Chemistry & Science
Experiments

Aerial Bombs

An Aerial Bomb is basically a tiny
mortar that shoots M-80 high into the air, exploding at it's maximum
height.
The Aerial Bomb is composed of two main parts, the mortar (launch
tube) and the projectile, in this case an M-80 salute.

The Projectile

The projectile for
the Aerial Bomb is a small 1-1/2" Flash Powder salute in an M-80 casing. The
only difference between this salute and an M-80, is that the salute for the
Aerial Bomb must have its fuse protruding out of the end of the case (so it will
fit in the mortar), and not from the side, as it does in an M-80.
Normally,
for larger aerial salutes & shells we would use Japanese Time Fuse for the
delay, but because of the size of this device, the fact that the projectile is
not launched very high, and that timing is not critical (as it is in a star
shell), we're going to use ordinary Visco Safety Fuse as our time delay fuse.
The way the fuse is cut and its placement are fairly critical, so do not modify
them in any way.

Take
a 1-1/2" piece of Visco Fuse, and using only a razor blade, cut one end in a
sharp diagonal. This is done so it will expose a larger amount of the black
powder core inside the fuse and insure that it will ignite during launch. Do not
cut the fuse with a scissors or similar tool. A scissors does not make a clean
cut and actually crushes the powder core & closes the fuse end at the same
time, making ignition much less reliable. There is no need to cut a diagonal on
the other end of the fuse.

Drill a 1/8"
hole in one of the M-80 end plugs.

This end plug is
going to be the bottom of the M-80, and to make it strong enough to withstand
the blast of launching it out of the mortar, we're going to use it backwards in
the tube and reinforce it. To do this, press the end plug in one end of the M-80
tube, and using a small stick or pencil, push the plug all the way to the other
end of the tube, leaving 1/4" of space above it.

Insert the
1-1/2" piece of fuse (with the diagonal end sticking out) so about 1/2" is
outside the tube.

Stand the tube
up, and fill the empty space with Elmer's White Glue. This will have to dry at
least several hours, or possibly overnight before you can continue. It is
possible to use Hot Melt Glue in place of Elmer's at this point if you're
impatient, then you need only to wait until the glue cools, which should be in
about 10 minutes or so. It should be noted however, that we have had a few
misfires using Hot Melt Glue and Elmer's is really the better choice. It's
possible that under the right conditions the  molten glue surrounding the
fuse effects the powder core in some way. In any case, if you're just too
impatient to use Elmer's, and going to use Hot Melt Glue, be sure to use a
low temperature gun and low temperature glue
sticks.

After the glue
is dry, flip the M-80 over and fill it 3/4 of the way with Flash Powder. If you
add a pinch of granulated Titanium to your Flash Powder, the explosion in the
air will be accompanied by an attractive  blast of white sparks. Proper
instructions for making Flash Powder can be found by Clicking
Here.

Smear some
Elmer's Glue around the lip of the tube and press in the other end plug. Push
the plug into the tube so there's about a 1/16" gap between the tube end and the
plug edge. This is just so we've got another anchor point for more glue between
the tube and plug. Smear a good quantity of glue around the rim so the end plug
will be locked into place. This end of the tube must be glued with Elmer's and
not with Hot Melt Glue. Since the glue layer is not very thick, it will not take
that long to dry.

Set the
completed M-80 projectile aside to dry.

The Mortar

The
Mortars for the Aerial Bomb come in 2 pieces, a small plastic base, and a heavy
wall launch tube. Morons must make these thing because we've never seen a tube
actually fit well in a plastic base. Test fit the two pieces and see if they
will it together. Chances are that they won't, so take a file and just file a
bit off the edge all the way around the tube so it's possible to press it into
the base.

Now take your
1/8" drill, and make a hole 3/4" from the bottom of the tube. This will be the
fuse hole.

Spread some
Elmer's Glue around the indent in the base and press the tube into the base
firmly. Make sure that the tube is pointing up straight from the
base.

Cut a 3" piece
of Visco Fuse and insert it all the way into the hole. Spread a little Elmer's
around the hole to hold the fuse in place.

Pour in a 1/8
TEASPOON of Granulated Black Powder into the mortar. Instructions on making
Granulated Black Powder (Lift Powder) can be found by Clicking Here. You can
also use commercial 2FG or 3FG Black Powder if you don't want to make your own.
You CAN NOT substitute Flash Powder for the Granulated Black Powder.
Black Powder burns slow, and even slower when it is granulated. We want to
gently (but quickly) launch the projectile out of the tube and ignite the delay
fuse. If you were to use Flash Powder (in any amount) in the launch tube it
would detonate and destroy the mortar, and also detonate the M-80 on the ground.
Flash Powder burns much too fast for doing anything other than making something
explode.

Push your
M-80 projectile (fuse first) all the way down into the mortar. The M-80
should slide easily down into the tube, you should not have to force it. When
completely dry, the completed Aerial Bomb will be ready for use.

Operation

When the fuse it
lit, the Granulated Black Powder ignites, shooting the M-80 up into the air. At
the same time, the flame from the lift charge ignites the delay fuse on the
M-80. When the fuse burns out, the M-80 explodes making a nice report in the
air.
Remember that for every action, there is an equal & opposite
reaction. This means that the same amount of force that is shooting the
projectile up in the air, is pushing back down on the mortar tube... so make
sure the device is on solid, flat ground.
Like everything, the Aerial Bomb
may require some fine tuning. If the projectile is exploding too low, add more
Black Powder to get it higher. If it's exploding too high, cut down on the Black
Powder a bit.
Don't even think about holding this in your hand and lighting
it. It is always possible for the M-80 to detonate before it gets launched, and
if it's in (or near) your hand at the time, it will take it right off at the
wrist. We then get to write "Stupid" on your forehead, call you "Stumpy", and
laugh at you for the rest of your life.