Analysis:

The temperature graph only shows a significant increase in heat many seconds after the engine has finished burning. This is significant because it shows that PVC reacts slowly to heat even when it is being directly exposed to it (the very last point on the graph that we see thrust is when the hot combustion gases are very close to the body of the PVC). This, in turn, shows that PVC has a very slow response to the gas.

This is a good thing and a bad thing. When PVC is cool, it is very stiff. Once PVC heats up, it becomes very moldable. As such, if enough pressure builds up within the PVC to make it explode and the PVC has not warmed up yet, it will literally shatter, sending shards of sharp plastic everywhere. PVC's tensile strength increases once it warms up, so the chances of it simply blowing up like a balloon at high pressures are more likely than it exploding.

Something that can be noticed from the force graph is that the engine spent lots of time burning precious fuel and producing minimal thrust before the 'spike' that is the main combustion (and thrust-producing) sequence can be observed.

Why did the engine spend so much time simply idling? We believe that the answer is that there is a special pressure that must be reached within the engine before it begins burning propellant at the rate needed for the nozzle to have maximum efficiency and produce thrust of the magnitude we expect it to.

How do we fix this? Somehow, the engine must be brought to that special pressure in minimum time. We have thought of two possibilities:

1. Manufacture some sort of nozzle plug that will blow away as soon as the engine reaches our desired pressure.

2. Use a larger igniter to produce the desired pressure and ignite the motor at the same time. (This option is both easier and safer to implement, so we will explore it first.)

The rocket after the static test.

The nozzle after the static test.