Embedded - 282: Tin Can Through a Wet Noodle

Episode Date: March 21, 2019

We spoke with Laughlin Barker of OpenROV (@OpenROV) about underwater drones, underwater navigation, underwater exploration of the Antarctic, and extraordinarily large (underwater) jellyfish. Watch this video of a Trident ROV being eaten by a shark… yes, you get to see the inside of a shark. S.E.E. Initiative: Science Exploration Education from National Geographic Laughlin left us with a coupon code for the Trident ROV. Please remember to invite us along on your ROV’ing.

Welcome to Embedded. I am Elysia White, here with Christopher White. And I would really like to say that this week we are roving reporters. You'll get that joke in a little while. But our guest has actually joined us in the studio. Welcome to Lachlan Barker. Hi, Lachlan. Hi.

Thanks for joining us over here. Thank you for having me. Could you tell us a little bit about yourself? Yeah. So I'm, let's see, mechanical engineer by training and undergrad. But at the moment, I'm a systems engineer at Open ROV. We make small, low-cost, underwater, remotely operated vehicles. And I got started doing underwater stuff a number of years ago, working in the Antarctic, supporting NSF science missions, deploying ROVs and instrumentation underneath the ice in the Ross Sea, working on an icebreaker at one point, and then kind of miscellaneous contract related underwater things in between field seasons. Thought I wanted to get my PhD at one point. And so I started doing that

in Baltimore for a while. And that was in underwater navigation and state estimation. Decided maybe that wasn't the right move and then came back out to california about 18 months well about a year ago and i've been back at open rv since okay i just i'm like navigation state estimation underwater antarctica i have all these questions but first we're going to do lightning round cool and you've heard the show so i'm not going to explain christopher do you want to go first who would win in a fight a a penguin or an ROV? Penguin. Despite the possibility of breaking federal laws if you answer in the infirmative, have you ever pet a penguin?

No. Do penguins care about ROVs? No. Who would win in a fight between a Roomba and an ROV? ROV. What temperature is cold? Minus 200 C. For me, it's 62 F.

Have you ever personally lost an ROV to the depths? No. Have you ever had one freeze in the ice? No. Almost had one stuck, though. How close is real life to the abyss oh uh they they touch there's there's a there's a a uh a boundary there does it lead to monsters i think it just leads to the unknown okay oh but that's a boilerplate question. Yeah, but you had a good answer, so go ahead. All right, what's a tip everyone should know?

Two is one and one is none. That's mostly talking about spare parts. I've heard that on mission-critical things. Yep. Usually from military guys. It's true in the Antarctic as well. I imagine. Okay, openROV.

This sounds like a company that is making underwater remote-operated vehicles that are in some way open. Yeah, so OpenROV started in 2012. Eric Sackpole and David Lang Lang and they launched a Kickstarter and the idea was that they wanted to make these low-cost, accessible, remotely operated vehicles. And so they started out with a kit that first launched on Kickstarter and it was cut out of acrylic sheet on a laser cutter.

All the electrical, mechanical, and software was hosted up and still is on the Open rov github page so in theory if anybody had a laser cutter uh they could download all the files cut the parts out um you know spin your own board all the gerbers and schematics and everything were up there um and then flash it with the appropriate um software on the sd card and you'd be up and running with a little rov um so that's you know a pretty big barrier to entry because you need a lot of tools and stuff to do that. So instead we sold the kits. And there were these little shoebox-sized ROVs.

And one of the driving themes behind this ROV was that you could fit it in a backpack, you could take it on an airplane. So we were beneath the 100-watt-hour limitation that you run into with with lithium uh batteries on airplanes um but you could literally just literally fit it under uh the seat of a commercial airliner and then take it anywhere you want um so uh open rov transitioned um for you know we saw even with these kits when all the parts were um given out to uh or sold to folks there's um

it takes quite a bit of maker skill to be able to put it together well to withstand 100 meters of depth um and if you were very diligent you made sure all the surfaces were good and you had good glue joints um you know you could you could make a hundred meter rov and and it would do exactly what um you know you thought it would um but it was also tough for a lot of folks because that that level of like spending an entire weekend and being very diligent and detail-oriented um left a lot of folks out and from that ability to go and explore the ocean and so we thought well um we should make something that you know that anybody can just buy and then literally pull out of their backpack or out of the box that it comes shipped in and be ready to go. And so that's what motivated the creation of the Trident ROV.

And all of the Trident ROV development occurred before I came on about a year ago. And so things were just ramping up in actual production when I joined last year. So there's been quadcopters in RC. That whole field has kind of exploded, and they've gotten more and more sophisticated. And the technology in those is well-known. Brushless motors and the battery technology

and the radio stuff is all advanced. How does an ROV differ from that? What are the hard problems about going underwater versus going in the air? Yeah. So pressure and the corrosive and conductive nature of water, especially saltwater, are the big ones. The Trident ROV is an injection molded plastic shell. And the entire shell itself is actually a pressure vessel. And this kind of goes in contrast to traditional ROVs that have been made for a number of years where you have cylindrical ceramic aluminum or other exotic material pressure housings, and then you build fairings and chassis around them. So we've got this injection molded plastic that keeps all the pressure out,

and then inside we've got a Raspberry Pi, and that's what's doing most of the computing and message and marshalling for the system. A handful of I2C sensors, accelerometers, that's very similar to the quadcopters. Also lithium-ion batteries, again, under that 100-watt-hour limit. Perhaps some of the really unique things, I think, are that we take the brushless motors, and they're actually immersed in saltwater. And this was one of the really brilliant things. What? Yeah. immersed and and in salt water and this was one of the really brilliant things what yeah one of the really brilliant things that i think open rv figured out early on was that you know instead of

trying to spend all of this time and energy and how do you keep the salt water out of the motor it's like actually if if the enamel coating on the wires is good um you can put them in the salt water and they'll run just fine and so that was like you know mind-breaking all of a sudden you know you can take these little motors and just expose them to the salt water and they'll run just fine. And so that was like, you know, mind-breaking. All of a sudden, you know, you can take these little motors and just expose them to the water. And then you just have to worry about a little electrical pass-through, you know, across your pressure housing. And that's much easier. Yes.

A couple of wires is so much easier. Yeah, yeah. A couple of wires that don't move. Right. You don't need fancy shaft seals that have to deal with pressure differentials across them and all sorts of stuff. Yeah. But unlike a drone that you fly, the Trident is cabled.

Correct. But it's still first person view, right? I mean, I could wear a headset and be the Trident. Yes. Be a fish. Yeah. So there's a high quality 1080p camera in the front and it's's tethered because uh rf is is very quickly attenuated um in water it's frequency dependent but effectively you can you can say that you can't pass rf uh through water you get into really low frequency uh you know that's the game that the

submarines play um but but we can't do that that's a few bits per second anyway yeah exactly if that uh-huh um and uh so the tether um the batteries are all on the vehicle and and we use um the home plug av protocol which is um perhaps more colloquially known as ethernet over power and so these are little modules that you could plug into your uh the plugs in your house and it takes a a standard ethernet signal and modulates that over, over two wires. So we have a, we have a single copper pair coming up from the ROV. And those tethers are either 25 or a hundred meters long. And, and we max out the, the bandwidth on the Raspberry Pi B. That's the bottleneck. Actually, we could push more over the tether if we needed to. and so the hundred meters you

mentioned it goes down to a hundred meters is this where the 100 meter limitation comes in um we've uh officially the rovs are good to 100 meters um and that's how long our tethers are so that's a convenient way to uh keep them from going deeper um but the rovs have gone deeper um with with special tethers um but you know we can't they're not warrantied past that but we have taken them down uh to failure and they they fail uh not insignificantly deeper than uh well i guess yeah well it's pretty significantly deeper than 100 meters. So we've got plenty of buffer there. And it's one atmosphere per every 10 meters. Yep.

So if we went to space, we would go from having one atmosphere to zero atmospheres. But if we go underwater 100 meters, we're going from one atmosphere to 10 atmospheres. Yep. Is this just a gasketing problem or is there more to it? So the gasketing, typically in underwater stuff, we use O-rings, which are distinct from gaskets. We don't get any of the advantageous geometry that you would get from a cylindrical pressure housing. You think about what a home scale propane tank looks like, for example. It's a cylinder with curved ends, and that's because that reduces stresses that occur at all these very critical points.

Ours is kind of funny-shaped. As a result, if you were to look at the inside of the Trident, the injection-molded piece actually has all this very complex latticing that the engineers did a tremendous amount of fea work on to basically make this part withstand you know 10 atmospheres which ends up being approximately 150 pounds per square inch at 100 meters and and one of the interesting things is that we actually use, there's a big motherboard inside Trident, and we use that motherboard, that piece of fiberglass,

FR4, as a structural component. So these lattices are coming down and pushing on the circuit board. We clear components away from where it lands down. But that PC board is actually in pretty significant compression to to help hold everything up what was the reason to go that way instead of cylindrical um we couldn't get the nice form factor uh that we wanted um one of the motivators behind trident was that it wanted to be this kind of nice transecting vehicle almost almost like flying that first person view you were talking about um Um, and so it's, it's actually

fairly low and sleek, um, has a very small frontal area, which is good for drag characteristics. Um, makes it so you can go fast. Um, yeah. How fast can you go? Uh, we can do about two meters a second, which is, uh, like Olympic swimmer, Michael Phelps speed. Yeah, it's actually pretty hard to control when it's going that fast. So I actually like to pilot it on the lowest speed setting because that's when you can get these really gorgeous slewing videos and movement. Otherwise, it's pretty jerky. You mentioned finite element analysis. Uh-huh.

What kind of tools do you use to do that um i believe i don't know if they're using ansys or just the built-in uh solidworks modules um all that design work happened before my time so i'm not quite sure but one of the two just that always it was always such magic and now it's like commonplace and amazing uh Okay, so what sensors are in the bot? You mentioned camera. So we have camera. What else do we have? We've got a temperature and pressure sensor.

So that gives you depth and water temperature. Doesn't the pressure sensor require you to have a hole? The pressure sensor actually lives on the outside of the vehicle. It's kind of buried up in the plastic and then again it's just a small electrical pass-through um into our across the bulkhead um and then we've got uh our three well nine doff but you know we get uh three axis um compass gyro excuse me compass orientation out of it um so on the heads-up display, we display tilt and yaw. We don't display roll, but it's a nine-axis gyro. It's doing fusion on board.

So we just take the quaternions out. Can I ask which one? It's a Bosch 085. Oh, good choice. 055. Yeah, yeah. That's a good choice. Oh, yeah choice. 055. Yeah, yeah. That's a good choice. Don't.

Oh, yeah, sorry. No, we don't like the, it's fine to say with the Bosch one. It's the same one we've used on the other ROVs. But yeah, we've had a really hard time with that IMU. We're not very happy with it. Has anybody had a good time with any IMU? I'm getting the impression that they're just very difficult to work with. And it's not because the math is hard. good time with any imu i'm getting the impression that they're just very difficult to work with and

it's not because the math is hard it's just that they don't do a great job yeah documenting stuff yeah yeah see i'm using the inventsense competitor to that one yeah the 9250 or one of the the 90 no 20948 oh that's one of the new ones yeah i've been looking at that one actually yeah it's a pain in the ass. Okay. Yeah, you have to actually load the Fusion system externally. And I was trying to think to myself, why the heck did they do that? So they could change the code.

But also, there doesn't seem to be any documentation for that code that you load. And so it's like, get the quaternion. You're like, okay, what does this accuracy flag mean? Yeah. And it's nowhere. Yeah. Do they actually give you the fusion code or do they just give you a hex blob that gets loaded in? They give you a hex blob.

Okay. Must not change the hex blob. Right. Are we keeping this part? Oh, yeah. Oh, yeah. Okay. Then I should stop saying mean things. You know. I do want them to help me someday.

Yeah. Okay. So it has an IMU pressure sensor, temperature, camera, anything else? Some bright forward-facing LEDs so that you can illuminate in the dark. And yeah, that's about it. Do you know lasers? Sorry. Oh, well, I mean, the MBARI, the local Monterey Bay Area Research Institute, has lasers on there so that they're always 10 inches apart where the lasers are, and they can measure things that way.

Those are measuring lasers. Yeah, scaling lasers, we typically call them. Scaling lasers, thank you. Yep. You wanted... Yeah, the ones like the sharks have. Oh, like the sharks. The lasers like the sharks have.

Yeah. All right, okay. So you can scare the fish. Yeah, no, so the 2.8 kit has scaling lasers on it, and that's definitely something that people can put on the trident if they want um we've got uh a uh a pattern of um threaded inserts on the bottom of the vehicle so anybody can uh screw on and attach payloads um if they want and do those have power connections as well or okay no power connection you can't add something that runs through the bulkhead right

right um but uh there's a fair amount of um you know capability that's plumbed in there for No power connection. You can't add something that runs through the bulkhead. Right, right. But there's a fair amount of capability that's plumbed in there for hackers that could do some fun stuff. Have you seen anything particular? So there's some folks in the forum who are plumbing out the, so we use DDS as the internal messaging and marshalling system. and so uh some folks may have heard of that what is that um uh ross uh maybe a familiar analog um dds operating system correct yes um dds i think was uh i'm not sure of its uh provenance or creation i think it's used a lot in uh nasa as well as um military and defense applications but it's it's a similar thing it's it's a messaging and marshalling system um it's you can fine-tune a lot more in terms of quality of service you can

prioritize certain messages or keep messages in a queue that then get delivered later on um but anyway so that's that's the underlying... Are you using ROS2? No. But ROS2, the ROS2 messaging system is built on top of DDS. Yeah, that's what I noticed. I'm waiting to find out if anybody is using ROS2. I'm excited to get in there.

I've kind of been waiting. I really want the introspection tools to come online before I kind of make that dive. So that's, that's what I'm excited for. Yeah. Wait, he was,

he was talking about things that people have done. Oh, sorry. I'm not going to, don't, don't, don't divert into Ross. Nobody,

but you care. Okay. No, not true. uh, so we've, I've seen some folks, um,

playing with piping out, um, the quaternions, uh, from the IMU, which are published on the messaging system. And we have hooks in there. On our

GitLab page, if you just go to gitlab forward slash open ROV, there's some sample code for a native app that'll run on the vehicle. This would be the equivalent of a ROS node for those familiar with Ross parlance. And there's a Wi-Fi. We don't use the Wi-Fi module inside the Raspberry

Pi all the time. And so the idea was that people could bolt on payloads to the bottom of the ROV and then use that Wi-fi and it turns out going you know uh back on my rf doesn't transmit through water very well uh just how far does if you've got a little bit of water like maybe a little water interface between your two housings you can you can pass a couple millimeters is okay yeah yeah um but if you really wanted to bolt something on and seal it, that would be even better. And yeah, because it's a Raspberry Pi, it's running Linux. The root password to the vehicle might start with an O and end with an ROV.

But I'll leave it to people to guess what that could be. Other ROV. Yeah. Opposite ROV. Ostrich ROV. Okay. So, payloads. Actually, I heard you speak at a PyLadies event.

And one of the things that kind of just, I didn't understand before your presentation was buoyancy. I kept thinking, okay, so when you add a payload to a flying drone, your battery goes way down, your maneuverability goes way down. It all just, I mean, it's such a cool idea to have taco copters, but it's not efficient. It's fine. But with the open ROV... Nobody wants a soggy taco. No. And really, as you fly through the air, what is hitting the taco? Air. Hopefully not bugs or birds.

So tell me about how buoyancy is important here. Yeah. Well, so, I mean, in theory you couldn't get away with just putting something that's very heavy and negatively buoyant or, uh, very light and positively buoyant on the vehicle, but then you're going to be fighting that, uh, natural tendency for the vehicle to rise or to sink in the water. Um, so to, to keep your, your batteries happy and not drain the system, you want to have something that's neutrally buoyant. So if you were to add a payload that is negatively buoyant and heavy, maybe underwater it weighs one pound, then you'd need to add some equivalent amount of buoyancy to the vehicle.

Which is just making a bigger plastic housing so you could put a bit of air in there. Yeah, or attaching external foam. But you're just making a bigger plastic housing so you could put a bit of psi of pressure um and then that's less dense than water so if you attach that to your vehicle um you're you're effectively adding uh flotation to it but that compression is important i we've been to the ambari open house where they have the little styrofoam cups that you decorate and then they take them to the bottom of the trench and then they come back and they're like little tiny teacups yeah so how do you i mean that seems like a natural property of foam that it compresses yeah yeah and so the this use of the word foam may be a little uh liberal but um there's uh syntactic foams out

there um you know some of these ones that are very good at grammar imagine foam like basically take an epoxy resin and then mix in a bunch of microscopic uh glass balls that are hollow and so those glass balls that are hollow are naturally buoyant um and when you um this is basically what makes composites strong is that as you take a material and you get smaller and smaller pieces of it you're reducing the likelihood that you have a defect in a grain boundary or some other property that is usually where failures begin in these in these materials so if you make them really small then they on average tend to be close to perfect, whatever that means. And then you can encapsulate them in epoxy. And overall, the structure is incredibly strong.

You can machine it on a mill or a lathe, which is great, but you need good respiration. And then you can even do things like paint over them with sealing paints or additional fiberglass. So they're actually quite hard. There's so much here. I mean, we've touched on math and Ross and foam. And how do you, it seems too big.

How do you even approach this? Yeah, it's hard. How did you approach this? How did you get into this? Ah, yeah, it's hard. Um, how did you approach this? How did you, how did you get into this? Yeah. Uh, so I got into it from, uh, a friend who I met at the ham radio club, uh, in undergrad. And, um, he called me up after I was, uh, uh, done with my mechanical engineering degree and, and said, Hey, hey, have you had your wisdom teeth pulled out? And I said, uh... What a way to start a conversation. Excuse me? I said, yeah, have you had your wisdom teeth pulled out? And I said, uh, yeah. And he

goes, oh, great. Well, do you want to go to Antarctica in November? And I was like, uh, let me think about that for a half second. Yes. That was the only major criteria. Well, so that, you know, that was the introduction. And then I actually, you know, met with a benthic ecologist. So she studies the critters that live on the seafloor. And the interview questions were all about how you deal with stress and team dynamics and this, that and the other. And I kept waiting. Well, when is she going to ask some technical questions? And then they never came. And she's like, OK, well, you know, you've got the job if you want it. I was kind of dumbfounded, Like, you don't even want

to know if I know like what an I2C bus is or something. And then after my first season down on the ice, when you're, you know, living and working with the same people for three months, I was like, oh, I get it. Like, it would be, you know, having not the right skill set is by far and away better than somebody who you just can't work with. And three months is a long time when you have to live and work with them six days a week, and it's go, go, go, go. Okay, so are you living on a boat? Are you living in a tent in Antarctica?

An ice cave, fortress of solitude. Yeah. So what's it like working in Antarctica? So the first season we were based out of McMurdo. And it's a summer population somewhere between 800 and 1,000 people. It's the largest U.S. research, actually largest research station on the continent down there. And it's like I kind of describe it as a small mining town. You have doctors.

There's a small hospital, you know, there are electricians and, you know, everything it takes to run a small town. Everybody's down there and it's dorm style housing. And then there's a big galley. So the first year we were living in town and then commuting out to our field sites on snow machines each day. And we would pull sleds that had our RVs and instruments. year we were living in town and then commuting out to our field sites on snow machines each day. And we would pull sleds that had our RVs and instruments. So we would go out in the morning, do our work, and then come back in. The following season, after the scientists looked at some of the initial data, they seemed to indicate that there was a strong diel signal in these animals. And that means that they not not surprisingly have a difference in how they behave whether it's night or day even though the sun is up 24 hours a day

that time of year it gets lower in the evenings so you end up with less light making it down into the water um and so this is like jellyfish come up at when there's a full moon at night and they feed at night high up, but then they go down during the day because they don't want to be eaten by birds. Right. Okay. And so this is with krill and silverfish. And so we were looking at critters at the bottom of the food web. And so that season we actually ended up setting up an ice camp out in the middle of the sea

ice. So this is ice that freezes, um, each year during the winter time. And it's, uh, on average, like about six feet thick. Um, so it's, it's quite strong. Um, and we had individual mountain tents set up out there and then, um, a food tent, storage tent, and, uh, like a communal eating tent. Um, and so we would be out there for six days at a time and then go into town which is like an hour away on snow machine it was about that far of a commute um and then you know would do laundry and get a hot uh brunch there's brunch served on sundays which is always a real good treat um so

mcmurdo station it's where you go for brunch yeah when you go for anything probably. Okay. You're camping on an ice block. It's summer. It's summer. Right. So, so doesn't that sound like a bad, even a worse idea than camping on an ice block during winter?

It's a lot of ice. All right. So were there storms and stuff or is it pretty calm during the summer? Generally it was pretty calm. We had, we, we put in our camp the, the last year and then within a few days had a big storm, you know, and we had the real bad storms come out of the south coming off of the Antarctic Plateau. And so we had basically built our camp so that it would be more robust against a storm coming out of the south.

And then this massive storm just comes out of the east and, you know, puts all of this snow on top of us um which is kind of bizarre there's not typically a bunch of snow out there um and i think that's was due in large to the wind picking it up and transporting it rather than falling out of the sky um but yeah for the next week um you know part of field work was having breakfast in the morning and getting up and then digging out a portion of the camp for an hour and a half and then going out and doing the field work and then coming back and repeating that until the place was dug out. That sounds super fun. What do you mean by field work?

Okay, so this wasn't the backpack-sized ROV that we have been talking about, the Trident. This was bigger and more and probably a little more effort. Yeah. So this was an ROV called Skinny, submersible, capable of under ice imaging and navigation. And it's about four feet long, torpedo shaped, weighs about 35 pounds. And we can deploy it through its largest OD outer diameter was eight inches. So you'd have to drill a hole in the ice in order to get it down there and that's how big you'd have to drill the hole yeah and so there's um how do you get it out yeah that was my question tethers six yeah but you have to align it to the hole so we just we pitch the vehicle down and then thrust down so

that we you know basically line it straight up and then the tether manager who's up at the surface gently guides it up and sometimes you know you'll catch the bottom fairing on the ice once or twice and you're just gentle until you guide it into the hole and then out she comes okay so so now you've dug out your your snow and you've drilled a large hole in the ice did you have to do that every day or did you do use same one most days? Yeah, no, we did that every day. And the holes were made in the ice using a Jiffy drill, which if you've ever used a gas-powered auger to dig fence post holes or something, it's basically a lawnmower engine mounted on handles. And then we put these large- Right, because you're drilling six feet. Yeah.

And an eight-inch hole is not small. it's actually a tent the drill bit itself is 10 inches um sure and uh so we had this you know gas powered drill and that would just was part of our field kit um and so we would uh we would actually have to drill a couple of holes at each field site one where the instrument would get deployed through and our instrument was um we were actually using skinny as a tow vehicle to pull a larger sonar instrument that had an active essentially an expensive scientific grade fish finder and a fluorometer that was measuring the amount of algae in the water and and so we were running transects with this but we would drill a hole to deploy that. One for the ultra-short baseline navigation head,

which is an acoustic navigation system that we would lower down through the ice. And then another one for taking water samples. So it was typically three holes per site. On a good day, we could knock out four field sites, and they were all separated, so it meant some commute on the snow machines. So we would pack everything back up, drag it to the next field site. So these were like 20 hour days.

Not quite that long. You know, we did have some that were long, especially when stuff broke down, you know, then the pressure was on. Like, you know, I don't even want to think about what the, you know, the hourly expense for having, you know, a person down at McMurdo when we're supposed to be doing science and the vehicles, you know, something is shorted you know a person down at mcmurdo when we're supposed to be doing science and the vehicles you know something is shorted out and the engineers

are like oh we're trying to fix it and the scientists are like when's it going to be ready and we're like oh we're working well and you you don't want to lose it so it's important that you fix it properly yeah no shortcuts or at least shortcuts with extra belt and suspenders attached. The underwater navigation. Is it just like sonar? I mean, is it just chirping and everybody takes times? Do you need a fine-grained clock to do that? Yeah, so underwater navigation is a whole subject of research in and of itself. Yeah. I hear somebody was thinking about getting a PhD in that. Yeah.

So, I mean, I don't know how much we want to do it like a deep dive, but essentially we have... Is that a joke? I mean, is it like your life full of puns? I didn't even think about that one. But yeah, I mean, so I kind of think about the navigation space as on the one side, you have a whole suite of sensors that you have that are available to you. I guess I should preface this with underwater, you know, is a GPS denied environment. So we don't have any external source of position when we're underwater naturally. And that's so weird. You know, like 20 years ago as humans, we were like, maps, maps are fantastic. We're going to get from here to there. The only way to know is to go

by a map. And then we got GPS and we're like, I'm just going to shake this until it works. And it's going to tell me where to go without ever thinking this goes to space and comes back down and has this weird calculation of multiple things in space and now you're underwater you don't even you don't even get this basic human right of gps well yeah well i mean fundamentally the way the way uh an external position correction underwater uh works which is the same thing that um well gps can provide velocity but let's just talk about position for a moment is that your your gps receiver is is measuring ranges to a whole bunch of different satellites

that are moving around the earth simultaneously and then it uses all those different ranges with a known position of where that satellite is to back out or estimate where you think you are. And in the underwater world, we do the same thing but using acoustics. So an ultra-short baseline system. The baseline refers to how far apart the receiving elements are on your system. So it's essentially this sonar head, and it has a whole bunch of piezo transceivers packed into the head of it. And in most USB-L systems, it'll work by, it emits a ping of sound, and that goes out and it hits the vehicle. The vehicle has a corresponding transponder on it. It hears that ping, and then it replies back with a chirp.

And so if you know that round clock time and you know the velocity of sound through water, you know what that range is. And the USBL goes even further. And by having multiple piezo elements packed into the head, you can do uh beam forming or um phase delay uh estimation to actually get an azimuth and elevation estimate of where that signal came from so then you've got range so you end up with a ball of piezos it's not all in one plane in order to get elevation you're going to need uh at least two planes yeah anybody who Anybody who listened to the ShotSpotter episode, yeah, it's the same thing. But acoustics through water, the speed of sound through water depends on temperature.

Yeah. And fish. More broadly, density. And so the density of the water is a function. Yeah, is a function of temperature and salt. And it turns out when you go really deep, water is actually not quite incompressible. That assumption begins to break down. Boy, is that a weird environment. sound velocity as a function of depth. And it's this kind of, depending on what the characteristics

are of the water, it can be this kind of convoluted shape. And as a result, you end up with the sound waves taking not a direct line through the water. They'll actually bend and refract and change. So they don't travel in a straight line as you're moving through these layers of water. You know, you could almost think of it as a finite model. Each five centimeter section of water has a slightly different velocity. Like a yogurt parfait. Yeah, yeah. And just like, you know, we rely on that in optics.

It's the same principle. The light travels at a different velocity through different materials, and then we shape those materials, and, you know that defend defines where we bend effectively the light so the same thing's happening underwater with sound and the same things happen with gps yep that you if you're in a city it it's much worse because you it gets the reflections from the buildings and it's like echoey except in gps uh ranges and so how do you fix that i mean it's more than just knowing it's there it's how do you compensate do you compensate

or do you just accept the error i think it depends um if uh you know my most of my work has been fairly mission driven and so it's uh you know what is an acceptable error for, uh, for the scientists using this system? If it's X, okay, well then that, that first order approximation, let's just call it 1500 meters per second and we'll call it good. Um, and anything else, uh, you know, we just don't worry about. Um, but, uh, you can, you can get really complex and you can do things like, uh like there's something called a bellhop analysis where you actually simulate a water. Do you tip it afterwards? No, but you do a numerical ray tracing analysis of sound through water and then you can put that into your navigation model um i haven't gone to that uh you know i haven't had to do that degree of of engineering and modeling for for these navigation

systems but i've talked to and worked with people who have and they've kind of said eh you know it it'll buy you a little bit but it you know oftentimes it's just not worth it and that first order approximation is good enough and wouldn't it be simpler to just have another station doing the pinging yes yeah because i mean and once you get four you get good location yeah and and so i just talked about um ultra short baseline where you're you're getting that um uh range and azimuth elevation from a single unit um but if you have multiple acoustic uh instruments, perhaps that are spread out over order kilometers on the seafloor, you typically would refer to that as a long baseline system. And then you're measuring ranges against things that have a known fixed location.

And then you can use more traditional TDOA, time difference of arrival methods, or even, you know, just finding the minimum or, you know, linearize the system and then do at least squares on your position. And then that tends to be pretty good. What was the neatest animal you saw under the ice? I mean, did you see any of these giant sea stars or jellyfish or weird things that shouldn't exist on this planet? Yeah. So, um, one of my, uh, colleagues down there, uh, who was a graduate student at Moss landing, um, he was an under ice diver. So he was going down and collecting samples and would put on dry suits. And he showed me a video that he took of a giant jellyfish that was

hanging out near the outfall, which is where the treated water leaves the station. And I couldn't quite get the scale of this jellyfish until he, you know, started the camera looking at the outfall. And he was like, the diameter of that pipe, I don't remember exactly. It was like 12 or 18 inches, right? And then he starts panning up and there's just like multiple pipe diameters like mini pipe diameters until he gets to the bell of the jellyfish and the tentacles were hanging on so the tentacles to this jellyfish were like 30 feet long and he said the the bell of that jellyfish was like six feet wide i was just dumbfounded like a jellyfish bell that's six feet wide. I can't even imagine swimming next to, you know, encountering something like that in the water.

Yeah. Yeah. Were you ever tempted to do an underwater, under ice dive? it but it certainly seems beautiful i mean the pictures that we would um most of the time we were operating the rov down there um in open water and we couldn't see the bottom but closer to some of the edges when we could actually get down and see the benthos holy cow it was phenomenal i mean the i never would have thought that there are so many critters living on the bottom of the ocean in antarctica but there are sea stars and pycnopodia, which are these kind of spider-looking things crawling all over one another in massive sponges. I mean, it looks like a rainforest,

but with underwater critters. It's phenomenal. Where do the nutrients come from? Is it all from the phytoplankton? I'm not the right person to know that. No, no, but that's a good question. I mean, I should know. Would you like me to ask you about ROVs?

No, no, no. That was just my way of saying I don't know. And I'm a little ashamed that I don't know. But so generally nutrient cycling in the ocean, you get upwelling where you get a lot of nutrients that are brought up from the depths. I'm not sure if those nutrients fundamentally come from the depths. I mean, I know there's lots of cycling. I know a lot of the iron in the ocean actually comes from deserts and wind that picks up little pieces of sand and then deposits iron out across the ocean. So the Sahara Desert actually does a tremendous amount for fertilizing the Pacific Ocean because that dust blows over and then lands out there. And that's, you know, oftentimes a limiting nutrient

for things like algae. Yeah, there's this interesting idea that you can dump iron filings into oceans in order to sequester carbon. Boy, am I off topic. Okay, let's see. I have a question from Bailey, and I know the answer to this one, and it is awesome. Have any animals attacked anyone's ROVs and what happens. Yeah. Um, so there's a, uh, there's a video on, on YouTube of an, uh, from an early Trident user. And I think they're, uh, operating down in the Farallon Islands, um, with great white sharks. Um, and the video, uh, starts out with the open, the Trident sitting out in the water and you see a great white shark come up and swim and do what I was told was, you know, an aggressive, you know, get out of here kind of behavior. And then she comes back and then makes another pass. And on the second pass, bam, just, you know,

chomps down on the ROV. And you have this first person view. And so all of a sudden you're literally like looking in the mouth of this great white shark at these teeth. And so she kind of che you're literally like looking in the mouth of this great white shark at these teeth. And so she kind of chews it for a minute and then spits it out because clearly it doesn't taste like anything. And so the,

you know, the, the shell is all scarred, but it, but it survived and they continued diving with the vehicle for the rest of the day. So yeah. Yeah.

And so then you bought it back for advertising. Exactly. This video is amazing. I mean, it starts out third person. You see what happens and you're like, oh, well, they lost their thing. But no, no, you look inside of a shark's mouth. It was kind of scary. Have you had other things like that?

Interesting animal encounters or actually lost units due to uh wildlife no uh i haven't we almost got a unit uh uh our skinny rov stuck out in the ice when we were operating a little too close to the ice edge um and the wind um had rafted and blown a whole bunch of right uh broken up ice back to close to where we were working um and we i took it out into the open water and then the tether got tangled up in this rafted ice that kind of looks like you know rubble from uh building after after an earthquake or something um and so it was like four very tense hours of just trying to untangle this uh you know tether and we're thinking like you know at about hour three we're like well are we gonna have to go get somebody who knows how to dive and

who can like go and untangle this you know um so it's just we're gonna need a bigger hole yeah yeah well that's what we started doing we're like we don't we didn't know quite where it was because we were out along horizontal range and the USBL wasn't quite working. So yeah, it was tense, but we recovered the vehicle and the tether. Let's see. If you could deploy ROVs anywhere, where would you take them and what would you want to look at? I think there's so many cool ecosystems out there. You know, in our own backyard here in the Monterey Bay,

we have these phenomenal kelp forests, which are actually extremely difficult to operate in our area. Yeah, I was about to say. A tether might cause some issues there. Yeah, they get tangled. But the life there is just phenomenal. You know, coral reefs are obvious ones. You know, and what I think would be so cool to be able to do with this is if you can, um, uh, live stream these, uh, experiences over the internet and

I'm envisioning a classroom, uh, that gets shipped like a big Pelican box that has a bunch of VR headsets and the kids can all put these headsets on and the vehicle has a 360 view camera. And so it's like Ms. Frizzle's magic school bus, you know, and you're getting a tour of this kelp forest or the coral reef, you know, down in Australia. So that's, that's kind of more of an experiential thing.

But yeah, I would love, I would also like to kind of embark on the challenge of like how, how cheaply could we make an an rov or an auv that would go to the bottom of the marianas trench i mean folks from wood woods hole um james cameron have have been down to the bottom of the marianas trench but could you do it with ten thousand dollars of hardware i mean engineering time aside like what would it actually you know how could you get down there and how cheap could you do it i I mean, the pressure is, is way more. So you have to, you have to, you have to

deal with the pressure, but what are the other factors? Maybe you don't have to deal with the pressure. So you, you can oil fill electronics and you can have everything be pressure compensated. Yeah. You don't have to put a human in it. So yeah. But then you have to get in, you need, you need to find, you need to be careful with your chip selection um because things like crystals have little air cavities in them um or mems devices have air cavities that um are open because the little elements in there need to vibrate um even some memory devices have little air pockets in them so if all of a sudden that's not usually on the data sheet either yeah no, no. Um, I think, you know, people, people have businesses about doing,

you know, pressure compensated electronics for, for very, uh, specialized needs. Um, so the, the electronics is one thing, but I think, I think you can get around that with, uh, just selecting the right stuff. Um, and then you fill everything with oil and let it go to uh 11 kilometers of pressure um so uh tethers uh if you wanted to have a tethered vehicle that's actually also pretty difficult because that gets really heavy gets really heavy and after uh you know depending on what the tether is made out of a lot of oceanographic um uh vessels have um a standardized i think it's a 0.68 inch uh steel braided tether um that's got some copper and fiber on the inside of it um but i think those uh i haven't done the math but they become non-self-supporting after like 8 000 meters or something

there's just too much weight and they snap um and so then you could um the way uh some folks at woods hole got around this was they had simultaneous um unarmored fiber spools both on the vehicle and on um a little depressor that lived just below the water surface so as the vehicle is descending um you're simultaneously spooling out um an unarmored fiber optic cable, one end from the vehicle and one end from the ship. And you just let the current take that cable wherever. So you've got, you know, easy gigabit comms down to the vehicle. It's not a structural thing.

Um, and then you build in, you know, backup redundant acoustic systems and failure, uh, safe mechanisms and all those sorts of things. Um, but then all of a sudden you basically have a weightless cable that gives you comms um so okay if we can do that on the cheap or maybe maybe there's another way to do it um you know maybe you do just make it autonomous um cameras the airspace uh dealing with air and pressure does get kind of interesting when you're thinking about cameras again because if you're going to go to the bottom of the ocean, I would think you want to see what's down there. I need a camera, maybe 12.

Yeah. Yeah. You know, maybe that little door is down at the bottom. So we've got to find that. Remember, don't take out the plug. Yeah. But, you know, I think you can also play kind of an interesting materials game there. Most of the time we use glass in our optics, which has a certain... I'm not as well versed in this, but Snell's Law is, I think,

what determines how the angle of light changes. And that's a function of, I think, just the density of the material. I don't actually remember what uh there's some electro-optic stuff to the chemical stuff that affects it but yeah index of refraction material science yeah um but i've been told by some people who have thought about this um that if you if you make your lenses out of like sapphire for example then the index of refraction between water and sapphire is roughly equivalent to that of air and glass so all of a sudden now you don't need to maintain an airspace

you know in your camera or your lens or anything like that so then you're then you're kind of in business um you don't need a pressure housing uh which is an expensive part and you still kind of have to figure out the tether comms part but yeah um okay this is from steven and it's related to what we're talking about now what are some of the key uh fundamental technology challenges that are currently limiting progress of rov development and he suggests comms bandwidth navigation positioning mechanical yeah what do you What do you think is the most important? Well, one of the things we haven't talked about is connectors. Underwater connectors are the bane of many underwater engineers' existence,

or at least I spent way too much time dealing with connectors. I've worked with military connectors and i suspect that that's a level of harder that's exponentially harder than the freaking military ones which are so much harder than regular yeah yeah and they're expensive i mean even even the lowest end connectors you're like looking at a hundred bucks a pop and you're like raspberry pie. $35. Connector. Yeah. It's just $100 for the cheapest one. Yeah. Yeah.

So if we can figure out a good way to make, you know, those connectors that can transmit a lot of power and, you know, you end up having to trade off a voltage in current, you know, based on conductor size. Especially when you're going 8,000 meters. Mm-hmm, mm-hmm. So yeah, connectors are a big one. The navigation is also a big one. You know, these navigation systems, if you have hundreds of thousands of dollars to spend, like you can build a pretty phenomenal navigation system. You can get laser ring gyros or fiber optic gyros,

which are actually measuring the rotation of the earth. And combined with knowing where the gravity vector is, you can get an estimate of true north. So that's how those compasses work. But those are like $150,000, you know, compasses. Well, I mean, you can get $5,000 ones, but they're not that much better than MEMS. Yes, correct. They don't have air? Oh, boy. MEMS gyros and everything.

Like, you're not, I don't think you can, you're not going to have a north-seeking, a true north gyro compass out of a MEMS device. I think that the noise floor is just too high. So, yeah, navigation, also tough one. Yeah, we kind of, like, figured out the motor things. Like, you can actually put brushless motors as long as you've got good enamel coating um as long as you wash them off after you get them out of the salt water uh you know yes they will certainly last longer if you do that um we've done a fair amount of testing with not rinsing the motors because we you know do these kind of rapid life cycle um testing on on the on the

motors and it's not called being lazy at all um and they'll they'll still do quite well uh the the abrasive properties you know if you set the rov down in a really silty environment and especially a silty environment that has lots of ferrous material because these are permanent magnet brushless motors all of a sudden you start accumulating the the black fuzz if you've ever dragged a magnet through play sand that starts accumulating in the motor and then that abrasion is usually what kills you before the salt water does let's see what other questions that i get from listeners uh spec wanted to know before going to antarctica what did you expect to miss the most and once you were there what did you actually miss the most oh that's good uh it wasn't sunlight because it was

summer yeah um i was expecting to mostly mish miss you know coming from california like lots of fresh uh vegetables all the time um and at the beginning of the season when there's lots of big cargo planes coming in um we actually have a pretty good supply of what we call freshies. Um, and those tend to taper off. Um, but you know, then it's okay. The thing I ended up missing the most though was, uh, was sleep. Uh, I'm definitely like an eight to nine hours a night kind of guy. And, um, when you're down doing field work, um, that just doesn't happen. And so, you know, I kind of get progressively more and more underslept as the season goes on. So that's a hard one for me. But you went back for three seasons. Yeah. Yeah. It seems like a lot. What

made you stop going back? The NSF grant ended, you know, and then it was like, what should I do now? How about grad school? What were you doing with the other months of the year while you were doing that? So I did a little bit of contract work for Open ROV. I worked as an intern at the Monterey Bay Aquarium Research Institute at one point. We had work to do in the off-season, making repairs and improvements to the vehicles themselves. And then a few other small contract things on underwater platforms. What does it take to keep the robots working in Antarctica? Is it different than the problems you're seeing with the Trident,

just making it work underwater? Yeah, so the vehicles we had, the skinny vehicles that we had down in Antarctica, were a pretty complete prototype vehicle. For it to be what I would consider a production vehicle, we would have needed another spin on it. And mostly we ended up dealing with, so there was not, a good example is we didn't have very good strain relief on a handful of these underwater connectors. There was just a little bit of residual strain in there. Thousand dollar connectors and they couldn't build in some strain relief.

Yeah. Yeah. And so, you know, every, probably on average, like three or four weeks, one of these connectors would fail. Just a little bit of water would start getting in and the power bus on skinny was a 300 volt DC power bus. And a little bit of water would start getting in and, and the power bus on skinny was a 300 volt DC power bus. Um, and a little bit of salt water, uh, can go a long ways with 300 volts. And so all of a sudden you would end up, there would be arcing underwater. And, uh, usually the symptom would just be that the vehicle would go dark, um, because it would short everything out. Um, and you know, at one point, uh, we actually cooked a, a, it shorted out and then some of that 300 volts made its way onto the know digging around looking in the inside of these circuit boards that are all kind of sandwiched together and and see a what looked like a lightning crack you know through the middle of the

the eight pin dip and i was like oh i don't think that's supposed to be like that you know and so that it was became a quest for like digging around for you know i don't remember what chip it was specifically but i don't you know find a spare for that okay and solder it back in and hey we're back in business you know so you had to do the hardware and soldering uh-huh how do you how do you solder in a tent in antarctica uh with a lot of patience and you know some thick skin like it's especially if there's a storm outside and it's it's blowing um but we had so in our field camp out on the ice um we had a small solar array with lead acid batteries um and if we really needed to we had some small uh gas power generators

if it had been cloudy for a couple of days and the batteries weren't up to snuff but um skinny itself uh was powered by a small portable kit uh honda one kilowatt generator that we would then put through a standard uh apc computer battery backup to clean the the power up a little bit um and then we would up convert to 240 volts pass that down the tether um so that we're not pushing a whole bunch of current over a 300 meter tether. So boost the voltage up, send it down, and then take it down to lower voltages on the vehicle, which is actually very common in ROVs. A lot of the professional ship-to-plate ROVs have like 4,000 volt DC systems going down the tether. I mean, that totally makes sense because then you have the high voltage,

you can have the super low current. But then when you talk about things like saltwater, it does seem like the compatibility, the trade-off there is, I don't know. I'm not sure about that. Are you sure? I mean, a lot of people who are smarter than me, I think have also converged on this solution. So I'll go with it. Okay. I wanted to ask you about methane seeps because you mentioned

that that was a hobby and I've never, I mean, I have some strange hobbies, but methane seeps was never one of them. What do you mean by that? Yeah. So methane is a really potent greenhouse gas. Um, it decomposes naturally in the atmosphere. It has a half-life between like eight and 12 years. And so it, um, methane, which is CH4, uh, decomposes into, uh, carbon dioxide and water. Um, but before it does that, um, it traps a lot more heat, um, than carbon dioxide. So depending on the timescale that you're talking about, a lot of folks have kind of standardized over a 100-year equivalent, but a ton of methane is roughly equivalent to 25 tons of CO2 over a 100-year time period.

So it's a potent greenhouse gas. And people have been thinking and talking about this uh in relation to cows and their methane emissions and i've heard it rice patties as well as um coal mines old oil and gas infrastructure um so those are kind of the primary sources um and a good friend of mine who works in the climate space um you know started thinking well what are we going to do about the arctic people are talking about these positive feed lap feedback loops um that uh occur when you have for example melting permafrost and then more co2 and methane gets emitted uh through the ground as a

result and then that induces more warming and more well melting of the permafrost. And it turns out that there are some relatively large point source releases of methane throughout the world. And large as in like, there's a lake where we're collaborating with some folks from University of Alaska Fairbanks. And it's in some parts of this lake, kind of like a jacuzzi where there's bubbles bubbling out from the bottom of the lake, except it's all natural gas. And it's, you know, it's a lot of methane. So then the question is, well, can we do it? Like solving the problem of plugging up cow farts is pretty hard because there's many cows and they make, on average, a little bit per cow.

So that's a very hard thing. But if you have large single point sources, that's a more tractable problem if your goal is to reduce overall emissions. So I'm working with a group of folks and we're working on a device to mitigate those emissions. I remember driving through Montana many years ago. They had basically lit some of the methane seeps on fire to partially offset. Was it offsetting or they were just burning off the fields? I thought it was partially to offset the emissions of the greenhouse gases. Yeah, so that's actually done at landfills.

Okay. When they cap them, with the decomposition of the organic material, you will generate methane. And some landfills will burn that methane. And it's, you know, as I mentioned earlier, it degrades into CO2 in the atmosphere. Which is better than methane. Yeah. So if you can just accelerate that transition from methane that's already going to get released into the atmosphere, it's better if you can just shorten that transition time. And then there are, you know. And there's a better chance that the CO2 will fall immediately out.

Yes. Yeah. I mean, when you combust it, in theory, if you have perfect combustion, you end up with carbon dioxide and water. I was thinking of the stuff they do in natural gas fields where there's burning off that excess. Yeah. Which is not for environmental reasons at all. It's just because they don't know what to do with it. Yeah. Yeah. I mean, they're drilling like an oil well, for example, but there's a little bit of gas in there and they need to do something with it.

They don't want to just release it. and you don't want it to build up correct yeah yeah okay uh i should go back to the rov the open rov because that's technically why you came you guys are selling these but they're kind of expensive yeah how much are they uh i think they're retailed for 17001,700 on openrov.com. I was able to get a discount coupon code. So if anybody is interested, if you use the code word embedded, and I think we'll drop a link in it in the show notes. But that'll get you off $200 in the store. So that should show up at checkout time.

But, you know, on the grand, like, you didn't used to be able to get an ROV for 1700 bucks. You know, it used to be that the lowest class was like a hundred grand and then people started making them for 30 grand. And now it's, you know, like same order as, you know, a DJI drown kind of thing. Yeah. That's, that's a good comparison. Um, and do people, do people send you videos or are there places where I can look and see what people are doing with them? Yeah. Um, so there's, uh, an awesome initiative, um, that, uh, we have going on in collaboration with National Geographic and the Packard Foundation, the Schmidt, uh, Schmidt Ocean Institute, um, called the Sea Initiative.

And these are, we got a grant that allows us to give ROVs out to citizen scientists, explorers, people who are just doing really interesting, engaging work. And so if you do a search for Sea Initiative, you can see all these expeditions that people are going on with the ROVs. There's folks working on turtle monitoring. There's folks here in the Monterey Bay. Some people working in the Monterey Bay marine protected areas and using these ROVs as monitoring tools. And it's a lot of really awesome stories. Yeah.

And I'll point out since I searched for the wrong one, it's S-E-E. Correct. Not S-E-A, so C as in visual C initiative. Yeah. As though you were looking through a camera at some amazing animal. Yeah, science engineering exploration initiative, I think. I'll have a link to that. Yeah.

Science exploration education. Yes, thank you. It helps to have the website in front of me. Yeah. My Googling skills are second to just about everybody's. What else should I ask you about? I mean, you have a pretty broad resume and I'm like, let's go back to navigation. Let's talk about acoustic sensors.

Let's talk about acoustic modems. Let's talk about Antarctica. Just what do you want to talk about acoustic sensors let's talk about acoustic modems let's talk about antarctica just what do you want to talk about um i don't know i mean i feel like it's uh it's always fun to talk about like dream projects or the you know the things that you would want to work on if you you know were given a chunk of free time and money for prototyping and that sort of stuff i've always been interested in trying to do low-cost acoustics. It's a space that I know very little about. And so I'm sure there's all sorts of gotchas in there

about what makes it really hard. But I look at how cheap consumer audio equipment is. And it's like, okay, so we have, you know, pretty good, uh, A to Ds and D to As that, you know, are good to like 440, uh, kilohertz. So you can, you can do anything in the acoustics range, you know, from 20 kilohertz and below. Okay. Uh, you know, what, what could be done using consumer grade stuff, um, instead of having to, to go really, really high up. Is this for exploration? For location? Yeah, I guess both for, first for location, you know, some of the other navigation instruments

that I didn't talk about are, one of them is called a Doppler velocity log. And this is an instrument that uses acoustic Doppler shift to measure three-dimensional velocity. So it sends out pings. And you can imagine, you know, when the ambulance is driving towards you, the pitch of its siren is higher than when it goes past you. And that's due to Doppler shift. And we can use that same principle underwater to measure velocity of a vehicle relative to the ground. Or you can also use the same thing to measure water velocity. But the sound in essence reflects off of little things in the water or the sea bottom. And so if you have a good velocity measurement,

that goes a long way in helping you out with your navigation system. Because then you're not just relying on acceleration. Acceleration's a terrible measurement. Yeah. I mean, because we have 1G of acceleration on us at all times and therefore anything else is tiny compared to that. Yeah, yeah. So having that acoustic velocity measurement would be awesome. And also, you know, it goes a long way if you're going to do an autonomous or untethered vehicle, having that acoustic back channel to the vehicle so that you can actually command it to come home or, you know, send a little bit of data back periodically.

This is the acoustic modem style thing. Have you used acoustic modems much? A little bit, yeah. I've used some, let's see, a modem from Tritech. They're a company based in the UK. And then I think that's actually the only one I've touched technically. I'm looking at one that is 600 baud. And I'm just like, I don't, that's like, I can speak 600 baud. Yeah. I feel like I could chirp to it like R2-D2.

Uh-huh. It's just so weirdly slow. I have my serial port turned up to one megabit per second. Yeah. How do you live this way? You get very diligent about bite packing. What is the data that you actually want to send to the vehicle and what is it that you need back? And what can you, like, what if, you know, so there's in the underwater world, you have not only the problem of a very low baud rate, but you have high latency right if your vehicle is 1.5 kilometers away

that message is going to take a second to get to you so you can't do really timing critical stuff over that much latency oh and by the way those sound waves don't travel in a direct line and they might bounce off of the underside of the ice and you might not actually ever get that packet. I have noticed it does seem to be like talking into a tin can through a wet noodle to the other side. That's a good analogy. I like that. It's not exactly a precision instrument there. Yeah. But I mean, there has, I mean, my sense is that there is a tremendous amount of digital signal processing that has gone into these systems.

And you do have error correction when they packetize this data. So you do have some assurances there, and you can check your checksum and do that kind of stuff. Okay, what else would be on your, just give me a genius grant. I'll do what I want to do. I think another kind of selfish program is I would like to... I've always thought it would be kind of interesting to roll a GPS from scratch. Like from... Sounds a little perverse.

I was at a company that did that. Just wrong. But they wanted to ship things. Don't you need some rockets first I think he just wants to do the ephemeris calculation and all of that

oh okay yeah okay I suggest doing it in postgres or SQL because that will make a really good

conference talk okay that was not a helpful suggestion yeah but that it just seemed like I kind of I tend to think about, you know, I'm also one of these people who starts a lot of projects

and doesn't finish most of them, but most of them are like a, it's a learning exploration. It's a way for me to dive deep on something kind of particular that I'm interested in. And then once I've extracted that nugget, then I'm like, okay, I'm ready to move on. I've learned what I want to there. Oh, and I could see GPS.

That makes sense because it is so critical to navigation. And they have made so many amazing things possible. What's hidden in that code that you just don't think about without doing it yourself? Yeah, yeah. For all that, I don't think that's a good idea. For me, for you, it may be awesome. Yeah. No, I mean, it sounds hard. And maybe it is just like just like you know maybe if i just did the math part of it i would

feel fulfilled um and maybe somebody will let you read their gps card yeah yeah all right i think we have kept you long enough since this is one of the first sunny weekends in a long, long time. Yeah, it's almost not cold for Christopher. I don't know. Let me look. I don't have that up. It's probably on the border. Yeah, it may be 61F. He's still got a sweatshirt on.

All right. Do you have any advice for people who want to follow a career path like yours? I would say, you know, especially if you're doing field robotics and field work, patience is a really key thing to develop. You know, when something breaks, and it will, you know, even in the most stressful environment,

you know, it's pretty key to keep a level head and, like, be able to put your head down and keep moving forward. But I guess also, you know, know when to walk away, take keep a level head and like be able to put your head down and keep moving forward. But also, I guess also, you know, know when to walk away, take a little break and come back and then get back to attacking it. So that and yeah, just be really curious, you know. Don't hesitate to take a little bit of time and go on those, you know, kind of deep dives, something that you're interested in. Because you never know when that's going to come back and be useful. Oftentimes it is. All right. I think I may have preempted my last question, but

before we get there, I will remind people the code embedded for $200 off at the Trident store. If you are getting your own ROV, please let me know and send me all your videos. Or let us borrow it and we can go check out the inside of the boat and see if there's really a giant octopus living there. Yeah. Did you bring one? Because I really want to go down to that concrete ship and see what's living inside. I'll bring one once the dust has settled a little bit at the office.

Yeah. All right. Lachlan, are there any final thoughts you'd like to leave us with? Oh, no. Thank you two just so much for having me on. This has been really fun. Our guest has been Lachlan Barker, systems engineer at OpenROV.

You can find them at OpenROV.com. Thank you so much for being with us. Thank you. Thanks, Lachlan. Thank you also to Kathleen Toot of PyLady Santa Cruz for introducing me to Lachlan. Thank you also to Christopher for producing and co-hosting. And of course, thank you for listening. You can always contact us at

show at embedded.fm or hit the contact link on embedded.fm. And now a quote to leave you with. Ah, yes. From Helen Scales. She wrote Eye of the Shoal, which I believe Christopher named the Fish Facts book. Before 1815, when Humphrey Davy invented his safety lamp, British coal miners sometimes went to work carrying a bucket of dead fish. Naked flames had the dangerous tendency of blowing up any methane that seeped into the tunnels, so miners needed alternative lighting sources. A bucket full of putrefying fish could apparently produce enough dim cold light for miners to see by. I hope you enjoyed that fact. I'm not sure I did. Embedded is an independently produced radio show that focuses

on the many aspects of engineering. It is a production of Logical Elegance, an embedded software consulting company in California. If there are advertisements in the show, we did not put them there and do not receive money from them. At this time, our sponsors are Logical Elegance and listeners like you.