Space Garbage Truck Takes Out the Trash

On April 2nd, 2018 a Falcon 9 rocketed skywards towards the International Space Station. The launch itself went off without a hitch, and the Dragon spacecraft delivered its payload of supplies and spare parts. But alongside the usual deliveries, CRS-14 brought a particularly interesting experiment to the International Space Station.

Developed by the University of Surrey, RemoveDEBRIS is a demonstration mission that aims to test a number of techniques for tackling the increasingly serious problem of “space junk”. Earth orbit is filled with old spacecraft and bits of various man-made hardware that have turned some areas of space into a literal minefield. While there have been plenty of ideas floated as to how to handle this growing issue, RemoveDEBRIS will be testing some of these methods under real-world conditions.

The RemoveDEBRIS spacecraft will do this by launching two CubeSats as test targets, which it will then (hopefully) eliminate in a practical demonstration of what’s known as Active Debris Removal (ADR) technology. If successful, these techniques could eventually become standard operating procedure on future missions.

A Dangerous Place Made Worse

Space is an exceptionally dangerous place to be. Anything you put out there must be built to take a beating. Spacecraft have to deal with radiation and massive temperature changes which would render lesser machines into scrap in short order. There’s also the ever-present threat of micrometeoroids, tiny specs of rocks and metal that have been flying through space since the formation of the Solar System.

Some of the larger debris in orbit

But since the 1960’s or so, the area of space that immediately surrounds Earth has become even more inhospitable. Decades of space missions, failed satellites, and even the occasional explosion have left thousands of individual pieces of stuff in orbit. The University of Surrey says that the roughly 23,000 unidentified objects orbiting the planet could have a total mass of up to 6,800 tons. Of course, that’s just the stuff we can track with radar. The number of objects too small to track, stuff like chips of paint or individual loose screws, are estimated to number in the hundreds of millions.

The problem is that each of these objects, from bits of Tiangong-1 to Elon Musk’s Tesla Roadster, are traveling at absolutely mind-bending speeds. Even the most leisurely of orbital pieces of junk will be flying around the planet at roughly 17,500 miles per hour (28,000 km/h). At those speeds, a lone screw is essentially a bullet. An impact with a larger object, say a defunct satellite, would be catastrophic to put it mildly.

As Real as it Gets

RemoveDEBRIS deploying a CubeSat

The RemoveDEBRIS spacecraft will actually be riding to the International Space Station inside the Dragon capsule, but once it arrives it will eventually find its way out of the Station via the Japanese Experiment Module (JEM) airlock. After being jettisoned into space sometime in the next couple of months, it will officially begin its mission which is scheduled to continue well into 2019. The mission will officially end when the RemoveDEBRIS spacecraft dips into the atmosphere and burns up.

But before its fiery end, several technologies will be demonstrated in about as close to a real-world scenario as possible short of tracking down and tangling with a dead satellite. Two CubeSat spacecraft will be launched from the larger RemoveDEBRIS vehicle and used as practice targets for a number of experiments. Given the growing popularity of CubeSat missions, this is an excellent analog for the type of missions which may well become commonplace in the next decade.

Seek and Destroy

Once the first CubeSat is ejected from the RemoveDEBRIS “mothership”, it will deploy an inflatable structure to present a larger target. After it’s moved approximately seven meters away, RemoveDEBRIS will fire a net at the CubeSat in an attempt to ensnare it. The net has weighted balls at the edges which are intended to wrap around the target, and an electric winch cinches the net closed. If successful, this will demonstrate the ability to ensnare a target spacecraft at range, which could be necessary in situations where the target is tumbling or otherwise too dangerous to approach closely.

RemoveDEBRIS will also test a harpoon that can be used to grapple distant targets. This won’t be fired at a separate spacecraft, and instead will make use of a 10 cm x 10 cm target on an extendable boom. Once the harpoon lodges itself in the target, it can be winched back to the spacecraft. This method could be used on smaller targets, where multiple small objects could potentially be harpooned and brought onboard to be deorbited later.

The second free-flying CubeSat to be released will serve as a target to demonstrate Vision-Based Navigation (VBN). Using a combination of 2D cameras and 3D LIDAR imagers, RemoveDEBRIS will autonomously demonstrate a concept known as non-cooperative rendezvous. In other words, the ability to track and rendezvous with a “dead” object. Being able to autonomously navigate visually will be critical when approaching a target that is unable to communicate or maneuver on its own.

First Steps

To be clear, the technologies being tested by the RemoveDEBRIS spacecraft won’t be used to remove speeding screws. These tiny objects are too small to track, and too small to intercept even if you knew where they were. It’s part of doing business in space, and vehicles that will spend any time outside of our atmosphere will need to be designed to take such things into account.

But if all goes according to plan, RemoveDEBRIS could serve as a touchstone for future “garbage truck” missions. In the coming years, we may see similar spacecraft that rove around Low Earth Orbit autonomously knocking out dead satellites and particularly troubling pieces of debris. There’s a certain irony of launching another piece of hardware into space just to pull down the ones we’ve already left up there, but for now this is a good a plan as any.

107 thoughts on “Space Garbage Truck Takes Out the Trash

        1. Nice retro-memory flashback. I remember seeing this on the TV when I was a kid. I didn’t remember Andy Grifith as the lead character. I did remember the cement mixer command module. :-) Thanx for refreshing my memory. (Dynamic RAM you know. :-) )

  1. “Even the most leisurely of orbital pieces of junk will be flying around the planet at roughly 17,500 miles per hour (28,00 km/h). At those speeds, a lone screw is essentially a bullet.”

    Isn’t it true that for anything else to be in orbit, it also has to be doing a minimum of about 17,500 mph? Would that not mean that the debris is going about the same speed, give or take a few thousand miles per hour, as the spacecraft? I suppose this gets really dangerous if on different orbital planes such as some space junk in a polar orbit colliding with a spacecraft in low earth orbit. In time, won’t all of the space junk’s orbits deteriorate and the items fall to earth in sort of a self-cleaning process? Of course, if we keep adding to the junk pile, the problem will continue.

    1. I think the problem they are mentioning is that you may be entering orbit at a different layer thus your velocity will still be more focused on moving away from Earth and not establishing an orbit speed, thus the object would be going fast relative to you (although not 17.5k as you pointed out since even at those stages you are likely moving your orientation slightly).

      I don’t think the risk is as big as this article makes it sound though since space is really really big, even just the area around earth.

      Also sorry admins I accidentally hit report not reply, please don’t delete this guys comment.

          1. also the rightmost button is the preferred action in most confirmation dialogs (macOS, Windows, Android, elementary OS).
            naturally, users will tend to reuse these subtle cues on the web without even noticing. it would be helpful to just comply to those guidelines because they already exist and they have become predictable behavior.

            HaD, you know what to do ;-)

      1. I said that in my comment, ha ha. I would have said one could be launched from west to east (normal) and one from east to west but I don’t think anything has been but into a reverse orbit like that due to the direction of the earth rotation.

    2. The problem is some things can be going in opposite direction. When two things collide at 35,000mph, they can make a lot of debris. Some of this debris will stay in orbit going in both directions, so now you have even more highspeed debris. If this happens too much, we have a Kessler syndrome (

      > In time, won’t all of the space junk’s orbits deteriorate and the items fall to earth in sort of a self-cleaning process?
      Yes, but depending on orbit, this may be several hundred years.

      1. Hey buddy, just an FYI: velocity vectors cancel when they’re in opposite directions. Driving into a brick wall at 60 subjects your remote control car to the same force as getting into a head on with an identical mass RC traveling at the same speed

        1. This all depends Dan on comparative material properties.
          There is huge difference between elastic and in-elastic
          collisions add to that the chance there is any sort of perfect
          alignment is negligible. Though fortunately if the vectors do
          cancel then that collision result taken out of the equation
          in terms of orbital issues as Gravity always wins :-)

        2. Yes, but there are no stationary brick walls in orbit.

          You can be hit by debris going prograde, or retrograde, or sideways on a (semi)polar orbit, or get hit from above or below. The worst case scenario with the highest impact energy is when you’re going in opposing direction to the debris you’re about to hit.

        3. if I’m not mistaken if the objects are approaching from opposite directions and, without taking angular differences into account the velocities are actually additive. I think this you tube link explains it.

      2. Satellites in LEO are almost never travelling in completely opposite directions in a corotating Earth frame – almost no satellites are ever launched retrograde. Even if two objects collide at LEO, they’ll still end up moving in a prograde orbit. The ‘forward’-moving objects (in their center of mass) will be at the perigee of a new elliptical orbit, and the ‘backward’-moving objects will be at the apogee.

        The situation where orbital velocity is really bad is when objects in very different orbital inclinations collide, and considering orbits precess around the Earth fairly rapidly (order(100) days!), that’s where the real danger comes in.

        1. So, when one orbit precesses 180 degrees and you shoot another object at that orbit, objects are still travelling in the same direction? Yeah, MOST object at equatorial orbit are travelling in the same direction. But there are more orbits. And when there is collision, some chunks can have altered orbits.

          1. Sorry, my previous comment should’ve said “in very different orbital *planes* collide.” Obviously satellites at the same inclination can still collide.

            “So, when one orbit precesses 180 degrees and you shoot another object at that orbit, objects are still travelling in the same direction?”

            When they collide, yes, they mostly are. Precession alters the ascending and descending nodes – rotating the entire plane – so all you’ve got there is the component of the orbital velocity that’s perpendicular to the rotation of the Earth. They’re both still rotating prograde, so the majority of their motion is in the same direction.

        2. I believe there have been launches in the more costly direction, too. But think about just objects in polar orbits, there’s no reason they couldn’t be in the same exact orbit going in opposite directions. Also think about objects in a LEO equatorial orbit hitting those in a highly elliptical equatorial orbit falling from their 50000km apogee.

          Also when objects collide their velocities will not normally cancel, they break into pieces, the batteries and electronics heat up to extreme temperatures (may explode and break into more pieces), or continue on their paths but gaining angular velocities of many thousand of RPMs (again may explode from just centrifugal force).

      3. The number of things traveling in the opposite direction is practically nil. There’s very few mission profiles which require a retrograde orbit, and to launch something into such an orbit means you’re working against the momentum inherited from the Earth instead of taking advantage of the free boost. That’s extremely expensive. It’s simply not done.

        Regardless, a collision at any orbital velocity is going to create a lot of debris, retrograde or not. Kessler syndrome is very unlikely without an immense rise in launch frequency, though. Yes, it can happen in LEO where the concentration is highest, but things in that orbit quickly decay which mitigates that risk. As you state the higher orbits last longer, but as you get further from earth the area of the orbit increases according to the inverse square law. Satellites in that orbit, even thousands of them, have virtually zero chance of ever colliding. It’s not like a crowded highway up there. It’s many times more volume than the entire Earth, with only a few thousand tiny specks circling through it. Nothing ever comes even close to another object without extremely precise and intentional rendezvous.

        It’s not like the movie Gravity where they aimlessly float away from one space station and just happen to drift to the Chinese station next door a few minutes later. Jesus that movie was absurd. That movie’s unscientific creative license along with a few dumb TIL posts on reddit are the real reason anyone is concerned with Kessler syndrome.

        1. Envisat’s risk of a Kessler-type situation isn’t negligible, just not high (otherwise someone would’ve done something about it!). The thing’s freaking huge, and it won’t deorbit itself for 100+ years.

          1. I’d say it’s a good definition of negligible if no action is required. That thing has a semi-major axis of over 7000 km. It’s pretty vanishingly unlikely that it will hit anything beyond a couple micrometeorites in the 150 years before it naturally falls.

            With that orbit it also isn’t likely that its debris would hit anything manned like a space station. And since it’s so far out, it probably wouldn’t block all launches and isolate us on the surface like Kessler syndrome predicts. There would still be lots of viable windows.

          2. They haven’t done anything about it *yet*. There are plenty of planned missions targeting it, and the chance of a collision in its lifetime is pretty high. Definitely in the double-digit percent case. It’s only been inoperable for 6 years, after all.

            Kessler doesn’t mean the whole orbital range goes “poof.” In the Envisat case, you’d lose the Sun-synchronous LEO orbits, which would really suck. But other LEO orbits, and of course farther out, would still be viable.

          3. Just to be quantifiably clear, you’re extremely wrong about the Envisat risk. It’s 15-30% likely to hit something over its orbital lifetime. If it had failed earlier in its life (in 2010) it would’ve come within ~50 meters of colliding with a Chinese rocket stage, with about a 1-in-70 chance of collision. 1-in-70 is not vanishingly unlikely.

            It’s also not “so far out”. It’s in a Sun-synchronous, relatively stable orbit at around ~800 km altitude. These are important orbits for observation satellites, and so losing that would be a big deal.

        2. The debris also would not have been threat to TDRS satellites in stationary orbit nor would the station re encounter the debris field every orbit just when their orbits synced up which could be hours or weeks depending on how far the debris have spread and how similar the altitudes are.

    3. The smaller the object (and so lower mass) the longer it takes for it to fall back into the atmosphere…. While large things like China’s satellite come down fairly rapidly, anything small could take thousands of years to re-merge with the atmosphere and burn up…

      1. Really djsmiley2k ?
        So what has mass of the object have to do with the rate at
        which it falls to then “ with the atmosphere..” ?

        Wasnt this issue settled with Galileo and when a hammer and
        feather were dropped on the moon by an astronaut, as well as
        myriad tests in long vacuum pipes at uni’s and research labs ?

        Surely you must have meant cross sectional area in relation
        to volume and not mass – with even negligible atmosphere
        having an effect – as there is no such precise non-atmosphere “edge” ?

        As bear in mind though, that a small and low mass object, is more
        affected by radiative transfer when Sol’s light shines on it which
        is one aspect of incremental change to orbiting objects in all
        rotating/orbiting axes.

          1. Yeah good link Luke for those unclear with the issue,
            hubris can be good though best to review the
            comment which provokes a responder’s reply for
            fuller understanding ie In reply to djsmiley2k :-)

            I was responding to djsmiley2k who plainly suggested mass
            makes a difference Before connecting with atmosphere, here
            is his full comment in case its lost in the ether ;-)

            From djsmiley2k
            “The smaller the object (and so lower mass) the longer it takes
            for it to fall back into the atmosphere…. While large things like
            China’s satellite come down fairly rapidly, anything small could
            take thousands of years to re-merge with the atmosphere and
            burn up…”

            djsmiley2k stating the mass of the object important in
            some unclear way before it encounters the atmosphere. Hence
            my question he’s not addressed as yet. So your reply to me was
            best directed at djsmiley2k as his comment misleading. No problem
            as we got the drift.

            In any case there isn’t any sharp edge of atmosphere and space,
            as its asymptotic and just like our experience of terrestrial winds,
            same happens in & above LEO far more chaotically too in respect
            of ionized oxygen, electric currents and magnetic fields mostly tenuous.


      2. Incorrect. The opposite is true. Small objects reenter MUCH faster than large objects.

        For similar densities and shapes, larger objects take longer than smaller objects due to the fact that volume (and thus mass and momentum) shrinks faster than cross sectional area (and thus drag) does as you shrink the scale of an object.

        1. Yeah, your statement’s a bit confusing. Safer to say that size is just totally the wrong measure to look at.

          Considering satellites aren’t really uniform density or common shapes, it’s easier just to say that drag and radiation pressure are proportional to (area/mass), so for objects with equal surface area, smaller masses reenter faster. And obviously for objects with similar densities, the smaller object will reenter faster.

          But obviously if you’ve got a metal bolt versus a satellite with panels, the metal bolt’s going to have a much lower area/mass, so it’ll stay up longer.

          1. Small objects have more surface area for volume due to the square cube law so the bolt will have more drag even if it is denser than a whole satellite.

          2. No, it really won’t. Not necessarily. Like I said, it’s area/mass. Not density. Not area. Area/mass. Plus shape, due to drag coefficient.

            A satellite with panels could easily have an area/mass ratio larger than a bolt, and it’ll almost certainly have a bigger drag coefficient. Just depends on the panels and how big they are relative to the satellite.

            To take an extreme, look at the ISS, which has an area/mass ratio times drag coefficient somewhere in the 20-30 cm^2/kg range. Approximating even a tiny 3/4″ bolt as a sphere (yes, terrible approximation) you’d be somewhere around 10 cm^2/kg or less.

      3. Nope. Nope nope nope. That isn’t how gravity works. It pulls large and small the same. If anything, a denser object will have more momentum and less drag in the rarified upper atmosphere, so heavy things would stay up longer.

        Regardless, it’s such a tiny difference that it’s not worth a distinction. Nothing in LEO is going to stay up for “thousands of years.” You need a higher orbit for that, and in a high orbit there just isn’t any significant risk of a collision at all. It’s too much space. Even the relatively crowded LEO has extremely low risk.

          1. Even if every little mom-and-pop telecom on Earth put up a constellation, it wouldn’t get crowded at the altitude where effective communication satellites operate.

            It sounds like a big number when we say there’s 23,000 bits of space trash, but this area is much larger than the volume of the Earth. It also looks worse than it is when you have a visualization such as the one in the article above which shows each piece of garbage as about the size of Oklahoma. If there were 23,000 fish in the sea, would you consider that crowded? Because the sea is absolutely claustrophobic compared to this amount of space, even considering the velocities things are moving.

          2. “, but this area is much larger than the volume of the Earth”

            Close. Most of the debris is confined to 500-1500 km altitude, which is about half the volume of the Earth.

            However, this is a horrible comparison. If an automated car dies driving in the US, and one dies driving in South America, there’s no chance of the two colliding. But orbital drift over time means that two satellites in similar situations could easily end up in a collision situation. These things aren’t stationary, and orbits aren’t known perfectly. An object at 1000 km altitude will cross a huge fraction of that “half the volume of Earth” space as it decays.

            Is there a huge risk? No, of course not. Stuff like this is always overblown in pop science. Most satellites deorbit themselves. But whenever you have a satellite fail, it becomes a risk, and so at some point it becomes economical to actively deorbit the large risk objects. And in order to do that, you need to have the technology to do it. Which means you need demonstration missions.

            I really don’t understand your comments – you act as if accidental satellite collisions have never occurred. Of course they have, with the most prominent one being the Iridium-Cosmos collision in 2009 which caused a huge spike in debris along those orbits, and has led to active avoidance by the Space Station of fragments and caused the ISS astronauts to take refuge in the Soyuz due to a collision risk.

    4. Yeah, it would have to rendezvous to capture a piece of trash, which means matching velocity and orbital plane closely. This means that for a practical capture (e.g. rendezvous with a real satellite in the wild instead of a cube thrown out of the ISS airlock, therefore inheriting similar orbital characteristics) it would have to be launched on a similarly-capable rocket as the original satellite.

      This means about the same delta-v, cost, and staging debris from the launch platform. And this is why these space-junk cleanup projects are not practical and really just investor bait. It’s a bit of a public secret. It’s not even remotely cost or time effective. Not within a couple orders of magnitude. And it’s useless anyway, since it would create more space junk.

      If we’re going to capture a significant portion of the 23,000 bits of trackable junk, that obviously means thousands of launches. At this point you might ask why not launch them all in one rocket and let them split up and rendezvous separately in orbit? Or manufacture and launch them from the ISS? That only works if all the targets are all in VERY similar orbits, since the satellite itself has practically nothing as far as delta-v. Most of the delta-v it does have needs to be used to de-orbit its target, which is already doubtful for larger satellites. So we’d be talking about very standard LEO orbits. You’re correct in your post, those orbits decay quickly and that stuff is coming down soon in any case, not needing active disposal. So we’re stuck with thousands of launches.

      Out of thousands of junk-cleanup-bot launches, tons of staging debris are going to get chucked into orbit. Explosive bolts, fairings, paint chips, tiny bits shaking off from vibration and thrust. That’s obviously counter-productive. Also, some of the missions are going to be failures. The bot might stop sending telemetry and become a piece of space junk itself, or much worse–collide with its quarry and turn both itself and the original piece of junk into an expanding cloud of ten thousand bits of far more dangerous junk. The method of shooting a net with dense weights at a spinning satellite is utterly insane.

      This is obviously a wacky contraption meant to get attention, not do useful work. This thing WILL create more trash. Well, it would if it wasn’t so expensive. The truth is this strategy will never be used large-scale beyond a couple of tests. About twice a year a loopy scheme to dispose of space junk is floated in order to get grants and create buzz, which is fine. Space exploration is important and it needs funding, as well it needs a hook to get future generations excited about continuing it.

      The space junk “problem” is overhyped. Yes, Kessler syndrome is technically possible. But most of our stuff is in LEO where it naturally decays quickly, including all of our manned spacecraft. The stuff that’s above LEO is so widely separated that the likelihood of a collision is a statistical impossibility. A shell of space at GEO is utterly huge. It would be like throwing a lego brick in the Atlantic, another in the Pacific, and expected them to eventually snap together.

      1. Well, yeah, I don’t think the net idea is very practical. But having a precise map of a LOT of junk in different orbits, speeds and phases, and a lot of time, you could program a sort of a Travelling Salesman algorithm which would put you on a collision course with each piece of junk such that your new mass and velocity after the collision are on a collision source with the next piece of junk on the list and in theory you could be using little fuel.

        1. You could possibly get to each piece of junk, but how are you deorbiting them? that requires delta-v. And if you want to grab something and decelerate something into a re-entry trajectory, then you are also in that re-entry trajectory, so you either burn up in the atmosphere or spend double delta-v to get back in orbit to find another piece of junk. This thing does not have enough delta-v for any of that. So it’s back to thousands of launches.

          1. Most of this stuff is likely to be small enough that it will burn up completely so we’re already not counting on a controlled deorbit. Heck why not just use some sort of shaped charge?

            Have the garbage bot position itself in exactly the right location then fire a cone-shaped projectile into the debris in question. After that it backs away to a safe distance and triggers the charge remotely. You could design it to be able to fire six charges then head back to the ISS for refill OR deorbit itself. Whichever is cheaper.

    1. It’s true, every mission like this we launch runs the risk of adding more debris in orbit.

      The best option is really to try and knock objects out of orbit with a laser, which is something that’s currently being experimented with. Until that kind of technology is ready for real-world use though, manually deorbiting hardware like this is our best bet.

        1. We can do the next best thing with the laser and also without
          relying on the plasma burst which offers a quicker delta V to de-orbit
          but more slowly and likely far cheaper too…

          ie. If many cheaper lower power lasers were deployed above the worst
          LEO junks then firing at appropriate times which impart radiative transfer
          to offer that push or if approaching to slow them down in their orbit
          so they naturally fall to a lower orbit then taken over by drag,

          Economies of manufacturing scale with coordination and good connection with
          tracking networks, that is, if there was trend to put up more satellites – then,
          depending on their altitude arming the bulk of satellites at the start of their
          design so they work collectively in swarm like paradigm could be the new
          base equilibrium re distributed approach so expensive specialised laser
          satellites may not be needed.

      1. I was wondering if a giant (5km dia) coil pumped with a massive current and flown at an angle could be used to deflect a fast-moving object through it by means of an induced eddy current?

    2. This is exactly what will happen if it’s used large-scale, ESPECIALLY with that gonzo net with bolas and a literal harpoon gun is used. Those techniques are beyond stupid. Why not just go all-in and put a shotgun on it? Or toss a few grenades out the airlock just to make future missions a little more interesting.

      This is a PR mission. They’re trying to inspire laymen who watched the movie Gravity. Which is fine, space exploration needs good PR too. But anyone who pays attention shouldn’t mistake this for a practical technique of eliminating space junk.

  2. The hard part is always matching the orbit of the target so that it can be grabbed or pushed at a reasonable relative speed (instead of violently smashing into it). If it carries several smaller craft that can attach to and give the piece of garbage a gentle push, then it could be viable, as long as each of the little ones (almost nothing more than propellant and guidance) can match a target. If not, it’s horrendously difficult (and propellant-intensive) to match multiple pieces of junk over the life of the satellite.

    Maybe a better approach would be to put a satellite at a higher orbit and use a laser to give gentle pushes to orbiting trash so their orbit decay faster.

    But then we’ll have an orbiting laser with some non-trivial power. Some treaties would need to be negotiated and, maybe, a consortium created to operate it outside any single government.

      1. I wouldn’t expect ablation to be a concern, from what I understand laser ablation vaporises the contact surface. I think the particles coming off would be more of the order of dust rather than paint flakes and screws.

        If you hit it with a really powerful laser with enough beam power however then you could have some issues with globs of molten metal being thrown around. I work on electron beam welders where the welding is done in a vacuum chamber and can confirm first hand that you get lots of tiny bits of molten metal being thrown about when a powerful beam hits a lump of metal. It’s a nightmare to clean off from your nice shiny new vacuum chamber; still I imagine it’s better than cleaning up after a bit of orbital weld splatter hits your nice shiny new spacecraft.

        1. These are very idealistic expectations. No engineer is going to expect only primary effects from that vaporization.

          If you’re dumping energy into a satellite via laser impart enough delta-v to deorbit, then there’s absolutely going to be a build-up of heat. Heat of a magnitude the satellite most likely wasn’t designed to dispose of. You’ll have molten globs as you said. You’ll get pressure build-up. Eventually something is going to experience some runaway thermal expansion, followed by what might be described as rapid unplanned disassembly.

          If we get down to the barest bones of the problem, it takes some rather serious energy to de-orbit a satellite. It’s not like most laymen think of space, where you just give something a gentle push and it floats off in that direction in a straight line forever. We gotta sink all these perigees into the atmosphere where the satellites can burn up. Any attempt to do that is going to take a lot of energy and hardware spread across an immense swath of space and moving incredible speeds. And all this will need to happen tens of thousands of times. It will not happen without incurring significant increases in space junk. It’s a non-starter if there ever was one.

          1. Instead of ablation, can we use lower power lasers focused on the target over a longer period of time to move the objects out of orbit? I mean surely there has to be some effect from photons hitting a target. (Granted it’s minuscule, but given enough time it should work.)

        2. Ugh, clouds of dust and satellite pieces vaporised by the laser sound like they could create a 3D version of the omnipresent sticky coca-cola stains you have anywhere you try to sit down in a city that isn’t actively being cleaned.

      2. Deorbiting with a laser is based on the idea that a plasma plume will be created where the laser strikes the target. In space, this effectively works as a tiny rocket engine, and provides thrust along the same axis the laser was fired on.

        So if you were on the ISS, and fired a laser at an incoming piece of trash, it would provide it with retrograde (opposite the direction of travel) thrust. This will slow down the target, and due to the way orbital mechanics work, simultaneously lower its apoapsis (peak altitude).

        Long story short, a good blast with the laser should send the object headed down into the atmosphere where it will burn up. Not immediately of course, but it will get the process started.

    1. You can push objects from below. When you push them up, but not in direction they’re flying, they will have more unstable orbit. If you push them in special parts of their orbit, their orbit will at some point cross atmosphere.

  3. I’m surprised by the use of a harpoon. Does the risk of creating more untrackable micrometeorites with the impact of the harpoon out weight the risk of having a large defunct but trackable object in space?

    1. My immediate thought on that as well. The first idea is probably worth trying, but isn’t really that cool. I wish they had decided to try the concept of flying an exposed gel-matrix to “catch” the smaller, untrackable particles and essentially sweep up the orbital path.

      The third idea–testing their scheme of rendezvousing with tumbling, uncontrollable craft–that’s cool. I’m excited to see how it works out for them.

      1. If the net is tied to the garbage scow, wouldn’t the tumbling of the target wrap the tether line around itself (or twist it until it knots up)? That could lead to some unpleasant repercussions as the target winds itself into the scow. Smarter people than me are working on this though so I’m sure they’ve got that planned in.

  4. ISTR a NASA(?) discussion about coaxing a comet/meteor that is heading to impact Earth by flying a spacecraft “close” to it and have the interaction of the gravity move the meteor from its course. That way, Earth dwellers would not have to worry about a huge comet/meteor being blown into millions of comets/meteors heading toward Earth.
    Or similar to the laser ablation, detonating a small slow nuke on a side of the threat to push it off course.

  5. Why?

    This thing releases it’s own ‘imitation’ space junk in order to practice catching it. Ok.. I see a big problem with that idea. All they are doing is practicing grabbing on to things. In this “release and catch” scenario they cannot possibly be doing anything to address the top to challenges in cleaning up space junk.

    The first problem… space is big. Really big! Ok, I get it, we are only talking about Earth orbit here but that is still HUGE! Think about how big the Earth is. What did you picture? I bet you thought about traveling in a circular line around the Earth. Most likely you imagined flying or sailing around the equator. That’s a long distance isn’t it. But.. it’s NOTHING compared to the space that junk is spread out in.

    Things do not orbit at the surface. They are much higher up. Think back to high school geometry now. Circumference increases exponentially as the radius increases. Traveling around the planet at an orbital altitude is a much longer trip than doing so near the surface!

    But.. that still doesn’t do the problem justice. Space junk doesn’t only orbit around the equator. There are polar orbits too. So.. this is a problem of ‘cleaning’ an area that is a thick-walled hollow sphere much larger than the Earth! Sure, there is a lot of junk when you squeeze it all into the area of a little png that fits in a web article it looks like the Earth is drowning in it’s own waste. In reality though there are huge amounts of empty space between those individual pieces of space garbage. Any attempt to collect them is going to mean spending millions or billions of dollars to launch a new satellite that will use up all it’s fuel just to get 2 or 3 items. It’s financially untenable! Furthermore if even a small fraction of those satellites blow up it could easily add more junk than it removes!

    Second, the problem of velocity. The difference in velocity between items in different orbits make them dangerous projectiles. This is like trying to make peace by sending a softball team into a warzone to catch all the bullets in their gloves!

    No doubt the maximum distance and the maximum differences in velocity between this satellite and the ‘junk’ that it ejects will be very small because it is all originating from the same orbit. So…

    what’s the point?!?!

    1. You don’t need to clean the whole area – you’re not talking about sweeping up nuts and bolts. There are a few “major risk” contenders that you would target and deorbit.

      1. I have never heard that. I only see articles talking about how it is a problem because there are so many pieces of junk up there and even the smallest ones are dangerous.

        1. Yeah. Pop science. Gotta love it. Small objects are a problem, too, but not a big enough problem that you’d try to deorbit them. The big objects are a problem because if there’s a collision, you get *lots and lots* of little objects in similar, but slightly different orbits. Like, orders of magnitude larger than what’s up there now.

          From the RemoveDEBRIS mission page: “A main part of these roadmaps is e.Deorbit, a program spanning a host of phase studies examining removing a large ESA-owned object from space, namely Envisat.” Follow up on e.Deorbit and you’ll find they’re talking about Envisat all the time.

          This isn’t to say that Envisat’s the *only* dangerous derelict up there – it’s just the most dangerous (and biggest) one that the ESA owns, which is why they’re targeting it. Once they’ve demonstrated that they can do it (and that’s a ways off) then that can be used as the basis for a commercial enterprise to remove debris from orbit.

          Why would anyone pay to remove a satellite from orbit? Because it’s a financial liability risk. That’s why most LEO satellites will actively decommission themselves, but there’s always the possibility of an operational failure, like Envisat.

          It’s really those satellites (the LEO ones that die before you can deorbit them) that are the big problem, because they have the potential to become a nearly impossible-to-track debris cloud.

    2. No, circumference does NOT increase exponentially with radius. There is a perfectly linear relation between circumference and radius: U=2*pi*r
      But this does not change much with the problems of cleaning up.

  6. So I actually had the pleasure on working one part of this mission. I helped develop the flight software running on one of the smaller satellites it deploys. The same code (with variations of course) has also been used on two prior missions to great success.

    A great team who I very much enjoyed working with and wish them all the success with this mission.

  7. Every time I see comments on how to clean up space debris, I think that this is an amazing endeavor and should definitely be attempted in whatever way possible…
    I just cant help but feel that chasing debris with more potential debris might not be the best option. Matching orbits, catching large satellites, these are all things that are rather “expensive” to do in orbit, both for the costs of fuel and labor to pick a target, change course, potentially catch, couple with… somehow, and then bring down from orbit.

    It just all seems very rube goldberg when every launch will bring up more than what the current ideas sound like they could bring down.

      1. Have panels of it that roll out from LEO satellites when they’re decommissioned. They’ll increase the drag to drop them faster, and on the way down they’ll pick up lots of micro debris.

        The sticky stuff would have to withstand years of exposure to vacuum and temperature swings, and not have bits of it fly off from impacts. Most likely some type of zero VOC silicone, formulated to be extra gooey.

      2. That would work if all the orbits were similar. Unfortunately 17km/s approach velocity means your paper needs to be an unknown better-than-Kevlar material and your glue needs to make sure no fragments leave. And not boil in space. Nice in theory but not viable.

        I would say, however, that flypaper slow harpoon is an infinitely better idea than firing a grappling hook into something and expecting no debris to break off.

    1. “It just all seems very rube goldberg when every launch will bring up more than what the current ideas sound like they could bring down.”

      It’s almost like they should test the mechanisms that they’re planning on using as much as possible to make sure they understand the risks and how to mitigate them. Something like that could possibly be done with a small test platform, right? Maybe at the ISS?


  8. I’ve seen a lot of other stories about this that lead with SpaceX launching it and make uninformed folks think this is a SpaceX experiment. Kudos to Hackaday for doing this story right.

    1. I think that confusion results from some people using the “,” as a thousands-separator (1,000 = 1000) and not a decimal separator (like 1/10=0,1). So they mean 175000mph or 28000km/h, which are correct values.

  9. So many comments and no one realizes this is actually for the military to bring down other country’s satellites? Capture a Chinese sat and reenter it over the US with a heat shield and parachute. Sure you could just blow them up, but that would create a whole lot more debris in orbit. And if we could capture it, then we can analyze what the capabilities are. It doesn’t make sense as a space junk cleaner because it isn’t.

    1. The Chinese already blow up their own satellites, that’s what got the situation as bad as it is.

      Nice as the conspiracy theory is, you’ve been watching too much You Only Live Twice. Given every major nation has tracking stations, it would not be subtle: “Oh, look! Our satellite changed trajectory just after a craft that was a secret payload rendezvoused with it. I wonder what happened there?”

      The problem is we are likely reaching the critical point for Kepler syndrome in the next few decades. Fixing it now is possible, fixing it after the chain reaction will not be. Removing a few large breakable lumps of mass makes an enormous difference to the chain reaction probabilities.

  10. Does anyone else feel harpooning into an unknown material in an environment where releasing 1 gram fragments is extremely unpopular/dangerous is a bad idea. And it has been launched from the ISS orbit too so it could pose a direct hazard if something breaks off even at a relatively small speed

  11. LOL when I first read the title, the first thing that came to my mind was sending household trash to space, now that would be an interesting idea, afterall look at the landfill sites getting full. Send it out into space would burn it up in seconds! But then again who wants to pollute the outer space with trash?

  12. I am more concerned that the ISS back-up power appears to be four 6-volt automotive batteries (located directly outside the Japanese Experiment Module, where the hatch opens). I can see the three cells on each battery, and a handy handle. This is appalling.

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