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  #11  
Old 10-08-2012, 10:00 PM
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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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  #12  
Old 10-08-2012, 10:05 PM
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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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  #13  
Old 10-08-2012, 10:06 PM
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Quote:
Originally Posted by Mark II
Interesting that you mentioned a low staging altitude, Tim. My old Astron Midget, had the strangest flight profile in its only launch in 1970.

Of course I don't remember the motors that I used in it that day, because I never logged anything back then, and any physical remains from that era in my rocketry career are long gone. But after looking through the old Estes catalogs, I think that I used a 1/2A6-0S in the booster and a 1/2A6-4S in the sustainer.
I think that's the combo I used with my Midget on the only 2 stage flight of phase one of my rocketry career.

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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  #14  
Old 10-08-2012, 10:09 PM
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Quote:
Originally Posted by Mark II
My father caught me as I tried to slip out of the house with my Electro Launch and my Midget, but instead of forbidding me to launch it he decided to accompany me "in case you get arrested." It was the only rocket launch of mine that he ever witnessed.
Mark, I've heard you express your frustration with your parent's lack of support for the hobby back then. But, reading this bit, it occurs to me that your dad may have simply not realized just how special it was for you.

Doug

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  #15  
Old 10-08-2012, 10:10 PM
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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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  #16  
Old 10-08-2012, 10:12 PM
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Quote:
Originally Posted by Doug Sams
Mark, I've heard you express your frustration with your parent's lack of support for the hobby back then. But, reading this bit, it occurs to me that your dad may have simply not realized just how special it was for you.

Doug

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Eh, it was just something that I dealt with. I thought that all or at least most parents had that attitude toward model rocketry.
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  #17  
Old 10-08-2012, 10:14 PM
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Quote:
Originally Posted by Bill
Too bad that did not get him hooked on the hobby...


Bill
No. In fact, I think that it confirmed some of his fears.
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  #18  
Old 10-08-2012, 10:17 PM
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Quote:
Originally Posted by Bill
I just love that upscale ratio. Big enough to be impressive; not so big as to be too big. And plenty of commercial tubes of the right size.


Bill
What helped was that Semroc just happened to have an upscaled BNC-50J in that size. The scale factor worked out so that LT-115 (a k a 29mm motor tube) was just the right size to replace the original BT-20 in the booster stage.
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  #19  
Old 10-08-2012, 10:18 PM
A Fish Named Wallyum A Fish Named Wallyum is offline
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Quote:
Originally Posted by Mark II
Eh, it was just something that I dealt with. I thought that all or at least most parents had that attitude toward model rocketry.

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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  #20  
Old 10-08-2012, 10:22 PM
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Quote:
Originally Posted by Mark II
So what happened? What caused that strange flight?
Mark,

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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Last edited by Doug Sams : 10-09-2012 at 09:58 AM.
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