Here is a simple Excel spreadsheet tool to help calculate the amount of black powder to use for ejection charges. The calculator assumes a parachute protector is being used. It does not currently do the calculation for a piston, which generally takes less black powder than a chute protector. The calculator is also not intended for high altitude flights (~20k and above).
This calculator based on the new model presented in my paper, "Using Black Powder for Parachute Deployment", available on the Papers tab. I developed the new model after having several deployment failures using the amount of black powder recommended by the existing black powder calculators - even after bumping up the recommended quantity. For small to medium sized high power rockets, this new calculator will predict 1-4 times the amount of black powder as the traditional calculators depending upon the parachute configuration. The calculation already includes the safety margin needed for an energetic deployment, so an additional multiplier is not needed. All my flights with recovery blankets have had successful deployments using the quantity recommended by this new calculator.
If you use this calculator, I would appreciate any feedback you have to help me make improvements. Just send a note to tfetter@speedmotionrockets.com.
IMPORTANT! - The Black Powder Calculator result is just a starting recommendation - always ground test with the parachute, recovery blanket, and shock cord in the flight configuration!
