9 Ideas For Coping With Space Junk

An anonymous reader writes "The space age has filled Earth's orbit with all manner of space junk, from spent rocket stages to frozen bags of astronaut urine, and the problem keeps getting worse. NASA's orbital debris experts estimate that there are currently about 19,000 pieces of space junk that are larger than 10 centimeters, and about 500,000 slightly smaller objects. Researchers and space companies are plotting ways to clean up the mess, and a new photo gallery from Discover Magazine highlights some of the proposals. They range from the cool & doable, like equipping every satellite with a high-tech kite tail for deployment once the satellite is defunct, to the cool & unlikely, like lasers in space."

Comments

Hit or Miss

[teeks99]

That Discover article was pretty hit-or-miss. They nailed the real solution in two of their pieces (tethers and sails), in that the best (easiest, cheapest, only-one-that-will-probably-ever-happen) are technologies that are built into space objects (satellites and boosters) before launch. There's lots of options here from tethers, sails, balloons, or just using existing thrusters. If we can stop leaving big pieces up there (which can run into other big pieces and make LOTS of pieces), the problem will start getting less severe.

On the other hand, on of Discover's pages was about blowing up the debris...this makes sense, until you really think about it. The problem is that when you blow up something, it makes a huge number of new pieces, with all sorts of different velocities and orbits. On average, these pieces will fall to earth more quickly than the unexploded satellite, however, that's just the average. There are many pieces that will stay up there even longer. And when you're talking about things moving that these incredible velocities, it doesn't matter a whole lot if you get hit by a 6,000lb. satellite or a 5lb. piece of a satellite, either one will destroy anything we've put in orbit.

Re:Hit or Miss

[BJ_Covert_Action]

That Discovery article was a total waste of time. It really had little to do with "9 ways of dealing with space junk," and was more along the lines of "9 things that are kind of related that we want to talk about." As you mentioned, a couple of its nine methods of dealing with space junk could really just be grouped into the general theme of, stop putting more up there (deorbit your crap at end of mission). There were only three methods that actually discussed getting rid of existing junk: lasers in space, balls of aerogel to capture stuff, blowing up large chunks of junk. For what it's worth, the exploding method that you mentioned discussed only conducitng such methods at low altitudes which actually does work really well. However, it still leaves a lot of unaddressed crud in the higher LEO bands (like the one the ISS is in). The aerogel glob discussion was also an interesting one, but as the article addressed, aerogel can only really handle tiny stuff like paint chips. The lasers in space is probably the most effective solution, but costs so much in terms of energy generation that it is still a ways off in any large scale deployment.

So what else did the article discuss? Well it mentioned the Kessler effect, which has nothing to do with dealing with space junk, but is just a model used to describe space junk. It mentioned that NASA is now putting more efforts into tracking space junk. This is important, of course, but doesn't qualify as a method for removing it or handling it (excepting the very indirect means of simply avoiding it). Then it talks about shielding spacecraft from space junk. This, of course, is necessary and current practice, but no amount of shielding (presently) will protect you from detached thermal blankets or burnt out Delta stages.

All in all, this article just seemed like a disorganized, loosely-themed, terse ramble. I usually expect better from Discover but was severely disappointed in this particular release.

The perfect solution has already been worked out

[TrentTheThief]

This is the solution:

http://en.wikipedia.org/wiki/Salvage_1

Lasers...

[Joce640k]

This guy built a laser which tracks mosquitoes in a room and zaps them. Surely the technology can be adapted...

Re:Lasers...

[BJ_Covert_Action]

You know, I always wanted to talk to that guy for the exact reason you posted. I thought it would be a great university project for some aerospace engineering students to team up with this guy and build a small satellite (~500 kg) that used some combination of high-load capacitors, trickle charge electronics, solar cells, and his laser-tracking technology to basically float around Earth for awhile in a particularly polluted altitude band and just try zapping what ~10 cm pieces of space junk they could find. It would be a great effort for the students, and would act as a wonderful proof-of-concept demonstrator to the big players in the space industry.

Re:Lasers...

[BJ_Covert_Action]

Oh, also, most of the things we've hit with lasers in space, today, are things whose relative position, velocity, flight path, and orientation are known. Recognizing an anonymous piece of cold debris, targeting it, and maintaining laser contact on it for any decent amount of time is a significantly different problem than targeting the next satellite in a known constellation and establishing a two-way communication protocol between hardware.

Re:Hmm

[Sir_Lewk]

Why shouldn't it be hard? Large changes in velocity require large amounts of fuel. Doesn't matter if you are "speeding up" or "slowing down". That's why so many of these ideas involve working out a way for satellites to increase their drag after a time.

The real problem...

[fahrbot-bot]

...like lasers in space.

The main obstacles being shark deployment and survivability.

I think this applies...

[badboy_tw2002]

Hi there! Your post advocates a

( ) technical ( ) legislative ( ) market-based ( ) vigilante

approach to fighting space junk. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.)

( ) Junkers can easily use it to create more space junk
( ) Space stations and other legitimate space uses would be affected
( ) No one will be able to find the guy or collect the money
( ) It is defenseless against brute force space dumps
( ) It will stop space junk for two weeks and then we'll be stuck with it
( ) Users of space will not put up with it
( ) NASA will not put up with it
( ) The space police will not put up with it
( ) Requires too much cooperation from space junkers
( ) Requires immediate total cooperation from everybody at once
( ) Many space users cannot afford to lose business or alienate potential employers
( ) Space junkers don't care about other junk in their junk
( ) Anyone could anonymously destroy anyone else's career or business

Specifically, your plan fails to account for

( ) Laws expressly prohibiting it
( ) Lack of centrally controlling authority for space
( ) Launches in foreign countries
( ) Difficulty of searching for tiny junk in all of space
( ) Asshats
( ) Jurisdictional problems
( ) Unpopularity of weird new taxes
( ) Public reluctance to accept weird new forms of money
( ) Huge existing investment in space
( ) Armies of worm riddled broadband-connected Windows boxes
( ) Eternal arms race involved in all space junk collection policies
( ) Extreme profitability of space junk
( ) Joe jobs and/or identity theft
( ) Technically illiterate politicians
( ) Extreme stupidity on the part of people who do business with space junkers
( ) Dishonesty on the part of space junkers themselves
( ) Fuel costs that are unaffected by space junk
( ) Outlook

and the following philosophical objections may also apply:

( ) Ideas similar to yours are easy to come up with, yet none have ever
been shown practical
( ) Any scheme based on opt-out is unacceptable
( ) We should be able to talk about space Viagra without being censored
( ) Countermeasures should not involve missles
( ) Countermeasures should not involve more junk
( ) Countermeasures must work if phased in gradually
( ) Sending things to space should be free
( ) Why should we have to trust you and your space garbage company?
( ) Incompatiblity with space licenses
( ) Feel-good measures do nothing to solve the problem
( ) I don't want the government cleaning up space
( ) Killing them that way is not slow and painful enough

Furthermore, this is what I think about you:

( ) Sorry dude, but I don't think it would work.
( ) This is a stupid idea, and you're a stupid person for suggesting it.
( ) Nice try, assh0le! I'm going to find out where you live and burn your
house down!

Re:Incinerator

[GodfatherofSoul]

The same reason you don't carry your car to work to save gas money.

Statistics...

[Sir_Lewk]

...that is not how they work.

There are no 669,725 people that are in any more danger than anyone else. There isn't a 1/10,000 chance that it will hit each person, there is a 1/10,000 chance that it will hit any person. In other words, for every ten-thousand pieces of space junk that fall, you might get a single casualty.

If you think these are particularly bad odds, then I have some bad news about your car...

Re:Out of dimension?

[djdanlib]

You need to get through all the orbits of uncontrolled junk, which takes a lot of calculation and you can only move so fast.

You have to be able to get out of the way of new junk that's moving so fast you can't accelerate quickly enough to wait and see if it might miss you.

Calculation of junk trajectory is only so precise, so you have to leave a 'safety buffer' of sorts.

There's more junk up there than we have cataloged. There will always be new junk, and collisions alter orbits of existing junk such that our known trajectories become inaccurate and we have to relocate and recalculate all the time.

So finding a safe zone which requires the least fuel usage to stay alive is becoming more challenging.

Tiny fragments that wouldn't harm anyone if you threw it at them are deadly, equipment-wrecking projectiles at high velocity. Think about a small piece of metal, like a penny. Not a problem if you drop it on your foot. Not going to destroy a vehicle if you drop if off a towering skyscraper, even. But, in space where there's no[t enough] atmosphere to slow it down or burn it up, it can theoretically approach any speed... and a 1,000 MPH penny is a fearsome entity to a fragile laboratory measurement device. We might not even be able to track that very accurately, but if you guess wrong... you transfer that momentum into multiple new shards of former expensive equipment!

So getting things into space is really getting more complicated and keeping things alive up there takes a lot more calculation and fuel as the probability of stray objects increases. Does that cut down on the exaggeration factor?

Re:Out of dimension?

[rlseaman]

the warning seem a bit exaggerated

Consider that each object (in low Earth orbit) is in a separate orbit. Each pair of orbits crosses twice on opposite sides of the Earth. The eccentricity of each orbit causes the object to traverse a range of altitudes, defining the subset of all the LEO objects that are possible collision risks at any given time. The risk for two particular objects colliding is low, but each object has many other opportunities as it crosses thousands of other orbital tracks each time it circles the Earth. Then integrate over all the objects. The probability is a nested summation - integrated over time.

For example, assume there are about one hundred spacecraft (active and defunct) occupying a particular semimajor axis "zone". Each satellite orbits once every 90 minutes, ie, 16 orbits/day. Each satellite crosses the orbit of another about 200 times in that 90 minutes. Usually the other spacecraft is somewhere else entirely, but there are a lot of opportunities.

Establish a "comfort radius" - say, one kilometer. If Le Petit Prince is sitting on a satellite, he will get very nervous if another spacecraft zooms through this keyhole at 10 km/s. A typical low Earth orbit is about 42,000 of these comfort units long. So the odds (ignoring altitude for the moment) of finding a spacecraft within the same part of the orbit - during each passage - is 1/42,000. Multiply by the 200 opportunities makes this 1/210 (0.5%) per orbit or about 7.5%/day/spacecraft. There are 100 spacecraft in this zone, so that amounts to about 4 close encounters per day (divide in half since it takes two to tango) in which some spacecraft passes directly above or below another by a few kilometers.

Accounting for altitude requires a bit more physics (inverse square law and all that), but basically amounts to a similar argument of dividing the altitude range traversed by each satellite into comfort zones. The odds of passing through the keyhole drop, but not dramatically - and the orbit crossings keep piling up about a hundred thousand per day per altitude range. With each close encounter, the odds of an impact are basically very simple. What is the volume of a typical spacecraft divided by the 1 km^3 volume? (The second spacecraft either will or won't be occupying the same volume at the moment of closest approach.) Satellites can be surprisingly large - Hubble is about the size of a schoolbus - but figure a Volkswagen van or at least a Beetle.

Bear in mind that this is just one particular altitude range, the same thing is happening at different altitudes. Some spacecraft are in highly elliptical orbits and cross through several such zones. In short, what seems to be a three dimensional problem is really one dimensional. After the spacecraft collision a couple of years ago some of us were scribbling on a blackboard. A physical model would be needed to get the precise answers, but a ball park figure is that we can expect the apparently astronomically rare event of two LEO spacecraft colliding to happen about once per decade (in the absence of active station keeping). Then account for all the debris, not just complete spacecraft.