Pyrotechnic Literature Series - Shimizu - Part 1
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Selected Pyrotechnic Publications of Dr. Takeo
Shimizu,
Part 1 (1985 to 1994) from the International Pyrotechnic Seminars
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Table of Contents (Shimizu - Part 1)
| Abstract: First, we hypothesize
that a serious accident related to the use of salutes may be caused
by the simultaneous explosion of several salutes or salute components,
resulting in an unexpected, abnormally strong shock wave. To prove
our theory, we conducted three experiments. In Experiment 1, we examined
the transfer of the explosion between salutes with one donor to shed
light on the properties of the charges. Experiment 2, which we conducted
to examine the transfer in the case of two donors, revealed a localized
effect of the transfer. In Experiment 3, we measured the pressure
during explosion using a pressure-sensing film, which was used to
create pressure contour lines. Our experiments reveal that there is
an area of abnormally high pressure, a finding which supports our
hypothesis. Proceedings of the 10th International Pyrotechnic Seminar, July, 1985. |
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| Reprint Information: Number of pages = 10. | |
| Abstract: In general, a
pyrotechnic composition consists of an oxygen donor such as KNO3,
KClO3, or KClO4, etc., an oxygen donee such
as organic resin and some other inert substances. When substances,
CaCO3, AlO3, SiO or CaSO4,
etc. are contained in it, they are regarded as an inert substance,
because they are full of oxygen and cannot be more oxidized. This
type of explosive deflagrates with oxidation reaction and could be
called "positive explosives". However, when some substances,
Mg, Al or Si, etc., which have a very large reduction capacity, the
inert substances change to active ones. This type of explosives, which
consist of Mg, Al or Si, etc., plus a substance which is thought to
be inert in conventional explosives, is defined here as "negative
explosives". With the oxygen donee, Mg was concerned as a representative
case, because it is very popular and has the largest reduction capacity;
it burns even sand or earth. About 50 types of negative mixtures were
listed as samples. Their characteristics were examined by several
tests. Ignition and burning properties were tested on the ground by
using black match. Ignition temperatures were obtained from a heating
test in a glass tube. Illuminating capacities were measured by burning
consolidated mixtures as a flare. Ballistic characteristics were examined
by firing a projectile with a small mortar by using granulated mixtures
for the propellant charge. The results were discussed and a proposal
for use of negative explosives was made. Proceedings of the 11th International Pyrotechnics Seminar, July 1986. |
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| Reprint Information: Number of pages = 11. | |
| Abstract: Heretofore we
have had four important problems with calculations in this field,
i.e., with the interior ballistics when using Black Powder as the
propellant: (1) to obtain a suitable form function of the propellant
which consists of irregular grains, (2) to obtain solutions when the
burning rate of the propellant grains is proportional to P(, where
P is an internal pressure of the mortar barrel and ( the pressure
exponent, (3) to obtain suitable solutions when the propellant gas
escapes from the burning room through the clearance between the wall
and the shell in the mortar, and with the exterior ballistics (4)
to obtain simply the drag coefficient for various shapes of shells.
For (1) a treatment to calculate the surface areas and volumes of
grains assuming the propellant grains consist of a mixture of cubes
and spheres is proposed. For (2) a method to solve a three order differential
equation derived from three basic interior ballistic equations step
by step with proper time intervals is proposed. For (3) the nozzle
theory used for rocket engines is introduced. For (4) the fact that
the maximum height of the projectile in the air is almost the same
as that of vacuum when the flying times of the both are equal is applied.
These methods are applied to 6-inch shells and examined if they are
suitable in practice. Proceedings of the 13th International Pyrotechnics Seminar, July 1988. |
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| Reprint Information: Number of pages = 11. | |
| Abstract: At
the Eleventh International Pyrotechnics Seminar, 1986, in Vail, Colorado,
I reported on a study of pyrotechnic mixtures with a theme, "A
Concept and the Use of Negative Explosives". A further study
has been continued on the same subject as before. In the former report
it was known that magnesium sulfate/magnesium mixture detonates on
heating. I studied if it is suitable for the noise mixture of fireworks
in place of the ordinary one which contains aluminum and potassium
perchlorate and which has long been a cause of serious accidents in
the firework industry. The chemical reaction of the magnesium sulfate/magnesium
mixture on detonation is thought to be: MgSO4 + 4 Mg =>
MgS + 4 MgO + 353 kcal. From several experiments following results
were obtained: (1) The intensity of the explosive noise from the magnesium
sulfate/magnesium mixture is almost the same as that from the ordinary
aluminum mixture when the weight of the charge of the former is two
or two and a half times as large as that of the latter. (2) The magnesium
sulfate/magnesium mixture is far more safe on handling than the ordinary
aluminum mixture. It was proved by an iron ball dropping test and
a fire propagation test. (3) The tone quality of the noise from the
magnesium sulfate/magnesium mixture is mild and superior than that
from the ordinary aluminum mixture. (4) In practical use it is necessary
to protect the noise unit which contains the magnesium sulfate/magnesium
mixture from moisture. Proceedings of the 15th International Pyrotechnics Seminar, July 1990. |
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| Abstract: The objective
of this work was to make clear the effect of hot spots or hot spot
materials on burning pyrotechnic compositions and to find practicable
strobe light compositions without ammonium perchlorate which is not
always popular in the firework field, using the effect of hot spot
materials. As the hot spot materials, four types, Japanese oak charcoal,
red iron, red lead, and potassium dichromate were selected from many
substances. The effect of each was examined by burning tests of compositions
which contained rosin, usual oxidizers (ammonium perchlorate, potassium
perchlorate, and potassium nitrate), and a small quantity of each
hot spot material. In this case, the effects did not clearly appeared
except that of potassium dichromate, which promoted the burning rate
of compositions in fairly large extent. Secondly, the effect of red
lead and potassium dichromate was examined with compositions which
consisted of magnesium, guanidine nitrate, and metal sulphates, which
had been thought to be suitable for strobe lights. From the results
of experiments, examples of four colored light compositions are shown
for practical use. It is concluded that the effects of hot spots are
not so clear, when using with compositions which contain usual oxidizers.
However, when using with the compositions for strobe light, which
do not burn so easily, the hot spot materials are very effective in
adjusting the strobe reaction and to obtain the compositions in practical
use. Proceedings of the 16th International Pyrotechnic Seminar, June, 1991. |
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| Reprint Information: Number of pages = 7. | |
| Abstract: In the past we
sometimes observed a fairly large burning star caused an explosion
with a loud noise at the very moment when it fell onto the ground.
The star did not explode totally, but only with the thin surface layer.
The burning surface layer of the star may be very sensitive to shock
because of the high temperature. This phenomenon is here called the
"surface explosion." The objective of this paper is to investigate
the surface explosion by experiments. It may be very important to
make clear the mechanism of the transition from burning to explosion
or detonation not only with pyrotechnic mixtures, but also with general
explosives, especially to avoid accidents. The mechanical sensitivity
of the burning surface layer was examined by dropping an iron ball
onto it with consolidated mixtures of ordinary stars and illuminants,
etc. Most of them showed a higher sensitivity than that of a standard
mixture called red explosive at ordinary temperatures. Using small
rocket engines, propellant of potassium chlorate and potassium perchlorate
comparing with that of ammonium perchlorate were examined. The former
two caused the surface explosion or a perfect detonation when ignited
and the rocket engines were broken, and only the propellant of ammonium
perchlorate worked well. The phenomenon of the surface explosion was
discussed in combination with a past accident. Proceedings of the 18th International Pyrotechnics Seminar, July 1992. |
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| Reprint Information: Number of pages = 9. | |
| Abstract: These studies
concern two important problems at present: one is how to select the
component materials of a mixture not to cause degeneration, and another
is to find a more effective method of magnesium coating than those
at present. A firework mixture generally consists of several solid
materials which are closely in contact with each other. The state
is not so much natural as artificial. Therefore, the mixture often
causes chemical degeneration to remove into a more stable state which
is opposite to the purpose. The direction of the change has been unknown
without experiences. It has been a great difficulty on selecting materials.
I have found a rule to foresee the direction: the component materials
in a mixture gradually decomposes with each other to create the most
water insoluble material. This tendency should be called the "minimum
solubility law". A table was prepared to foresee the direction
of the degeneration reactions arranging materials in the order of
their solubilities. When a magnesium flake is soaked in a solution
of dichromate and sulfate, the flake is gradually coated with a thin
black film. It may be CrO2 and have a high corrosion resistance. The
effect was tested with several dichromates and sulphates against mainly
ammonium perchlorate using magnesium ribbon and powder. In addition
an effect of guanidine nitrate on the coating was observed because
it gave a good result of corrosion resistance when it was used as
a blinker (strobes) in the past. Proceedings of the 19th International Pyrotechnics Seminar, February, 1994. |
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| Reprint Information: Number of pages = 13. | |
| Abstract: It
has been generally believed that the finer the grain size, the faster
the burning when we select the component materials of a pyrotechnic
mixture. It is not always true because a small explosion occurred
in the past when we tested a smoke mixture, although it contained
a dye of very coarse grains. The purpose of this paper is to make
clear the general mechanism of the burning rate of pyrotechnic mixtures
on the standpoint of the grain size of component materials of pyrotechnic
mixtures. Experiments on burning rate were carried out with four types
of mixtures changing the grain size of the component materials: (a)
base mixtures of oxidizer (conventional materials as potassium chlorate,
potassium perchlorate or ammonium perchlorate) and fuel (accroides
resin), (b) mixtures of the base and an inert material (clay), (c)
mixtures of the base and a semi-inert material (barium nitrate), (d)
mixtures of an explosive of synthesized simple substance (potassium
picrate) and an inert material (clay). All the materials except potassium
picrate were sieved to obtain grains of six class sizes. With decreasing
the grain size of the component materials, some mixtures increased
and some decreased the burning rate. In other cases there were grain
sizes which gave the smallest burning rate: the burning rate at first
decreased and then increased. In general, the burning reaction seemed
to be stabilized as the grain size decreased. These effects will help
the designing of pyrotechnic mixtures for various purposes. Proceedings of the 20th International Pyrotechnics Seminar, July 1994. |
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1775 Blair Road Whitewater, CO 81527 USA
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