More space debris

[scottb50]

Your right, I meant to say the ball would land first. <div class="Discussion_UserSignature"> </div>

 

[j05h]

<i>>Your right, I meant to say the ball would land first.</i><br /><br />On the Moon the feather and the ball/hammer land at the same time. Local gravity accelerates objects (acts upon them) at the same rate. Check out how slowly they fall in 1/6 G. The tenuous atmosphere on the Moon has a negligible effect on the experiment:<br /><br />http://youtube.com/watch?v=dHzVsLAhUCA <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[comga]

One concept for reducing space debris:<br /><br />Bring a Shuttle External Tank all the way to orbit and leave it there. Debris hitting it would penetrate the tanks. The resulting debris would be of minuscule size or vaporized. They would not puncture the opposite side of the tank. The debris would be captured. The ET, having large mass but enormous mass, and being left in a very low orbit, would decay over a short time, days to months.<br /><br />An experimental package of microphones attached to the tank structure could return information on the distribution of debris, and produce frequency vs impact energy data.<br /><br />The downside: Reduced Shuttle payload and an uncontrolled reentry of the massive ET. As all but one of the remaining Shuttle flights are going to an ISS orbit (51 degree inclination?) that would fly over most of the inhabited surface of the world. <br /><br />If the ET tanks are sealed after being jetisioned (Do they?) there would also have to be a way to depressurize the tanks to avoid it exploding like so many upper stages that have created so much of the debris we are discussing.

 

[comga]

bobblebob: Do the new satellites have a time limit from when they are non-operational to when they have to burn up upon reentry?<br /><br />NASA rules state that new satellites going to orbits with lifetimes of more than 25 years (IIRC) need to include a mechanism to deobit themselves. In general, that means either additional fuel or an added rocket of some sort. This lifetime is equivalent to an altitude of about 500km (also IIRC) depending on the mass to area ratio (aka the ballistic coefficient.)

 

[henryhallam]

Does NASA have the authority to make those rules for everyone? Or do they only apply to NASA satellites?

 

[bobblebob]

Just their own i would think. Nasa dont own space or what goes into space. Each agency will set their own rules (although it would be benifically to everyone to come up with common rules)

 

[samkent]

How about a LARGE can of 'Great Stuff' at several different altitudes in polar orbit. A lot of volume for little mass. Debris hitting the foam will slow or even imbed (if small enough). After a period of a few years much of the smaller debris should have hit the foam balls at least once. Keeping track of the balls should not be an issue either.

 

[bdewoody]

Wasn't there a time when they were considering taking the ET's all the way to orbit and modifying them for use as part of the ISS? <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[MeteorWayne]

Only here on SDC <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[scottb50]

I would think the foam would be one of the major reasons. The thing would look like Pig Pen in the Charley Brown cartoons after a few years with a cloud of debris all around it. <div class="Discussion_UserSignature"> </div>

 

[comga]

henreyhallam is correct. NASA can only make rules for its own satellites. This restriction was in place for the NASA ESSP AO a few years ago and is presumed to be a requirement for other Earth orbit NASA missions.

 

[comga]

"The ETs would cover an in significant volume of LEO and thus would be ineffective collecting small debris in LEO."<br /><br />Of course. (ET ~400 m^2 Equatorial LEO 200 to 1000 km high ~4E15 m^2) This is not serious. It wouldn't really clean LEO. As said elsewhere recently, "We can discuss using vacuum cleaners in a vacuum elsewhere."<br /><br />One ET might be a good way to sample the debris distribution, however. Current technology cannot detect debris smaller than 10cm IIRC. But it doesn't matter much because there is no way this would even be considered.

 

[MeteorWayne]

"One ET might be a good way to sample the debris distribution, however. Current technology cannot detect debris smaller than 10cm IIRC. But it doesn't matter much because there is no way this would even be considered."<br /><br />True, but it also could contribute to the problem if it is hit by something <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[comga]

"True, but it (an orbiting ET) also could contribute to the problem if it is hit by something "<br /><br />No. Read the original post. It would act like a Whipple shield, like an orbital Roach Motel. Debris punch in, but they don't punch out the other side. <br /><br />And like SG said, with its large area it would quickly decay out of orbit. So do most objects with low perigees. That's why the Chinese test was so polluting. The target was pretty high, so many of the debris have decades or centuries long decay times.

 

[comga]

"Not if the high velocity hit was from a large object, say a upper stage."<br /><br />Weren't you the one discussing probabilities? Collisions with large objects are less frequent than with small debris, especially for the short orbital lifetime of a low density ET, as you also pointed out.

 

[cello]

"The ET has a low density and large surface area thus it's orbit would decay very quickly."<br /><br />How long after et sep, et burns on re-rentry? average? quickest? longest?<br />I understand, it depends on orbital parameters at sep, but anyway. What are numbers?<br />Also, is there big difference (how long after) on typical "go to iss" mission, or for example, hubble repair?

 

[itsfullofstars]

Lets add another large piece to the list:<br /><br />SKorea loses contact with first satellite: official<br /><br />http://www.spacemart.com/reports/SKorea_loses_contact_with_first_satellite_official_999.html<br /><br />They lost contact with it on Dec 30th 'lost contact' doesn’t tell you if it is in one piece either. Although eight years on orbit is about the right time for a basic mechanical failure.<br /><br />I do agree with you tho shuttle_guy the actual launch itself is probably a bigger problem than the end of a satellites life. Unless the Chinese come along and blow it into 35,000 pieces. <br /><br />Casting my mind back, every rocket cam I have watched that shows separation also shows hundreds of pieces of junk of varying sizes splintering out from between the stages, fractured rings, splinters of metal, paint etc etc.<br />

 

[comga]

"every rocket cam I have watched that shows separation also shows hundreds of pieces of junk of varying sizes splintering out "<br /><br />None of those make it to orbit. It is possible to keep the part that does make orbit from shedding parts and debris, and to de-orbit spent stages. It just takes discipline and money, and costs a bit of performance. A system on which I am currently working spent a good deal of time and effort (=$$) on a door instead of a disposable "lens cap" so we don't leave a large (and radar-invisible) piece of debris in orbit.

 

[cello]

"The orbit is targeted for q re-entry into the Pacific Ocean."<br /><br />Ok. Does ET burns up completely before reaching surface, or there is same wreckage down in the ocean?

 

[itsfullofstars]

Thanks for the reply Comga, thats nice to know.

 

[comga]

"That is not true for upper stages where the upperstage and satellite are in orbit"<br /><br />Obviously correct, but this is unrelated to the clouds of debris seen in Rocketcam footage of launches. The highest Rocketcam I can recall is the ET separating from the Shuttle, and even that is sub-orbital. <br /><br />The SpaceX launch *could" have shown a rear view from orbit, had it not fallen back into the ocean. If you watch that video, after the Krestel sheds the bell stiffeners, nothing comes off. <br /><br />A rocket that gets to orbit can still make a mess if there is a screw-up, but it can be totally clean, controling all of the hardware and deorbiting in one or two pieces.

 

[itsfullofstars]

This is a Delta IV heavy inaugural flight 21 December 2004. It shows all stages of the launch and each stage clearly shows lots of debris, even at the satellite separation.<br /><br />www.eclipticenterprises.com/video/delta4-heavy-mpeg-hi.mpg<br /><br />Quick question S_G, at what stage are we on orbit? Is the fairing separation on orbit? If so how long before they fall back?<br /><br /><br />Thanks.

 

[willpittenger]

Look out below. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[billslugg]

Post deleted by billslugg <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[comga]

Thanks for the link. This was neat to watch (after I corrected the URL).<br /><br />You are correct. You do see a cloud of debris at the separation of the microsat, which was *supposed* to be in orbit. But you have to consider what constitutes this stuff. There is no obvious hardware. No bolts or brackets. It looks like frost, not solid materials. This will dissipate rapidly.<br /><br />