I haven't followed the last part of this thread.
Just a few quick thoughts on a charge based orbital sweeper.

I find it very hard to imagine that the average IMPACT velocity as high as
10 km/s (but NASA SHOULD know what they are saying). Objects in similar
orbits have similar velocities. Two highly elliptical orbits that cross may
have objects going "up" and "down" with a largish delta V. Low earth orbit
(LEO) velocity for a circular orbit is about 5 miles per second ~= 10
km/sec. Two objects in similar orbits will generally have much lower
relative velocities although as noted worst case ones will be as high as
NASA says.

If you can charge objects and keep them charged then you would be able to
perturb their orbits albeit ever so slowly over time using an oppositely
charged object. Results diminish with distance. It may well be possible to
make a diaphonous but physically large "net" many km on a side that attracts
rather small particles that have been charged by whatever other means best
suggests itself. I don't know whether an "ion sprayer" can be made to charge
up incoming taregets. If they are slowed as they pass through the nets mesh
on successive passes, in time the energy difference would allow capture.
While they are too fast to "stick" some of the differential velocity will be
scrubbed off on each pass. Like Arnold "they'll be back" if nothing else
perturbs their orbit.

As particles in elliptical orbits assumedly intersect the sweeper's at
random angle they will impart a random velocity vector as they pass through
its field. On average these will tend to cancel in the up and down
direction - as particles "tug" the mesh up and down they effectively
interact with each other with a time delay. This has the effect of
circularising their orbits into that of the mesh. [Note that up and won
components do not necessarily result in the mesch effectively rising and
falling slightly in orbit in a simple manner. Orbital mechanics can have
some very unintuitive outcomes. (eg To go around the planet more quickly you
must accelerate "backwards". Accelerating "forwards" along the orbit will
make your orbit rise and your orbital period increase ! :-) ) ][Be careful
of the terminology - there's a trap in there].

A major problem would be in maintaining the mesh in orbit in LEO as it's
"ballistic coeffciient" (energy per drag) would be poor. Sweeping up
smallish particles in the sub gram range would be valuable if you could get
enough of them as the larger a praticle is the more easily it can be
detected but, as noted previously, a chip of paint in the wrong place in its
orbit relative to yours can chip windows.

Small "non dsitributed" tethers have a life time measured in days to weeks
in LEO due to being cut by particles or micrometeorites!

Giving an object in LEO large area per mass ensures its early re-entry due
to drag. If your sweeper automatically deorbited itself and its catch in due
course that would be an admirable achievement :-).
Alternatively, a large enough amount of "free" mass of almost any sort in
one place in LEO would be a potentially significant resource.




        RM

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