Re: Underwater questions [ot]

In a message dated 11/2/99 6:33:48 AM Pacific Standard Time,
gromit+@CMU.EDU 
writes:

> > >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. :) 

Would an Aerobraking system work?
-Stephen