We can also seriously discuss active roll control then, although Dan
can't make it to Tuesday evening meetings for a while...


Thanks for all the feedback. I can't make the meetings for a bit, so that's why I wanted to get some people's ideas from here.

I plan to create a 'Roll Control' wiki page to track ideas and progress.

Perhaps we consider making 2nd's of the critical parts, and have a
replacement payload or avionics module that facilitates the canards?

That's what I was thinking, or maybe even put the fins on the payload module (but away from the patch antenna). The point is, we DON'T want the fins in *front* of the CG, and the CG is pretty far back, like around the payload bay.

1) Please use the airframe list. Really. That's what it's for.

Done!

Greenberg<and...@psas.pdx.edu> wrote:
PS. Sure, why not?

Nathan Bergey wrote:
I think it's a good idea.

Camarillo<dave.camari...@gmail.com> wrote:
I must admit I'm biased toward the spin control idea, mostly for it's
coolness factor...

<rq1...@q7.com> wrote:
[Paraphrased by Dan] ...If it's safe...
For extra credit, control spin / direction during descent on the drogue.

That's a good enough response for me to do some of the ground work.

Some basic requirements so far:

1) Small 'canard' style fins, so that they fail safe.
2) On error, fins go to neutral.
3) Fins have short mechanical travel to minimize control gain.
4) Fins are mechanically linked to ensure they must operate together, only in the roll (rocket) axis.
5) Fins placed near CG to minimize steering if alignment is off.
6) One powerful/fast servo, instead of many.
7) If we are really worried about uC failures, we could do a hardware watchdog CPLD that centers the servo if it doesn't get serviced. That requires 1 chip and a few caps.


Testing:
1) I like the axial bearing rig on the pickup truck. We should do that anyway.
2) How about a mythbuster's style "chicken gun" tank to use as a high speed wind tunnel? All we need is a pipe, tank, valve, compressor, and a pitot tube... 3) A leaf blower claims an exit velocity in excess of 200 MPH. I'd bet faster if ran in a circuit. Perhaps more than one could give us the speed and flow we need for a small wind tunnel?

http://www.aerorocket.com/offer.html
http://www-htgl.stanford.edu/bradshaw/tunnel/index.html

Dan





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