Click
Here to see a QuickTime movie (File size 231kb) of a black powder
rocket launch with reaction from some bystanders. (This video was shot at
the 2000 WPA
Western Winter Blast. Free Quicktime player available here.)

This page deals with general info, mixing the
comp, the construction
of a black powder rocket using your rocket tool set, as well as
'sticking' and fusing the rocket.

This web site  is prepared for purposes of education only.
If you want to read these pages for an understanding how rocket propellant
systems are physically made and how they fly, then this should suffice. We
assume no responsibility for the use of this material by any person. If
you attempt to use any of these materials in order to make devices, you
should be in compliance with all laws and regulations and observe the
maximum possible safety precautions.

Why a Black Powder (BP) Rocket?

Easy to obtain chemicals

BP is a well known and fairly predictable product

Easy to work with

Fairly forgiving ? given sensible safety issues.

It can be quite spectacular!

Considerations for BP:

BP rockets tend to lift off of the pad at a slower pace than whistle
rockets.

Max altitudes tend to be lower. (Not all the time!)

Hand made BP burns at a much slower rate than commercial or meal BP.
This is not a bad thing. (When using meal, it is recommended to slow the
mixture down ? refer to formula table.)

How a BP Rocket Works

The comp is burned in a core-burning fashion ? from the inside
to the outside - along the length of the hole (made by the spindle) in
the fuel. Material then burns during the coast stage in an end burning
fashion, releasing spark but not attributing too much to lift. Ideally,
enough material is present to allow the rocket to coast to apogee -
there fire is passed to your payload.

Tubes and Sticks

Tube size ration:

Tube ID = 1

Tube OD = 1.25 to 1.50 ID

Tube Length = 10 ID

Note all ratios deal with the ID

The following table should help you decide what kind of sized tooling
you will need.

Rocket Size

ID

OD

Length

Min Stick Length*

Payload Weight*

8 oz.

5/8" (.60")

1"

6 1/4" (6.25")

30"

120 grams

1 lb.

3/4" (.75")

1 1/4" (1.25")

7 1/2" (7.50")

36"

180 grams

3 lb.

1"

1/5" (1.50")

10"

48"

500 grams

*Stick lengths and payloads are general recommendations. Longer
sticks will cause the rocket to be more stable, but detract from the
payload weight. Sticks are around 1/4? to 3/8? wide ? stout enough so
they don?t snap when you hold the rocket (with payload) up by the end of
the stick. Cut sticks shortly before using them to avoid warpage.

Tubes can be ordered from many sources. Check out our friends at Skylighter.com for an up-to-date list.

Nozzle Material

Can be many different materials. It must be able to withstand the
abrasive effects of the gas jet, but easy to deal with and not damage
your tooling.

Material

Pluses

Minuses

Bentonite Clay or Fire Clay

- Cheap, easy to obtain
-
Effective

- Subject to
erosion, esp. on larger rockets

Kitty litter (added to clay 50%)

- Cheap, easy to obtain
- More
effective than clay alone

- Some prep work

Wax added to kitty litter/clay or 'clumpless' kitty
litter

- Makes clay 'stickier'
- Much more
effective than clay alone

- Requires preparation

Durhams Water Putty

- Excellent
erosion resistance

- Requires
preparation before ramming and drying time after
ramming

MIXING THE COMP

Chemicals

Sulfur

KNO3 - Potassium Nitrate (K-Power fertilizer)

Air float charcoal

Large grain charcoal (80, 36, 20 mesh - depending on your taste)

Formulas

The three major components of Black Powder can be mixed and used dry.
This method is somewhat dirty, but is quick and easy to do. The mix can
also be wetted down or have a binding agent added to reduce the amount
of dust. (This will slow the burn rate down.)

Although BP has been around for many years, there are still quite a
few folks that have their own unique mix percentages. The percentages
given here are for general purposes. BP is quite forgiving, and volumes
don't have to be exact down to the very last gram. (But it helps!) BP
Rocket fuel burns quite slowly. (If you use meal BP, you will need to
slow it down!)

Note: All numbers are in percentage of
total weight.

Separate Ingredients in %

Range

Typical

Potassium Nitrate (KNO3)

55-70

60

Charcoal (mixed)

25-35

30

Sulfur

5-15

10

Formulae (in %)

8 oz.

1-2 lb.

3-4 lb.

Tom's 1 lb. Mix*

Potassium Nitrate

60

60

60

70

Sulfur

10

10

10

10

C - Air float

15

10

10

10

C-80 mesh

10

15

15

C-36 mesh

5

5

C-20 mesh

20

(* So it adds up to 110%. If the formula works, who says it needs to
be 100%? Do you really want measurements to look like 63.6%? Didn't
think so.)

[Webmaster note: I developed 'Tom's Mix' to give a tall column of
spark. This formula results in a rocket with a slow takeoff, a huge
pillow of spark on the ground, and a column of that will last, so when
the rocket delivers it's payload you can follow the tail all the way
back down to the ground. Depending on your taste, make your own
variants! This works best for 1lb rockets. Larger rockets may need to
have the KNO3 backed down.)

The strength of the formula can be adjusted by changing the ration of
air float (more = faster if you subtract larger charcoal), meshed
charcoal (more = slower), and KNO3 (more = faster). You can change many
variables, depending on your tastes. Start with a small batch to verify
your mix is OK. And always write down your formula and note
results!

Pictured is some agricultural grade potassium nitrate -
unmilled on the left, milled on the right. Note how the nitrate
looks like salt on the left, and fine sugar on the right. (Click
picture for larger view.)

The burn rate of the powder can be changed by altering the
particle size. Ball milling the potassium nitrate helps to speed
up the burn rate. Ball milling the sulfur is also a good idea.
(Remember to thoroughly clean out your ball mill after using it.)
Potassium nitrate comes under many different brand names. K-Power
fertilizer i s one such name. It is agricultural grade
KNO3 and is adequate for use in rocketry. However, the
particle size is on the order of salt crystals, and must be ball
milled before using. If you do not want to do this extra step (or
do not *yet* have a ball mill), contact our friends at Skylighter.
They stock both milled and unmilled potassium nitrate. (And a
plethora of other chemicals as well.)

(Freebie tip: Ball mill the air float charcoal and sulfur together
in a 1:1 ration. They are both fuels and safe mixed. The air float will
keep the sulfur from clumping, and it is easier to measure out!)

Screen the sulfur and air float charcoal together (assuming you have
not already ball-milled them together) three times. Add in the potassium
nitrate and screen 3 more times. Add in the course charcoal, and screen
(using a very course mesh screen) three more times. This mix is called
"green mix" and is not true black powder. However, it is more than
adequate for a black powder rocket. Remember to clean your screens after
each use.

(When screening, if you have properly ball-milled your chemicals, it
is recommended to start with a 20 then 40 then 60 mesh screen. By this
time, you have achieved a decent mixing.)

If you add 4 to 5% petroleum jelly to the mix, it will reduce the
dust problem significantly. However, we have observed that this
significantly slows down the burn rate (of green mix). (Comparison burn
rate - a line of untreated green mix took 8 seconds to burn off. Treated
with petroleum jelly - 20 seconds.)

Variations

Meal Powder Plus (in %)

Brown (1878)

Faber (1919)

AFN (1983)

Steyding (1991)

Meal Powder

13

15

80

70

KNO3

52

62

--

--

Charcoal

25

12.5

20

30

Sulfur

10

12.5

--

--

You could also add in 3-5% Titanium for a white spark tail. (NOTE:
Any time you add metal to your comp you MUST press the rocket. DO NOT
use a hammer.)

CONSTRUCTION

You will need your tool set, a scoop, tubes, nozzle material,
hammer or press, and enough comp on hand for one rocket. (It's a
good safety precaution to have enough comp on hand for one rocket,
and leave the rest of the comp covered, away from your work
area.)

Put a tube over the spindle and seat it at the base.
Add one full scoop of nozzle mix. Using the longest drift,
compress it with either ramming or
pressing.

The longest drift has a beveled end, so that the gasses exit
the rocket by being funneled into the nozzle. (The other drifts
are squared on the ends.)

The drifts also have successively smaller holes to accommodate
the spindle's taper.

Extract the drift, add one scoop of comp, and
repeat. Change out the drifts when the next drift has sufficient
clearance of the spindle.

It's usually a good idea to mark your drifts so that it won't
'bottom out' on the spindle, and when to change to the next size.
(I mark the danger spot with red and the change out spot with
black.) Usually you count your scopes - the number depends on the
size of the scope.

It's also a good idea NOT to change out the drifts too
quickly. If the drift gets close to bottoming out, you could be
creating a friction point. Change out the drifts after it is well
clear of the mark.

Make sure the solid drift will NOT come in contact with the
spindle. The compression of the solid drift on the end of the
spindle has been well documented as a cause of
accidents.

When you have reached the top of the spindle, add
one full scoop of comp and use the solid drift. Now add one half
scoop of nozzle mix and compress.

Remove the rocket motor from the spindle. (This is
where you may need to use the strap wrench. I find that I put the
strap around the base, hold the wrench against my leg and use both
hands to loosen the engine.)

At this point, you can do a little test. Tap the
nozzle end of the rocket against your table or ramming station by
dropping it about an inch or so 3 or 4 times. You may see some
dust come out on the first or second tap, but by the fourth one it
should be clean. If comp continues to fall out (in small bits or
dust), you may have a crack. Use this one with caution.

Take a small drill bit (3/16" or 1/4") and slowly
hand drill out a hole at the top of the clay cap to pass fire
to your payload. (NOTE - If you have any added metal to your BP,
this must be done with great caution. Take it s-l-o-w.)

It is usually advised to add your payload before you add the
stick your rocket. This will help you pick a proper weight stick.
Add in a teaspoon of meal BP to the void at the top of the rocket
to help pass fire and add your payload.

Using strapping tape, attach it to the top of the rocket.
(There are many methods for this - usually a strip around the
joint to help hold in the loose BP, and strips across the top of
the heading down to the body of the
rocket.)

STICKING AND FUSING
THE ROCKET

Sticking the rocket

This is a "batch-o-rockets" I did at the 2000 WWB. There
are 4 1lb rockets on the left, 6 3lb rockets on the right.
Payloads are attached, sticked and fused. The one on the far left
has been trimmed for balance, the rest have yet to be
balanced.

Put the stick about 1/2 to 3/4 up the side of the rocket, and
secure using (minimum of) two strips of strapping tape.

AFTER you have applied the payload, trim the stick until it
balances on your finger just below the nozzle. If the stick is
longer, it will be more stable but be heavier. Shorter, and it
will be lighter (faster/higher), but may be unpredictable. Use
strapping tape to adhere the stick to the rocket in two
places.

This is a generally accepted rule, and works very well. You may
hear terms like 'center of pressure' or 'center of thrust', but
that is not covered here. Just know that if you balance your
rocket as described above, it has an excellent chance of flying in
a general upward direction.

Fusing

Two methods of fusing. If you fuse from the nozzle end, the rocket
will take more time to build up enough pressure for lift, but will also
create a larger cloud of sparks and will have a gentle lift-off. (The
rocket video at the top of the page was fused in this manner.) If you
fuse from the deep inside of the cavity, it will light and lift quicker.
Make sure the Visco has a sufficient side-spit to light the composition.

Method 1:
Add a length of Visco
up into the ?business? end of the rocket about 2 inches up. (It
must come in contact with the BP.)

Apply a strip of masking tape across the
bottom to secure the fuse. Keep enough Visco exposed to allow a
sufficient time to retreat to a safe distance.

Method 2:
Put the business end up.
(Optionally add in a bit of meal or loose BP. You may try and add
some NC lacquer to hold the loose BP inside of the rocket.)

Add in a length of quickmatch
with approx. 1? exposed.

Stuff with tissue paper to hold in loose
BP and match.

Tape/secure the nozzle and quickmatch
with some masking tape. Add a couple of inches of Visco to the
other end of the quick match, secure with masking tape.

These rockets are fun and relatively easy to build. They are great for
the beginner manufacturer. And remember:

There are local, state, and federal laws that restrict or prohibit the
use and/or manufacture of pyrotechnic devices. The tools sold in this web
site are strictly for the use and manufacture of devices made within legal
guidelines. We do not encourage, nor are we responsible for individuals
who knowingly or ignorantly violate the law.