Japanese space lasers aim to clean up orbital junk A Japanese biz wants to remove debris from Earth orbit by using a satellite-mounted laser to decelerate an object such as a defunct satellite so it gradually descends towards the atmosphere and burns up. Orbital Lasers is a startup backed by Japanese satellite operator SKY Perfect JSAT as a space debris removal service. If all …
I'm curious how much of a concern will be created by the abladed material. At least the defunct satellite is observable and (hopefully) predictable.
(I suspect that if I asked that of the men and women working on this system, exactly zero of them would respond by slapping their forehead and exclaiming "holy crap Mr. AC, we never thought of that!")
"(I suspect that if I asked that of the men and women working on this system, exactly zero of them would respond by slapping their forehead and exclaiming "holy crap Mr. AC, we never thought of that!")"
I suspect you're right.
Laser ablation is vapourising the surface of the material, so what's left in orbit is probably mostly individual atoms - which aren't that much of a concern.
Additionally that ablated material is exiting the target satellite at some significant velocity (since it appreciably changes the orbit of the much more massive target) and will therefore end up in an interesting elliptical orbit which keeps it out of trouble most of the time (assuming it isn't simply accelerated to escape velocity)
The laser isn't destroying the space debris/junk, it's causing it to decelerate so that it burns up in the atmosphere. So, it probably (famous last words?) wouldn't have the power to reach the surface and/or do any significant damage. And of all the various governments of the world, Japan is probably one of the more trustworthy on this particular front. Post-WWII they've banned themselves from having any kind of offensive military force.
The laser is strong enough to vaporize the surface of the space debris/junk. These gasses then excert forces on the space debris/junk, resulting in acceleration / deceleration.
The force of the laser light alone is miniscule.
So, yes, some care must be taken with the aiming. I can easily see such a laser being mis-used to damage parts of functional setelites.
This has been the fundamental objection to laser brooms (terrestrial or space-based) since they were proposed - along with virtually all other manouverable "deorbiting" systems
If you can bring down junk you can also bring down satellites of those "unfriendly" to you
Despite the need, spacefaring nations still won't agree to a jointly operated facility with strict oversight - the politics just keep getting in the way
You can knock down or at least damage stuff that's supposed to be there.
You think China will be happy that Japan has this capability? What would our reaction be if China or Russia did, or worse Iran or North Korea?
Now maybe the US/China already have something like this, no one is going to make that public if they can avoid it. But the more countries that have this capability, the more likely it is used and causes warfare to move to space. Which would create a LOT more orbital debris that needs knocking down...
Again, per TFA, this isn't a laser that's going to vaporize the debris -- at least not directly -- it'll just cause it to lose some speed so that it falls out of orbit and burns up in the atmosphere. Which probably will give it an upper limit on how big a bit of debris it can presumably knock out of orbit. It's probably at least within the realm of possibility that it could be used to cause a functional satellite to be moved out of alignment, maybe even crash into another satellite, but this isn't some Bond villain style weapon where they can blow shit up in space or be used to target cities in an enemy country. We already have terrestrial rockets that can destroy satellites in orbit which would cost a lot less. Think it was China just blew up a satellite with one of these a year or so ago.
They can't have a laser sufficient to slow something down enough to lose orbit via photon pressure alone that can't also damage sensitive items like cameras, solar panels, dish antennas and so on in working satellites.
Additionally, if it can knock a failed satellite out of orbit via photon pressure, it can do the same to a working satellite. It might take longer since the working satellite has propellant it can use to boost its orbit and make up for the momentum it is losing, but if you keep it at it'll run out of fuel eventually. The "attacker" will always win that battle since it isn't using propellant for its "attack".
Light has pressure, and anything in low-Earth orbit will spend around half its time exposed to the Sun. How about
1) Using mirrors to aim sunlight at selected pieces of junk
2) darken one side of a piece of junk, so sunlight will produce asymmetrical thrust
In either case the goal is to steadily reduce the object’s orbital velocity until it falls from orbit and burns up in the atmosphere. Of course this may take time, but a few days or weeks should be enough.
"2) darken one side of a piece of junk, so sunlight will produce asymmetrical thrust"
I like it. How hard would it be to do this before launch? Paint it like the Crookes radiometer. It could be small enough to not disrupt normal operations, just an attitude adjustment so the radiometer applies thrust in a benign direction. But once the onboard power dies, the adjustment goes away and the passive drive destabilizes the orbit. Again, a tiny thrust applied over years could do the trick.
Oh yes, let's have millions of tiny soot particles in LEO that are impossible to track. You may laugh and think a tiny soot particle can't do anything, but if a satellite in a different orbital pattern encounters a soot particle with a relative velocity of 10km/sec it'll cause damage. If it encounters a whole field of soot particles its solar panels may become unusable in an instant.
Sunlight instead of the laser isn't a bad idea. Why convert light to electricity and back if you can just reflect and focus it. Darkening one side is not so promising for a couple of reasons. Hitting a metal surface in a vacuum is likely to just melt it, rather than blacken it, and most of this junk is tumbling so the dark side would, on average, do nothing. The article talks about ablating the surface to provide thrust, which seems more viable.
I presume it's going to take many minutes or hours of ablation to make any meaningful change of momentum on the orbiting target.
Surely that means you'll have to pretty much match orbit with the target, and sit right alongside it? This implies burning lots of propellant to keep wandering over to each target in turn.
And if you're going to get that close, maybe it's more efficient to have a supply of small rockets which you attach to each piece of debris in turn.
I, too, don't like the idea of lasers which are powerful enough to vaporise steel or aluminium over hundreds of metres, being pointed downwards at the Earth.
"Surely that means you'll have to pretty much match orbit with the target, and sit right alongside it?"
The quality of the laser focussing and stability of the aiming are pretty much the only things affected by distance. There not much else in the vacuum of space to degrade the laser power over distance.
This post has been deleted by its author
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Just how long will this laser satellite need to be targeted on a single item of junk to de-orbit it? If it's less than a few hours, perhaps the system would be workable. If it's a few months, then it would be hopelessly impractical.
I'm disappointed not to read such things in the Register.
This proposal isn't new and it's much easier to provide the necessary laser powwer from terrestrial sources
https://en.wikipedia.org/wiki/Laser_broom
Apart from the obvious (bringing down individual sats), a laser broom can bring down small debris by illuminating the known paths of such things - satellite-mounted lasers will have trouble coping with the 1-5cm range of sizes
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