Swiss craft janitor satellites to grab space junk

February 15, 2012 By JOHN HEILPRIN , Associated Press
A handout image released by Swiss Space Center shows an artist's impression of a CleanSpace One satelite chasing a piece of debris. The Swiss Space Center at the Ecole Polytechnique de Lausanne (EPFL) announced today the launch of CleanSpace One, a project to develop and build the first installment of a family of satellites specially designed to clean up space debris.

The tidy Swiss want to clean up space. Swiss scientists said Wednesday they plan to launch a "janitor satellite" specially designed to get rid of orbiting debris known as space junk.

The 10-million-franc ($11-million) satellite called CleanSpace One - the prototype for a family of such satellites - is being built by the Swiss at the Swiss Federal Institute for Technology in Lausanne, or EPFL.

EPFL said Wednesday its launch would come within three to five years and its first tasks are to grab two Swiss satellites launched in 2009 and 2010.

The U.S. NASA says over 500,000 pieces of spent rocket stages, broken satellites and other debris are being tracked as they orbit Earth.

The debris travels at speeds approaching 17,500 miles per hour (28,000 kilometers per hour), fast enough to destroy or inflict costly and time-draining damage on a satellite or spacecraft. Collisions, in turn, generate more fragments floating in space.

"It has become essential to be aware of the existence of this debris and the risks that are run by its proliferation," said Claude Nicollier, an astronaut and EPFL professor.

Building the satellite means developing new technology to address three big problems, scientists say.

The first hurdle has to do with trajectory: The satellite has to be able to adjust its path to match that of its target. EPFL said its labs are looking into a new ultra-compact motor that can do this.

Next, the has to be grab hold of and stabilize the debris at high speeds. Scientists are studying how plants and animals grip things as a model for what would be used.

And, finally, CleanSpace One has to be able to take the , or unwanted satellites, back into Earth's atmosphere, where they will burn on re-entry.

Swiss Space Center's director, Volker Gass, said it hopes to someday "offer and sell a whole family of ready-made systems, designed as sustainably as possible, that are able to de-orbit several different kinds of satellites."

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1.6 / 5 (7) Feb 15, 2012
Why not put something up that would deflect the space junk back at earth, make it steerable and have a very dense and hardened wedge shaped nose. Items would bounce off the nose and be nudged back into lower orbit for burn up.
2.6 / 5 (5) Feb 15, 2012
It's too bad you can't operate a vacuum cleaner in a vacuum.
3 / 5 (4) Feb 15, 2012
Actually, since space is a vacuum, and this craft is supposed to clean it up, then isn't it a "vacuum cleaner" by definition?
1 / 5 (1) Feb 15, 2012
feldagast...that 'very dense' nose would cost a fortune to put into orbit.
1 / 5 (2) Feb 15, 2012
Why not put something up that would deflect the space junk back at earth, make it steerable and have a very dense and hardened wedge shaped nose. Items would bounce off the nose and be nudged back into lower orbit for burn up.

your idea makes no sense
5 / 5 (3) Feb 15, 2012

The reason you cant do that is that a material hard enough to do this does not exist. You cant just sit in the path of some debris and bounce it back to earth. Even if you were to close the velocity gap just enough to survive the collision, there is this thing called conservation of momentum, so after each bump you would have to burn a bunch of propellant to maintain the same orbit.

If you catch up to a piece of junk, you can just attach a tether to it, and move on to the next piece of junk.

Before any of this is practical though, we need a fuel depot and spacetug/refueling sats in orbit. otherwise one space "vacuum cleaner" could only deorbit a few pieces of junk before needing to deorbit itself.
3 / 5 (2) Feb 15, 2012
I really dont see the point of collecting all the junk. each piece they grab increases the fuel cost of getting to the next one. There are excellent tether systems that have already been tested for deorbit capability, and each tether placed would actually make it easier to get to the next piece.

Any space junk cleanup needs to start with a comprehensive policy to prevent new junk by adding deorbit capability to anything that reaches orbital velocity. Otherwise you just chase your tail all day long. After we stop making the problem worse we can then focus on cleaning things up.
5 / 5 (5) Feb 15, 2012
If you catch up to a piece of junk, you can just attach a tether to it, and move on to the next piece of junk.

Pieces of junk are hundresds or thousands kilometers apart. You have any idea how much tether you'd need to lug along? or what the differential speeds between pieces of junk is - especially if they don't orbit in the same plane?

Why not put something up that would deflect the space junk back

That's not how deorbiting works. If stuff collides (providing you don't produce many more shrapnel pieces in the collision) then all you do - at best - is minimally decrease the orbital velocity of one while increasing the obital velocity of the other. This simply alters the orbit of both a bit. It does not reduce the amount of debris in orbit at all (unless you can get one of the pieces so low where it interacts with the atmosphere)
1 / 5 (1) Feb 15, 2012
Even with a tether system one would need rockets for maneuvering, but the tether would work for deorbiting targets. Sneak up on the target and attach the tether. Tighten it and rotate the combined vehicle. Done properly, the total momentum remains the same, but some is transferred from the target to the janitor. That moves the target into a lower orbit, where it burns up, and the janitor into a higher orbit. Release the tether from the target and reel it in for reuse. You could arrange the maneuver to send the janitor to the next target at the same time, but an ion drive would be easier.
5 / 5 (1) Feb 15, 2012
Do the math on that. You'll notce that that isn't nearly enough to deorbit a piece of debris. At best it gets it to a few km lower orbit (which is worse most of the time, since the most expensive piece of equipment up there - the ISS - is in low Earth orbit)
not rated yet Feb 15, 2012
Pieces of junk are hundresds or thousands kilometers apart. You have any idea how much tether you'd need to lug along?

You have misunderstood me. The tether is only attached on one side. Think streamer. but the drag is actually electrodynamic.

1 / 5 (1) Feb 15, 2012
antialias_physorg: Depends on how fast you rotate it and the length of the tether. A tether could easily be a hundred meters long, and that will transfer quite a bit of momentum. Also, if done right, it will leave the target in an eccentric orbit, with the target's perigee well below the average orbital altitude. There have been serious proposals to use orbiting tethers to launch interplanetary missions, but that is far beyond anything we could do with a small satellite.
5 / 5 (1) Feb 16, 2012
A tether could easily be a hundred meters long

Have you done the forces calculation on that? Do it. Then calculate the weight of a tether that long that can withstand that kind of force. Then calculate the amount of fuel you need to get that thing in orbit and lug it around all kinds of orbits (including the spinning maneuver). Then calculate the weight you need to have a secure gripper/release mechanism that can hold onto an object of UNSPECIFIED GEOMETRY AND SIZE at those forces and release it with high precision.

See on how many levels this idea falls apart? And that's only what I could come up with while typing. If I give this a minute more thought I can probably tell you a dozen more reasons why this isn't a workable solution.
1 / 5 (2) Feb 16, 2012
The space plow idea I was thinking of would be for the very small items that you wont be able to tether. Under 1 inch in size and would change their trajectory into a lower orbit and hopefully into the atmosphere. Sure the plow would have to be controlled and adjusted after impacts and its lifetime would be limited because of fuel, but I think it could be an answer for the tiny pieces up there.
1 / 5 (1) Feb 16, 2012
antialias_physorg: No, I prsonally haven't done the math, but others have.

Shuttle TSS-1 Mission: "This mission discovered a lot about the dynamics of the tethered system, although the satellite was deployed only 260 meters (853 ft) of the 20 km proposed amount due to mechanical problems. A protruding bolt[3] due to a late-stage modification of the deployment reel system, jammed the deployment mechanism and prevented deployment to full extension. Despite this issue, the results conclusively proved that the basic concept of long gravity-gradient stabilized tethers was sound. It also settled several short deployment dynamics issues, reduced safety concerns, and clearly demonstrated the feasibility of deploying the satellite to long distances.[1]"

1 / 5 (1) Feb 16, 2012
SEDS I: In 1993 and 1994, NASA launched two "Small Expendable Deployer System" experiments (SEDS-I and SEDS-II), which deployed 20 km tethers attached to a spent Delta second stage. The first fully successful orbital flight test of a long tether system was SEDS-1, which tested the simple deploy-only Small Expendable Deployer System. The tether swung to the vertical and was cut 1 orbit after the start of deployment. This slung the payload and tether from Guam onto a reentry trajectory off the coast of Mexico.The reentry was accurate enough that a pre-positioned observer was able to videotape the payload re-entry and burnup.

1 / 5 (1) Feb 16, 2012
SEDS II: SEDS-2 was launched on a Delta (along with a GPS Block 2 satellite) on March 9, 1994. A feedback braking limited the swing after deployment to 4°. The payload returned data for 8 hours until its battery died; during this time tether torques spun it up to 4 rpm. The tether suffered a cut 3.7 days after deployment. The payload reentered (as expected) within hours, but the 7.2 km length at the Delta end survived with no further cuts until re-entry on May 7, 1994. The tether was an easy naked eye object when lit by the sun and viewed against a dark sky.[15]

In these experiments, not only were tether models verified, the tests successfully showed that a reentry vehicle can be downwardly deployed into a reentry orbit using tethers.

1 / 5 (1) Feb 16, 2012
TiPS: The Tether Physics and Survivability Experiment (TiPS) was launched in 1996 as a project of the US Naval Research Laboratory. The tether was four kilometers long. The two tethered objects were called "Ralph" and "Norton". TiPS was visible from the ground with large binoculars or a telescope and was occasionally accidentally spotted by amateur astronomers. The tether broke in July 2006.[17] This long-term statistical data point is in line with debris models published by J. Carroll after the SEDS-2 mission, and ground tests by D. Sabath from TU Muenchen. Predictions of a maximum of two years survivability for TiPS based on some other ground tests have shown to be overly pessimistic (e.g. McBride/Taylor, Penson). The early cut of the SEDS-2 therewith must be considered an anomaly possibly related to the impact of upper stage debris.


We actually have a lot of real-world data on space tethers.
2 / 5 (8) Feb 16, 2012
A problem easily solved with photon torpedoes.
1 / 5 (1) Feb 16, 2012
True, but do you want fusion/antimatter explosions in low Earth orbit? Besides the risk of collateral damage, it would seem to be overkill.

Phasers would work better, and a high-powered solar-pumped orbital laser might actually be practical. Vaporizing a small amount of material on the leading end of the target would provide a rocket-like push, slowing the target and dropping it into a lower orbit. Done right, all that would be released is gas and plasma, so secondary debris wouldn't be a problem.

On the other hand, who would control the laser WOULD be an issue, as most countries wouldn't trust anyone else to run it...
not rated yet Feb 18, 2012
antialias_physorg: No, I prsonally haven't done the math, but others have.

Did you even read your own link? This has nothing to do with what you proposed.

Reeling out a large line in LEO is not the same as.

- Moving a huge mass of cable repeatedly all over orbit(s)
- Securely attaching said mass to various irregularly shaped obejcts
- SPINNING the resulting object up to huge forces
- releasing with precision
- rinse, repeat hundreds of times before the teher and its craft become space debris themselves

Space (even orbital space) is BIG. Velocity differentials needed to deorbit something are HUGE. Get that into your head.

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