Self expanding balls of foam to clean space debris

[Edgard Neuman]

I have an idea to clean space of its debris, but I don't know if its a good one :

I would use some kind of spray bombs as mini satellites, containing self hardening foam that would inflate themselves to become big, low density balls of plastic foam. We could put in orbit a cloud of those mini satellite that would then be able to slow and capture little debris.

It would have to be a very sticky and slimy material, in order to always stay in one piece after violent impacts with debris (but we would need to avoid contact with other functionning satellites).

We also need to insure that the ball of foam doesn't stay long in orbit, and fall on earth with its debris stuck inside, before it becomes too damaged and explodes into new debris.

Edited January 17, 2014 by Edgard Neuman

[Phi for All]

It's an interesting idea. It's hard to engineer it so it doesn't become part of the problem itself. As you mention, it has to avoid contact with functioning satellites.

 

Currently, the biggest problem is that no country wants another country capturing parts of their satellites. They don't want the responsibility of cleaning up their own mess, but they don't want anyone else to clean up their mess and discover their secrets or copy their technology. Nobody wants anyone else to have more power in space than they do, so they mostly avoid dealing with even responsible efforts to clean things up.

[EdEarl]

To get debris to fall from orbit, it is necessary to slow the velocity of that debris. A laser fired from the ISS or another satellite can push a bit on debris and slow its orbit; after which, it will fall to Earth.

 

Expanding foam would merely add mass to the debris already orbiting and make it more dangerous.

[Danijel Gorupec]

I like the idea. I think it can be useful to clean very small debris (maybe 1mm, or smaller) from lower orbits. I hope that even if such very-low-density material breaks into pieces, those pieces would de-orbit much faster than more dense particles because of relatively high drag (in LEO there is some atmosphere).

 

I don't know if you already read about the similar (less ambitious) way they used to collect dust from a comet: startdust. They used aerogel.

[Enthalpy]

Putting a few figures should help to imagine how the attempt looks like.

 

Satellites and debris move at 8km/s on a low Earth orbit - a rifle bullet can have 800m/s; at such speeds, the matter's deformation properties have no importance. Their orbit inclination differ, so no two satellites would have a moderate relative speed. Any material needing a small relative speed to the debris must be in orbit itself, which demands a complicated launcher.

 

Satellites are less strong than a wardrobe, for most of their parts. Any significant shock or deceleration breaks them.

 

De-orbiting a satellite already very low, when acting at one end of the Pacific to target the other end, takes roughly 100m/s. If one wants to avoid creating more debris, the deceleration must be far less than 1g - to be applied very uniformly, because the outer surfaces of a satellite are weak.

 

But even at 1g, it takes 10s to decelerate the little bit that will trigger the re-entry. Within these 10s, the satellite moves by 80km.

 

If the relative speed with some colliding matter is 10km/s, 1g deceleration (probably too much) of a 5t satellite on 5m² surface needs a pressure of 10kPa obtained by a density of only 0.1g/m³.

 

Unless the colliding material is very well targeted, big amounts must be put there. Over 80km length, a D=100m trail takes 63t - to be put very evenly at exactly the right position at exactly the right time despite falling down.

 

Not exactly easy, is it? What can be done presently is render a satellite unfunctional, but this spreads its fragments. Satellites designed accordingly and still controlled can be de-orbited properly by many means, but if poorly designed or out of control, de-orbiting is an unsolved task because it's seriously difficult.