Open questions will appear on this page for discussion.  After consensus is reached (or after a long time with no discussion), the question will be moved to the resolved category along with its discussion.

Open Questions:

MQ2013-06-11a: Fully or partially flooded hull for flexibility in configuration of sensors and actuators, or a fully enclosed hull to maximize buoyancy?

Resolved Questions:


3 comments on “Mechanical
  1. Jon Riley says:

    As a suggestion, a hull that has ballast to be negatively buoyant (in salt water) with a compressed gas (air) option and buoyancy chamber (that is preserved to maintain positive buoyancy unless actively exhausted to waste) is easiest to deliver in small scale designs. It requires one solenoid valve to exhaust (to submerge). And one solenoid to release compressed air to the inverted cup.
    If too much air is released to the cup (too much lift) then it goes to exhaust (that tube level can be preset before the mission depending on mission mass/payload).
    This method requires the compressed gas (air) pressure to exceed the ambient water pressure at maximum depth.

    I’m not sure what scale you are planning, but a scuba cylinder (or charged 1 cu.ft pony cyl) could probably exceed your spec.
    If you want to pump or charge with a scuba cyl then be careful that your pressure vessel can take the extreme pressure. The pressure in a scuba cylinder is high and decanting to any other pressure vessel is extremely dangerous and could result in death or serious injury if not done carefully to equipment that is rated to take the pressure.

    Alternatively, off the shelf carbon-dioxide pressure cylinders (for soda syphons) could also be a useful suggestion. They are also under extreme pressure, but have lower volume.

    Depending on the source of your compressed air, then you may also need a regulator to allow the low-pressure side to be controlled via a simple servo-actuator or solenoid. Scuba regulators are readily available to deliver a useful depth-compensated pressure to assist reliable buoyancy control by a simple mechanical actuator.

    If you want to shrink to a smaller scale then you will probably need a mechanical ram (screw, linear jack or hydraulic) and a compressible volume that can be compressed to submerge and expanded to re-surface.

    Good luck. I hope you sub re-surfaces the first time. 🙂
    Cheers, Jon

  2. Cecil Johnson says:

    i totally agree with a open system . u dont have to worry about imploding

  3. Phil Marcelino says:

    My vote would be for a partially flooded design. It would give the device much better control. The other option would be for some other tube which is attached to the vessel which can take in ballast, but then you might run into trouble when you start adding instruments.

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