Really cool work on making your own rocket motors.

I wonder why he calls it a MANPADS (Man portable Air Defense System) It does slightly resemble a Manpads, but with a GPS based guidance system it would not able to be used for air defense, even conceptually. Typically manpads would use something like an infrared/optical or radar guidance system which would run way more than $5. This does seem like a cool home made AGM-176 or similar. There's always been a side project idea in the back of my head about what the cheapest IR or laser guided RC Plane launched rocket would look like. A cheap rocket design powered by some model rocket engines that could be used for a drone -> drone intercept cheaply.

Awesome job taking a fun idea into reality. It's really impressive to see the design work