FFFFg Black Powder Calculator

Warning: Use of black powder is dangerous and its purchase is prohibited under the age of 21. Check with your local and state laws before use. Consult a mentor prior to first use. Always test black powder charges at a safe distance away, never touching the rocket!

This is designed to give you an approximation as to how much black powder to use. For Standard high powered rockets around 3-4 inches in diameter, 10 to 15 PSI is typical. Piston ejection systems require less. Tight fitting parachutes require more PSI.

Always ground test to insure proper deployment of parachute laundry prior to first launch. Keep clear and a safe distance from the Rocket and deployment during test.

Pounds per square inch (PSI)

Diameter of parachute section body tube:
Inches

Length of parachute section body tube, do not include length of amount that bay slides in or nose cone slides in!
Inches

Grams of FFFFg Black Powder
Grams

Formulas Used:

^2=Squared
A=Area
D=Diameter of cylinder
L=Length of cylinder
F=Force
P=Pressure
N=Size of charge in Grams
V=Volume of cylinder=π((D/2)^2)L
c=Conversion of Grams to Pounds=1/(453.593 gm/lbs)
B=(22.16*12(inches))=265.92 in-lbf/lbm
T=Combustion temperature of FFFFg, 3307 degrees R
F=PA, PV = cBT
z=1/cBT
Final Charge in Grams=PVz
P=Final Charge in grams/(Vz)
Area of Bulkhead=π((D/2)^2)
Calculation of force on Bulkhead: F=Pπ((D/2)^2)

Random:

Take off speed: "Minimum Speed for Stable Flight 44 FPS (30 MPH) is generally accepted as a minimum safe speed for stable flight and is good for winds up to 5 mph. Faster speeds are necessary to achieve stability in windy conditions so add 9 FPS (6 MPH) for each additional 1 MPH of wind speed."

Drogue Descent Rate: Usually around 60-70 FPS (40-50 MPH)

Main Descent Rate: Usually around 20 FPS (13 MPH)