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Drag on ISS
Anybody know why the mean altitude has been decreasing somewhat
rapidly in the past while? http://www.heavens-above.com/issorbitheight.asp Solar activity? Orientation? |
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"Allen Thomson" wrote in message
om... Anybody know why the mean altitude has been decreasing somewhat rapidly in the past while? http://www.heavens-above.com/issorbitheight.asp Solar activity? Orientation? Probably due to the intense geomagnetic storm during Nov 8-10. Ted Molczan |
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(Allen Thomson) wrote in message . com...
Anybody know why the mean altitude has been decreasing somewhat rapidly in the past while? http://www.heavens-above.com/issorbitheight.asp Solar activity? Orientation? Solar activity: http://www.spaceref.com/news/viewsr.html?pid=14469 "After yesterday's dramatic drop in ISS altitude due to an energetic solar particle event with 100MeV protons (measured on the GOES 11 satellite), resulting in a massive spike in geomagnetic activity and in atmospheric drag at orbital altitude, solar activity appears to have leveled off and come down, with reduced orbital decay. The crew was not in any danger. [Yesterday's drop in mean flight altitude reached ~440 m in 24 hrs, as compared to previous ~160 m/day. This morning, the 24-hr. drop was ~200 m. Next week's planned reboost (11/17) will make up for the loss.]" A nice demonstration of just how variable the upper atmosphere is. |
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There is a lower altitude bound (about 300 km or so) after which a
single Progress or Shuttle cannot reboost ISS enough to counteract the increased drag at that altitude. Given that the Russians can't make a lot of Progresses these days, the Shuttles and ATV aren't flying, the reality is that a few weeks of bad solar weather could put the whammy on the whole program. |
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Allen Thomson wrote:
ISS carries a fuel reserve about ten times as large as a Progress delivery. That would let it do a major reboost back to ~400 km altitude even without the Progresses. We know they can transfer fuel from Progress to the station. But in such an event, could they transfer fuel from station to Progress so that they can use the Progress engine instead of the Stations's thrusters ? |
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John Doe wrote:
We know they can transfer fuel from Progress to the station. But in such an event, could they transfer fuel from station to Progress so that they can use the Progress engine instead of the Stations's thrusters ? I believe so. I seem to recall that, if they want to use the Progress's main engines, they need to do a transfer before the burn, but if they use the Progress's smaller attitude control thrusters for the reboost, they can feed fuel straight from the station's tanks during the burn. --Chris |
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John Doe wrote in :
But in such an event, could they transfer fuel from station to Progress so that they can use the Progress engine instead of the Stations's thrusters ? Maybe I'm missing something, but why would they want to? Is there something wrong with the station's thrusters? |
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