#21
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Something was definitely "foul" with the propellant combustion.
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When in doubt, WHACK the GAS and DITCH the brake !!! Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't ! Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY. ALL systems are GO for MAYHEM, CHAOS, and HAVOC ! |
#22
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Interesting. I’ve only flown a 13mm stager once, my scratch-built Double Mini Max. It was A10 to A10. It flew pretty well, but not the roaring liftoff I expected. Upper stage flight angle was not perfectly vertical, but it’s a gap-stager, so I suspect it may have had a bit of arc-over before upper stage ignition. Recovery was fine. If I were to build another, I’d go 18mm booster. The extra length of an 18mm booster would be no issues since I used at least an inch of gap in the design. A similar difference in motor average thrust exists with the 18/20 RMS D reloads. Probably a lot more examples, but I noticed this because I bought the 18/20 specifically for the Mars Lander. I thought the D24 might be too much, so I bought the D13 also.Then I looked closer at the thrust curves. The D13W is rated 12.67 N average thrust, the D24T is 14.77 N. The thrust curves are very similar. I’ll try the D24 next flight. I’ve flown it twice on D13 with excellent results.
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Lee Reep NAR 55948 Projects: Semroc Saturn 1B, Ken Foss Designs Mini Satellite Interceptor In the Paint Shop: Nothing! Too cold! Launch-Ready: Farside-X, Maxi Honest John, Super Scamp |
#23
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No doubt, you want a lot more than 4 AA's Doug .
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YORF member #11 |
#24
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It seemed like that booster burned forever - finally the sustainer lit and the flight was 100% successful. I was totally psyched by it - I've been a staging fiend ever since Doug .
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YORF member #11 |
#25
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I had the same idea when I viewed the pictures of the spent first stage motor. My first thought was moisture damage after seeing the pictures of the nozzle and casing.
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Bruce S. Levison, NAR #69055 |
#26
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#27
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__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#28
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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).
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
#29
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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.
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I love sanding. |
#30
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I would never have suspected that such "off-center-burning grain" composite motors would have exhaust plumes that would actually mirror--in the rockets' flight characteristics--the internal ballistics of the burning grain inside. Maybe a sufficiently-long nozzle (or even a provided jetavator) would eliminate that, without really hurting the motor performance enough to matter.
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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see: http://www.lulu.com/content/paperba...an-form/8075185 http://www.lulu.com/product/cd/what...of-2%29/6122050 http://www.lulu.com/product/cd/what...of-2%29/6126511 All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com. NAR #54895 SR |
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