Ye Olde Rocket Forum - View Single Post - Houston...you guys know the rest.

Quote:

Originally Posted by blackshire

If a M.E.S.S. form submission is in order here, that would be well worth inspecting the motor for. That happened with an Omega of yours once, if memory serves (where the clay of one of the stages' D12 nozzles asymmetrically eroded, making the rocket pitch over under power and hit the ground hard--you even caught it on camera too, I think). Even perfectly symmetrical erosion of a clay nozzle (as unlikely as such an occurrence would be) would drastically reduce the motor's thrust, regardless of the motor's size and rated thrust-time curve.

Since that Omega Cineroc flight, I've found that off axis thrust is pretty common with BP motors, especially during that critical time of high thrust the first 25 ft or so off the rod. Nozzles normally look fine after flight, so I don't know if smeared clay nozzle material, igniter residue, or something else causes it. Many of the super slow-mo videos on Youtube show this also. With that in mind, I don't know if Estes would want to start honoring off-axis thrust as a reason for flight failures.

BTW, I used to see off-axis thrust in C-slot composite motors all the time. You'd think the nozzle would straighten it out, but a nozzle throat is just a fraction of an inch long.