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Clumping Satelites together...

Posted by: Sean Girling - Tue Apr 25, 2006 12:39 pm
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Clumping Satelites together... 
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Post    Posted on: Tue May 09, 2006 10:56 am
Hello, Sean Girling,

I mostly agree.

I thought the External Tank of the shuttles is completely burned at reentry - does it explode instead?

In that case I would prefer one proposal and recoent from officials. The proposal say that stages and tanks should go to safe orbits by consuming completely propellant left after releasing the payload. This would mean also that the stages and tanks might reused later perhaps.

At least they could be used to reflect radar-beams - the interruption of which would indicate small objects not traceable from Earth. Perhaps the stages and tanks could be equipped by small receivers and senders enabling htem to detect interruptions themselves and report them to stations, satellites, ground stations and so on.

This could help to relay exact positions of the satellites to be clumped.

What about using micro-gravity ...? The small satellites might react to it ...



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Post    Posted on: Tue May 09, 2006 9:02 pm
Sean Girling wrote:
Hell, they could use GPS to relay their exact position couldn't they? Why don't all satellites and space craft have GPS? These could be attached to large object that we know will become junk too. Like the shuttle's external tank?


I wouldn't trust GPS for close proximity operations, it's not accurate enough by itself. You need close in ranging and imaging technology to get really close.

That and GPS is a MEO satellite. Not very useful for GEO satellites, although there is some bleed over of GPS signals.

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Post    Posted on: Tue May 09, 2006 9:37 pm
I would have thought it would be relatively straight forward to use laser ranging to hold position.

Even estate agents use small laser measures to survey properties these days, so the technology is pretty common. I dont know whether that would be accurate enough or if you would need something more complicated.

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Post    Posted on: Wed May 10, 2006 7:24 am
Yeah, sorry, I meant GPS so the world and their dog would know there was a sat, just, there! But close proximity manouvering or docking or the like would use the more acurate short range devices that NASA now seem to be investigating.

At the moment a lot of satellites positions are found using ground based systems, such as radar. I just thought it would be better if the data stream from a sat included where it thought it was. That would make things easier. Of course, they might already do just that, I'm just not aware of it.

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Post    Posted on: Wed May 10, 2006 7:59 am
Hello, Sean Girling,

the idea to include the satellite's position in the data stream it sends to others or to the ground is a very good idea I think. It should be one within a "vector" of methods and ways providing the information about the position and would be an additional way also to command a change of the position.

...



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Post    Posted on: Fri May 19, 2006 10:26 am
Hello, Sean Girling,

the article "NASA Releases Summary of DART Mission Mishap" ( www.space.com/news/060515_dart_mishap_summary.html ) says that
Quote:
According to the mishap summary, DART’s velocity measurements by its primary global positioning system (GPS) receiver were off by about 1.9 feet per second (0.6 meters per second), an inaccuracy that persisted in the spacecraft despite a computer reset because the needed software patch was never installed.
.

Obviously DART was using GPS and the only problem was a software problem a patch existed for which would have removed the problem.

DART weighs 362 kilograms according to the article and it approached another satellite weighing 49 kilograms only - from a distance of several hundred kilometers.

I couldn't find out yet the size and volume of DART.

Would you consider this to be encouraging regarding your idea?



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Post    Posted on: Fri May 19, 2006 10:47 am
Yep, another clever idea already fleshed out by some other clever people. Shame they hadn't patched that software. But the fact that it works, dispite the hiccup, in very promising, because basically, the scientists are sitting back happy (ish). Even that failure has validated the technique, because they know why it didn't work, so the next one will.

Science fiction rarely stays that way now. "Hey repair sat four, go to this comm sat, and replace it's aging antenna" And off it goes.

Hey, that puts and idea in my head. An autonomous sat could be given the locations of junk, which it could clamp onto, nudge to de-orbit, release, and move onto the next. When it's propellant is running low, it could dock with the ISS for a refill, and off it goes again. A little automatic orbital cleaner. With an ion drive or two, it could well just be left alone, and it only be seen every three or four months for a top up. It'd know where the targets were, and it's relatively easy to work out how and where to de-orbit the junk. What do you think? It's really just an extension of the now existing technology.

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Post    Posted on: Fri May 19, 2006 11:02 am
Hello, Sean Girling,

except for my preference for collecting debris instead of deorbiting it I fully assist your idea.

And why consider the articles to say that others already had your idea? To me they merely assist you and agree to you - you are on the right way to develop further what others do now: You are the future while the others may be going to be the past.



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Post    Posted on: Fri May 19, 2006 11:45 am
Cheers mate for the happy spin. I really do enjoy seeing ideas come to life. Now I'm not in a position to affect many of the little ideas that come to me, (for we all think of little ideas every day) but when you see that some other clever boffin has implimented the very same solution that I thought of, well it gives me a little boost. I talk to my mates and say, "Hey, remember that idea we had while drinking the other day, well someone's gone and done it, how cool is that." And so we all have a giggle about it. Obviously sometimes we wish we'd written it down and done something about it. But, that's life.

You're right about collecting the junk, but I wouldn't yet consider it's worth to be sufficient. I guess there'll be a time when an orbital junk yard could be mined for useful metals, but I can't see it happening real soon. In the mean time, they're a danger to our ever growing constalation of expensive and still functional equipment.

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Post    Posted on: Fri May 19, 2006 3:17 pm
Sean Girling wrote:
Hell, they could use GPS to relay their exact position couldn't they? Why don't all satellites and space craft have GPS? These could be attached to large object that we know will become junk too. Like the shuttle's external tank?


Sure, tell that to the NASA DART folks. It was GPS positioning errors that led to the on-orbit collision.

GPS is useful for LEO satellites, not so good for other orbits (which are above GPS).

For formation flying, laser ranging is far more accurate to maintain separation. GPS is good for determining the location of the whole cluster.

We've thought about tracking devices also. The shuttle's external tank burns up relatively quickly, so it's not an issue. My biggest concern is spent upper stages, especially solid rocket motor engines (there is usually some residual slag, not to mention unburned chunks thrown out during the burn). The US Air Force is moving away from using solid rocket motor engines and is also using more integrated kick motors. Less junk this way.

Large, known debris, should use some sort of tracking enhancement devices. GPS would be nice, but is not always practical. We're recommendning optical and radar tracking enhancement devices were practical.

If you're going to create debris, keep it big and trackable, or burn it in quickly.

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Post    Posted on: Fri May 19, 2006 3:42 pm
With regard to the GPS, couldn't the device pick up the signal from the satellites on the other side of, not quite obscured by the earth? I don't know if the signal is strong enough though, or even if the footprint reaches beyond each horizon so it'd be useful that way. Shame they're not unidirectional. I wonder if the new European proposed system will be more accurate and useful in this manner.

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Post    Posted on: Sun May 21, 2006 9:10 am
Hello, alistair,

as I understood the news and articles about DART it wasn't GPS itself which caused oor lead to errors but the software using the GPS.

If that's correct GPS still can be assumed to work regarding Sean Girling's idea.



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Post    Posted on: Tue May 23, 2006 7:08 pm
Ekkehard Augustin wrote:
Hello, alistair,

as I understood the news and articles about DART it wasn't GPS itself which caused oor lead to errors but the software using the GPS.

If that's correct GPS still can be assumed to work regarding Sean Girling's idea.


True. My office has request the formal mishap report. There is a fair amount of restricted data, so it might be slow coming. Hopefully I can read that over the next month or so (too many other things going on to sit down and get through it in one go).

I believe you are correct in as much as the GPS unit was operating correctly, but something to do with the interface of the unit with other parts of the system caused the problem.

Still GPS is only useful for LEO satellites and some other satellites in the lower part of MEO. Galileo going up will increase the potential for more MEO satellites using a navigation signal. Even GPS satellites will be able to use the Galileo signals.

MEO will be getting crowded over the next few years. Hopefully integrated upper stages will be the norm and thus result in less junk. I'm not too confident in the Russians and their ho-hum method of satellite disposal in MEO (they live them in place).

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Post    Posted on: Wed May 24, 2006 4:30 am
I'm not sure an ion drive is the way to go. The thrust is so low it might take months to collect each piece of junk. Maybe a VASIMR? That way you can step up the thrust level for short term close manouvering.

The market for space junk in orbit won't appear until we have commercial manufacturing in orbit or on the moon. The cost, after collection, of de-orbiting this stuff to a soft landing, would not be very high though.


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Post    Posted on: Wed May 24, 2006 8:04 am
It will be no problem to improve GPS by installing GPS-satellites in higher orbits - this GPS could be focussed on space purposes then. Another aspect would be if the clumping satellites would go ahead or follow a larger object - then the position of this larger object only needs to be known precisely while the positions of the clumped satellites could be measured relative to that object by instruments of the object and the clumped satellites which should form a network including such measurements.

The space debris/junk market already is germing I think. First agencies already have started to call for rocket stages etc. being flown to a parking orbit. Second insurances and satellite owners already have started to call for higher safety since insurance rates etc. are going to be increased if the risks aren't reduced.

This means that there is a market to avoid and to remove debris/junk. This will be paid for if a company offers the service. Then the debris/junk could be stored somewhere in orbit without giving up any actual profit - the costs of the storage will be less than the profit gained by removal etc.

The best location to do the removal is around working and expensive satellites...



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