Case 3: cracks

Occurrence of straight cracks along the axis of the motor can relatively easily be calculated. In the following figure one crack is simulated in 4 of the 6 segments. The influence of one crack in one segment is not very significant given the small increase in burning surface. In general cracks will contribute to a faster thrust increase at the start.

BEM 3 simulation with one crack over 4 segments

Case 4: what happens if in a number of segments, the bottom and top surfaces do not burn?

In the following figure we have simulated what happens if in 2 segments the bottom and top surfaces do not burn at all. We can see here that the thrust and pressure is taking up

BEM 3 simulation with 2 bottom and 2 top surfaces not ignited

more slowly and that the maximum thrust and pressure get a bit higher. Although less burning area is available the gas speed is higher due to a lower initial pressure. If more than 2 segments suffer from this problem a slower take up and higher final thrust will be favored.