Requirements

1. Nozzle shall expand exhaust to ambient pressure (since ambient pressure changes throughout flight, will choose pressure at altitude 0.75? of the way to target altitude → need to justify why)

2. Withstand 2x maximum operating pressure

3. Attach securely to motor case

4. Withstand temperature of fuel burn

5. Prevent gas leak between graphite, phenolic, and carrier interface

6. Support the fin can under high acceleration

Our launch site elevation is 4600 ft above sea level.  We will optimize for roughly 3200 ft above the launch site--a total elevation of 7800 ft.  Our current expansion ratio is 8.517, and the nozzle throat will be 1" in diameter.

Nozzle Phenolic

The above image is a rough sketch of the current nozzle phenolic design, though many dimensions are dependent on grain geometry, expansion ratio, etc. and are thus subject to change.  In Prometheus, the phenolic piece was in two parts: a phenolic insert and a top ring.  Machining the top ring was incredibly difficult as it was too thin to be held by the lathe, so the goal is to make the phenolic portion this year one whole piece, though how that will be accomplished while keeping it manufacturable is yet to be determined.  To further increase machinability, instead of having the graphite and phenolic bottoms end in sharp "V"'s like they did last year, this year both will be flat faces.