Re: FW: Model Rocket Plan

On Mon, 30 Aug 2004, Adrian Tymes wrote:
> > ...With eight
> > deflectors, you can even get roll control this way. 
> 
> Why not just six?  Two for each axis you wish to
> control: roll, pitch, and yaw.

If you're feeling minimal, it can be done with five, as on DC-X's
maneuvering flaps.  One deflector on each of four sides to do pitch and
yaw... and then *split* one of them, with the two halves movable
independently, for roll. 

Bear in mind that on a well-built rocket, roll torques are quite small,
and you can think of dealing with them by some separate means with less
control authority, or even just ignoring the issue if you limit the rate
(with fins or rollerons) and tolerate a bit of random roll. 

The Pegasus second and third stages, for example, do pitch and yaw with
nozzle gimbaling, but use little cold-gas thruster packages for roll
control. 

                                                          Henry Spencer
                                                       [email protected]