

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    Getting pretty close!
    According to one site: "Tiangong-1 is currently predicted to reenter the Earth’s atmosphere around April 1st, 2018 14:00 UTC ± 16 hours." [ref]
    Quite a bit of uncertainty.
    From one of their graphs, the space station is losing about 0.44 km in altitude per orbit. Current altitude is about 189 km.
    Orbital period is 88.5 minutes, which means with the uncertainty, it will orbit the earth about 22 times in those 32 hours.

    Northern and southernmost latitudes that have to be worried about debris are 42.8° N & S.

    Another site's infographic shows the debris field being 2000 km long. (Which is about half the width of the USA)
     
  23. Mar 30, 2018 #22

    mfb

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    From the second link:
    First stages never enter orbit, they cannot become space junk even if they are discarded (they typically land in the ocean downrange of the landing site). SpaceX actively deorbits their second stages for missions to low Earth orbits, however - to avoid adding more junk to orbit.

    +- 16 hours starts to get some weak prediction for the longitude-dependence. At +- 6 hours we'll get a wide s-shaped band for the reentry prediction, at +- 4 hours large parts of the map can be ruled out.

    The most recent re-entry prediction is now April 1, 14:00 UTC, or 51 hours from now.
     
  24. Mar 30, 2018 #23
    51 hours +/- 16 hours is a very conservative estimate. I can remember all the cyclones coming down the Coral sea around the time of the Apollo missions when the S-IVB stage 3's were coming down.
     
  25. Mar 30, 2018 #24

    mfb

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    April 1, 16:15 +- 9 hours, 38.5 hours from now. It is getting thinner. Western Turkey is out, northern South America and India to Australia are less likely. Some part in the South Pacific has been ruled out as well but no one cares about that.
     
  26. Mar 30, 2018 #25
    I picked up some chat that the Mediterranean or N Africa region might be likely, but we wait and see
     
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