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Zvezdichko
2009-Feb-19, 07:22 PM
I'm still wondering.

I have read tons of publications on Roscosmos.ru, several other Russian websites, some international websites. Opinions vary from: "Don't worry, space is big", to "One day it will be impossible for us to explore space".

My question is: Is this really a threat or a false alarm?

We have the atmosphere, which is cleaning the low earth orbit constantly. It will take several years to clear all orbital debris up to 300-400 km.

I'd like to see a serious discussion.

NEOWatcher
2009-Feb-19, 07:46 PM
I have read tons of publications on Roscosmos.ru, several other Russian websites, some international websites. Opinions vary from: "Don't worry, space is big", to "One day it will be impossible for us to explore space".
In a way, both sides are right.
Space is big, and it doesn't take a lot to avoid what's there.
But; one day it may be impossible because the fragments will be more plentiful, and smaller making them harder to track and avoid.

The risk is huge.


My question is: Is this really a threat or a false alarm?
It's a threat of things to come if not resolved. Since we have no way of cleaning it up at the moment, it can only get worse.


We have the atmosphere, which is cleaning the low earth orbit constantly. It will take several years to clear all orbital debris up to 300-400 km.
But the problem extends much farther than that.
See the wiki page (http://en.wikipedia.org/wiki/Space_debris) for the distribution of debris.
And here's a graph that I found (http://books.nap.edu/openbook.php?record_id=4765&page=29#p200063399960029001) of orbital decay, or lifetime... (thousands of years for higher ones)

Zvezdichko
2009-Feb-19, 07:53 PM
But the problem extends much farther than that.
See the wiki page (http://en.wikipedia.org/wiki/Space_debris) for the distribution of debris.
And here's a graph that I found (http://books.nap.edu/openbook.php?record_id=4765&page=29#p200063399960029001) of orbital decay, or lifetime... (thousands of years for higher ones)

So, for LEO stations like Skylab, everything will be cleaned after several years.

But it will take decades to clean the sky higher than 500 km...

EDG
2009-Feb-19, 07:54 PM
I'd argue that we should be looking at having a (manned or unmanned) orbital cleanup capability instead of wasting money on funding manned missions to other planets. There will come a time when debris will cause a calamity up there (be it to a suborbital flight, space shuttle, space station, telescope, or satellite) - the recent impact between a Kosmos and Iridium satellite has produced a LOT of fragments. Either way, something worth a lot of money just got destroyed by what essentially was a bit of junk that shouldn't have been up there.

If you've seen the anime "Planetes" then you know what I'm talking about - we need a "Debris Section" to divert the dangerous fragments and bits up there, preferably within the next couple of decades.

Larry Jacks
2009-Feb-19, 08:02 PM
Last week's satellite collision took place almost 500 miles high. Early reports indicated over 600 pieces large enough to track with the Space Surveillance Network (SSN) but I suspect the number will be far higher once the pieces disperse some more. At that altitude, a lot of the pieces will be in orbit for decades to perhaps over 100 years. The Chinese ASAT test in 2007 was also near that altitude. Over a period of a few months, some 2500 SSN trackable pieces were cataloged.

The SSN can track objects down to perhaps the size of a baseball (about 10 cm). Impact models predict the actual number of pieces from the Chinese ASAT test alone could've easily exceeded 100,000, it's just most are too small for the SSN to reliably track.

The energy of an impact depends on the object's mass and the relative velocity between it and another object. A simple piece of debris, say 1 cubic centimeter with a mass of a few grams, can hit with the impact of a cannon shell if the relative velocity is high enough. That can do a lot of damage and cause more debris.

The official satellite catalog of man-made objects in space already keeps track of some 19,000 objects. These range in size from the smallest objects the SSN can reliably track to the ISS. These objects can be an active satellite, a dead satellite, spent rocket bodies, or simple pieces of debris. In the next few years, the military is hoping to field an S-band multistatic radar fence that will be able to detect much smaller objects. It's predicted that the catalog will rapidly grow to more than 100,000 objects once that system is on line. Still, there will be countless pieces even smaller than the new system can detect in orbit.

Even a small piece of debris can do damage. On more than one Shuttle mission, a windshield was impacted by a small piece of debris likely no bigger than a paint chip. The windshields were damaged enough that they had to be replaced. Imagine what would've happened had the piece been 1-2 cm instead of a paint chip.

When NASA was designing the ISS, they sponsored studies to try and measure 1 cm objects in space using the HAX radar. Using that data, they realized that over a period of years, the ISS was certain to be struck by 1 cm and smaller pieces multiple times. As a result, they designed the ISS to withstand such impacts. Most satellites lack any protection so they're vulnerable.

Zvezdichko
2009-Feb-19, 08:35 PM
Oh... No, no... I meant something different...

This topic has been discussed in the past. But when I did the search for "Kessler", the search engine of the forum gave me only several results. Do you think we are nearing the Kessler syndrome?

Yukmay
2009-Feb-20, 01:45 PM
I personally have no idea how much debris it takes for us to reach Kessler-syndrome. However we're definitely on our way.

I guess all it would take is X number of satellite collisions which seems to still be highly unlikely. However if there was some sort of a political-uproar and some more SATs get blown up this could quickly change.

JustAFriend
2009-Feb-20, 02:18 PM
And its not so much the big stuff.... platforms, sats and other big objects can be easily tracked. But those bolts, pens, tools, debris and little stuff that are the real worry.

Ignoring it all now would be like saying in the 1930s, "There aren't that many airplanes in the sky now.... lets not bother putting up expensive air-traffic towers at the airports to direct them and keep some control over the situation."

If we're going to (hopefully) become a space-faring race we just need to do some planning and take control of the situation now....

samkent
2009-Feb-20, 07:35 PM
Dealing with dead satellites is almost a non issue. Once they get to high enough numbers joint efforts to de orbit them will be under taken. An ion thruster craft attaching a long wire to dead satellites comes to mind.
It’s the smaller debris from collisions and clumsy astronauts. There I like a large aerogel or foam blob orbiting where it will take the most hits.
Which orbit would do the most good? Lo inclination or hi or polar?

publiusr
2009-Feb-20, 07:40 PM
I might launch an aerogel blob from Israel. There you would be running into debris at a faster rate going westbound. A Sea Launch might put something large enough with enough mass to clear debris out in a hurry.

Argos
2009-Feb-20, 08:27 PM
There I like a large aerogel or foam blob orbiting where it will take the most hits.

So you want more debris in orbit? :)

samkent
2009-Feb-20, 08:44 PM
So you want more debris in orbit?

One big blob collecting thousands of pea sized crud, absolutely!
Even if the debris punches through the blob it will slow it down.
It’s like a Roomba. It may not be fast or thorough but it will do a darned nice job with no human input.

cjameshuff
2009-Feb-20, 09:09 PM
Or blow a big ball of very-low-density foam composed of some material that slowly evaporates in vacuum...similar plastics have been developed for other purposes (delicate structures that can't withstand launch without support). Small fragments that get knocked off will evaporate more quickly, and not make the debris problem worse. Debris that punches through will lose velocity and drop into a faster-decaying orbit. Debris that gets trapped deorbits with the foam-ball, more quickly than otherwise due to the higher drag for its mass. In the meantime, it's stuck in a single easily-avoided object.