With the amount of space debris orbitting the planet, how do satellites and space stations mitigate against impacts?
In: Engineering
Think about how huge the earth is at the surface. Expand that sphere several 10s to 100s of miles. We’re taking about *an insane* amount of area. It’s still a concern, but not a constant danger.
When a potential impact is seen through tracking, satellites and stations can use thrusters to move out of the way
The first line of defense is the vast amount of room there is in space. This means that even though the spacecrafts and debris are both moving at very high speeds they are very unlikely to hit each other. In addition we do have radars on the ground which constantly scan for any debris and will alert the operators of the satellites whenever there is a risk of collision. Most satellites have some remaining fuel intended for station keeping so they can alter their course slightly to avoid the space debris. The issue with this technique is that most of the radar stations were built in the cold war to detect incoming missiles and are therefore no longer being maintained as they used to so we are slowly losing the ability to track space debris.
But it is not uncommon for small pieces of debris to hit spacecrafts. So they have to be designed to handle some impacts. It is possible to build some redundancies into some systems so that the spacecraft will work with some damage. For example solar panels can get holes in them and still operate with just a slightly reduced output. Antennas can similarly get damaged and still work good enough. But for more critical components, especially when humans are the critical component, needs to be armored. There is a number of different techniques used from layers of kevlar to whipple shields to armor plates. So hopefully what you get in an impact is only a small crater.
In addition to all these percussion space stations usually do not technically leave the atmosphere. They orbit the Earth in the upper ionosphere where there is still quite a bit of air. This means that any debris that could potentially hit the space station will get slowed down by the air resistance and will fall down to Earth. So it does not stay in that orbit forever like space debris further up. That gives a lot of protection to the space stations.
For large debris, the ISS and many satellites have collision-avoidance systems on board to adjust the orbit so that it doesn’t hit the debris. They fire a small thruster to increase the projected distance between the craft and the debris at closest approach. This is what Starlink satellites do, for example.
For smaller undetectable debris, they just have to build the outer shell strong enough so that it won’t do any significant damage. The modules of the ISS are covered in specially-designed layers of material that break up the impactor into many small pieces to dissipate the kinetic energy. It’s like being hit by a brick vs being hit by many particles of sand of the same mass.
Keep in mind that despite the large quantity of pieces of debris in orbit, the space around Earth is still very large and relatively empty. So while a piece of high-speed debris can be damaging, it’s less like dodging bullets in a crowded convenience store and more like avoiding an occasional stray bullet in Central Park (while also wearing a bulletproof vest).
“Space debris” is a continuum. The frequency of a piece of debris is directly related to the size of that debris – small particles are significantly more likely than huge chunks of matter. Satellites and space stations are just built with enough external shielding to survive the constant onslaught of tiny particles (mm scale and below).
Larger objects than that are **actively tracked**, and if something is on a collision course with a space station we have enough of an advance warning to move the station out of the way using its onboard thrusters. These happen every so often, maybe once every few years.
Also, there’s not actually as much space debris as you might think. Space is a big, big place. Even down in low-earth orbit, the chance of getting pummeled by space debris is only really a concern for very long-lived projects like the ISS that survive in orbit for many years. And this is the “high risk zone”. Out in the far reaches of geostationary orbit (many times the altitude), space debris is a non-issue. This is where most satellites live, especially communications satellites.
Each satellite has millions of cubic kilometrers, on average, all to itself. Even when you up the numbers to account for debris, the average is still millions or high hundred thousands.
[Here’s](https://www.youtube.com/watch?v=itdYS9XF4a0) a pretty good video about it. Only 16 minutes.
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