agooga:
I'm curious about a few things regarding this plan; my questions might seem a little cranky or gruff, and I don't want to discourage your plan, and perhaps I am not thinking outside the box enough - so bear with me.
First off, I am wondering how many model rockets you have flown in the past? If you have ever flown any, then you will soon see the issues you will face in this project - a few of which I am going to summarize here.
I initially wondered where this light show was going to occur, because so far as I can see it, it can only occur: on a static display, on the pad or in the air. Giving it a little more thought, I realized that the only place where you'd be able to see anything of the light display was -only- on the pad. Once that rocket takes off, you won't be seeing anything. At the apogee, when the chute is deployed, you still won't be able to see much, because it will be so far away - there might be some form of twinkle, but that's about it. Maybe with a pair of binoculars you might be able to see better, but not by much (as anyone who's ever tracked a model rocket can tell you, just keeping the rocket as it descends in-frame is hard enough). Once it is lower, you might see more, you might see less - depending on where it lands, how far away downrange it is, etc.
I also wonder how you intend to even see the light display? AFAIK, night-flying model rockets isn't legal, and can get you in trouble with the FAA (or whatever the equivalent is in your country - you don't say where you are located) pretty quickly. That's not even counting on whether having an on-board light display is legal. I also can't imagine tracking such a rocket at night using binoculars, even with a running light display (and forget it if the light display fails to work for some reason).
What's your thoughts on the above?
Finally - I am wondering how you intend to connect the LEDs to the Arduino? Your LEDs will be on the outer tube of the rocket (so far, so good - though you are going to want to run several wind tunnel and other tests to verify that the rocket won't go off-course due to the extra drag caused by the LEDs, etc - on the outside). Since the ejection charge from the engine has to travel up through the tube to push the nosecone and chute out, your Arduino would have to be in the nosecone (at first glance). The data lines would then need to be connected (in some manner?) to the data lines on the tube via some kind of specially made "friction" contacts around the inner top edge of the tube (and bottom outer edge of the nosecone)...
Alternatively, you could invert the workings of the rocket, and have the ejection charge blow out the engine pod (which would consist of the engine and fins, mainly - you see this on simple two-stage rockets for the first stage), draging the chute out. This way the Arduino could be directly connected to the LEDs, with no nosecone separation.
Another method might be to forgo an ejection charge entirely, and have the Arduino trigger something to cause the ejection, rather than using an engine with an ejection charge (this is how many high-power model rockets eject their chutes - although you have to make a black-power ejection charge, and have a source of kevlar cloth).
The first method is problematic in that the light show, at apogee, would stop when the ejection charge occured (making downrange tracking - especially at night - difficult to impossible). The other two methods would require a custom rocket to be built; not an impossibility, but not easy, either (and they would require a lot of testing before first flight to ensure that they don't go "horizontal" on takeoff).
Finally, you don't mention what kind of "model rocket" you intend to use? Do you have a specific model picked out? Do you know what engine size/impulse you will be using (this is very necessary data just to know whether it will even get off the pad - of course, you won't know anything until you can calculate the final weight of the payload and display)?
There's a lot more to this project than simply sticking an Arduino (well, its equivalent) and driver circuitry into a tube arrayed with a bunch of SMD LEDs - if you want to have a chance at succeeding, while not endangering spectators, and not running afoul of the authorities...
Good luck!
