The second test of the hybrid PVC prototype ended in CATO. Two possible reason were:

• Oxidizer leak in combustion chamber prior to ignition.
• Igniter malfunction,not burning through the oxidizer feed line.

The above images illustrate clearly the state of the engine after CATO. Notice that injector and nozzle areas are intact and that oxidizer feed line is still attached to injector.

frame1

frame2

frame3

Analysis:

The three frame images above are 1/30 sec. each.

Frame1 - Can see white plumb of smoke from igniter charge coming out from nozzle section.The pressure gauge shows no action.

Frame2 - Orange flame mixed with white smoke indicate engine start. Still no pressure gauge action

Frame3 - Explosion occurs, orange flame on top of frame, nozzle section flying by, pressure gauge registers the burst force.

Since CATO occurs so early and just as the igniter was set off, I tend to think that the cause of the explosion is due to a leak of the oxidizer in the combustion chamber prior to ignition. The chamber was oxidizer rich and at the moment of spark CATO occurs.

The other possibility is that the igniter didn't break the oxidizer feed line thus blocking the nozzle exit area and causing pressure build up that eventually CATO the engine. I tend to think this scenario would not have caused CATO to happen so quickly.