Could a disabled spy satellite crash into Earth and pose a threat to human life?

In summary, a large US spy satellite has lost power and could hit the Earth in late February or early March, with appropriate government agencies monitoring the situation.
  • #71
Not necessarily, they pay for their weapons development by selling us consumer goods.
We pay for ours by borrowing money from China
We could sell them weapons - that would balance out!
 
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  • #72
I just saw the video on the news of the missile and explosion----didn't they say it was a non-armed missile?-----it didn't look like it
 
  • #73
rewebster said:
I just saw the video on the news of the missile and explosion----didn't they say it was a non-armed missile?-----it didn't look like it
Just shows what a good healthy dose of kinetic energy can do ...
 
  • #74
nesp said:
I agree that's the reason for the claims, but I was referring to those pieces ejected with additional velocity along the parth of the original orbit. There probably are not many such pieces, in comparison with the total, but some will obtain additional velocity for the same reason that someone shooting a bullet at, say, a piece of concrete, will have some concrete fragments fly back into their face. The movie shows what appears to be a pressure sphere exploding, probably the outgassing hydrazine. That pressure will itself impart positive delta v to any pieces in front of it.

DH, I don't have the chart in front of me, but if you find a chart for decay of elliptical orbit debris, you will find that even at 130 mile perigee there are orbits that won't decay for over a year, those with apogees in the hundred of miles. Doesn't take more than a couple of km/s extra to get those apogees.
Yeah ... escape velocity at that altitude is only around 11 - 12 km/sec, so if the impact could deliver 3 km/sec delta-v, you know apogee would be way up there.
 
  • #75
BobG said:
That's correct. The perigee altitude will barely change until the orbit becomes circular. Then the orbit will start to decay.

Any maneuver, including maneuvers performed by the atmosphere, primarily affect the opposite side of the orbit.

Isn't that how atmospheric braking is done?
 
  • #76
nesp said:
Isn't that how atmospheric braking is done?
Atmospheric braking usually refers to re-entry, I believe, not orbits. In any case, though, the general rule of thumb is that removing energy at perigee lowers apogee, thus orbits with low perigee (and therefore increased drag compared to the rest of the orbit) tend to become circularized. Once it's circular, then apogee and perigee are effectively the same, and you can lower perigee by removing energy at apogee (actually, at that point you're doing it everywhere along the orbit, but that's the general rule).
 
  • #77
Aerobraking was first used in the movie 2001, but a recent Mars probe used it as well.
 
  • #78
russ_watters said:
Aerobraking was first used in the movie 2001, but a recent Mars probe used it as well.
No kidding? It was also used in the movie "Dark Star", although in that case the astronut surfed into the upper atmosphere on a chunk of space debris ...

(a special prize to the first person who recognizes that obscure reference!)
 
  • #79
I loved Doolittle trying to convince the bomb not to explode
 
  • #80
Shoulda' known this forum would have people who know that movie!:cool:
 
  • #81
I was very young when I saw it in theaters, but I remember seeing it. I had to buy it when it came out on DVD (2010, too)...
...oh oh...I may actually be getting the two of them confused now. It may have been 2010 (2010 was better). I'll be back in 4 hours...

Anyway: http://mars.jpl.nasa.gov/odyssey/mission/aerobraking.html
It was actually named after the story/movie!
http://en.wikipedia.org/wiki/Aerobraking
 
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