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When the Kessler syndrome occurs, all transportation will grind to a halt. The Kessler syndrome is when collisions between objects cause a cascade in which eac

When the Kessler syndrome occurs, all transportation will grind to a halt. The Kessler syndrome is when collisions between objects cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome

akiselev 7y ago
GPS satellites are in geosynchronous orbit, far above any threat of Kessler syndrome and we won't have nearly enough material in orbit that occlusion of the satellites would become a problem for centuries, if ever.
- missosoup 7y ago
  If there's ever a hot world war again, all global navigation constellations are going to be destroyed with ASAT missiles in the first hour of it. There's a legitimate concern that over-reliance on GPS will cause massive financial and loss of life damage in the civilian sector if it's ever denied through jamming or kinetic attacks or solar storm etc.
  - jessriedel 7y ago
    This may be true, but note that all the ASAT missle demonstrated to date are only capable of low-Earth orbit, just a couple thousand km from the Earth's surface. The GPS satellites operate at tens of thousands of kilometers higher altitude in medium Earth orbit. https://www.reuters.com/article/us-china-space-report/analysis-points-to-chinas-work-on-new-anti-satellite-weapon-idUSBREA2G1Q320140317 https://www.reuters.com/article/us-china-space-report/analys...
    - missosoup 7y ago
      Demonstrating ASAT against a GEO target would cause a major political incident. The LEO ASAT tests carried out to date caused enough outcry as is. Hitting a GEO target is not difficult. Ignoring dedicated ASAT missiles, any modern IRBM or LRBM can be tasked to intercept a GEO target. Global navigation constellations are certainly going to be one of the first targets in any major hot conflict between world powers. Realistically, a solar storm is a more likely and less predictable threat. The end result is the same, any critical functionality that relies on GPS will be denied for a prolonged period of time.
      - jessriedel 7y ago
        > Hitting a GEO target is not difficult. Ignoring dedicated ASAT missiles, any modern IRBM or LRBM can be tasked to intercept a GEO target. Do you have a cite for this?
        deleted 7y ago
        [deleted]
        missosoup 7y ago
        Not as an overt blanket capability statement, but e.g. LGM-30 is known to carry ASIP and rumoured to carry THAAD kill vehicles, both capable of intercepting dynamic orbital targets. LGM-30 climbs to 100km altitude before deploying the payload bus, which gives it ample range to hit GEO targets anywhere in the hemisphere. Other thing I completely forgot to mention is that all existing global navigation constellations orbit at MEO, not GEO. Which puts them within speculative range of demonstrated ASAT weapons and allows for even longer reach from a launch vehicle like LGM-30. https://www.mda.mil/news/11news0002.html https://www.mda.mil/news/11news0002.html https://www.raytheon.com/capabilities/products/ekv https://www.raytheon.com/capabilities/products/ekv
        jessriedel 7y ago
        > LGM-30 climbs to 100km altitude before deploying the payload bus, which gives it ample range to hit GEO targets anywhere in the hemisphere. This doesn't make sense to me. Could you explain further? LGM-30 is a land-based ICBM designed to strike targets on the surface of the Earth, and hence to take a (just barely) sub-orbital trajectory <13,000 km from point-to-point, with maximum altitude a few hundred km. Wouldn't its thrust capability have to be drastically upgraded to reach 20,000km in altitude, where MEO satellites like GPS are?
        missosoup 7y ago
        It takes about 0.6 tons of fuel to transfer from a 100km to a 20,000km orbit. Well within the payload limits of LGM-30. A derivative of the LGM-30, Minotaur, is used to launch satellites (or ordnance) directly to GTO @ ~30,000km.
- sigstoat 7y ago
  just fyi, they're in medium earth orbit, thousands of kilometers below geosynch. it's why you have to have an up to date almanac, to know which satellites you can see right now, and why cold starts used to take so damn long. (listen for 4 satellites at a time, trying to figure out which ones are there, when you have no idea when or where you are.) (though i agree that kessler concerns are overblown.)
- jessriedel 7y ago
  GPS satellites are indeed at much higher altitudes and thus well protected from (highly speculative) worst-care Kessler syndrome scenarios, which occur in low-Earth orbit (<2,000 km altitude). However, GPS satellites are not in geosynchronous orbit (35,7000 km altitude) but rather operate in a medium Earth orbit of about 20,000 km.
  - tialaramex 7y ago
    Indeed. The GPS birds zip around, a GPS device has to learn (traditionally from GPS itself but downloading from the Internet is much faster if you have Internet and these days most devices can do that) where the birds are in order to turn its relative distance from each satellite into an absolute position on the Earth's surface. If you have an actual GPS app there's typically a diagnostic screen where can see where the satellites are and see them arrive and disappear from your perspective as they orbit.

akiselev 7y ago

GPS satellites are in geosynchronous orbit, far above any threat of Kessler syndrome and we won't have nearly enough material in orbit that occlusion of the satellites would become a problem for centuries, if ever.

missosoup 7y ago
If there's ever a hot world war again, all global navigation constellations are going to be destroyed with ASAT missiles in the first hour of it. There's a legitimate concern that over-reliance on GPS will cause massive financial and loss of life damage in the civilian sector if it's ever denied through jamming or kinetic attacks or solar storm etc.
- jessriedel 7y ago
  This may be true, but note that all the ASAT missle demonstrated to date are only capable of low-Earth orbit, just a couple thousand km from the Earth's surface. The GPS satellites operate at tens of thousands of kilometers higher altitude in medium Earth orbit. https://www.reuters.com/article/us-china-space-report/analysis-points-to-chinas-work-on-new-anti-satellite-weapon-idUSBREA2G1Q320140317 https://www.reuters.com/article/us-china-space-report/analys...
  - missosoup 7y ago
    Demonstrating ASAT against a GEO target would cause a major political incident. The LEO ASAT tests carried out to date caused enough outcry as is. Hitting a GEO target is not difficult. Ignoring dedicated ASAT missiles, any modern IRBM or LRBM can be tasked to intercept a GEO target. Global navigation constellations are certainly going to be one of the first targets in any major hot conflict between world powers. Realistically, a solar storm is a more likely and less predictable threat. The end result is the same, any critical functionality that relies on GPS will be denied for a prolonged period of time.
    - jessriedel 7y ago
      > Hitting a GEO target is not difficult. Ignoring dedicated ASAT missiles, any modern IRBM or LRBM can be tasked to intercept a GEO target. Do you have a cite for this?
      - deleted 7y ago
        [deleted]
      - missosoup 7y ago
        Not as an overt blanket capability statement, but e.g. LGM-30 is known to carry ASIP and rumoured to carry THAAD kill vehicles, both capable of intercepting dynamic orbital targets. LGM-30 climbs to 100km altitude before deploying the payload bus, which gives it ample range to hit GEO targets anywhere in the hemisphere. Other thing I completely forgot to mention is that all existing global navigation constellations orbit at MEO, not GEO. Which puts them within speculative range of demonstrated ASAT weapons and allows for even longer reach from a launch vehicle like LGM-30. https://www.mda.mil/news/11news0002.html https://www.mda.mil/news/11news0002.html https://www.raytheon.com/capabilities/products/ekv https://www.raytheon.com/capabilities/products/ekv
        jessriedel 7y ago
        > LGM-30 climbs to 100km altitude before deploying the payload bus, which gives it ample range to hit GEO targets anywhere in the hemisphere. This doesn't make sense to me. Could you explain further? LGM-30 is a land-based ICBM designed to strike targets on the surface of the Earth, and hence to take a (just barely) sub-orbital trajectory <13,000 km from point-to-point, with maximum altitude a few hundred km. Wouldn't its thrust capability have to be drastically upgraded to reach 20,000km in altitude, where MEO satellites like GPS are?
        missosoup 7y ago
        It takes about 0.6 tons of fuel to transfer from a 100km to a 20,000km orbit. Well within the payload limits of LGM-30. A derivative of the LGM-30, Minotaur, is used to launch satellites (or ordnance) directly to GTO @ ~30,000km.
sigstoat 7y ago
just fyi, they're in medium earth orbit, thousands of kilometers below geosynch. it's why you have to have an up to date almanac, to know which satellites you can see right now, and why cold starts used to take so damn long. (listen for 4 satellites at a time, trying to figure out which ones are there, when you have no idea when or where you are.) (though i agree that kessler concerns are overblown.)
jessriedel 7y ago
GPS satellites are indeed at much higher altitudes and thus well protected from (highly speculative) worst-care Kessler syndrome scenarios, which occur in low-Earth orbit (<2,000 km altitude). However, GPS satellites are not in geosynchronous orbit (35,7000 km altitude) but rather operate in a medium Earth orbit of about 20,000 km.
- tialaramex 7y ago
  Indeed. The GPS birds zip around, a GPS device has to learn (traditionally from GPS itself but downloading from the Internet is much faster if you have Internet and these days most devices can do that) where the birds are in order to turn its relative distance from each satellite into an absolute position on the Earth's surface. If you have an actual GPS app there's typically a diagnostic screen where can see where the satellites are and see them arrive and disappear from your perspective as they orbit.