[Server-sky] A kind of thinsat to help deorbiting small debris

[Michael Turner]

My reply on the LinkedIn Thread:

Greg Zsidisin: "Now for reality to intrude - who is gonna pay for
debris removal? That is the eternal question."

It's an answered question, I believe, only if you can identify a
launching state as having produced debris that caused a collision that
actually damaged or destroyed an asset of yours. (Brian Weeden is the
go-to guy on questions like these. I'm only echoing what he's
written.) Without added treaty terms that mandate insurance on
objects, with any added insurable risk to others being billed to the
owner of the new object that imposes the new risks, it's hard to see a
source of any systematic flow of payments.

I took my posting here to the Server Sky mailing list, and Keith
Lofstrom responded with some cogent comments. Basically, as he points
out, it's really more about neutralization more than removal (removal
being just one kind of neutralization.) Neutralization can mean
steering debris to more innocuous orbits - which it looks like LODR
can do. And the debris is really an asset, if we can figure out how to
economically recycle it into useful space purposes. Neutralization
might also take the form of more accurate tracking, for purposes of
avoidance. Again, Keith had some good thoughts on this.

The ideal solution might be a neutralization scheme that feeds on the
debris itself. For example, in the above comment I propose that the
LODR mirrors be distributed in orbit. (This admittedly gets tricky in
terms of scheduling if you're dependent on the intensity of deposited
energy for net thrust vectors -- speed-of-light delays become even
more significant.) What if those mirrorsats could be (partly) made of
debris themselves? They might use their reflected pulses to steer some
of the metallic debris not into the atmosphere but upward, toward
orbital facilities where mirrorsats final assembly is done, so that
the aluminum (and whatnot) can be recycled into mirror backing and
other mirrorsat components. And maybe, eventually, into other useful
things. You have to wonder if LODR couldn't actually help with some
fabrication steps.

Another neutralization technique, as Keith points out, is accurate
tracking of debris for avoidance. Avoidance incurs costs (in terms of
useful lifetime without refueling) on the spacecraft that's evading
the debris. As Keith points out, Server Sky could make an excellent
radar tracker, providing very accurate orbital elements for debris we
can't even see now. If one can make a case that a piece of debris
/could/ hurt or destroy your orbital asset, and that it didn't do harm
only because you dodged it, there's a basis for imposing the costs of
evasion (in terms of lifetime or refueling of your asset) on the
generator of the debris. But that's only IF that source can be
identified. Better tracking might help in this as well: it could
narrow down the possibilities of launching state (or launching
corporate entity.) Reflection from LODR pulses might be also [sic]
produce spectral results that further narrow down the possibilities
for identity. In the future, very trace admixtures in the alloys used
might be required of treaty cosignatories, to provide an identifying
signature that LODR pulses might "read out." In the meantime, it would
be good to develop a registry of materials used in various objects
that currently represent debris risk, through "open source
intelligence" and eventually by treaty mandate.

I should point out that ideas here that I have not attributed to Keith
Lofstrom do not necessarily originate with me. I might be
independently reinventing (or even "remembering" without remembering
where I first saw an idea.) If anyone knows of similar (if not
identical) proposals, I'd be happy to hear about them. LODR itself
dates from the early 90s, if not earlier, with Claude Phipps
apparently at the root of most of [the ideas]. Few ideas about space
technology are entirely new.

Regards,
Michael Turner
Executive Director
Project Persephone
K-1 bldg 3F
7-2-6 Nishishinjuku
Shinjuku-ku Tokyo 160-0023
Tel: +81 (3) 6890-1140
Fax: +81 (3) 6890-1158
Mobile: +81 (90) 5203-8682
turner at projectpersephone.org
http://www.projectpersephone.org/

"Love does not consist in gazing at each other, but in looking outward
together in the same direction." -- Antoine de Saint-Exupéry


On Mon, Nov 18, 2013 at 7:43 PM, Michael Turner
<michael.eugene.turner at gmail.com> wrote:
> On Sun, Nov 17, 2013 at 7:38 PM, Keith Lofstrom <keithl at gate.kl-ic.com> wrote:
>> When people talk about thousands or millions of potential debris
>> objects, I'm not impressed.  The sphere below GEO is 300 billion
>> trillion cubic meters, and almost all of those cubic meters are empty.
>
> Specific /orbital ranges/ are the problem here, though.
>
>> When I walk to the library, I navigate through a few thousand cubic
>> meters of space filled with hundreds of unpredictable potential
>> colliders, mis-operated by idiots yakking on their cell phones,
>> rather than passive objects following Newton's laws to eight decimal
>> places.  Accurately track the debris objects, and space becomes
>> far safer than a crosswalk.
>
> A lot of it is rather small for tracking purposes. Much of it consists
> of tiny pieces chipped off larger pieces. Even paint flakes can cause
> spider cracks and cratering in windows.
>
>>>   http://www.bloomberg.com/news/2013-11-14/real-life-gravity-space-debris-spells-business-for-astrium.html#!
>> ...
>>
>> Check out Star Inc's electrodynamic tether debris collector:
>> http://www.star-tech-inc.com/id121.html
>
> Nice. And I love ED tethers. But are they going send these after every
> 1-cm debris chunk out there?
>
>> Some space advocates talk about extracting resources from the moon.
>> Jerome Pearson points out that there are thousands of tons of high
>> grade aluminum in orbit already - we call it debris because we
>> don't know how to harvest it and re-use it (yet).
>
> Some physical processes are virtually irreversible. I think current
> modeling suggests that if they neutralize the big stuff, the small
> stuff solves itself (or at least the situation stabilizes.) One would
> hope so.
>
>> Much of the unharvested aluminum is in highly eccentric, highly
>> inclined orbits (Delta, GEO, and Molniya upper stages, mostly) and
>> hard to bring to space processing facilities to melt and recast.
>> However, there are two good uses as-is for cylinders of 5mm to 10mm
>> aluminum-lithium tankage:  armor for ISS, and ballast for launch-weight
>> reduced server sky thinsats.
>
> Armor sort of begs the question. Ballast for thinsats sounds a lot
> better. Ideally, there's some solution to the small-debris problem
> where the solution actually /feeds on/ debris. If it helps bootstrap
> Server Sky, one could hardly complain.
>
>> Jerome posits twelve 100 kg EDDE systems to capture all the larger
>> low earth orbit objects in 7 years.  But electrodynamic tethers
>> don't work very well above 2000 km or so.  That is the /lower/
>> practical altitude for light sails.  Light sails won't be effective
>> moving a large rocket body, but they could move small bits of one
>> if we laser cut pieces off of it (hovering a few millimeters away,
>> not from thousands of kilometers, definitely not through a
>> dispersive atmosphere).  One gram chunks would make dandy
>> ballast for ultralight thinsats - less to launch from earth.
>
> You'd want a pretty clean cut. Maybe only lasers can do that.
>
>> But worst case, if we choose to reenter that valuable aluminum,
>> remember that powdered aluminum is the main fuel component of
>> solid fuel rockets.  Rendezvous some oxidizer and the appropriate
>> combustor and nozzle with that aluminum, and it can make its own
>> delta V.  It is far more difficult to deliver that kind of energy
>> from the ground and through an atmosphere, because 99% of the
>> time, any given LEO object is over the horizon from a ground laser.
>> When and if an object appears, it isn't in view for very long.
>
> It'll be back, though.
>
>> Whatever you plan for dealing with an orbital object, you must
>> still find it, very accurately.  Radar sensitivity decreases as
>> the inverse fourth power of distance in vacuum; atmosphere adds
>> more inaccuracies.
>
> Sounds like we need more radar up there. Is that another possible
> thinsat-edge-of-the-wedge? Oh wait: you address this below. How nice.
>
>> ... The reason we don't "just get out of the way"
>> of more space debris is that the tracking error for passive
>> objects in high LEO is one kilometer.  If we knew where the stuff
>> was to 10 meter accuracy, very little delta V would be needed to
>> get out of the way of it, and we could confidently ignore a much
>> larger quantity of objects in the short term.  With high precision
>> tracking and orbit computation, we could also prioritize the
>> likely colliders that need orbit change first.
>>
>> Server sky arrays make dandy illuminators for look-down synthetic
>> aperture radar.  We can find small objects, and characterize their
>> position and velocity to millimeters and to micrometers per second.
>> You can't do that from the ground, or with small aperture, low
>> power, lower frequency orbiting radars.  You also need a lot of
>> computing to correlate and characterize the reflected energy.
>> That is a similar calculation to sorting out uplink from millions
>> of terrestrial internet customers.  Server sky will do radar until
>> the internet business becomes profitable.
>
> OK, then: is it /also/ worth making early thinsats mirror Distributed
> LODR laser pulses for diverting debris onto more innocuous paths until
> it can be recycled?
>
>> We can already do that kind of hyper-accurate tracking of objects
>> if they are designed to be found.  The LAGEOS laser geodesy
>> satellites are tracked accurately enough to measure continental
>> continental drift, with millimeter-per-year velocity accuracy.
>> Most rocket bodies and fragments are NOT designed to be found;
>> that could be fixed by pasting light weight, solar powered, RF
>> fabric on inner and outer surfaces.  In other words, the solar
>> cell and radio portion of thinsats.
>
> Another potential market entry point, if debris tracking information
> can be sold. To the extent that satellites can use station-keeping
> thrust to evade tracked debris, perhaps the information would be
> useful for reducing satellite insurance premia.
>
>> BTW, the LAGEOS satellites the nearest neighbors to the M288
>> orbits, and the only valuable assets we need worry about
>> colliding with.  It's lonely up in the van Allen belt gap.
>>
>> Most "pollution" is valuable material we are too stupid to use.
>> We drilled wells into oil formations for hundreds of years,
>> hoping to find brine for making salt, before Thorla and McKee
>> started selling the gunk that came out of their brine well as
>> medicinal "Seneca Oil" in 1814.
>>
>> We will learn to do the same with space "debris".  The companies
>> that get paid to remove it will profit handsomely from reselling
>> it.  Stake your claims now - the Russians would probably be glad
>> to sell the headache and responsibility for their orbiting
>> derelicts for a little hard currency.
>
> If only there were a way to stake claims. Is there? As things stand,
> they would appear on balance sheets as liabilities, not assets. The
> question is how to turn that around.
>
> Note that LODR doesn't seem to be limited to deorbiting - it can also
> nudge things into higher(-energy) orbits.
>
> Regards,
> Michael Turner
> Executive Director
> Project Persephone
> K-1 bldg 3F
> 7-2-6 Nishishinjuku
> Shinjuku-ku Tokyo 160-0023
> Tel: +81 (3) 6890-1140
> Fax: +81 (3) 6890-1158
> Mobile: +81 (90) 5203-8682
> turner at projectpersephone.org
> http://www.projectpersephone.org/
>
> "Love does not consist in gazing at each other, but in looking outward
> together in the same direction." -- Antoine de Saint-Exupéry