CubeSats and Huge Amounts of Un-Trackable Space Junk

Traveling at orbital speeds up to 17,000 miles an hour, even an aluminum pellet 1-centimeter wide packs the kinetic equivalent of a 400-pound safe moving at 60 miles an hour.

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Cubes usually only last a couple of years; low orbit and low mass/surface ratio. So they wash out.

Someone conjectured that bigger, higher-orbit satellites could one day explode into a fragmentation crisis, where everything starts knocking pieces off everything else. That would look spectacular.

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John Larkin         Highland Technology, Inc 

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John Larkin

A Wall Street Journal subscription is required to read the article.

Hmmm... Since the surface of the earth is 510*10^12 square meters, there are 500,000 pieces of space junk in orbit, and you occupy a target area of about 1 square meter, the chances of you getting flattened by falling space junk is 1 in 1*10^9. I suggest that you purchase and wear a safety helmet.

Incidentally, the odds of getting hit are much higher if you move to the spacecraft cemetery:

Orbital Debris Program Office:

For the latest disaster news, there's the quarterly news:

We already have a garbage dump site in space:

Space junk visualization: Try clicking on "groups" to the right of the search box and then zoom out. "Iridium 33 collision debris" is interesting and rather messy:

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

I think that was for the geostationary orbital belt, where all the satellites are the same distance from the surface of the earth and are concentrated over the equator. They therefore have the possibility of running into each other. While that seems like a large number of satellites in close proximity, the 2 degree orbital slots are 73km apart: Many operators cram more satellites into a single orbital slot seperated by much smaller distances: As the geosynchronous belt becomes more crowded, chances of collisions incease. Although there are theoretically 1800 available places to part a satellite, only 402 are currently occupied.

However, there is the possibility that something will arrive and decide to play billiards with the satellites. Chances of getting the cue stick perfectly aligned to create a dominoes-like effect is almost impossible, but it's fun to speculate on the possibility and its after effects.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Jeff Liebermann wrote on 12/22/2017 9:14 PM:

I thought those two numbers couldn't go together and it seems you have some data confusion:

"Note that some of these satellites are separated from each other by as little as one tenth of a degree longitude. While that may seem like very little separation, and it is, at geosynchronous altitude (nearly 36,000 km), this corresponds to an inter-satellite spacing of approximately 73 km."

So 73 km corresponds to 0.1 degrees of separation. I believe elsewhere I saw that 2 degrees is closer to 1000 km although that would be 1460 km if the first numbers are accurate. Oh well...

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rickman

Jeff Liebermann wrote on 12/22/2017 8:47 PM:

But there are some 7*10^9 people on earth, so the odds are around 7 people will be killed by space junk when it all comes down?

I recall reading about and seeing a simulation of two sats colliding. What was the chance of that happening? How likely is it to happen again anytime soon?

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rickman

A Gigundus kevlar umbrella on the nose to clear a path...

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David Lesher

That is correct. For 2 degrees of separation it is more like 1460km.

Also, note that two satellites that are in the same orbit are not going to hit eachother at 17,000 miles an hour. That privilege is reserved to objects in DIFFERENT orbits, e.g. in low earth orbit at different inclination. Satellites in geostationary orbit remain at roughly the same distance, and when there is a small inclination of the orbit they could potentially hit eachother but not at 17,000 miles an hour. When the mean motion of the orbit changes (the rate at which it orbits the earth), so does the diameter of the orbit, and that would make the satellites miss eachother when they approach.

The only way to cause collisions in geostatonary orbit is to launch a satellite in reverse direction (which of course will never happen) or in an orbit with wildly different inclination or eccentricity that crosses the geostationary orbit in 2 places. But the density of satellites in geostationary orbit is very low, it will not be an obvious target that you are going to hit for sure.

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Rob

The upside is all that junk may inadvertently deflect that extinction event asteroid hurtling towards Earth at 140,000 MPH.

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bloggs.fredbloggs.fred

It could happen if a thruster misfires during orbital insertion. It's unlikely but it might only have to happen once. A particular slot used by a particular country would be affected sooner, and take longer for the cloud of fragments to spread around the orbit.

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Tom Del Rosso

Oops.

I just hate it when I screwup that badly. I grabbed the 73km number from a Google search without reading much of the article or doing a sanity check. Earth radius = 6370km. Geosync belt altitude = 35,786km Total radius = 6370 + 35,786 = 42,138km The length of a 2 degree chord is: 2 * radius * sin(2deg/2) = 2 * 42,138 * 0.0175 = 1470km

Thanks for the correction.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Can you describe how that would work? Do you envision an orbit that is circular and at the correct altitude but with a high inclination?

Or an elliptical orbit with zero inclination but a much higher apogee?

How do you rate the probability that it would hit something while crossing the geostationary belt before its orbit would perturb enough to not be crossing the belt anymore?

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Rob

Tthe projected crisis was for lower orbits, where closing velocities are insane and there are millions of objects in orbits that intersect.

One optimal collision could start a cascade of disintegration.

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John Larkin

It wouldn't require a "much" higher apogee. One possibility is a slightly eliptical orbit with an apogee at the correct altitude. I did say "unlikely", but it might only have to happen once.

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Tom Del Rosso

There was once a 1cm deep crater in a window of the space shuttle that was created by a paint chip something like 0.1mm wide.

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Tom Del Rosso

When there is "not much" difference in orbit there will also be "not much" difference in speed. Certainly not the 17.000 mph that was mentioned further up in the thread. Those numbers are valid for low-earth orbits of completely different inclination only.

It would still damage the spacecraft beyond usability but there is much less chance of smattering it into small pieces and causing an avalanche effect.

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Rob

Really? I've seen cars nearly explode in a 50 mph impact. In orbit a satellite doesn't need a huge hit to scatter debris which can then cascade.

I wonder if that is how the rings of Saturn developed, from a set of alien created satellites where just one went wonky and creamed all the others? Over time the collisions continued until they destroyed a moon or two and scattered rocky debris.

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Rick C 

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rickman

I think it is more like the opposite: the debris in the rings failed to lump together into larger moons because the gravity field of the many other small moons kept the pieces distributed and swept clear areas between them.

There are no (violent) collisions between objects orbiting that way, as is demonstrated by the rings of Saturn being "stable". Would there be another set of rings at a different inclination, the situation would be completely different.

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Rob

I still say it's aliens... all the way down.

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Rick C 

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rickman

But if a control failure led to that situation it could stay in that orbit, and then it's inevitable because its speed would be a little different. After a collision both would have a small change in speed, and then....

Still unlikely, but some have failed. They just have to fail in the right way.

One small piece of debris can damage it beyond usability, but the whole thing could scatter the solar panels. A paint chip almost killed a shuttle crew once.

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Tom Del Rosso

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