ESA Says Space Junk Must Be Removed

[lawrocket 3]

I was reading an article about this. It says that there are an estimated 29,000 objects of larger than 4 inches in earth orbit right now at an average orbital velocity of 15,500 mph. Sounds pretty bad, doesn't it?

That's where I come in to help paint a picture of what 29,000 4 inch items means in terms of what the statistical differences are.

Let's imagine 29000 objects randomly spaced throughout the earth. For that we must know earth's surface area (I'll act as though there are no valleys or mountains and take the average radius of earth since it is flatter at the poles) by getting an average radius of 3,956.52 miles from core to surface.

Formula for surface area of a Sphere: 4*pi*r^2
4(pi)(3956.52^2)
4(pi)(15,654,050.5)
The surface area of an earth-sized spehere is 196,714,600.2 million square miles. If 29,000 pieces of space junk were placed on the 2 dimensional earth surface we'd average one piece every 6,783 square miles.

But space is considered up there so add 60 miles to radius
4016.52^2 = 16132432.9104
4(pi)( 16132432.9104) = 202,726,130.86 million square miles of surface area of space boundary

But let's go to a more useful altitude of 250 miles, around where the ISS likes to be.
Radius = 4206.52 miles
4206.52^2 = 17694810.51
4(pi)( 17694810.51) = 222,359,546.82 square miles

Now assume 29,000 catalogued items over 4 inches at 250 miles altitude: 222,359,546.82/29,000 = 1 object every 7,667.57 square miles. That means roughly one item in an area 50 miles by 150 miles. But since most space debris is between 2/3 of the earth’s latitudes, let's reckon one object every 5,112 square miles, or roughly one in a 50x100 mile area. So let’s take a big square place like Wyoming – about 98,000 square miles and it averages out to 19 objects of 4 inches or larger randomly in Wyoming at any point. Even on two dimensions (note - almost all traveling in a west-east azimuth) the odds of them actually colliding are tiny.

This still overstates the risk.  Consider it like 19 planes all flying at a random altitudes up to 22000 miles.  What are the odds of them actually colliding when just the vertical spacing is averaging a little more than 1 every mile? Yes, there are many satellites in geosynchronous/geostationary orbits that skew the average altitude up to 1250 miles.

There’s the space-junk risk in some basic math. 29000 objects is a lot in raw number. But when you ask, "what is the risk of a collision between items traveling in a direction between 0 and 180 degreees, spaced out by an average in excess of 5000 square miles at random altitudes, doesn't the risk seem quite low?

Again, the exception is geostationary orbit where they are all at the altitude of 22,236 miles directly over the equator (and generally clustered). A collision there certainly would cause a very bad day, which would cause chain reactions making geosynchronous orbits unusable for the next 50,000 years.

Also note: the vast distances between these objects makes cleanup that much more difficult and would probably cause more junk than it picks up. How can a cleanup be effectuated?

My wife is hotter than your wife.

[wmw999 2,602]

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Also note: the vast distances between these objects makes cleanup that much more difficult and would probably cause more junk than it picks up. How can a cleanup be effectuated?

It's not really possible now, but the ocean used to be really, really big too -- and now there's enough trash for us to talk about it.

Maybe starting the discussion when it's impossible will bring some ideas to the forefront, or at least get people to consider what's left behind in planning space activities.

Wendy P.

There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown)

[kelpdiver 2]

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So let’s take a big square place like Wyoming – about 98,000 square miles and it averages out to 19 objects of 4 inches or larger randomly in Wyoming at any point. Even on two dimensions (note - almost all traveling in a west-east azimuth) the odds of them actually colliding are tiny.

I think where your examples understate the concern is that the good spacecraft is crossing Wyoming every 90 seconds. So you're taking that very low probability and multiplying it by a large number of exposure changes.

The amount of debris is significant enough that it factors into launch windows.

[lawrocket 3]

I have no problem with talking about it. Indeed, it's been a significant issue for at least the last 30-40 years. It's why such vehicles at the Delta are designed to vent unused fuel to prevent explosive "venting." We've taken steps with regard to orbital missions to shed as much before orbital velocity.

I've followed a lot of this stuff for a while. The Kessler function, I think it is, were impacts become chain reactions. I do think the rest of the world is catching on. But I do dislike the "tipping point" talk. It's why I did the math this morning - the "space debris" maps showing the earth behind a cloud aren't really a good representation of how it is.

It's good to think about it. But I think it requires a treaty to discuss particulars.

My wife is hotter than your wife.

[regulator 0]

So any ideas on the approximate diameter of said objects..and wouldnt they burn up in the atmosphere if they fell out of orbit?

[BillyVance 35]

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So any ideas on the approximate diameter of said objects..and wouldnt they burn up in the atmosphere if they fell out of orbit?

Probably 99% of all space junk would burn up without any significant pieces reaching the surface. I could be a few percentage points off. And I'm not talking specifically about the 4" and smaller stuff.

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[BillyVance 35]

FWIW I do remember when Skylab (the first space station) made its return to earth, probably also the first space object that had pieces survive reentry, other than reusable rocket parts and manned modules.

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[normiss 906]

Who is ESA?

I'm too lazy to search.

[champu 1]

I appreciate what you're trying to do, but your approach to this is flawed.

Satellites (both useful ones and junk) are not spread out all over the place going every which way, they are in orbits. Two objects in stable orbits with different elements but that overlap in altitude will eventually cross paths. In most cases, "big space" theory prevails because for most orbital planes, there's only one or a few things in that plane, and so the chances of the two objects being phased correctly when their paths cross is very low...

However...

A sizable percentage (probably around 10%) of those 29,000 objects you're talking about are in just a couple of orbital planes. Those planes correspond to the Chinese ASAT test in 2007 and the Iridium-Kosmos conjunction in 2009.

So it's less like wandering around Wyoming and more like running intersections without stopping because, "eh, the streets aren't that busy" ...except that there are two streets that are actually quite busy.

[BillyVance 35]

I do have to wonder.... What happens to the I.S.S. when it has outlived its usability and is abandoned? That's one BIG sumbitch! If left intact and allowed to drop closer to earth via gravity and make reentry (wouldn't happen for decades anyway), that would make for a spectacular show!

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[BillyVance 35]

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Who is ESA?

I'm too lazy to search.

European Space Agency, you slack ass slug.

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[GeorgiaDon 385]

You are downplaying the time element, though, when you portray the situation as "19 objects in Wyoming". Satellites and space stations are intended to function for a decade or more, so events that are low probability to happen today become quite a bit more likely if you say "some time in the next 10 years". Also, "risk" is some combination of probability of an event and consequences if the event happens; low probability events can still be risky if the consequences are catastrophic, just as events that are likely to occur but have only minor consequences are not perceived as risky. Collisions have in fact occurred, and the space station has been moved to reduce risk of a collision, so the probability of it happening is not 0 even if it is low. A collision with the space station could well be catastrophic. Clearly no need to panic yet, but still the prudent course would be to avoid adding to the problem as much as possible.

I've seen discussions of using a laser to target the larger objects. Obviously you don't want to cause them to break up, but if you can perturb their orbit so they dip down toward the upper fringes of the atmosphere for part of the orbit, eventually they'll reenter and burn up.

Don

_____________________________________
Tolerance is the cost we must pay for our adventure in liberty. (Dworkin, 1996)
“Education is not filling a bucket, but lighting a fire.” (Yeats)

[normiss 906]

Europeans in SPACE???
OMG.
Where's my tin foil?

[lawrocket 3]

Not really. It's stuff traveling around the planet - I just narrowed the area to a size of wyoming to give some perspective of size.

The velocity DOES relate to the energy released in a collision. (Mass time Velocity^2).

My wife is hotter than your wife.

[champu 1]

You can do a search for "Mir Deorbit" or "Columbia Disaster" or "Hayabusa Reentry" to get an idea of what a massive spacecraft doing an uncontrolled reentry looks like.

ISS is a few times more massive than Mir was.

[lawrocket 3]

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So any ideas on the approximate diameter of said objects..and wouldnt they burn up in the atmosphere if they fell out of orbit?

The atmosphere has been the only thing that has cleaned up space. Sucking stuff up.

Regarding the ISS issue brought up - I reckon they will attempt to deorbit it so that whatever is ultimately left of it ends up in the Pacific. The Skylab came down on its own - in part thanks to delays with the Space Shuttle.

My wife is hotter than your wife.

[GeorgiaDon 385]

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FWIW I do remember when Skylab (the first space station) made its return to earth, probably also the first space object that had pieces survive reentry...

A Russian nuclear powered satellite reentered over northern Canada before that. Debris was scattered over 48,000 square miles; 12 large fragments, all but 2 radioactive and at least a few emitting potentially lethal levels of radioactivity, were eventually recovered. My father headed up the Canadian recovery team.

Don

_____________________________________
Tolerance is the cost we must pay for our adventure in liberty. (Dworkin, 1996)
“Education is not filling a bucket, but lighting a fire.” (Yeats)

[turtlespeed 226]

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So any ideas on the approximate diameter of said objects..and wouldnt they burn up in the atmosphere if they fell out of orbit?

The atmosphere has been the only thing that has cleaned up space. Sucking stuff up.

Regarding the ISS issue brought up - I reckon they will attempt to deorbit it so that whatever is ultimately left of it ends up in the Pacific. The Skylab came down on its own - in part thanks to delays with the Space Shuttle.

The atmosphere is only a part of it, Gravity and Friction did most of the work, the atmosphere was just there warming the planet.

I'm not usually into the whole 3-way thing, but you got me a little excited with that. - Skymama
BTR #1 / OTB^5 Official #2 / Hellfish #408 / VSCR #108/Tortuga/Orfun

[quade 4]

The problem is your "math" doesn't match up with reality. There already have been several fairly famous collisions and each one adds significantly more risk to more happening like a chain reaction.

quade -
The World's Most Boring Skydiver

[billvon 3,132]

>Consider it like 19 planes all flying at a random altitudes up to 22000 miles. What are
>the odds of them actually colliding when just the vertical spacing is averaging a little
>more than 1 every mile?

Consider it like 19 parachutes all opening at random altitudes up to 12,000 feet, and all spaced over 2 miles of jump run. What are the odds of them colliding? Heck, how could it ever happen? The odds are a billion to one.

Such collisions DO happen, of course, because 1) everyone is aiming for the same place to land and 2) they tend to open at similar altitudes for other reasons (like maximizing freefall times.)

Same thing happens with aviation. There are about 10,000 aircraft in the air at any given time, at altitudes from 0 to 40,000 feet, all over the planet. The odds of them ever hitting at random must be billions to one! The gotcha is, of course, that they all want to land at a small number of airports, and they all follow similar paths to get there. Which is why there are midair collisions even with those odds, and even with technology deployed specifically to prevent them.

And the same problem arises with space debris. If it were truly spaced randomly it would be much less of a problem. But orbital mechanics dictates that when an upper stage separates, all the junk that falls off (restraining bands, pyrotechnic bolt heads, payload fairings etc) are either going to burn up or stay in low Earth orbit. No one wants to boost an extra 200 pounds of useless junk to geosynchronous orbit, so it's all jettisoned as early as possible. Which means if it stays in orbit it's going to be a low one.

Then there's the problem of where they are going. There are a few very useful orbits, like the geosync orbits. That's where everyone wants to be. So all the satellites that end up there are in a very narrow band, and when something bad happens (loss of control, collision with something etc) most of that debris is going to stay right there where everyone else wants to be.

> it averages out to 19 objects of 4 inches or larger randomly in Wyoming at any point.

OK let's go with that.

Now imagine Wyoming with a fair number of important things (call them people) in it. They don't want to get hit by any of that debris, since it's moving at 15,000 miles per hour. Any such collision would vaporize them. And they never stop moving. And there is nowhere you can go that is truly safe; nothing you can hide behind. And since they are moving that fast they cover a lot of ground; if the "danger zone" is 16 inches (the width of a person) then the danger zone posed by even one of those objects is (1.3 ft X 15,000 mph x 5280) = 4 sq mi an hour, or 89 sq mi a day. With 19 it's 1684 sq mi a day. With Wyoming's area that means you have a 1.7% chance of being hit on any given day.

Are you OK with those odds for one day? Perhaps. For a week? A year?

And that's the big objects. There are a lot more of the smaller ones that will also kill you; they're just harder to see.

You might be lucky enough to have a tracking system that would send alerts to your cellphone so you could move. It would be annoying, surely, to periodically wake up in the middle of the night and move two feet to avoid being vaporized, but is probably doable. But after a while you'd also probably start to want people to remove all that damn junk that's whizzing around all the time. Especially if it's not your junk.

[BillyVance 35]

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FWIW I do remember when Skylab (the first space station) made its return to earth, probably also the first space object that had pieces survive reentry...

A Russian nuclear powered satellite reentered over northern Canada before that. Debris was scattered over 48,000 square miles; 12 large fragments, all but 2 radioactive and at least a few emitting potentially lethal levels of radioactivity, were eventually recovered. My father headed up the Canadian recovery team.

Don

Cool, I didn't know that.

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[JackC1 0]

Not only are there corridors of "useful" orbit that most of the junk gets dumped into, but due to the gravitational variations of the planet's field there are also orbital hotspots where junk tends to want to migrate to. Unfortunately, as the junk gets sucked into these gravitational wells, the motion isn't damped so it passes too and fro like a pendulum, until it meets something to collide with.

Science is rarely as simple as you might want to think.

http://www.bbc.co.uk/news/science-environment-12911806

[Andy9o8 3]

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Science is rarely as simple as you might want to think.

That's why we have Intelligent Design.

[normiss 906]

[lawrocket 3]

I'm impressed with everyone's input. Got me thinking a bit more deeply. Kinda why I put this out there.

My wife is hotter than your wife.