This week, AB has an amazing chat with Paul Stevens, CEO of Voltitude, a company focused on exploring and unlocking the potential of the stratosphere for research and commercial applications.

Paul discusses his background working on the Zephyr program at Airbus, developing solar-powered high-altitude pseudo-satellites. He explains the challenges faced in designing aircraft that can maintain their position in the stratosphere while balancing the delicate energy budget. Paul and his team at Voltitude aim to overcome the vulnerability of these aircraft to gusts and turbulence during ascent and descent, expanding their operating envelope.

Voltitude is currently exploring the use of small, low-cost, biodegradable latex balloons to carry meteorological sensors (dropsondes) into the stratosphere. These balloons can drift for several days, dispensing dropsondes that transmit atmospheric data as they descend to sea level. Paul discusses the regulatory framework for high-altitude balloons and the potential for using machine learning and AI for mission planning and route optimization.

Connect with Paul on LinkedIn at: https://www.linkedin.com/in/paul-stevens-b07b0382/ or on the Voltitude web site.

We’re also publishing this episode on YouTube, if you’d like to watch along in full living colour: https://youtu.be/_d5wYy14mx4

Chapters

07:14 – Voltitude’s Current Projects

Paul discusses Voltitude’s current projects, including the use of small, low-cost, biodegradable latex balloons to carry meteorological sensors (dropsondes) into the stratosphere. These balloons can drift for several days, dispensing dropsondes that transmit atmospheric data as they descend to sea level. He also mentions the regulatory framework for high-altitude balloons and the potential for using machine learning and AI for mission planning and route optimization.

19:15 – Super-pressure Balloon Technology

Paul discusses the possibility of miniaturizing super-pressure balloon technology to create a more sustainable and tactical delivery system for environmental sensors. He explains the differences between zero-pressure and super-pressure balloons, and the challenges involved in designing a lightweight, long-endurance system.

35:24 – Improving Aircraft Resilience

Paul discusses Voltitude’s efforts to improve the resilience of highly aeroelastic aircraft to turbulence and gusts. He explains their approach of using sensors to detect deformations in the aircraft’s shape and actuators to control the lift distribution, restoring the desired shape and flight control authority. Paul also mentions the potential for using AI to preemptively adjust the aircraft’s shape based on sensory inputs.

Transcript and Links

AB
Well g’day and welcome to Episode 25 of SPAITIAL. If you’re watching this, it is a lot darker, all my coloured lights are a lot brighter, something’s happening. Yes, it’s my evening. Why? That’s because I’m talking to a very special guest today.

A big welcome to Paul Stevens – coming to us from sunny UK. Yes, I get to use those two words together in the one sentence. Paul, g’day, how are you? Welcome.

Paul
Oh hello, thank you very much for having me. It’s great, I’m very well, and it is indeed sunny. In fact, we’re having a little heatwave, so a lot of confused British people.

AB
Okay ‘heat wave’… I must ask the question. Weather check, what do you mean by heat wave per se? What’s a UK heat wave?

Paul
Well yesterday it was 31 degrees. Which is very uncomfortable for us British folk.

AB
That is “everyone to the beach”, “everyone grab the flannels” and start to, yeah, okay. Well done. That does count as a nice heatwave. Well done!

Paul
Well, that’s saying is something from somebody who’s used to heat waves.

AB
True, true, well, days of 40 aren’t too bad – it’s when you get five days in a row and when the can of beans in the middle of the house in your pantry is also 40 degrees, when the heat is just leached in from every side, that’s a good heat wave, but still, 31 in the UK, you get top marks for that.

Now for the record, Paul and I met a couple of months ago, we actually met at a, let’s call it a conference in, let’s say, northern Europe, that’ll do, but we actually, like ships passing in the night, we both, I think, heard each other’s five-minute intro lightning talk and then we’re in different streams the entire few days and on the last day, we must catch up, we must have a chat.

This is that chat, this is the time to actually finally do a final deep dive to actually ask all the burning questions which you didn’t get to ask back then.

So, Paul, you are CEO of Voltitude, which is a lovely company, which has an awesome name and I love the fact that you’ve got yourself, Paul Stevens, and then your two of your partners are Steven and Stephen, your meetings must be ‘Steve-o’, ‘Stevie’ and pretty problematic?

Paul
Yeah, we need to work on our diversity statement. People other than Steve are allowed to join Voltitude. Although it may surprise you that there are a total of four Steeves in a 12 -man team.

AB
You’ve hit the KPI for the year, I think even for the decade, so well done!

Voltitude does some astounding work and it’s definitely in a area of geospatial AI data science that is literally on the edge. You are playing with the highest of altitudes. You are playing with the highest of latitudes. Can you give us a easy then a medium and we’ll save the hard explanation for where do you play? What are the sort of things that you are actually doing?

Paul
So to tell you a story of why we are obsessed with the stratosphere and what you can do with the stratosphere. I’ll just fill you in a little bit about my background, how I got to here. Awesome.

So prior to 2020, I was working for Airbus on the Zephyr program. So Zephyr is a solar powered, high altitude, high altitude pseudo -satellite. And what they mean by that is that it is a very special type of plane that can cruise day and night only on the energy it’s collected from the sun through very efficient solar array and hold that in extremely high specific energy density batteries.

And by building such a craft, we can effectively create a near perpetual flying machine with interesting properties. It’s a bit like a satellite in that it’s got a very large field regard, but it has aerial resolution.

So it’s an interesting blend between the resolution capabilities of aerial sensing and the huge swath and low cost per meter square of space. And so we were developing this platform for Airbus. And I must say it was a two decade obsession to make it work.

Paul 04:56
And I was the head of design. So I had a career high in 2018 when we demonstrated all the key enabling technologies that come together and made it possible to design an aircraft that could hold itself in the stratosphere, cruising day and night and balancing this delicate energy budget.

So you might say, well, why have I changed, disrupted the ecosystem and disappeared from what was an amazing program. And yeah, it was simply two aspects really. One, I was really interested in opening up the stratosphere to other applications, which were perhaps not only defense related and not only connectivity related.

I was really interested in Earth observation. And number two, although we have demonstrated the energy budget aspect of designing these aircraft, which I’ll explain in detail in a moment, although that aspect had been solved and we could now hold a plane in the stratosphere day and night for months on end, the type of aircraft that can do this are extremely vulnerable to gusts and turbulence when they climb to and descend from the stratosphere.

And this vulnerability I saw as the Achilles heel for the entire industry. And we thought that there was some, the next challenge was to solve that, but without detriment to its performance in the stratosphere.

So, you know, I love, I love working for Airbus, but there are certain things you can’t do in a big corporate environment. And so my friends, my colleagues, my design team, basically we’ve joined up in altitude.

We’ve made a clean break from Airbus and our challenge is to open and unlock the stratosphere to a whole range of new applications and to overcome this Achilles heel for the industry so that we can expand the operating envelope of these unusual aircraft.

And so that’s, that’s how, that’s the story of how I got to here. And so I’m joined in altitude by my former design team from, from Airbus. We’re still on talking terms with Airbus. We’re not persona and vatius, fortunately.

And the journey since then has been to test the utility of the stratosphere for interesting new applications. And one of the first applications we wanted to explore was getting really high resolution meteorology data from remote areas.

And so we took a step back from fixed -wing solar electric flight, and we have started to explore the benefits of really, really small, low -cost, largely biodegradable natural latex balloons, and their ability to float for many, many days in the stratosphere and reach, just through drifting with the winds, reach remote areas, and to then dispense tiny meteorological sensors, it’s called dropsondes, which fall all the way down to sea level, transmitting their observations back to the balloon. And then that data is then disseminated via SATCOM, and we receive that, do some quality checking, and then send it out to our data customers.

Paul 08:18
And so it’s a really simple, it’s a reinvention of a very old idea. So cast your mind back to the 1940s, in the thick of World War II, perhaps, and as a terror weapon, the innovative Japanese were launching arrow -triggered, vented balloons to drift in the jet stream across the Pacific Ocean.

Yeah, across the USA. And drop incendiary devices onto the USA. I don’t know for certain if anyone’s ever killed, but as a terror weapon, it was incredibly effective. Gotcha. So we thought, well, you know, let’s not terrorize people, try and do the opposite.

And let’s try and solve societal issues and help improve the forecasting of extreme weather events. And so what we’ve done is fit a standard meteorology balloon, latex weather balloon with a vent and a ballast bag so that it can control its height.

It doesn’t go up and burst. It controls its height. We can set a height which corresponds to winds that will are desirable for our drift direction to take us to an area of interest. And then we can drop tiny, tiny dropsongs.

Our dropsondes are about 20 grams in total. There are some insects that are heavier than these dropsongs. And these dropsongs are stored for many days or weeks at a time in the stratosphere. We resuscitate them, we warm them up, we charge the battery, and we dispense them.

And about 20 minutes later, they fall all the way down to sea level. And all that way, they measure temperature, pressure, humidity, wind speed and wind direction in very high vertical resolution. And all of that data is then collected. And we send that to our data end users. And it’s all in near real time.

AB 10:16
Look, I must say, I’ll put the link to your products page in the first thing within the show notes. Stratus Sond. StratusSonde, am I saying that correctly?

Paul
Yes, a combination ‘dropsonde’ and ‘stratosphere’.

AB
So sold on trademark like that, but the image is there. I mean, you really are showing pennies and, yeah, pence there for size. So how long can that parent balloon stay aloft? What’s what’s the sort of the mean range of days or is it measured in weeks?

Paul 10:48
So those balloons are really basic. It’s a very high value system. It’s a bit like the explanation for why do they have finite life? If you can imagine this ball of buoyant gas, every day when the sun sets, that gas ball cools and it loses buoyancy and to prevent it from sinking all the way down to surface, it has to throw out some things it doesn’t need anymore.

And so we dispense harmlessly, we dispense sand. So sand trickles out of it and falls away. And that reduction mass catches the drop in buoyancy. And so every day, a bit like compound interest, negative compound interest.

You’re just paying it forward.

AB
And eventually you get to a point where, gotcha, gotcha. It runs out of ballast. Gotcha. So, um, days or cycles, do you mean days or sun cycles?

Paul
Yeah, we we get about in the tropics, we get about five sunsets at high latitudes. We get a few more maybe in theory, we should be well in excess of 10. But we find that the UV degradation of the latex envelope then causes it to burst.

And so really, you can only really count on about five or six days. And in that time, you’re going to be able to drift to somewhere interesting. And, you know, regularly distance your drop songs and we carry up to 10 drop songs on these balloons.

So it’s a and they’re really small, you know, one person can launch them, it’s very low logistics footprint. And so any if you’ve ever watched me trolls as small just standard weather car is exactly the same.

AB
Any priming of the, what’s the, is there much of a CPU or a black box or is it just comms and hardwired and it’s just a slave?

Paul 12:59
Yeah, there’s a little computer on board which manages everything, there’s a default mission plan which usually works for most missions, but if it doesn’t, once airborne, our operations base in Farnborough can send it a new mission plan, and so really it’s a case of somebody who really knows nothing about the system can inflate a balloon with buoyant gas and release it.

They don’t really need to be able to program it or anything like that. It’s very hands -off, very simple, and then it’s all managed centrally, and indeed, we don’t even have somebody watching it all the time.

We have a computer generating a mission plan for each balloon, and that’s worth talking about because it’s crying out for its own talk, which is all about machine learning and artificial intelligence on planning routes through a complex wind field. You have the platform.

AB
You’ve got time, you’ve got altitude, you’ve got the cycles to contend with – you haven’t got battery life per se – but how do you chart a four dimensional path – a complex route?

Paul 14:10
I’m going to disappoint you really badly here because we’re a bunch of Luddites and what we do is a large scale Monte Carlo simulation where effectively we tell synthetically a balloon to change height to all possible altitudes within a certain resolution and every six hours it changes back to all other possible altitudes and this Monte Carlo simulation of all possible outcomes for this balloon over the next five days is computed.

It’s an end to the power of wide problems. But with modern computing, this is done within a few seconds. So there’s a probability map of where the balloon could go. And so we highlight where we want it to go and all paths of truth that lead to that location are identified.

We can wait each branch and say, well, what’s the common factors here? Which branches in this decision tree hold the greatest likelihood of getting to where we want to at the right time?

AB
Mission ‘set and forget’ you can tell it what the mission vaguely is and unless it goes outside those parameters because of Hurricane X comes along chances are it will converge close to that mission profile

Paul
And of course, you know, the world’s heartbeat for meteorology is about every six hours there is an update to the global forecast. And of course, in six hours, the balloon has made some progress along its planned track.

And so every six hours, we automatically rerun the mission planning system with fresh data, with progress. And that is then said, you know, progress and fresh data and differences are fed back in to create an enhanced track prediction.

So in a sense, we are vectoring in, as time goes by, but the whole complexity of this is is is rife for modern thinking and modern machine learning principles and artificial intelligence and, and so on, so forth, to be thrown at this to because as we as our constellations get larger, it’s inconceivable that we should be doing this on a balloon by balloon basis, and that there are certainly better ways to do this to coordinate the

AB
How many do you have up at any one time? If it is in known numbers, it’s a great thing to always ask a potential client, what number would make you change your thinking? So 10X, some people go, oh yeah, 10X is fine. Okay, well, if that’s fine, how about 100 or 1000 x?. At what point in time would you have to transition to using it like a, and here’s the gnarly question, what’s the collective noun for a group of smart balloons?

Paul
I’m not sure, but I know what the collectives now for Radiothorax scientists are, and I’m sure it’s probably something like a disaster of transparent engineers, I don’t know. Our busiest time of year is the tropical cyclone season in the Atlantic, and we’re hoping to branch out services into the Pacific.

But at the moment, we rarely have more than between five and 10 balloons airborne at once. So with the numbers nice and low, we can take this rather clunky methodology and keep it going in an automatic sense that humans really don’t have to, well, aside from launching them and deciding at an executive level what the mission should be, humans are no longer interacting.

The drops ons are scheduled, the path of the balloon is automatically being modified and evolved in response to new forecast data and progress. But the answer to your question is, at what point does it become, you know, do we need to evolve?

It’s really, really soon. If we are successfully expanding services to the Pacific, we really should be doing it straight away. And related to your previous question, which is, why are the balloons only five days endurance because of this compound interest effect of cooling on the buoyant gas?

Well, there are other innovations in balloon technology which could benefit from being reinvented in a much smaller form factor. And we’re exploring really small super pressure balloons, which is another type.

So what I’ve been talking about is a zero pressure balloons, the balloon which has a vent in the bottom effectively. And if it wasn’t for the fact that latex is elasticated and trying to squeeze the buoyant gas out of itself, if it was just a parting bag, this would be called a zero pressure balloon.

And it’s one where each day that cooling effect causes it to have to dispense ballasts and retain its buoyancy. A different type of balloon called a super pressure balloon is one where the envelope and the gas inside it is under a small pressure.

And that pressure is large enough such that even during that cooling cycle as the sun sets, there is still a positive overpressure in that envelope, even at the coldest point of the night. And by achieving this, the balloon does not change density.

Paul 19:49
And so they’re often called constant density balloons. And what we have there is a really long endurance balloon able to float almost indefinitely if it wasn’t for a fusion of buoyant gas through the balloon film.

And so this is if you think of perhaps some of the really large balloons you might have seen doing scientific missions operated by the likes of Aerostar International or even the Chinese spy balloon that we all came to early with 10 years ago.

Those were examples of super pressure balloons, very special super pressure balloons, which are able to fill an emptier ballonet inside them and to control their height and benefit from this remarkable feature, which is that they don’t change their density on the sunset to give really long endurance and altitude control.

And so one of the technologies we’re exploring is what is the smallest balloon of that type that you can design practically and has all the requirements.

AB 20:58
And is it still the on back of a single person, back of a car, the graphical, comic-style Swedish furniture maker instructions – not a list of instructions a mile long? Is that, so the super pressure balloons, are they managed by teams on the ground? Are they tenfol- sized today?

Paul
At the moment, really the smallest commercially viable super pressure balloon carries about a 50 kilogram payload underneath it and is a really large envelope. We’re talking maybe 15 to 20 meters in height and a really huge volume of buoyant gases used in that process.

It requires a substantial team to launch these things. I would say it’s still pretty tactical. You could turn up with a Land Rover or a truck with all the equipment needed to do that, as well as another truck with all the buoyant gas cylinders.

It’s a 10-fold, maybe even 100-fold increase in the effort to get one of these things airborne. They’re a mature technology. I think the world record is about 250 days, which is really impressive and hats off to those people.

I think the average is more like 60 days, but it’s a really interesting field of endeavor. High altitude balloons are afforded an unbelievably welcoming to aviation via the regulatory community. The regulations are common sense, not the sort of thing that you find in conventional aviation.

They are very operational risk assessment. It’s very lighting. It’s all about the operational risk assessment and ensuring you operate your balloon in a way that is safe for the general public, knowing that all balloons end their lives in what aviation would call a catastrophe, a crash.

They will always fall from the sky, hopefully under their parachute. That’s the end of their life. They’re a single -use system. Remarkably, the regulatory world has embraced this principle and afforded huge freedoms for innovation.

We see the efforts to miniaturize super pressure balloon technology to something that’s really quite small and tactical and as sustainable as possible as a potential new and disruptive delivery system for environmental sensors of the type that we do.

AB 24:08
10 or 20 times the number of the songs the the small yes you would and then you would need better comms and better mission planning to To actually push them in the right direction for longer. So you

Paul
And it’s a real challenging system engineering optimization process. An altitude changing super pressure balloon needs a compressor and a compressor that works up there in the stratosphere at 30 millibar.

And it needs solar arrays, it needs rechargeable batteries, and it needs a mission system. And it needs this high tech envelope, which is ultra thin and ultra lightweight and able to withstand the mechanical strains of this overpressure that keeps it in this constant density mode, but also allows you to fill and unfill a ballonet to deliberately change its density, to change its altitude and actually navigate.

So there’s a minimum capital of mass of system to go into this product to make it viable. And in the system engineering optimization space, it’s very easy to chase your own tail into nothing and find that you produce a brilliant system, but there’s no payload capacity or there’s no excess power to provide for a payload. Correct, it’s almost the opposite of that.

AB
The famous line of ‘the best part is no part’. That’s true but when you’re left with just a balloon you’ve removed the bits that make it viable!

Paul 25:48
And it’s probably no surprise to you or anyone listening that the available mass fraction of a system like this, available to its payload, gets smaller, the smaller the overall size of the platform.

So at some point, it is just not possible with current technology to make it smaller than a point of commercial value. And we’re exploring that point at the moment with some projects we’re running, and exploring whether or not they offer disruptive new services for Earth observation and meteorological data collection.

I should mention that there’s a sort of regulatory, I’ve said the regulations are very lax, there are regulations, and a really convenient threshold is for meteorology boons is if you can operate in what’s called the light category, which is where your total payload mass has got to be less than four kilos.

And payload is considered to be anything that’s hanging under your balloon. So it’s not just your, your box of tricks that are paying you your your livelihood, it’s all the things that everything else.

Yeah, all mechanical things and everything, all the critical systems to make the balloon work. And so four, four kilos is a key threshold, because the world in 1945, at the International Chicago, civilization organizations inaugural conference, set out some rules of the air.

And they said that balloons of a light category used exclusively for meteorological purposes, can be allowed to cross international state boundaries without prior permission. Okay. And so this is like a revelation of global freedom for a balloon in a weight, the light category can go anywhere without prior conditions.

You must ask for permission to launch it from your launch state. But but once it’s airborne, it’s allowed to go anywhere. So, so being in the light category, an engineering of balloon that can be so light, that it can do all these amazing capabilities in that tiny weight constraint, suddenly opens up global freedom.

And so that’s the, that’s the exam question. I don’t have the answer, yes, whether it’s a commercially viable solution. Well, we’re doing some great prototyping. And we are optimistic that there is a system hidden in there somewhere that allows us to open up a new application to the stratosphere with a 10 fold capability.

AB 28:41
Existing’s like looking forward to that and also you mentioned earth Observation so of course dropping little droplets, you know, 20 gram things behind you that can sense is still you know Astounding I need to talk to you about comms in high Altitude and high latitudes, but what sort of earth alps would you be thinking?

How do you put a… You don’t want a wide-angle camera you want the longest super zoom in the smallest package are there Throw away cameras of that nature or parachutes and you retrieve what’s the what’s the size weight and power?

What’s the what’s the delicate balance you’re aiming for in that kind of world?

Paul 29:22
Yeah, I should say we’re probably not seriously exploring conventional Earth observation using the principles of remote sensing, a long focal length optical system staring down the surface and retrieving imagery.

We do use our balloons for test and evaluation purposes and indeed we have a steerable parachute. So when we carry a high value payload to the stratosphere, we can conduct multi-day tests at a really low cost because our balloons are so cheap.

And we’ve got a reasonable chance of not just navigating the balloon to within land, but then releasing this steerable parachute and navigating that back to do a spot landing and retrieve a high value payload.

So you can imagine the industry of fixed-wing solar electric, high altitude satellites is still in this infancy. And there are a lot of payload developers exploring the solution space, which is a really demanding size, power and mass envelope.

Paul 30:45
And there are very few successful operators of these planes at the moment. So there’s a very long waiting list to get to the front of the nose of one of these aircraft with your payload. And that’s not very helpful if people want to do a real world full system test before the embarrassment of its failing on one of these precious flight opportunities.

So there’s a mini market in providing test and evaluation services on balloons. And I would say that’s probably the only time that we remotely get close to what you would describe as Earth observation using multispectral, hyperspectral sensors.

However, I would say that our efforts and technology relating to fixed -wing aircraft to expand their operating envelope, which I can talk more about, and to get those aircraft more regularly transitioning through the troposphere to and from the stratosphere more successfully opens up all kinds of commercial applications, which currently are priced out because the platforms are just so vulnerable and they keep crashing.

AB 32:07
A two-stage, a high-density atmosphere, low altitude transitions to a different mode of working or a way to protect or pardon, that’s the toughest power to weight ever surely?

Paul
Yeah. So I’m hoping you’ll love the simplicity of the solution that we are pursuing. So when you analyze why these aircraft crash when they’ve encountered gusts and turbulence, it’s very rarely that they were not strong enough.

The problem they encounter is that by prioritizing within their design, this energy budget in the stratosphere, the need to be able to cruise on so little power. And we’re talking powers equivalent to human powered flights.

I’m sure you’ve seen these athletes pedaling as fast as they can to get airborne and cruise just above walking speeds.

AB
Ah! I went down the YouTube rabbit hole a few weeks ago, I’m gonna say Japan and I’m gonna say 60 kilometers? I watched a bird man cycling and he just kept on going. He actually had to stop because his muscles were cramping up.

Paul
It’s amazing – the English Channel used to be the reference mark for for success But these modern athletes doing this sport are doing you know, 60 kilometers, which is huge a huge distance But they are super human.

They they’re able to produce a lot more useful But so it’s a very similar problem, how do you how do you close that energy budget in the strategy? the answer is fly with minimum power required to cruise and Casting your mind back to your your school years.

I’m sure you’ll remember that drag is proportional to velocity squared. And if you can still remember these classic physics equations power is drag times speed so a Velocity squared for drag times speed again is a velocity cubes term So the power required to cruise is a V cubed relationship So the in the biggest lever you have is to reduce V right?

So you have a really slow flying aircraft up there in the thin atmosphere. It has to fly pretty fast to generate lift But it’s still you know It’s still gonna get there and the design space solution is a really it ends up with a really wide wingspan very high aspect ratio and incredibly light and very very low wing loading and With a distributed mass so it is a you know There’s no central point like a passenger carrying aircraft whether the fuselage let everyone sits and a strong stiff wings holding that you can’t do that with these aircraft You’ve got to distribute all of your your mass uniformly across this this flying wing.

And the net effect is it’s it’s incredibly easy to deform it’s it’s displays very strong aero elastic properties Okay, what I mean by that is the serious wings twisting.

Paul 35:24
Yeah forming bending torsional effects and And that’s a byproduct that comes from prioritizing the minimization of mass on your aircraft and And the issue there is that when a plane of that type encounters a gust or some turbulence It might be designed with a little bit of dihedral the dihedral is a sort of v -shaped your wing Great and it gives a gives you all aircraft role stability It’s a it means that even with no flight control system on board a role will generate more lift on the on the downward hanging wing Naturally restoring it to stable flight and And so most aircraft are designed with a shape in mind that gives them their optimal flight control authority And the problem with these really aero elastic aircraft is that when they encounter, you know strong or moderate or even light turbulence the effect can be the shape changes completely right and the the the aerodynamic derivatives the stole the Stability characteristics of this can you say lost momentarily or for yeah.

Yeah, it could be lost for many tens of seconds We’re talking about a very slow train crash Yeah, and and the problem is this this is these aircraft once they’ve lost their stability characteristics They they find themselves in a kind of divergent runaway situation Where they might have lost role control.

They might be entering a spiral dive They’ve got no way of coming out of it because the shape has changed to one of zero role control it might have been turned to instead of having dihedral I’ve gone to and he drove and And so this for aircraft Yes And so just gets faster and faster and faster until eventually it just breaks up There’s there’s too much too many aerodynamic forces on it and the structure fails and so You know the step one in our solution is to tell the aircraft what its shape is.

So MEMS technology is super light super lightweight as a key enabler for the solution is to cover your aircraft in Sensors that allow the aircraft to know its shape Wow and the in the second Attribute of our system odds our solution is to give the aircraft an ability to change its lift distribution across its wing To allow it to vary its shape back towards its idolized shape So if it finds itself encountering a gust that deforms it in some way Maybe makes it bow in the middle or even accentuate We can get the aircraft to sense that deformation has occurred and actuate devices which will change the lift distribution to restore the shape, to give it flight control authority back to control its flight envelope.

AB 38:37
getting a simple descent of mechanical help in those extreme situations to pull it out of the deadly dive?-

Paul
Actuators usually cost you mass, and people are familiar with some of the actuation systems on a conventional aircraft. I’ve probably heard of ailerons. So, ailerons are a trailing edge device. They sit on the trailing edge, and when they move, they impart a torsion into the wing.

Now, normally wings are stiff, and all the planes that you and I travel on, for all the tempers, they’re really stiff, strong aircraft, and ailerons are great for that. But on a highly aeroelastic aircraft, like a solar -powered HAPS platform, ailerons are terrible, because as soon as they deflect, they impart a torsion, the wing will twist, and they can result in

AB
You can’t about turn it into an oscillating mess and yeah

Paul
It would be a disaster. And the only way of making such devices work is to stiffen up your structure and add more and more mass. And eventually, you can no longer close that energy budget in the stratosphere.

Paul 39:52
So we’ve been thinking about ways in which we can control this lift distribution, control the lift generated by all parts of this wing without imparting torsion into the wing. That’s the key factor. And I’m sure you’ve heard of a spoiler.

So a lot of cars have spoilers on, they dump lift. When I was 18, I had a very, very underpowered car. And I think it was a spoiler. I didn’t need it. But I thought it was cool. So spoilers are really great at destroying lift. And they’re really simple actuation devices. They don’t need to be very small. actively put some pretty much a binary off on off on click it into the air stream to just suddenly bring things back in milliseconds

Little fences can pop up here and there to disrupt the lift, and so for very little sophistication in your actuation system, you can really have quite profound disruption of lift for very little mass or electrical power, and that’s why dumping lift is a really great solution to the exam question, which is how do you dynamically vary the lift distribution of an ultralight air elastic aircraft to control the shape of that aircraft as it transitions through turbulence and gusts and other features.

AB 41:22
Do you train such a system? Are there known rules for such a system? Is it is it a known set of ‘if this then that’? or does it have to be put through simulations? And dare I say it a small AIML to try and simulate this thing up in this up in the upper reaches?

Paul
There is certainly a solution derived from conventional control theory, with a like a super loop around your conventional flight control loop, which is maintaining the shape of the plane.

However, the really sexy part of this is that there is the potential for AI to preempt based on some sensory inputs, particularly if you’re able to sense disturbances before they’ve even reached the wing.

Paul 42:11
So just like a meter in front of the wing edge, you know, there is the potential to have a signal that says the last time this happened, it was strongly correlated with the following events. So why don’t we pre -end that.

AB
Things like radio interference between the nose and the wingtip things like that or?

Paul
Potentially, yeah, this is an area that we are road mapping into our technology. At the moment, we’re trying to get the conventional control theory solution working in an optimized way. But using old school engineering, the results are dramatic.

We were able to halve the bending loads in a structure, compared to a system without this technology. And we’re able to double the speed envelope. So we are able to control an aircraft back inside its normal cruise range from a position that would have been disastrous without the technology.

And so suddenly, this means that these aircraft are a lot more robust. They still fly very, very slowly, because the drag is still the enemy of the power budget. But they can withstand moments of very high speed flight and safely control themselves back inside that conventional flight envelope.

AB
And while the effort to make them still might be intense, they are long lasting, but the fact that you will have the confidence to know that it will be up in the air for longer and survive squalls and survive the unknowns better, that certainly makes it a much more viable per payload proposition.

Paul
I should admit, though, that like everything we do, it’s a reinvention. And anyone listening to this who’s a keen bird spotter may have watched large wingspan birds soaring on the winds. And they may have noticed that when they hit a gust, they let their wing deform.

They let the wing take a new shape. The bird’s bones connected by tendons and those tendons allow the bone to let other joints deform. If they didn’t, they would break their wing. The loads would become too great.

They’d snap a bone, they’d die. So they let their wings deform into new shapes and shapes which would not allow them to control their flight envelope.

And a bird is covered in sensors every single feather. Every single feather is a sensor for them. It connects to their nervous system. They have acute awareness of their wing shape. They’ve got acute awareness of the lifts affecting their wing.

Paul 45:01
And so they follow exactly the same algorithm. They sense that a deformation has occurred. And their priority, when safe to do so, is to restore the idealized shape. Then to restore their flight envelope and then to restore navigation on their mission, which was probably to hunt some small rodents that they were chasing.

And the effect interrupts why it seems to be that they’ve lived for another day.

AB
I think that gives you a definite good method of name for your next project for the I mean we’re talking Condor We’re talking we’re talking the largest of large birds. So Paul that is a phenomenal phenomenal journey from weather balloons with smart devices the Drops ons falling on ahead the size of a less than a coin.

So we should be too worried going from that to from zero pressure to Stable pressure brushes gotcha Cheers and then going from the Chinese spice at Spy balloon size down to can your company make something that is you know truck single-person deployable?

And then not only have you come from the largest solar-powered long lasting astro spheric You know fixed wing you now try to already design the next flavor of you know Better faster cheaper or in this case longer lasting and you know better bang for your buck More resilient more resilient able to leap tall buildings and survive for longer Paul.

That is an astounding journey. I don’t don’t think we’ve actually touched the sides of it I actually love to have a chat to you again in a little while if that’s possible and we’ll come back and talk about the communication sort of things you’re doing what data you can actually play with and Catch up and see where you’re going on both those two next -level challenges that you’re facing

Paul
Sure, it’s been a pleasure.

AB
Where do people find you, where’s the best place? We’ll have links to Voltitude, and to LinkedIn for you. Any other places people need to reach out and find you?

Paul
Well, I’m usually fairly vocal on the conferences I attend. I go to a lot of meteorology conferences.

AB
I must say, I’ve been living vicariously through your LinkedIn feed, Paul!

Paul
The EGEU is an annual one – the European Geological Geosciences Union – is one I frequent and anything to the tropical cyclones. I go to those, so if you’re interested in the stratosphere, meteorology, all those things I’ve been talking about, look out for me on LinkedIn and through our website, I’ll be posting which conferences I’m going to.

I’d love to meet up with anybody who’s interested in having a proper, a proper, you know, geek to geek conversation about this. So you can probably tell I love to talk about this. It’s a real passion and I love the physics.

AB
Such an amazing field – and you know you wouldn’t start as a teenager saying ‘I want to do this’, this is obviously you jumping from one insight to another to another – you’ve obviously seen what’s coming and you’re getting ready for it.

It’s heartening to hear, Paul – thank you so much for your time.

We’ll leave it there and we’ll catch up with you hopefully in a couple of months definitely when you’ve got the next product ready to go but also we do want to talk about data and the data science coming off these devices

Paul
Thank you so much.

AB
Well, that’s it from Episode 25 of SPAITIAL, We’ll catch you on the next episode. From myself here and probably the plethora of cats that’s been walking behind me if you’re on YouTube we’ll say farewell and we’ll see you on the next episode.

Bye bye.

HOSTS

AB – Andrew Ballard
Spatial AI Specialist at Leidos.
Robotics & AI defence research.
Creator of SPAITIAL

_{To absent friends.}