Francois Labreque <fla### [at] videotronca> wrote:
> Le 2016-01-08 22:52, clipka a écrit :
> > Am 09.01.2016 um 00:39 schrieb Mike Horvath:
> >> I'm building a spaceship in POV-Ray.
> >>
> >> I think that, normally, you want to put the maneuvering thrusters at the
> >> cardinal directions of the spaceship so that you can turn most efficiently.
> >>
> >> But can you put them at other places too?
> >>
> >> I mean, instead of just the top/left/bottom/right, can you place
> >> additional thrusters around the circumference of the ship?
> >
> > Certainly you can -- it'll actually be a bit more effective in terms of
> > propellant consumption (probably by a factor of about 1.2).
> >
>
> The fuel-saving factor depends on the geometry of your spaceship (more
> specifically, its moment of inertia).  And you probably need to take the
> occupants' well being in consideration as well*, and not just your fuel
> mileage.
>
> For example, if the Millenium Falcon wants to turn right, and only fires
> the left-side thruster to turn the ship (minimizing fuel consumption),
> it will rotate about an axis (called the "instantaneous center of
> zero-velocity") that's somewhere between the central turret and the
> cockpit - assuming an uniform mass distribution.  This means the cockpit
> will appear to move backwards.  to reduce motion-sickness from the crew,
> you would have to fire most thrusters as well, and the left-side ones a
> lot more, so that the instantaneous center of zero-velocity is right
> undeneath the cockpit, using a lot more fuel.
>
> *Unless, of course, they have Star Trek-like inertial dampers.
>
> --
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Keep in mind that they also want to turn gradually, not make a right angle and
fly off in a new direction instantly, because of inertia.

Assuming that they did simply turn the ship at a right angle, they'd still need
to fire the off-side thrusters to control the turn.  It makes sense, if you
assume that they're already burning their thrusters, that they simply relax the
thrust on one side and then gradually shift the thrust back to center, so that
the center of pressure is always behind the center of gravity.

Regards,
A.D.B.

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