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A test was conducted in a supersonic wind tunnel, to determine deployment characteristics and aerodynamic performance of disk-gap-band parachutes of various geometric porosities and ballutes with various ram-air inlet configurations. Deployments were made from a reentry-type model at nominal free-stream Mach numbers from 2.0 to 3.7 at a nominal free-stream dynamic pressure of 70 psf.
Tests were conducted in wind tunnels to determine the drag and performance characteristics of various disk-gap-band parachute configurations in the wake of a 0.10-scale Viking entry vehicle. The parachutes were also tested behind a small faired body to obtain minimum interference parachute performance characteristics. Increasing the parachute trailing distance and suspension line length increased the parachute drag coefficient at each Mach number.
Supersonic wind-tunnel tests were conducted with disk-gap-band parachute models having a nominal diameter of 1.65 meters and geometric porosities of 10.0, 12.5, and 15.0 percent. Canopy inflation characteristics, angles of attack, and drag performance are presented for deployment behind forebody base extensions which were free to oscillate in pitch and yaw. The effect of increasing suspension-line length on canopy motions and drag performance is included, and the drag performance of a model with 12.5 percent geometric porosity is compared with results from flight tests of a parachute with a nominal diameter of 12.19 meters.
Ten flight tests of modified-ringsail, disk-gap-band, and cross parachute configurations with deployment at Mach numbers and dynamic pressures corresponding to conditions expected during entry into a Martian atmosphere have been completed. Comparison of flight results indicates that theoretical snatch force values were never exceeded when the deployment techniques of these tests were used. Opening loads showed no definite trend with Mach number. Values for filling times compared favorably with generally accepted empirical curves based on 15-percent geometric porosity. Canopy stability was good when Mach numbers were below 1.4 for the modified-ringsail and disk-gap-band configurations.
A test was conducted in the 16-ft supersonic tunnel to obtain drag, inflation, and stability characteristics of a metal ballute, a cloth ballute, and three hemisflo parachutes (5-, 10-, and 15-percent porosity). The cloth and metal ballutes were investigated at Mach numbers of 2.5 and 2.9, respectively, at a dynamic pressure of 120 psfa. The hemisflo parachutes were investigated at a Mach number of 2.6 at a dynamic pressure of 120 psfa. The drag coefficient of the hemisflo parachutes decreased as canopy porosity increased. There was no discernible effect of canopy porosity on stability of the parachutes.
An investigation was conducted at Mach 1.80 in the Langley 4-foot supersonic pressure tunnel to determine the effects of variation in reefing ratio and geometric porosity on the drag and stability characteristics of four basic canopy types deployed in the wake of a cone-cylinder forebody. The basic designs included cross, hemisflo, disk-gap-band, and extended-skirt canopies; however, modular cross and standard flat canopies and a ballute were also investigated. An empirical correlation was determined which provides a fair estimation of the drag coefficients in transonic and supersonic flow for parachutes of specific geometric porosity and reefing ratio.
This report documents wind tunnel tests of a series of 20 gore Disk-Gap-Band parachutes to determine the effects off [sic] gap length, band length, band billow, and cloth air permeability on the parachute aerodynamic characteristics. Measurements for the steady-state drag-force, opening shock force, oscillation stability, and inflation stability were made of the various configurations and are presented in tabular and graphical format.