Space debris is becoming more of an issue as time goes on with the number of objects doubling in the last 15 years. Part of that problem is inevitable as the stage based approach to rocketry, whilst being the most efficient way to transport mass to orbit, unfortunately leaves behind a considerable amount of mass. This, combined with the numerous defunct satellites and other bits of junk, means that our lower orbits are littered with objects hurtling through space with enough force to cause some rather significant damage to anything else we put up there. Solving this problem isn’t easy as just picking it up is far more complicated than it sounds. Thus researchers have long thought of ideas to tackle this issue and scientists working at the RIKEN institute may have come up with a workable solution for some of the most dangerous and hardest to remove debris out there.
The idea comes off the back of the Japanese Experiment Module – Extreme Universe Space Observatory (JEM-EUSO) telescope which is slated to be launched and installed on the International Space Station sometime in 2017. The telescope is designed to use the Earth’s atmosphere as a giant detector for energetic particles which will leave a trail of light behind them as they decay in the Earth’s atmosphere. The design of the telescope, which consists of three large lenses that direct the light to some 137 photodetector modules, means it has an extremely wide field of view. Whilst this is by design for its primary mission it also lends itself well to detecting space debris over a large area, something which is advantageous to the ISS which needs to do everything it can to avoid them.
However that’s only half the solution; the other half is a freaking laser.
Scientists at the RIKEN institute have posited that using something like the CAN laser, which is a fibre based laser that was originally designed for use in particle accelerators, could then be used to zap space junk and send it back down to Earth. This kind of approach only works for debris that are centimeters in size however they’re among some of the most devastating pieces of junk due to the difficulty in detecting them. With the JEM-EUSO however these bits of debris could be readily identified and, if they’re within the reach of the laser, heated up so their orbit begins to decay.
The current plan is to develop a proof of concept device that uses a 1/10th scale version of the current JEM-EUSO telescope combined with a 100 fiber laser. Whilst they haven’t provided any specifications beyond that going off their full scale design (10,000 fibers) the concept should be able to deorbit debris up to a kilometer away. The full scale version on the other hand would be able to zap space junk at a range of up to 100km, an incredible feat that would dramatically help in cleaning up Earth’s orbit. The final stage would be to develop a standalone satellite that could be put into a 800km polar orbit, one of the most cluttered orbits above Earth.
Our approach to tackling space debris is fast becoming a multi-faceted approach, one that will require many different methods to tackle the various types of junk that we have circling our Earth. Things like this are the kind of approach we’ll need going forward as one launch will be able to eliminate several times its own mass in debris before its useful life is over. It’s far from an unsolvable problem however whatever solutions we develop will need to be put to use soon lest our low orbits become a place that no man can ever venture through again.
Ever since getting things into orbit became a routine task the amount of stuff we’ve left floating around us in space has increased exponentially. Typically the debris that surround us are made up of the upper stages of rockets, disused satellites that can’t/won’t de-orbit for some time and, worst of all, innumerable other bits of miscellanea that are the result of things crashing into each other. This is the beginnings of a terrible self inflicted disease called Kessler Syndrome whereby the lower orbits are so littered with junk that launching anything becomes nigh on impossible, save for some drastic changes in technology. Thus it’s in our best interests to come up with some workable solutions to this issue and the engineers at the Japanese Aerospace Exploration Agency (JAXA) have come up with a very interesting solution.
Whilst most of the debris surrounding Earth will eventually make its way back down the time frame in which it will do so varies from years to centuries. Since the orbits are unstable it’s likely that they’ll change drastically over time and this means that the chance that they will collide with another bit of debris increases quite dramatically. This is the real crux of the issue as collisions of this nature create much more debris than their individual parts alone (it is also why all the collective space faring nations were a rather pissed at China for testing their anti-satellite missile). Whilst there’s not much we can do for the numerous small bits of debris orbiting Earth there’s a lot we can do for a specific type of space junk, specifically the upper stages of rockets, and this is what JAXA’s latest development targets.
The team at JAXA’s Innovative Technology Research Center have devised what they’re calling an electrodynamic tether to help combat the space debris issue. It consists of a small space craft, one could imagine something of cubesat size, that attaches to a large piece of debris via a long electrically conductive tether. Then, by virtue of the fact that Earth has a magnetic field and the tether is conductive, Lorentz forces then act to drag the two satellites back down to Earth. It’s a rather ingenious way of getting the junk to deorbit as it doesn’t rely on carrying massive amounts of propellant, making the craft infinitely smaller and far more efficient. It might only tackle a specific subset of the debris in space but their calculations show that this should be enough to prevent a runaway Kessler syndrome situation.
Probably the coolest thing about it, at least for me, was the preferred way of attaching the tether to the target. They have explored some regular options, namely coasting up to the craft and attaching it with a robotic arm, but since their targets are going to be the usually thin walled upper stages of craft they’re instead opting for a harpoon that will penetrate the hull of the craft. So in the future we could have a swarm of harpoon carrying cubesats orbiting us, ensuring that any large bit of space junk is brought to the fiery demise it so rightly deserves.
Of course this doesn’t mean the problem is completely solved but this could be enough of a stop gap solution whilst we figure out better ways of cleaning up our lower orbits. It’s not going to be an easy problem to solve, the energies required to get everything up there in the first place ensure that, but things like this show that there are highly efficient ways of dealing with it. All that’s required is for us to find them and, hopefully, deploy them before its too late.
In the short time that we’ve been launching stuff into orbit around our little blue marble we’ve made quite a mess of things up there. Sure it’s not that much of problem currently thanks to NASA tracking the most dangerous parts of it but the fact is that as time goes on the problem isn’t going to get better on its own. Whilst most space junk that’s close to earth or beyond geosynchronous will eventually burn up or leave our orbit for good the space in between there is littered with junk that will stay around from a couple decades to even a few centuries. It’s not exactly an easy problem to solve either as orbital mechanics aren’t exactly energy efficient, but that hasn’t stopped people from trying.
There are two factors that make cleaning up space junk difficult: the orbital speeds involved and the fact that most space junk doesn’t share an orbit. The first one is the reason that space junk is such a big problem in the first place. You see to stay in orbit you need to be travelling at some 26,000KM/h (Mach 26ish) and when you hit that speed small things start to become rather dangerous. The ESA has some good pictures of what hypervelocity impacts look like and should such an impact happen on a craft it’s usually the end of it, and the beginning of yet another debris field.
The orbits also pose a problem as any efficient space junk collector will need to change orbits often in order to be able to capture as much space junk as possible. Doing so requires either a lot of energy or an incredibly efficient engine (thus, lots of time) and there’s really nothing that solves either of these problems well when it comes to a space junk collector. The Swiss Space Centre still wants to have a crack at it though with their concept craft CleanSpace One:
The cleanup satellite has three major challenges to overcome, each of which will necessitate the development of new technology that could, in turn, be used down the road in other applications.
After its launch, the cleanup satellite will have to adjust its trajectory in order to match its target’s orbital plane. To do this, it could use a new kind of ultra-compact motor designed for space applications that is being developed in EPFL laboratories. When it gets within range of its target, which will be traveling at 28,000 km/h at an altitude of 630-750 km, CleanSpace One will grab and stabilize it – a mission that’s extremely dicey at these high speeds, particularly if the satellite is rotating. To accomplish the task, scientists are planning to develop a gripping mechanism inspired from a plant or animal example. Finally, once it’s coupled with the satellite, CleanSpace One will “de-orbit” the unwanted satellite by heading back into the Earth’s atmosphere, where the two satellites will burn upon re-entry.
In essence CleanSpace One is a simple capture and de-orbit craft, designed to be disposable. They’re looking to create a whole family of them that can cater to any kind of satellite and presumably looking to launch several at once in order to keep the cost down. Whilst such a craft would eliminate some space junk it doesn’t address the larger problem of those satellites not being managed properly in the first place, which I think is the core of the problem.
You see most of the junk satellites are still there because they weren’t designed with any kind of de-orbiting mechanism in them. The reasoning behind this is simple, such systems add cost to already expensive satellites and are therefore usually overlooked. There’s also a lot more maintenance and regulation required for such things as well like Hydrazine which is commonly used in such systems. It’d be far more cost effective to regulate that all new satellites have to have something like NanoSail-D attached to it as they’re relatively cheap and can de-orbit a satellite without the added hassles of current de-orbit systems.
I still commend the Swiss for being forward thinking with this issue however and realistically this is logical first step towards fixing the space debris problem. With experience they might be able to find clever ways to structure orbits for debris capture or devise better propulsion systems that will make more efficient collection possible. Developments in this area will also have flow on effects for other space programs as well as many of the technologies developed for something this will have dual uses elsewhere. Hopefully this will trigger other countries to start thinking about their own kind of space debris management system and eventually lead to an end to the mess that we created up there.