Hello from new forum member!

[DaveAK]

Hi all! Just thought I'd start an introductory thread and check that I've come to the right place for help with a project I'm in the initial planning stages for. I'm currently kicking around ideas for an AUV and preliminary research on the internet often brings up links to the SubCommittee. Not a submarine in the sense of what you guys are doing, but it will need to operate underwater as well as at the surface. I understand the basic principles, (or at least I think I do!), but I'll need a little help with some of the finer details and already have a couple of questions about ballast tanks. If you'll humour a non-Navy guy and a non-Navy vessel then I'd be more than happy to pony up the very modest membership fee to be able to pick the brains of some very obviously knowledgeable individuals.

My background isn't very impressive in any particular field, I'm just an avid tinkerer with overly ambitious ideas! I live in Alaska and spend my winters in my workshop. Right now I have more projects than I know what to do with, but that hasn't stopped me thinking about more. With this AUV my aim would be to continue the research and design this winter, start purchasing what I need over the summer, and complete construction next winter. My intention is that I will track the vessel using GPS and satellite communications, and be able to monitor its performance and provide it course corrections as needed.

The goal of the project isn't a particularly noble one, it's simply a question of a) can I do it, b) how long will it run for, and c) how far will it travel? I plan on equipping it with solar panels to recharge the batteries, and propulsion will be limited with it mostly spending its time drifting with the ocean currents. It will need to dive and resurface of course, and any remaining power will be used judiciously to navigate as best it can. The control and communication systems are what I'm most familiar with and get a lot of fun from, the rest is uncharted territory for me. I have a lot of concepts for this rattling around my head from the impractical to the more than likely impossible. If you guys are willing to help me out by answering questions then I can fine tune my plans in to something that might actually work, and just as importantly that I have the resources and ability to build.

So with all of that said I'll go and do some more reading before posting my questions. It might be that I can find what I need to know at the moment with a bit more digging, but I'm sure I'll have plenty of questions for you all as this project progresses.

Dave

[Ralph --- SSBN 598]

Welcome.

If your intentions are to run this AUV free of cables, you might want to look in to Sea Gliders.
They are submersibles that travel the oceans with no propulsion motors.
Guided by new GPS instructions when surfacing.
Correct heading and dive again on a predetermined course collecting sea temperatures and current data.
Here is one of many articles about Sea Gliders.

They operate with ballast systems and movable weight inside to change the pitch so the boat dives and surfaces.
It glides up and down on an angle producing headway.

It sounds like this is similar to the project you described.
Again, Welcome.

Ralph --- SSBN 598

[DaveAK]

Thanks for the link Ralph. It's not one that I've come across before, but it is very similar to what I'm trying to achieve - maximum distance with minimum power, speed not critical. In fact all the cool stuff I've been thinking up over the last few days is already incorporated in to their design, although I'm not planning to go as deep. Still, I'm not really trying to come up with anything unique, but something that I can have some fun with. Off to do some more research on Sea Gliders!

[southern or]

Portland State University's Rocket club is working on a guidance system for they're new rocket. It's not a sub, but the software and components could be modified and used on a sub. Keep in mind that autonomous vehicles have a decent high loss rate. There are at least four that I know of that are at the bottom of Crater Lake, so failsafes and a homing beckon is a must.

I haven't been following any AUV builds, but the system PSU is using should be modifiable for a sub, but you'll need a good grasp on Linux and electrical engineering. psas.pdx.edu I've seen the electronics bay of a few AUVs and a lot of the hardware is the same.

To go along with what Ralph was saying, a lot of the AUVs I've seen aren't static submarines but a few were. Some operate along the same principle as the sea gliders except they have powered propulsion and operate under a modified version of dynamic diving. I think the one the USGS used with my college had a weight system that shifted the CG, but I can't remember as that was years ago. A lot of the new ones look like modified torpedoes. Keep in mind that a lot of the exploratory versions have avoidance and mapping sonar systems and a pretty sophisticated software suite to prevent them from hitting something, but it all depends on how deep you want to go and what your needs are. Needs and depth also help determine the building materials needed too, like fiberglass resin for shallow, and high grade steel, titanium, or high grade aluminum for deep divers, but I've seen one made from carbon fiber but I don't recall it's operating depth.

[DaveAK]

Thanks southern or. Failsafes and a homing beacon are both things that I've been considering. I'm thinking about various modes of failure and what I can do to prevent them. I'll probably use some redundant/backup systems, but I've also got to watch cost doesn't get out of hand. I'm expecting that this will eventually be lost at sea, it's just a question of how long I can delay that! I took a look at that PSAS site. Linux and microcontrollers are things that I play about with a lot, although I'm no expert at any of it, so that part I'm actually comfortable with. Luckily I won't be travelling at the speed of a rocket, so I won't have to have the most efficient or quickest code. As for depth I can't see me wanting to go below 100ft at a maximum, and this will most likely be dictated by the material I use. Again, cost will be a big factor.

[DaveAK]

So I've been digging around the forum a bit and I'm hooked. After lots of discarded ideas I think I've come up with a good solution for what I need, but of course I still have plenty of questions. The first one is when things go bad, how quickly do they go bad? If I've got this right you guys build your subs with slight positive buoyancy and dive using forward motion and the dive planes. This means that providing you don't take on extra water if forward motion ceases the sub will come back to the surface. If I go with a sea glider then I'll have to rig for negative buoyancy to dive without propulsion, and if the system fails at this point then it's goodbye unless I've got some way to blow the tanks. Lets say design depth is 100ft and at this point I want to reverse buoyancy back to positive to rise, but something goes wrong. How long do I (or the glider) have to react before things go from bad to worse? Answering my own question I guess it's all to do with dive rate, and this is my unknown at the moment. So is there any easy way of working this out or ballpark figures I can use?

The other question that I have right now is what kind of life cycle can you expect on a piston type ballast tank such as the Engel ones? As a point of reference a Rutger sea glider did a trans-Atlantic crossing in 221 days performing 11,000 dives in the process.

The design that I'm kicking around could easily be modified to include a drive system if need be, but to start with I'm planning on a pure glider for power reasons. It's all subject to change of course as I learn more about the practicalities of what I'm actually trying to achieve.