Hacker News Reader

Comment by b_tterc_p | Hacker News Reader

What’s a bigger concern? Big space debris or small space debris?

The latter. There are more than 170 million objects with dimensions up to 1cm, while the larger ones are less than a million.

Not only that, but they are MUCH harder to track. Tracking systems just aren't good at tracking small things.

1cm objects are currently essentially impossible to track.

So might the risk of harpooning one big thing have a net negative effect by creating more tiny objects?

Yes. It,s nearly impossible to avoid, really. Space debris doesn't really look like a problem that can be solved. It can only be managed.

Other than removed selected really large pieces, such as entire derelict spacecraft, in crowded orbits like GEO where the likelihood of hitting something else is high.

That's what is being assessed with this mission. If creating a few debris with he harpoon allows you to de-orbit the whole debris, which would have generated a certain amount of small debris over time, then it can be a win if the former is smaller than the potential latter.

Also, depending on the orbit considered, the debris generated by the harpoon may be less harmful: they have typically a high surface area/weight ratio so they will deorbit fast if the altitude is low enough, like for this mission.

Wouldn’t it be easier to push objects down towards earth, so the small stuff burns up?

You need to push them in a correct and somewhat precise way so you need to grab the debris somehow before applying the push.

Depends on what you're concerned about and where it is.

Smaller things are more likely to burn up on reentry, whereas bigger things can partially survive.

Atmospheric drag can also vary based on size and density of debris. IIRC smaller things will reenter more quickly. Which is nice, except smaller debris is harder to track (imagine looking for a fleck of paint that's 500 miles away).

However things are a little different in GEO. The good news is that orbital velocities are lower, so if you hit something it'll be less catastrophic than if you hit it at the same angle in LEO. But tracking things is much harder. In LEO you can follow the wrench that some astronaut dropped 10 years ago. But in GEO there's almost no chance. And there's much less atmospheric drag, so junk can stay up there for hundreds of years.

That was my thought too, I wonder how cubesats will also affect the asteroid belt we're building around earth.

They won't have much of an impact, as at the altitude that they operate and for various regulatory reasons, virtually every cubesat will deorbit and burn up in the atmosphere within 25 years of the launch date, with typical times being more on the order of 5-7 years. Should we reach a point where we decide there are too many cubesats and it is becoming problematic, we slow down or stop launches entirely for a few years and the problem resolves itself.

Depends on how you define concern.

For killing a spacecraft? Small debris. For creating more debris? Big debris.

Big space debris is more dangerous because it can start a Kessler cascade.

In addition, small space debris could conceivably be cleaned up with lasers from the ground. That's not so feasible for bigger stuff.

Probably total number of objects.

Reply on news.ycombinator.com