LEO Garbage Collection
Cameron Dorrough
Traffic Around Earth Calls for Stronger Spacecraft; Earlier Warning" and
wondered why there has been no serious proposals for robot garbage
collection in LEO - just lots of talk (and articles like this one) about the
problem.
http://www.space.com/businesstechnology/technology/debris_protection_020710-
1.html
It seems to me that the technology exists now to launch a few small
satellites into LEO with a large folding scoop on the front and a thruster
on the back, to collect some of the rubbish that is drifting around up there
by deliberately running into it. Maybe even one or two Progress-type craft
with the ISS docking gear replaced with a scoop - but many smaller ones
would suffice.
These satellites would fly around on preset orbits until the scoop is full
or they are nearly out of fuel, and then be de-orbited to burn up in the
atmosphere. I realise they can't get everything, but by targetting the
collection of the >10cm objects they know about now, they will collect a lot
of the other stuff as well.
Is there a problem with this scoop idea?? Is the problem simply one of
cost?? The articles never say.. Surely spending the same amount of money
on a few of these satellite garbage collectors as is being spent on research
into better barriers would solve the problem. You can't avoid the debris
for ever...
TIA, Cameron.
Christopher M. Jones
> It seems to me that the technology exists now to launch a few small
> satellites into LEO with a large folding scoop on the front and a thruster
> on the back, to collect some of the rubbish that is drifting around up there
> by deliberately running into it. Maybe even one or two Progress-type craft
> with the ISS docking gear replaced with a scoop - but many smaller ones
> would suffice.
>
> These satellites would fly around on preset orbits until the scoop is full
> or they are nearly out of fuel, and then be de-orbited to burn up in the
> atmosphere. I realise they can't get everything, but by targetting the
> collection of the >10cm objects they know about now, they will collect a lot
> of the other stuff as well.
>
> Is there a problem with this scoop idea?? Is the problem simply one of
> cost?? The articles never say.. Surely spending the same amount of money
> on a few of these satellite garbage collectors as is being spent on research
> into better barriers would solve the problem. You can't avoid the debris
> for ever...
The scoop would be very ineffective. Space is big. Really
big. Really, unbelievably, hugely, bigly big! Do the math,
a region in LEO with a thickness of about 300km will have a
volume 1,000x more than what we would consider as "Earth"
(the region from ground level to the tallest skyscrapers,
including the oceans). More importantly, with a "scoop"
there will be many objects that do not intersect the orbit
often, so it will take essentially forever to get
everything. Also, you wouldn't have a "scoop" like some
big trash can, it would really be a sacrificial, ablative
shield, that would (hopefully) destroy (vaporize) space
junk when it collided with the "scoop". Most of the
space junk that will impact a spacecraft in LEO will be
orbiting in the opposite direction, this material has a
relative speed of ~16km/s, giving it a kinetic energy of
128 kiloJoules per gram (or 0.03 tonne TNT equiv. per kg).
More than enough to vaporize itself and a lot of other
material on impact.
A better idea, in my opinion, would be to hit the debris
with a relatively high power laser (which, if done right,
can deorbit the debris through thrust generated from
vaporization of part of its surface). Also, the debris
in LEO is a lesser concern than that in higher orbits,
since objects in LEO experience a fair bit of drag from
Earth's outer atmosphere, limiting the lifetimes of their
orbits. Objects above about 1,000km altitude will stay
in orbit for a very long time. Unfortunately, the
amount of volume that region represents (trillions of
cubic kilometers) makes physical collection very
impractical.
--
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ois...@yanoo.com
it up, you are transferring yourself to a higher orbit.
Gordon D. Pusch
> Hi All! I was reading the following article in Space.com, titled "Increased
> Traffic Around Earth Calls for Stronger Spacecraft; Earlier Warning" and
> wondered why there has been no serious proposals for robot garbage
> collection in LEO - just lots of talk (and articles like this one) about the
> problem.
>
> http://www.space.com/businesstechnology/technology/debris_protection_020710-
> 1.html
>
> It seems to me that the technology exists now to launch a few small
> satellites into LEO with a large folding scoop on the front and a thruster
> on the back, to collect some of the rubbish that is drifting around up there
> by deliberately running into it. Maybe even one or two Progress-type craft
> with the ISS docking gear replaced with a scoop - but many smaller ones
> would suffice.
>
> These satellites would fly around on preset orbits until the scoop is full
The scoop is never likely to get to get ``full,'' because the vast majority
of what will run into it will be moving at such a high relative velocity
that it will simply punch a hole through any known material. (You are far
more likely to be hit by something in a different orbit than intersects
yours, since something in the same orbit will maintain a constant distance
from you, modulo orbital perturbations.)
> or they are nearly out of fuel, and then be de-orbited to burn up in the
> atmosphere. I realise they can't get everything, but by targetting the
> collection of the >10cm objects they know about now, they will collect a
> lot of the other stuff as well.
If you are talking about _chasing down_ all the >10 cm bits of junk, that
will take more propellant than we can afford to ship up with the ``scoop,''
unless something like an ion drive is used. Changing orbits to rendezvous
with even _one_ other object is =EXPENSIVE= !!!
> Is there a problem with this scoop idea??
1.) Propellant consumption due to all the required obit changes.
2.) Drag.
> Is the problem simply one of cost??
Ultimately, =EVERYTHING= that is not physically impossible boils down to cost.
> Surely spending the same amount of money on a few of these satellite
> garbage collectors as is being spent on research into better barriers
> would solve the problem. You can't avoid the debris for ever...
Currently, it's still cheaper to build sacrificial ``meteor bumpers.''
Such bumpers need not be especially strong or massive --- one or more
relatively thin layers of material spaced off slightly from the main wall
to allow the debris plume to dissipate are quite sufficient to stop the most
common tiny bits of junk. For the big stuff, it's currently cheaper to
change the orbit of the ISS slightly than to send out a ``garbage truck''
to chase down the junk.
I _do_ wonder whether some fairly low-tech options might not be useful,
however --- such as inflating an ``echo'' style balloon ahead of the
station. The most dangerous junk is the stuff that crosses the station's
orbit at a high angle, and relative to the station, this junk will appear
to be approaching from the ``forward'' cone. A balloon with a diameter
comparable to the station's size should be able to intercept the worst
of the incoming junk, yet use fairly little mass. (The obvious problem,
of course, is a significant increase in drag, with a concommit need for
more frequent re-boosts...)
Henry Spencer
Cameron Dorrough <cdor...@spamspamgoawayrmna.com.au> wrote:
>It seems to me that the technology exists now to launch a few small
>satellites into LEO with a large folding scoop on the front and a thruster
>on the back, to collect some of the rubbish that is drifting around up there
Trouble is, this is not like scooping trash up from the street. That
rubbish will typically arrive in the scoop at several times the speed of a
rifle bullet. Collisions at such speeds are not like cars colliding. The
energies involved are more than sufficient to vaporize the materials, and
as a result, collisions become explosions. Typically, in fact, the very
beginning of a collision sends violent shockwaves back through both
objects, shattering them, and the fragment clouds then pass through each
other without interacting much... so you've just made the debris problem
worse rather than better.
The only practical mechanical method of removing the debris is to have
your collector rendezvous with each and every piece. That's impossibly
costly in fuel with current propulsion systems.
--
Socialists always tell us they're going to | Henry Spencer
do better next time. -- Ed Wright | he...@spsystems.net
Designori
"Cameron Dorrough" <cdor...@spamspamgoawayrmna.com.au> wrote in message
news:ai22vp$800$1...@perki.connect.com.au...
would not actually collect the objects. I wonder how much of the
vaporized/fragmented "scoop" would remain in LEO to add to the problem? It's
like nuclear waste down here on Earth; cleaning up 100 tons of it creates
120 tons.
Cameron Dorrough
news:giado7d...@pusch.xnet.com...
>
> Currently, it's still cheaper to build sacrificial ``meteor bumpers.''
> Such bumpers need not be especially strong or massive --- one or more
> relatively thin layers of material spaced off slightly from the main wall
> to allow the debris plume to dissipate are quite sufficient to stop the
most
> common tiny bits of junk. For the big stuff, it's currently cheaper to
> change the orbit of the ISS slightly than to send out a ``garbage truck''
> to chase down the junk.
Ok. Thanks for the answers, all.
> I _do_ wonder whether some fairly low-tech options might not be useful,
> however --- such as inflating an ``echo'' style balloon ahead of the
> station. The most dangerous junk is the stuff that crosses the station's
> orbit at a high angle, and relative to the station, this junk will appear
> to be approaching from the ``forward'' cone. A balloon with a diameter
> comparable to the station's size should be able to intercept the worst
> of the incoming junk, yet use fairly little mass. (The obvious problem,
> of course, is a significant increase in drag, with a concommit need for
> more frequent re-boosts...)
How about a big conical kevlar "umbrella" deployed in the forward cone? -
more to deflect debris than intercept it... I guess the downside is that it
would be in the way of orbital ops a lot of the time (as well as increased
drag).
Cameron Dorrough
news:ruQ19.197261$Wt3.154534@rwcrnsc53...
I was mainly thinking of recovery of some of the known dangerous "ojects"
and their subsequent removal from the database..
You don't think there would be a danger of the laser "pushing" a piece of
debris out of it's known orbit and onto a collision course with something
valuable with little time for avoidance? I suppose that with some (very)
sophisticated target tracking technology and a variable-output steerable
laser it could be done. It would certainly be impressive to seen in action!
:-)
Cameron.
John R. Campbell
>"Cameron Dorrough" <cdor...@spamspamgoawayrmna.com.au> writes:
>I _do_ wonder whether some fairly low-tech options might not be useful,
>however --- such as inflating an ``echo'' style balloon ahead of the
>station. The most dangerous junk is the stuff that crosses the station's
>orbit at a high angle, and relative to the station, this junk will appear
>to be approaching from the ``forward'' cone. A balloon with a diameter
>comparable to the station's size should be able to intercept the worst
>of the incoming junk, yet use fairly little mass. (The obvious problem,
>of course, is a significant increase in drag, with a concommit need for
>more frequent re-boosts...)
I seem to recall a post indicating that a "cloud" of aerogel
would act as an effective "bumper" and collector of the small
crap floating in orbit.
I also seem to recall that a fair amount of damage found after
shuttle flights came from paint flecks but I don't recall any
of the references. It is fortunate that a fragment of an
explosive bolt hasn't crossed paths...
The larger stuff _is_ a problem but at least it can be found.
Of course it also tends to de-orbit, especially during a solar
maximum, so LEO (even at ISS' altitude) tends to be self-
cleaning over a long enough span of time. I would also suspect
that conductive materials also would suffer an additional amount
of braking from the magnetic field, though this may be sheer
fantasy on my part. Since I've no technically specific
background, I can only speculate...
--
John R. Campbell Speaker to Machines so...@jtan.com
- As a SysAdmin, yes, I CAN read your e-mail, but I DON'T get that bored!
Disclaimer: All opinions expressed above are those of John R. Campbell
alone and are seriously unlikely to reflect the opinions of
his employer(s) or lackeys thereof. Anyone who says
differently is itching for a fight!
Peter Hanely
>
>
> I was mainly thinking of recovery of some of the known dangerous "ojects"
> and their subsequent removal from the database..
>
> You don't think there would be a danger of the laser "pushing" a piece of
> debris out of it's known orbit and onto a collision course with something
> valuable with little time for avoidance? I suppose that with some (very)
> sophisticated target tracking technology and a variable-output steerable
> laser it could be done. It would certainly be impressive to seen in action!
> :-)
>
> Cameron.
>
volume (definately non trivial) surrounding your spacecraft and you'd have
a working shield against debree aproaching at high speeds.
F = I*l x B = Q*V x B
E = n * l * B x V : n = 1
V (set)= 8*10^3
l (set)= 1m
E(destructive) (set)= 24*10^6 V
B >= 3*10^3 Tesla
Garbage would be burned as it crossed the field. Sub destructive fields
might deflect debree, possably out of orbit, or slow it to where it
could be collected.
Spambot trap:
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ab...@msn.com ab...@sprint.com ab...@earthlink.com u...@ftc.gov
wall...@kmsi.net
...
>The only practical mechanical method of removing the debris is to have
>your collector rendezvous with each and every piece. That's impossibly
>costly in fuel with current propulsion systems.
It's seemed to me for some time that it would be useful to have robotic
"waldo satellites" or RPVs sitting in orbit, running on ion or Hall Effect
thrusters and solar power. They could be used for miscellaneous simple
repairs, up close views of damaged satellites, possibly towing things to
different orbits, etc.
Sure, they'd be slow, but what the hey, it'd be faster and way cheaper than
sending up a space shuttle crew or abandoning expensive equipment.
And when they're not doing that, they could collect garbage -- one piece at
a time. Big stuff first, filling station for reaction mass... If they were
small enough and cheap enough, I wonder how many it would take.
/kenw
Ken Wallewein
Calgary, Alberta
ke...@kmsi.net
www.kmsi.net
Gordon D. Pusch
> "Gordon D. Pusch" <gdp...@NO.xnet.SPAM.com> wrote in message
> news:giado7d...@pusch.xnet.com...
[...]
>> I _do_ wonder whether some fairly low-tech options might not be useful,
>> however --- such as inflating an ``echo'' style balloon ahead of the
>> station. The most dangerous junk is the stuff that crosses the station's
>> orbit at a high angle, and relative to the station, this junk will appear
>> to be approaching from the ``forward'' cone. A balloon with a diameter
>> comparable to the station's size should be able to intercept the worst
>> of the incoming junk, yet use fairly little mass. (The obvious problem,
>> of course, is a significant increase in drag, with a concommit need for
>> more frequent re-boosts...)
>
> How about a big conical kevlar "umbrella" deployed in the forward cone? -
> more to deflect debris than intercept it...
You're not getting it, yet: =NO= material is strong enough to stop, or even
``deflect'' the debris! Impact with a bit of orbital debris equals a gout
of superheated plasma, and a vaporized hole in the shield --- =PERIOD=.
=NO= material made of ordinary atoms has chemical bonds strong enough
to hold together when hit by that much kinetic energy density !!!
> I guess the downside is that it would be in the way of orbital ops a lot
> of the time
Not really --- viewed from the ISS, the shuttle kind of ``slides in''
sideways from the aft direction. But the ``umbrella'' will get blown
around a bit when the jets from the RCS thrusters impinge on it...
> (as well as increased drag).
Drag is the killer.
-- Gordon D. Pusch
perl -e '$_ = "gdpusch\@NO.xnet.SPAM.com\n"; s/NO\.//; s/SPAM\.//; print;'
Jordin Kare
> "Cameron Dorrough" <cdor...@spamspamgoawayrmna.com.au> wrot:
> > It seems to me that the technology exists now to launch a few small
> > satellites into LEO with a large folding scoop on the front and a thruster
> > on the back, to collect some of the rubbish that is drifting around up there
> > by deliberately running into it. ...
>
>
> A better idea, in my opinion, would be to hit the debris
> with a relatively high power laser (which, if done right,
> can deorbit the debris through thrust generated from
> vaporization of part of its surface).
It's been looked at several times. The main recent study was the Orion
concept (no, not *that* Orion) proposed by Claude Phipps (formerly of
Los Alamos, now Photonics Associates).
--
Jordin Kare
"Don't count your photons before they're emitted"
Mike Speegle
news:3D493B6E...@nospam.calweb.com...
> Figure a way to create a multi kT (kilo-Tesla) magnetic field over
a large
> volume (definately non trivial) surrounding your spacecraft and
you'd have
> a working shield against debree aproaching at high speeds.
And what about materials not affected by a magnetic field?
--
Mike
________________________________________________________
"Colorado Ski Country, USA" Come often. Ski hard.
Spend *lots* of money. Then leave as quickly as you can.
Richard Treitel
>The only practical mechanical method of removing the debris is to have
>your collector rendezvous with each and every piece. That's impossibly
>costly in fuel with current propulsion systems.
So I have this hare-brained idea: instead of RV'ing with each piece of
debris, puff out a small amount of gas as it goes past, enough to slow
it down appreciably, so that its perigee dips into the atmosphere.
This obviously won't work very well for anything large. And for really
small (pinhead-sized) debris it would probably be a waste of gas. What
about medium-sized pieces?
-- Richard
------
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Keith F. Lynch
> Typically, in fact, the very beginning of a collision sends violent
> shockwaves back through both objects, shattering them, and the
> fragment clouds then pass through each other without interacting
> much... so you've just made the debris problem worse rather than
> better.
What if one of the objects isn't in orbit, but is moving straight up,
or better yet straight down. And has already fragmented into billions
of sand-grain sized pieces.
Or perhaps it shoots out a downards-thrusting jet of air or other gas,
as it passes the offending object.
ANY delta V applied to something in low earth orbit, other than a
push directly forwards in orbit, is likely to cause its new orbit
to intersect the atmosphere within minutes.
And launching interceptors that only have to reach orbital altitude,
should be much easier than if they also have to reach orbital velocity.
--
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Cameron Dorrough
> "Cameron Dorrough" <cdor...@spamspamgoawayrmna.com.au> writes:
>
> > "Gordon D. Pusch" <gdp...@NO.xnet.SPAM.com> wrote in message
> > news:giado7d...@pusch.xnet.com...
> [...]
> >> I _do_ wonder whether some fairly low-tech options might not be useful,
> >> however --- such as inflating an ``echo'' style balloon ahead of the
> >> station. The most dangerous junk is the stuff that crosses the
station's
> >> orbit at a high angle, and relative to the station, this junk will
appear
> >> to be approaching from the ``forward'' cone. A balloon with a diameter
> >> comparable to the station's size should be able to intercept the worst
> >> of the incoming junk, yet use fairly little mass. (The obvious problem,
> >> of course, is a significant increase in drag, with a concommit need for
> >> more frequent re-boosts...)
> >
> > How about a big conical kevlar "umbrella" deployed in the forward
cone? -
> > more to deflect debris than intercept it...
>
> You're not getting it, yet: =NO= material is strong enough to stop, or
even
> ``deflect'' the debris! Impact with a bit of orbital debris equals a gout
> of superheated plasma, and a vaporized hole in the shield --- =PERIOD=.
> =NO= material made of ordinary atoms has chemical bonds strong enough
> to hold together when hit by that much kinetic energy density !!!
Hokay... so we need to go with layers and break the pieces down - kind of a
portable extra-thick Whipple shield.
How about a cluster of three small ion-thruster-equipped "satellites" flying
in close proximity (within metres), holding the edges of a large flexible
conical "bag" made of double or triple the thickness of normal hull
protection fabric with a "target" of rock (a meteroid?), iron or other
really thick/dense material in the exact center??
You'd still have to be careful what sized particles you picked on, but
presumably you could stop/vaporize paint flakes, etc. Anything too large
hitting the "bag" *might* be deflected slightly inwards (leaving a nasty
gouge) before colliding with the chunk of rock in the center and exploding
into smaller fragments to be collected by the surrounding "bag"... or blast
straight through to be collected next time (maybe!) and the more junk you
collect, the more rubbish you have in the bag for the next flake to run
into..
Of course if you hit something the same mass as the "target" it's game over,
but it has to be better than letting the same sized bits hit something
valuable.. no? ;-)
Cameron:-)
Bill Bogen
> Traffic Around Earth Calls for Stronger Spacecraft; Earlier Warning" and
> wondered why there has been no serious proposals for robot garbage
> collection in LEO - just lots of talk (and articles like this one) about the
> problem.
I seem to remember an article by Peter Kokh in 'The Moon Miner's
Manifesto' that proposed a standard for launchers to reduce the
creation of space junk in the first place. The standard included
simple things like not painting the vehicles (reduce paint chips).
Also, I believe Bob Forward has formed a company promoting a tether
package that launchers could include on their satellites so that, when
the satellite had consumed all its station-keeping fuel or otherwise
passed its useful lifetime, it would deploy the tether which would use
electrodynamics to create a drag on the satellite, causing it to
de-orbit.
It's in the interest of every nation or company that launches to clean
up after itself.
Gordon D. Pusch
> To my surprise and delight, he...@spsystems.net (Henry Spencer) wrote:
>
> >The only practical mechanical method of removing the debris is to have
> >your collector rendezvous with each and every piece. That's impossibly
> >costly in fuel with current propulsion systems.
>
> So I have this hare-brained idea: instead of RV'ing with each piece of
> debris, puff out a small amount of gas as it goes past, enough to slow
> it down appreciably, so that its perigee dips into the atmosphere.
It doesn't ``go past'' at any significant velocity unless it's in an orbit
that nearly intersects yours, but at a significant relative inclination.
The most effective debris-clearing orbits will be retrograde ones, which
unfortunately are hideously expensive to get into...
> This obviously won't work very well for anything large. And for really
> small (pinhead-sized) debris it would probably be a waste of gas. What
> about medium-sized pieces?
It's going to be a waste of gas at =ANY= debris size, unless the gas is
contained in a balloon as I proposed earlier...
Gordon D. Pusch
> Henry Spencer <he...@spsystems.net> wrote:
>> Typically, in fact, the very beginning of a collision sends violent
>> shockwaves back through both objects, shattering them, and the
>> fragment clouds then pass through each other without interacting
>> much... so you've just made the debris problem worse rather than
>> better.
>
> What if one of the objects isn't in orbit, but is moving straight up,
> or better yet straight down.
You still get shockwaves that shatter the debris into smaller pieces,
some of which will still have orbital-magnitude velocities.
> And has already fragmented into billions of sand-grain sized pieces.
Can you say ``victims of `friendly fire' '' ???
> Or perhaps it shoots out a downards-thrusting jet of air or other gas,
> as it passes the offending object.
Space is BIG. Very, very BIG. In fact, space is so mind-bogglingly HUGE
that attempting to clear out an orbit a few square meters at a time
as you propose is quite pointless --- before you will make a dent it
this way, the debris will have de-orbited on its own from atmospheric drag.
> ANY delta V applied to something in low earth orbit, other than a
> push directly forwards in orbit, is likely to cause its new orbit
> to intersect the atmosphere within minutes.
I suggest that you write down some order-of-magnitude numbers onto the
back of your envelope RE: the velocities invlved, and then re-think
your position.
> And launching interceptors that only have to reach orbital altitude,
> should be much easier than if they also have to reach orbital velocity.
I suggest that you write down some order-of-magnitude numbers onto the
back of your envelope RE: the number of interceptors required, and then
re-think your position.
Brian Gaff
till it becomes a problem and either hits operators in their pockets, or
someone dies, then hastily devise some way to clear away the junk we send up
there.
I'd have thought there ought to be some international agreement that makes
the people who design launch vehicles and sts, responsible for what happens
to them after use.
Sooner or later something will need to be done. I can see those folk
awaiting pictures from their probe to our solar system marvelling at the
rings of Earth, and wondering what they are....:-)
Brian
--
Brian Gaff - Sorry, can't see pictures, graphics are great, but the blind
can't hear them
bri...@blueyonder.co.uk
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John Schilling
>In article <3D500A37...@sys.uea.ac.uk>, <m...@sys.uea.ac.uk> wrote:
>>That idea's seen several proposals. Usually what's proposed is
>>an inspection/repair satellite sitting in GEO and designed
>>to service faulty communication satellites. The idea has
>>never got anywhere, perhaps because of doubts over it's
>>usefulness.
>There are three interlocking problems which cause that.
>First, the satellite-servicing people tend to have grossly inflated ideas
>about how much satellite design will change to suit the limitations of
>their robots. Building a servicer robot which is about as versatile as a
>spacesuited astronaut would improve the situation greatly, but it's hard,
>and simpler servicers are of very limited use with current satellite designs.
The servicer that may actually be cost-effective for current satellite
designs, at the low end of the scale, is a simple camera-bot. Does
nothing but sit clamped to some passive docking adaptor on the host
99.9% of the time, and flit around taking pictures the remaining 0.1%
But those pictures can be of serious value to anyone trying to diagnose
on-orbit failures, can make the difference between implementing the right
fix and the wrong fix.
You do need to modify the existing satellite design somwehat - a cheap
camera-bot can't do stationkeeping for years, so it does need that passive
docking adaptor on the host. And of course you have to build the bot.
But that's megabucks, not gigabucks.
>Second, the comsat people are deeply conservative and are *not* going to
>make their plans around a nonexistent servicing facility. This means that
>a servicing system needs to spend most of its money before it gets any
>commitments from customers, and that makes financing a lot harder.
Another point in the camera-bot's favor, you don't need to plan for it
to derive value from it.
>Finally, actual comsat operating costs are closely-held information, to
>put it mildly, so it's difficult to make any sort of solid assessment of
>what such a thing could be worth to operators. This adds a further hefty
>dose of market uncertainty.
For that matter, the operating *procedures* are secrets, which makes
offering support services even harder.
--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
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*schi...@spock.usc.edu * for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *
John R. Campbell
>I'd have thought there ought to be some international agreement that makes
>the people who design launch vehicles and sts, responsible for what happens
>to them after use.
The treaty only covers damage caused by re-entry of an object.
Of course, I wonder if there's anything *entry* of finished goods
from a mined/processed asteroid since it never _left_ the earth's
atmosphere (so it can hardly be a *re*entry now, could it?)...
I think the "cloud" of an aerogel may work best over time once
the tech/launch capability is up to it; The only problem comes
from the debris injected into orbit with 'em (we're not talking
the use of just *one* sponge here).
Sheesh- My mind's in the gutter again. I've had to suppress
3 different tangents for overdone obscure sexual references...
Here's one, from a 1979 Omni write in of 21st Century Brand
Names:
Apollo Capsules - The Contraceptive that makes each
re-entry as safe as the first!
Sorry, I couldn't resist injecting levity. *SIGH*
William Mook
consequence. A better approach is to use a very large Earth based
laser in conjunction with US space command data - to fire at orbiting
debris. Not to destroy it, but to impart controlled changes in
velocity in their orbits. These changes would bring the debris back
to Earth quickly. A small debris element for example, would be struck
on the leading edge by a laser burst. This would cause a small plasma
ball to erupt on the leading edge of the debris. This would slow the
debris. Its new orbit would be confirmed, and the process repeated,
until the debris was low enough to be slowed by air resistance and
fell out of orbit.
A 100 MWatt laser combined with a moderately sized telescope equipped
with adaptive optics, operating as a beam steering device - would
suffice. The whole program may cost $1 billion to set up, and $200
million a year to operate - depending on the nature of the laser (I'm
assuming a CO2 laser - but others are possible).
m...@sys.uea.ac.uk
John Schilling wrote:
>
> The servicer that may actually be cost-effective for current satellite
> designs, at the low end of the scale, is a simple camera-bot. Does
> nothing but sit clamped to some passive docking adaptor on the host
> 99.9% of the time, and flit around taking pictures the remaining 0.1%
>
> But those pictures can be of serious value to anyone trying to diagnose
> on-orbit failures, can make the difference between implementing the right
> fix and the wrong fix.
>
> You do need to modify the existing satellite design somwehat - a cheap
> camera-bot can't do stationkeeping for years, so it does need that passive
> docking adaptor on the host. And of course you have to build the bot.
> But that's megabucks, not gigabucks.
You do have to convince the satellite operators the bot which hopefully
won't be needed is worth sacrificing several months of station keeping
propellant.
A camerabot might be dooably if launched separately. AFIK, getting
from point to point in GEO is quite cheap so one could imagine a
bot able to make 4 or 5 rendezvous'.
To work financially, I you'd have to pitch it along the lines
of... "pay me $N per year and I'll image your satellite for free
if you have a problem". This way you get a steady cash flow and a
predictable return on your investment. Keep the thing small so it
can be launched on the Ariane secondary payload platform and I think
you're in business.
--
>==============================================================<
Michael Morton | Need a job!
School of Information | (pretty please)
Systems, University | http://www.sys.uea.ac.uk/~mtm/work
of East Anglia, Norwich |
>==============================================================<
Cameron Dorrough
news:5d3d12e8.02081...@posting.google.com...
And just what, praytell, would a 100MW laser do to the atmosphere, ozone
layer, local meteorology (thinking electrical storms), birds and anything
else in it's path before getting to the target? Operating a large microwave
dish is restrictive enough. I suppose the operators would factor this in as
"acceptable path loss" ?
Though you could always name the project "Star Wars", use it against
incoming missiles and get congressional funding.. ;-)
At least if the thing is installed on a GEO satellite, you 1) don't need it
to be as powerful, 2) solar electricity is relatively plentiful and 3) can
mount it on a steerable turret - making (slightly) less of a security risk.
Cameron:-)
John R. Campbell
>
>To work financially, I you'd have to pitch it along the lines
>of... "pay me $N per year and I'll image your satellite for free
>if you have a problem". This way you get a steady cash flow and a
>predictable return on your investment. Keep the thing small so it
>can be launched on the Ariane secondary payload platform and I think
>you're in business.
Somehow the HMO mechanism doesn't work for human beings and
you're thinking it'd be a good idea for satellites? :-)
Henry Spencer
Cameron Dorrough <cdor...@spamspamgoawayrmna.com.au> wrote:
>> A 100 MWatt laser combined with a moderately sized telescope equipped
>> with adaptive optics, operating as a beam steering device - would
>
>And just what, praytell, would a 100MW laser do to the atmosphere, ozone
Nothing much, actually. It's a beam of *light* (well, probably infrared
actually -- many engineering problems get easier at longer wavelengths).
It isn't even all that intense, since the telescope spreads it out. For
obvious practical reasons, it would use a wavelength where air is quite
transparent.
>birds and anything
>else in it's path before getting to the target?
Any bird that wanders into the beam is in big trouble. Best not build the
thing in a bird sanctuary. A desert would be preferable.
Serious designs for such things invariably have a radar pointing along the
beam, which automatically cuts it off if something substantial (planes,
satellites) wanders near the beam unexpectedly. Might even work halfway
well for birds.
>Though you could always name the project "Star Wars", use it against
>incoming missiles and get congressional funding.. ;-)
Actually, the engineering problems tend to be quite different. Notably,
the weapons guys tend to want short wavelengths.
>At least if the thing is installed on a GEO satellite, you 1) don't need it
>to be as powerful
It would have to be *much more* powerful, because it's a hundred times
farther away. The debris problem is mostly in LEO.
>2) solar electricity is relatively plentiful...
Solar electricity in space is far more expensive, especially in megawatt
quantities, than any Earthly source, even diesel generators. Have you
*priced* space-rated solar cells lately? (And solar cells in GEO have a
strictly limited life; that orbit is in the fringes of the outer Van Allen
belt and the radiation rots them.)
Ground-based systems work much better for this.
Arie Kazachin
Hmmm... $200M a year plus initial $1B ... that leaves room for quite a few
cheaper ideas, for example:
Armed with the knowledge of the trajectory of an object you want to deorbit,
launch a sounding rocket vertically so that its apogee is at the orbit
of that object few seconds before the object arrives. The sounding rocket
disperses compressed air and falls back to earth (together with the air).
Assumimg the timing was precise enough for the deorbited object to arrive
VERY soon (seconds), the air density will still be high enough to slow the
object down. Since the orbital speed of the rocket is close to zero,
it'll not become a space junk. And in a rare event of it actually colliding
with the object to be dorbited, most of the debries will have their
speed greatly reduced and deorbit soon. A rocket capable of lifting a simple
compressed air tank to attitude without supplying it with orbital speed
seems quite cheat to produce. Maybe instead of carrying an air tank
the rocket will just carry some more fuel and apon arrival to apogee rotate
90 deg so that its exaust will be directed towards the object to deorbit,
thus the dispersing exaust gases will serve the same purpose. I think you
could make quite a few such launches for $200M.
******************************************************************************
* Arie Kazachin, Israel, e-mail: ar...@attglobal3.14159265358979323846.net *
******************************************************************************
NOTE: before replying, leave only letters in my domain-name. Sorry, SPAM trap.
Dr John Stockton
news:sci.space.tech, Arie Kazachin <ar...@attglobal3.1415926535897932384
6.net> posted at Mon, 19 Aug 2002 22:24:45 :-
>
>Armed with the knowledge of the trajectory of an object you want to deorbit,
>launch a sounding rocket vertically so that its apogee is at the orbit
>of that object few seconds before the object arrives. The sounding rocket
>disperses compressed air and falls back to earth (together with the air).
>Assumimg the timing was precise enough for the deorbited object to arrive
>VERY soon (seconds), the air density will still be high enough to slow the
>object down. Since the orbital speed of the rocket is close to zero,
>it'll not become a space junk. And in a rare event of it actually colliding
>with the object to be dorbited, most of the debries will have their
>speed greatly reduced and deorbit soon. A rocket capable of lifting a simple
>compressed air tank to attitude without supplying it with orbital speed
>seems quite cheat to produce. Maybe instead of carrying an air tank
>the rocket will just carry some more fuel and apon arrival to apogee rotate
>90 deg so that its exaust will be directed towards the object to deorbit,
>thus the dispersing exaust gases will serve the same purpose. I think you
>could make quite a few such launches for $200M.
Circular speed at 6400km radius (near ground) is 7900 m/s. At 6500 km,
7840 m/s; 6600, 7780; 6700, 7720; 6800, 7660.
To drop the perigee of an object in circular long-term orbit by a truly
significant amount (so that it becomes no more than a short-term object)
will require a change of velocity of the order of, say, 80 m/s, or 1%.
To obtain such a change of velocity by hitting what would be an
effectively stationary gas cloud would require the object to hit gas
totalling around 1% of its own mass. That is a very substantial amount,
for an object of non-trivial thickness and density; the whole of Earth's
atmosphere, from sea level[*] to space, is only about one kilogram per
square centimetre.
The scheme seems numerically impractical.
The area to be swept is of the order of 10^6 km^2 (200 km high, 5000 km
wide, over the equator). Launch a sweeper backwards (an Israeli
speciality), and it will have about 30 passes per day at any given
typical object; 10,000 per year. So, to complete the job in ten years
needs an area of around 10 km^2 - and highly reliable COLA for non-
debris.
[*] a bit more by Israel, of course.
--
© John Stockton, Surrey, UK. j...@merlyn.demon.co.uk Turnpike v4.00 MIME. ©
Web <URL:http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms & links;
some Astro stuff in astro.htm, gravity.htm; quotes.htm; pascal.htm; &c &c &c.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.
Jonathan Thornburg
> 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.
[[...]]
> 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.
This is a clever idea. Let's crank a few numbers to see how it works...
In article <3OwRfWHJ...@merlyn.demon.co.uk> (20 Aug 2002)
John Stockton discussed a similarly clever idea, having sounding
rockets dump a gas cloud into space (without orbital velocity) just
ahead of a debris chunk, so the debris would pass through the gas
cloud before the gas cloud dispersed. As John wrote then
> To drop the perigee of an object in circular long-term orbit by a truly
> significant amount (so that it becomes no more than a short-term object)
> will require a change of velocity of the order of, say, 80 m/s, or 1%.
>
> To obtain such a change of velocity by hitting what would be an
> effectively stationary gas cloud would require the object to hit gas
> totalling around 1% of its own mass.
In other words, if the aerogel is too tenuous, then debris won't be
decelerated enough by passing through it.
What matters here is basically the areal density of the absorber,
in grams/cm^2. That is, if you cut a debris-fragment-sized hole through
the absorber, the mass of absorber in that hole, m, is given by the
product of this areal density, and the hole's area. If a debris-fragment
of mass M passes through the absorber, it is then looses a fraction
m/M of its orbital velocity. We want this fraction to be at least
f=0.01.
[In my simplistic analysis, it doesn't matter whether
a given areal density comes from a very low-density
aerogel that's quite thick, or from a higher-density
aerogel that's a bit thinner.]
A line or two of algebra reveals that this means the absorber areal
density must be at least (4/3)*f*r*rho, where r is the typical radius
of a debris fragment and rho is the typical mass density of a debris
fragment. Setting rho = 3 grams/cm^3 gives f (in grams/cm^2) =
0.04 * r (in cm). So to deorbit 1cm-and-smaller diameter debris
fragments (a 1cm-diameter fragment has r = 0.5cm, and in this crude
masses around 0.4 grams) needs an absorber with an areal density of
0.04 grams/cm^2. That's 400 grams/m^2, so an absorber 100 meters
on a side has a mass of 4 tonnes. So far, so good.
Unfortunately, near-Earth space is *big*, so it takes a lot of
absorber area to sweep it in any reasonable time. As Henry Spencer
put it in another old post to this newsgroup, (article
<Ivq46...@spsystems.net> on 6 Mar 2006),
> An absorber 100 meters on a side --
> a *big* thing to build, especially since it needs a fair bit of mass per
> unit area -- sweeps out about 7000 cubic kilometers a day. Assuming you
> put it into a slightly elliptical orbit, with apogee 100_km higher than
> perigee so that it sweeps out a range of altitudes rather than just one,
> it's trying to sweep a shell with a volume of 53,000,000,000 cubic km.
> In 20 years it sweeps about 0.1% of that volume.
In other words, our 100-meter absorber just isn't big enough to do
the job in any reasonable time. If we want our system to sweep, say,
10% of that volume in 20 years (which is still not really "doing the
job in a reasonable time"), then it needs to be 100 times bigger,
i.e., 1 kilometer on a side. But now it masses 400 tonnes, so
launching it isn't quite such a simple job. :(
Making the system another factor of 10 larger in area, so it nominally
sweeps all the target volume in 20 years (i.e., so it's actually a
"solution" to the orbital-debris problem, at least in this 100km-wide
range of orbital altitudes) means it now has a mass of 4000 tonnes. :(
In other words, while the aergel system can be made to work, it's not
going to be small, fast, or cheap. :(
There's also another rather serious issue to worry about, namely the
fate of all the non-debris satellites in that range of orbital altitudes.
The aerogel probably has to have a substantial delta-V capability (i.e.,
it has to carry a rockets and (given its huge mass) a *lot* of fuel)
to be able to maneuver so as to avoid hitting any known satellites.
In fact, it's probably better to divide up that 4000 tonnes and 10 km^2
absorber area into 1000 100-meter-on-a-side 4-tonne absorbers, each
with its own maneuvering capability. This way "only" 4 tonnes of
absorber (+ rockets + fuel + control/structures/communication/etc)
has to be maneuvered each time there's a satellite in the way.
[The requirement to maneuver the absorber also means
that the whole thing (aerogel + any supporting structure)
has to be structurally strong enough to handle the
maneuvering g-forces. We probably want to make the
maneuvers as gentle as possible consistent with not
hitting other satellites.]
Someone has probably done a more careful analysis of such a
debris-sweeping constellation, but I've never seen it...
--
-- "Jonathan Thornburg [remove -animal to reply]" <jth...@astro.indiana-zebra.edu>
Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
"Space travel is utter bilge" -- common misquote of UK Astronomer Royal
Richard Woolley's remarks of 1956
"All this writing about space travel is utter bilge. To go to the
moon would cost as much as a major war." -- what he actually said