Momentum-Impulse Balance and Parachute Inflation: Fixed Point Drops

Abstract

A S documented in [1], the momentum–impulse theorem (or “MI theorem”) is a very useful tool for analyzing parachute inflation, given that the duration of the net drag force generated during the inflation process is a well-documented empirical input. In particular, the MI theorem can be used to extend a well-known technique for estimating the maximum drag Fmax to any type of parachute and reefing designs, and to any type of drop conditions. This Note aims at building on the insight gained in [1], by applying the theorem to drops of hemispherical-type canopies from fixed points rather than from aircraft. Such fixed points would not only include cranes and ceilings, but also (slow-moving) lighter-than-air aircraft and even (slow-moving) personnel parachutes. This analysis shall reveal several inflation facts that were previously unknown to the parachute engineering field. The extended Fmax estimator technique is based on the following formula, which uses the a priori knowledge of the opening-shock factor Ck [1–5]