Building A Homemade Ambient Pressure Submarine

About two years ago, [Hyperspace Pirate] set to work on building his own two-seater submarine, because who doesn’t want to have a submarine when you have just moved to Florida? In the linked video (also attached below), he describes the reasoning behind the submarine design. Rather than going with a fully sealed submarine with ambient pressure inside and a hull that resists the crushing forces from the water, he opted to go for a semi-wet ambient pressure design.

What this essentially entails is a fancy equivalent of an old-school diving bell: much as the name suggests, these are sealed except for the bottom, which allows for water to enter and thus equalize the pressure. Although this has the distinct disadvantage of being not dry inside (hence the semi-wet), it does mean that going for a dive is as easy as letting the water in via the bottom hole, and to resurface only a small amount of air injected into two ballast tanks and a pump are all that are required.

So far this submarine has survived a few test runs, which uncovered a number of issues, but diving and resurfacing seems to be going pretty smoothly now, which is definitely a massive plus with a submarine.

(Thanks to [Drew] for the tip!)

27 thoughts on “Building A Homemade Ambient Pressure Submarine

  1. I assume he is not going down that far, as a rescue diver, I must mention that this is the same as diving, going down 30ft you start to begin nitrogen build up and must surface very slow, playing around and pressurized depth can be dangerous. The volume of air one breathes in at 33ft is 2x the density. so lets just say he goes down 33ft, breathing, then boom a leak, so he holds his breath and swims to surface, he will blow out his lungs as they try to expand 2x the size. – I didnt fully watch the video, maybe he is aware of this. (side note, when we have issue at depth, we breath out slowly by humming continuously as we swim to surface – its amazing how much air you seam to have as you rise)

      1. Baro-trauma and volu-trauma are both very real things, (two distinct entities but related) seen in the critical care world as well. Even small amounts of lung trauma can give you a charming thing called “crepitus” where you skin is full of tiny air bubbles and crackles like pork rinds when you squeeze it.
        I didn’t read further but I hope the submarine person at least has some recreational no-decompression diving training.
        I can attest after working at a hyperbaric center for a summer that “the bends” is super real too.

      2. Your lungs rupture…..the air ends up just under the skin at your sholders…..if your lucky….none of it enters a vein……your dead in seconds…..or, you survive and endure the pain. Oh… will most likely drown in your own blood.

    1. Yeah, buoyancy control is critical in this case (no accidentally shooting from depth to the surface), and for ambient subs it can often be tricky due to the nature of the vessels (i.e. everything depends on the external pressure).

      Personally I prefer 1 ATM subs instead. :)

  2. Yes, it really will blow out your lungs or at least push bubbles into your blood stream or spine where they can do REALLY bad things. Paralysis is one possibility, death is another.

  3. Yup, sorry to be a party pooper but the other commenters are all right – this kind of thing is potentially very dangerous. The builder needs to have a good long chat with an experienced and qualified diver.

    1. So enlighten us as for me, I was trying to be helpful and not snide as you. Maybe I missed something, maybe the people who trained me missed something, I am always open to being wrong and learning. but hey, maybe you were mistreated and now have to do post like this to fee like you are important, or maybe you just need a hug?

    2. Ok, so you are feeling a little depressed, so in turn you insult all the other people commenting?
      Also, how do you know how much other people know?

      Hope you feel better soon. But in the meantime consider if you are adding value or just insulting people when commenting?

  4. I agree with the safety comments about diving, although if you watch the video it seems the builder does seem to have diving experience/knowledge and addresses some of the issues in the video.

    My two biggest concerns (although I do have many minor concerns):

    1) The issue when diving the first time wasn’t only the free water issue (water sloshing around), but an issue inherent to submarine design. When a submarine is diving there is a point where the center of buoyancy and center of mass approach each other causing instability. [That was an overly simplified explanation.]

    2) The use of ballast tanks for surfacing in an ambient submarine seems less than ideal. To avoid issues others have pointed out, you need to accurately control the ascent to the surface. Bowling two ballast tanks doesn’t really provide that control. Even if you just put a little bit of air in the tank(s), that air will expand as the sub rises causing the sub to rise faster, which may cause the occupants rise faster than decompression tables recommend.

    Potential fixes:
    For the first issue, making the sub dive as fast as possible to avoid spending time at the point of instability is a good solution. But this sub seems to have a large volume which requires flooding, so flooding this fast on such a small craft isn’t going to be so straight forward.

    For the second issue, add some fine control for depth keeping. The best solution I’ve seen for an ambient sub depth control was controlling the breathing bubble size, basically a pipe which adjusts the high of the air-escape vent. This allows the pilot to make small buoyancy changes (including stopping at certain depths) by increasing or decreasing the breathing bubble water level by just a small amount (a couple of centimeters or even millimeters).

    Overall (from what I can tell) the sub seems like a good start!
    If the builder hasn’t already done so, they should join (mailing list) and ask questions there).

    (I still prefer 1atm subs.)

  5. The algorithm has spoken…
    I was recommended his more recent “kayak submarine pt 1” video just yesterday. Given that there has been no update on this sub, or the kayak sub, I suspect that the creator has given up on these efforts. Very likely for many of the challenges outlined in these comments.

    FWIW, based on the other video, it does seem that the creator has a fair amount of dive experience.

  6. Can anyone comment on the benefits of this design over simple scuba diving in the traditional manner? I can’t think of any. Super trying to not be a nay-sayer, but I’m struggling to see how this is a good thing. The visibility is probably worse, the buoyancy control probably worse, and all the downsides of decompression or non-decompression diving still apply. Instead of throwing your gear in the trunk you need a trailer and a launch site. Maybe simply the engineering challenge of doing it, which I massively respect. I personally was too poor to hassle with buying scuba gear although I did get certified ages ago. I much preferred the silent freedom of freediving and spearfishing. But to each his own.

    1. Subs are fun.

      I think there are several draws for ambient submarines. For example you can cover more ground and not get tired. Many ambient subs have wet-exit facilities, so you can dive to your destination under power and get out to explore or collect things (sometimes with a tether/air-supply from the sub). Some can carry passengers, so people with little-to-no training can ride a long and experience underwater thrills.

      Maybe a comparison would be ‘why drive when you can walk’. Walking is great. In a away it’s interesting that he also has a kayak-submersible project, half way between walking and driving. :)

      Personally I like 1atm subs (with the inside always at 1 atmosphere) where you can go deeper and do not have concerns about decompression times, bonus you usually stay drier.

    2. Iirc, the builder dives wrecks that are a significant swim from shore and wants to make the trip out and back easier. He could do it on the surface, but there is a significant amount of traffic.

  7. Cool concept. Make sure to have some protection if for whatever reason(COG or turbulence), you roll too much, you don’t fart out all the air quickly and then not be able to replace it. May want to look into using an Arduino to control a hacked up BC to have your wet area linked but separate enough so you don’t risk a flood. The Arduino could also handle trim and ascent/descent rates too.

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