Author Topic: Kessler on the Kessler Syndrome (March 8, 2009)  (Read 26899 times)

Offline Jim

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #20 on: 03/16/2009 12:24 pm »

The US military can turn off the civilian component of the GPS signal completely in whatever conflict zone they choose.

That is not true.  It is always on.


I'll take your word for it.  It seems strange to me tho, but maybe the de-tuning to +- 35m accuracy leaves other methods (old fashion map and compass based) more accurate, so its pointless to turn the civilian signal off completely?


Just think of mechanics of trying "turning it off" one region.  30 or more spacecraft, in different positions, with only 6 (ground stations),etc.  The region would be huge.  Also turning on and off a signal that has be calibrated and validated.  What insures it is good when it comes back on?

And also I believe the military signal is not standalone, it still needs the basic signal.
« Last Edit: 03/16/2009 12:26 pm by Jim »

Offline Warren Platts

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Offline mlorrey

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #22 on: 03/17/2009 02:33 pm »
THis makes for some interesting reading:

http://books.google.com/books?id=q0qVc8dQrpgC&pg=PA48&dq=%22kessler+syndrome%22&ei=8FuxSaLGN6OOyQS7x_nNDQ#PPA51,M1

"If we had 10 platforms in orbit each 100 meters across, one would get hit each year."

Thats nice, what SIZE of object are we talking about here is going to strike? The article talks about objects down to 1 mm in size, which is something even the shuttle has previously dealt with and which even spacewalking astronauts are trained to handle. http://www.newscientist.com/article/dn10235

Furthermore, his comment is as if a 100x100x100 meter cubic volume is all pressurized modules and critical systems. Even the ISS doesnt approach a tiny fraction of one such platform.

That said as most here understand, LEO isnt one specific altitude, it is a wide range of altitudes from 100 miles up to a few thousand miles.

Now, how hard would it be to put up a few 'scrubbers'? I can imagine orbiting a satellite that would inflate a hugh Echo type baloon with aerogel, and use electric propulsion to slowly maneuver through a range of orbital planes before deorbiting. A 100 meter sphere of aerogel should be sticky enough to catch most anything.
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Offline Warren Platts

Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #23 on: 03/18/2009 01:01 pm »
Now, how hard would it be to put up a few 'scrubbers'? I can imagine orbiting a satellite that would inflate a hugh Echo type baloon with aerogel, and use electric propulsion to slowly maneuver through a range of orbital planes before deorbiting. A 100 meter sphere of aerogel should be sticky enough to catch most anything.

K.E. = 1/2 mv2

Defunct satellite 1,000 kg
Relative velocity 10,000 m/s

Total energy = 5 x 1010 J = 10 tons of TNT

A direct hit by a Cosmos 2251-like satellite might wind up blowing your gel ball to smithereens. And what goes up must come down. The Aussies might not appreciate flaming gel-balls crashing into the outback.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline gospacex

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #24 on: 03/18/2009 05:12 pm »
Now, how hard would it be to put up a few 'scrubbers'? I can imagine orbiting a satellite that would inflate a hugh Echo type baloon with aerogel, and use electric propulsion to slowly maneuver through a range of orbital planes before deorbiting. A 100 meter sphere of aerogel should be sticky enough to catch most anything.

K.E. = 1/2 mv2

Defunct satellite 1,000 kg
Relative velocity 10,000 m/s

Total energy = 5 x 1010 J = 10 tons of TNT

A direct hit by a Cosmos 2251-like satellite might wind up blowing your gel ball to smithereens. And what goes up must come down. The Aussies might not appreciate flaming gel-balls crashing into the outback.

That's why I prefer flat plate style scrubbers. They can't be blown up, only holed. Imagine how cool Cosmos-2251 shaped hole in the plate would look like :)  Not that it is intended to clean up whole sats, but it at least can survive one impacting it.

Offline MKremer

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #25 on: 03/18/2009 05:31 pm »
That's why I prefer flat plate style scrubbers. They can't be blown up, only holed. Imagine how cool Cosmos-2251 shaped hole in the plate would look like :)  Not that it is intended to clean up whole sats, but it at least can survive one impacting it.

You'd end up with a bunch of satellite debris, too, with too thin a 'plate'. Much of the larger pieces with hardly any change in energy, either, but now spreading into different orbits making the 'junk' situation even worse.

If you're going to use an impact plate, make it thick and massive enough to survive even larger impacts, so any debris left over is robbed of much of its kinetic energy.
« Last Edit: 03/18/2009 05:37 pm by MKremer »

Offline khallow

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #26 on: 03/18/2009 05:31 pm »
Now, how hard would it be to put up a few 'scrubbers'? I can imagine orbiting a satellite that would inflate a hugh Echo type baloon with aerogel, and use electric propulsion to slowly maneuver through a range of orbital planes before deorbiting. A 100 meter sphere of aerogel should be sticky enough to catch most anything.

K.E. = 1/2 mv2

Defunct satellite 1,000 kg
Relative velocity 10,000 m/s

Total energy = 5 x 1010 J = 10 tons of TNT

A direct hit by a Cosmos 2251-like satellite might wind up blowing your gel ball to smithereens. And what goes up must come down. The Aussies might not appreciate flaming gel-balls crashing into the outback.

I guess it wouldn't be a good idea to run into such a satellite then. If you can get the density of the gel-ball low enough, then it won't heat up to burning temperatures when it reenters.
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Offline LegendCJS

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #27 on: 03/18/2009 06:00 pm »
Now, how hard would it be to put up a few 'scrubbers'? I can imagine orbiting a satellite that would inflate a hugh Echo type baloon with aerogel, and use electric propulsion to slowly maneuver through a range of orbital planes before deorbiting. A 100 meter sphere of aerogel should be sticky enough to catch most anything.

Aerogel?  You can't treat aerogel like you treat a can of shaving cream or spray foam insulator.  To make aerojel you need a mass of liquid water or CO2 jelled with the jelling agent and the whole mass needs to be in the final desired shape.  Then you pressurize the relatively incompressible liquid and bring it on a path around and over the liquid's critical point on the PV plane, then lower the pressure but keep the temperature and bleed it off as a vapor without ever having made the liquid go through a phase transition to vapor.  That is how the structure and shape of the jelling agent is preserved with all the voids intact- no evaporation happens.  This can't be done in space like you think in an 'inflationary" manner like blowing up a balloon.

A note to all the people championing ideas that involve collisions in space- why do we want more things smacking into each other at orbital velocities up there?  Common sense and experience shows that at those energies it just ends up making more debris.
Remember: if we want this whole space thing to work out we have to optimize for cost!

Offline gospacex

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #28 on: 03/18/2009 06:02 pm »
That's why I prefer flat plate style scrubbers. They can't be blown up, only holed. Imagine how cool Cosmos-2251 shaped hole in the plate would look like :)  Not that it is intended to clean up whole sats, but it at least can survive one impacting it.

You'd end up with a bunch of satellite debris, too, with too thin a 'plate'. Much of the larger pieces with hardly any change in energy, either, but now spreading into different orbits making the 'junk' situation even worse.

Define "larger".

For every foot-sized chunk there are ten 1/3 foot sized chunks, so there are more small chinks to clean up than big ones. Also, untrackably small chunks are more dangerous, ISS et al. can't dodge those => again, cleaning up those is more important.

Quote
If you're going to use an impact plate, make it thick and massive enough to survive even larger impacts, so any debris left over is robbed of much of its kinetic energy.

Plate made with the same technology as ISS protection will stop dead 1 cm sized impactors, and I'll hazard to guess will shatter and deorbit impactors up to ~10 cm. These bigger ones will hole the plate, but it is sacrificial anyway.

This is already not so bad. The real problem is "who is willing to foot a bill for such a thing?"

Offline gospacex

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #29 on: 03/18/2009 06:09 pm »
A note to all the people championing ideas that involve collisions in space- why do we want more things smacking into each other at orbital velocities up there?  Common sense and experience shows that at those energies it just ends up making more debris.

What about a scrubber on retrograde orbit? It will have mean collision speeds of about 12 km/s, and impacts debris in the best direction for deorbiting it - roughly opposite to debris' velocity vector.

Offline khallow

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #30 on: 03/19/2009 05:48 am »
Now, how hard would it be to put up a few 'scrubbers'? I can imagine orbiting a satellite that would inflate a hugh Echo type baloon with aerogel, and use electric propulsion to slowly maneuver through a range of orbital planes before deorbiting. A 100 meter sphere of aerogel should be sticky enough to catch most anything.

Aerogel?  You can't treat aerogel like you treat a can of shaving cream or spray foam insulator.  To make aerojel you need a mass of liquid water or CO2 jelled with the jelling agent and the whole mass needs to be in the final desired shape.  Then you pressurize the relatively incompressible liquid and bring it on a path around and over the liquid's critical point on the PV plane, then lower the pressure but keep the temperature and bleed it off as a vapor without ever having made the liquid go through a phase transition to vapor.  That is how the structure and shape of the jelling agent is preserved with all the voids intact- no evaporation happens.  This can't be done in space like you think in an 'inflationary" manner like blowing up a balloon.

I guess we'll just have to settle for a stiff foam then.

Quote
A note to all the people championing ideas that involve collisions in space- why do we want more things smacking into each other at orbital velocities up there?  Common sense and experience shows that at those energies it just ends up making more debris.

We want less things smacking into each other. Hence, the proposals to remove or slow down orbital debris. Common sense and experience shows that you are incorrect in your last sentence. Sure slamming large dense objects into each other has been shown to create a lot of debris.

However, we have plenty of cases where a orbiting object is "sticky" enough to absorb the impact of another, much smaller object. For example, things collide with the ISS all the time. They're microscopic and get embedded in the ISS's skin. mlorrey's proposed aerogel ball is intended to catch or slow down small objects not one ton satellites.
Karl Hallowell

Offline LegendCJS

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #31 on: 03/19/2009 01:35 pm »
However, we have plenty of cases where a orbiting object is "sticky" enough to absorb the impact of another, much smaller object. For example, things collide with the ISS all the time. They're microscopic and get embedded in the ISS's skin. mlorrey's proposed aerogel ball is intended to catch or slow down small objects not one ton satellites.


Have you seen the videos of the debris impact tests during ISS shield material development?  It sure looks like a lot of crap is flying away form the points of impact to me.  Maybe its just gasses and plasmas and it dissipates harmlessly, but I'd like to know for sure what those "splashes" of material are at the impact sites before saying that the impact is completely or even usefully sticky.

I'm going to outline my initial thoughts about the foam scrubber concept.  Don't get me wrong, I relish challenging engineering design projects, and I'm not saying that these issues are insurmountable.  Every worthwhile project is challenging.

Any maneuverable foam ball will have to have thrusters, sensors, power sources (solar panels), antenna, and everything else that goes with a standard spacecraft.  All this hardware will need to be attached to a structural skeleton of some sort.  Especially the thrusters, so they don't punch right through the foam when you turn them on to do orbit changes.  At minimum all the thrusters and other components that depend on precise orientation will need to be rigidly connected to each other. 

To justify the need for a rigid skeleton structure for the foam read the following:  I've got images of a wobbling and gyrating mass of foam after a large impact in my head.  If the thrusters are only sunk in to local unconnected anchor sites around its periphery, its going to be a very hard thing to control or move while the relative orientation of the thrusters is changing randomly with time due to the heaving waves of foam underneath it.  If you try to make the foam stiff, it will have trouble being as stiff as required (remember its a big ball we are talking about here) without also loosing its ability to capture the debris in sticky collisions.  In addition every collision changes the structural characteristics of the foam mass in an un-predictable way.   So you can't rely exclusively on the foam for long term structural support or for short time stability, especially when you might need it most- to regain control after a particularly large impact.

There will need to be some kind of radiative heat rejection and thermal management of the foam mass to keep it in a stable and narrow temperature range in order to extend the foams life,  Otherwise the solar heating and cooling thermal expansion cycle will wreck the foam's integrity in no time.  The thermal management equipment will also be called on to cool the foam mass down especially after absorbing some significant impacts.  All that will require equipment distributed throughout the foam and large space viewing radiators that should also not be hit by the debris. 

Then there will need to be a trade off between how much help the foam gets in finding its debris to absorb from the ground vs from its own sensors.  The trade off needs to factor in the sensor mass and power requirements, the lead time the sensors give for different types and sizes of debris, and the reaction time and capabilities of the scrubber's thrusters.  It is a question of the needed positional accuracy to absorb the target piece of debris.  I don't know to what accuracy the orbit of the debris to be cleaned is known.  I do know that the smaller the debris the less accurate their orbits are known, so the best debris to absorb might have to be found with short notice by the scrubber itself, thus requiring powerful chemical thrusters.

Given that the scrubber is being repeatedly and purposely directed into harms way on a frequent basis, the chances that a part of the 'scrubber' getting hit that you don't want getting hit increases dramatically.  The chemical rocket thrusters might also be needed to quickly change the projected point of impact of the particular piece of debris if its found to have been a risk to a critical hardware component of the scrubber.   So the best fuel sipping thrusters for the job- hall effect or ion thrusters, might be inadequate.

Don't say you can put the foam in front and the hardware in back and then try to take all your hits form the same 'front side' direction.  Doing that will cause the scrubbers orbit to degrade or change much faster than it needs to in comparison with taking hits from all directions (assuming you can model the debris momentum flux as evenly distributed form every direction).  And you can't do all the maneuvers you might need to do if you mount all your thrusters so they thrust in the same hemisphere i.e in the 'back.'

So there are some challenging design issues here, not to say they can't be solved, but challenging none the less.  But every worthwhile project is challenging.  Maybe people can propose more specifics about the foam scrubber concepts and get some of these details worked out.
Remember: if we want this whole space thing to work out we have to optimize for cost!

Offline gospacex

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Re: Kessler on the Kessler Syndrome (March 8, 2009)
« Reply #32 on: 03/19/2009 02:19 pm »
However, we have plenty of cases where a orbiting object is "sticky" enough to absorb the impact of another, much smaller object. For example, things collide with the ISS all the time. They're microscopic and get embedded in the ISS's skin. mlorrey's proposed aerogel ball is intended to catch or slow down small objects not one ton satellites.

Have you seen the videos of the debris impact tests during ISS shield material development?  It sure looks like a lot of crap is flying away form the points of impact to me.  Maybe its just gasses and plasmas and it dissipates harmlessly, but I'd like to know for sure what those "splashes" of material are at the impact sites before saying that the impact is completely or even usefully sticky.

I didn't see videos, do you have URLs?

I saw some photos. Basically, when projectile impacts first layer, it gets shattered to pieces, or vaporizes completely if it is small enough. Then these pieces and vapors fly further through standoff gap, and impact the second layer. Impact area is bigger, but the force of the impact is smaller.

The ideas here (I guess) are (1) to produce many smaller impacts over the wider area instead of one, nearly pointlike impact which delivers all enrgy and impulse to a small area, and (2) let some part of energy to be released as light while vapors travel through the gap, and expend some of the energy for melt and vaporization.

This works best when the gap is wide, and first layer is dense. Not necessarily heavier - we want to drive as strong shock through the projectile as we can, and for that we need denser material. For example, at the same mass aluminum wall will perform worse than steel one.

If this design is to be adapted into a dedicated debris scrubber, the gap can be made really big (a few feet) to increase the diameter of debris cone, third wall can be added to repeat the same process when debris cone impacts second wall, and so on.

This can be refined further by folks who know this stuff better. I've seen advanced models with more than two walls, with two closely-spaced walls instead of one wall in the front etc. I don't know why is that better, guess there are some subtler effects at play.

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