Why not "Combat" Model Rocketry?

Back in fifth grade or so, a buddy and I use to be into model rockets. Well one day, while searching my older brother's room for his playboys, we found instead a
great big box of cherry bombs. And with great delight we stole a big handful of them. Then built a bunch of rocket/bombs by simply gluing fins and a launch tube directly to the Estes rocket motor and taping the cherry bomb to the top. And let the ejection charge light the fuse.
We soon realized what fun it would be for us to go to the opposite sides of the field and see who could come closest to hitting the other with our little rocket bombs. It was a blast!
By the time our parents were alerted, we were getting the range down to about fifty feet or so, enough to make it exciting. I wonder, how could we turn that into a sport?
Jonathan
s
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I dunno, but I may have found you a sponsor:
http://www.aopanet.org /
Dave
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Wear Kevlar clothing and a full helmet ?
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Scott M. Kozel wrote:

Sounds like a Kevlar straight jacket might be appropriate
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Jim wrote:

Well, I'll bet you never got into a bottle rocket fight with the girl across the street when you were both around 15, and saw her jump straight into the air when one went between her legs at around knee height. :-D
Pat
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Pat Flannery wrote:

I actually lived in a state where fireworks were illegal so had no access to them, that is a funny concept though. Now I live in Oklahoma where you can buy fireworks and see the amount of damage done every summer via grass fires and pop bottle rockets on wood shingle roofs in 100 degree weather in early July and have developed a bad taste for them unless handled professionally. The model rocket part is great though, have flown my share of them when I was a kid.
Jim
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In Florida you have to sign a waiver that says you own either a fishery or a train company, then you can buy just about anything.
Gotta love this country!
PYROTECHNIC MOTHERLODE Item #: G-042 . Considered the King of the 500-gram fireworks http://www.fireworks.com/fireworks_gallery/photo.asp?pidR7
25 SHOT WOLF PACK MISSILE BASE Item #: L-017 The ultimate missile base! 25 powerful launches that erupt in color and crackle. http://www.fireworks.com/fireworks_gallery/photo.asp?pid 3

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Does anyone else besides me notice how strange the mating rituals get the further west one lives?
;-)
Dave
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David Spain wrote:

The Freudian implications of the incident didn't escape me at the time. :-)
Pat
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writes:

Being from the midwest, I wouldn't know. But the first time I slept with a first cousin I felt real bad about it. Until my buddy told me the way he got over it was to stop counting!

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You might be a redneck....
if you attend family reunions in order to find new dates.
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Scott M. Kozel wrote:>

I never did shoot one at anyone or anything, but I have to 'fess up to putting a explosive impact-fused warhead on a model rocket to try out the detonation system for bombs to be carried on a large RC aircraft at a fly-in. ...worked like a charm. :-) Unfortunately, the actual bombs had such a good aerodynamic form that they would sail hundreds of feet forward from the drop point, and were almost impossible to accurately aim at a target on the ground. Really needed a RC dive bomber for this concept to work, although I did get production cost down to around twenty-five cents per bomb circa 1976.
Pat
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I can't get my wife to attend airshows because she's convinced she'll get killed and now I've got to make sure she never reads this or it will be curtains for RC fly-ins as well. (Not that she'd *voluntarily* want to go to an RC fly-in anyway)...
;-)
Dave
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David Spain wrote:

I've been to a lot of RC fly-ins, and they are a lot more dangerous than any airshow (unless the Russians show up of course; then it seems you can count on a MiG or Sukhoi crashing at some point during the display). The problem is when something goes wrong with the radio, as then you can end up with a aircraft coming out of the sky at over 50 mph with a buzz-saw and chunk of metal at the front. I've had one crash around five feet from me, and another one would have hit my father if he hadn't used the bottom of his shoe to deflect it as it came at him at around two feet in the air.
Pat
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Para-fragmentation... no dive bomber required.
rick jones
--
the road to hell is paved with business decisions...
these opinions are mine, all mine; HP might not want them anyway... :)
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Rick Jones wrote:

K.I.S.S. Tried that concept and with my luck the chute would have opened while the bomb was still on the plane, it would have crashed from the drag, and I'd be in a hell of a lot of trouble with the guy who built it. Except for one that really did have a sizable explosive charge in it, all the other bombs used a very small charge (a shotgun shell primer actually) to eject flour from the back end on impact, for safety's sake. It hadn't occurred to me at the time that what I had designed had the potential to be a fuel-air bomb if the flour ignited after it was ejected. The bombs were very light (around two ounces) and I really didn't expect them to fly that far forward after release. The aircraft used to carry the bombs was a old design called a "Powerhouse" that was quite large and actually covered with real silk. It had a very big low rpm engine on it that actually used a sparkplug instead of a glowplug, and it sounded like a small lawnmower in flight.
Pat
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Scott M. Kozel wrote:

Not for Cherry Bombs...those accouterments must be reserved for M-80s: http://www.fireworksland.com/html/m80.html ...the H-Bomb of fireworks. ;-)
Pat
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I'm beg to differ with this link on two points:      /quote Before you send me an e-mail message arguing that flash powder is a high explosive, here is further discussion of that subject. By flash powder, I mean the chemical composition inside an M-80, which is a mixture of various substances, including potassium perchlorate. The scientific community defines a high explosive as one that detonates when unconfined. A low explosive is defined as one that deflagrates - not detonates - whether confined or unconfined. The distinction between "detonate" and "deflagrate" is the key difference here. A low explosive, that deflagrates, generates pressure waves in the air that are slower than the speed of sound, while a high explosive, which detonates, generates pressure waves that are higher than the speed of sound /endquote
1st point:
Deflagration and detonation refer to the speed of reaction through the explosive itself, not the blast effect through the air.
'Slow' explosives deflagrate, the reaction progresses through the material at a speed below the speed of sound through that material.
'Fast' explosives aka superexplosives, allow the reaction to progress at the theoretical maximum speed, the speed of sound through the material.
IIRC, black power is an example of a slow explosive, (well explosive when confined).
Nitroglycerin, PETN and RDX fall in the super-explosive class.
2nd point: 'Generates pressure waves that are higher than the speed of sound?'
Eh?
Dave
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David Spain wrote:

The only thing I can think of in this regard is Primacord, a super fast burning detonating cord used for high explosives that burns at a rate of 7,000-8,000 m/s: http://en.wikipedia.org/wiki/Detonating_cord ...which seems a lot higher than the speed of sound in the material it's made from, which is a variable that depends on density. That would mean it's burning at around 16,000 mph, which seems high for sound, even going through solid lead.
Pat
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I gotta learn to stop posting based on recollection.
I WAS WRONG. Well sort of...
I quick review of what's available on the Internet delineates between between the shock wave that initiates the chemical reaction vs the chemical reaction itself.
The 'detonation wave' can proceed through the material at supersonic speed (relative to the material). It physically displaces (compresses) which heats the reactant which then reacts sonically after the 'shock discontinuity' wavefront passes. [1]
The speed of the detonation wave is aided by an increase in the density of the material. According to US Patent 4913053 Primacord uses a process of heating and high pressure to boost the detonation velocity of the fusing by 15-20% [5].
Technically its not 'burning' or reacting at that speed, and again taking a risk IIRC, that is why there's no discernible flame front in a detonation as opposed to a deflagration. The chemical reaction happens after the supersonic shock wave passes through the material which would make it appear to be 'burning' (aka reacting) all at once.
To pick this apart a bit I focused on one type of explosive, RDX and came up with this:
Explosive velocity: 8750 m/s [2] Speed of sound in RDX: ~3300 m/s [3], [4]
Thus the shock wave propagates through the material at roughly 2.65x the speed of sound in the material.
Sources:
[1]'Toward Detonation Theory' by Anatolii Nikolaevich Dremin page 4 para 3 a description of ZND theory.
http://books.google.com/books?id=pZLdfT-NZ-wC&source=gbs_navlinks_s
[2] http://en.wikipedia.org/wiki/RDX
[3] Molecular Dynamic Simulation of Nanoindentation of Cyclotrimethylenetrintramine (RDX) Crystal
http://www.mrs.org/s_mrs/sec_subscribe.asp?CID 52&DID 1139&actiontail
Google search of 'speed of sound in RDX crystals' yields a reference to this paper with the quote 'the indentation speed is 200 m/s which is 6% of the sound speed in RDX' this calculates to 3,333 and 1/3 m/s.
[4] The elastic constants and related properties of the energetic material cyclotrimethylene trinitramine (RDX) determined by Brillouin scattering by Haycraft, Stevens and Eckhardt.
http://digitalcommons.unl.edu/chemistryeckhardt/2
See the sound velocity diagrams in Fig 3. I noted the logitudinal mode curves, esp. the ones from the ultrasonic works of Scwartz and Hassul which are in close agreement at around 3300 m/s.
[5] US Patent No. 4,913,053 McPhee for Western Atlas International Houston TX. 'Method of increasing the detonation velocity of detonating fuse'
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&lP&co1=AND&d=PTXT&s1I13053.PN.&OS=PN/4913053&RS=PN/4913053
--
Sorry,
Dave

PS: And boy, if this post doesn't end up on a NSA server somewhere,
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