I Love Learning Something New - Again
>> Saturday, May 22, 2010
Well, I'm back from the conference and I think it went well. I think my own paper was well received and I saw a number of other presentations that were very nice or thought-provoking, particularly one that used lessons learned from a rather tragic sledging expedition in Antarctica. It might seem a stretch, to compare them, but I thought he had excellent points. When everything you need to survive has to be brought with you, when you might be stranded or cut off from your home base, you need to be prepared and think it through. Lessons learned from this I thought quite applicable to Moon or Mars EVA expeditions and missions.
Another interesting presentation was on EDDE, a proposed debris cleaning program for Low Earth Orbit. Now, I've been pretty skeptical that cleaning out the debris is a practical notion, but, I have to say, this idea was intriguing to me. Using a tethering system to gain energy as well as change altitude/inclination very quickly without propulsion - thanks to the electromagnetic field around the Earth (and I find that cool beans). It's not science fiction; tethers have been used several times in the past with considerable success.
According to the presentation, they could change hundreds of km a day in altitude, quite a bit in inclination and, theoretically, clean out all the cataloged debris up to an altitude of 2000 km in less than seven years with just twelve 100 kg units. Units could deorbit themselves or stay as policemen. Now, they claimed they didn't have to worry about uncataloged debris (I'm less sanguin about that) though I agree they could avoid the cataloged stuff. And I'd want more than a power point presentation before I was sold on the idea, but, it seemed like a fine idea.
Although all the small stuff doesn't get cleaned out this way, you limit the generation of more debris by taking out the big stuff. The smallest stuff is the most readily cleaned out by natural processes. They bring the stuff down to 330 km (pretty much below anywhere dangerous) and were natural atmospheric friction will bring it down in weeks instead of decades. As the electromagnetic field at geostationary is not strong enough to use this there, it's limited to LEO, but that is where many of our valuable assets are.
Even if it didn't completely solve the problem, if effective, it could make a real difference.
They have an animation of this that's well worth watching here. If it doesn't work, the link above (EDDE) has it there as well.
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I'd heard people complain about all our "junk" floating around out there, but until I watched that animation I didn't realize there was so much of it! I guess it might be a good idea to clean some of it out, huh?
Sounds like you had a successful conference. Good deal!
I agree with Roy, you don't get the full idea of how much stuff is out there, and what it can do...
sounds like it went good.
How awesome an idea is that! I admit I'd feel a lot better seeing people fly up there knowing we'd cleaned up a bunch of the crap we've spewed up there over the last century.
but, isn't it more risky to deorbit the large pieces of junk. I know most of the equipment we put up there would burn up, but I know of a few deorbited satellites that crashed into the ground and we had to blow up one satellite because it had a toxic fuel. Thus, they would need a detailed catalog of the junk they are dealing with and maybe a space station to deal with the biggest and toxic systems.
These things are all going to come down uncontrolled anyway (and this system, supposedly, will allow for a more controlled reentry process as well - still to be demonstrated).
If something is desperately large, theoretically, one can give it a kick to encourage it to land somewhere benign. The satellite filled with toxic fuel was a fluke, by the way, and there are many who think it was shot down more to demonstrate a capability rather than necessity (noting it was hard on the heels of China's demonstration). However, having a satellite go defunct still full to bursting with fuel is unusual and, in most cases, even toxic fuel will burn up nicely in orbit.
One exception and something we should check out first: any satellites with nuclear fuel as "burning up" will do nothing to neutralize it and we'd be spreading it over a large area. For that reason alone, it's a question worth asking: is there something that poses a danger during reentry. So, Aron, it's a good question.
Wouldn't the smaller pieces accrete over time, allowing them to be more accessible to removal?
Or just burn up as they lose altitude.
Geez, the Mother, I had to look up the word accrete.
Actually, in space, things don't clump together. Usually, things are going so fast (relative to each other up to 18 km/s) that they are far more likely to break each other into smaller pieces than glom together into bigger pieces. (Glues/adhesives and the like do very poorly in vacuum and the temperature extremes, by the way).
Smaller items, however, once they've worked themselves into a low enough orbit to interact with the vestiges of the atmosphere tend to deorbit faster than larger objects. It's a surface area to mass ratio thing.