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How Safe is Space? New Study Spotlights Anti-Satellite and SpaceDebris Risks.
How Safe is Space? New Study Spotlights Anti-Satellite and Space
Debris Risks. http://www.spacesecurity.org/SSI2008.pdf |
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How Safe is Space? New Study Spotlights Anti-Satellite and SpaceDebris Risks.
On Sep 26, 11:56*am, Michel wrote:
How Safe is Space? New Study Spotlights Anti-Satellite and Space Debris Risks.http://www.spacesecurity.org/SSI2008.pdf There are over 12,000 space objects registered with the UN, of this total, 6,000 are still on orbit. http://www.uni-koeln.de/jur-fak/inst.../workshop05/10 These are not a hazard, their orbital parameters are well defined. Imagine 6,000 refrigerators tossed across the surface of the Earth- they would be hard to find even let alone run into. Of course, all objects are moving and sweeping out vast volumes of space - but the volumes of space are vast as well. The space between Earth's surface and geosynch orbit is over 40 times the entire volume of the Earth itself. Cut into spheres every 10 meters the total surface area created is millions of times the surface area of Earth - so we are in most cases talking about something the size of a refrigerator or automobile - and only 6,000 of these in well defined orbits. What is of concern is the numbrer of tiny objects shed b these larger objects over time, and their dispersal through this vast volume. For example, there is a famous photo of a crack in the space shuttle window created by collision with a tiny paint chip less than a millimeter across, shed by a Gemini capsule in the 1960s. There is a problem of detection, and a problem of what to do about it. NORAD and later the Aerospace Command has high power radars that have the capacity to track objects the size of a nut or bolt on orbit out beyond GSO. Modern LIDAR - laser light distance and ranging - methods can extend this down to the micrometer range. LIDAR can even be switched to a higher power mode, involving laser sustained detonation (LSD) - where a portion of the object is evaporated with laser energy and then the vapor formed is detonated with laser energy providing a controlled propulsive effect. A LIDAR / LSD combination in the 100 MW range should be capable of sweeping out small objects like the paint chip just described - in less than five years. A continuous sweeping operation should be added to a dedicated survey to detect NEAs and NEOs since the complement one another. LIDAR / LSD detects and sweeps away - into lower orbit and eventually re-entry - all objects larger than a millimeter and smaller than 10 centimeters - if limited to 100 MW.. For objects smaller than a millimeter - one sweeps them up physically with a sweeper mechanism made of a thin sheet of material that absorbs the materials in the size range desired. These sweepers avoid larger objects altogether. Once the smaller objects are swept up into the sweeper,solar wind and solar light pressure is used to bring the sweeper down to burn up in the atmosphere.. Proposed Sweeper PET plastic is 1.2 grams per cubic centimeter. An 8 micron thick layer of this film masses 9.6 grams per square meter. 9.6 metric tons per square kilometer. Evacuated aerogel is 1 milligram per cubic centimeter. A foamed in place aerogel that is 9.6 millimeters thick atop a PET film masses another 9.6 grams per square meter - 9.6 metric tons per square kilometer. So, a 20 metric ton satellite with an 800 kg mechanism can take 19.2 metric tons of materials and fabricate 1 sq km 'sweeper' - a disk 1,128 meters in diameter. 10 such satellites launched into orbits every 2,800 km in altitude out to GSO use light pressure to graduallly lose altitude- avoiding the 6,000 large objects - as they gradually descent - clearing out the equatorial ploane. A more agressive campaign involves 40 sweeper satellites in retrograde polar at longitudes 9 degrees apart - precessing in a non-synchronous way. When they precess 9 degrees they drop 10 kms due to solar pressure. Starting at 30,000 km and dropping 20 meters per week - in 28 years - they will have evacuated every particle orbiting everywhere above Earth out to 30,000 km. The laser/lidar/lsd system, the 50 sweepers - constitute a total cost of approximately $5 billion. There are 50 or so space launches per year - a tax of $10 million per launch, would collect sufficient fees to run this sort of operation. This leaves the larger 6,000 objects of which 2,800 are non- functioning. Here, one only need make it legal for registered and certified recovery operators to capture these objects return them safely to Earth and sell them as collector items. Here the fee to collect each object starts at $3 million - and collecting all of the non- functioning satellites collects $8.4 billion. Assuming one launch per collection attempt, another $28 billion is raised in per launch fees. In this way, at the present launch rate, sweeping operations may be continued indefinitely - as well as surveys to watch out for NEAs and NEOs. NEAs and NEO capture for industrial development is another revenue source, and another topic, though related. |
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How Safe is Space? New Study Spotlights Anti-Satellite and SpaceDebris Risks.
On Sep 26, 8:56 am, Michel wrote:
How Safe is Space? New Study Spotlights Anti-Satellite and Space Debris Risks.http://www.spacesecurity.org/SSI2008.pdf Without specific knowledge of where each and every bit of debris larger than a sugar cube is, and of where it's going, you're taking great risk, especially since so much tonnage has become unaccounted for. There's only a few of those highly sought after GSO parking spaces left, unless something else is eliminated. LEO is getting crowded, especially for missions that must avoid the SAA contour. ~ BG |
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How Safe is Space? New Study Spotlights Anti-Satellite and SpaceDebris Risks.
Claude Hopper wrote: There are many rock bullets flying around out there. Just look at the sky any night and see at least one shooting star (a rock bullet that enters the atmosphere) and notice the speed of entry! This is fun in regards to velocities, mass, and impact energy potential of various types of space objects on the surface of the Earth: http://www.lpl.arizona.edu/impacteffects/ If nothing else in regards to this thread posting, it gives you some rough estimates of the velocities of various types of things that hit Earth's atmosphere, and would of course hit anything in orbit at full initial speed. Pat |
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How Safe is Space? New Study Spotlights Anti-Satellite and Space Debris Risks.
Claude Hopper wrote:
There are many rock bullets flying around out there... Those entering the atmosphere make only one pass. Those in the Leonid, Taurid etc. "streams" that don't enter the atmosphere typically make only one pass per year. With a little thought, you can probably figure out why man-made orbital debris that spends months to centuries orbiting the earth every 85-300 minutes, nearly all of it (surprise!) at distances and inclinations quite like those of satellites and spacecraft, poses risks that are greater by many orders of magnitude... And why measures to prevent creation of new man-made debris are a lot more practical than vacuum-cleaning the solar system.... And therefore, why responding to "man-made debris is dangerous" with "yebbut there's natural debris too" might sound a little beside the point. |
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How Safe is Space? New Study Spotlights Anti-Satellite and SpaceDebris Risks.
On Sep 27, 9:22 am, Monte Davis wrote:
Claude Hopper wrote: There are many rock bullets flying around out there... Those entering the atmosphere make only one pass. Those in the Leonid, Taurid etc. "streams" that don't enter the atmosphere typically make only one pass per year. With a little thought, you can probably figure out why man-made orbital debris that spends months to centuries orbiting the earth every 85-300 minutes, nearly all of it (surprise!) at distances and inclinations quite like those of satellites and spacecraft, poses risks that are greater by many orders of magnitude... And why measures to prevent creation of new man-made debris are a lot more practical than vacuum-cleaning the solar system.... And therefore, why responding to "man-made debris is dangerous" with "yebbut there's natural debris too" might sound a little beside the point. Either by natural or artificial flack, we're somewhat screwed as far as safe space travel is considered. Parking your butt on the moon is actually a whole lot worse off than LEO, however the Selene/moon L1 might be relatively clean, except for being hotter than hell and gamma radiated. ~ BG |
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