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This post makes me wonder about space pollution/saturation. Are there any resources that talk about what is a safe number of satellites for different altitudes

This post makes me wonder about space pollution/saturation. Are there any resources that talk about what is a safe number of satellites for different altitudes and the effects of space pollution? I have heard of the Kessler Syndrome, any suggestions that discuss this? https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome

gravypod 11y ago
As long as the satellites are under a certain mass, they will eventually get too close to Earth and burn up once they are pulled into reentry.
- mino 11y ago
  That doesn't really depend on mass, but on drag and altitude. See for example Figure 10 of: http://www.agi.com/downloads/resources/white-papers/20110808_SmallSat_CubeSat_Orbit_Lifetime_10.pdf http://www.agi.com/downloads/resources/white-papers/20110808...
  - gravypod 11y ago
    Yea, that makes much more sense. I've always wanted to get a group of people together at my college and build a CubeSat but when you say "I want to build a satellite" people think you are crazy. We have the labs, the supplies, and the ability to expense anything we want but no one thinks it is possible.
    - Cshelton 11y ago
      Just do it. You'd be surprised at what money and support may come your way ;) It's very much possible.
      - knappe 11y ago
        I can't encourage this enough. It was one of the most rewarding things I did in college. We launched a cubesat and used it to capture images of the curvature of the Earth and measure the Earth's magnetic field. The work to build the cubesat was tough, but extremely rewarding. Edit: Check out http://www.nasa.gov/offices/education/programs/national/spacegrant/home/Space_Grant_Consortium_Websites.html http://www.nasa.gov/offices/education/programs/national/spac... and see if you can find a local Space Grant program. They'd more than likely be able to either get you the resources or point you in the right direction to get going. We launched ours via a ballon which had the cubesats attached to it. We needed a micro-controller (even easier to find now) a camera and our sensors. All very obtainable. I think the most expensive thing was the magnetometers which ran $80 a pop.
        david-given 11y ago
        While it's still very cool, hanging a sensor off a balloon in the upper atmosphere isn't quite the same thing as launching a satellite into orbit (by about 8 km/s).
throwaway812 11y ago
> Are there any resources that talk about what is a safe number of satellites for different altitudes and the effects of space pollution? Lots. It tracks radius squared, if not cubed. As altitude gets large (which you need for orbit anyway), you can fit a ton of small satellites safely.
clarkmoody 11y ago
The largest class of debris object, by mass, is unspent boosters from launches in the 50s-70s. Lots of old Soviet stuff up there. Kessler Syndrome can be brought under control with as few as five upper stage boosters brought out of orbit per year. Whether the political will exists to spend money to clean up our space mess is another issue entirely.
adamkaz 11y ago
"Space is big. Really big. You just won’t believe how vastly hugely mindbogglingly big it is. I mean you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space." The Hitchhiker’s Guide To The Galaxy, The Hitchhiker’s Guide To The Galaxy
- ceejayoz 11y ago
  Space is big, but low earth orbit isn't as roomy.
  - Klathmon 11y ago
    But isn't it? I mean low earth orbit is at least as much space as we have on the surface, which is already pretty damn big. Yeah, speeds and orbits and stuff change the game a bit, but i can't imagine even a few thousands of satellites cramping a space that large.
    - AnthonyMouse 11y ago
      The problem is we want a lot of things to be in geostationary orbit, which is only possible at a specific altitude. That effectively transforms the "space" from three dimensions to two because the third relative coordinate for all of those things has to be the same. Which is when relative motion becomes a problem. The Empire State Building and the Trump Building are at approximately the same altitude (i.e. sea level) but you don't have to worry about them crashing into each other because their relative position doesn't change. In space everything is in relative motion which effectively costs you another dimension. Then you no longer have "space" you just have "a line" and if two things are at the same point on the line, they eventually crash into each other.
      - zardeh 11y ago
        You also don't have to worry about things in geostationary orbit crashing into each other ;)
xd1936 11y ago
We have a lot of junk in Low Earth Orbit. http://stuffin.space/ http://stuffin.space/
sjburt 11y ago
With the explosion of commercial space in the past 30 years and the end of the Cold War, the space agencies are very concerned about this issue and there is a lot of tracking and cooperation. The regulatory process for launch is quite lengthy, and debris concerns are absolutely addressed industry-wide. Generally as part of the permitting process you have to file an Orbital Debris Assessment Report that contains predictions for orbital lifetime, what will happen to the satellite at EOL, systems for putting the satellite in a safe orbit in case of in-service failure, launch failure etc, risk of collision with other orbital objects and so on. The details differ depending what orbital regime. Things at ISS altitude (~400km) or below will deorbit very quickly (days to months). Terra Bella and other earth observation satellites are typically in slightly altitude, sun-synchronous, near-polar orbits. They will need to carry propellant to drop the vehicle down to a lower orbit when they are taken out of service, otherwise the orbital lifetime will be 5-50 years. Geosynchronous satellites are basically going to be up there forever, so they are placed into a slightly lower (but still extremely high) parking orbit after their useful life ends. This keeps them out of the way of the active satellites, and the orbit there is so large that collisions are unlikely. Finally, the US maintains radar tracking, and will notify operators if a collision is possible so they can make a maneuver. Generally a small adjustment, if performed ahead of time, is sufficient to reduce the probability of collision significantly. The scary things are debris that are too small to track but large enough to cause damage, and situations where non-operational satellites conjuct. Fun fact: if the conjunction probability is high enough, the Air Force will call you in the middle of the night.
Confusion 11y ago
You may be interested in this[1] post by Charles Stross. I think there are a few very insightful comments on there. [1] http://www.antipope.org/charlie/blog-static/2015/09/the-skys-gone-dark.html http://www.antipope.org/charlie/blog-static/2015/09/the-skys...
peterwoo 11y ago
The ESA has a really interesting segment on the space debris problem and possible solutions. https://www.youtube.com/watch?v=tN_CvGJKMOs https://www.youtube.com/watch?v=tN_CvGJKMOs
kang 11y ago
Its frighteningly polluted! http://stuffin.space/ http://stuffin.space/

gravypod 11y ago

As long as the satellites are under a certain mass, they will eventually get too close to Earth and burn up once they are pulled into reentry.

mino 11y ago
That doesn't really depend on mass, but on drag and altitude. See for example Figure 10 of: http://www.agi.com/downloads/resources/white-papers/20110808_SmallSat_CubeSat_Orbit_Lifetime_10.pdf http://www.agi.com/downloads/resources/white-papers/20110808...
- gravypod 11y ago
  Yea, that makes much more sense. I've always wanted to get a group of people together at my college and build a CubeSat but when you say "I want to build a satellite" people think you are crazy. We have the labs, the supplies, and the ability to expense anything we want but no one thinks it is possible.
  - Cshelton 11y ago
    Just do it. You'd be surprised at what money and support may come your way ;) It's very much possible.
    - knappe 11y ago
      I can't encourage this enough. It was one of the most rewarding things I did in college. We launched a cubesat and used it to capture images of the curvature of the Earth and measure the Earth's magnetic field. The work to build the cubesat was tough, but extremely rewarding. Edit: Check out http://www.nasa.gov/offices/education/programs/national/spacegrant/home/Space_Grant_Consortium_Websites.html http://www.nasa.gov/offices/education/programs/national/spac... and see if you can find a local Space Grant program. They'd more than likely be able to either get you the resources or point you in the right direction to get going. We launched ours via a ballon which had the cubesats attached to it. We needed a micro-controller (even easier to find now) a camera and our sensors. All very obtainable. I think the most expensive thing was the magnetometers which ran $80 a pop.
      - david-given 11y ago
        While it's still very cool, hanging a sensor off a balloon in the upper atmosphere isn't quite the same thing as launching a satellite into orbit (by about 8 km/s).

throwaway812 11y ago

> Are there any resources that talk about what is a safe number of satellites for different altitudes and the effects of space pollution? Lots. It tracks radius squared, if not cubed. As altitude gets large (which you need for orbit anyway), you can fit a ton of small satellites safely.

clarkmoody 11y ago

The largest class of debris object, by mass, is unspent boosters from launches in the 50s-70s. Lots of old Soviet stuff up there. Kessler Syndrome can be brought under control with as few as five upper stage boosters brought out of orbit per year. Whether the political will exists to spend money to clean up our space mess is another issue entirely.

adamkaz 11y ago

"Space is big. Really big. You just won’t believe how vastly hugely mindbogglingly big it is. I mean you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space." The Hitchhiker’s Guide To The Galaxy, The Hitchhiker’s Guide To The Galaxy

ceejayoz 11y ago
Space is big, but low earth orbit isn't as roomy.
- Klathmon 11y ago
  But isn't it? I mean low earth orbit is at least as much space as we have on the surface, which is already pretty damn big. Yeah, speeds and orbits and stuff change the game a bit, but i can't imagine even a few thousands of satellites cramping a space that large.
  - AnthonyMouse 11y ago
    The problem is we want a lot of things to be in geostationary orbit, which is only possible at a specific altitude. That effectively transforms the "space" from three dimensions to two because the third relative coordinate for all of those things has to be the same. Which is when relative motion becomes a problem. The Empire State Building and the Trump Building are at approximately the same altitude (i.e. sea level) but you don't have to worry about them crashing into each other because their relative position doesn't change. In space everything is in relative motion which effectively costs you another dimension. Then you no longer have "space" you just have "a line" and if two things are at the same point on the line, they eventually crash into each other.
    - zardeh 11y ago
      You also don't have to worry about things in geostationary orbit crashing into each other ;)

xd1936 11y ago

We have a lot of junk in Low Earth Orbit. http://stuffin.space/ http://stuffin.space/

sjburt 11y ago

With the explosion of commercial space in the past 30 years and the end of the Cold War, the space agencies are very concerned about this issue and there is a lot of tracking and cooperation. The regulatory process for launch is quite lengthy, and debris concerns are absolutely addressed industry-wide. Generally as part of the permitting process you have to file an Orbital Debris Assessment Report that contains predictions for orbital lifetime, what will happen to the satellite at EOL, systems for putting the satellite in a safe orbit in case of in-service failure, launch failure etc, risk of collision with other orbital objects and so on. The details differ depending what orbital regime. Things at ISS altitude (~400km) or below will deorbit very quickly (days to months). Terra Bella and other earth observation satellites are typically in slightly altitude, sun-synchronous, near-polar orbits. They will need to carry propellant to drop the vehicle down to a lower orbit when they are taken out of service, otherwise the orbital lifetime will be 5-50 years. Geosynchronous satellites are basically going to be up there forever, so they are placed into a slightly lower (but still extremely high) parking orbit after their useful life ends. This keeps them out of the way of the active satellites, and the orbit there is so large that collisions are unlikely. Finally, the US maintains radar tracking, and will notify operators if a collision is possible so they can make a maneuver. Generally a small adjustment, if performed ahead of time, is sufficient to reduce the probability of collision significantly. The scary things are debris that are too small to track but large enough to cause damage, and situations where non-operational satellites conjuct. Fun fact: if the conjunction probability is high enough, the Air Force will call you in the middle of the night.

Confusion 11y ago

You may be interested in this[1] post by Charles Stross. I think there are a few very insightful comments on there. [1] http://www.antipope.org/charlie/blog-static/2015/09/the-skys-gone-dark.html http://www.antipope.org/charlie/blog-static/2015/09/the-skys...

peterwoo 11y ago

The ESA has a really interesting segment on the space debris problem and possible solutions. https://www.youtube.com/watch?v=tN_CvGJKMOs https://www.youtube.com/watch?v=tN_CvGJKMOs

kang 11y ago

Its frighteningly polluted! http://stuffin.space/ http://stuffin.space/