Test Vehicle Forebody Wake Effects on CPAS Parachutes

Abstract

Parachute drag performance has been reconstructed for a large number of Capsule Parachute Assembly System (CPAS) flight tests. This allows for determining forebody wake effects indirectly through statistical means. When data are available in a "clean" wake, such as behind a slender test vehicle, the relative degradation in performance for other test vehicles can be computed as a Pressure Recovery Fraction (PRF). All four CPAS parachute types were evaluated: Forward Bay Cover Parachutes (FBCPs), Drogues, Pilots, and Mains. Many tests used the missile-shaped Parachute Compartment Drop Test Vehicle (PCDTV) to obtain data at high airspeeds. Other tests used the Orion "boilerplate" Parachute Test Vehicle (PTV) to evaluate parachute performance in a representative heatshield wake. Drag data from both vehicles are normalized to a "capsule" forebody equivalent for Orion simulations. A separate database of PCDTV-specific performance is maintained to accurately predict flight tests. Data are shared among analogous parachutes whenever possible to maximize statistical significance.