At 02:51 PM 7/31/02 -0400, Henry Spencer wrote:
>On Wed, 31 Jul 2002, Michael Wallis wrote:
> > ...Max pointed out at one
> > point that the trouble with 18 engines was you get 6 clusters of 3
> > engines or 3 clusters of 6 engines - neither of which lent themselves
> > to efficient vectoring.
>
>Either should work fine for vectoring, if you're willing to impose a
>straightforward transformation between the guidance-command coordinate
>axes and the engine commands. (Such transformations are far from unknown;
>the LM autopilot did one, although for different reasons.)
Coordinate transforms like this are just a matter of multiplying
by a (pre-generated) matrix called a Jacobean and is remarkably close to
trivial once you understand the underlying mathematics. I understand the
physics guys consider Jacobeans so commonplace that they sometimes use
non-orthogonal and and even time-dependent coordinate systems when
convenient, such as magnetic field lines (Boozer coordinates).
-p
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