We’re going to circumnavigate the world with a droneship
Andrew’s next hobby project is here.
The goal is to complete an around the world ocean trip, autonomously navigating 25,000 miles over the course of one year. The droneship will be streaming to X live via Starlink through the whole journey.
Will it work? Who knows. Do we have a specific goal? Not really. We're just here for the grand adventure and the inevitable memes.Projectbob.xyz
Andrew’s next hobby project is here.
The goal is to complete an around the world ocean trip, autonomously navigating 25,000 miles over the course of one year. The droneship will be streaming to X live via Starlink through the whole journey.
Will it work? Who knows. Do we have a specific goal? Not really. We're just here for the grand adventure and the inevitable memes.Projectbob.xyz
Why??
Insatiable curiosity, or just poor impulse control? Honestly, building stuff is fun. I like to wade into the deep end of subjects I’m not qualified for and come out the other side with a story and a new skill.
A lot of things inspired this idea. For my day job, I build spacecraft + satellites which orbit the earth. When I watched our reentry footage (), it was a conscious altering thing to watch the camera film all the way from orbit to sitting on the desert floor. It just puts things in perspective, that we live on this giant but ultimately tiny blue marble. To have hardware in my hand that went on a journey around the entire control volume that we as humans occupy, that’s special.
Wired had a hilarious quote in their LK99 interview, which I have come to like. “McCalip preferred not to dwell, but instead chose to focus on what he had set out to do: making the thing”.
So that’s what we’re going to do. We’re going to build the thing.
I’m reminded of that intro to the movie Primer.
“…They took from their surroundings what was needed... and made of it something more…”
Insatiable curiosity, or just poor impulse control? Honestly, building stuff is fun. I like to wade into the deep end of subjects I’m not qualified for and come out the other side with a story and a new skill.
A lot of things inspired this idea. For my day job, I build spacecraft + satellites which orbit the earth. When I watched our reentry footage (), it was a conscious altering thing to watch the camera film all the way from orbit to sitting on the desert floor. It just puts things in perspective, that we live on this giant but ultimately tiny blue marble. To have hardware in my hand that went on a journey around the entire control volume that we as humans occupy, that’s special.
Wired had a hilarious quote in their LK99 interview, which I have come to like. “McCalip preferred not to dwell, but instead chose to focus on what he had set out to do: making the thing”.
So that’s what we’re going to do. We’re going to build the thing.
I’m reminded of that intro to the movie Primer.
“…They took from their surroundings what was needed... and made of it something more…”
A year ago
A year ago to the day, and coincidently my birthday, the LK99 madness kicked off with this tweet.
The entire saga was an absolute blast. We did it live and in public. The outpouring of support was unreal. From national labs to twitter anons, we were all just peers. For a moment, it looked like nature had gifted us with something extraordinary.
I remember at one point, we were one of the top Twitch streams in the world, with a webcam pointed at the door of a furnace. It was 100% on the fly improvisation as problems came up. From trying to buy red phosphorus, to building our own vacuum ampules, we just live tweeted the entire process as it was happening. It was a meme and coffee fueled rager of a week, where no one slept, and the entire world watched.
What I took away from this is that people love seeing real-life engineering adventures unfold live. It tapped into a deep-seated desire for authentic stories, rather than crafted Hollywood ones.
The webcam incident stuck with me, and a few weeks ago someone happened to mention it, and that got me thinking. What is something dramatic that would unfold over a long period of time, that the internet could get excited about? What’s a journey we could go on, where no one knows how it will end? Could we do something that no one has ever done, in our nights and weekends, for pocket change?
A year ago to the day, and coincidently my birthday, the LK99 madness kicked off with this tweet.
The entire saga was an absolute blast. We did it live and in public. The outpouring of support was unreal. From national labs to twitter anons, we were all just peers. For a moment, it looked like nature had gifted us with something extraordinary.
I remember at one point, we were one of the top Twitch streams in the world, with a webcam pointed at the door of a furnace. It was 100% on the fly improvisation as problems came up. From trying to buy red phosphorus, to building our own vacuum ampules, we just live tweeted the entire process as it was happening. It was a meme and coffee fueled rager of a week, where no one slept, and the entire world watched.
What I took away from this is that people love seeing real-life engineering adventures unfold live. It tapped into a deep-seated desire for authentic stories, rather than crafted Hollywood ones.
The webcam incident stuck with me, and a few weeks ago someone happened to mention it, and that got me thinking. What is something dramatic that would unfold over a long period of time, that the internet could get excited about? What’s a journey we could go on, where no one knows how it will end? Could we do something that no one has ever done, in our nights and weekends, for pocket change?
Trawling for likes:
I can’t believe how lucky we are on the timing. Starlink Mini just hit the market and is the enabling tech of this whole project. Of course, we’re going to livestream from this thing 24/7. The home base for this project is X (the everything app). We’ll also put updates up on the website. But X is where it’s at. @elonmusk has no idea what I’m planning to do with Starlink, and SpaceX isn’t sponsoring this in any way, though I may need to call in some favors to get my dish enabled for ocean roaming?
On the site, we’ll set up a live video stream from the Gopro, alongside the full set of telemetry channels. The route will be published as well, full transparency.
Honestly, the absolute best case scenario is if it gets picked up by pirates that were monitoring the boat’s Twitter account while the world watches live. Peak entertainment.
I can’t believe how lucky we are on the timing. Starlink Mini just hit the market and is the enabling tech of this whole project. Of course, we’re going to livestream from this thing 24/7. The home base for this project is X (the everything app). We’ll also put updates up on the website. But X is where it’s at. @elonmusk has no idea what I’m planning to do with Starlink, and SpaceX isn’t sponsoring this in any way, though I may need to call in some favors to get my dish enabled for ocean roaming?
On the site, we’ll set up a live video stream from the Gopro, alongside the full set of telemetry channels. The route will be published as well, full transparency.
Honestly, the absolute best case scenario is if it gets picked up by pirates that were monitoring the boat’s Twitter account while the world watches live. Peak entertainment.
The boat. Why Bob?
It’s a reference to the Bobiverse, a fantastic scifi series where a von neumann probe is loaded with a human consciousness and sent out into the universe.
It’s also a pun.
It’s a reference to the Bobiverse, a fantastic scifi series where a von neumann probe is loaded with a human consciousness and sent out into the universe.
It’s also a pun.
The team:
My lab partner in crime is back for this one. PhD astrophysics sailor who spent a year in the Arctic. @lepsthomas
Cracked PLC test engineer @Jeff15603296 is doing all things software for this project. We’ll be hijacking his NI-killer PLC infrastructure for the backend and server side stuff.
@laskerer is going to make magic happen on the bizdev front. This idea don't have a business component, so I'm interested to see how he does it 😂
Some of these people don’t even have a Twitter presence, that’s how locked in they are. I’ll do my best to drag them online.
•Sam Knoles
•Marat Kulakhmetov
•Jordan Croom
My lab partner in crime is back for this one. PhD astrophysics sailor who spent a year in the Arctic. @lepsthomas
Cracked PLC test engineer @Jeff15603296 is doing all things software for this project. We’ll be hijacking his NI-killer PLC infrastructure for the backend and server side stuff.
@laskerer is going to make magic happen on the bizdev front. This idea don't have a business component, so I'm interested to see how he does it 😂
Some of these people don’t even have a Twitter presence, that’s how locked in they are. I’ll do my best to drag them online.
•Sam Knoles
•Marat Kulakhmetov
•Jordan Croom
Project Bob: Day 1
Let’s take stock of where everything is right now. We’ve been working for a few weeks to do the sanity checks, and we’re looking okay so far. It’s not physically impossible.
Excel:
•Energy budget feels within 25%
•Mass budget has been worked over is probably within 10%
•Prop budget is largest uncertainty. Need to conduct propeller experiments to downselect a diameter and pitch.
•Hull drag numbers anchored by DELFTship software.
CAD:
•Reasonably mature.
•Center of gravity and buoyancy in reasonable locations with all mass props accounted for
Hull:
•A twitter anon has incredibly kindly volunteered their giant CNC 5 axis.
•Goal is to buy foam this week and finalize geometry in ~10 days.
•Cutting and fiberglass in ~3 weeks
Propulsion:
•Not super mature.
•Keel is roughed in.
•Down selected to a prop drive after the failure of the magnetic coupler approach
•17-4 SS helical coupler candidate bought, needs testing. Can it survive 500mil cycles at 10deg off axis
Rudder:
•Basic rear mounted skeg/rudder chosen.
•Unsure about sizing. Our turning radius is way less critical than most other small boats.
Solar:
•Sunpower cells selected as array type
•MPPT need a final decision. Thinking Victron?
Batteries:
•18650s, but no brand decided. A kind twitter anon has donated 100 cells already. Undecided if these will be for development or the real flight pack.
•Packs need to be spot welded and assembled. Might get some help from the gundo boys.
PCB:
•Architecture for the deadman switch has been roughed in. More on that later. This is super important.
•Schematic design this week.
Software:
•Docker stack is being borrowed from previous applications. It has tens of thousands of hours of runtime and is fairly battle hardened.
•Grafana / InfluxDB / Telegraf contains in the process of being set up.
•Haven’t got my hands on a Starlink Mini yet to test what networking will be like.
Administrative:
•Website set up. This is mainly for the blog. We found out last time in LK99 that its hard to tell a story in hundreds of chronological twitter posts. I’ll mirror all content there.
•Givebutter donation site setup. This is going to cause a tax headache if donations actually happen.
•Youtube live account set up. We also found out the hard way in LK99 that you need to do this far in advance. I still need to work on the software stack to handle the Starlink video retrieval scripts. We’ll need to automate this in a server and continually stream the chunks as we bring them back every hour.
Let’s take stock of where everything is right now. We’ve been working for a few weeks to do the sanity checks, and we’re looking okay so far. It’s not physically impossible.
Excel:
•Energy budget feels within 25%
•Mass budget has been worked over is probably within 10%
•Prop budget is largest uncertainty. Need to conduct propeller experiments to downselect a diameter and pitch.
•Hull drag numbers anchored by DELFTship software.
CAD:
•Reasonably mature.
•Center of gravity and buoyancy in reasonable locations with all mass props accounted for
Hull:
•A twitter anon has incredibly kindly volunteered their giant CNC 5 axis.
•Goal is to buy foam this week and finalize geometry in ~10 days.
•Cutting and fiberglass in ~3 weeks
Propulsion:
•Not super mature.
•Keel is roughed in.
•Down selected to a prop drive after the failure of the magnetic coupler approach
•17-4 SS helical coupler candidate bought, needs testing. Can it survive 500mil cycles at 10deg off axis
Rudder:
•Basic rear mounted skeg/rudder chosen.
•Unsure about sizing. Our turning radius is way less critical than most other small boats.
Solar:
•Sunpower cells selected as array type
•MPPT need a final decision. Thinking Victron?
Batteries:
•18650s, but no brand decided. A kind twitter anon has donated 100 cells already. Undecided if these will be for development or the real flight pack.
•Packs need to be spot welded and assembled. Might get some help from the gundo boys.
PCB:
•Architecture for the deadman switch has been roughed in. More on that later. This is super important.
•Schematic design this week.
Software:
•Docker stack is being borrowed from previous applications. It has tens of thousands of hours of runtime and is fairly battle hardened.
•Grafana / InfluxDB / Telegraf contains in the process of being set up.
•Haven’t got my hands on a Starlink Mini yet to test what networking will be like.
Administrative:
•Website set up. This is mainly for the blog. We found out last time in LK99 that its hard to tell a story in hundreds of chronological twitter posts. I’ll mirror all content there.
•Givebutter donation site setup. This is going to cause a tax headache if donations actually happen.
•Youtube live account set up. We also found out the hard way in LK99 that you need to do this far in advance. I still need to work on the software stack to handle the Starlink video retrieval scripts. We’ll need to automate this in a server and continually stream the chunks as we bring them back every hour.
What’s this word, antipode?
To make it a true circumnavigation according to the rulebooks, you must meet the following:
Start and finish: The trip must begin and end at the same location
Direction: Travel in one general direction, preferably continuously
Distance: Travel a distance that is equal to or more than the length of the equator (24,900 miles or 40,075 kilometers)
Antipodes: Touch at least one pair of antipodes, which are two spots on opposite sides of the Earth
Equator: Cross the equator at a minimum of two points
We’re going to follow a variation of the classic clipper route. Because we’re launching out of Los Angeles, we’ll need to drive up into the Indian Ocean. See here.
As far as we can tell, no individual or non-professional group has ever accomplished an unmanned autonomous full circumnavigation. Two notable efforts were:
Saildrone circumnavigated Antarctica, but did not complete the larger journey of 25,000+ miles.
Seacharger was a brilliantly successful hobby attempt that went 6,500 miles before a rudder failure.
Our route is going to take us to some of the most extreme places in the world. The southern Arctic Ocean is legendary for its weather. I’m hoping to use live weather satellite data to perform some maneuvering around major storms. These waves of the things of nightmares.geodatos.net/en/antipodes/u…
saildrone.com/news/unmanned-…
seacharger.com
To make it a true circumnavigation according to the rulebooks, you must meet the following:
Start and finish: The trip must begin and end at the same location
Direction: Travel in one general direction, preferably continuously
Distance: Travel a distance that is equal to or more than the length of the equator (24,900 miles or 40,075 kilometers)
Antipodes: Touch at least one pair of antipodes, which are two spots on opposite sides of the Earth
Equator: Cross the equator at a minimum of two points
We’re going to follow a variation of the classic clipper route. Because we’re launching out of Los Angeles, we’ll need to drive up into the Indian Ocean. See here.
As far as we can tell, no individual or non-professional group has ever accomplished an unmanned autonomous full circumnavigation. Two notable efforts were:
Saildrone circumnavigated Antarctica, but did not complete the larger journey of 25,000+ miles.
Seacharger was a brilliantly successful hobby attempt that went 6,500 miles before a rudder failure.
Our route is going to take us to some of the most extreme places in the world. The southern Arctic Ocean is legendary for its weather. I’m hoping to use live weather satellite data to perform some maneuvering around major storms. These waves of the things of nightmares.geodatos.net/en/antipodes/u…
saildrone.com/news/unmanned-…
seacharger.com
The weather?
Our thoughts about the southern Arctic Ocean are something like this.
The roaring forties have legendarily bad weather. It has been a terrifying place to take a boat, in both ancient times and modern day.
Seeing those videos had a large effect on our design of hull for the boat. Obviously, it should be able to self-right itself even if flipped over 180deg. The construction of the hull needed to be more similar to a buoy right than a ship, with a solid interior of closed cell marine foam.
Originally a more optimized trimaran hull was desirable for solar area efficiency, Unfortunately we couldn’t settle on what an acceptable load case would be to design the top solar deck to. If you have a breaking wave hit the deck, this is a huge dynamic load of hundreds of pounds per square foot. The risk of undersizing your cantilever beams in your deck is just too scary, the risk/return doesn’t seem to close on this concept.
Our thoughts about the southern Arctic Ocean are something like this.
The roaring forties have legendarily bad weather. It has been a terrifying place to take a boat, in both ancient times and modern day.
Seeing those videos had a large effect on our design of hull for the boat. Obviously, it should be able to self-right itself even if flipped over 180deg. The construction of the hull needed to be more similar to a buoy right than a ship, with a solid interior of closed cell marine foam.
Originally a more optimized trimaran hull was desirable for solar area efficiency, Unfortunately we couldn’t settle on what an acceptable load case would be to design the top solar deck to. If you have a breaking wave hit the deck, this is a huge dynamic load of hundreds of pounds per square foot. The risk of undersizing your cantilever beams in your deck is just too scary, the risk/return doesn’t seem to close on this concept.
Budgets. What do we have to work with. Let’s do some hand calcs
Everything in engineering should start with an excel sheet. Do your rough sizing, order of magnitude estimates, sensitivity studies.
In this case, we have a few critical coefficients that everything in the project is heavily dependent on. This is a multivariable optimization problem where we’re bounded primarily by power generation and consumption.
•Watts per newton of propeller thrust.
•Watt-hour/meter^2/day of solar collection
•Newtons / meter^2 of hull drag
Let’s tackle one at a time
Everything in engineering should start with an excel sheet. Do your rough sizing, order of magnitude estimates, sensitivity studies.
In this case, we have a few critical coefficients that everything in the project is heavily dependent on. This is a multivariable optimization problem where we’re bounded primarily by power generation and consumption.
•Watts per newton of propeller thrust.
•Watt-hour/meter^2/day of solar collection
•Newtons / meter^2 of hull drag
Let’s tackle one at a time
Electrical: Power is everything:
(my favorite piece of media so far)
We’re going to have to watch every watt of consumption. If we consider our end of journey 24hr avg power output, we’re looking at 38 watts for the whole ship.
Starlink is the HUGE consumer. Average power during upload is going to be 30w. This is basically the entire propulsion budget, so we’re going to need to get this duty cycle to <10% of overall time. Burst uploading large chunks of video every 2-4hr is probably the way. Would people rather see a 5fps 1080p stream or a 480p 24fps stream?
Rudder servos need to be powered off most of the time. The average Hitec digital servo draws 1200millwatts. The strategy will be to turn on the servo at perhaps a 1% duty cycle. We’re mostly going in a straight line after all.
Gopros are very power hungry. Avg consumption looks to be around 3 watts. But if we’re not shooting video, that defeats a major point of the project. I think we’ll keep one camera powered down as a backup / diagnostic rear facing camera. Another power savings is that we’re not going to run the livestream GoPro at night. That’s a 36watt-hour savings!
ESCs are fairly efficient. I’ve chosen a Tmotor Alpha ESC with sinusoidal field oriented control. Should be one of the most efficient on the market. If you have any better suggestions, I’m all ears. Perhaps 250mw of power dissipation in the FETs.
Pis are reasonable. A 3+ in idle condition is going to draw about 1.2watts. We’ll send the secondary backup Pi into a sleep mode after the watchdog GPIO on the primary goes high.
GPS. A sparkfun gps with an I2C bus is quite low, hundreds of milliwatts.
All this needs to go into the avionic budget sheet with duty cycles. Last time I checked, we’re at 6 watts on a 24hr averaged basis.
(my favorite piece of media so far)
We’re going to have to watch every watt of consumption. If we consider our end of journey 24hr avg power output, we’re looking at 38 watts for the whole ship.
Starlink is the HUGE consumer. Average power during upload is going to be 30w. This is basically the entire propulsion budget, so we’re going to need to get this duty cycle to <10% of overall time. Burst uploading large chunks of video every 2-4hr is probably the way. Would people rather see a 5fps 1080p stream or a 480p 24fps stream?
Rudder servos need to be powered off most of the time. The average Hitec digital servo draws 1200millwatts. The strategy will be to turn on the servo at perhaps a 1% duty cycle. We’re mostly going in a straight line after all.
Gopros are very power hungry. Avg consumption looks to be around 3 watts. But if we’re not shooting video, that defeats a major point of the project. I think we’ll keep one camera powered down as a backup / diagnostic rear facing camera. Another power savings is that we’re not going to run the livestream GoPro at night. That’s a 36watt-hour savings!
ESCs are fairly efficient. I’ve chosen a Tmotor Alpha ESC with sinusoidal field oriented control. Should be one of the most efficient on the market. If you have any better suggestions, I’m all ears. Perhaps 250mw of power dissipation in the FETs.
Pis are reasonable. A 3+ in idle condition is going to draw about 1.2watts. We’ll send the secondary backup Pi into a sleep mode after the watchdog GPIO on the primary goes high.
GPS. A sparkfun gps with an I2C bus is quite low, hundreds of milliwatts.
All this needs to go into the avionic budget sheet with duty cycles. Last time I checked, we’re at 6 watts on a 24hr averaged basis.
Watts per newton of propeller thrust.
Ideally, a propeller is acting as an inclined plane, converting the motor torque to forward motion with a certain % efficiency.
The basic definition of a watt is a joule per second. A joule is the work done in displacing a body 1 meter with an opposing force of 1 Newton.
There are going to be a ton of losses everywhere in the system. Propeller slippage, bearing drag, viscous shaft losses, ohmic coil heating in the brushless motors, switching losses in the mosfets. All these things are going to stack up.
At the end of the day, we need some real world performance numbers as a starting point for our excel doc.
I simply started looking at every RC boat and AUV thruster datasheet I could find that had thrust curves. For a non optimized medium diameter 2/3/4 blade propeller with a direct drive brushless motor, I saw values at .5 newtons / watt, plus or minus about 25%. Good enough to get started.
A great benchmark was the Blue Robotics T200 thruster. This had a 480kv motor spinning a 100mm 3 blade prop. Performance was about .6 newton/watt. It’s not clear if this is a static bollard pull number or an at speed number. I suspect stationary bollard pull.
The general rule of thumb is that your efficiency will increase with the swept area of the propeller. We want as large of a diameter as practically possible, while minimizing blade thickness. The plan is to take APC airplane propellers of varying sizes and conduct real seal trials in the Marina. We’ll select the most efficient for our cruising speed, 3d scan the geometry, and CNC it from 316 stainless.
The factors we need to simultaneously optimize are the KV motor rating, battery voltage, propeller diameter, throttle percent, and desired cruising speed.
We don’t know exactly how fast we can go, but we know the general relationship. The drag force, and therefor motor power, is going to go up with the SQUARE of velocity. This ain’linear. So ideally we want to motor along 24 hours a day at the slowest possible speed while still maintaining enough velocity to make it around the world in a year. That maths to about 2.85 miles per hour (mph) or 2.48 knots. Great, we have an absolute minimum speed. We can now proceed to see what the power budget allows us to consume.
Ideally, a propeller is acting as an inclined plane, converting the motor torque to forward motion with a certain % efficiency.
The basic definition of a watt is a joule per second. A joule is the work done in displacing a body 1 meter with an opposing force of 1 Newton.
There are going to be a ton of losses everywhere in the system. Propeller slippage, bearing drag, viscous shaft losses, ohmic coil heating in the brushless motors, switching losses in the mosfets. All these things are going to stack up.
At the end of the day, we need some real world performance numbers as a starting point for our excel doc.
I simply started looking at every RC boat and AUV thruster datasheet I could find that had thrust curves. For a non optimized medium diameter 2/3/4 blade propeller with a direct drive brushless motor, I saw values at .5 newtons / watt, plus or minus about 25%. Good enough to get started.
A great benchmark was the Blue Robotics T200 thruster. This had a 480kv motor spinning a 100mm 3 blade prop. Performance was about .6 newton/watt. It’s not clear if this is a static bollard pull number or an at speed number. I suspect stationary bollard pull.
The general rule of thumb is that your efficiency will increase with the swept area of the propeller. We want as large of a diameter as practically possible, while minimizing blade thickness. The plan is to take APC airplane propellers of varying sizes and conduct real seal trials in the Marina. We’ll select the most efficient for our cruising speed, 3d scan the geometry, and CNC it from 316 stainless.
The factors we need to simultaneously optimize are the KV motor rating, battery voltage, propeller diameter, throttle percent, and desired cruising speed.
We don’t know exactly how fast we can go, but we know the general relationship. The drag force, and therefor motor power, is going to go up with the SQUARE of velocity. This ain’linear. So ideally we want to motor along 24 hours a day at the slowest possible speed while still maintaining enough velocity to make it around the world in a year. That maths to about 2.85 miles per hour (mph) or 2.48 knots. Great, we have an absolute minimum speed. We can now proceed to see what the power budget allows us to consume.
Watt-hour/meter^2/day of solar collection
Luckily this was the most straight forward exercise. We can easily bound this problem to a fairly high degree of accuracy. The amount of sunlight that hits the earth and is collected by average grade silicon PV cells is well quantified. We can simply go to get some estimates of what it would be along our path. For our simple estimates, we’ll choose 4.5 watt-hour / panel_watt/ day.
The bigger issue is efficiency knockdown factors. We need to hold some conservatism from this ideal number.
•Salt grime buildup
•Cosine losses due to panel angle error
•Cell degradation
•Possible loss of string of cells
Let’s make some wild guesses and hold some conservative margins. With all the losses stacked, we are seeing a worst case ~45watts continuous power from a 300 watt array with a 1.5m^2 deck area requirement. Great, this is a very linear relationship. We know we can easily buy premade Sunpower cell arrays in 100w increments. We like Sunpower, as they have a long history of being used by SpaceX, so they’ve got good heritage. They’re also dirt cheap, about a dollar per watt.
The entire boat exists to support this solar array. This required deck area will help drive the hull design.globalsolaratlas.info/and
Luckily this was the most straight forward exercise. We can easily bound this problem to a fairly high degree of accuracy. The amount of sunlight that hits the earth and is collected by average grade silicon PV cells is well quantified. We can simply go to get some estimates of what it would be along our path. For our simple estimates, we’ll choose 4.5 watt-hour / panel_watt/ day.
The bigger issue is efficiency knockdown factors. We need to hold some conservatism from this ideal number.
•Salt grime buildup
•Cosine losses due to panel angle error
•Cell degradation
•Possible loss of string of cells
Let’s make some wild guesses and hold some conservative margins. With all the losses stacked, we are seeing a worst case ~45watts continuous power from a 300 watt array with a 1.5m^2 deck area requirement. Great, this is a very linear relationship. We know we can easily buy premade Sunpower cell arrays in 100w increments. We like Sunpower, as they have a long history of being used by SpaceX, so they’ve got good heritage. They’re also dirt cheap, about a dollar per watt.
The entire boat exists to support this solar array. This required deck area will help drive the hull design.globalsolaratlas.info/and
Newtons / meter^2 of hull drag and what should the hull look like?
5 of us went through about a dozen hull variations in one epic session of excel and CAD.
Ultimately, we need to displace a volume of water equal to our boat's mass if we’re a displacement hull. Or we need to maintain neutral buoyancy and be nearly completely submerged.
Right now the baseline is a traditional hull with a length to beam ratio of about 25:1. This is rather extreme and is an effort to be maximally efficient. We are constrained in that we need to accommodate the solar panels on the top deck. Each panel is ~46in long, so the boat needs to be in even array integers. We settled on 300 watts, so we’re about 14ft long.
I initially had a bit of a tough time establishing ballpark drag numbers for such a low velocity. Once I got a full CAD modeI was then able to import the STL into DELFTship and have it do some basic hydrodynamic calcs. This served as a sanity check against my basic ChatGPT derived wetted area/displacement hull hand calcs. Hoping for something close to 20 newtons of drag at 4 knots.
Turns out, humanity is already fairly good at boats, and has documented this knowledge in extreme detail. A weekend of reading Practical Ship Hydrodynamics helped distill a lot of the best practices.
5 of us went through about a dozen hull variations in one epic session of excel and CAD.
Ultimately, we need to displace a volume of water equal to our boat's mass if we’re a displacement hull. Or we need to maintain neutral buoyancy and be nearly completely submerged.
Right now the baseline is a traditional hull with a length to beam ratio of about 25:1. This is rather extreme and is an effort to be maximally efficient. We are constrained in that we need to accommodate the solar panels on the top deck. Each panel is ~46in long, so the boat needs to be in even array integers. We settled on 300 watts, so we’re about 14ft long.
I initially had a bit of a tough time establishing ballpark drag numbers for such a low velocity. Once I got a full CAD modeI was then able to import the STL into DELFTship and have it do some basic hydrodynamic calcs. This served as a sanity check against my basic ChatGPT derived wetted area/displacement hull hand calcs. Hoping for something close to 20 newtons of drag at 4 knots.
Turns out, humanity is already fairly good at boats, and has documented this knowledge in extreme detail. A weekend of reading Practical Ship Hydrodynamics helped distill a lot of the best practices.
Details:
Okay, so let’s roll up all the detailed specs as they are currently. All this is subject to change.
~14ft feel long
3lb density foam. CNC milled
Fiberglass wet layup. Surfboard style
~130lb total mass
300watt solar Sunpowerarray
1800watt-hour 18650 lion battery. 6s 18p
~45w average continuous power
Starlink Mini
Iridium satellite modem
2x Gopro Hero cameras
2x redundant raspberry PIs.
Read only OS with failover images
Docker stack for OTA code upgrading
Direct drive prop (pitch unknown yet)
10deg shaft drive
2x TmotorAlpha 60a ESCs in primary/backup config
320kv Tmotor brushless motor
Custom PCB with deadman reset logic
Okay, so let’s roll up all the detailed specs as they are currently. All this is subject to change.
~14ft feel long
3lb density foam. CNC milled
Fiberglass wet layup. Surfboard style
~130lb total mass
300watt solar Sunpowerarray
1800watt-hour 18650 lion battery. 6s 18p
~45w average continuous power
Starlink Mini
Iridium satellite modem
2x Gopro Hero cameras
2x redundant raspberry PIs.
Read only OS with failover images
Docker stack for OTA code upgrading
Direct drive prop (pitch unknown yet)
10deg shaft drive
2x TmotorAlpha 60a ESCs in primary/backup config
320kv Tmotor brushless motor
Custom PCB with deadman reset logic
Ideas graveyard:
Pour one out for the things we thought about and had to pivot away from. I spent a few nights thinking longingly of the energy density of hydrocarbons. It’s just so many joules per kilogram. Ultimately we couldn’t convince ourselves that a system capable of running for 4000 hours unattended was possible with cheap COTS components.
Hydrogen fuel cell. Thought about using 6,000psi k bottles from Matheson and a PEM fuel cell. The energy storage in terms of electrical joules per kilo actually is fairly decent. The PEM cells are readily available. The real killer to this idea is the salt water contamination that happens on the PEM membrane.
Internal combustion engine. Small 2kw gasoline generator doing a fast charge every 24hr on the batteries. Basically like an old diesel/electric submarine. The joules per kilo of gasoline is SO GOOD. Hydrocarbons are a hell of a drug. I really wanted this option o work. It does require a snorkel and good filtering on the incoming air. The main issue was the lack of a small ~2000w generator with electric start. There are some sketchy Chinese units, but I didn’t see anything that really fit the bill nicely. This would accumulate about 200 hours of runtime, which isn’t terrible. The volume of gasoline would easily fit in bladders in our current hull.
TriMaran hull. They look amazing, and it’s more efficient structurally for a given surface area of solar panels. What killed this idea is the small beams that would be needed for the outriggers. It's nearly impossible to estimate a load case when you could be riding up and down 20ft waves. I loved this concept, but I had to kill it because of the complexity and risk. Ruthless descoping.
Underwater drive pod. This eliminated the need for a long angled drive shaft from the motor to the prop. It does place the motor under the waterline, so sealing must be absolutely perfect. A fairly standard method is to use a magnetic coupler through a polymer end cap.
I ended up building a prototype of this design, but it wasn’t able to couple sufficient torque for us in a reasonable diameter. I believe the root cause was my gap between the magnetic plates was a bit too hard. I could have tightened up all my assembly tolerances, but it felt like it was becoming an excessively complicated swiss watch of a design. KISS.
Pour one out for the things we thought about and had to pivot away from. I spent a few nights thinking longingly of the energy density of hydrocarbons. It’s just so many joules per kilogram. Ultimately we couldn’t convince ourselves that a system capable of running for 4000 hours unattended was possible with cheap COTS components.
Hydrogen fuel cell. Thought about using 6,000psi k bottles from Matheson and a PEM fuel cell. The energy storage in terms of electrical joules per kilo actually is fairly decent. The PEM cells are readily available. The real killer to this idea is the salt water contamination that happens on the PEM membrane.
Internal combustion engine. Small 2kw gasoline generator doing a fast charge every 24hr on the batteries. Basically like an old diesel/electric submarine. The joules per kilo of gasoline is SO GOOD. Hydrocarbons are a hell of a drug. I really wanted this option o work. It does require a snorkel and good filtering on the incoming air. The main issue was the lack of a small ~2000w generator with electric start. There are some sketchy Chinese units, but I didn’t see anything that really fit the bill nicely. This would accumulate about 200 hours of runtime, which isn’t terrible. The volume of gasoline would easily fit in bladders in our current hull.
TriMaran hull. They look amazing, and it’s more efficient structurally for a given surface area of solar panels. What killed this idea is the small beams that would be needed for the outriggers. It's nearly impossible to estimate a load case when you could be riding up and down 20ft waves. I loved this concept, but I had to kill it because of the complexity and risk. Ruthless descoping.
Underwater drive pod. This eliminated the need for a long angled drive shaft from the motor to the prop. It does place the motor under the waterline, so sealing must be absolutely perfect. A fairly standard method is to use a magnetic coupler through a polymer end cap.
I ended up building a prototype of this design, but it wasn’t able to couple sufficient torque for us in a reasonable diameter. I believe the root cause was my gap between the magnetic plates was a bit too hard. I could have tightened up all my assembly tolerances, but it felt like it was becoming an excessively complicated swiss watch of a design. KISS.
Funding:
(main site)
(funding)
This isn’t a 2024 Defense LARP, this is my nights and weekends hobby. A strict requirement of this project is to be cheap enough and easy enough that I could do it by myself, if everyone happened to bail out. This sets a firm upper limit on what I can spend in $ and labor. It has to be something I can accomplish on nights and weekends. I think I could pull it off for $5k. Applying a 3.14 correction coefficient to the estimate, it’ll probably cost $15k all said and done.
That said, if ya’ll want to throw a few bucks in the jar, we’ll go on this adventure together. Some of you have been kind enough to help outwith previous hobby projects, for which I’m super grateful. I’ve put together a funding campaign here. Please check it out. I’ve been considering ideas on how to reward the donors. Maybe we do a collage of twitter profile pictures on a mural on the side of the boat?
If we double the fundraising goal, we could build two copies and have them race. I’m pretty sure we could find a Las Vegas bookie to handle the bets. Also suggested was to let the internet task the second boat. I shudder to think how chaotic that would be.
Please tag some companies that you think would make good sponsors of the project. The holy grail would be a sponsorship from Mcmaster. Internet, can you make this happen?
If you have spare parts you would want to donate, everything is welcome. We could use Gopros, 18650 cells, Sunpower solar cells, tooling foam, epoxy.projectbob.xyz
givebutter.com/projectbob
(main site)
(funding)
This isn’t a 2024 Defense LARP, this is my nights and weekends hobby. A strict requirement of this project is to be cheap enough and easy enough that I could do it by myself, if everyone happened to bail out. This sets a firm upper limit on what I can spend in $ and labor. It has to be something I can accomplish on nights and weekends. I think I could pull it off for $5k. Applying a 3.14 correction coefficient to the estimate, it’ll probably cost $15k all said and done.
That said, if ya’ll want to throw a few bucks in the jar, we’ll go on this adventure together. Some of you have been kind enough to help outwith previous hobby projects, for which I’m super grateful. I’ve put together a funding campaign here. Please check it out. I’ve been considering ideas on how to reward the donors. Maybe we do a collage of twitter profile pictures on a mural on the side of the boat?
If we double the fundraising goal, we could build two copies and have them race. I’m pretty sure we could find a Las Vegas bookie to handle the bets. Also suggested was to let the internet task the second boat. I shudder to think how chaotic that would be.
Please tag some companies that you think would make good sponsors of the project. The holy grail would be a sponsorship from Mcmaster. Internet, can you make this happen?
If you have spare parts you would want to donate, everything is welcome. We could use Gopros, 18650 cells, Sunpower solar cells, tooling foam, epoxy.projectbob.xyz
givebutter.com/projectbob
What does success look like for this project?
“…making the thing”
My whole thing is ridiculous execution. I live to make things happen. Have an idea, build the idea, ship the product.
The goal is to be setting sail before the end of the year! That’s 6 months to design, build, and test. It’s going to be an epic project
“…making the thing”
My whole thing is ridiculous execution. I live to make things happen. Have an idea, build the idea, ship the product.
The goal is to be setting sail before the end of the year! That’s 6 months to design, build, and test. It’s going to be an epic project
Why are your hobbies so weird?
Wrapping up this mega thread with a mandatory plug for Varda. If you’re looking for a grand adventure, please get your resume to us (). My day job is a something of a cross between mechanical / automation / manufacturing engineer to enable autonomous hypersonic spacecraft. I’m extremely lucky to work on some of the coolest hardware in a small tightknit team. I wish I could post more about the nitty gritty details of the engineering we do on a daily basis. ITAR, HR, and Legal would prefer I keep my hobbies to non-spacecraft activities, so this is why my hobbies push in such orthogonal and silly directions. The common theme is hopefully good engineering, even if the subject matter is at times odd. They don’t sponsor any of this extracurricular stuff except through their patience with it.varda.com/careers/
Wrapping up this mega thread with a mandatory plug for Varda. If you’re looking for a grand adventure, please get your resume to us (). My day job is a something of a cross between mechanical / automation / manufacturing engineer to enable autonomous hypersonic spacecraft. I’m extremely lucky to work on some of the coolest hardware in a small tightknit team. I wish I could post more about the nitty gritty details of the engineering we do on a daily basis. ITAR, HR, and Legal would prefer I keep my hobbies to non-spacecraft activities, so this is why my hobbies push in such orthogonal and silly directions. The common theme is hopefully good engineering, even if the subject matter is at times odd. They don’t sponsor any of this extracurricular stuff except through their patience with it.varda.com/careers/
ya'll are amazing. please hit me up for coffee or a beer if you're ever in LA. First thing to buy is a laser cut keel from @KennethCassel
I'm taking the day off work today. My birthday present to myself is an uninterrupted (with the exception of twitter) CAD session
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