Quote from: Jim on 03/16/2009 12:07 pmQuote from: LegendCJS on 03/16/2009 11:23 amThe 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?
Quote from: LegendCJS on 03/16/2009 11:23 amThe 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.
The US military can turn off the civilian component of the GPS signal completely in whatever conflict zone they choose.
THis makes for some interesting reading:http://books.google.com/books?id=q0qVc8dQrpgC&pg=PA48&dq=%22kessler+syndrome%22&ei=8FuxSaLGN6OOyQS7x_nNDQ#PPA51,M1
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.
Quote from: mlorrey on 03/17/2009 02:33 pmNow, 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 mv2Defunct satellite 1,000 kgRelative velocity 10,000 m/sTotal energy = 5 x 1010 J = 10 tons of TNTA 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.
Quote from: gospacex on 03/18/2009 05:12 pmThat'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.
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.
Quote from: mlorrey on 03/17/2009 02:33 pmNow, 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.
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.
Quote from: khallow on 03/19/2009 05:48 amHowever, 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.