High-Power Rocketry
Black Powder Calculator
Estimates BP charge for cylindrical body tubes with shear pins loaded in shear only.
Always ground-test and follow your rocketry safety code.
Imperial (in, psi, lbf)
Metric (mm, MPa, N)
Shear Pins
Number of pins
Pin diameter
in
Effective pin diameter.
Material (approx. tensile yield)
Nylon 6/6 (~11 ksi / 76 MPa)
Polycarbonate (~9 ksi / 62 MPa)
Acetal / Delrin (~10 ksi / 69 MPa)
ABS (~6 ksi / 41 MPa)
PLA (~9 ksi / 62 MPa)
Custom value…
Tensile yield strength
psi
Double shear (pin loaded in two planes)
Enclosed Gas Volume
Enclosed space diameter
in
Inner diameter of cylindrical body tube.
Enclosed space length
in
Distance from bulkhead to bulkhead.
Force factor of safety
×
1.0 = just enough force to reach shear yield. 2.0 ≈ 2× the shear yield force (more aggressive charge).
⚡
Calculate Charge
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Estimated Charge
0.00 g
≈ 0.0 grains black powder
Start below this value and ground-test in small steps until the separation is reliable without over-pressurizing the airframe.