black powder rockets 1 / 12 - quality pyrotechnic · 13% meal powder 52% potassium ... visco...

Black Powder Rockets 1 / 12

Produced by Granite Falls Arts Inc. Revised 14 November 2016 All Rights Reserved. 202

Table 1: Black Powder Skyrocket Specifications Summary

Rocket Size

Designation

Engine Casing Dimensions (inches) Minimum Stick

Length

Upper Payload

Weight (grams) I.D. O.D. Length

2-Ounce ⅜ ½ 3½ 18 30

4-Ounce ½ ¾ 5 24 60

8-Ounce ⅝ 15

/16 6¼ 30 120

1-Pound ¾ 1¼ 7½ 36 180

2-Pound ⅞ 1⅜ 8¾1 42 300

3-Pound 1 1½ 10 48 500

4-Pound 1¼ 1¾ 12 54 850

6-Pound2 1½ 2¼ 15 72 2000

1 A 10" long tube of this I.D. seems to be more commonly available and can be used assuming

the drifts are long enough to accommodate the extra tube length. 2 The dimensions for the so-called 6-Pound size is starting to become more “standardized” as the

tools and tubes are starting to be carried as standard items by dealers in pyro supplies, but it still

may be too soon to say the dimensions listed here are a “standard.” Black powder rockets using a

tube I.D. of greater than ½" are rare and involve custom tooling and tubes; therefore, a standard

naming convention has not yet emerged.

Black Powder Skyrocket Formulae

2 oz.

60% Potassium Nitrate (120-mesh)

20% Charcoal (air float)

10% Charcoal (80-mesh)

10% Sulfur (100-mesh)

4 oz.







8 oz.





1–2 lb.






3–4 lb.






Note: The strength of any formula can be adjusted by changing the ratio of air float charcoal in

relation to the coarser charcoals. Increasing the air float in the ratio will increase the burn rate

(the power and speed of the rocket); increasing the coarser charcoals in the ratio will decrease the

bum rate.

Mixing Notes

1. First sieve sulfur and then potassium nitrate through a 40-mesh screen.

2. Add air float and 80-mesh charcoals and pass 4–5 times through 40-mesh sieve.

3. Add 36-mesh charcoal and sieve 3 times through a 20-mesh screen.

4. Optional: Mix 4–8% water and/or alcohol and granulate through 20-mesh. Thoroughly

dry before using.



Approaches to BP Rocket Compositions

Meal Powder plus Charcoal/Potassium Nitrate/Sulfur

Browne (1818)

13% Meal Powder

52% Potassium Nitrate

25% Charcoal

10% Sulfur

Faber (1919)

15% Meal Powder


12.5% Charcoal

12.5% Sulfur

AFN (1983)

80% Meal Powder

20% Charcoal

Bush/Hardt (2001)

5% Meal Powder


25% Charcoal

12% Sulfur

Separate Black Powder Ingredients

Range (%) Average (%)

Potassium Nitrate 55–65 60

Charcoal 25–35 30

Sulfur 5–15 10

Factors in Adjusting BP Rocket Compositions

Ratio of ingredients

Particle size of ingredients

Intimacy of mixing

o Sieving Ball Milling

o Wet mix/Granulation



Nature and origins of the charcoal

Loading density

Sample 1 lb. Mix

60% Potassium Nitrate (100 mesh)


18% Charcoal (80 mesh)

2% Charcoal (36 mesh)

10% Sulfur (120 mesh)

Loading Black Powder Rockets

Loading Increment Size Rule

Load no more than one I.D. of comp per increment

The cumulative effect of loading too large an increment is multiple areas of uneven

burning leading to overpressure

Loading Pressures

In general load with as much pressure as possible:

Un-sleeved casings—As much pressure as the case can withstand without bursting

Sleeved casings—More than that!

“Rockets can scarcely be rammed too hard”

A recommended loading pressure is 6,500 lbs/in²

Hand Ramming vs. Pressing

Hand ramming is effective but becomes difficult and impractical in sizes above 3 lb.

Pressing (arbor, pneumatic, hydraulic) allows for greater pressure and control /

measurement of pressure used per increment

Using Sleeves

Not necessary to get good performance from a black powder rocket but it does allow the

use of greater pressure

Ignition Hazards When Ramming Rockets

It is possible to cause an ignition when ramming a black powder rocket

Ignitions are rare and usually associated with hand ramming as opposed to pressing



Importance of Marking Rammers

It is rare but possible to get an ignition ramming a black powder rocket

Usually caused by switching rammers too soon

Mark “No-Pass” lines on all rammers to avoid damaging the tools or causing an ignition!

Rocket Stick Stability

Rule of Thumb

Balance just below nozzle end of motor

Scientific

Center of Gravity must be located a minimum of 1½ engine calibers (O.D.'s) in front of

the Center of Pressure

Further Reading

“Stick Stabilization of Rockets” by Jennings-White & Sommers, PGI Bulletin #105 (July 1997)

“Rocket Stability” by Fred Lienhard, Pyrotechnica X (August 1985)

Ignition

The faster and higher up the central cavity you light the rocket, the faster the rocket will

take off

Visco halfway up the core makes for a slower take of then black match all the way up the

core



Figure 1: Cross section of a core burning black powder rocket motor

Current American Standard Black Powder Rocket Tube Sizing Ratio

Tube I.D. = 1

Tube O.D. = 1¼–1½ I.D.

Tube Length = 10 I.D.

Figure 2: Rocket tube ratios



Table 2: Typical Rocket Tube Ratios

Rocket Size I.D. (inches) O.D. (inches) Length (inches)

2-Ounce ⅜ ½ 3½

4-Ounce ½ ¾ 5

8-Ounce ⅝ 15/16 6¼

1-Pound ¾ 1¼ 7½

2-Pound ⅞ 1⅜ 8¾1

3-Pound 1 1½ 10

4-Pound 1¼ 1¾ 12

6-Pound(2)2 1½ 2¼ 15

1 A 10" long tube of this I.D. seems to be more commonly available and can be used assuming

the drifts are long enough to accommodate the extra tube length. 2 The dimensions for the so-called 6-Pound size are starting to become more “standardized” as

the tools and tubes are starting to be carried as standard items by dealers in pyro supplies, but it

still may be too soon to say the dimensions listed here are standard. Black powder rockets using

a tube I.D. of greater than ½" are rare and involve custom tooling and tubes, therefore a standard

naming convention has not yet emerged.

Nozzle Materials And Preparation

In the past, the nozzle was formed by “choking” the tube near one end, but this practice is

virtually non-existent in the US

Current practice is to use some form of powdered clay or a water activated plaster or

cement type of material

Additives are sometimes mixed the clay to give it certain handling and performance

properties



Table 3: Common Black Powder Nozzle Materials

Material Pros Cons

Bentonite Clay Cheap and easy to obtain

Effective

Easy on tooling

Nozzles subject to a certain

amount of erosion,

especially in larger rockets

Mixtures of bentonite

clay and grog or

Kyanite

Provides better erosion resistance

than bentonite alone

Gives clay more “tooth”-to adhere

to the casing

Requires minimal

preparation

Somewhat harder on

aluminum spindles

Graphite added to

mixtures of bentonite

clay/grog or Kyanite

Graphite adds to the heat resistance

Provides lubrication making it

easier to remove rocket from

spindle

Requires minimal

preparation

Wax/oils added to

clay or

clay/grog/graphite

mixtures

Makes clay “stickier” and provides

better erosion and moisture

resistance than dry clays

Requires more elaborate

preparation and drying time

Kitty litter Cheap and easy to obtain

Effective Easy on tooling

Requires preparation for

best results

Tile grout

Durham’s Rock Hard

Various

plaster/cement

products

Excellent erosion resistance to BP

comps

Requires preparation

before use

Limited working time once

prepared

Requires drying time

before firing rocket



IGNITION HAZARDS WHEN RAMMING ROCKETS

These hazards are caused by changing rammers too soon:

Best Case:

Rammer is stuck on spindle and/or spindle is bent (usually rendering it unusable)

Worst Case:

An Ignition!



“DO NOT PASS” LINES

“Do not pass” lines indicate the point beyond which the rammer will strike the spindle

If you cannot see this line on a rammer —Don’t ram or press on it!

black powder rockets 1 / 12 - quality pyrotechnic · 13% meal powder 52% potassium ... visco...

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