Importance of the test stand - J680 Test (Failure)

This was the first test of this motor design. Motor is designed to be operating at a maximum of 612 PSI, a pressure which my other motors have no problem with. In this test, however, the nozzle blew out. Without the pressure gauge and video I would assume that the concrete nozzle was not sufficient to hold the expected 612 PSI of this motor. Conveniently, I had a pressure gauge connected to the motor which was able to show in the video that the nozzle was not the cause of the failure. May not be the best test stand in the world but it surely beats nothing!


The gauge has a maximum reading of 1,000 PSI with a number at every 200 psi graduation. If you watch the video you will see where the gauge passes 1,000 PSI!! The nozzle held well up to 1,000 psi so it surely wasn't the cause of the failure.

I'm now thinking that the grains were not inhibited properly. I used 3 layers of posterboard paper as inhibitor. Comments are welcomed.

Update:

It was explained to me by a senior sugpro member that my high pressure may not be just a problem with inhibition, but rather the fact that I'm using sucrose and dextrose and not purely dextrose as the reducer. My motor design was based on the assumption of dextrose fuel, but the sucrose+dextrose mix may have caused the motor to behave more like a sucrose only mixture, or at least an average of the two. This means higher pressures than expected.



Video and snapshots follows:

0 PSI

80 PSI

420 PSI

800 PSI

1,000 PSI

Failure

Motor specs