The Concern of Space Junk

space junk.jpgThere currently are less than 2,000 operational satellites in orbit. In the next few years, SpaceX and other launch services are going to be deploying tens of thousands of new satellites. What does this portend for the problem of space junk?

The short answer is that it is hard to know for sure.

The good news is that space is big, including even near-earth orbit. There is a lot of room for a lot of satellites. If you think, for example, about the number of boats the oceans can accommodate, and then realize that space is much, much larger, it gives an idea that there is a lot of room to work with. The odds of a collision are low.

All new satellites need to have launch approvals and also decommissioning plans (typically involving falling back into the atmosphere and burning up). SpaceX and OneWeb, for example, have committed to one year deorbiting plans for satellites at end of life.

We’re also pretty good at tracking larger pieces of space junk and identifying potential problems. The International Space Station is periodically moved in order to minimize chances of collision. Around 20,000 man-made objects are currently tracked in space (although they need to be big enough to track — estimates assume many millions of smaller items are also in orbit).

The concerning problem is that one collision can lead to the creation of lots more space junk, which in turn could collide into other satellites. Computer models show that a chain reaction of this sort is possible (the “Kessler Syndrome”). This also isn’t hypothetical: at least five satellite collisions have resulted in increased space debris. Both the International Space Station and the Mir Space Station have sustained damage from collisions with space debris. Space crowding is particular acute at the poles: many satellites maintain polar orbits (in order to have complete coverage of the earth), which means the orbits all cross at the poles.

Some scientists argue we are already in the early stages of the Kessler Syndrome.

So on the issue of space debris, most scientists cautiously believe we are OK if we are prudent. But there are definitely unknowns, and definitely risks.

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