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# NASA Wants To Zap Space Junk With Lasers

#### samzenpus posted more than 3 years ago | from the space-sharks dept.

148

Hugh Pickens writes "MIT Technology Review reports that various ideas have been floated for removing space junk, most of them hugely expensive, but now James Mason at NASA Ames Research Center has come up with the much cheaper option of zapping individual pieces of junk with a ground-based laser, to slow them down so that they eventually de-orbit. Mason estimates that a device to test the reversal of the Kessler syndrome could be put together for a million dollars, which would have to be shared by many space-faring nations, to avoid the inevitable legal issues that using such a device would raise. 'The scheme requires launching nothing into space — except photons (PDF) — and requires no on-orbit interaction — except photon pressure. It is thus less likely to create additional debris risk in comparison to most debris removal schemes,' writes Mason. 'Eventually the concept may lead to an operational international system for shielding satellites and large debris objects from a majority of collisions as well as providing high accuracy debris tracking data and propellant-less station keeping for smallsats.'"

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### i have a better use for these lazers (-1)

#### Anonymous Coward | more than 3 years ago | (#35506454)

dingleberries. damn if they don't hurt.

### Re:i have a better use for these lazers (0)

#### Anonymous Coward | more than 3 years ago | (#35507408)

Just think of them as Mother Nature's Brazilian wax. Grip 'n' rip.

### Insert shark joke here... (-1)

#### Anonymous Coward | more than 3 years ago | (#35506458)

...for instant +5, Funny!

### Re:Insert shark joke here... (0)

#### russlar (1122455) | more than 3 years ago | (#35506542)

I tried, and found a "Lameness filter"

### I Predict (0)

#### Jeremiah Cornelius (137) | more than 3 years ago | (#35507242)

Lots of smaller, harder to track debris, moving at higher velocities.

Didn't these numbskulls ever play "Asteroids"?

### Re:I Predict (1)

#### BlackSnake112 (912158) | more than 3 years ago | (#35507706)

They may not be old enough to have played Asteroids.

### Re:Insert shark joke here... (0)

#### Anonymous Coward | more than 3 years ago | (#35506572)

Not really. TFA says ground-based. Everyone knows there are no land-sharks. Not yet, anyway.

(tap tap tap)
"Candygram!"

### Re:Insert shark joke here... (1)

#### Kosi (589267) | more than 3 years ago | (#35507168)

You need to read some books from Walter Moers, a German writer. Then you'll know that a species called "shark maggots" lives on the continent of Zamonia.

### Re:Insert shark joke here... (1)

#### elrous0 (869638) | more than 3 years ago | (#35506582)

Yeah, it's all fun and games until someone gets him it the head with an old satellite.

### Re:Insert shark joke here... (1, Funny)

#### yeshuawatso (1774190) | more than 3 years ago | (#35506736)

How big is your "junk" that it needs to be zapped while you're in space?

### Will the TSA be in charge of the "junk"? (1)

#### sconeu (64226) | more than 3 years ago | (#35506994)

And China will tell the US "You touch my junk, and I'll nuke you!"

### Ground-based lasers powerful enough to... (0)

#### Anonymous Coward | more than 3 years ago | (#35507600)

And China will tell the US "You touch my junk, and I'll nuke you!" ...blast orbiting stuff might also just be powerful enough to shoot down any incoming ICBMs too!

### Re:Insert shark joke here... (1)

#### dpilot (134227) | more than 3 years ago | (#35507286)

Or worse, getting hit by a re-entering toilet.

### Re:Insert shark joke here... (0)

#### Anonymous Coward | more than 3 years ago | (#35507388)

Or worse, getting hit by a re-entering toilet.

I do believe that was "Dead Like Me"

### Re:Insert shark joke here... (1)

#### blair1q (305137) | more than 3 years ago | (#35506702)

See the dept tag on the summary.

### Re:Insert shark joke here... (1)

#### natehoy (1608657) | more than 3 years ago | (#35506888)

Not for... (sticks pinky finger to mouth)... One MILLion dollars!

### Re:Insert shark joke here... (1)

#### SnarfQuest (469614) | more than 3 years ago | (#35507656)

Are sharks really accurate enough to shoot down orbital debris with a head mounted laser? If they released some piranha into the sharks tank, would that be sufficient to destroy Tokyo (is a thrashing shark with a laser as powerful as Godzilla)?

#### olsmeister (1488789) | more than 3 years ago | (#35506476)

Ability to blind and de-orbit enemy satellites in wartime.

#### Anonymous Coward | more than 3 years ago | (#35506552)

Another added bonus, Shoot out the Aliens in case of invasion!

#### MikeDirnt69 (1105185) | more than 3 years ago | (#35506758)

And if you are good enough, can do with just one coin!

#### blair1q (305137) | more than 3 years ago | (#35506730)

Ability to blind populations on the ground in peacetime.

This laser would have to be powerful.

Satellites are irregularly-shaped and have flat reflective surfaces.

See where I'm going with this?

Not for long.

#### Anonymous Coward | more than 3 years ago | (#35506890)

I see what you did there.

#### interkin3tic (1469267) | more than 3 years ago | (#35506958)

Ability to blind populations on the ground in peacetime. This laser would have to be powerful. Satellites are irregularly-shaped and have flat reflective surfaces. See where I'm going with this?

Are you suggesting that governments will blind, say, protesters or peaceful people they don't like who happen to be staring at the lasers or at sattelites, which will reflect the beams into their eyes? Wow, that WOULD be a nightmare scenario, those evil bastards! So much wasted tax money! They should really stick to the low-tech grabbing them, putting them in a van, and burying them in an unmarked grave. It's SO much more efficient.

#### blair1q (305137) | more than 3 years ago | (#35507346)

I'm using the word "ability" ironically.

In fact, what I'm really saying is, there's really no safe way to use this thing on a random piece of space junk. Far too great a chance of half of its energy being reflected back into the face of one of the millions of people oooing and ahhhhing on the ground when it's fired into the sky.

#### hedwards (940851) | more than 3 years ago | (#35508354)

That's not how that works. The likelihood of that happening is nihil. It takes a huge amount of energy to get a laser to paint the target, let alone actually cause a perceptible change in velocity, the reason being that light tends to get scattered as it passes through the atmosphere. So, in order to bounce a laser off a bit of debris in space and get it in the eyes of anybody, is more or less impossible, when you account for the loss of energy, the tiny target on both ends.

Even when people are trying to hit larger targets at a closer distance and lower velocity, like say those morons trying to blind pilots, the amount of effort it takes is still pretty impressive, and rarely if ever do they manage to actually get it in the eye of any of the flight crew.

#### wagnerrp (1305589) | more than 3 years ago | (#35508616)

Well there is also the fact that those laser pointers paint a target half the size of the airplane at a mile out. Even were they to aim correctly, the beam would be too diffuse to be more than a nuisance.

#### Anonymous Coward | more than 3 years ago | (#35507116)

Um, these are ground based weapons. Though I guess we could reflect them off a shiny satellite like in "Top Secret".

#### natehoy (1608657) | more than 3 years ago | (#35507238)

There are already websites that track what are called "Iridium Flares" where the sun reflects off one of the boxy, shiny AT&T Iridium satellites. Focus the beam a little more and you could accomplish some fairly serious eye damage. However, aiming such a thing at a specific target for any length of time would be damned near impossible.

If you wanted to truly permanently blind a populace, issue each of your people a 1kw aiming laser for their rifles. If you want to temporarily blind them, set up a couple of powerful spotlights on a tall building or helicopter. It's a lot cheaper and more reliable.

#### holmstar (1388267) | more than 3 years ago | (#35508410)

1kw?! A couple of watts would be enough to blind you, at least wherever the laser focused on your retina.

#### wagnerrp (1305589) | more than 3 years ago | (#35508796)

Actually, less than a mW of sustained exposure would be sufficient to cause permanent damage. Somewhere up to around 5mW is considered "safe" as your blink reflex will happen fast enough to protect your eyes. Also, we've already got this nice stellar object about a hundred million miles out that will cause damage if you stare at it.

At just a few kW, there is absolutely no risk of harm from this. The beam will scatter and spread on the way up through the atmosphere, hitting the object at something far less than full intensity. It will hit the object, which is not perfectly flat, nor perfectly reflective, further spreading the beam. It will have to pass back through the atmosphere, scattering further. That full 800mi+ trip will easily drop the beam the 6-7 orders of magnitude power needed to render it safe.

#### Jurily (900488) | more than 3 years ago | (#35507280)

Satellites are irregularly-shaped and have flat reflective surfaces.

How is this not +5 Insightful already? Does anyone really think we can split or stop metal parts by shining light on them? It was a slightly less retarded idea when all they wanted to do was burn a tiny little hole into aircraft and nukes, but this is ridiculous.

Since when does NASA take their knowledge of physics from Star Trek?

#### blair1q (305137) | more than 3 years ago | (#35507374)

The theory of it works, kinda-sorta, but only for objects for which you know all of the characteristics, and environments where everyone and everything that's vulnerable to backscatter is protected. Space-junk and satellites are basically randomized, especially when they're in a state where you have to use a ground-based laser to try to nudge them into more-quickly-deteriorating orbits.

They might as well flash this thing at a disco ball and tell everyone to get a good look.

#### Anonymous Coward | more than 3 years ago | (#35507580)

Yes, it's absolutely unpossible [navy.mil] for them to use a laser to destroy objects traveling above the earth's surface at high rates of speed! Unpossible, I say!

If you bothered to read the article, you'd see that they're talking about using either:

1) A powerful-enough laser to ablate the surface of the junk enough to destabilize its orbit so it falls back into the atmosphere and burns up;
or
2) Using the momentum of photons from a lower-power laser over a longer period of time to slow down the junk enough to cause it to de-orbit and burn up;

Both are certainly possible given current technology.

#### rgbatduke (1231380) | more than 3 years ago | (#35507866)

What? You insist on doing arithmetic? Something like P = I/c (within a factor of 2) for the radiation pressure exerted by light? So that if we make a very generous assumption of a kilowatt in a single square centimeter, we have 10^3/3x10^8 \approx 3 x 10^-6 Pa. We multiply by 10^-4 square meters (one square centimeter) and get 3 x 10^-10 Newtons. Take into account attenuation in the atmosphere and the fact that the beam is wiggling all over the place because of atmospheric thermal ripple and lensing, and you would be lucky to exert 10^-11 Newtons per kilowatt per square centimeter of laser beam.

If our supposed space junk is travelling in an actual low orbit, it is travelling at roughly 7 km/sec. Let's assume that it has a mere 10 kg of mass -- if it is much smaller just finding it from Earth will be difficult, let alone hitting it. Lessee, F=ma, so we can give it a maximum relative acceleration of a whopping 10^-12 m/sec^2! A year, on the other hand, has a mere \pi x 10^7 seconds, and of course we can shine our laser on the object at most a few hours a day -- again, a duty cycle of 10^7 seconds/year would be enormously generous.

This means that we can -- over a whole year -- change the velocity of the junk by 10^-5 meters/second! That's right folks, you heard it here first -- ten microns per second per year of thrust with a 1 KW laser beam 1 cm across, and downhill from there in nearly every direction.

Of course this is still wildly optimistic. The problem is that we are exerting the thrust on the object from underneath. This is more or less at right angles to the direction of motion, and hence does very little to speed it up or slow it down. In fact, pretty much nothing. If we wait until it is directly overhead to hit it, we get the cosine of a nearly right angle as a transverse component and can only fire on half of the overhead pass before we are hitting it from the rear and speeding it up again. If we fire at an oblique angle, to get a good dot product cosine with the direction of thrust and direction of motion, we have to go through an equally oblique layer of atmosphere that both bends the laser beam (making it effectively impossible to hit the target) and attenuates the kilowatt still further (reducing efficiency at about the same rate the dot product improves).

If the material were highly ablative, and if we could hold the beam steady enough to actually heat the object to where it boils, we could get some real thrust. Even a thin layer of actual reaction mass being boiled off of the surface would exert orders of magnitude more force than a perfectly reflected laser beam. But even orders of magnitude more thrust would almost certainly not suffice to slow the object enough to in any possible drug-addled, hallucinatory Universe make this an economically feasible, intelligent idea.

Now I know who was using the cocaine found at NASA today. Whoever it was that dreamed this one up.

rgb

### Since most people learn science from Star Trek (1)

#### jeko (179919) | more than 3 years ago | (#35508756)

Does anyone really think we can split or stop metal parts by shining light on them?

I had a guaranteed military sale with ED 209. Renovation program. Spare parts for 25 years. Who cares if it worked or not?
-- Dick Jones, Robocop

Are you kidding? This idea is brilliant. It's an impossible goal that demands huge amounts of funding which the military will find as appealing as crack-soaked catnip served on hookers. It's not a blank check -- it's a limitless credit card that will never get declined. They've been buying this schtick since Reagan. When this idea plays out -- finally, a few decades from now -- we'll just move on to promising them phasers, then blasters and light sabers.

#### Anonymous Coward | more than 3 years ago | (#35507358)

so this would be creating the largest disco ball in the solar system?

#### EdZ (755139) | more than 3 years ago | (#35507766)

The laser would have to be focussed pretty accurately onto the satellite to be effective. After passing through a few hundred kilometres of atmosphere twice, and being hugely out of focus (i.e. diffused over a large area), the most you'd see from the ground would be a bright flash, no worse than an Iridium flare.

#### bluemonq (812827) | more than 3 years ago | (#35507906)

...except for the part where changing air currents and densities (the same reason why starlight seems to twinkle at night) distorts lasers, so there are "tracer" low-powered lasers so that the system can properly shape, focus, and aim the main beam. You think that reflected laser is going to magically focus itself after bouncing off of some junk to blind someone? Come on folks, this is basic SDI/ABL stuff.

#### Aighearach (97333) | more than 3 years ago | (#35508152)

I don't know where you're going with it, but I see where you're coming from... right out your BLEEPITY!

#### Anonymous Coward | more than 3 years ago | (#35506778)

As usual, the Simpsons had it right:

The wars of the future will not be fought on the battlefield or at sea.
They will be fought in space, or possibly on top of a very tall
mountain. In either case, most of the actual fighting will be done by
small robots. And as you go forth today remember always your duty
is clear: To build and maintain those robots.

#### GooberToo (74388) | more than 3 years ago | (#35506930)

I actually hadn't thought of that bug good point. What did occur to me was the exact opposite of that coin. Meaning, couldn't this then be used as a was to change orbits or to provide a boost in altitude?

#### michelcolman (1208008) | more than 3 years ago | (#35506992)

And you can say "I didn't do it!", who's going to prove otherwise?

#### mysidia (191772) | more than 3 years ago | (#35508636)

Ability to blind and de-orbit enemy satellites in wartime.

It's too slow, and any satellite with propulsion will be able to compensate. Unless your laser is powerful enough to cut up or burn parts of the enemy satellite, or they rely on unprotected optics, then it won't work.

#### Anonymous Coward | more than 3 years ago | (#35506486)

And, if development of the technology also allows the US to de-orbit other country's satellites that's all to the good. Right?

### Lasers (1)

#### Grapplebeam (1892878) | more than 3 years ago | (#35506528)

Is there any problem they CAN'T fix?

### Re:Lasers (2)

#### f8l_0e (775982) | more than 3 years ago | (#35506586)

To answer your question, there is a reason the signs outside laser labs say "Do not stare at laser with remaining eye."

### Re:Lasers (2)

#### Nadaka (224565) | more than 3 years ago | (#35506652)

That is a problem that lasers can fix, you will eventually run out of remaining eyes.

### Re:Lasers (2)

#### Nidi62 (1525137) | more than 3 years ago | (#35506830)

That's why you use that other universal fixer. Just cover said "remaining eye" with duct tape.

Parking tickets?

### Let's face it... (2, Funny)

#### Anonymous Coward | more than 3 years ago | (#35506532)

...everyone wants to zap space junk with lasers. NASA just happens to be in a better position than most to get the job done.

### I've always said we need a Grand Cannon (1)

#### GodfatherofSoul (174979) | more than 3 years ago | (#35506550)

Just never knew where we could find the protoculture to power it [robotech.com] . Plus, it would come in handy [youtube.com] when some pesky ETs show up looking to steal our resources and women!

### Wooosh ... (-1)

#### Anonymous Coward | more than 3 years ago | (#35506554)

You know that they've accomplished their task as soon as you spot the first shark in orbit ...

### Shields at maximum! (3, Funny)

#### Thraxy (1782662) | more than 3 years ago | (#35506584)

Fire photon torpedoes!

### FPS game!! (2)

#### nowen2dot (1768088) | more than 3 years ago | (#35506590)

Oooh! Can they set up a web interface and charge money for us to shoot them!!!?

Who wants high score??

### James Mason Continues... (2, Funny)

#### Ancantus (1926920) | more than 3 years ago | (#35506596)

To avoid legal incidents we will be mounting the lasers in international waters. We will be subsidizing costs by using existing biological life-forms, mainly sharks, as the key base for the laser installation. Aiming the devices will also utilize the shark's keen sense of smell to identify and destroy decaying orbital installations.

### Re:James Mason Continues... (1)

#### fragfoo (2018548) | more than 3 years ago | (#35506798)

You jumped the shark with that one

### Re:James Mason Continues... (1)

#### jd2112 (1535857) | more than 3 years ago | (#35507846)

And this plan that i propose will cost (pinky to moth) ONE BIIIILIEEEON DOLLARS! (strokes hairless cat)

### And then when the rat-cats invade.. (1)

#### IICV (652597) | more than 3 years ago | (#35506600)

And then when the Kzinti invade, we'll just turn the lasers on them! It's a win/win situation, really.

### lasers... is there anything they can't fix? (1)

#### Aighearach (97333) | more than 3 years ago | (#35508228)

Niven... is there anything he can't fix?

### Ah, the possibilities... (2)

#### fuzzyfuzzyfungus (1223518) | more than 3 years ago | (#35506610)

There are some very pricey earth-facing CCDs, behind sophisticated optics, in earth orbit. Be a pity if any of them were to catch fire...

### Lasers? (-1)

#### Anonymous Coward | more than 3 years ago | (#35506624)

How about sharks with lasers? Sharks... In... Space!!!!!!!

### Recycled from 2000 (2)

#### Bamfarooni (147312) | more than 3 years ago | (#35506626)

NASA Hopes Laser Broom Will Help Clean Up Space Debris
http://www.spacedaily.com/news/debris-00a.html [spacedaily.com]

### Re:Recycled from 2000 (2)

#### Daniel Dvorkin (106857) | more than 3 years ago | (#35506850)

What TFA is talking about is the same as the laser broom in the same way a street-sweeping machine is the same as a guy with a pushbroom. The goal is similar, but there's a vast difference in scale.

### oblig. (2)

#### memnock (466995) | more than 3 years ago | (#35506640)

Are sharks space worthy?

Frickin' worthy.

### Re: NASA Wants To Zap Space Junk With Lasers (1)

#### shallot (172865) | more than 3 years ago | (#35506678)

Am I the only one who read this title and immediately thought of Frau Farbissina yelling "Fire the laser"? :)

### Prior art (2)

#### inviolet (797804) | more than 3 years ago | (#35506696)

but now James Mason at NASA Ames Research Center has come up with the much cheaper option of zapping individual pieces of junk with a ground-based laser

Pfah, this is an old idea: it's called a laser broom [wikipedia.org] .

Pew. Pew.

### Re: Prior art (1)

#### tophermeyer (1573841) | more than 3 years ago | (#35507518)

The laser is \$0.8 million. The tracking and optics needed to point the laser in the right direction were described as costing millions to tens of millions.

Basically there is a piece of COTS tech that will kind of do what the laser broom would have done. Just much cheaper on a much smaller scale. Also we still don't quite know how to do it yet.

### Re:Prior art (3, Funny)

#### BattleApple (956701) | more than 3 years ago | (#35507096)

The breakthrough is that these are the first lasers that actually make a pewpew sound.

### Re:Prior art (0)

#### Anonymous Coward | more than 3 years ago | (#35507756)

Similar idea, but with a lesser laser.

The idea is to nudge objects out of collision courses so they don't cause more orbital junk, but instead encourages them to deorbit.

Lesser lasers that can only nudge objects are much more less threatening politically friendly. For objects that don't have manuvering capability of their own something is needed.

### One way to address the pidgeon problem. (0)

#### Anonymous Coward | more than 3 years ago | (#35506704)

Am I the only one that got this image of charred feathers fluttering gently to the ground? Sizzle, poof, flutter.

### Re:One way to address the pidgeon problem. (1)

#### Nadaka (224565) | more than 3 years ago | (#35506792)

It works for mosquitoes.

### Re:One way to address the pidgeon problem. (1)

#### TheRaven64 (641858) | more than 3 years ago | (#35507258)

I'm not an entomologist, so I could be wrong, but I'm pretty sure that mosquitos don't have feathers...

### Missile Command interface (1)

#### gsgriffin (1195771) | more than 3 years ago | (#35506862)

Can just see it now....all these aging NASA guys sitting around a trackball playing Missile Command...but for real. Sign me up!!!

### One possible logistical problem... (0)

#### Anonymous Coward | more than 3 years ago | (#35506920)

How are they going to get the sharks up there?

### Old idea... (1)

#### Jaegs (645749) | more than 3 years ago | (#35507150)

Meh. This idea has been bouncing around for a while now: http://www.youtube.com/watch?v=UN8YIR60Ij0 [youtube.com] Though the application demonstrated in the video was for a slightly different purpose, it would be an additional benefit, should the need arise.

### Re:Old idea... (0)

#### Anonymous Coward | more than 3 years ago | (#35507858)

Or, we could use the Japanese suggestion, although that doesn't involve blowing shit up.

### Auction off satellite hunting rights! (1)

#### PolygamousRanchKid (1290638) | more than 3 years ago | (#35507182)

Pay big bucks to bag an elephant? Or a rare Antarctica albino bearded clam tiger? Offer folks who have unreasonable amounts of money the opportunity to bag a satellite. It looks great mounted, up on the wall of the Africa room, next to Bambi's head. The profits could go to getting NASA back into action.

We'll aim the laser on the satellite, Sir . . . all you have to do is pull the trigger . . .

### Not about de-orbiting anything (2)

#### PSaltyDS (467134) | more than 3 years ago | (#35507218)

In reply comments at the bottom of TFA you see they are NOT talking about de-orbiting things this way, only making minute changes in orbit to avoid collisions.

Perhaps preventing collisions allows natural decay to remove debris faster than it accumulates, but other than that, their plan was not about de-orbit of debris.

### How about sending BB guns to the space station. (0)

#### Anonymous Coward | more than 3 years ago | (#35507298)

Maybe we could just send a couple of Daisy BB guns to the International space station. When the crew gets bored they can go for a space walk and practice space debris skeet shooting.

### Re:How about sending BB guns to the space station. (1)

#### Kosi (589267) | more than 3 years ago | (#35507924)

I'd rather use something without recoil for that, unless we want to add some astronauts to the debris.

Oh, and I faintly remember a SciFi story about two enemies on Mars, where one misses shooting his last bullet at the other. The other one just kept talking with him, until the bullet, being fast enough to make a full orbit, hit the guy who shot it in his back. Or at least something like that, must be about 25 years ago. Anyone who knows that story here?

### Lasers aimed at space (0)

#### byteherder (722785) | more than 3 years ago | (#35507320)

Don't we have something like this already. Isn't it called StarWars.

### Or you can recycle the mass (0)

#### Anonymous Coward | more than 3 years ago | (#35507442)

There's been interesting talk about trying to recycle this on-orbit material, since significant energy costs have been paid to get it up into orbit. Such a scheme would be orders of magnitude more difficult, since you're trying to do more than just roughly reduce the velocity of some object by selectively burning off its +V side, and instead you're trying to corral enough space junk into similar orbits that you can cause clumps to accrete. Presumably, the accretion would involve broader scale application of energy--off the top of my head, I'd say a shitload of directed microwaves, since directing shitloads of microwaves is something we're relatively good at, but there's no analysis behind that.

Exciting times.

### What legal issues? (1)

#### Kosi (589267) | more than 3 years ago | (#35507500)

Any law that forbids cleaning up space? As there is no international convention about at which height airspace ends and space starts, all should be fine if the country using such a laser only shoots stuff above it's own territory.

### I agree (1)

#### unassimilatible (225662) | more than 3 years ago | (#35508324)

Since when should countries give away their technology because of fear of lawyers? OK, this is Slashdot, so I'd better re-word that.

### They can fire lazers at my junk any time. (1)

#### AbRASiON (589899) | more than 3 years ago | (#35507536)

They are trying to increase the size of Mr. Spaces junk right? This is what scientists do yes?
8=====D

### Play Katamari Damacy in space with a big magnet (0)

#### Anonymous Coward | more than 3 years ago | (#35507638)

Maybe we could put a big magnet in space and play Katamari Damacy with the space junk.

### Prototype (0)

#### Anonymous Coward | more than 3 years ago | (#35507852)

The people in my neighborhood have been running scaled down tests of this technology using laser pointers at aircraft for years.

### Send up a garbage scow (0)

#### Anonymous Coward | more than 3 years ago | (#35507920)

http://en.wikipedia.org/wiki/Quark_%28TV_series%29

### Enormously stupid idea... (2)

#### rgbatduke (1231380) | more than 3 years ago | (#35508020)

I commented elsewhere on the actual numbers, which show quite clearly that even a 5 kw laser would exert at most completely irrelevant forces on any object large enough to actually see from earth and hence target -- accelerations on a good day of 10s of microns per second per year of radiation pressure. Having RTFA and noted all of the corrections by the authors (of the idea, if I understand things correctly) it is still an enormously stupid idea. What part of piconewton scale forces is difficult to understand?

I give this one as an assignment for my intro physics classes -- suppose you have a megawatt laser with a beam 1 cm^2 across and mount it on the rear of your spaceship to use as a drive. Wow, a whole million watts of power! Surely that will provide the ship with all kinds of thrust!

Sure, if all kinds of thrust is a few micronewtons.

You'd get more thrust -- and probably more net delta-vee for any acceleration time you are willing to wait -- if you simply took the laser to the door of your capsule and threw it, as hard as you can, away.

rgb

### Re:Enormously stupid idea... (1)

#### Xtifr (1323) | more than 3 years ago | (#35508346)

Yeah, too bad they're relying entirely on light pressure, and aren't planning to take advantage of, say, the possibly-catastrophic outgassing they might get from heating one side of an object. I mean, obviously one of their main concerns is going to be not damaging the objects they're trying to destroy.

### Re:Enormously stupid idea... (1)

#### rgbatduke (1231380) | more than 3 years ago | (#35508612)

In the after-article article they make it clear that they're not trying to destroy the objects (which they cannot do in any event), and that they recognize that it would take decades to actually knock something out of orbit (a vast underestimate -- try centuries). They allege -- and I'm still having a hard time seeing it but it is barely possible -- that they can divert the orbit of something enough to prevent a collision. The after article also makes it clear that the actual cost of building a laser system to do any of this is orders of magnitude more than a million dollars -- that's the cost of just the laser, not the targeting system, which has to be just as accurate and stable as any star wars antimissile laser device. They also clearly state that they are relying on light pressure, not outgassing or heating in general.

Changing an orbit enough to cause the junk to miss by meters instead of hit something is at least in the realm of the possible, given that tiny changes in orbital velocity can make large changes in orbital position over a long enough time base. Large at least compared to the size of a space ship.

I'd like to see the actual arithmetic that they use to justify this, though. The piconewtons from the laser actually have to be compared to things like the piconewtons being exerted by the light pressure from Mr. Sun at this sort of scale, and the sun shines on them all of the time. The forces are likely within an order of magnitude of each other, and are comparable to the extra force you experience when you lie down on the beach at noon on a sunny day.

rgb

### ablation, not photon thrust (0)

#### Anonymous Coward | more than 3 years ago | (#35508372)

I think you are thinking of momentum transfered by photons, this heats part of space junk to high temperature, to vaporize. Much better thrust to energy ratio.

### Re:Enormously stupid idea... (1)

#### Antique Geekmeister (740220) | more than 3 years ago | (#35508438)

But you can use such arrays against paint, rust, frozen water, and the other dust cluttering LEO. And that should be quite detectable as "glitter" in the ordinary spy satellite monitoring of LEO, which is taken from LEO and has less relative velocity to cope with and less atmospheric distortion. So I think your premise of being able to "see it from Earth" has nothing to do with most of this debris.

### Re:Enormously stupid idea... (1)

#### pz (113803) | more than 3 years ago | (#35508544)

A 5KW laser is surely going to cause surface vaporization and thus create potentially far more thrust that the light pressure alone.

### Obvious question (1)

#### Baloo Uriza (1582831) | more than 3 years ago | (#35508084)

Will they be shark-mounted?

### Real Genius (0)

#### Anonymous Coward | more than 3 years ago | (#35508522)

I mean... what if my "space debris" is a well calibrated reflective surface...

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