From what I gather, the general consensus seems to be that if a satellite collision took place in LEO, then it would probably start a chain reaction, creating a debris cloud that could stop mankind's space travel for a long time.

My question is that whilst this debris cloud will be moving at around eight kilometres a second laterally with respect to the satellite's orbit, how much would the cloud spread vertically?

In other words, am I wrong in thinking that Kessler syndrome will only create a belt of debris? Is the collision sufficient enough to cause a significant deviation of debris from the original orbit of the satellite?

Thank you in advance, and I note that I am probably wrong, I simply want a clarification. :)

  • $\begingroup$ Maybe longitudinally is a better word than vertically here? Or do you mean "altitudinally"? $\endgroup$
    – LocalFluff
    Apr 14, 2015 at 8:14
  • $\begingroup$ "latitudinally" I meant above (damn it, I try to clarify the choice of words but only increase the confusion. But don't worry, it is not I who fail, just my brain) $\endgroup$
    – LocalFluff
    Apr 14, 2015 at 8:22
  • $\begingroup$ Satellites aren't just in a "flat" equatorial orbit - they are also in various inclined orbits. So you wouldn't start with all satellites in a "belt" around the equator. After the first collision occured, there would be a single "cloud" but fragments would collide with intact satellites crossing their path at different inclinations. The result would be the band of fragments would widen as the damage spread... $\endgroup$
    – Andy
    Apr 14, 2015 at 8:26
  • $\begingroup$ @Andy Ah I never thought about the debris affecting orbits in other planes. You've answered my question, thank you :) $\endgroup$ Apr 14, 2015 at 8:47
  • 2
    $\begingroup$ "the general consensus seems to be that if a satellite collision took place in LEO, then it would probably start a chain reaction, creating a debris cloud that could stop mankind's space travel for good." Definitely not. It might be expensive to clean up, and perhaps it could delay space exploration by as much as 25 years, but it would not stop space travel for good. $\endgroup$ Apr 14, 2015 at 11:23

2 Answers 2


First of all, virtually all satellites have elliptical orbits. So if a cloud of debris is created around one of these satellites, then it will intersect with more than just those objects at the provided altitude. Some of the satellites are rather elliptical, and those few satellites would no doubt spread the damage to other planes as well. The most elliptical objects are often those with the most potential for damage, spend boosters.

Secondly, the impact events are very energetic. The most well known satellite collision was the 2009 impact between two satellites. Debris from that event has threatened the ISS. In fact, there's a nice graph that shows the altitude of the various space junk from Wikipedia. It should be noted that this includes all debris, not just the debris from this event, although a significant portion of space debris came from this event. Note that the debris is spread out. This makes sense, as the two objects hit each other at a very high velocity, and thus can change their orbits quite dramatically (Although the point of impact must remain as an altitude to remain, unless some external force (Atmospheric drag, solar radiation, etc) changes it later).

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The bottom line is, a single event seems unlikely to trigger Kessler Syndrome. It does seem quite likely though if the number of objects goes up, we could indeed have such an effect. Satellite collisions are very damaging, and steps should be taken to remove debris if possible, to prevent the problem from getting worse.


Earth (and a LEO orbit) is about 40 million meters around and there are about 30 million seconds per year. So two pieces of debris which move only at walking speed, 1 meter per second, latitudinally relative to each other after a collision or explosion, could be on the opposite sides of Earth within a year. That part seems to be easy, debris from an explosion in LEO don't stay in an orbiting belt. But how bad it is to space flight is another question which I don't know the answer to.


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