Mopping up Space Junk

I have a few ideas to throw into the global pot for consideration.

After their useful lives, some satellites can deorbit with chemical or
ion rockets or deploy vary large sails to increase their drag
coefficient or be perturbed by the solar wind. Another method could be
to extend long cables to use the Earth’s magnetic field to induce
drag.
However, all these require active systems installed on the junk and be
commanded to deploy.

The only methods for getting rid of space debris is to either go up
there and get it, or wait a very long time for it to decay out or hit
something else and hope that the resulting debris ends up with lower
velocities that will decay quickly and not contribute to the cascade
effect.

Matching an orbit to be able to retrieve something is horrendously
costly in fuel and really not practical except for large or valuable
pieces in really inconvenient orbits.

My idea would be to scale-up Stardust's aerogel capture system and
deploy kilometre-sized megafoams in orbits designed to intersect as
many debris fields as possible. While probably not able to capture
most debris, one or more collisions could reduce their kinetic energy
substantially to aid quicker reentry. Any foam shrapnel produced
should be relatively harmless and decay very quickly. I can't imagine
any process that could create kilometre-scale aerogels on Earth, let
alone in-situ!

A few tons of foaming agents could be shipped up in batches and then
mixed together when the right quantities are reached. Foams would
expand massively in a vacuum if the bubbles in the material could
remain gastight under the extreme stretching. Space would be a very
harsh environment for foam, as they would deform a lot depending on
temperature so some pretty amazing materials would need to be used.

Many shapes are possible - either big amorphous blobs, tentacular
tangles or more structured lattices.
If foams are extruded while being formed they could make long
continuous tentacles.
These could also be used instead of sails as aerobrakes for
deorbiting.
I imagine enormous structures could be made in space with just a few
tons of materials.
They would have to start off in high orbits because their own orbital
decay would be substantial. Maintaining altitude and manoeuverability
would be difficult using rockets, especially after absorbing unknown
amounts of angular kinetic energy from the collisions it is looking
for!

If the foaming material has a high enough albedo or aluminized, they
could provide usable night illumination too.
If we make thousands of them, perhaps they could also reduce
insolation by a useful amount as well.

The foam would have to be environmentally benign for reentry. If it
didn't burn up it would shrink massively with increasing atmospheric
pressure. If enough survives, it might even preserve anything it
caught.

NASA know an awful lot about foam now, anyone from NASA like to
comment on feasibility?

How easy would it be to make foams in a vacuum?

Andy Lee Robinson