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I've had rockets backslide before ejecting, but never before staging! The Aerobee comes very close to stopping when it stages on the A8-0, but doesn't backslide.
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I love sanding. |
#12
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I've been working on a BT-60/Bt-70 version with slightly different fin shapes that I call "the Troll". It flew nicely on D12-0/D12-7 and C11-0 and C11-7 combinations. On the 6th flight it failed to stage, forcing the BNC-80BB halfway down the sustainer body tube!
Engines were not right up to each other, but the gap was less than 1" On "the Troll" 2.0 both engines will be closer and both will use engine hooks. The 1.0 used an engine block in the bottom of the booster to prevent engine kickout. this seemed to cause a bit of a venturi effect with a resulting loss of thrust. The maiden flight was in Lafayette with the local TRA boys back in January. Staged beautifully, and the booster went into a glide-nicer than anything I ever got from any Black Widow booster I ever flew! Unfortunately it glided right into the side of the club's trailer, with parts going everywhere! Seems the epoxy I used didn't like the 16 degree F. weather.
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"If you want my view of history, there's something you should know. The three men I admire most are Curly, Larry, Moe!" Meat Loaf |
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We had scoured the old Estes catalog for stuff to add to our setup and had purchased the old extension section for the rod that had come with our starter set. That brought the rod to about 4-1/2 feet. In my mind, it seems the Midget was barely above the rod when it staged. My next 2-stage flight was that same Midget in 1999 on an A10-0T booster. In that case, it went very high - the booster seemed to burn forever. (It was the flight that has had me hooked ever since!) I later repeated the first flight using another vintage 1/2A6-0S. It too seemed to be barely off the rod before it staged. It was more like a 1/4A, IMO. Anyway, that 1999 flight is what made me into a Midget aficionado. Doug .
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YORF member #11 |
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Doug .
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YORF member #11 |
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So what happened? What caused that strange flight? I have pondered this question over the past 42 years. For the longest time I thought that the booster motor must have just been underpowered. That was the explanation that fit with my experience. My Alpha, in its first flight (my very first as a rocketeer) had struggled to reach 40 feet on a 1/2A motor, and had fallen all the way back to the ground before the ejection charge fired. Because of that I was always wary of using motors at the lowest end of the power range. But my experience since then has caused me to question that explanation.
A 1/2A (or was it an A?) shouldn't have acted like that. My new hypothesis is that the cellophane tape that I used had caused the two motors to have difficulty separating at staging. Perhaps in addition it may have also caused the two stages to refuse to separate at first. What I think happened was that staging had occurred right about when the Midget reached treetop level, right before it slowed down and stopped in midair. But the booster didn't drop off, possibly because the motors couldn't separate. The sustainer motor struggled to haul the whole assembly skyward but couldn't because its thrust was attenuated by the fact that it was firing down through the spent booster motor. The Midget was stable enough (in the dead calm air) and there was enough thrust coming out that the whole assembly remained upright while gently backsliding like a Lunar Module. But after a few feet of descent the tape finally broke, freeing the booster and allowing the sustainer to shoot off. What is amazing was that it still had enough impulse left at that point to apparently get to descent altitude.
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Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic • Advice Unsullied by Erudition • Rocketry Without Pity
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Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic • Advice Unsullied by Erudition • Rocketry Without Pity
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Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic • Advice Unsullied by Erudition • Rocketry Without Pity
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#18
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Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic • Advice Unsullied by Erudition • Rocketry Without Pity
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#19
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Yeah, my Dad was completely disinterested. Other than sports we had very little in common, and he really didn't enjoy watching me play because of the difference in our "styles".
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Bill Eichelberger NAR 79563 http://wallyum.blogspot.com/ I miss being SAM 0058 Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Gee'Hod, Shrike, SST Shuttle In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Solar Sailer II Semroc Cyber III Ready to fly: Estes - Multi-Roc, Solar Sailer II Semroc - Earmark, Snake Jumper |
#20
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I think the old 1/2A6's were nearer 1/4A's than 1/2A's. I've heard that stated by others such as Bob Kaplow. And my experience with vintage 1/2A6's has been consistent with that. Which means that the K-40 two-staged flight was marginal. And any malfunction - any shortcoming at all in the booster - would likely result in a very exciting situation. I think that's what you witnessed - a small malfunction of that old 1/2A such that the flight became very interesting! Doug .
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YORF member #11 Last edited by Doug Sams : 10-09-2012 at 09:58 AM. |
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