Re: Underwater questions [ot]

Excerpts from mail: 2-Nov-99 Re: Underwater questions [ot] by Beth
Fulton@marine.csiro 
>  
> >5)  What is the best shape for a lander desgined to move though the
air and 
> >go into the water?
>  
> Hydrodynamics and aerodynamics share an awful lot in common due to the
> basics of fluid dynamics. Just remember to give it stabilisers so it
> doesn't go into a spin once in the water.
>  

Yes and no.

Water differs from air in two major ways that impact what you're
discussing:
-Buoyancy
-Density/viscosity

In air, a plane must support itself through lift.  This means that the
plane must be light, strong, and have a large wing surface.

In water, a vehicle is supported vertically through buoyancy.  In order
to move through the water at a reasonable speed, it needs to have a
small cross-section with nothing that will snap off due to the drag on
the vehicle (like wings).

Thus airplanes and submersibles are fundamentally different, and I doubt
you could make a very effective vehicle that operated both in the air
and the water unless you've got exotic technology (like anti-grav).

Yes, I'm a mechanical engineering student; no, I don't like fluid
mechanics at all. :)