Sean, you might consider an obvious, cheap fix - put a microswitch
against the launch rail, when said microswitch snaps open ("we've left
the launch rail" signal) delay scan for 100mS or so;  That should help
prevent off-the-rail hard turns.  For extra credit do this contact-less
i.e. have a photodiode inside the rocket, and a strobed LED just outside
the rocket on the launch pad, when the LED goes away delay(150) then
start scanning?

Could put the photodiode on the !MClr circuit - then roll of the rocket
could cause nice spurious resets.  Don't want that <G>

CP 1.5 diameters behind the CG?  That should be plenty stable if the
fins are locked straight...

  Mark

Sean Breheny wrote:
> Hi James,
>
> Well, actually, it DID turn toward the balloons, but I think it was a
> conincidence(because the IR receiver was not receiving the target signal
> before launch). I haven't had a chance to really go over the video frame by
> frame yet, but I plan on doing so to determine the rocket velocity
> (roughly) and how well the motion corresponded to what the fins were
> supposed to be doing. I am not sure if the initial large left turn was
> due to instability (too slow coming off the rail), or if it was because
> it happened to be launched exactly when the fins were turning that way
> (just because they oscillate back and forth for the conical scan motion).
> Due to having large forward fins, this rocket is not extremely stable (I
> did a static stability analysis and the CP is about 1.5 tube
> diameters or so behind the CG)
>
> Sean
>
> On Wed, 13 Sep 2000, James Newton wrote:
>
> > Sean, I was under the impression that the rocket didn't get anywhere near,
> > but from the video, it appears that it did attempt to change direction and
> > head toward the balloons. Is that just the camera angle?
> >
> >
> > ---
> > James Newton mailto:jamesnewton@geocities.com 1-619-652-0593
> > ===================================================================
> > An Art of Electronics that is falling apart usually belongs to an
> > engineer who is not.
> > ===================================================================
> >
> >
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Andy Kunz
> > Sent: Tuesday, September 12, 2000 18:31
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: [PICLIST] Sean B.
> >
> >
> > Sean,
> >
> > Don't have your address here.  Video is at
> >
> > http://www.montanadesign.com/rocket.mpg
> >
> > It's about 2.4M long.
> >
> > CD will go out in the AM along with the tape.
> >
> > Andy
> >
> > ===================================================================
> > A Bible that is falling apart usually belongs to someone who is not.
> > ===================================================================
> >  andy@rc-hydros.com      http://www.rc-hydros.com     - Race Boats
> >  andy@montanadesign.com  http://www.montanadesign.com - Electronics
> > ===================================================================
> >
> > --
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