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Design and Construction Ideas

This sub is a small, fast, "hydro-dynamic" design. It is intended to have complete freedom of motion in three dimensions. Some of the design philosophy behind this sub comes from Deep Flight. The basic body design was inspired by the VASH submersible. A lot of input on the design and construction work was provided by Dennis Kaiser, who built the first VASH prototype.

This is a dry, one-atmosphere sub. It will be positively buoyant, like both Deep Flight and the VASH. It is a two-seater, with the passenger seat behind and slightly higher than the pilot. It is a fairly shallow depth sub, having a depth limit of about 100 feet.

The canopy is cut from an F-16 fighter jet canopy, which is what the VASH uses as well. The F-16 canopy is extremely strong. It is 3/4" thick acrylic, capable of withstanding a strike from a four pound bird at 350 knots.

The inner and outer shells are hand-laid fiberglass, each one 1/2" thick. The space between the shells (varies from 3" - 4") is filled with a sprayed-on closed-cell foam, the kind that dries very stiff and hard. The cockpit is pressurized at one-atmosphere. The rear compartment is flooded, and uses modular component packs. Currently, it has three modules:

  1. The Power Supply Module - Four 100 amp-hour gel batteries.
  2. The Propulsion Module - Two 35 amp electric motors, plus the propeller shafts, propellers, and the thruster tunnels.
  3. The Oxygen Module - Two 80 cubic foot (@ 3200 psi) oxygen tanks.

The first two modules drop out of the bottom of the sub, and the third comes out the top. A large portion of the bottom and top of the shell at the back forms a pair of removable covers, which allow the modules to be removed and/or replaced. Since the rear compartment is flooded, I don't have to worry about sealing anything (except the modules themselves).

The nice thing about using a modular system is the ability to replace the modules easily when new technology comes out. One example of this is the power supply module. At some point in the next few years, a new form of hydrogen storage will be coming on the market, which will allow replacement of the batteries with a high-density hydrogen tank and a hydrogen fuel cell. This hydrogen tank/canister will contain enough hydrogen to power the sub for more than 100 hours, and will cost less than $80 per charge.

Another possibility would be to replace two of the batteries with a small gas engine driving a generator, which could recharge the batteries while surfaced.

The front lateral fins are fixed, and are shaped like an airplane wing, except upside down. This will give enough downforce while moving to counteract the large upward buoyancy of the sub. They also have a pair of high-intensity lights mounted on each side. The rear fins deflect independently, and are controlled by a pair of one-axis joysticks. The top fin is controlled by a pair of foot pedals (similar to an airplane's rudder). Each fin is moved by a manual hydraulic system.

Each thruster is powered from a single 12 V motor, and they counter-rotate to offset any tendency for the sub to "torque" (like a typical single-prop powerboat does). The motor speeds and directions are independently controlled with finger triggers on each joystick.

I chose a sitting position, unlike Deep Flight's prone position, for a number of reasons. The main reason is that it allows entrance and exit of the sub while it is still in the water, and thus the capability for single-handed launch and retrieval from a trailer. Also, for a three-hour dive, I suspect it would be a good deal more comfortable. The only down-side I can see is the reduced visibility downwards over what Deep Flight has, but that is a trade-off I'm willing to live with.

The seats will be molded in fiberglass, form-fitting, with a thin layer of high-density cushion foam. The pilot and passenger will be held down with a full five-point harness, for those awkward times when the sub is upside down :-) The pilot's seat folds down (backwards) for entrance, and then is folded back into the normal position and locked to allow the passenger to enter. The rear half of the canopy slides up and back to allow for entrance/exit while the sub is in the water.

For breathing, it uses a carbon-dioxide scrubber, which is basically a tube stuffed with Soda Lime, which chemically reacts with carbon-dioxide and removes it from air. The oxygen removed from the air in the cabin (by breathing) is replaced with oxygen from the tanks, with the flow rate set to the appropriate amount (depending on whether or not there is a passenger).

The sub will have a large number of sensors, to measure various parameters, including:

  • speed, distance traveled
  • pitch, roll, compass heading
  • GPS (while surfaced)
  • water pressure (allows you to calculate depth from surface)
  • depth transducer (depth to bottom when level)
  • water & cabin temperature
  • cabin pressure (barometer)
  • oxygen, carbon dioxide levels
  • motor RPM, current draw
  • power level remaining in battery pack
  • oxygen tank pressure/flow rate

The external sensors will be in the rear compartment, through the bottom of the hull. Speed, distance, and water temperature are all on one transducer (from a sailboat), and water pressure and depth to bottom each have their own transducers.

The GPS receiver will be mounted directly behind the passenger's head, for best reception while surfaced. The fluxgate compass and the pitch and roll sensors will be mounted up near the nose.

Future Enhancements

There are a number of ways to enhance a sub like this, once the basic mechanical sub is working. Some of them are:

  • a front-mounted CCD video camera.
  • two stereo microphones, one mounted on the top near the back, and the other in the nose-cone, just below the camera.
  • a custom onboard computer system.
  • side-scan and front sonar (hooked into the computer system).
  
 

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