The goal is to attach a small camera to the outside of a solid state fuel rocket 3 miles into the air that will allow me to see that the earth is indeed flat.
Good for you... but I can think of two (sorry.. three) reasons why it wouldn't work.
1. 3 miles up is not enough to see the curve of the Earth so seeing a flat horizon from that altitude would not prove your flat Earth belief.
2. The Earth is not flat so your experiment would fail even if you could make it to 30 or even 300 miles.
3. FE people seem to have a habit of not accepting evidence obtained from a camera.
From the FAQ page...
In general, we at the Flat Earth Society do not lend much credibility to photographic evidence.
However it is your choice of course so good luck....