Could a Disabled Spy Satellite Pose a Threat to Earth?

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Discussion Overview

The discussion revolves around the potential threat posed by a disabled U.S. spy satellite that has lost power and is expected to re-enter Earth's atmosphere. Participants explore the implications of its uncontrolled descent, the materials it may contain, and the possible responses from government agencies. The conversation touches on historical precedents, the nature of satellite re-entries, and the risks associated with space debris.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants express concern about the satellite's potential to contain hazardous materials, specifically hydrazine, which is toxic and could pose a risk upon re-entry.
  • Others argue that uncontrolled re-entries of satellites are common and typically do not result in harm, citing historical examples like Skylab.
  • A participant questions the logic of shooting down the satellite, suggesting that it would only create more debris rather than mitigate the threat.
  • There is a discussion about the likelihood of different parts of the satellite surviving re-entry, with some suggesting that spherical titanium fuel tanks are more likely to survive than other components.
  • Some participants highlight the unpredictability of where the satellite might land, depending on its orbit, and the challenges in controlling its descent.
  • Concerns are raised about the potential for increased space debris if the satellite is destroyed, which could complicate the operational environment for other satellites.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best course of action regarding the satellite. There are competing views on the implications of its re-entry and the effectiveness of potential responses, with some advocating for destruction and others questioning its efficacy.

Contextual Notes

Participants note that the satellite's orbit and the nature of its materials significantly influence the risks associated with its re-entry. The discussion reflects uncertainty regarding the satellite's trajectory and the effectiveness of proposed mitigation strategies.

  • #61
joema said:
Did you mean $100 million? The expended SM-3 missile cost about $10 million, the overall effort inc'l software, relocation of ships and other assets, etc about $40-$60 million.

The satellite itself probably cost around $1 billion.

No, I meant Billion with a "B." To start with, $1B would hardly cover the overruns on this satellite. If the following report is true, this satellite was part of a $10B program, including $4-5B in overruns.

http://blog.wired.com/defense/2008/02/that-satellite.html

That's the cheap part. Now, let's count the cost of the missile defense program, of which the SM-3 is just a part. That individual $10M missile would not be there if not for the program that brought it into existence, and $100B is probably a lowball estimate.
 
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  • #62
chemisttree said:
I understand that the debris field will pass over Canada first. It should make for an interesting light show for the next couple of days.
I think that was for the first orbit after the intercept. By now it's had time to do many revs, and has probably passed over most of the planet's surface, either on ascent or descent.
 
  • #63
I bet:

they don't hit that tank with the hydrazine

and most of the spy satellite will end up falling on land someplace
 
  • #64
rewebster said:
I bet:

they don't hit that tank with the hydrazine

and most of the spy satellite will end up falling on land someplace
So you think their claims of nothing larger than a football surviving are just plain lies? I guess it wouldn't be the first time, but there are a lot of people with insight into this who could catch them out if they were lying.
 
  • #65
nesp said:
Yes, that's what I meant. Any positive delta-v's imparted would result in higher apogees. Even though the perigee would remain at approximately the original altitude, the apogee would have less atmospheric drag, thus lengthening the debris lifetime -- perhaps significantly so. Sort of an unintentional Hohmann burn. My guess is that some of the pieces may remain in orbit for a year or longer, though those would likely be the smaller pieces that got ejected at higher delta v's.
The missile hit the satellite at an altitude of 130 miles, so the perigee of any chunks sent into a higher orbit will still be 130 miles. 130 miles is quite deep in the atmosphere. Vehicles with circular orbits at 130 miles fall within a day or so. Elliptical orbits take a bit longer, but not years. The Pentagon quotes a max of 40 days for all of the debris to re-enter.
 
  • #66
D H said:
The missile hit the satellite at an altitude of 130 miles, so the perigee of any chunks sent into a higher orbit will still be 130 miles. 130 miles is quite deep in the atmosphere. Vehicles with circular orbits at 130 miles fall within a day or so. Elliptical orbits take a bit longer, but not years. The Pentagon quotes a max of 40 days for all of the debris to re-enter.
No, that's true only for debris ejected with a vertical flight path angle of 90 deg. (i.e. horizontally). Any other angle and perigee will be lower; I think that's the reason for the claims. I believe the imparted delta-v is distributed approximately evenly in direction about the incoming velocity vector.
 
  • #67
I think they should wait until it actually starts entering the atmosphere to shoot at it---it would show a lot better on the news
 
  • #68
belliott4488 said:
No, that's true only for debris ejected with a vertical flight path angle of 90 deg. (i.e. horizontally). Any other angle and perigee will be lower; I think that's the reason for the claims. I believe the imparted delta-v is distributed approximately evenly in direction about the incoming velocity vector.

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.
 
  • #69
CaptainQuasar said:
Oh well. There goes an arms race with China.

Not necessarily, they pay for their weapons development by selling us consumer goods.

We pay for ours by borrowing money from China.:rolleyes:
 
  • #70
nesp said:
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.

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.

Assuming an even distribution of material, there will be very few pieces of debris with a perigee of 130 miles. The overwhelming majority will have lower perigees and higher apogees.
 
  • #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!
 
  • #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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