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
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
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
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
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!
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
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
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
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
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
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
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&actionÞtail
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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