This is really neat. I probably drew 100 diagrams of submarine designs as a kid. Kudos to him for actually building one (or four for that matter).
I'm curious if the 30ft depth limit is simply a practical safety limit (if you remember back to High School Physics, 33ft of fresh water = 1 atmosphere of pressure) or if he actually worked out the limits of the drainage tubing/joints/skylight/other components. It would be cool if he did a technical writeup.
It's linear. The surrounding pressure increases by the following:
P=γ*h
P=pressure (lb/ft^2)
h=height (ft)
γ=density (lb/ft^3) water = 62.4lb/ft^3
So if he goes down 33ft, the pressure @33ft will be:
Total pressure: 62.4x33 = 2059psf (1atm ≈ 2116.21psf)
What physically matters is the pressure difference. 2atm:1atm and 1atm:0atm are the same -- they both exert 1.03 kg-force per square centimeter of wall.
If you're asking how does pressure change with depth, it's linear for water. The pressure is just the sum weight of the column of fluid above you. Since water is (basically) incompressible, the density is the same at any depth, so, the fluid weight is proportional to the column height. At ~10 meters, it's 1.03 kgf per cm^2 or 1 atmosphere (on top of one atmosphere of air above, for 2 atmospheres total).
It's the opposite for air. That's a compressible gas, so density increases with pressure, which makes pressure an exponential function of altitude. A packet of air is compressed by the air above it, which makes it denser (more mass/volume), so that the pressure below increases at a steeper rate.
I also designed a bunch of submarines and wanted to build one for the masses. Until my friends told me I was crazy and I would kill myself.
My final design was using scuba tanks to equalize the internal pressure of the sub with ambient pressure at specific depth.
This was a clever design but limited it's usefulness to 30f as well.
It simplified the construction of the sub but limited its use as it required depressurization following the same rules applied to SCUBA divers. So at 30ft you could be submerged for a while, but any deeper it limited the time you could remained submerged unless you depressurized before surfacing.
Relatively little danger, with the proper care and attention (it pumps oxygen from the surface). Also, watch some of his interviews, he seems very competent.
Finally; sometimes a little bit of danger is what makes things worthwhile :)
This is true but with the proper precautions one can take measures to reduce the risk. Never to complete zero of course and it will probably always be relatively dangerous to travel underwater. But it's already dangerous to travel in a minimal atmosphere, in a pressurized vessel, at the speed of a bullet, and it happens everyday via air travel. More work in the field from pioneers like these students will help reduce the risk for future travelers.
It would be the same as if you were in a car that dropped in a body of water. Do not panic. Let the water fill up the submarine while breathing deep to oxygenate your body just like a swimmer. When enough pressure is gone from the submarine filled with water, open the hatch and swim to freedom. Most people drown in these scenarios because they try to leave before it fills with water and panic sets in.
In the mythbusters episode where they tried that, Adam "died" the first time he attempted doing it that way. It worked after he gained experience escaping, but most people aren't going to have the training/ability to escape that way.
The best thing to do is to open the door as soon as it hits the water before the pressure is too great, or to break the window if you have the tools.
The thing is, when a car hits water, it is usually in a violent way where I would imagine people would be momentarily stunned. By that time, the water pressure outside would be too high for them to open the door. Breaking the window is a bit hard to do as well for most people in that situation. Breakout window tools are great, but most people leave their tools in the trunk. This is where the controlled breathing is vital. I have not been in this situation, but I have been in drowning situations where I have helped someone in the ocean. I took quick, deep breaths and it helped me while I was underneath the water searching. When I was a kid, I took swimming lessons, and the first thing the trainer talked about was controlled breathing. Before we even started swimming around, he would make us stay still while taking deep breaths. Try it anywhere and you will see how your body reacts to it afterwards.
This is so cool and I've followed others doing similar "personal" submarines. I hope this continues trending and we see more private exploration of the seas. It's quite an engineering feat, analogous to space travel in some ways. The more work done in the field the more the cost will drop and the more accesible it will become. I imagine one day we'll see the ocean in a much different way.
Another teen that has built a submarine is Håkan Lans (http://en.wikipedia.org/wiki/H%C3%A5kan_Lans). He built a submarine that took him close to 100 m deep (I find different sources, 90 - 110 m). This was in 1968 while he was 18-19 years old. He subsequently was drafted to FOA, the Swedish defense research institute, and is probably the most famous (to Swedes in general) now living Swedish inventor.
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[ 2.4 ms ] story [ 75.9 ms ] threadI'm curious if the 30ft depth limit is simply a practical safety limit (if you remember back to High School Physics, 33ft of fresh water = 1 atmosphere of pressure) or if he actually worked out the limits of the drainage tubing/joints/skylight/other components. It would be cool if he did a technical writeup.
If you're asking how does pressure change with depth, it's linear for water. The pressure is just the sum weight of the column of fluid above you. Since water is (basically) incompressible, the density is the same at any depth, so, the fluid weight is proportional to the column height. At ~10 meters, it's 1.03 kgf per cm^2 or 1 atmosphere (on top of one atmosphere of air above, for 2 atmospheres total).
It's the opposite for air. That's a compressible gas, so density increases with pressure, which makes pressure an exponential function of altitude. A packet of air is compressed by the air above it, which makes it denser (more mass/volume), so that the pressure below increases at a steeper rate.
My final design was using scuba tanks to equalize the internal pressure of the sub with ambient pressure at specific depth.
This was a clever design but limited it's usefulness to 30f as well.
It simplified the construction of the sub but limited its use as it required depressurization following the same rules applied to SCUBA divers. So at 30ft you could be submerged for a while, but any deeper it limited the time you could remained submerged unless you depressurized before surfacing.
(http://www.justinbeckerman.com/Site/Home.html)
Finally; sometimes a little bit of danger is what makes things worthwhile :)
The best thing to do is to open the door as soon as it hits the water before the pressure is too great, or to break the window if you have the tools.
Does anyone know?