Re: Armadillo 4/18

>> >rocket has no built-in tendency to amplify a perturbation, departing
>> >faster and faster from the desired attitude once nudged off center. 
>> 
>> ...other than sloshing propellant, which may be a significant
>> factor in a real system.
>
>True, depending on design and conditions.  Also, that will generally be an
>oscillating disturbance rather than a simple one-sided instability, so the
>analogy remains weak. 

Right.  It's possible for it to be non-oscillating; if you hover
at an angle the free surface effect may be constant, but that is
probably rare on rockets as opposed to say ships, where I first
learned about the significance of the effect.  Particularly significant
in damaged stability calculations when part of a ship has flooded...

The natural slosh frequency should be avoided in the control loop
systems, however, as getting into a slosh/maneuver feedback loop
would quite possibly be a Bad Day.


-george william herbert
[email protected]