formulas provided below will calculate an estimated parachute size that will result in a descent rate of about 15 feet per second. If the landing area is hard, such as packed earth or salt, a slower descent rate may be desired to prevent damage to the rocket.Circular Parachute
size in inches = sqrt( rocket_weight_in_pounds * 0.454 ) * 39.6Example of a 5 pound rocket:
sqrt( 5 * 0.454 ) * 39.6 = 59.7" (60" parachute)X-Form Parachute
size in inches = sqrt( rocket_weight_in_pounds * 0.454 ) * 51.5Example of a 5 pound rocket:
sqrt( 5 * 0.454 ) * 51.5 = 77.6" (78" parachute)A smaller parachute will result in a faster descent. A larger one a slower descent. If the ground is soft, such as grass covered, you may want to use a smaller parachute for a faster descent. A faster descent will result in less drift. If the ground is hard, like frozen earth or salt, you may want a slower descent, and therefore a larger parachute.
Submitted by Dean Roth