DARPA Wants A Few Good Space Debris Cleaners

Shame on you, DARPA! You're thinking in reverse.

You don't need a space junk cleaner, because cleaners tend to suck like a vacuum. You need a space junk pusher!

My solution is a spiraling vehicle that pushes space junk ahead of itself--think of a space equivalent of a bulldozer that never comes back. This vehicle is launched into orbit, and there it deploys a massive basket-shaped appendage ahead of it. Using predetermined coordinates, it pushes outward from the Earth's gravitational pull, gathering bits of space debris ahead of it that are moving with it as it leaves orbit, not against it because that would cause a catastrophic collision. As the net collects slower-moving debris and pushes it forward, the "net" uses small hooks, magnets (although a lot of space debris probably won't stick to a magnet because they tend to use a lot of aluminum alloys), grabbers, and adhesives to hold on to the debris--it's not just the big items, but the nuts and bolts we have to worry about as well.

Once the device has cleared orbit, and effectively cleared the path ahead of it, a second stage rocket fires, pushing it away from the Earth at a rate that will prevent it from falling back into orbit. Affix a warning beacon and let the device push away from the Earth at a leisurely pace.

By launching forty to fifty of these vehicles, we could pre-program a fairly extensive cleaning operation that would allow everyone who tracks space debris the chance to assess whether or not the Rogers Spacejunk Debris Pusher (RSDP) is effective. Start with the tough stuff first. If it works, order up a few hundred more and commence to cleaning the skies above.

Problem solved, and DARPA, I'm wealthy. I don't need the money. Have a pizza party on your uncle Norman.

I'll post some diagrams in a bit on my website, if I stop having a life.

-------------
http://www.anamericanlion.com/

that or we could make a big rocket-fist that punches satellites out into space

I think the devil in this issue is scale. No net, basket, or whatever is going to "sweep" an area miles thick and several times the surface area of Earth (surface area of exspanding spheres). What is needed is percise removal.

Forget the big stuff. There isn't that much of it, and it is easy to avoid. It is the stray screw or nut that punches holes in stuff.

A small UAV (I guess it would be a USV up there) about the size of a shoebox, could hold enough propellant to reach and match the orbit of several small items or one basketball sized object. It would then pick them up or attach to it. Once loaded or attached, it would use its remaining propellant to put it in a sharp orbit down into the atmosphere (burning UAV and load to nothingness). Hundreds of these (they would not need to be heavy, using simple compressed gasses as propulsion) could be taken up in a single rocket payload (reducing cost).

Each one could be remotely controled from the rocket to its target(s), and then to its destruction. Any duds would remain in the rocket bay (to return to Earth, or for its own planned atmospheric demise).

A thousand of these, mass produced at a thousand dollars each, on a single rocket, at two pounds each, worked over four years to catch up with and remove debris, with 20 nerdy tech operators, removing an average of two pieces of junk per unit would only take 40 years (less with simultaneous missions) or 10 missions, each of which would cost no more than a typical manned space flight.

@ NormanRodgers,

Your "RSDP" concept is an interesting idea.

However, it may not be mechanically sound. PLease follow the math on this.

If a 1 gram paint chip were to separate from the ISS it would have an orbtal velocity of 7.65Km/s (Vp), to push it into intraplanitary space it needs to have a radial velocity of 11.2Km/s.

If the RSDP were to follow a spiral path, it would encounter debris heading both with and against it's path, if we assume the RSDP heads directly away from the surface, we will reach a lower than accurate impact energy equation but we will geatly simplify the math.

We will need to find the impact energy of the paint chip against the collecting basket to find out if it could be mechanically sound.

Our assumptions are:
Velociy of RSDP = 11.2km/s (Vrsdp)
the path of the RSDP is perpendicular to the path of the paint.
the impact is plastic (inelastic)
the mass of the paint is negligable relative to the mass of the RSDP.

Here goes:
the relative velocity of the paint and the RSDP is
Vr = sqrt(Vrsdp^2+Vp^2)
thus Vr = 13.563 km/s

the impact energy of the paint Ep = (0.001Kg)*(Vr^2)/2
thus Ep = 91.981KJ

Conclusion: the energy of the paint relative to the RSDP is 92000joules. This is seven times the energy of a 50-caliber anti-tank round.

The enegry will scale linearly with the debris' mass at a ratio of 9.1981x10^7 J/Kg.

Your idea is sound but perhaps an angled surface which would deflect the debris into successivly higher orbits (until outside geo-stationary orbit) would be more feasable.

I don't have time right now to run the math but feel free to post it

So please consider the Kootz Space Debris Deflector (KSDD) to be your main DARPA challenger ;).

Respectifully
-Austin Kootz

Edit to previous post,

After due consideration, The KSDD has been revised to deflect the debris down into the atmosphere. This will allow the KSDD to use the energy imparted by each deflection to boost itself into a higher orbit. This reduces the energy required to spiral out from earth and removes the undesired effect of debris in intraplanetay space. Also not needing to reach escape velocity increases the number of deflectors that can be launched per rocket.

-Austin Kootz

Mr. Kootz,

Thank you for the math. However, you're missing an essential element of this plan--the device pushes an object moving slower than it is traveling. It cannot collide head-on with an object, it will blow a hole clean through anything it strikes. By increasing speed to push objects rather than hit them and snag them, the device becomes a formidable pusher of material. Given that objects in high orbit are already traveling at high speed, this is essential to remember. Do objects move at differing speeds if they are not under their own propulsion or has gravity locked them into speeds based on what they were traveling when they went into orbit? I have several people now trying to research this for me.

I did some calculations--a basket 50 square meters in size making a minimum of 72 passes through known debris fields, shifting that path on a spiral outward into deeper space would clear a fair amount of space, although I can't figure out the numeric value because I simply cannot find the solar powered calculator that I use for science and business calculations. I have calculated on paper that each RSDP would clear 3,600 square meters--a sizeable clear "lane" through the orbit path of the skies above where valuable satellites could be moved to or situated.

There would have to be a minimum of at least fifty of these devices, which would clear safe passage highways above, amounting to a safe belt approximately 180,000 square meters in size (I hope that's right). The vastness of the amount of territory convered in debris is almost unimagineable, I grant you. What we should pursue are lanes where debris is to be cleared or removed without bothering with the extra cost of clearing areas that are already fairly saturated with material. Much of this material is going to come down and burn up safely anyway.

Oakspar77777, I gave your idea some thought, and it would be workable if the devices were programmed to avoid "friendly" debris, as my device would be programmed. My device would only clear those identifiable "lanes" that do NOT contain working satellites.

-------------
http://www.anamericanlion.com/

And let us not forget about recycling said debris. It's not like there is dirt and rusty scrap metal floating around up there. We are talking about reusable metals and expensive equipment. Any cleanup effort concept should have recycling as a goal.

Re: NormanRodgers

You are correct that by increasing the speed of RSDP you will avoid impacts from behind, however: though the debris in front of the basket will be moving at a uniform speed (neglecting ellipsoidal orbits) the debris will not be moving in a uniform direction.

It is true that some debris (perhaps even a majority given a well chosen path) will be moving parallel to the RSDP. However there will also be debris traversing the path at angles, to include vectors directly opposed to that of the RSDP. These are the pieces of debris which may harm the spacecraft, as the kinetic energy density of the debris will increase with the angle (theta in radians) between the debris vector and the vector of the RSDP.

Kinetic Energy Density = (Vorbit^2)*(2*theta/pi)^2

This means that the debris energy will vary from zero (parallel) to a maximum of 4 (opposing direction) times the energy of the previous calculations. If you are primarily interested in clearing a lane for spacecraft to use, perhaps some manner of redirecting the debris which does not require as much impulse from the RSDP to remove it from the lane would be worth investigation.

As to the speed relative to the orbit (for circular orbits)
V = (Mass of earth)*(Gravitational constant) /(Radius of orbit)

-Austin Kootz

p.s. Your thoughts on removing the chance of a rearward strike agianst the KSDD are appreciated. :)

the scale of this is so immense! It would be way to expensive to send a craft(s) to all but the largest intact orbital debris. We know where those are, and they are the easiest to avoid. The problem is all the small junk from the size of a paint fleck and up. There will always be more of it, and all you could ever hope would be to clear and maintain a small safe route, if at all.

The only solution that could be feasible would be and earth based laser system that could slowly scan the skies and pick off debris surgically piece by piece.

We know what most of objects would be made of. It might well be probable that vaporizing small material or even decaying the orbits of some debris could be done with such a system.

It may not work with debris larger than a basket ball for example. It may only destroy part of it and leave the rest in several more pieces. Maybe the laser could be focused into a beam of larger radius/less energy to push these type of objects? Would a light vapour trail extruding from targeted objects be enough?

Edit to previous post

The orbital velocity equation should be:

V = ((Mass of earth)*(Gravitational constant) /(Radius of orbit))^(1/2)

This equation assumes negligable relative mass for the object.
-Austin Kootz

@Oakspar77777

I like your idea. One improvement I would suggest is that the USV be able to send the debris to its fiery demise without leaving orbit itself.

Using your calculations, if 1,000 were produced, (say for example a tungsten-carbide deflector blade to a beryllium cased guidance/propulsion system) could each be plotted by those same 20 nerds to intercept 2 pieces of debris per month (or 24 per device per year)(quicker because it only requires a collision and not a docking-type maneuver) would in theory only take 2 years and have a total cost of 1,000,000 dollars.

What do you think?

I'm wondering if we're thinking too small.Intercepting all sorts of materials at various orbital altitudes and velocities is a huge undertaking. My modest proposal is to orbit huge sails of tough materials perhaps a kilometre or more square. Their job is not to catch or trap objects (although that might be nice), but rather to serve as a target for these object, as a means of reducing their kinetic energy via multiple collisions. Of course holes will be punched in them, but my hope is that subsequent orbits and more collisions with a sail, more energy will be sapped. Orbital altitudes will change, hopefully these objects will drop towards earth, finally burning upon re-entry. We can equip these sails with warning beacons so we can trace them and dispose of them later. This may require a short moratorium on new launches as we don't want accidents with legitimate orbiting vehicles.

Much easier: put giant aerogel blocks into orbit (created by small vehicles in swarms, etc.) Let them impact debris and absorb it. (Same stuff as used in the comet debris-collection spaceflight.) As time goes on, the huge surface area/mass ratio of the aerogel blocks will ensure their orbits decay, and that they and their embedded passengers burn up in atmosphere.

They would be large and obvious when orbiting, and hence easily evaded by spacecraft, etc. If necessary, tiny maneuvering rockets or ion engines could be embedded in them to keep them from intersecting satellites etc. which can't avoid them on their own.

Well why dont they take the idea of the robot that eats material to make energy apply it to a engine that can move in space and bam a metal eating robot that does nothing but move around our orbit cleaning up debri to move sort of thing. When NASA or any other space agency is done with a sat or station or anything send a message to the junk eating robot to intercept it and done and done.

some sort of elektromagnet could do the trick. whenever it gets close to an unwanted particle it could be remotely activated. after collecting the particle you shut down the magnet. after awhile the cluster would be pretty large and at least easier to track than thousends of small cm sized objects, which i imagine represents the biggest threats to safety when spacetravelling

Though I do admit to not knowing much about physics (being only in AP Physics right now); it does occur to me that besides the act of actually dealing with the debris the biggest problem is keeping that vehicle in orbit. Considering the amount of funding going into this anyway, why not consider the moon? By placing some sort of system that pushes the debris into a terminal trajectory on the moon that problem is eliminated. Once several are placed on the moon it would be as simple shooting targets, well for NASA anyway.

Building on mauriceg's idea NASA could adopt the practice of leaving as much large debris as it can in orbit at a trajectory that will cause them to collide with as much as possible. They could even go as far as to make modifications to the parts so that they serve this purpose better. Once these bulldozers have served there purpose they could be much more easily be moved into a new orbit or into a terminal one then any of the smaller stuff they handled.

These are just my thoughts and not based on anymore scientific knowledge or numbers then a high school student can have. If my ideas are fundamentally wrong or impractical please don't just tell me so but tell me how they could work at all.

Redwarrior

I have the simplest idea yet. Pump a huge amount of gas into the orbits of most of the debris. The gas will be much more likely to collide into the paint flecks than a small sail, and will incrementally slow down everything in those orbits and force the them to return to earth. The gas will eventually slow itself down and fall back to earth to.

I recommend magnetic catchers. then take the materials gathered to a prefab station and recycle them. A great deal of the cost of space exploration is getting the material up there.

So if you can recycle what is up there you will take care of multiple issues simultaneously.

A win win if you will with reduced waste and reduced future cost.

For the design use a solar charged ultra capacitor powered electromagnet surrounded by replaceable aerogel panels. Unlike the gentleman above I am poor and would appreciate either $ or a job making cool things like this.

Laser.
Not to blow stuff up, but to slowly push them back down to earth. Not a fast solution, but does allow for precise targeting. Would likely be more effective on the small stuff than big.

I'm surprised no one has mentioned a device that could magnify the suns rays to burn objects or alter their orbits. Something along the lines of a giant hand holding a magnifying glass, should be sufficiently simple enough to get the support of congress.

This problem is something that will need a lot of time to solve and there is not yet a right answer, magnets may grab medals but a chipped off pieces of paint and other non-medal items will not be attracted, a bulldozer will be knocked off track each time it hits and if hit from the wrong direction it to becomes more pieces of orbiting space junk although thats the right concept, some kind of flyswatter to knock things out of orbit. The big sail idea, well he said himself most objects the will punch holes clean through but won't that cause more small pieces as pieces of the sail are fractured off, so i think the slow capture of each piece or the laser idea (if possible) will work best, other wise there will need for too much steering and that needs more resources per craft. A laser from earth pushing objects away from earth to be lost deep in the black, or a laser on the new station they are planning to make on the moon using lasers the push stuff into earth to be burned seems the most effective way and the larger items captured and recycled. Thats my guess at the issue but theres got to be a better way.

Gas would dissipate quickly in the vacuum of space. If, how ever, you launched, for example, a 20 ton tank of water into a high eccentricity orbit and sprayed the water out it would form a large cloud that would slow down the small, untrackable particles that are most common and most dangerous to operating satellites. These particles would slow down enough to drop out of orbit. The other methods I've read all involve targeting individual objects which only makes sense for large spent stages and old satellites. They would be very high tech, very expensive. A big tank of H2O would be low tech and more affordable.

Lets just focus on man-made fusion power. Then we will be able to meet our power needs way better and have extra power to do these other small things. We also need to harness our energy more effectively. Just having the power means nothing unless you can harness it correctly.