Life in Earth Orbit

Originally posted 5/19/09
I predict that in the next ten years, much of the space around Earth will be inaccessible to us. With more and more debris in space, the risk of impacts due to space debris increases geometrically. There will be a cascade of collisions which will make low Earth orbit too dangerous to put expensive satellites (or people) into. It will remain inaccessible for hundreds of years or until it is cleaned up.

Today, depending on your definition, there are as few as ten-thousand or as many as one-million things in orbit around the Earth.

In low Earth orbit (LEO) everything must traveling at least 14,000 miles per hour. Impacts can happen at relative speeds of up to 35,000 mph. Visualize two cars hitting each other at a closing speed of 35,000 mph; pieces will fly off in all directions. Most of the new objects created from the collision will not be in sustainable orbits but enough of it will hang around to be a hazard to other objects in space.

If there are 10,000 objects in space, and two of them collide at high speed, there might immediately be 10,500 objects in space. That increases the chance of additional collisions and the number of objects will continue to increase.

This won't be a problem in all orbits. Because of atmospheric drag, nothing lasts for long in very low Earth orbit; so there won't be too much debris there. Of course because of the atmospheric drag it's difficult to keep a useful satellite there for long. Distant orbits and specifically geosynchronous orbits may be available too. There is a whole lot of extra room out that way and objects are generally traveling in similar directions making them less likely to collide.

Space is a tough place to get anything done. We need to do what we can to keep it from getting more difficult. Solutions are hugely expensive, but we need to study them. If cost benefit analysis is being done to examine this issue, I haven't heard it discussed.