posted March 06, 2000 05:17 PM            

anyway, i plan to have fins that rotate on the engine body and a small servo for each fin (i plan to build a steerable RC rocket/missile) i figure i can rip out the RC boards of a RC car to control the servos. the only problem is that when the rocket starts to rotate (barrel roll) the logistics of steering the thing become totally different. for example, if the rocket is spinning counter-clockwise and traveling parallel to the ground and i want to go up (ie climb/gain altitude) i would normally turn the 2 fins parallel to the ground, towards the ground, but if the rocket is spinning it would actually go up, then the rocket would turn 1/4 turn and the fins would make it turn left if you are looking at it from behind. and then after another 1/4 turn, the fins would make it turn down (ie lose altitude) and after another 1/4 turn, the fins would make it go right and so on and so on which would make the missle highly unstable.

the way the military counters this is with a complex navigation computer and gyros. this is the area my dad specializes in. however, i think i would have a bit of a problem getting a $100,00 guidence system.

i had an idea. what if i used a series of mercury switches inside the body tube of the missile that, depending on the turn of the missile, completed a circut that adjusted the fins a little and if it still wasnt right, another mecury switch would be unlevel and complete another circut that turned the fins a bit more until the fins came to a position that didnt cause the rocket to spin.

What do you people think of this? Any other ideas?

posted March 06, 2000 05:49 PM            

Don't try to duplicate military weapons because there's no way you can without spending the kind of money they do.

If you looked through the archive you'll see that this idea has been discussed very throughly in a previous posting, http://theforum.virtualave.net/ubb/Forum2/HTML/000031.html . Conclusion was to use a winged projectile (like a cruise missle) with a pulse jet for propulsion. Much more practical and less expensive.

posted March 07, 2000 01:15 AM         

So my opinion is, if you want a finned RC spinning missle, multiple fins more than 4 is
absolutely necessary. You don't need to
find out the correct verticle direction, all you need is to find out exactly how much it spins and synchronize it with the fin system.

To visualize it, say a missle is known to spin 1 turn/s after reaching full speed, on the ground, by pushing the control stick to a certain direction, sets of 2 oppsite fins in the system will be seen taking turn flapping at exactly 1 turn/s cycle. If your system can
always monitor the spinning speed then it's
even perfect.