October 27, 2011
De-Orbit Space Junk With High Powered Lasers?

Lots of little and big pieces of space junk are making Earth's orbit an increasingly polluted and hazardous place. What to do about it? A Wired piece reports on a proposal to hit space junk with lasers to cause plasma jets that will de-orbit the junk.

The heat from the laser blasts would vaporize a minuscule part of a piece of space junk, resulting in a plasma jet that could slow the object down enough to bring it out of Earth orbit.

“You’re essentially creating a laser-powered rocket, using the object to be its own fuel,” said engineer Claude Phipps of the company Photonic Associates, LLC, who co-authored the laser-removal paper, published Oct. 17 on arxiv.

This is a cool idea. Lots of other ideas (see the article) involve lots of mass up in Earth's orbit moving around trying to catch the junk. Getting the fuel to do this up into orbit is quite expensive. But energy on the ground is a lot cheaper. So laser beams from the ground have real potential if the targeting problem can be solved. Anyone know how hard that problem is?

Share |      Randall Parker, 2011 October 27 08:32 PM  Space Pollution

PacRim Jim said at October 28, 2011 12:21 AM:

Wouldn't laser energy increase rather than decrease the orbital height?

Brett Bellmore said at October 28, 2011 3:52 AM:

No more than energy used in any other form of rocket propulsion. The idea is to ablate material on the leading edge of the space junk, so that it flies off at high speed, just like a rocket exhaust, slowing the junk. It seems feasible to me.

Phillep Harding said at October 28, 2011 11:26 AM:

A single burn causing a random change in orbit is most likely going to result in a more eccentric orbit, so the object swings both further away, and closer. An oval orbit that crosses the more circular, original orbit in four places. The sides of the oval will be closer to atmo so the object will eventually deorbit sooner.

I tried to calculate orbits and escape trajectories, before computers, just for the fun of it. Decided migraines were no fun.

Doug said at October 28, 2011 11:46 AM:

Sounds like a paying job for the International Space station. Put the big laser up there. Sort of a mini Death Star, hmm? Might make the ISS a bit of a target under some scenarios though.

Ronald Brak said at October 28, 2011 4:08 PM:

The ISS vibrates too much to be a good platform for a laser. It would be better to have it in an independant satellite.
Hitting space junk with a laser from earth would be tricky but not impossible. Hitting an object in orbit with a low power laser has been done, but not on the first try.

Doug said at October 28, 2011 5:55 PM:

@Ronald, OK, I'll accept that as correct for discussion prposes, but am skeptical that no damping technology exists capable of stabilizing a laser, even if necessary by temporarily detaching from the ISS, long enough to acquire the target, shoot, then re-dock.

Brett Bellmore said at October 29, 2011 5:13 AM:

"A single burn causing a random change in orbit is most likely going to result in a more eccentric orbit, so the object swings both further away, and closer."

Yup, exactly, and the idea is that on the "closer" part of the orbit it dips down into the upper fringes of the atmosphere, causing it's orbit to progressively decay. You don't have to deorbit the junk with one shot, you just have to transform it from something that will be up there for many years, to something that will burn up within months.

Engineer-Poet said at October 29, 2011 9:30 AM:

The technology is already here.  Hit the piece of space junk with a low-powered laser pulse.  The telescopes of the de-orbiting system receive the reflection of this pulse and transmit it through their optics backwards.  At the far end, the pulse is time-reversed and returned with the conjugated wavefront.  A millisecond later, the piece of junk receives several hundred kJ of laser energy in a few nanoseconds.

You hit these things when they're coming toward you.  The impulse will be up and backward, causing the orbit to be both more eccentric and lower.  Enough of a hit and the orbital lifespan will be measured in hours.

Ronald Brak said at October 30, 2011 4:38 AM:

Doug, I'm sure they could try to attach a space junk laser to the ISS or make one that docks with the ISS, but I don't see why they would bother when it could just float free for its operational lifespan.

Engineer-Poet said at October 30, 2011 12:29 PM:

Why pay to put it in orbit when it can do its work from the ground?

Ronald Brak said at October 30, 2011 3:47 PM:

I don't know.

Doug said at October 30, 2011 4:09 PM:

Well, if based on the ISS, it would have (1) far more power, from those huge solar arrays the ISS has; (2) can be refuelled over and over (for longer lifespan) when docked if it needs to roam somewhat for maximum effectiveness -- after all, the problem with many of the dead satellites is just that they've run out of fuel; (3) repairability and upgradability. Final thought: if it adds anything, you could have several of these things based on the ISS, operating in concert for quicker results.

Engineer-Poet said at October 30, 2011 7:26 PM:

More power on the ISS than a ground-based laser connected to the grid?  Don't insult our intelligence.

Doug said at October 31, 2011 12:47 AM:

So use your intelligence, man. Of course there's more power on the ground! but from up there you don't have to punch through the atmosphere, and might be able in most instances to work from much closer. I was unclear though. I meant more power from the ISS than for an independently operating satellite. Give us all a break. If this can actually be done better from the ground, fine. Seems old-think though. We should be seeking more capabilities in space.

Gary said at October 31, 2011 11:08 AM:

As far as I recall, this was proposed by Ivan Bekey at Aerospace Corp. in the 1970s, and several ties subsequently by others. About 60MW is required, based on memory, though this figure is highly dependent on many variables.

Mel said at October 31, 2011 11:44 AM:

Wasn't that the premise of "The Cardinal of the Kremlin" by Tom Clancy 1988?

Right Wing Nutter said at October 31, 2011 12:01 PM:

A surface based laser would have more power available. It may be worthwhile to build (or refit) a nuclear powered ship with stabilization systems similar to a drilling ship and a gyro stabilized laser system for the final platform accuracy. Such a rig could be moved around the oceans to get good angles on the various orbits and optimum surface conditions. Nuclear power would provide plenty of power, and a ship would provide plenty of storage for exotic fuels if a gas laser was the only way to get sufficient power. (In that case the ship propulsion could be standard bunker oil.)

If there's just too much water vapor interference at sea level then locating the facility on a high desert would be the way to go. The Altiplano or Atacama of Peru, Chile, or Argentina would ensure clear air, and not much of it, day and night. (I leave out Bolivia because of their unreliable and confiscatory socialist government.) Power could come from a dedicated solar thermal station which would also be very effective in such a location. In such a barren and deserted place it would be relatively simple to build an underground "hot rock" heat storage facility that could keep power generation going around the clock. After some years, once the laser is no longer needed for de-orbiting purposes, the laser could be removed and the power plant turned over to the host country to hook into their own power grid.

One thing for sure. A laser technology that can blast plasma off a satellite sufficiently to de-orbit it will be a technology that can be part of an effective ballistic missile defense.

Mister Lynch said at October 31, 2011 12:13 PM:

"Anyone know how hard that problem is?"

Sure: now you're talking about an ASAT system with such capability that the owner can deny the use of space to anybody they want. Try telling the rest of the world that you have one of these, and see what happens!


M. Report said at October 31, 2011 12:18 PM:

Tom Clancy researched his science well; The laser he predicted likely exists today,
but is so highly classified that it will not be used for civilian purposes;
The orbital version would be a very effective weapon of war - or assassination.
Hit-to-kill seeker satellites launched into the retrograde orbit of their targets
would do the job as well, and could not be used as weapons against ground targets.

Alan said at October 31, 2011 12:25 PM:

Problem, as I recall, is that a really high-powered laser pulse through the atmosphere quickly ionizes the gasses in its path. The resulting plasma column is much more opaque than the atmosphere normally is (even if you tune the laser for the infrared atmospheric 'window' between 8-14um, where much less energy is absorbed than at other frequencies.)
Some solutions include: very short pulses (most of the energy gets through before the plasma forms), multiple lasers at lower power all aimed at the same point (less energy in each path, less plasma formation, less energy lost, but a bigger aiming headache), or ... a simpler lower power laser system, in orbit, at a somewhat different orbital height from most of the junk (reduces risk of being hit and ensures that sooner or later every target piece of junk will be a relatively short-range shot.) In all cases, gotta be careful about collateral damage to other satellites!

Worried Stapler said at October 31, 2011 12:28 PM:

4 words:

When no one is looking, we'll carve our names into roads in China.

Larry J said at October 31, 2011 12:38 PM:

A single burn causing a random change in orbit is most likely going to result in a more eccentric orbit, so the object swings both further away, and closer. An oval orbit that crosses the more circular, original orbit in four places. The sides of the oval will be closer to atmo so the object will eventually deorbit sooner.

If the plasma jet is in the opposite direction from the velocity vector, it will decrease the object's velocity slightly. This will lower the object's orbital perigee 180 degrees away from where the energy was applied. It won't raise the apogee. If you lower the perigee enough, the object will experience increased drag from the very thin upper atmosphere. That will cause it to lose more velocity, lowering the apogee. Depending on the perigee altitude, atmospheric density and the object's mass, you could substancially increase the decay rate.

Shooting from the Earth's surface, the plasma jet may not be exactly opposite to the velocity vector but it could be close enough. Small objects are likely to be tumbling, making it difficult to control the direction of the plasma.

Engineer-Poet said at October 31, 2011 1:50 PM:

The plasma will jet off essentially normal to the illuminated surfaces, which will be substantially along the vector toward the incoming pulse.

Dewage said at October 31, 2011 3:07 PM:

Many smaller objects of space junk spin, yaw and roll at highspeeds. Getting a plasma jet that exerts predictable thrust would have to be very brief and hit a surface that wasn't an edge, or the plasma blast would disspate.

Engineer-Poet said at October 31, 2011 4:02 PM:

The jet will last microseconds.  The laser pulse will more or less push the illuminated object, so any vector where the object is approaching the laser at a reasonably small angle will do.

Bob said at October 31, 2011 4:54 PM:

Wait a minute, don't we have a 747 some where (maybe in mothballs by now) with the basic equipment need to do this. Seems like they have even done some dynamic testing.

Tom Billings said at October 31, 2011 11:49 PM:

Many of the comments here are correct. The key is using the laser to de-orbit a piece of junk by hitting it on its instantaneous frontal aspect at the moment the beam strikes. Notable here is that the reason this is effective is that a plasma shock wave propagates perpendicular to the surface it is blasted from.

That means the average vector will be backwards along its orbit, decelerating the object, and allowing its far-side-of-the-Earth perigee to drop into the atmosphere, where it slows down more and burns up, or re-enters. This could be enhanced by having a spacecraft with a large mirror system in an appropriate orbit. It would concentrate the beam on the frontal aspect of the body, and target it better than could be done through the atmosphere directly. This would be superior to a vehicle assigned to go out and de-orbit bodies itself, because it could target *many* objects from an orbit that need change only slowly, and could be done by ion engines, while maintaining a high rate of orbital clearance activity through the long ranges it can target objects at.

There is also a *large* problem.

The very versatility of this concept scares those who are terrified of the budgetary consequences of demonstrating a key technology that could be expanded for Ballistic Missile Defense. Once the US drops its present anti-industrial policies, and restarts its economy, it can support such efforts easily,....but other countries cannot do so at all easily. There would be much opposition from those who desire the US to *not* advance technically in areas that would give it strategic superiority.

Surellin said at November 1, 2011 5:08 AM:

SDI lives!

Abelard Lindsey said at November 6, 2011 4:22 PM:

A Wired piece reports on a proposal to hit space junk with lasers to cause plasma jets that will de-orbit the junk.

This can be done annually where it would be called annual sky-clearance day. It could be a national holiday with a Marti-gras carnival in every major city, sponsored by Apple and Google (Zig Zak Corporation).

Anyone remember M-m-max Headroom?

Engineer-Poet said at November 6, 2011 6:01 PM:

If only there were enough small junk pieces to make a decent artificial meteor shower when we deorbited them!  On second thought, I'm glad there aren't.

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