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Originally Posted by Newbomb Turk
I'm inclined, knowing the conditions at flight time, to think GH might be right. If the A10-0T does in fact have enough oompf to power the design, perhaps this particular A10 was a less than perfect product.
Our LCO is a Physics PhD. His immediate reaction was that it didn't have enough thrust.
Note the damage sustained by the second stage upon impact with the ground under power.
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Well...at least you have more hardware to examine to hopefully determine the cause (pity the incident investigators who have to determine why ballistic missiles or space launch vehicles fail--while they [usually] have telemetry data, they either have no hardware at all, or--unless they're very lucky--just tiny fragments or shards to examine). Here (see:
www.youtube.com/watch?v=g9Dbfa0V38s ) is another "gravity turn" Mini Commanche-3 flight. Also:
I'd check the nozzle for unusual (excessive), asymmetrical erosion, as tbzep suggested. In addition, examining the ablation on the inside walls of the motor might reveal some unusual pattern, that could point to poor or incomplete (in the usual thrust duration time) combustion of the propellant. I suppose that from time to time, a batch of black powder may be "sour" (Estes sometimes buys it from overseas suppliers, which could provide opportunities for excessive amounts of moisture, dust, or some other impurity to find its way into it, despite precautions). If a motor containing such "sour" black powder burned even 15% - 20% more slowly than it should, the amount of thrust produced each second could be low enough to result in the crash that your Mini Commanche-3 suffered. As well--to mention something more cheerful, after looking at your posted pictures:
The lower two stages' fin spans look large enough to make them gliding stages, like the Centuri Black Widow kit's gliding first stage. While two of the three fins on each Mini Commanche-3 lower stage could--like the fins on the Black Widow's first stage--be spaced either *less* than 120 degrees apart (as in the early version, see:
http://plans.rocketshoppe.com/centu...B-6/cenKB-6.htm ) or *more* than 120 degrees apart (as in the later version, see:
http://www.spacemodeling.org/jimz/kb-6.htm ), there is a way to space the Mini Commanche-3's lower stages' fins normally (120 degrees from each other), yet have each lower stage glide (which would be more spectacular, while also making them easier to track [because they would remain aloft longer than tumble recovery lower stages]):
The early "Mini-Bird" boost-gliders (which appeared in either the First, Second, or Third Edition of G. Harry Stine's "Handbook of Model Rocketry") were very similar to the lower stages of multi-stage model rockets. A typical Mini-Bird looked like, say, an Estes Alpha, with a body tube (usually--but not necessarily--minimum-diameter) no longer than the motor, and with a nose cone glued into the front end of the body tube. The fins were spaced 120 degrees apart, and one fin (the "bottom" or "centerboard" [as in a sailboat] fin--was either slightly longer in span than the other two fins, ^OR^:
The "bottom" fin could be of the same planform as the other two, with ballast weight applied to its tip). After the motor (or the motor mount; either could be streamer-recovered, to make Mini-Bird BGs "NAR-Kosher" for contest flying) ejected itself from the model, it settled into gliding attitude. The two lower stages of the Mini Commanche-3 could be modified slightly--in either of the two above-described ways--so that they would glide like Mini-Bird boost-gliders (in the case of minimum-diameter multi-stage models such as the Mini Commance-3, the spent motors would remain inside the lower stage airframe or airframes, as with the Centuri Black Widow's lower stage). As well:
For multi-stage models with *larger*-than-minimum-diameter body tubes, the lower stage's (or stages') motor mount tube(s) could eject themselves rearward (each lower stage's forward stage coupler would act as a thrust ring for the motor mount), and descend under steamers. The "middle" lower stage (the second stage, when all three stages are used) of the BT-50 size Estes Commanche-3 (see:
https://estesrockets.com/wp-content..._COMANCHE_3.pdf ) could use the rear-ejecting, streamer-recovered 18 mm motor mount with a "Mini-Bird modified," gliding second stage (the C11-0 or D12-0 powered first stage could--like the Centuri Black Widow's gliding first stage--retain the spent C11 or D12 motor casing, and--like the Commanche-3's second stage--also incorporate the Mini-Bird modifications, so that it too would glide).