Black Powder Rockets 1 / 12

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1 Black Powder Rockets 1 / 12 Rocket Size Designation Table 1: Black Powder Skyrocket Specifications Summary Engine Casing Dimensions (inches) Minimum Stick Length Upper Payload Weight (grams) I.D. O.D. Length 2-Ounce ⅜ ½ 3½ Ounce ½ ¾ Ounce ⅝ 15 / 16 6¼ Pound ¾ 1¼ 7½ Pound ⅞ 1⅜ 8¾ Pound 1 1½ Pound 1¼ 1¾ Pound 2 1½ 2¼ 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. 60% Potassium Nitrate (120-mesh) 18% Charcoal (air float) 12% Charcoal (80-mesh) 10% Sulfur (100-mesh)

2 Black Powder Rockets 2 / 12 8 oz. 60% Potassium Nitrate (120-mesh) 15% Charcoal (air float) 15% Charcoal (80-mesh) 10% Sulfur (100-mesh) 1 2 lb. 60% Potassium Nitrate (120-mesh) 10% Charcoal (air float) 18% Charcoal (80-mesh) 2% Charcoal (36-mesh) 10% Sulfur (100-mesh) 3 4 lb. 60% Potassium Nitrate (120-mesh) 8% Charcoal (air float) 18% Charcoal (80-mesh) 4% Charcoal (36-mesh) 10% Sulfur (100-mesh) 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.

3 Black Powder Rockets 3 / 12 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 60% Potassium Nitrate 12.5% Charcoal 12.5% Sulfur AFN (1983) 80% Meal Powder 20% Charcoal Bush/Hardt (2001) 5% Meal Powder 58% Potassium Nitrate 25% Charcoal 12% Sulfur Separate Black Powder Ingredients Range (%) Average (%) Potassium Nitrate Charcoal Sulfur Factors in Adjusting BP Rocket Compositions Ratio of ingredients Particle size of ingredients Intimacy of mixing o Sieving Ball Milling o Wet mix/granulation

4 Black Powder Rockets 4 / 12 Nature and origins of the charcoal Loading density Sample 1 lb. Mix 60% Potassium Nitrate (100 mesh) 10% Charcoal (air float) 18% Charcoal (80 mesh) 2% Charcoal (36 mesh) 10% Sulfur (120 mesh) Loading Increment Size Rule Loading Black Powder Rockets 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

5 Black Powder Rockets 5 / 12 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! Rule of Thumb Balance just below nozzle end of motor Scientific Rocket Stick Stability 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

6 Black Powder Rockets 6 / 12 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

7 Black Powder Rockets 7 / 12 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 8¾ 1 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

8 Black Powder Rockets 8 / 12 Table 3: Common Black Powder Nozzle Materials Material Pros Cons Bentonite Clay Cheap and easy to obtain Effective Easy on tooling Mixtures of bentonite clay and grog or Kyanite Graphite added to mixtures of bentonite clay/grog or Kyanite Wax/oils added to clay or clay/grog/graphite mixtures Kitty litter Tile grout Durham s Rock Hard Various plaster/cement products Provides better erosion resistance than bentonite alone Gives clay more tooth -to adhere to the casing Graphite adds to the heat resistance Provides lubrication making it easier to remove rocket from spindle Makes clay stickier and provides better erosion and moisture resistance than dry clays Cheap and easy to obtain Effective Easy on tooling Excellent erosion resistance to BP comps Nozzles subject to a certain amount of erosion, especially in larger rockets Requires minimal preparation Somewhat harder on aluminum spindles Requires minimal preparation Requires more elaborate preparation and drying time Requires preparation for best results Requires preparation before use Limited working time once prepared Requires drying time before firing rocket

9 Black Powder Rockets 9 / 12

10 Black Powder Rockets 10 / 12

11 Black Powder Rockets 11 / 12 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!

12 Black Powder Rockets 12 / 12 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!