Laser evaporation for orbital debris removal?

[TimePeriod]

A little question which has been bothering me today, could you potentially use a laser to cause an object to move?

My logic is most likely flawed but I wouldn't mind being disproved. My question is this:

If we took a laser of desired size and power, focused the beam on one side of the object in question, would various atoms from the said object begin to evaporate/burn on the surface? If yes, would it be enough force to be considered a type of propulsion?

My idea continues with multiple laser satellites orbiting the Earth, with each satellite slowly 'pushing' the object into a lower and lower orbit.

The general jest here is not to destroy the object in question but rather get it 'close enough' to our atmosphere, from there the object could de-orbit on its own via atmospheric drag.

Edited September 23, 2015 by TimePeriod

[crestofawave]

cant remember the excact theory here but there was a problem about light and mass, like it has energy so must (potentially) have mass, but the dispute was that it could be used as a bridge but not to move subject matter, allthough you could just destroy it, or indeed heat it to produce a reaction.

i would be interested if anyone can find this theory again, i did have it on file but lost it

[Slam_Jones]

I think I read an article somewhat along these lines a few years ago, except the intent was to provide power to an orbiting spacecraft, allowing vessels to be lighter (due to not having to carry their own fuel or generators) and able to travel further/faster/something like that.

Haven't been able to find it again, could well have been an April Fool's joke.

Sure makes you think, though...

[UmbralRaptor]

This sounds like a laser broom which as best I'm aware could work.

[SargeRho]

Using a laser to push space debris won't work all that well. However, using a laser to vaporize one side of a piece of space debris could produce enough thrust to de-orbit it.

[crestofawave]

yea, the broom was the initial proposed idea, there were some before it but that was the most accepted one, i think it came from beam propulsion, used to superheat propellant,

dam, got me looking for that theory on laser/mass/energy now ...

[Motokid600]

A large ground laser that hit debris coming over the horizon. Just need to loose a very little amount of energy so the debris is pushed into a more rapidly decaying orbit. Even if it takes years after being hit by the laser.

But that's a lot of atmosphere to blast through. I only say a ground based laser because we could make one much, much larger then one in orbit.

[Elthy]

I dont know if its even possible to aim that well...

[maltesh]

cant remember the excact theory here but there was a problem about light and mass, like it has energy so must (potentially) have mass, but the dispute was that it could be used as a bridge but not to move subject matter, allthough you could just destroy it, or indeed heat it to produce a reaction.

i would be interested if anyone can find this theory again, i did have it on file but lost it

Light carries momentum and energy without having mass.

[vger]

I dont know if its even possible to aim that well...

If it is, my telescope desperately needs a new tracking motor.

[Yasmy]

I dont know if its even possible to aim that well...

Aiming is not that hard. For example, we can hit a retroreflector on the moon to measure the Earth-Moon distance. This is not to say that these experiments are easy. They are difficult, but definitely doable.

[PB666]

Using a laser to push space debris won't work all that well. However, using a laser to vaporize one side of a piece of space debris could produce enough thrust to de-orbit it.

Bad idea, you would need a powerful ground laser, remember the laser emmitter is being pushed, so if you attemot to deorbit a probe, the source is going to be sent inot incrasingly highrborbit.

The ground laser does not have high enough resolution, and would prbaly blast the craft to smaller pieces. undesired.

Also lets not forget that space weapons are verbotin.

all in all a bad idea.

Vasimr with a cahin link cage to capture bag and release the junk with a large drag sail.

[SargeRho]

You'd only fire the laser while the debris is coming "towards" you from the horizon, so that the force produced on the space debris slows it down. And space weapons aren't forbidden, only space WMDs are. ASAT missiles are, after all, surface to space or air to space weapons.

[Brotoro]

Sure, it can work.

I wonder how bright the little pieces of space debris would look if you catch a specular reflection off of them from a laser pulse.

[NuclearNut]

You'd only fire the laser while the debris is coming "towards" you from the horizon, so that the force produced on the space debris slows it down. And space weapons aren't forbidden, only space WMDs are. ASAT missiles are, after all, surface to space or air to space weapons.

I wonder, what exactly do they define as a WMD?

It just seems to be such a... buzzword these days, devoid of all meaning other than "weapon more destructive than high explosives" or not even that.

[SargeRho]

Any NBC weapon for starters, so nukes, anthrax, sarin gas, etc. A MOAB could probably also be classified as a WMD, since it's meant to wipe out a large area.

[prophet_01]

Regarding the aiming, the European Data Relay System uses laser communication to link up the satellites in space. So it seems possible to get that kind of precision with a laser between satellites. It's pretty much cutting edge technology, but I don't see severe issues for adapting it for a vastly bigger laser.

There was a large interview on national radio broadcast. The CEO of the company that designed and produced the laser comm system talked about the technology involved and that different military R&D facilities are interested in the design. Quite neat stuff, but sadly it was in german only (still available on the official site of the DLF).

How big would a laser need to be in order to deorbit small debris anyway? The radiators and solar panels for a high energy laser should be quite heavy...

Edited September 24, 2015 by prophet_01

[sgt_flyer]

Tracking an orbital object from the ground is not a problem - even while using lasers

(How else would ISS OPALS work if it wasn't feasible ? https://en.m.wikipedia.org/wiki/OPALS)

- plus, the orbital parameters of dangerous junk are known, so it's even easier - no need to track when you can accurately predict - align on the orbit, and fire at the correct timing (and you can retry at the next orbit)

And you don't even need to fire so a retrograde thrust is generated - an antiradial thrust can also be used to bring the orbit within atmosphere

Though, it's still require lasers of several hundreds of KW - maybe even chemical ones - but still, they'll be easier to maintain, power and cool down if used from earth ground than space based lasers of this kind of power - as for sublimating material through laser heating, it's called laser ablation and it can be quite effective

You can take some infos from randall's what-if about lasers and the moon

https://what-if.xkcd.com/13/

[TimePeriod]

Another key question I've asked myself over and over would be who should be in charge of said project, in terms of controlling the actual laser system, AKA what kind of targets should be picked first, what orbit should be cleaned up, who owns what satellites etc.

[Friend Bear]

The Japanese are the ones experimenting with deorbiting debris via laser. I think it has to do with breaking momentum, not dissolving the target.

- - - Updated - - -

Another key question I've asked myself over and over would be who should be in charge of said project, in terms of controlling the actual laser system, AKA what kind of targets should be picked first, what orbit should be cleaned up, who owns what satellites etc.

It gets complicated (so much so that I cannot say precisely what they are doing but generally the idea since I don't think they even know). All space-faring nations (except North Korea) agree that their debris is their debris, whether privately owned or publicly owned. But countries like Japan and the US are keen on cleaning it all up. While they might leave the mess China made in 2013 with its satellite missile test to them, generally, UN aligned nations are trying to work together on the final outcome, but each are developing their own methods.

The other issue is when a satellite becomes defunct or inoperable/out of date, they do not typically just sit there nor are they retro fired into orbit to burn up. Typically, nations will just send them out to high earth orbit and there is a graveyard of that trash there now. This is because most satellites are either in low, including the ISS, and geosync orbits are really far out.

That being said, I would imagine low earth/mid earth and geo satellites that have not made it to the junk orbit would be the first target. Ideally, so would the Chinese debris.

[More Boosters]

Tracking an orbital object from the ground is not a problem - even while using lasers

(How else would ISS OPALS work if it wasn't feasible ? https://en.m.wikipedia.org/wiki/OPALS)

- plus, the orbital parameters of dangerous junk are known, so it's even easier - no need to track when you can accurately predict - align on the orbit, and fire at the correct timing (and you can retry at the next orbit)

And you don't even need to fire so a retrograde thrust is generated - an antiradial thrust can also be used to bring the orbit within atmosphere

Though, it's still require lasers of several hundreds of KW - maybe even chemical ones - but still, they'll be easier to maintain, power and cool down if used from earth ground than space based lasers of this kind of power - as for sublimating material through laser heating, it's called laser ablation and it can be quite effective

You can take some infos from randall's what-if about lasers and the moon

https://what-if.xkcd.com/13/

How are you going to get that? You'd have to shoot the laser from above the debris.

[sgt_flyer]

Nah - you can shoot them from below too - the laser heating on the bottom of the part will result in ablation ejecting thrust towards the planet (the same as if you made tried to make a burn in KSP to get directly 'away' from the surface. making Radial and antiradial manoeuvers end up rotating the whole orbit with the debris as the center of rotation. (Instead of changing the orbit's opposite point altitude like in retrograde / prograde manoeuvers)

Normal spacecrafts have generally no use for this kind of manoeuver because it's extremely costly in delta-V - but that's not a problem when using lasers on debris.

If you picture your orbit rotating with your spacecraft as the center of rotation, (not talking about plane change here) the orbit will either end up intersecting the planet (or if you can target satellites in geostationnary orbit, potentially getting it into an escape trajectory before the orbit intersects with the planet) - think of the radial / antiradial manoeuvers as something akind to the spacecraft playing hula hoop with it's orbit firing from above or from below only change the direction of rotation. Once the orbit intersects, it does not matter the direction you rotated the orbit anymore

If you want to test, just create a manoeuver node on an orbit in KSP and play with the radial / antiradial controls

[More Boosters]

---

I know what you are talking about, but wouldn't the thrust be generated on the side the laser hits? Which will have to be the Earth-facing side, naturally, sending the piece of debris away instead of closer to Earth.

[Kibble]

Lasers for orbital debris is practical! Low mass objects easily accelerated by light pressure, not having to actually boost anything onto orbit (no potential for additional debris), passively shining into sky.

[sgt_flyer]

I know what you are talking about, but wouldn't the thrust be generated on the side the laser hits? Which will have to be the Earth-facing side, naturally, sending the piece of debris away instead of closer to Earth.

You need to think about the orbital mechanics at play here the debris is in orbit around earth fire at it from the earth surface, and the resulting ablative thrust will effectively be directed towards earth - however, this thrust will result in a radial / antiradial type of orbital manoeuver, the whole orbit will 'rotate' around the spacecraft. At one point, the orbit would intersect with the planet - ok the apoapsis will be farther from earth - but at the same time, if the periapsis has become low enough to go through the atmosphere, when the debris enter the atmo it will start to slow down (if it only pass through the high layers of atmosphere at first) and will end up being delrbited due to drag and will burn during atmospheric reentry.)

edit : here's what doing radial/antiradial manoeuver looks like in KSP (i only tugged at the blue manoeuver node outwards)

i have precise node and KER opened so you can check the orbital parameters (ok, 'besides, it works in KSP' is a corny line, but in this case, it would do the same in real life )

Edited October 4, 2015 by sgt_flyer