 As Laura's mentioned, I'm a spacecraft engineer, very fun title, so as a thermal engineer my job is to measure and control how the heat moves around on a spacecraft. So space is surprisingly enough, one of those challenging environments, we don't have the protection of atmosphere so at an earth distance spacecraft in full sunlight will get to around 180 degrees within half an hour. Equally, the side that is facing away from the sun, so facing us into dark space, is going to reach somewhere around minus 180, minus 200 degrees C again within half an hour. So we're playing with some pretty extreme temperatures, you start putting some different orbital control in there, you're changing what side the sunlight's hitting and everything can start getting a little bit exciting. So what we try and do for thermal control, in fact for pretty much anything on a spacecraft, if we can avoid anything that switches, we will do. Anything that requires any mechanical input, it's a potential risk for failure. As soon as you're switching something regularly, it's not going to last very long. Telecommunications spacecraft can be active for around 25 years after launch. Can you think of anything that you own that you have used for 25 years with moving parts and you haven't actually touched it at all and it's done its own thing completely? So that's kind of an idea of what the challenge is. So that luckily maybe for thermal engineering, we can actually get away with not having too many active methods of control. We try and aim for a lot of passive control methods. So one of those is to use some thermal blankets. So this is why I always consider that my job is one of the girliest of jobs because we take something that's incredibly expensive, millions to billions of pounds and we make them shiny. So this is a thermal blanket. If any of you here ever watched or run a marathon or some kind of race, couple of nods, brilliant. So at the end of the race, they get given like a sheet of foil. It's essentially what this is. There's lots and lots of different layers. I'm going to pass this round. Well, some seamless stuff round. It's made up of lots and lots of different layers. And what the layers are doing is the heat, yeah I'm going to do it that way round. Heat gets to one surface and it's going to be reflected away because it's shiny. It's not at, nothing is a perfect reflector. So we're going to actually absorb some of the heat. So that particular layer of foil will get hot and then the same thing will happen between one layer and the next and the next and the next. So what we're doing is reducing how much heat is getting through one layer to the next until you get to the other side of the blanket. So whether that's some side or internal side. So that's how we can control how much heat is coming into the spacecraft and leaving the spacecraft through blankets. As an idea of how effective that is, this 10 layers of blanket, so if it's on full sun, 180 degrees on that full sun side, it's going to be at around 50 degrees on the inside of that blanket. So pretty effective. And that's what my little demo is going to be for. Do I have a willing volunteer or do I need to pick somebody out of a crowd? Yeah, please do. Excellent. So we're going to do a proper little school style experiment. So what's your name? Harriet. Harriet, hello, hello. Can I have a little round of applause for Harriet for being a volunteer? Thank you very much. So what I've got in the corner here is a little IR lamp. So it's nothing particularly fancy. It's the same as what you might get in a little reptile cage. So it's going to make things warm. And we have a plate, nice and round. And we have some chocolate. What happens if you put chocolate under something hot? It melts. Fantastic. So that is pretty much what the experiment is going to be. Harriet, can I ask you to arrange these fairly evenly on the plate? All of them. As much as you like. It doesn't need to be all of them. Just a decent selection. Here we are. Yeah, and then if we can spread them around a bit. A bit of fair testing, so you know I'm not rigging it basically. So what we're going to do is we're going to cover half the plate with the blanket and then leave it to kind of essentially cook under this thermal lamp. Here we go. So if you can put that fairly easy distance under there, that would be great. Lovely. And then we'll come back to that pretty much just before lunch and see how squishy they are. That's it. I'll get you to do some testing in a little bit. So we've got our fair test set up. So hopefully that's got just enough time for everything to get a bit gooey. So I didn't mention I'm going to pass some of these around. Here we go. Pass these. Here you go. Have a little squid. Have a rub. You can feel the different foils in there. So that's a little bit about blankets. Some of the other methods that we'll use on there, if we actually want to let heat out the spacecraft, which we do want to do over and over again, we use different surface coatings. That will often be black paint, white paint, or it might be tiny mirrors. Anybody here like tiling? Yeah. So this is the only size that spacecraft mirrors come in. And I'm going to use my reference point of telecommunications satellite again. Telecommunications satellite have two walls. So there are a box. They've got four walls. Two whole walls. And they're around six metres by two metres completely tiled in these. It's certainly not a job that I would want to have. Thankfully, as an engineer, my job is to decide where the tiles are going not to actually put them on. So that's a little bit of some of the different techniques that we might use, and I'll have a bit of chat with those things later. But now I'm going to actually use my slides I've prepared. Does anybody know what this is? It is a solar panel. It's one of my favourite images. It's not the probe. It's the satellite that took the probe to the comet. So yeah, this is the solar array of Rosetta. So that is the comet 67P. I can't remember its full name. It's mega long. So that is the comet that, as it's on its approach to the comet. And Rosetta is a UK mission. So it was retired last year. It woke up so that was around September time last year. In April last year, the comet had actually came out of our hibernation after nine years. Pretty much as many of those functions switched off as possible. So it's been doing all its orbital control completely passively on the very bare minimum of anything it can do. It's been a very long way. It's been out behind Jupiter. It's been above five distances between the earth and the sun. So five AU. And it's really unusual that at that distance that we will be using solar arrays. So it's ended up having some of the longest solar arrays that many, many spacecraft will have. Each of those solar arrays is in the region of 24 metres and it's got a pair, it's got two of them. So it folds up pretty small. And actually this image, the reason it's one of my favourite images is because this is essentially Rosetta's own selfie. It's trying to take an image of the comet and it's solar arrays in the way. It's trying to take images where, as it's on a flyby past Mars. And that image will have taken 14 minutes to actually be being back to earth because it comes through its tiny little pixels. So, and again, that's mainly the reason that it's in black and white. So yeah, Rosetta is a UK mission. When we first started doing Rosetta, there were four of the missions that were essentially on the books. Each department had one computer per department. It's got four or five spacecraft. Nearly everything was designed numerically by hand. And the computer models, you would book your time on the computer and you would get 24 hours to be able to run anything. So Rosetta's thermal model was around 150 nodes. As a comparison, Solar Orbiter, which is one of the more recent models that I've worked on, that model now is at around 15,000 nodes and takes about two hours to run. So computing power has significantly changed in the last 20 years, but we work with what we've got because once it's up there, we're not going to be playing with it. Rosetta, interestingly, we knew that technology was moving at a huge rate when it was launched. So we didn't actually design for anything after it came out of hibernation. So its instructions were, do all of it whatever it's doing to get where it's needing to be, wake up, send us a signal to say that you're there. And then we started doing lots of communications with the spacecraft. Does this work? Does this work? Does this work? What's the health of that part and this part? And then we send a whole load of new software to update the next section. And then it arrived at its comet and the comet wasn't shaped like a spud. It's more like a rubber duck. Which was a surprise for everybody concerned and that's where some of the interesting sections with Feely, which is that problem when it landed on there, in terms of actually how to land it on the actual spacecraft. It's been incredibly successful mission. They've learned a lot of things about comets. And there are further missions in the pipeline that have been discussed with NASA and ESUS, the European Space Agency, in terms of other different spacecraft. Right. So this is the insides of my very first thing in space, which is a bit of a weird phrase to ever be able to say. If you open up any spacecraft, the insides bit pretty much are shiny. Of the silvery variety, or black. Any idea why we might use black on the insides of spacecraft? Black body radiation. This man's got it there. So black is a pretty good absorber and emitter in a particular wavelength that we're interested in. Which for me, you, the planet, most of our spacecraft, that's infrared. So it's going to emit and absorb pretty much equally. Which means that you can put something hot in that spacecraft and it's going to be able to get short of plenty of its heat. And then, at the other end of it, something that's a bit cold can also start and absorb some of that heat. What we're trying to do is to level out any of the temperature gradients that you actually have across a spacecraft. Have any of you come across the idea of thermal acid distortion? I know, there are great phrases aren't there? You probably have, but maybe not with those actual words. So if I have a lump of metal say about this big and I heat it up, what's it going to do? It's going to expand and how about if I cool it down it's going to contract. There you go, thermal acid distortion. How difficult is that? Well that's totally fine when you've got a nice lump of metal and it's all heating evenly. Imagine you've now got like a bar of metal and you heat one end back to the other. So everything's starting to get into a bit of a different shape and then you make that into a lovely structure and you've got heat on one side but not on the others. And that's where we start getting some pretty interesting things. And the same sort of thing. It doesn't actually just have to be the sunlight coming in. It could be instruments being switched on and other instruments being switched off. If you've ever sat with a laptop on your knee for too long you're probably aware that electronics start to get hot as they're actually being used. So Leesa Pathfinder is a technology demonstrator. It's looking for gravity waves. Say looking, yes still looking. I think that's going to be finishing in October sometime. It had an extended mission phase. As a technology demonstrator what we're trying to do is demonstrate that we can build something that can actually detect gravity waves and to see if gravity waves can be detected. It's an extended mission phase. That means we have actually been successful at detecting gravity waves. The first detections came around at the same sort of time as I think it's LIGA, one of the underground detectors, detected gravity waves. We've also managed to detect them in space as well. The idea with Leesa Pathfinder is that the Leesa mission would be three of these spacecraft and they'd all be around 200,000 km apart from each other in a big triangle so we'd pick it up at one and measure the impact at the other to be able to measure the size of a gravity wave. They're pretty small things. This is inside of Leesa Pathfinder. It's looking for gravity waves. Gravity is surprisingly enough impacted by maths. For Leesa Pathfinder specifically we had to measure every single item on that spacecraft and also measure its response to different temperature gradients and then analyse them numerically to see if it was going to behave as we wanted it to. Thankfully we did, which is a really good thing. We have had cases where it's not always actually come out as we wanted it to because the numerical techniques are only so good as your prototype and your testing. If you don't have the data to play with how do you know what model you're actually building? That's actually what Leesa Pathfinder looks like in real life, not just the inside of it. The solar is under this black blanket. That's just to stop it getting really mucky. There's a person there as an idea for height but Leesa Pathfinder is about my height is the short part here. Because it has all the sensitivity to maths we got rid of any maths that we didn't need during the observational phases which is all of the silver section here which is the propulsion module. The blankets are different colours on Leesa Pathfinder. Anything that's going to be in sunshine will pretty much be a gold type colour. We expected that we might get some glancing solar input on the actual module itself. The propulsion tanks are wrapped in silver blanket because the idea was that it was just going to be in shadow of the rest of the spacecraft during that phase. Leesa Pathfinder has been about 15 years in the design build test and actual launch for around a nine month mission phase. They're pretty short lived when they're the science ones but the science missions are very bespoke. My next one. This is Solar Orbiter. It's not actually Solar Orbiter it's an artist's impression of Solar Orbiter. Any interesting features anybody can see there? It's all black. Solar Orbiter is a mission that's going to be the closest thing that mankind has ever sent to the sun. It's going to be a third of the distance between the earth on the sun side of sun to earth distance. It's going to be within Mercury's orbit. So obviously having it all black that feels like a funny choice does that to me anyway. So in the front of this heat shield that will get to around 700 degrees and yet the rest of the spacecraft pretty much all electronics likes to work at comfortable body temperature maybe even less than just comfortable like I'm all right about minus 10 with a couple of coats on and 40 for holidays. Well that's not me personally but I know some people like that. That's pretty much the range that everything on the spacecraft wants to live at. So there are the sort of two conflicting ideas that we're after when we're looking about thermal control is not too hot, not too cold and not too bendy so no great big changes of temperature gradients. So 700 degrees this stretch is pretty big the front heat shield is about two and a half meters by two meters and then it's got a big heat shield. So I want to say a big heat shield that's 700 degrees in the same way as the blankets that have been passed around it is a series of foils it's actually five layers of titanium and they're all painted black and it will drop the inside of the spacecraft so where it actually connects to the spacecraft it's around 70 degrees it's a massive temperature gradient and the thickness of the heat shield is about this big so it's the passive technology it really does work but we're really really being challenged with that thermally we're actually alright to design for that kind of thing it's one of the things that we can use materials differently we can use the colours we can size things for that the challenging part of solar orbitary it's got an absolutely incredible orbit in the same sort of way as what Rosetta did so this is the solar rub to orbit so it's got a nice little arrow that says launch brilliant and then it does all these weird loops biggest loop takes it out beyond Mars and it's really cold out at Mars but we've just designed the spacecraft to be really hot on one side which basically means we need a whole lot of power to be able to manage that so it's solar rays again so that we've got enough power when we're all the way back the solar rays present their own issues they melt same as anything when you put them too close to the sun so as it gets towards the sun we can't actually keep the solar rays flat as soon as we're getting towards Venus we have to start and move the solar rays back otherwise they'll melt so we're reducing how much energy we can get on the solar rays and then there's actually a point at which we get no energy from the solar rays and that's when we're closest to the sun because the solar rays are pretty much flat so any of the light comes in and is actually being completely scattered by the layer of silicon that's on the top that stops them, that actually protects the solar ray itself and in the same way as we did for Venus Express each solar ray panel has a row of mirrors in between it so again, these tiny lovely little mirrors are just like tessellated in between so you've got a strip of mirrors, a strip of cells so that we can actually manage the heat so you've got a bit of a cold gap in between each section because the solar rays get hot as they're generating energy Who would be a thermal engineer? It turns out spacecraft are complicated So we've launched from Earth we actually go out back towards Mars first before we come back into the sun and that's so that we can get the right acquisition on the orbit What we're actually trying to do with solar orbiter is match up the speed of its orbit and the rotation rate of the sun so as it comes in towards the sun it's going to rotate at the same speed and we can actually map for a much longer duration of time what's going on on the surface of the sun All solar missions to date have been from around an earth distance and they look at the sun which is lovely but the problem is the sun turns so if you start seeing some solar activity some sun spots and things arriving and then it rolls its way out the corner so that's kind of the idea is that we can actually track how one particular aspect of the surface is going to develop The other thing that's been heavily on solar physics since the 70s is plasma physics In fact that's what I actually do in my dissertation and in my undergrad Solar plasma physics has been a big field for quite a long time and that's the sort of thing that gives us the northern lights and the southern lights is generated somewhere in the solar corona don't know all the mechanisms for that that's where the research comes in what we don't have is any spacecraft that are looking at both we don't have any spacecraft that are looking at the sun and that plasma physics all at once you might have seen the images of the sun in all its different colours there's green ones, blue ones, orangey ones they're looking at the sun in different wavelengths often they're on different spacecraft too lots of different data of different wavelengths of the plasma different images of the sun and videos that can be made out of them but we don't have anything that's all of that together so that's what solar orbit is going to do it's got a whole raft of instruments it's got 34 instruments on it looking at the plasma in seven or eight different wavelengths as well as five different lenses looking directly at the sun in all those different wavelengths what it means is the data we get from solar orbiter it means we can look at all the data we've gathered since the 70s in the light of all the new constructs that we learn from solar orbit's data so it's a pretty exciting mission if you're a physicist and then the other thing that it does because that's just not enough apart from going closer to the sun it does a vegan manoeuvre a Venus gravity assist manoeuvre so we kind of lock it into Venus and use that to slow it down so that actually we can start to look at this multitude so instead of just going straight around the equator we're going to actually start and be able to look at the poles which is where the majority of the energy for the solar wind actually comes from and again that's never been done before either so hopefully solar orbiters should give us some pretty decent data so that's definitely one of my favourite missions that I've ever worked on so back to solar orbiter it's all black it's going to a really hot place and it's all black so what would you like it to be? white yeah white, white would be good all shiny, any of that so actually the reason that it's all black is because if you leave things in space for long enough or put them in a very high radiation area for long enough it's going to go black anyway so by having it all black to start off with there's only so far that it can degrade so instead of it getting to black within three months and starting going like brilliant maybe after three months it's black what are we designing for we know what we're designing for so that's the reason that it's all black equally it's going to be in a region a very high ion density so lots of alpha particles lots of helium particles and actually the black blanket coating is fully loaded with carbon it's a bit like a big faraday cage everything needs to be stuck to one another otherwise it's going to spark and usually actually everything goes from hot to cold hot is more energy cold is less energy everything is trying to move towards a more equilibrium state and the cold is part of the space craft of these cameras they're at cryogenic temperatures so there's an idea of that front of the heat shield 700 degrees cryogenic camera that's less than minus 180 degrees colder than at the same time as this is at 700 degrees so what we end up with are these panels here the same on the other side and they're radiators they're radiating heat away from the space craft and that's how we start and control things so in space we have radiators and heaters because we have radiators to radiate the heat away and heaters to add more heating when things are too cold so when we get out beyond miles most of that is going to be under heat control to be able to make sure that nothing freezes yeah I think that's quite a lot about Solar Order there this here this is Rosetta this is Rosetta in its test chamber so this is what a thermal test chamber looks like and where you guys are sat is a really big lens it's a big bank of cameras well it's not cameras sorry it's lenses and they're usually xenon light bulbs because we're trying to match the profile of the sunlight that comes through so we can't just use infrared depending on the space craft you're looking at we can get away with infrared if you're just looking at how the thermal moves but if you're looking at how things are going to be reflected we can't get away with that kind of thing so Solar Orbiter that's been tested in front of a massive great big lamp that instead of just one solar constant which is roughly what we get on Earth is actually a 20 solar constant can't put any people in that and actually it's a vacuum so you won't want to go in there anyway so we tested them all in a vacuum because obviously that's one of the massive massive heat drivers why do we test in vacuum? it's a vacuum in space which is a good start we don't get convection so as soon as you're in space you don't get convection so all the other different disciplines they actually do an earth based analysis and then they'll do a space based analysis because for them that's really challenging whereas firmly it's like brilliant, we've got at least 40% convection there are no problems you switching things on here so it's only when you get back up into space that actually things start getting interesting so a little experiment that we've got going on here that Harriet very kindly set up for us that's not going to be as effective as if it was in space because we do have about 40% convection just by having some air so on my blankets hopefully you've all had a little cat we've got some flying leads that's because everything literally everything on a spacecraft is connected to everything else they're fully grounded so that we don't get all that sparking I can't remember what have I got any other pictures so this is actually three spacecraft together you might get an idea of that by the tiny people in the corner they're actually normal sized people it's just a very large spacecraft and this is baby Colombo and this is also going pretty close to the sun this is actually going to be orbiting Mercury we've got three different bits we've got the Mercury Transfer Module that's the bus essentially so that's how we separate everything out in spacecraft buses and payload things that people pay for buses, things that get them there so Mercury Transfer Module which is a full UK design and then here is the Planetary Orbiter which is going to be taking images of the surface of Mercury and it's going to be looking at its atmosphere and then on the very top there that's a lovely heat shield but inside that there's a smaller spacecraft and that's a MMO, Magnetospheric Orbiter so it's looking at the magnetic field of Mercury and the reason that we want to look at the magnetic field of Mercury is because it looks like Mercury may have had at some point a similar pass to Earth so it gives us an insight into what we might see in the future on Earth in terms of what its structure looks like how its atmosphere is being how that's developed and what its magnetic field might actually develop like future so we don't just do this science because it's fun but we are trying to find things when we're starting to look at different planets it gets reflected back to what we know about Earth and how different things are driving together I think do you want to have a go at a bit of testing? Brilliant so I've not brought any thermometers with us but humans are pretty good at detecting changes of temperature so we've got two halves of plates if you test the side that's been under blanket how are they feeling that feels just like regular normal chocolate that feels like regular normal chocolate can you guess what's happening in the next bit? so our blanket's been pretty effective under that heat there's some napkins there Brilliant, thank you very much help yourself with some chocolate so that's a rough idea of generally most things thermal on spacecraft the reason that thermal is well in my own personal opinion I'm not biased I promise is one of the more interesting analysis aspects of spacecraft design is because it impacts the whole spacecraft it's very very difficult to look at just one section and then hope that the rest of it's going to be around being okay around that if you're an electrical engineer you're going to have to consider noise you're going to have to consider the amount of power that's needed what lines you've got going here there and everywhere but they can look at one section in isolation and then start and move through a chain thermal you really can't it's all down to we're heavily driven by radiative exchange so temperature to the power for is very much how much it can see something else so batteries I'm going to go right back to one of those first slides in here if you want to make sure that something is an interaction with the rest of the environment you wrap it in shiny stuff there we go so we've got all the electrical harnesses here the batteries were also covered in a blanket because batteries get very very very hot and they get too hot for much of the rest of the spacecraft to deal with and it means that when it comes to testing that we actually can't always test everything to its upper limits but we're trying to test the whole spacecraft system so there's quite a few bits that go into general spacecraft design but thermal is definitely on the interesting side of things you get to work with the electrical guys the mechanical guys mission systems, communications anything that has power in it's going to get warm pretty much yeah okay I think I'm going to stop there does anybody have any questions thank you thank you