What caused this failure?
 

Hey Guys,

Last week at the club launch (their launch pad), I set off an Estes Loadstar 2456 (prebuilt kit) and on the first launch of this rocket, it corkscrewed severely flying in loops until it crashed. I contacted Estes and they are providing a warranty no questions asked, but I am trying to determine what happened. They did indicate it could have been an engine problem.

Every time I place a rocket on the rod, I slide it up and down as to ensure no binding will occur and the lugs appear well, aligned, etc. I also place the lugs towards the wind, so the rocket is at the leeward side of the rod, though there was next to no wind. Everything looked perfect on the rocket to me as well, and was inspected by the club representative prior to launch. It appears the rocket never got enough momentum to fly properly. Now thinking back, I do recall one instance during the day that I was preparing a rocket. I placed the engine in, then igniter, and finally the plug. I do recall the plug aligning perfectly with the engine retaining clip. In a sense, the clip could have held the plug in? I have my Bertha’s and other rockets that use this same clip assembly, and don’t recall it ever seeing it lining up like this. At the time, I do recall a question coming to mind about the ability to push out the plug, but it quickly escaped since it was the “design” of the rocket and hence should be fine. So, is it possible this clip held the plug in, hence igniter and finally the alligator clips of the launch controller long enough to impact the ability of the rocket to get up to the appropriate thrust/speed to fly?

Anyway, I was not sure Estes would warranty it and kudos to them for doing it, but I was perplexed about this failure and for safety reasons, really want to know what happened as to avoid it in the future. Again, I cannot say this rocket is the same one I noticed the plug issue on, but starting to think that may have been it. I am normally pretty good on the common sense thing, but still a rookie who may not see what you guys deem to be blatant issues…

http://www.estesrockets.com/002456-loadstartm

http://www.estesrockets.com/media/i...56_LOADSTAR.pdf

Possible problems:

* Payload section on crooked or loose and wobbly resulting in unstable flight.
* Motor nozzle damaged - look for chipped nozzle or asymmetrical nozzle - resulting in vectored thrust and unstable flight.
* Igniter plug stuck on motor hook resulting in vectored thrust and unstable flight.
* Motor hook bent 'funny' and protruding into exhaust/nozzle area resulting in vectored thrust and unstable flight.

Got any pics of the rocket's remains, the motor nozzle, and pre-launch photos after igniters were hooked up that you can share? Did you have anything in the payload section?

No pics of the rocket before or after. I also took out the motor as to throw away, so in hindsight that was a big blunder and I should have investigated then. Kind of like one of those guys scratching their head while peering into an open hood on a car; I had no idea what I am looking for, so I did not bother…. I do have the spent motors, so I will peruse through them and see if one of them looks out of sorts. I will also throw in another motor as to check the alignment of the plug. I will take pics if I see something odd. BTW, no payload was in the rocket. I did check, as did the club launch guy as to see if anything was loose, but could have missed something…

I would agree that it is probably an issue with the nozzle. Pre-built models without modification are generally pretty reliable. Since this was a corkscrew as opposed to a spin it would appear that the motor thrust was off the thrust-line of the model so the forward component never got enough flow across the fins to provide stability. I also agree that prior to flight you should check the nozzle of the motor. It should be circular and without damage to the inner rim. Even at the pressures associated with model rocketry an irregularity can produce some pretty spectacular offsets in the flame.

Don't forget that, after all the postmortems many parts of that Lodestar may be salvageable. Specifically, the nose cone and transition should be reusable. And, unless a fin broke off in the crash, the fin can should be too.

One thing I noticed on mine (haven't flown it yet cause I really just bought it as a parts rocket) that the motor mount is off center - it looks as though the centering ring is eccentric to make more room for that motor clip. Looking closer, I can see that the motor tube is obviously canted. See attached photo.

Greg

I'm a bit confused.................corkscrewing and looping are two different things. Did it flip end-over-end during flight, or did it ascend like the threads on a screw? Did it get up to what you would deem to be a normal speed leaving the launch rod?

If it corkscrewed, it's likely an alignment problem, either in the engine nozzle or in the engine mount.

If it flipped end-over-end, it was unstable. You could suspect a number of things, including the CP/CG relationship (unlikely in this case) or a low lift-off speed (probably an engine problem).

I feel that the plastic plug is very likely not part of the problem. Even if the engine hook was able to snag it, which I doubt, it would melt in the engine's exhaust (if it was a normal engine) before it cleared the launch rod.

Joe

I've seen engine hooks catch igniter leads before. If the leads were positively anchored to the launch pad, it could have killed momentum and also caused a deviated flight path. In combination, it could cause the aerobatics. The more marginally stable the rocket, the more likely the aerobatics.

I've had serious nozzle issues in the past, evident in my photos showing significant thrust vectoring. However, there was always enough of thrust for a stable flight. Normally the flight path was altered while the rocket was travelling very slow off the rod, then took a fairly straight flight path as speed built up. Recovery was often done via garbage bag, if you know what I mean. ;)

Visualize a Polaris, Poseidon, or Trident missile launched from under water, breach slowly, then have the solid motor kick in, change directions, and take a stable flight path. I'm not saying all nozzle issues are like this, but I've captured thrust vectoring in still images and with onboard video footage showing stable flight other than the direction change.

Yeah, not sure I am explaining it properly. Upon leaving the pad, you can see it start to corkscrew, then about 30ft up it performs a tight loop (flips end over end); another 20 ft or so, another tight loop; then heads strait to the ground. It was all over the place. It did not appear to have a chance to get up to speed since I noticed it curve immediately upon leaving the pad.

I looked at the engines and saw nothing odd. Also, the issue where the plug hits the engine retaining hook is on my Big Bertha, not this rocket.

Looked at mine and it is perfect. I think next time I need to pay more attention...