10,000 Yen into the Sea
Flipper, Nick
The use of a pressure housing in an underwater vehicle can be difficult to implement without becoming a cost-center. Flipper will walk the audience through a new design for an Autonomous Underwater Glider which challenges assumptions about what is required or necessary to deploy sensors, transmitters, and payloads across long distances in the ocean. The speaker assumes no priory knowledge of subject matter & hopes the audience can help him to find new applications for this Open Source Hardware project. Flipper is a hardware hacker obsessed with lowering the cost of underwater robots. Flipper spent 2 years as a member of his College's ROV team practicing waterproofing of CoTs components such as cameras, IMUs, and motors. These experiences inspired him to form the "Mesa College" team that participated in the 2011 & '12 AUVSI Robosub competition. During the first year of competition, the Mesa team took home a judges award for 'Innovation on a Budget'. Since that time Flipper has been employed by an EV manufacturer working to reduce the cost of high efficiency electric vehicles.
 everybody, don't be shy if you want to move up front. There you over there. Anyway, 10,000 yen into the sea. Let's give him a big hand. Say something like, come on. Awesome. Hello. So as he said, I'm flipper. This is my talk, 10,000 yen into the sea. Essentially, I mean, just to start with, can I show a hands who enjoys filling up their gas tank? Yeah, I'm not a big fan of it either. Actually, I spent four years commuting to and from my community college. Four years, two year program. I had other things to do. So it was a 45 minute drive each way. So I pretty much ended up putting about as much money into my tank as I saved by living in my parent's basement. So all the benefits of living in my parent's basement with none of the cost savings. So that was kind of an interesting experience. And the reason why this is relevant is shortly after college, I saw underwater gliders and they kind of blew me away because when you see the typical range and duration of these things missions, it's pretty incredible. Around 3,000 kilometers on a single battery pack charge. And I work with electric vehicles professionally, partially as a consequence of this project. And I got to say, if you can show me a Nissan Leaf that can go 3,000 kilometers, I'll be pretty impressed. One of my coworkers says it's all about the drive cycle. So as I said, I'm flipper and this is kind of why I do electric vehicles professionally. They're ground vehicles here underwater. I keep on trying to talk my boss and let me turn one of our vehicles into a submarine but so far, no such luck. So, you know, I'm finished with my education and not much in the way of job options at the time. Kind of dead-end jobs and I'm killing time in the bathroom because I didn't really like my job. Reading the Oregonian and I see an article on Oregon State University's underwater glider program. And, you know, they're talking about how they work. They show a little cutaway diagram and I'm kind of blown away. It's all like, wait, wait, wait. Like how much do these cost? I could do that. You know, $100 tops. So that's where the $10,000 comes from is at one point in history that was about $100. A little bit of Jules Verne's too. So in order to build an underwater glider for $100, you kind of have to be an engineer or hacker, one of the two. I definitely wasn't an engineer so I guess that's why I'm here at DEF CON with you guys. So, you know, how do you design an underwater glider? You have to learn how to design an underwater glider. So it was really the start of an education, you know, self-taught in design and manufacture of underwater vehicles. So what I did was I was studying machine tool technology at the time, manufacturing engineering type stuff, eventually got a transfer degree. And so, yeah, it was a great vehicle to actually learn and gave a really good incentive to, you know, study STEM subject matter and ultimately transitioned into an interest in engineering transfer degree. So what is an underwater glider? Normal underwater vehicles propel themselves to the water using a propeller, pretty straightforward. There's no propeller on an underwater glider, generally speaking. They use something similar to a fish's swim ladder to change buoyancy in the water and as they float to the surface, they have wings on them. Does this thing work? Apparently not. So, wings. And those actually help transfer the change in altitude into forward movement. And so, the efficiency of the vehicle is going to be determined by a couple things. First of all, the efficiency of your fish bladder buoyancy engine. Your drag, big factor is your drag. And then also kind of related to drag is your glide ratio. How many feet forward you move through the water for every foot you lose or gain in altitude. One interesting thing of underwater vehicles is they spend about half the time flying upside down because, you know, your gravity vector flips its head when you are going against the water column or going down with it. So, yeah, there are autonomous underwater vehicles that can travel long distances and have battery power. So, history, you know, it all started back in, you know, 80s or something. I wasn't even born yet so it doesn't really matter. Very egocentric view of the universe. So, they had these things called Argos floats and they are essentially, you know, a coffee can with a big linear motor powered syringe and they go down through the water column and they collect sensor data and then when they had enough data they would float back to the surface, you know, satellite mode them, phone home and then they do it all over again. And based on my understanding of how things went down, one person was like, well, these things are really cool, you know, we are getting really good data. We are not having to send people out in boats, you know, $40,000 a day. But the problem is we can't actually control where they go. They are kind of like hot air balloons. So, it was like, what if we strap wings on them? And underwater gliders were born. Henry Stommel was one of the people who wrote some kind of pioneering articles on the potential applications of these things. And what you see before you today between the Scarlet Knight, the Slocum, the Spray, it's become a very popular vehicle class simply because of the range you can cover for the amount of energy you have to store. So, the Scarlet Knight is one of the record holders. It was put together by Rutgers University and it was essentially a Slocum glider that had been, you know, loaded down with extra battery mass and stretched out a little bit. It uses lithium CSC cells, is my understanding, which is kind of impressive because the high-test peroxide rocket fuel you see in the movie Moonraker, as far as I can actually, has lower energy density. So, those are pretty impressive batteries, although also fairly expensive. That's not what I ended up using. So, I don't know if this is the correct way to design underwater glider, but, you know, after going through, you know, 10, 20 designs in my head before even trying to build the first draft, this is kind of what I settled on as the proper procedure. Maybe somebody can correct me if I'm wrong, but you don't really know how you can package your components until you know what your components are. And buoyancy engine being one of the key elements is going to determine the efficiency. You really have to start with that. Energy storage system is going to be dictated by the energy requirement inside of your buoyancy and then, you know, hold design. It's pretty straightforward process. Very few moving parts. So, eventually I did, you know, I'm not a very decisive person, but eventually I did, you know, come to a conclusion on how I wanted to build one of these things. And that was with a phase change material. There's another vehicle out there that uses PCMs to propel itself through the water. It's called the Slokum thermal. And I'm not doing that because it looked really expensive. I read some NASA tech briefs talking about that concept. And I think it was like in Deccane, the alkane they used. And really expensive per ounce. Wasn't really on the table. My goal going into this was, remember, I said I could do this for $100. If I'm spending $200 on my phase change material, I'm kind of already blown out. So these were the design requirements I went into it with. I wanted the entry to be low because even though I had access to a milling machine in a lathe, not everybody does. So I wanted, you know, all of you to be able to take your DEF CON CD, take the solid models that are on there and go home and build one of these yourself. And then, you know, range of efficiency, you're not going to take a two order of magnitude reduction in cost without, you know, taking some hits on range, efficiency, performance. So it was kind of a best effort basis. I'm pretty optimistic. I've got a fairly large battery pack compared to the current consumption I'm looking at. So we'll see. Here's one of the earlier efforts I made into actually trying to design for manufacture. That's a Harbor Freight air compressor being used to index several syringes. And this design actually served as a lobe of inspiration for a hack I had to make towards the end of this project. Overall, the check valves involved were kind of a prohibitive feature that just disillusioned me with this concept. So, considered a lot of things, I struck out electric motors, linear actuators pretty early on in the process because, you know, at the time, you know, the milling machine were pretty much, you know, a requirement to make those happen. The weight of using an off the shelf linear actuator was pretty massive. You'd end up with like a scuba tank pressure housing and that's no fun. So wave and solar power, interesting concepts. I'd like to explore them a little bit, especially for one concept I might mention at the end. But overall hydraulic pumps and phase change materials kind of showed out to me as the best choices available. So paraffin wax expands 10% when it melts-ish. And it's got a very high specific heat. So when it does melt, it will stay liquid for a very long time. So I was looking at using soldering irons as a resistive load to actually melt the wax. And this is just kind of a breakdown comparison of various energy densities I was looking at for kind of guiding my decision on how to build the buoyancy engine. And when I first started on this project, there really wasn't much in the way available of low cost inertial navigation. You had the multi-wee project, which I thought was pretty genius. They took a nunchuck and a motion plus from a Wii game console and they actually made a 6-degree freedom IMU out of it. Welcome to the future. This is really cool. This is a $33 board available from Hobbyking. And I can't imagine they have more than $5 of profit margin built into that. You get a really cutting edge chip on there called the MPU 6050 or 6000, one of the two depending on if it's SPI or ITC. But the point is it's got a built-in magnetometer and so it can do complete 9-degree freedom sensor fusion, which is the ability to distinguish between gravity and linear movement through space. And when you're trying to actually integrate your inertial data, you'll run into problems unless you have some pretty good math background or a fantastic product like this behind you. That's the 3DR Robotics GPS chip. It was available. And it's actually buried in the nose cone of my vehicle right now, coated in a nice thick goop of RTV compound. Hole design was kind of fun. I spent most of the past year working on that as a specific aspect because it ultimately guided the production of the rest of the vehicle. Once I knew what I was packaging, I had to actually wrap it up into some sort of fluid dynamic hole form. And so based on the research I had, I'd heard some interesting things about 30 to 1 glide ratios with something called a NACA 004, which is pretty much a NACA 4-digit series 0030. But based on the simulations I did using a program called Profili 2, marketed at RC plane design, its main claim to fame was it didn't stall out at high angles of attack, whereas the black line has one of the sharpest peaks on there. So NACA 009 or 0009 was kind of out of the question too. So kind of middle of the road choice of the symmetric airfoils that were well understood at the time. Pretty common options are NACA 0015-ish. So I think my wing root is NACA 0015. And wing tip is NACA 002. And what that does is hopefully like the Rutan Long Easy, if you end up stalling out, the wing root stalls before the wing tips and that will cause the pitch to self-correct. Fingers crossed on that. Not a lot of testing in that regard. So first concept, I took a polycarbonate tube, a wax motor used to control a dishwasher latch, high force, high latency, low efficiency unfortunately as I found out later. And oh no, I'm not sure if I submitted my CFP at this point but I was kind of sweating at that time because I'm apparently really, really bad at fiberglass. Who knew? The original idea was that I would be using hot wire foam cutting techniques to actually generate the whole form and then lay fiberglass over it and as you can see from this picture, that wasn't going so hot. So not as easy as it looked on YouTube. Was not going to hit my deadline at that rate. So throw money at the problem. I've generally found that when time is of the essence, money can generally buy you time back. So I bought a 3D printer. I really am happy I made that decision. 3D printers are really cool. One of the design requirements, being able to build this thing in my underwear, check. So similar design, same whole form but now broken into smaller chunks to help with the print volume and also trying to minimize the overhang of the printed parts. Support material is an option and one of the largest prints on there actually was using support material but one month turnaround time, you really can't argue with that. And I knew 3D printing could really help expedite the design process and getting you through multiple iterations but until I had experienced it firsthand, kind of saving my bacon on getting improved concept out the door and second, third revision, whatever, I was incredibly impressed with the value. That 3D printer I showed was a Rostock Max. It's a Delta Bot style design and they are one of the coolest to look at when they're coming. Cartesian bots a little bit lame in my opinion. And that's the robot you see in front of you. So $100 price target, $31 a kilogram for my plastic, that could be cheaper but let's try and be generous just to make sure I don't underestimate. So $21 in plastic. So if you throw a significant amount of capital investment at the prospect of building projection molding tooling then that could come down significantly. Remaining bill of material was actually published to the DVD if I remember correctly and I mentioned there may have been some hiccups along the road. This bill of material is definitely not accurate to the $0.30 mark because the phase change material concept ended up working out to not just moderately inefficient to virtually unworkable at least with the energy storage system I selected. If you need your robot to go to the bottom of the Maryass trench the fact that it's a solid to liquid phase change as opposed to expansion and contraction of a gas really working to your advantage. But if you're going for range and you don't particularly want to be dragging bottom with seaweed, trying to get 3,000 meters depth with that process probably not the most efficient use of battery storage. So I think it was early May when I realized, wow, I've got a 200 volt pack or whatever and it's browning out at 100 milliamps,.1 amps. I knew that coin cells weren't exactly like lithium polymer or RC plane batteries but I was a little bit blown away. So I needed a Plan B or Plan C I guess. So what I came up with was something a little bit more conventional, trying to avoid too many experimental wild concepts and one vehicle build can be a lifesaver. So I went to the tried and true electric motor linear actuator because if you remember at the time my perception was those weren't really an option because people wouldn't have access to a lathe and mill. But with a 3D printer that potentially changes. So I ended up using commercial off the shelf McMaster car parts to build the assembly which you can see in white on the actual robot now. So the only change between what's on your DVD and what actually is here in front of you is the white assembly. Everything else I was able to recycle between designs. So modular design is a good thing I guess. The gray pipe was a really good choice. Sorry about that. The gray pipe was a really good choice because it allowed for routing of the wiring and ultimately acted as kind of a skeleton or a backbone for the entire vehicle. So what I learned from that process is 3D printing is awesome and the great thing is when you're actually done with it you don't have to go through an entire twisted new process to design 3D printed or injection molded parts. You're practically already there when you have a working prototype. What I learned through the process I feel like I actually hit a pretty good balance between fail early, fail often and not making stupid mistakes for lack of planning. I didn't build anything before I had complete solid model data and that's really valuable when you're trying to avoid these last minute crazed runs to Home Depot, West Marine, AutoZone, whatever it is. If you have a complete build of materials before you make the first part you know exactly what's going into the thing and you don't find yourself running into these issues where parts are colliding with each other. So and then it was also extremely difficult to quantify whether or not a design decision was a good or a bad one such as the wax motor until actually trying it. So it was a design decision tradeoff to not use so much simulation and I was pretty happy with how that went because you can simulate the daylights out of a bad idea and then find out you wasted last year doing you know, F.E.A. or CFD on broken design and then it's all wasted so prototypes can illuminate things that you otherwise wouldn't be aware of. So I did this entire thing out of pocket. No grants or funding agencies and I actually really like that because I'm accountable to myself and I don't have anybody breathing down my neck forcing me to chase sunk costs or make bad decisions because oh, I need to save face over that $1,000 I wasted on wax motors. On the other hand, I gave pretty much the profit of the design away for free on the DVD this year. I've probably spent around 15 grand on the project over the past decade and so I would consider it a dubious appropriation of my retirement savings. But you know, that was the mission from the start. I want people to be able to build these themselves and kind of empower themselves to deliver sensors, communications devices and payloads to remote destinations where traditionally it would be prohibitively expensive at you know, tens of thousands of dollars per vehicle and how that's possible is if your price is low enough, you can consider it disposable and you don't have to pay somebody 40 grand to go out in the water and change the batteries. So we'll see ultimately if you build it, they will come and if it's a good idea, hopefully people will say hey, maybe we should build some of these. So where to go from here? I didn't have an opportunity to test max depth because I only had one prototype as of two weeks ago and I didn't really want to lose it out in the ocean scuba diving. Like I guess I could have like tried to put a dog collar on it and you know, walked it like with a leash but overall it's disposable after my talk is over. But thing took over you know, 100 hours to print and actually that guy right there put in a significant amount of labor helping getting this thing ready for you guys' eyes. Small applause for him if you're willing. Thanks guys. So in terms of trimming vehicle, I can say with high degree of certainty this thing is very positively buoyant. Traditional buoyancy foam, polyurethane or epoxy and glass micro balloons. High crush depth, kind of unnecessary spacing is how I designed the vehicle with syringes. But overall a good choice. So generally speaking epoxy or urethane, I chose paraffin wax. It's low cost and over half the dollar per pound of buoyancy. I was seeing was either epoxy or polyurethane. So paraffin wax is like $4 a pound. So very positively buoyant. Every empty cavity in that entire thing has specific gravity about.5. So it's really just a matter of how you distribute your lead and batteries at this point to make sure that when the buoyancy engine is in a neutral position it's sitting about horizontal. Because when the vehicle goes buoyant, the center of buoyancy moves forward on the vehicle and it pitches towards the surface and the GPS chip starts rising up to its daylight. And when it goes negatively buoyant the opposite happens. So if you're a neutral buoyancy you should be sitting around level in the water. And it's really just a matter of adding weight and removing buoyancy foam as necessary to achieve that. I'm looking at around 40 to 50 milliliters of displacement change. So it's unknown at this time what the vehicle's velocity through the water is. The more buoyant it is the faster it's going to pop to the surface like a cork. And your speed through the water is going to determine what the Reynolds number is and that guides things like what airfoil you select. But first draft, I'd call it an alpha stage design and openglider.com is where I'm going to be adding future revisions. The one on your CD is rev 0.1 and rev 0.2 will be on openglider.com tonight and that will have the new white syringe based assembly. So yeah. In terms of research that went into this, this guy named Bruce Carmichael was one of the pioneers of the airfoil you see before you. It's called the X35 and originally it was known as the dolphin. But if I understand correctly they ran the dolphin through genetic algorithm and ultimately the citation, shaping of axiometric bodies for minimum drag, that one I think was where I was able to find the coordinates for this design. It does bear some resemblance to some other vehicles on the market and that shouldn't be too surprising seeing as far as I can tell we did use the same curve, rotate around its axis to generate the main body. Otherwise the NACA 4 digit series, pretty common equation and I threw something in here that I found really fascinating. It's the geometry of a blended wing body morphing wing and that was the idea that you could actually design an entire vehicle around variables and equations. So you can change something like a static wing sweep from 30 degrees to 15 to 25 degrees and rather than having a lot of hard engineering labor going into remaking the entire design, it just regenerates itself. So very early on in the process I was trying to stick to that concept and I was pretty pleased. I would change the variable from NACA 4 digit, 002 to NACA 005, kind of crazy and hit rebuild and the model would regenerate itself with very little labor on my part. One thing I'd like to explore is potentially even doing a genetic algorithm around that concept to optimize for parameters like speed through the water column and lift to dry ratio. So that's pretty much how I got here. The X35 took me like six months to a year to even find. I had no idea where people were getting this curve from but I saw it in several places. Ultimately it was just a mad Google foo that was able to illuminate the coordinates to build this thing. In terms of other information on how to build an underwater vehicle, I was going to joke every story, Ciro has a favorite weapon, Brock Samson's Bowie knife, Will Smith's little cricket and flippers hot glue gun. When you're trying to waterproof stuff, I've tried a lot of things, conformal coat, epoxy potting, pressure housings and overall even paraffin wax actually. It's not going to do very good in the Caribbean where the water gets damn near 80 degrees Celsius. It does a pretty good job because when you pot your electronics in epoxy it's very difficult to actually repair them or repair them if something blows up. But when you're using paraffin wax, the 80 degree C melting temperature is actually below the rated temperature for most electronics so if you decide you want to change something about them and I've had to, you can just use a hot air gun or boiling water to rescue your electronics. That said, from a durability standpoint, paraffin wax, even if you anneal it with a little bit of mineral oil, not the most durable thing ever. So ultimately hot glue has been my favorite approach to water proofing. If you need something a little bit lower, viscossi, get down in the English muffin nooks and crannies, then they make low viscossi silicone RTV. The acetic acid can potentially corrode your electrical contacts but we're talking about disposable vehicles here. It doesn't have to last three years. I've got electronic speed controllers. I potted for the RoboSpub competition two years ago that still work. And that was just plain Jane AutoZone RTV compound. And so pretty much every beast of electronics on that thing are just either code and hot glue or RTV compound. And it's a pretty easy, low cost way of waterproofing electronics. So I guess at this time it would be a good way to go for questions. Yeah, that's a good question. So one of the problems with underwater vehicles that make some kind of interesting to me is unlike, you know, Mars rovers, you know, easy environment, you know, aerial vehicles, a bunch of light weights, you know, these people, they're so spoiled. With underwater vehicles, you don't get to talk to your robot after you let it go until it comes back to the surface at which point. You know, it's kind of a surface vehicle until it goes back underwater snorkel depth style. So no radio frequency communication so it has to be pretty much all autonomous. And the source code I used with the IMU to actually, it's called a Haversine formula. It finds your current GPS coordinates and your destination GPS coordinates and gives you a bearing. And the distance you need to go to get there. So it's pretty much a line follower robot. That's what makes underwater gliders potentially so successful is unlike, you know, mind detecting robots or, you know, anti-frogman stuff. They have a pretty basic mission which is go from point A to point B. So object avoidance potentially with sonar. But, you know, suddenly when your payload starts getting into the, you know, high dollar sonar stuff, it stops being so disposable. At that point, you know, my 3D printed open glider may not be the best choice of vehicles. So testing has been kind of an iterative process. I've learned every time I stuck in the bathtub. Early on, it was pretty much with a small car battery and some red and green wire hanging out of the thing. Underwater vehicles can actually be communicated with remotely using something called a tether. At which point, they're no longer AUVs or UUVs or ROVs, remotely operated vehicles. And I had two years of tethered vehicle competitions that kind of prepared me for working with the unmanned side of things. And it's a pretty good way to go. So for testing, bathtubs are surprisingly effective. You have them in hotel rooms. And yeah, generally speaking, the main thing you're going to be testing is either what it decides to do when it gets in the water or how it sits in the water when you put it in there. And both of those things don't require a big swimming pool. Also, a lot less terrified, shrieking swimmers running away from the evil robot. It's the second one. So I don't really rely on pressure housings as a rule. I had to depend on some amount of air cavity for the design fix. And it's the most conventional thing about this design was you've got little linear actuators driven by 3 volt gear motors. Actually, I think I have one. Anybody want one? I know audiences love things being thrown at them. Not you, Mark. Oh, hey, speaking of that, anybody want a flight controller? $33, give me. Remember, two is one, one is none. So bring spare parts. Sorry. I throw like a roboticist. More questions. Oh, good question. So when you have like a tank light when you're scuba diving, you can actually make them water active. They're only wasting battery life when you're in the water and you're trying not to lose your dive buddy. In my case, I don't have anything smart like that on my robot. So those wires allow me to disconnect the power supply from the actual microcontroller. Because once I plug it in, it just goes and it will keep going until I unplug it. Oh, really good question. I was at an ROV conference and this guy who is like super salty, you know, had been out in the field for a long time, told me a really cool trick. You go to like Harbor Freight and they'll sell these heat shrink packages, marine heat shrink. And it's just heat shrink that's been lined with hot glue. And you don't need to use special heat shrink or wire crimps. You can just take your wire splice, coat it in hot glue and then run heat shrink over it. And when you melt the heat shrink or shrink the heat shrink, it will melt the hot glue again and pull all the air bubbles out. Great question. How does it work? Oh, yeah, no, I totally glossed over on that. Really good point. So I don't actually have one buoyancy engine. I have four. And generally speaking, you might have them towards the top of the vehicle. I have them low on the center of gravity because I had two places I could put them top or bottom. And the top was all being used by syntactic foam or syntactic wax buoyancy sand. And since that was more buoyant than the buoyancy engines themselves, I have them down low. And so I have broken the cross section of my vehicle into eight little slices of pie. The top four are full of buoyancy sand and the bottom four, there are two pairs. So when you trigger the two on the left, your left side is going to be more buoyant than your right side. So one wing will lift up. And likewise, if you use the two on the right, it's going to change the attitude the other way. So this is one unique thing about my vehicle design. Traditionally, you actually move your battery mass, whereas I'm just having four times the buoyancy engines that are typical. And finally, you know, if you change buoyancy on the bottom two, then you'll just go straight. So you have to use your inertial system for just independent operations. How often do you have to go to the surface to get GPS fixed to? How accurate is the GPS? Good question. So I can say with pretty good confidence that my inertial navigation system is not high enough quality to the U.S. munitions list grade. So that's totally a relief. Yeah, these are hobby components. So video game grade, in terms of actual like integration of my velocity or whatever to get my position, I don't really do any of that. I've been working a little bit in my free time with trying to use fetal Doppler monitors, which measure the velocity of fluid through baby's blood to, you know, let you listen to the kid's heartbeat, kind of cool. And they're essentially homodines, ultrasonic homodines. And I've been looking at potentially getting some velocity information from that. But pretty much I figure out which direction I want to go. And it's a line follower bot. It says, I know I need to go either left, right, or straight. And it dives and it comes to the surface and it says, oh, wow, I missed my target. But okay, now I need to go. You know, it doesn't really look backwards, only forwards. Good question. Thanks. Oh, bathtub depths. Okay, originally, I had a washing machine wax motor from like a, I think it was a whirlpool Neptune or something. And that one didn't get a lot of mileage simply because the fiberglass thing went so terrible. Just didn't really work into the 3D printed picture. So then I moved to a soldering iron based design. I was using silicone high temperature rubber hose and soldering irons and filling them with wax. And I was browning out my power supply, even though I only needed about 100 milliamps, it was still too much. And it would have been a pretty big design tear up to change my batteries. So I just changed my buoyancy engine. Questions? Really good question. So in the original solid model I designed around, I actually made a solid model of the PX4 autopilot from DIY drones or PX. I don't really know what that relationship is, but it's a really good board. It uses a publisher subscriber system. And so right now I'm only using the IMU, the micro-wee board for everything. And one of the issues with that decision is it is so flash memory constrained that you can only just barely compile the source code included on your DVD. In fact, if you try and use Arduino 1.5.2 to do so, it's not going to work for you. You have to use Arduino 1.0.4 if I remember correctly. And that will work. So I didn't remember to put that in the slides and I'm glad you brought it up. So there is a reasonable amount of space, about one quarter of the size of an Altoid 10, maybe half the size of an Altoid 10 for a supervisory controller to supplement the IMU. The IMU is broadcasting yaw, pitch, roll information that's already been fused. So it's pretty much relative to your world body or world coordinate system. And it's really nice because it's publishing it on the serial port and it's also telling you time's up. All right. Any further questions or wanting to see the robot in person, touch and feel, I'll meet you guys out in the hallway, I guess. Thank you.
 everybody, don't be shy if you want to move up front. There you  over there. Anyway, 10,000 yen into the sea. Let's give him a big  hand. Say something like, come on. Awesome. Hello. So as he said,  I'm flipper. This is my talk, 10,000 yen into the sea. Essentially,  I mean, just to start with, can I show a hands who enjoys  filling up their gas tank? Yeah, I'm not a big fan of it either.  Actually, I spent four years commuting to and from my community  college. Four years, two year program. I had other things to do. So  it was a 45 minute drive each way. So I pretty much ended up  putting about as much money into my tank as I saved by living in  my parent's basement. So all the benefits of living in my parent's basement  with none of the cost savings. So that was kind of an interesting experience.  And the reason why this is relevant is shortly after college, I saw  underwater gliders and they kind of blew me away because when you see  the typical range and duration of these things missions, it's pretty  incredible. Around 3,000 kilometers on a single battery pack charge.  And I work with electric vehicles professionally, partially as a  consequence of this project. And I got to say, if you can show me a  Nissan Leaf that can go 3,000 kilometers, I'll be pretty impressed.  One of my coworkers says it's all about the drive cycle. So as I said, I'm  flipper and this is kind of why I do electric vehicles professionally.  They're ground vehicles here underwater. I keep on trying to talk  my boss and let me turn one of our vehicles into a submarine but so  far, no such luck. So, you know, I'm finished with my education and  not much in the way of job options at the time. Kind of dead-end jobs and  I'm killing time in the bathroom because I didn't really like my job.  Reading the Oregonian and I see an article on Oregon State University's  underwater glider program. And, you know, they're talking about how they work.  They show a little cutaway diagram and I'm kind of blown away. It's all  like, wait, wait, wait. Like how much do these cost? I could do that.  You know, $100 tops. So that's where the $10,000 comes from is at one  point in history that was about $100. A little bit of Jules Verne's too.  So in order to build an underwater glider for $100, you kind of have to  be an engineer or hacker, one of the two. I definitely wasn't an engineer  so I guess that's why I'm here at DEF CON with you guys. So, you know, how do  you design an underwater glider? You have to learn how to design an  underwater glider. So it was really the start of an education, you know,  self-taught in design and manufacture of underwater vehicles. So what  I did was I was studying machine tool technology at the time, manufacturing  engineering type stuff, eventually got a transfer degree. And so, yeah, it  was a great vehicle to actually learn and gave a really good incentive to,  you know, study STEM subject matter and ultimately transitioned into an  interest in engineering transfer degree. So what is an underwater glider?  Normal underwater vehicles propel themselves to the water using a  propeller, pretty straightforward. There's no propeller on an underwater  glider, generally speaking. They use something similar to a fish's swim  ladder to change buoyancy in the water and as they float to the surface,  they have wings on them. Does this thing work? Apparently not. So, wings.  And those actually help transfer the change in altitude into forward  movement. And so, the efficiency of the vehicle is going to be determined by  a couple things. First of all, the efficiency of your fish bladder  buoyancy engine. Your drag, big factor is your drag. And then also kind of  related to drag is your glide ratio. How many feet forward you move through  the water for every foot you lose or gain in altitude. One interesting  thing of underwater vehicles is they spend about half the time flying  upside down because, you know, your gravity vector flips its head when  you are going against the water column or going down with it. So, yeah,  there are autonomous underwater vehicles that can travel long distances  and have battery power. So, history, you know, it all started back in,  you know, 80s or something. I wasn't even born yet so it doesn't really  matter. Very egocentric view of the universe. So, they had these things  called Argos floats and they are essentially, you know, a coffee can  with a big linear motor powered syringe and they go down through the  water column and they collect sensor data and then when they had enough data  they would float back to the surface, you know, satellite mode them, phone  home and then they do it all over again. And based on my understanding  of how things went down, one person was like, well, these things are  really cool, you know, we are getting really good data. We are not  having to send people out in boats, you know, $40,000 a day. But the  problem is we can't actually control where they go. They are kind of like  hot air balloons. So, it was like, what if we strap wings on them? And  underwater gliders were born. Henry Stommel was one of the people who  wrote some kind of pioneering articles on the potential applications of  these things. And what you see before you today between the Scarlet  Knight, the Slocum, the Spray, it's become a very popular vehicle class  simply because of the range you can cover for the amount of energy you  have to store. So, the Scarlet Knight is one of the record holders. It  was put together by Rutgers University and it was essentially a  Slocum glider that had been, you know, loaded down with extra battery  mass and stretched out a little bit. It uses lithium CSC cells, is  my understanding, which is kind of impressive because the high-test  peroxide rocket fuel you see in the movie Moonraker, as far as I can  actually, has lower energy density. So, those are pretty impressive  batteries, although also fairly expensive. That's not what I ended up  using. So, I don't know if this is the correct way to design underwater  glider, but, you know, after going through, you know, 10, 20 designs in  my head before even trying to build the first draft, this is kind of  what I settled on as the proper procedure. Maybe somebody can correct  me if I'm wrong, but you don't really know how you can package your  components until you know what your components are. And buoyancy  engine being one of the key elements is going to determine the  efficiency. You really have to start with that. Energy storage  system is going to be dictated by the energy requirement inside of  your buoyancy and then, you know, hold design. It's pretty  straightforward process. Very few moving parts. So, eventually I did,  you know, I'm not a very decisive person, but eventually I did, you  know, come to a conclusion on how I wanted to build one of these  things. And that was with a phase change material. There's another  vehicle out there that uses PCMs to propel itself through the  water. It's called the Slokum thermal. And I'm not doing that  because it looked really expensive. I read some NASA tech  briefs talking about that concept. And I think it was like in  Deccane, the alkane they used. And really expensive per ounce.  Wasn't really on the table. My goal going into this was, remember,  I said I could do this for $100. If I'm spending $200 on my  phase change material, I'm kind of already blown out. So these  were the design requirements I went into it with. I wanted the  entry to be low because even though I had access to a milling  machine in a lathe, not everybody does. So I wanted, you know,  all of you to be able to take your DEF CON CD, take the solid  models that are on there and go home and build one of these  yourself. And then, you know, range of efficiency, you're not  going to take a two order of magnitude reduction in cost  without, you know, taking some hits on range, efficiency,  performance. So it was kind of a best effort basis. I'm pretty  optimistic. I've got a fairly large battery pack compared to  the current consumption I'm looking at. So we'll see. Here's  one of the earlier efforts I made into actually trying to  design for manufacture. That's a Harbor Freight air compressor  being used to index several syringes. And this design  actually served as a lobe of inspiration for a hack I had to  make towards the end of this project. Overall, the check  valves involved were kind of a prohibitive feature that just  disillusioned me with this concept. So, considered a lot of  things, I struck out electric motors, linear actuators pretty  early on in the process because, you know, at the time, you know,  the milling machine were pretty much, you know, a requirement  to make those happen. The weight of using an off the shelf  linear actuator was pretty massive. You'd end up with like a  scuba tank pressure housing and that's no fun. So wave and  solar power, interesting concepts. I'd like to explore  them a little bit, especially for one concept I might mention  at the end. But overall hydraulic pumps and phase change  materials kind of showed out to me as the best choices  available. So paraffin wax expands 10% when it melts-ish. And  it's got a very high specific heat. So when it does melt, it  will stay liquid for a very long time. So I was looking at  using soldering irons as a resistive load to actually melt  the wax. And this is just kind of a breakdown comparison of  various energy densities I was looking at for kind of guiding  my decision on how to build the buoyancy engine. And when I  first started on this project, there really wasn't much in the  way available of low cost inertial navigation. You had the  multi-wee project, which I thought was pretty genius. They  took a nunchuck and a motion plus from a Wii game console and  they actually made a 6-degree freedom IMU out of it. Welcome to  the future. This is really cool. This is a $33 board available  from Hobbyking. And I can't imagine they have more than $5  of profit margin built into that. You get a really cutting edge  chip on there called the MPU 6050 or 6000, one of the two  depending on if it's SPI or ITC. But the point is it's got a  built-in magnetometer and so it can do complete 9-degree  freedom sensor fusion, which is the ability to distinguish  between gravity and linear movement through space. And  when you're trying to actually integrate your inertial data,  you'll run into problems unless you have some pretty good math  background or a fantastic product like this behind you. That's  the 3DR Robotics GPS chip. It was available. And it's  actually buried in the nose cone of my vehicle right now, coated  in a nice thick goop of RTV compound. Hole design was kind of  fun. I spent most of the past year working on that as a  specific aspect because it ultimately guided the production  of the rest of the vehicle. Once I knew what I was packaging, I had  to actually wrap it up into some sort of fluid dynamic hole form.  And so based on the research I had, I'd heard some interesting  things about 30 to 1 glide ratios with something called a  NACA 004, which is pretty much a NACA 4-digit series 0030. But  based on the simulations I did using a program called Profili  2, marketed at RC plane design, its main claim to fame was it  didn't stall out at high angles of attack, whereas the black line  has one of the sharpest peaks on there. So NACA 009 or 0009 was  kind of out of the question too. So kind of middle of the road  choice of the symmetric airfoils that were well understood at the  time. Pretty common options are NACA 0015-ish. So I think my  wing root is NACA 0015. And wing tip is NACA 002. And what that  does is hopefully like the Rutan Long Easy, if you end up  stalling out, the wing root stalls before the wing tips and  that will cause the pitch to self-correct. Fingers crossed on  that. Not a lot of testing in that regard. So first concept, I  took a polycarbonate tube, a wax motor used to control a  dishwasher latch, high force, high latency, low efficiency  unfortunately as I found out later. And oh no, I'm not sure  if I submitted my CFP at this point but I was kind of sweating  at that time because I'm apparently really, really bad at  fiberglass. Who knew? The original idea was that I would be  using hot wire foam cutting techniques to actually generate  the whole form and then lay fiberglass over it and as you  can see from this picture, that wasn't going so hot. So not as  easy as it looked on YouTube. Was not going to hit my deadline  at that rate. So throw money at the problem. I've generally  found that when time is of the essence, money can generally  buy you time back. So I bought a 3D printer. I really am happy I  made that decision. 3D printers are really cool. One of the  design requirements, being able to build this thing in my  underwear, check. So similar design, same whole form but now  broken into smaller chunks to help with the print volume and  also trying to minimize the overhang of the printed parts.  Support material is an option and one of the largest prints  on there actually was using support material but one month  turnaround time, you really can't argue with that. And I knew  3D printing could really help expedite the design process and  getting you through multiple iterations but until I had  experienced it firsthand, kind of saving my bacon on getting  improved concept out the door and second, third revision,  whatever, I was incredibly impressed with the value. That  3D printer I showed was a Rostock Max. It's a Delta Bot style  design and they are one of the coolest to look at when they're  coming. Cartesian bots a little bit lame in my opinion. And  that's the robot you see in front of you. So $100 price  target, $31 a kilogram for my plastic, that could be cheaper  but let's try and be generous just to make sure I don't  underestimate. So $21 in plastic. So if you throw a significant  amount of capital investment at the prospect of building  projection molding tooling then that could come down  significantly. Remaining bill of material was actually published  to the DVD if I remember correctly and I mentioned there  may have been some hiccups along the road. This bill of  material is definitely not accurate to the $0.30 mark because  the phase change material concept ended up working out to  not just moderately inefficient to virtually unworkable at  least with the energy storage system I selected. If you need  your robot to go to the bottom of the Maryass trench the fact  that it's a solid to liquid phase change as opposed to  expansion and contraction of a gas really working to your  advantage. But if you're going for range and you don't  particularly want to be dragging bottom with seaweed, trying to  get 3,000 meters depth with that process probably not the most  efficient use of battery storage. So I think it was early  May when I realized, wow, I've got a 200 volt pack or whatever  and it's browning out at 100 milliamps,.1 amps. I knew that  coin cells weren't exactly like lithium polymer or RC plane  batteries but I was a little bit blown away. So I needed a  Plan B or Plan C I guess. So what I came up with was something  a little bit more conventional, trying to avoid too many  experimental wild concepts and one vehicle build can be a  lifesaver. So I went to the tried and true electric motor  linear actuator because if you remember at the time my perception  was those weren't really an option because people wouldn't have  access to a lathe and mill. But with a 3D printer that  potentially changes. So I ended up using commercial off the  shelf McMaster car parts to build the assembly which you can see  in white on the actual robot now.  So the only change between what's on your DVD and what  actually is here in front of you is the white assembly.  Everything else I was able to recycle between designs. So  modular design is a good thing I guess. The gray pipe was a  really good choice. Sorry about that. The gray pipe was a  really good choice because it allowed for routing of the  wiring and ultimately acted as kind of a skeleton or a backbone  for the entire vehicle. So what I learned from that process is  3D printing is awesome and the great thing is when you're  actually done with it you don't have to go through an entire  twisted new process to design 3D printed or injection molded  parts. You're practically already there when you have a working  prototype. What I learned through the process I feel like I  actually hit a pretty good balance between fail early, fail  often and not making stupid mistakes for lack of planning.  I didn't build anything before I had complete solid model data  and that's really valuable when you're trying to avoid these  last minute crazed runs to Home Depot, West Marine, AutoZone,  whatever it is. If you have a complete build of materials  before you make the first part you know exactly what's going  into the thing and you don't find yourself running into these  issues where parts are colliding with each other. So and then  it was also extremely difficult to quantify whether or not a  design decision was a good or a bad one such as the wax motor  until actually trying it. So it was a design decision tradeoff to  not use so much simulation and I was pretty happy with how that  went because you can simulate the daylights out of a bad idea  and then find out you wasted last year doing you know, F.E.A.  or CFD on broken design and then it's all wasted so prototypes  can illuminate things that you otherwise wouldn't be aware of.  So I did this entire thing out of pocket. No grants or funding  agencies and I actually really like that because I'm accountable  to myself and I don't have anybody breathing down my neck  forcing me to chase sunk costs or make bad decisions because  oh, I need to save face over that $1,000 I wasted on wax motors.  On the other hand, I gave pretty much the profit of the design  away for free on the DVD this year. I've probably spent around  15 grand on the project over the past decade and so I would  consider it a dubious appropriation of my retirement savings.  But you know, that was the mission from the start. I want people  to be able to build these themselves and kind of empower  themselves to deliver sensors, communications devices and  payloads to remote destinations where traditionally it would  be prohibitively expensive at you know, tens of thousands of  dollars per vehicle and how that's possible is if your price  is low enough, you can consider it disposable and you don't have  to pay somebody 40 grand to go out in the water and change the  batteries. So we'll see ultimately if you build it, they  will come and if it's a good idea, hopefully people will say  hey, maybe we should build some of these. So where to go from  here? I didn't have an opportunity to test max depth  because I only had one prototype as of two weeks ago and I  didn't really want to lose it out in the ocean scuba diving.  Like I guess I could have like tried to put a dog collar on it  and you know, walked it like with a leash but overall it's  disposable after my talk is over. But thing took over you know,  100 hours to print and actually that guy right there put in a  significant amount of labor helping getting this thing ready  for you guys' eyes. Small applause for him if you're willing.  Thanks guys. So in terms of trimming vehicle, I can say  with high degree of certainty this thing is very positively  buoyant. Traditional buoyancy foam, polyurethane or epoxy and  glass micro balloons. High crush depth, kind of unnecessary  spacing is how I designed the vehicle with syringes. But  overall a good choice. So generally speaking epoxy or  urethane, I chose paraffin wax. It's low cost and over half the  dollar per pound of buoyancy. I was seeing was either epoxy or  polyurethane. So paraffin wax is like $4 a pound. So very  positively buoyant. Every empty cavity in that entire thing has  specific gravity about.5. So it's really just a matter of how  you distribute your lead and batteries at this point to make  sure that when the buoyancy engine is in a neutral position  it's sitting about horizontal. Because when the vehicle goes  buoyant, the center of buoyancy moves forward on the vehicle  and it pitches towards the surface and the GPS chip starts  rising up to its daylight. And when it goes negatively buoyant  the opposite happens. So if you're a neutral buoyancy you  should be sitting around level in the water. And it's really  just a matter of adding weight and removing buoyancy foam as  necessary to achieve that. I'm looking at around 40 to 50  milliliters of displacement change. So it's unknown at this  time what the vehicle's velocity through the water is. The  more buoyant it is the faster it's going to pop to the surface  like a cork. And your speed through the water is going to  determine what the Reynolds number is and that guides  things like what airfoil you select. But first draft, I'd  call it an alpha stage design and openglider.com is where  I'm going to be adding future revisions. The one on your CD  is rev 0.1 and rev 0.2 will be on openglider.com tonight and  that will have the new white syringe based assembly. So  yeah. In terms of research that went into this, this guy  named Bruce Carmichael was one of the pioneers of the airfoil  you see before you. It's called the X35 and originally it was  known as the dolphin. But if I understand correctly they ran  the dolphin through genetic algorithm and ultimately the  citation, shaping of axiometric bodies for minimum drag, that  one I think was where I was able to find the coordinates for  this design. It does bear some resemblance to some other vehicles  on the market and that shouldn't be too surprising seeing as far  as I can tell we did use the same curve, rotate around its  axis to generate the main body. Otherwise the NACA 4 digit  series, pretty common equation and I threw something in here  that I found really fascinating. It's the geometry of a  blended wing body morphing wing and that was the idea that  you could actually design an entire vehicle around variables  and equations. So you can change something like a static wing  sweep from 30 degrees to 15 to 25 degrees and rather than having  a lot of hard engineering labor going into remaking the entire  design, it just regenerates itself. So very early on in the  process I was trying to stick to that concept and I was pretty  pleased. I would change the variable from NACA 4 digit, 002 to  NACA 005, kind of crazy and hit rebuild and the model would  regenerate itself with very little labor on my part. One  thing I'd like to explore is potentially even doing a genetic  algorithm around that concept to optimize for parameters like  speed through the water column and lift to dry ratio. So that's  pretty much how I got here. The X35 took me like six months to  a year to even find. I had no idea where people were getting  this curve from but I saw it in several places. Ultimately it  was just a mad Google foo that was able to illuminate the  coordinates to build this thing. In terms of other information  on how to build an underwater vehicle, I was going to joke  every story, Ciro has a favorite weapon, Brock Samson's Bowie  knife, Will Smith's little cricket and flippers hot glue gun.  When you're trying to waterproof stuff, I've tried a lot of  things, conformal coat, epoxy potting, pressure housings and  overall even paraffin wax actually. It's not going to do  very good in the Caribbean where the water gets damn near 80  degrees Celsius. It does a pretty good job because when you  pot your electronics in epoxy it's very difficult to actually  repair them or repair them if something blows up. But when  you're using paraffin wax, the 80 degree C melting temperature  is actually below the rated temperature for most electronics  so if you decide you want to change something about them and  I've had to, you can just use a hot air gun or boiling water to  rescue your electronics. That said, from a durability  standpoint, paraffin wax, even if you anneal it with a little  bit of mineral oil, not the most durable thing ever. So  ultimately hot glue has been my favorite approach to water  proofing. If you need something a little bit lower, viscossi,  get down in the English muffin nooks and crannies, then they  make low viscossi silicone RTV. The acetic acid can  potentially corrode your electrical contacts but we're  talking about disposable vehicles here. It doesn't have to  last three years. I've got electronic speed controllers. I  potted for the RoboSpub competition two years ago that  still work. And that was just plain Jane AutoZone RTV  compound. And so pretty much every beast of electronics on  that thing are just either code and hot glue or RTV compound.  And it's a pretty easy, low cost way of waterproofing  electronics. So I guess at this time it would be a good way  to go for questions. Yeah, that's a good question. So one of  the problems with underwater vehicles that make some kind of  interesting to me is unlike, you know, Mars rovers, you know,  easy environment, you know, aerial vehicles, a bunch of  light weights, you know, these people, they're so spoiled. With  underwater vehicles, you don't get to talk to your robot after  you let it go until it comes back to the surface at which  point. You know, it's kind of a surface vehicle until it goes  back underwater snorkel depth style. So no radio frequency  communication so it has to be pretty much all autonomous. And  the source code I used with the IMU to actually, it's called a  Haversine formula. It finds your current GPS coordinates and  your destination GPS coordinates and gives you a bearing. And  the distance you need to go to get there. So it's pretty much a  line follower robot. That's what makes underwater gliders  potentially so successful is unlike, you know, mind detecting  robots or, you know, anti-frogman stuff. They have a pretty  basic mission which is go from point A to point B. So object  avoidance potentially with sonar. But, you know, suddenly when  your payload starts getting into the, you know, high dollar sonar  stuff, it stops being so disposable. At that point, you  know, my 3D printed open glider may not be the best choice of  vehicles. So testing has been kind of an iterative process. I've  learned every time I stuck in the bathtub. Early on, it was  pretty much with a small car battery and some red and green  wire hanging out of the thing. Underwater vehicles can  actually be communicated with remotely using something called  a tether. At which point, they're no longer AUVs or UUVs or  ROVs, remotely operated vehicles. And I had two years of  tethered vehicle competitions that kind of prepared me for  working with the unmanned side of things. And it's a pretty good  way to go. So for testing, bathtubs are surprisingly  effective. You have them in hotel rooms. And yeah, generally  speaking, the main thing you're going to be testing is either  what it decides to do when it gets in the water or how it sits  in the water when you put it in there. And both of those things  don't require a big swimming pool. Also, a lot less  terrified, shrieking swimmers running away from the evil robot.  It's the second one. So I don't really rely on pressure  housings as a rule. I had to depend on some amount of air  cavity for the design fix. And it's the most conventional  thing about this design was you've got little linear actuators  driven by 3 volt gear motors. Actually, I think I have one.  Anybody want one? I know audiences love things being thrown  at them. Not you, Mark. Oh, hey, speaking of that, anybody want  a flight controller? $33, give me. Remember, two is one, one is  none. So bring spare parts. Sorry. I throw like a roboticist.  More questions. Oh, good question. So when you have like a  tank light when you're scuba diving, you can actually make  them water active. They're only wasting battery life when you're  in the water and you're trying not to lose your dive buddy. In  my case, I don't have anything smart like that on my robot. So  those wires allow me to disconnect the power supply from the  actual microcontroller. Because once I plug it in, it just  goes and it will keep going until I unplug it. Oh, really good  question. I was at an ROV conference and this guy who is  like super salty, you know, had been out in the field for a  long time, told me a really cool trick. You go to like  Harbor Freight and they'll sell these heat shrink packages,  marine heat shrink. And it's just heat shrink that's been  lined with hot glue. And you don't need to use special heat  shrink or wire crimps. You can just take your wire splice,  coat it in hot glue and then run heat shrink over it. And when  you melt the heat shrink or shrink the heat shrink, it will  melt the hot glue again and pull all the air bubbles out.  Great question. How does it work? Oh, yeah, no, I totally  glossed over on that. Really good point. So I don't actually  have one buoyancy engine. I have four. And generally speaking,  you might have them towards the top of the vehicle. I have them  low on the center of gravity because I had two places I  could put them top or bottom. And the top was all being used  by syntactic foam or syntactic wax buoyancy sand. And since  that was more buoyant than the buoyancy engines themselves, I  have them down low. And so I have broken the cross section of  my vehicle into eight little slices of pie. The top four are  full of buoyancy sand and the bottom four, there are two pairs.  So when you trigger the two on the left, your left side is  going to be more buoyant than your right side. So one wing will  lift up. And likewise, if you use the two on the right, it's  going to change the attitude the other way. So this is one  unique thing about my vehicle design. Traditionally, you  actually move your battery mass, whereas I'm just having four  times the buoyancy engines that are typical. And finally, you  know, if you change buoyancy on the bottom two, then you'll  just go straight.  So you have to use your inertial system for just  independent operations. How often do you have to go to the  surface to get GPS fixed to? How accurate is the  GPS? Good question. So I can say with pretty good  confidence that my inertial navigation system is not high  enough quality to the U.S. munitions list grade. So that's  totally a relief. Yeah, these are hobby components. So video  game grade, in terms of actual like integration of my velocity  or whatever to get my position, I don't really do any of that.  I've been working a little bit in my free time with trying to  use fetal Doppler monitors, which measure the velocity of  fluid through baby's blood to, you know, let you listen to  the kid's heartbeat, kind of cool. And they're essentially  homodines, ultrasonic homodines. And I've been looking at  potentially getting some velocity information from that. But  pretty much I figure out which direction I want to go. And it's  a line follower bot. It says, I know I need to go either left,  right, or straight. And it dives and it comes to the surface  and it says, oh, wow, I missed my target. But okay, now I need  to go. You know, it doesn't really look backwards, only  forwards. Good question. Thanks. Oh, bathtub depths. Okay,  originally, I had a washing machine wax motor from like a, I  think it was a whirlpool Neptune or something. And that one  didn't get a lot of mileage simply because the fiberglass  thing went so terrible. Just didn't really work into the 3D  printed picture. So then I moved to a soldering iron based  design. I was using silicone high temperature rubber hose and  soldering irons and filling them with wax. And I was browning  out my power supply, even though I only needed about 100  milliamps, it was still too much. And it would have been a  pretty big design tear up to change my batteries. So I just  changed my buoyancy engine. Questions?  Really good question. So in the original solid model I designed  around, I actually made a solid model of the PX4 autopilot from  DIY drones or PX. I don't really know what that relationship is,  but it's a really good board. It uses a publisher subscriber  system. And so right now I'm only using the IMU, the  micro-wee board for everything. And one of the issues with that  decision is it is so flash memory constrained that you can only  just barely compile the source code included on your DVD. In  fact, if you try and use Arduino 1.5.2 to do so, it's not  going to work for you. You have to use Arduino 1.0.4 if I  remember correctly. And that will work. So I didn't remember  to put that in the slides and I'm glad you brought it up. So there  is a reasonable amount of space, about one quarter of the size  of an Altoid 10, maybe half the size of an Altoid 10 for a  supervisory controller to supplement the IMU. The IMU is  broadcasting yaw, pitch, roll information that's already been  fused. So it's pretty much relative to your world body or  world coordinate system. And it's really nice because it's  publishing it on the serial port and it's also telling you  time's up. All right. Any further questions or wanting to  see the robot in person, touch and feel, I'll meet you guys out  in the hallway, I guess. Thank you.
DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_0_2759.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_2760_3203.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_3204_3791.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_3792_5747.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_5748_5891.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_5892_6407.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_6408_6587.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_6588_7895.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_7896_9419.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_9420_10355.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_10356_10631.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_10632_10799.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_10800_11699.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_11700_12791.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_12792_12935.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_12936_13343.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_13344_14183.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_14184_14927.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_14928_15887.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_15888_16259.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_16260_16631.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_16632_18575.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_18576_20651.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_20652_20939.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_20940_21347.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_21348_21947.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_21948_22043.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_22044_22127.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_22128_22607.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_22608_23015.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_23016_24023.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_24024_25823.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_25824_26495.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_26496_27287.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_27288_27479.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_27480_28523.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_28524_30251.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_30252_30383.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_30384_32531.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_32532_36971.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_36972_40679.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_40680_43763.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_43764_45155.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_45156_59231.png DEF_CON_21_-_Flipper_-_10_000_Yen_into_the_Sea_AXQ7Qaxw2Cc_59232_59270.png
everybody, don't be shy if you want to move up front. There you over there. Anyway, 10,000 yen into the sea. Let's give him a big hand. Say something like, come on. Awesome. Hello. So as he said, I'm flipper. This is my talk, 10,000 yen into the sea. Essentially, I mean, just to start with, can I show a hands who enjoys filling up their gas tank? Yeah, I'm not a big fan of it either. Actually, I spent four years commuting to and from my community college. Four years, two year program. I had other things to do. So it was a 45 minute drive each way. So I pretty much ended up putting about as much money into my tank as I saved by living in my parent's basement. So all the benefits of living in my parent's basement with none of the cost savings. So that was kind of an interesting experience. And the reason why this is relevant is shortly after college, I saw underwater gliders and they kind of blew me away because when you see the typical range and duration of these things missions, it's pretty incredible. Around 3,000 kilometers on a single battery pack charge. And I work with electric vehicles professionally, partially as a consequence of this project. And I got to say, if you can show me a Nissan Leaf that can go 3,000 kilometers, I'll be pretty impressed. One of my coworkers says it's all about the drive cycle. So as I said, I'm flipper and this is kind of why I do electric vehicles professionally. They're ground vehicles here underwater. I keep on trying to talk my boss and let me turn one of our vehicles into a submarine but so far, no such luck. So, you know, I'm finished with my education and not much in the way of job options at the time. Kind of dead-end jobs and I'm killing time in the bathroom because I didn't really like my job. Reading the Oregonian and I see an article on Oregon State University's underwater glider program. And, you know, they're talking about how they work. They show a little cutaway diagram and I'm kind of blown away. It's all like, wait, wait, wait. Like how much do these cost? I could do that. You know, $100 tops. So that's where the $10,000 comes from is at one point in history that was about $100. A little bit of Jules Verne's too. So in order to build an underwater glider for $100, you kind of have to be an engineer or hacker, one of the two. I definitely wasn't an engineer so I guess that's why I'm here at DEF CON with you guys. So, you know, how do you design an underwater glider? You have to learn how to design an underwater glider. So it was really the start of an education, you know, self-taught in design and manufacture of underwater vehicles. So what I did was I was studying machine tool technology at the time, manufacturing engineering type stuff, eventually got a transfer degree. And so, yeah, it was a great vehicle to actually learn and gave a really good incentive to, you know, study STEM subject matter and ultimately transitioned into an interest in engineering transfer degree. So what is an underwater glider? Normal underwater vehicles propel themselves to the water using a propeller, pretty straightforward. There's no propeller on an underwater glider, generally speaking. They use something similar to a fish's swim ladder to change buoyancy in the water and as they float to the surface, they have wings on them. Does this thing work? Apparently not. So, wings. And those actually help transfer the change in altitude into forward movement. And so, the efficiency of the vehicle is going to be determined by a couple things. First of all, the efficiency of your fish bladder buoyancy engine. Your drag, big factor is your drag. And then also kind of related to drag is your glide ratio. How many feet forward you move through the water for every foot you lose or gain in altitude. One interesting thing of underwater vehicles is they spend about half the time flying upside down because, you know, your gravity vector flips its head when you are going against the water column or going down with it. So, yeah, there are autonomous underwater vehicles that can travel long distances and have battery power. So, history, you know, it all started back in, you know, 80s or something. I wasn't even born yet so it doesn't really matter. Very egocentric view of the universe. So, they had these things called Argos floats and they are essentially, you know, a coffee can with a big linear motor powered syringe and they go down through the water column and they collect sensor data and then when they had enough data they would float back to the surface, you know, satellite mode them, phone home and then they do it all over again. And based on my understanding of how things went down, one person was like, well, these things are really cool, you know, we are getting really good data. We are not having to send people out in boats, you know, $40,000 a day. But the problem is we can't actually control where they go. They are kind of like hot air balloons. So, it was like, what if we strap wings on them? And underwater gliders were born. Henry Stommel was one of the people who wrote some kind of pioneering articles on the potential applications of these things. And what you see before you today between the Scarlet Knight, the Slocum, the Spray, it's become a very popular vehicle class simply because of the range you can cover for the amount of energy you have to store. So, the Scarlet Knight is one of the record holders. It was put together by Rutgers University and it was essentially a Slocum glider that had been, you know, loaded down with extra battery mass and stretched out a little bit. It uses lithium CSC cells, is my understanding, which is kind of impressive because the high-test peroxide rocket fuel you see in the movie Moonraker, as far as I can actually, has lower energy density. So, those are pretty impressive batteries, although also fairly expensive. That's not what I ended up using. So, I don't know if this is the correct way to design underwater glider, but, you know, after going through, you know, 10, 20 designs in my head before even trying to build the first draft, this is kind of what I settled on as the proper procedure. Maybe somebody can correct me if I'm wrong, but you don't really know how you can package your components until you know what your components are. And buoyancy engine being one of the key elements is going to determine the efficiency. You really have to start with that. Energy storage system is going to be dictated by the energy requirement inside of your buoyancy and then, you know, hold design. It's pretty straightforward process. Very few moving parts. So, eventually I did, you know, I'm not a very decisive person, but eventually I did, you know, come to a conclusion on how I wanted to build one of these things. And that was with a phase change material. There's another vehicle out there that uses PCMs to propel itself through the water. It's called the Slokum thermal. And I'm not doing that because it looked really expensive. I read some NASA tech briefs talking about that concept. And I think it was like in Deccane, the alkane they used. And really expensive per ounce. Wasn't really on the table. My goal going into this was, remember, I said I could do this for $100. If I'm spending $200 on my phase change material, I'm kind of already blown out. So these were the design requirements I went into it with. I wanted the entry to be low because even though I had access to a milling machine in a lathe, not everybody does. So I wanted, you know, all of you to be able to take your DEF CON CD, take the solid models that are on there and go home and build one of these yourself. And then, you know, range of efficiency, you're not going to take a two order of magnitude reduction in cost without, you know, taking some hits on range, efficiency, performance. So it was kind of a best effort basis. I'm pretty optimistic. I've got a fairly large battery pack compared to the current consumption I'm looking at. So we'll see. Here's one of the earlier efforts I made into actually trying to design for manufacture. That's a Harbor Freight air compressor being used to index several syringes. And this design actually served as a lobe of inspiration for a hack I had to make towards the end of this project. Overall, the check valves involved were kind of a prohibitive feature that just disillusioned me with this concept. So, considered a lot of things, I struck out electric motors, linear actuators pretty early on in the process because, you know, at the time, you know, the milling machine were pretty much, you know, a requirement to make those happen. The weight of using an off the shelf linear actuator was pretty massive. You'd end up with like a scuba tank pressure housing and that's no fun. So wave and solar power, interesting concepts. I'd like to explore them a little bit, especially for one concept I might mention at the end. But overall hydraulic pumps and phase change materials kind of showed out to me as the best choices available. So paraffin wax expands 10% when it melts-ish. And it's got a very high specific heat. So when it does melt, it will stay liquid for a very long time. So I was looking at using soldering irons as a resistive load to actually melt the wax. And this is just kind of a breakdown comparison of various energy densities I was looking at for kind of guiding my decision on how to build the buoyancy engine. And when I first started on this project, there really wasn't much in the way available of low cost inertial navigation. You had the multi-wee project, which I thought was pretty genius. They took a nunchuck and a motion plus from a Wii game console and they actually made a 6-degree freedom IMU out of it. Welcome to the future. This is really cool. This is a $33 board available from Hobbyking. And I can't imagine they have more than $5 of profit margin built into that. You get a really cutting edge chip on there called the MPU 6050 or 6000, one of the two depending on if it's SPI or ITC. But the point is it's got a built-in magnetometer and so it can do complete 9-degree freedom sensor fusion, which is the ability to distinguish between gravity and linear movement through space. And when you're trying to actually integrate your inertial data, you'll run into problems unless you have some pretty good math background or a fantastic product like this behind you. That's the 3DR Robotics GPS chip. It was available. And it's actually buried in the nose cone of my vehicle right now, coated in a nice thick goop of RTV compound. Hole design was kind of fun. I spent most of the past year working on that as a specific aspect because it ultimately guided the production of the rest of the vehicle. Once I knew what I was packaging, I had to actually wrap it up into some sort of fluid dynamic hole form. And so based on the research I had, I'd heard some interesting things about 30 to 1 glide ratios with something called a NACA 004, which is pretty much a NACA 4-digit series 0030. But based on the simulations I did using a program called Profili 2, marketed at RC plane design, its main claim to fame was it didn't stall out at high angles of attack, whereas the black line has one of the sharpest peaks on there. So NACA 009 or 0009 was kind of out of the question too. So kind of middle of the road choice of the symmetric airfoils that were well understood at the time. Pretty common options are NACA 0015-ish. So I think my wing root is NACA 0015. And wing tip is NACA 002. And what that does is hopefully like the Rutan Long Easy, if you end up stalling out, the wing root stalls before the wing tips and that will cause the pitch to self-correct. Fingers crossed on that. Not a lot of testing in that regard. So first concept, I took a polycarbonate tube, a wax motor used to control a dishwasher latch, high force, high latency, low efficiency unfortunately as I found out later. And oh no, I'm not sure if I submitted my CFP at this point but I was kind of sweating at that time because I'm apparently really, really bad at fiberglass. Who knew? The original idea was that I would be using hot wire foam cutting techniques to actually generate the whole form and then lay fiberglass over it and as you can see from this picture, that wasn't going so hot. So not as easy as it looked on YouTube. Was not going to hit my deadline at that rate. So throw money at the problem. I've generally found that when time is of the essence, money can generally buy you time back. So I bought a 3D printer. I really am happy I made that decision. 3D printers are really cool. One of the design requirements, being able to build this thing in my underwear, check. So similar design, same whole form but now broken into smaller chunks to help with the print volume and also trying to minimize the overhang of the printed parts. Support material is an option and one of the largest prints on there actually was using support material but one month turnaround time, you really can't argue with that. And I knew 3D printing could really help expedite the design process and getting you through multiple iterations but until I had experienced it firsthand, kind of saving my bacon on getting improved concept out the door and second, third revision, whatever, I was incredibly impressed with the value. That 3D printer I showed was a Rostock Max. It's a Delta Bot style design and they are one of the coolest to look at when they're coming. Cartesian bots a little bit lame in my opinion. And that's the robot you see in front of you. So $100 price target, $31 a kilogram for my plastic, that could be cheaper but let's try and be generous just to make sure I don't underestimate. So $21 in plastic. So if you throw a significant amount of capital investment at the prospect of building projection molding tooling then that could come down significantly. Remaining bill of material was actually published to the DVD if I remember correctly and I mentioned there may have been some hiccups along the road. This bill of material is definitely not accurate to the $0.30 mark because the phase change material concept ended up working out to not just moderately inefficient to virtually unworkable at least with the energy storage system I selected. If you need your robot to go to the bottom of the Maryass trench the fact that it's a solid to liquid phase change as opposed to expansion and contraction of a gas really working to your advantage. But if you're going for range and you don't particularly want to be dragging bottom with seaweed, trying to get 3,000 meters depth with that process probably not the most efficient use of battery storage. So I think it was early May when I realized, wow, I've got a 200 volt pack or whatever and it's browning out at 100 milliamps,.1 amps. I knew that coin cells weren't exactly like lithium polymer or RC plane batteries but I was a little bit blown away. So I needed a Plan B or Plan C I guess. So what I came up with was something a little bit more conventional, trying to avoid too many experimental wild concepts and one vehicle build can be a lifesaver. So I went to the tried and true electric motor linear actuator because if you remember at the time my perception was those weren't really an option because people wouldn't have access to a lathe and mill. But with a 3D printer that potentially changes. So I ended up using commercial off the shelf McMaster car parts to build the assembly which you can see in white on the actual robot now. So the only change between what's on your DVD and what actually is here in front of you is the white assembly. Everything else I was able to recycle between designs. So modular design is a good thing I guess. The gray pipe was a really good choice. Sorry about that. The gray pipe was a really good choice because it allowed for routing of the wiring and ultimately acted as kind of a skeleton or a backbone for the entire vehicle. So what I learned from that process is 3D printing is awesome and the great thing is when you're actually done with it you don't have to go through an entire twisted new process to design 3D printed or injection molded parts. You're practically already there when you have a working prototype. What I learned through the process I feel like I actually hit a pretty good balance between fail early, fail often and not making stupid mistakes for lack of planning. I didn't build anything before I had complete solid model data and that's really valuable when you're trying to avoid these last minute crazed runs to Home Depot, West Marine, AutoZone, whatever it is. If you have a complete build of materials before you make the first part you know exactly what's going into the thing and you don't find yourself running into these issues where parts are colliding with each other. So and then it was also extremely difficult to quantify whether or not a design decision was a good or a bad one such as the wax motor until actually trying it. So it was a design decision tradeoff to not use so much simulation and I was pretty happy with how that went because you can simulate the daylights out of a bad idea and then find out you wasted last year doing you know, F.E.A. or CFD on broken design and then it's all wasted so prototypes can illuminate things that you otherwise wouldn't be aware of. So I did this entire thing out of pocket. No grants or funding agencies and I actually really like that because I'm accountable to myself and I don't have anybody breathing down my neck forcing me to chase sunk costs or make bad decisions because oh, I need to save face over that $1,000 I wasted on wax motors. On the other hand, I gave pretty much the profit of the design away for free on the DVD this year. I've probably spent around 15 grand on the project over the past decade and so I would consider it a dubious appropriation of my retirement savings. But you know, that was the mission from the start. I want people to be able to build these themselves and kind of empower themselves to deliver sensors, communications devices and payloads to remote destinations where traditionally it would be prohibitively expensive at you know, tens of thousands of dollars per vehicle and how that's possible is if your price is low enough, you can consider it disposable and you don't have to pay somebody 40 grand to go out in the water and change the batteries. So we'll see ultimately if you build it, they will come and if it's a good idea, hopefully people will say hey, maybe we should build some of these. So where to go from here? I didn't have an opportunity to test max depth because I only had one prototype as of two weeks ago and I didn't really want to lose it out in the ocean scuba diving. Like I guess I could have like tried to put a dog collar on it and you know, walked it like with a leash but overall it's disposable after my talk is over. But thing took over you know, 100 hours to print and actually that guy right there put in a significant amount of labor helping getting this thing ready for you guys' eyes. Small applause for him if you're willing. Thanks guys. So in terms of trimming vehicle, I can say with high degree of certainty this thing is very positively buoyant. Traditional buoyancy foam, polyurethane or epoxy and glass micro balloons. High crush depth, kind of unnecessary spacing is how I designed the vehicle with syringes. But overall a good choice. So generally speaking epoxy or urethane, I chose paraffin wax. It's low cost and over half the dollar per pound of buoyancy. I was seeing was either epoxy or polyurethane. So paraffin wax is like $4 a pound. So very positively buoyant. Every empty cavity in that entire thing has specific gravity about.5. So it's really just a matter of how you distribute your lead and batteries at this point to make sure that when the buoyancy engine is in a neutral position it's sitting about horizontal. Because when the vehicle goes buoyant, the center of buoyancy moves forward on the vehicle and it pitches towards the surface and the GPS chip starts rising up to its daylight. And when it goes negatively buoyant the opposite happens. So if you're a neutral buoyancy you should be sitting around level in the water. And it's really just a matter of adding weight and removing buoyancy foam as necessary to achieve that. I'm looking at around 40 to 50 milliliters of displacement change. So it's unknown at this time what the vehicle's velocity through the water is. The more buoyant it is the faster it's going to pop to the surface like a cork. And your speed through the water is going to determine what the Reynolds number is and that guides things like what airfoil you select. But first draft, I'd call it an alpha stage design and openglider.com is where I'm going to be adding future revisions. The one on your CD is rev 0.1 and rev 0.2 will be on openglider.com tonight and that will have the new white syringe based assembly. So yeah. In terms of research that went into this, this guy named Bruce Carmichael was one of the pioneers of the airfoil you see before you. It's called the X35 and originally it was known as the dolphin. But if I understand correctly they ran the dolphin through genetic algorithm and ultimately the citation, shaping of axiometric bodies for minimum drag, that one I think was where I was able to find the coordinates for this design. It does bear some resemblance to some other vehicles on the market and that shouldn't be too surprising seeing as far as I can tell we did use the same curve, rotate around its axis to generate the main body. Otherwise the NACA 4 digit series, pretty common equation and I threw something in here that I found really fascinating. It's the geometry of a blended wing body morphing wing and that was the idea that you could actually design an entire vehicle around variables and equations. So you can change something like a static wing sweep from 30 degrees to 15 to 25 degrees and rather than having a lot of hard engineering labor going into remaking the entire design, it just regenerates itself. So very early on in the process I was trying to stick to that concept and I was pretty pleased. I would change the variable from NACA 4 digit, 002 to NACA 005, kind of crazy and hit rebuild and the model would regenerate itself with very little labor on my part. One thing I'd like to explore is potentially even doing a genetic algorithm around that concept to optimize for parameters like speed through the water column and lift to dry ratio. So that's pretty much how I got here. The X35 took me like six months to a year to even find. I had no idea where people were getting this curve from but I saw it in several places. Ultimately it was just a mad Google foo that was able to illuminate the coordinates to build this thing. In terms of other information on how to build an underwater vehicle, I was going to joke every story, Ciro has a favorite weapon, Brock Samson's Bowie knife, Will Smith's little cricket and flippers hot glue gun. When you're trying to waterproof stuff, I've tried a lot of things, conformal coat, epoxy potting, pressure housings and overall even paraffin wax actually. It's not going to do very good in the Caribbean where the water gets damn near 80 degrees Celsius. It does a pretty good job because when you pot your electronics in epoxy it's very difficult to actually repair them or repair them if something blows up. But when you're using paraffin wax, the 80 degree C melting temperature is actually below the rated temperature for most electronics so if you decide you want to change something about them and I've had to, you can just use a hot air gun or boiling water to rescue your electronics. That said, from a durability standpoint, paraffin wax, even if you anneal it with a little bit of mineral oil, not the most durable thing ever. So ultimately hot glue has been my favorite approach to water proofing. If you need something a little bit lower, viscossi, get down in the English muffin nooks and crannies, then they make low viscossi silicone RTV. The acetic acid can potentially corrode your electrical contacts but we're talking about disposable vehicles here. It doesn't have to last three years. I've got electronic speed controllers. I potted for the RoboSpub competition two years ago that still work. And that was just plain Jane AutoZone RTV compound. And so pretty much every beast of electronics on that thing are just either code and hot glue or RTV compound. And it's a pretty easy, low cost way of waterproofing electronics. So I guess at this time it would be a good way to go for questions. Yeah, that's a good question. So one of the problems with underwater vehicles that make some kind of interesting to me is unlike, you know, Mars rovers, you know, easy environment, you know, aerial vehicles, a bunch of light weights, you know, these people, they're so spoiled. With underwater vehicles, you don't get to talk to your robot after you let it go until it comes back to the surface at which point. You know, it's kind of a surface vehicle until it goes back underwater snorkel depth style. So no radio frequency communication so it has to be pretty much all autonomous. And the source code I used with the IMU to actually, it's called a Haversine formula. It finds your current GPS coordinates and your destination GPS coordinates and gives you a bearing. And the distance you need to go to get there. So it's pretty much a line follower robot. That's what makes underwater gliders potentially so successful is unlike, you know, mind detecting robots or, you know, anti-frogman stuff. They have a pretty basic mission which is go from point A to point B. So object avoidance potentially with sonar. But, you know, suddenly when your payload starts getting into the, you know, high dollar sonar stuff, it stops being so disposable. At that point, you know, my 3D printed open glider may not be the best choice of vehicles. So testing has been kind of an iterative process. I've learned every time I stuck in the bathtub. Early on, it was pretty much with a small car battery and some red and green wire hanging out of the thing. Underwater vehicles can actually be communicated with remotely using something called a tether. At which point, they're no longer AUVs or UUVs or ROVs, remotely operated vehicles. And I had two years of tethered vehicle competitions that kind of prepared me for working with the unmanned side of things. And it's a pretty good way to go. So for testing, bathtubs are surprisingly effective. You have them in hotel rooms. And yeah, generally speaking, the main thing you're going to be testing is either what it decides to do when it gets in the water or how it sits in the water when you put it in there. And both of those things don't require a big swimming pool. Also, a lot less terrified, shrieking swimmers running away from the evil robot. It's the second one. So I don't really rely on pressure housings as a rule. I had to depend on some amount of air cavity for the design fix. And it's the most conventional thing about this design was you've got little linear actuators driven by 3 volt gear motors. Actually, I think I have one. Anybody want one? I know audiences love things being thrown at them. Not you, Mark. Oh, hey, speaking of that, anybody want a flight controller? $33, give me. Remember, two is one, one is none. So bring spare parts. Sorry. I throw like a roboticist. More questions. Oh, good question. So when you have like a tank light when you're scuba diving, you can actually make them water active. They're only wasting battery life when you're in the water and you're trying not to lose your dive buddy. In my case, I don't have anything smart like that on my robot. So those wires allow me to disconnect the power supply from the actual microcontroller. Because once I plug it in, it just goes and it will keep going until I unplug it. Oh, really good question. I was at an ROV conference and this guy who is like super salty, you know, had been out in the field for a long time, told me a really cool trick. You go to like Harbor Freight and they'll sell these heat shrink packages, marine heat shrink. And it's just heat shrink that's been lined with hot glue. And you don't need to use special heat shrink or wire crimps. You can just take your wire splice, coat it in hot glue and then run heat shrink over it. And when you melt the heat shrink or shrink the heat shrink, it will melt the hot glue again and pull all the air bubbles out. Great question. How does it work? Oh, yeah, no, I totally glossed over on that. Really good point. So I don't actually have one buoyancy engine. I have four. And generally speaking, you might have them towards the top of the vehicle. I have them low on the center of gravity because I had two places I could put them top or bottom. And the top was all being used by syntactic foam or syntactic wax buoyancy sand. And since that was more buoyant than the buoyancy engines themselves, I have them down low. And so I have broken the cross section of my vehicle into eight little slices of pie. The top four are full of buoyancy sand and the bottom four, there are two pairs. So when you trigger the two on the left, your left side is going to be more buoyant than your right side. So one wing will lift up. And likewise, if you use the two on the right, it's going to change the attitude the other way. So this is one unique thing about my vehicle design. Traditionally, you actually move your battery mass, whereas I'm just having four times the buoyancy engines that are typical. And finally, you know, if you change buoyancy on the bottom two, then you'll just go straight. So you have to use your inertial system for just independent operations. How often do you have to go to the surface to get GPS fixed to? How accurate is the GPS? Good question. So I can say with pretty good confidence that my inertial navigation system is not high enough quality to the U.S. munitions list grade. So that's totally a relief. Yeah, these are hobby components. So video game grade, in terms of actual like integration of my velocity or whatever to get my position, I don't really do any of that. I've been working a little bit in my free time with trying to use fetal Doppler monitors, which measure the velocity of fluid through baby's blood to, you know, let you listen to the kid's heartbeat, kind of cool. And they're essentially homodines, ultrasonic homodines. And I've been looking at potentially getting some velocity information from that. But pretty much I figure out which direction I want to go. And it's a line follower bot. It says, I know I need to go either left, right, or straight. And it dives and it comes to the surface and it says, oh, wow, I missed my target. But okay, now I need to go. You know, it doesn't really look backwards, only forwards. Good question. Thanks. Oh, bathtub depths. Okay, originally, I had a washing machine wax motor from like a, I think it was a whirlpool Neptune or something. And that one didn't get a lot of mileage simply because the fiberglass thing went so terrible. Just didn't really work into the 3D printed picture. So then I moved to a soldering iron based design. I was using silicone high temperature rubber hose and soldering irons and filling them with wax. And I was browning out my power supply, even though I only needed about 100 milliamps, it was still too much. And it would have been a pretty big design tear up to change my batteries. So I just changed my buoyancy engine. Questions? Really good question. So in the original solid model I designed around, I actually made a solid model of the PX4 autopilot from DIY drones or PX. I don't really know what that relationship is, but it's a really good board. It uses a publisher subscriber system. And so right now I'm only using the IMU, the micro-wee board for everything. And one of the issues with that decision is it is so flash memory constrained that you can only just barely compile the source code included on your DVD. In fact, if you try and use Arduino 1.5.2 to do so, it's not going to work for you. You have to use Arduino 1.0.4 if I remember correctly. And that will work. So I didn't remember to put that in the slides and I'm glad you brought it up. So there is a reasonable amount of space, about one quarter of the size of an Altoid 10, maybe half the size of an Altoid 10 for a supervisory controller to supplement the IMU. The IMU is broadcasting yaw, pitch, roll information that's already been fused. So it's pretty much relative to your world body or world coordinate system. And it's really nice because it's publishing it on the serial port and it's also telling you time's up. All right. Any further questions or wanting to see the robot in person, touch and feel, I'll meet you guys out in the hallway, I guess. Thank you.
electric vehicles professionally, partially as a be an engineer or hacker, one of the two. I have to learn how to design an underwater glider. the efficiency of the vehicle is going to be long distances and have battery power. So, can package your components until you know what two order of magnitude reduction in cost without, with like a scuba tank pressure housing and when I first started on this project, there expansion and contraction of a gas really working also extremely difficult to quantify whether or such as the wax motor until actually trying it. devices and payloads to remote destinations where really want to lose it out in the ocean scuba removing buoyancy foam as necessary to achieve time what the vehicle's velocity through the that will have the new white syringe based six months to a year to even find. I had no idea RoboSpub competition two years ago that still vehicles. So testing has been kind of an you know, had been out in the field for a long trying to use fetal Doppler monitors, which there is a reasonable amount of space, about one