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Nanosatellite Takes Out The Trash
michael.creasy writes "The BBC has a article about a new nanosatellite due to be launched later this year. The idea is that the satellite be used to latch on to and slow down junk in space so that they will fall out of orbit and burn up on re-entry. " The only problem, as the article points out, is that there's no one really interested in purchasing this right now. Still, it's a pretty cool, especially if the price points are correct.
I don't understand why they are burning up $100,000 satellites just to take out trash. Why not build a more expensive satellite that can stay up longer? Would it be possible for one of these satellites to catch the trash, picking up a boost of energy, while deacclerating the garbage? How about a cheap ion engine to keep it in orbit, and a couple of solar panels? Sure $100,000 may be cheaper then an ordrinary satellite, but that isn't including the cost of launching these buggers, and it's still a heck of a lot more expensive then the trash itself - and there is a lot of trash.
-- perl -e'print pack"H*","6e656d6f406d38792e6f7267"'
This (Post-Flight Inspection of STS-90) is from NASA Orbital Debris Quarterly News:
Using samples collected by tape pull, dental mold, and wooden probe extraction techniques, a scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometers (EDXA) were able to identify the nature of 29 of the impactors. A total of 16 particles (55%) were found to be man-made debris, while the remaining 13 particles (45%) were meteoritic in nature. An analysis of the orbital debris impactors revealed an assortment of aluminum (56%), paint (31%), and stainless steel (13%) projectiles.
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The FAQ from this site says:
8). Does the U.S. Space Shuttle have to dodge orbital debris?
Whenever a Space Shuttle is in orbit, the U.S. Space Command regularly examines the trajectories of orbital debris to identify possible close encounters. If another object is projected to come with a few kilometers of the Space Shuttle, the Space Shuttle will normally maneuver away from the object, even though the chances of a collision are only approximately 1 in 100,000. This occurs infrequently, about once every year or two.
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If you notice, the Earth now has a ring similar to that of Saturn. With all this debris, finding an affordable commercial space solution will not be the only problem. It would be no good to see Titanic revisited. Just as icebergs are a problem at the turn of the century, space debris will be a problem during this century.
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Launches are very expensive. The Pegasus, which is one of, if not the lowest cost launch, runs at about 11 Million US. It could, though, pack quite a few of these birds on it. I wonder about the satellites' maneuvering propellant margins...
As satellites become smaller and more capable, not to mention cheaper, this places a downward pressure on launch costs. IMHO, this product is a bit premature, as the cost of getting it up is greater than the cost of acquisition.
The only current way to mitigate launch cost is hitching a ride along with another satellite. This causes porblems (ask the OSCAR guys.) As an example, you need a special dispenser that releases multiple payloads in such a way that they enter their proper orbits and don't come into contact. This technology is rather close to a piece of ICBM tech...
It is important, though, to try to clean up the orbit areas if we want to establish any real long-term orbital presence. the threat to hardware (and, eventually, wetware) is too ugly to ignore.
Would we need an entire spaceship to get all the damned unused AOL CDs off the planet? I mean, you can only use so many of them as coasters before they end up in the garbage. If everyone in America got 15-20 of those like I have, it'd take a couple of rocketships to get the billions and billions of wasted space off the ground. Still, they make effective weapons if you just sharpen the edges a little bit. Sharkey
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I'm surprised the US government hasn't invested in these babies to take out the occasional spy satellite:
Mission Control: Sir, the nanosatellite is now in position...
The commander puts his coffee down on a red button sticking up from the panel. Suddenly the nanosatellite attaches itself to a Soviet spy satellite
Commander: Ooooops. I didn't mean to do that. It was an accident, I swear! I'm just going to call my commanding officer and tell him that the mission was a succ.... I mean, that I should be demoted in rank for wasting a 100000 dollar piece of equipment... yes, that's it...
Malfunctioning satelites in a high orbit could be cheaply brought to low earth orbit where they could be repaired. This might generate more revenue than finding someone willing to pay to clean up old boosters.
If even that fails to generate revenue there are always other less nobel options: Pay us 10 milion or your 100 M satelite is fish food.
I wonder if these things are accurate enough to target Redmond?
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Actually, most stuff under ~750 km altitude will decay all by themselves within 25 years or so, give or take a solar cycle. Even big stuff. Stuff above that altitude is going to be around there longer, but under 750 km altitude is where precious things like shuttle, station, and hubble lay, so that's where the most concern is.
NASA has recently imposed requirements that all satellites deorbit within 25 years, either coming back to earth, or being boosted up to above 1400 km (iirc).
Also, there are a LOT of satellites way, way out at GEO. But these are spaced so far apart that we generally merely boost them up to a slightly higher orbit and leave them there. There is no drag at GEO so no fear of seeing them run into other stuff.
On the positive side, the smaller an item is, the quicker it de-orbits due to atmospheric friction. For example, a cloud of dust (or sand) would de-orbit from LEO within a couple days. It's all about altitude.
Techically, it's a function of altitude, mass, and surface area. Solar cycles play a role as well; when we're in a solar max condition (lots of sunspot activity), the atmosphere "thickens" and thus spacecraft are subjected to stronger drag forces and will decay faster. Surface area is very important. At the end of life we'll feather a spacecraft's solar arrays to maximize atmospheric impingement, and thus go down faster.
OMV is not tether-based, btw. (I work with the guys that designed it, and they are always pulling out the little models and such. *Grin*) In any case, all you need is surface area, so if you wanted to do something fancy, consider just hooking on a big inflatable sail dohicky - cheap, low mass, and effective.
If you have the power to spare for a tether, I'd wonder if it wouldn't be simpler to just use electric propulsion; for a few hundred watts and a few tens of kilograms (and a year or two) you can deorbit most anything. Getting back up out of the drag well would be challenging if you wanted to reuse the orbit maneuvering craft. Probably better to just deorbit the whole mess. But if a spacecraft operator is on contract to deorbit a spacecraft, they generally like to get it done ASAP, and having to wait a few years for a slow deorbit can be expensive.
But the fact of the matter is that most of the garbage up there is *tiny* - bolt heads from old explosive bolt mechanisms, pieces of tape or foil, and bits of metal from explosions or impacts. Small teeny stuff.
OK I was one of the team at SSTL that built that satellite, and it's probably time to set some of the record straight :)
;)
First junk busting is not entirely why we built SNAP. It's main application areas are:
1. Remote inspection: You throw it out of a space station to inspect damage etc.
2. Inferometry: You fly a bunch of them in formation to simulate a big dish/lens.
3. Space science: Fly a number of them to get multiple readings of something like the magnetosphere at each point in time. So you get both time and space measurements.
4. Satellite deorbiting: A SNAP spacecraft with large fuel tank could be used to track down and latch onto a dead satellite, then bring it down.
Now SNAP-1 is just a technology demonstrator. We're proving all the new miniaturised computer/transmitter/camera/propulsion systems actually work. That's why no-one has bought it, cuz it ain't for sale. We do obviously have people in contract negotiations with us to buy their own versions of the SNAP spacecraft.
So to sum up. SNAP-1 is a completely functional spacecraft in a 30cm diameter package. That's quite an impressive feat to pull off. We're flying SNAP-1 on the 28th June 2000. It's probably just got to the launch site as we speak. Once we've proved it works customers will then come to ask us to build new SNAP spacecraft for their particular missions.
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The answer to removing large pieces of junk from orbit is to send up a couple of tether-based OMVs to do it automatically.
Space tethers are basically conductive cables, maybe a mile long or more, that are suspended out of an orbiting vehicle. Because of gravitational gradients, the cable will align itself to be pointing down towards the ground. As the cables pass through the Earth's magnetic field, they convert velocity for energy, producing lots of electricity. It's like an electric motor.
Normally.
If, on the other hand, you run power through the cable, you trade electricity for velocity. Again, like an electric motor.
The end result is that you have a method of altering your orbit that doesn't require expending propellents. This technology will be installed on the Mir space station late this year or next, ending the reliance on Progress boosters.
Anyhow, the reason I'm bringing this up is that this is the key to removing big debris.
You launch an orbital maneuvering vehicle that uses this technology. It would rendezvous with the piece of debris and turn on the orbital brake (eg, use the tether to start generating electricity) until the object was on a re-entry vector, then it would detach and use the tether to raise itself to the orbit of the next piece of large debris.
The process could be mostly automated and wouldn't require expending propellent. Gyros would provide attitude control (and maybe energy storage for nighttime passes).
Of course, this only takes care of the stuff that's big enough to be tracked.
On the positive side, the smaller an item is, the quicker it de-orbits due to atmospheric friction. For example, a cloud of dust (or sand) would de-orbit from LEO within a couple days. It's all about altitude.
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I remember a gentleman from NORAD come to my school about 4 or 5 years back to discuss what exactly they did up there. One of the facts that they gave us was that they were (then) tracking over 65,000 objects in and around earth's upper atmosphere. Most of it man made trash.
:P
When you realize that if one of these hits a satelite or (worse) space, shuttle...at the velocity it's going...it would basically tear a hole right through it.
I think in the best of all possible worlds, the U.N or some other international organization would get together to find the funds for something like this. It's getting pretty cluttered up there, and i don't want to have to see a whole bunch of garbage when i take my scenic trip to the moon in 2014.
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