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Conventionally shaped Ribbon parachutes do not function satisfactorily as aerodynamic decelerators in supersonic flow. Particularly objectionable is their unstable behavior. In order to determine the cause of this structural and dynamic instability, a series of pressure distribution measurements were made on ribbon parachutes at Mach numbers of 0.8, 1.2, 3.0, and 4.5. This report presents the results of measurements and attempts to indicate the effect of suspension lines and forebodies on the pressure distribution of the parachute canopy.
The measured mass flows are analyzed relative to free stream velocity and density ratio. The results are presented as ratios of measured to inviscid flow through the canopy inlet area, thus giving a measure of the canopy's ability to accommodate the air mass entering the parachute mouth. Related to the mass flow studies, was the determination of pressure distributions on the internal and external canopy surfaces. Measurements were made at Mach 0.8, 1.2, and 3.0. In addition, several tests were conducted using an ogive forebody at two upstream locations. The wake of the ogive forebody with respect to pressure is analyzed. (Author).
Results are presented in this report of an experimental study to determine the air flow through several fully open circular flat ribbon canopies of various geometric porosities and a 17% geometric porosity Hemisflo canopy during its inflation. The measured mass flows are correlated with inviscid flow as a measure of the canopy's accommodation of the air mass available at the mouth inlet under specific operation conditions. In conjunction with the actual measurements of mass flow, the pressure distributions on the internal and external canopy surfaces were determined. These measurements were made on models with suspension lines as well as on models without suspension lines so that suitable estimates of suspension line effects could be made. Measurements were made at Mach 0.8, 1.2, and 3.0. In addition, several tests were conducted in the wake of an ogive cylinder located at two upstream positions. (Author).
This report presents the results of an experimental study to qualitatively determine the air flow through a Hemisflo ribbon parachute during the inflation process. These measured mass flows are analyzed relative to free stream velocity and density ratio. The results are presented as ratios of measured to inviscid flow through the canopy inlet area, thus giving a measure of the canopy's ability to accommodate the air mass entering the parachute mouth. Related to the mass flow studies, was the determination of pressure distributions on the internal and external canopy surfaces. Measurements were made at Mach 0.8, 1.2, and 3.0. In addition, several tests were conducted using an ogive forebody at two upstream locations.
This report summarizes measurements of pressure distributions over the canopy of two rigid parachute models. This study was originated under Contract No. AF 33(616)-3755, but was discontinued through an executive order on Sept. 6, 1957. Because of related studies pursued by Sandia Corporation, Albuquerque, New Mexico, the evaluation and analysis of already recorded data was requested and sponsored by Sandia Corporation through a purchase request issued on March 3, 1958. The investigation was conducted on a guide surface and a ribbon parachute model with 20% geometric porosity. Both models had a 2.5 inch maximum projected diameter. The tests were made in a speed range of M[infinity] = 0.6 to 1.2.
The location of shock waves, the pressure distribution and the mass flow, which are significant for the functioning of a parachute in supersonic flow, are discussed and some advantageous conditions are postulated. Wind tunnel studies are described in which the validity of the assumptions has been checked by means of models of a modified guide surface canopy combined with a shock producing cone. A configuration was found according to which 4 inch textile models function satisfactorily up to Mach numbers of 4.5. The results of further supersonic wind tunnel tests are shown in which a 4 ft supersonic guide surface parachute, built in accordance with the established aerodynamic parameters, functioned satisfactorily. This parachute collapsed due to structural weakness at a Mach number of 2.8 after being exposed to supersonic flow for approximately 90 minutes. The concept of the wake producing cone in conjunction with ribbon parachute canopies was also tried, but no satisfactory configuration was found. (Author).