A Crash Course in Space Junk

OCD or excessive compulsive disorder affects about one person in 50. Patients with the condition often feel compelled by anxiety to perform repetitive, ritualistic behaviours, like washing their hands a certain number of times or getting dressed in a certain way. If they don’t comply, they experience an overwhelming sense of dread that something terrible will happen. One way to treat the problem is to prevent sufferers from fulfilling their rituals - for instance, making them touch a toilet seat and then stopping them from washing their hands more than once. But this only works for about half of patients, so what’s needed is a deeper understanding of what causes OCD in the first place so that better therapies can be developed. Now Annemieke Apergis-Schoute, at Cambridge University, has discovered that OCD patients are very good at learning when things are unsafe or a threat, but they fail to be flexible and learn when something is actually safe, as she explained to Chris Smith...

Annemieke - We used an experiment where you had one threatening stimulus. That meant it was a stimulus that was sometimes paired with a mild electric shock, and another stimulus that was always safe, so it was never paired with a shock. The nice thing about this experiment is that we can measure very small changes in sweat in the skin so we know exactly when the participant is expecting a shock and when they are not, because you see a difference in the amount of sweat that comes on. And then unannounced in the middle of this experiment, the threatening stimulus became the safe one, and the safe one became the threatening one.

Chris - Right. So let’s say, for the sake of argument, I show them a picture of an orange and I give them an electric shock whenever they see it. I show them a picture of an apple and I never give them an electric shock. So you’re measuring how much they sweat when I’m presenting this sequence of pictures at them randomly and then, all of a sudden, you flip round so the orange, which was I’m going to get a shock now becomes no shock, and the apple, which was safe now gets an electric shock?

Annemieke - Exactly.

Chris - If a person who is not affected by OCD does this, what do you see in a normal person first?

Annemieke - What we see there is that they’re very flexible. They have increased amounts of sweat, which we call skin conductance, to the threatening stimulus compared to the safe stimulus. And then when this reverses, so when the threatening one becomes safe and the safe one becomes threatening, they very easily adapt to this. So that in a few trials, the one that has now become threatening, which was previously safe, leads to more sweat than the newly safe one.

Chris - Right, and what happens when you do the same thing with someone who has got OCD?

Annemieke - What we found in this study is that although they initially learn that one of the stimuli is threatening, when this changes they can’t learn that stimulus that was previously threatening is now safe.

Chris - If one looks at the brain when it is in the process of doing this reversal, when you take something that was a threat that had something unpleasant attached to it and you flip it round and make it un-nasty, how does it compare when you look at someone who’s normal and someone who’s got OCD?

Annemieke - Because we performed this experiment while the participants were in the brain scanner, an area called the ventral medial prefrontal cortex that we know is specifically involved with learning safety of stimuli, and we already know that this area gives a larger signal to when a stimulus is safe. What we found was that this signal was entirely absent in OCD patients from the get go, meaning they did the initial learning based on just learning about the threatening stimulus in absence of learning most likely about the safe stimulus.

Chris - Is it that there’s physically some kind of circuitry missing that enables them ascrib safety to things, or is it that they’re just very good at rendering things unsafe?

Annemieke - I have my own theory about this. I believe that this area of the brain might be too concerned with their kind of self-referential kind of thinking about their own obsessions and, perhaps, unavailable to pay attention when things are rewarding or safe in the environment.

Chris - Does this help that 40 percent or so of people for whom the exposure therapy does not work at the moment? Have we got some clues on the basis of what you’ve found as ways we can intervene more meaningfully for those people?

Annemieke - So, yeah. We think that we can come up now with new therapies. For example, in terms of the exposure with response prevention therapy, we could augment a therapy by enhancing the experience of the safety. So when they actually touch the toilet seat that they feel more of a reward, that they feel oh yes indeed, nothing went terribly wrong when I didn’t wash my hands right afterwards. So this experience can be more meaningful and, perhaps, is easier for them afterwards to overcome the urge of performing the compulsion.

Ebola made the headlines in 2014 when there was major outbreak in West Africa. Thankfully, for the time being at least, the threat to humans was halted, but it’s still a massive problem for gorillas. Experts estimate that, over the last 30 years, a THIRD of gorillas have been wiped out by the virus. So how do you protect a wild animal from a disease? The same way you do with people: a vaccine! The results from a trial in chimpanzees for a new oral vaccine were published this week in Scientific reports, suggesting the vaccine would be effective, with no damaging side effects. But new legislation in America could prevent further trials of this kind, which could be devastating for future outbreaks of diseases in our endangered cousins. Georgia Mills spoke to Peter Walsh from the University of Cambridge, and Apes Incorporated, about the challenges of vaccinating a 450 pound wild gorilla!

Peter - With wild animals it’s more difficult to protect them. Some of the gorillas and chimpanzees are in tourism programmes or research programmes where they’re habituated to the presence of people. With those animals you can get up close, you can get a dart gun or a blow dart. We use a phtt and you can shoot them with a little dart that has the vaccine.

The other animals are very afraid of people and so it’s too difficult to try and track each one and shoot them with a dart. So what we’re working on is an oral vaccine where you put the vaccine in a little bait. We’re using a fruity bait that’s sweet and we’re testing that now Africa. You put the vaccine in there and then you can put that at areas where there’s high activity rates by gorillas and chimpanzees, and then they’ll eat the bait and then become immunised that way. We have a problem right now, we have gambian rats (pouch rats) and the rats come in at night and they eat all my bait and so I’m working on ways to get around that. But, in principle, we should have the ability to really precisely target who gets vaccinated.

Georgia - OK. I suppose you’ve got to test that this form works?

Peter - Exactly. So we need to go out and, preferably, in the species that we’re trying to vaccinate in the wild, we need to test in the captive animal or closely related species. So chimpanzees, gorillas, and humans also, are very closely related. The objective of testing this in a chimp is to see will it have a robust immune response and will it cause any kind of health complications, and so the trial we’ve just done did exactly that. We took ten chimpanzees: four of them we injected intramuscularly and six we gave an oral dose of the vaccine. Then we took blood samples every week for a month and what we found was, first of all, it didn’t cause any health complications, they didn’t get sick. And they didn’t show any kind of behavioural anomalies, they weren’t really stressed out.

And the other thing it showed is they had an immune response that was very similar to the immune response of monkeys who were vaccinated, and then challenged with ebola and survived. So we didn’t actually challenge the chimps with ebola, we just look at their immune response and health response, but their immune response was very similar to the responses of these monkeys that were actually challenged and survived challenge.

Georgia - Is it quite hard to test these things? I mean, there aren’t too many gorillas and chimps around - is it hard to get that testing process through?

Peter - Yes. It’s exceptionally hard because the United States is the last developed country that allowed biomedical testing on chimps and, as of last summer, they’ve now banned it. The rationale was that it was inhumane and that it was unproductive scientifically. I don’t want to get into a debate about whether or not it was productive for human health, that’s somebody else’s business. But what I can tell you absolutely is a) that it’s not unproductive for conservation reasons, and b) we actually did monitor the stress responses of the chimpanzees during the trial, and they don’t show the extreme health effects that the animal welfare advocates were claiming.  So now they’ve shut down these facilities and we really have no place where we can do the trial.

Now what critics say was: you can do this in a sanctuary, you could do this in a zoo. While the sanctuaries are all philosophically opposed to animal testing so they won’t do it, but zoos have facilities to do it safely. That’s the other issue as well - where can you do this safely? But they are terrified of a public backlash. So here we are, we have really no place where we can do these trials and consequently that’s a problem because in Africa, they say if you haven’t tested that vaccine in a captive ape, or any human, you're not going to use it on our endangered apes in the wild. So it’s a catch 22.

Georgia - Right. So in future when the next ebola comes it’s going to be more difficult to do what you’ve done here?

Peter - Exactly. This has happened before. Ebola goes away for a while and people say oh, it’s gone, it’s not a problem anymore, and then ‘boom’ it comes back and it kills a bunch of people. And all of a sudden it’s in the news and it’s like “Oh, we’re going to worry about it again,”. For once, for once, why don’t we think into the future and not react on a crisis basis but actually plan ahead and say you know a) we’re going to need to vaccinate for ebola again in the future, and b) there’s always other diseases. These animals are critically endangered. They’re in really bad shape and it’s incredibly frustrating because we have the ability to protect these animals but we’re not doing it for silly, foolish reasons.

Why is space junk a threat to us? And how come there’s so much of it up there? Kat Arney talks to extraterrestrial rubbish expert Dr Hugh Lewis from the University of Southampton. 

Hugh - We’ve been launching satellites into orbit since the late 1950s, so we’ve basically accumulated a lot of junk associated with all those space launches. They can be satellites that have reached the end of their mission. It could be the parts of the rocket that we’ve used to put the satellites there. It could be bits and pieces from those satellites that have somehow come away. But the most numerous objects up there are fragments from explosions and collisions.

Kat - It’s big bits and it’s small bits. But why is it so much of a problem? Doesn't it all eventually just fall back down to Earth?

Hugh - Well actually, many of the objects that are up there will be up there for centuries or even longer and that’s simply because the only mechanism we’ve got for removing the objects from the orbit is the atmosphere at the moment, and the atmosphere is so sparse at those altitudes.

Kat - So thinks aren’t just breaking down and burning up?

Hugh - No, absolutely. So yes, if an object is experiencing enough atmospheric drag it will come down and burn up. But objects that are high enough don't experience that kind of drag and they can be there for… some of the objects - Cath mentioned Envisat in her piece there - and that’s potentially up there for more than a hundred years.

Kat - Now isn’t space massive? We shouldn’t forget that space is enormous so how come this junk poses a problem for other things we want to send up into space?

Hugh - Well I think that the space is big mantra was used and has been used since the beginning of the space age and it’s certainly true. The volume space occupies is enormous. But what we’re doing is sending satellites into quite specific orbits and into orbits that are relatively close to the Earth. And if we keep doing that, as we’ve been doing for the last 50/60 years, then all that junk accumulates relatively close to the Earth in these quite congested orbits.

Kat - The way I like to think about is it’s like a trail of muck going from your front door where you always walk across the same bit of the carpet.

Hugh - Yes, absolutely right. Yes, that’s a very good analogy.

Kat - We saw in the film Gravity, there’s a collision with some space junk and it sets off a massive chain reaction. Is that the worse case scenario that there could be a rocket going up, or a really important communications satellite or something and it gets knocked out?

Hugh - Yes. So, fundamentally, the problem with space debris will be those collisions that could occur. You could lose a satellite from an impact with something in orbit. But that collision cascade that you talk about is, I guess you could say, that’s the absolute worst case that you could expect. That’s something that we’re working very hard to try and avoid.

Kat - There was in the news recently that the Chinese have, apparently, lost control of an abandoned space station that was up there so, presumably, this is now classed as space junk? That’s quite a big thing and what’s going to happen to it up there?

Hugh - That particular space station, I guess, it’s not as big as the International Space Station. It’s slowly moving down in terms of altitude and will ultimately, we hope, burn up in the atmosphere.

Kat - But what if it doesn’t, is it going to come down? And do these bits of junk actually come down and hit the Earth?

Hugh - It is possible for parts of spacecraft to survive that re-entry process; the heating and the loading that they experience, so some components may survive down to the surface of the Earth. But most of the Earth (three quarters of the Earth) is covered by water so it’s quite likely that we’d never even see these objects as they come in.

Kat - We also heard in Cath’s piece that there’s a whole load of debris from the Chinese trying to blow up something to try and get rid of it, and that’s just made the problem worse. Is it the big bits of debris or the small bits that are the most concerning?

Hugh - I think, in terms of the long term evolution of the space environment, we worry about the big objects because, essentially, all that mass that is locked into that object can be converted into many, many fragments. But in terms of objects that can be lethal, you’re talking about objects that are probably the order of millimetres in size that can actually pose serious risk to operational spacecraft.

Kat - That seems pretty dramatic when you think oh, it’s just going to be something massive and, in fact, it could be almost a fragment of dust something the size of a piece of sand that could bring down your spaceship?

Hugh - Yes, indeed. The space shuttle, when that was flying, they would have to replace the windows on the space shuttle, for example, due to the impacts that they would receive from objects that were very, very small. The craters that were left behind there are just perfect evidence of the risk that space debris poses.

Space junk is currently a problem and could be an even bigger problem in the future, so the big question is - can we clean up space? There are a few projects worldwide looking into this and one is at Surrey Space Centre, where removeDEBRIS is going to test several technologies for bringing this junk back down to Earth. Aaron Knoll is a researcher at Surrey Space Centre, and Georgia Mills asked him why it’s so tricky to fix this messy problem.

Aaron - It’s a challenge because pieces of space debris are one in space so they’re quite a way away from the surface of the Earth, but the other reason is that they’re moving incredibly fast. So they’re moving on the order of about 7 kilometres every second so actually rendezvousing with a piece of space debri, in and of itself, is an extraordinary challenge, let alone trying to get rid of it.

Georgia - What is Surrey Space Centre trying to do about this?

Aaron - We have a project called “remove debris”, which is aiming to demonstrate technologies for rendezvousing with an uncooperative object (that's a piece of space junk) and then testing various technologies to actually tether or secure ourselves to the object and then, finally, to tow the object out of orbit.

Georgia - So what kinds of things is it going to try and do?

Aaron - It has a couple of different technologies it’s testing in orbit. The first is a harpoon, which sounds rather primitive in technology and, indeed, you can say it is. But what it is is it’s a sharp metal object that penetrates the surface of, let's say, an old dysfunctional satellite and then with barbs it actually hooks onto the surface of that satellite. You have a tether connecting the harpoon to the main mother ship, and then that mother ship can pull it out of orbit.

Georgia - I assume that’s for the larger pieces, what about the smaller ones?

Aaron - We’re also testing something called “net capture”. So we deploy a large net which ensnares smaller objects and, as well as with the harpoon, once you’ve ensnared those objects you would use a tether to drag them out of orbit.

Georgia - I like the way it’s a harpoon and a fishing net that you’ve got here. Cleaning up space junk is basically fishing?

Aaron - Yes. I’ll say the actual technologies were selected based on their reliability. You don’t want to have pieces of technology which are complicated just purely for the sake of being complicated. You want to actually balance what you’re trying to do against the most convenient way of doing it, and it turns out that the net and the harpoon were actually coming up on top in terms of their simplicity and their reliability.

Georgia - Once you harpoon or you net a piece of space junk, how do you get it back to Earth?

Aaron - Once we’ve secured them, we’re testing a de-orbiting sail. This is a 5 x 5 metre sail and it puts a large drag surface area onto the spacecraft so that even the small amount of atmosphere, which is in orbit, will slowly pull the spacecraft on a descending trajectory, and it will burn up in a ball of fire in the Earth’s atmosphere.

Georgia - So where are we with this plan - what’s next?

Aaron - We’ve come a long way on actually developing the technology, so the next phase is to launch it into orbit. I believe that we’ll be launching in the next year or two and then we’ll be able to see whether these technologies actually work.

Georgia - Oh wow! Is the plan in the long run for this technology, is the mother ship going to go along grabbing loads of different bits of space debris? Or is that not possible and will it just have to get one and fall back to Earth because that seems an incredibly expensive way of cleaning up space?

Aaron - So, the long term objectives I think what you’ll see is a mother ship that’s able to rendezvous with multiple objects and then attach to themselves a rocket motor to drag them out of orbit. But then again, it could rendezvous with another object, so then you could have one mission cleaning up multiple pieces of space debris.

Georgia - These are the projects the Space Centre’s working on. Are there any other zany ideas or wacky plans people have come up with to try and sort this problem out?

Aaron - Yes. I’ve heard of a number of different projects. The one that I find particularly interesting is called the “ion beam shepherd.” As opposed to actually securing to the object with a tether and then trying to drag it out of space, this one aims to use an ion beam from a spacecraft at some distance away from the object and push it gently out of orbit. I think that’s quite exciting because eliminating the complexity of actually trying to secure yourself to a tumbling object in space makes the mission much more practical. Also, you could imagine that if you’re pushing an object out of orbit using an ion beam, then you could rendezvous with far more objects because you don’t have to attach to each of them a sail or a rocket motor. So that one struck me as rather clever.

Georgia - Oh wow! So the idea that a spacecraft would aim and fire like pew pew, and all these different bits of space debris would fly out of orbit. So they’d still be in space but they wouldn’t be our problem any more?

Aaron - Yes. So you could push them higher up into higher orbits (what we call graveyard orbits), or you could push them down into the Earth’s atmosphere. Either way you’re clearing the useful areas of space (the lower orbit area), for future space missions.

Georgia - Wow! Very cool ideas. Here’s my idea - why can’t we just use magnets to sweep it all up?

Aaron - Ah yes. This is an interesting one. It’s because magnets actually will have very little effect on a spacecraft. Spacecraft are designed to be what we call “magnetically clean objects.” That means we specially choose the materials so that they have absolutely no ferromagnetic properties. The reason we do that is because if spacecraft were magnetic they would interact with the Earth’s own magnetic field - what we call a compass mode instability. So by making spacecraft very magnetically clean, they can fulfill their mission, Unfortunately, it means that we can’t secure to them with magnets.

Georgia - Ah, so not a great plan then?

Aaron - Maybe not the best.