[PDF] The Reduction Of Parachute Inflation Time Through Use Of An Internal Canopy As Experienced In Laboratory And Full Size Studies eBook

Author : R. J. Niccum
Publisher :
Page : 20 pages
File Size : 46,26 MB
Release : 1964
Category : Force and energy
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A short opening time and moderate opening force are desirable characteristics of practially all parachute applications. But because of the interdependency between opening time and force, this is one of the most intricate functions in the dynamics of parachute inflation. Particularly, parachutes with rapid inflation usually develop a high opening force. It has been hypothesized that since theoretical and experimental analyses indicate that the maximum force occurs after the canopy has attained one-half or more of its fully inflated size, possibly an acceleration of the initial phase of opening might have the desired effect upon the total inflation.

Author :
Publisher :
Page : 185 pages
File Size : 30,29 MB
Release : 1978
Category :
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The Omega sensor was developed for measuring stress in textile and other flexible materials by the Department of Aerospace Engineering and Mechanics of the University of Minnesota and sponsored by the Air Force Flight Dynamics Laboratory. Two studies were conducted by the University which indicated that the circumferential stresses of inflated parachute canopies indicated by Omega sensors agreed with theoretically predicted stresses and also that the stresses measured by an Omega sensor were not affected by dynamic loading. This particular study deals with an in-house test program, designed to measure the circumferential stresses of a model (five foot nominal diameter) ringslot parachute during inflation and at steady state using modified Omega sensors. Slight modifications to the original Omega sensor had to be made due to complications of the tabs tearing during preliminary testing. Five sensors were attached strategically to the canopy of a ringslot parachute and put through a series of low speed wind tunnel tests. The results are presented in detail and provide for the first time actual measurement of circumferential stresses on the surface of a model ringslot parachute. These results, however, can only present the general trend shown in the parachute's stress distribution and not actual stress values due to the inability to calibrate the sensor while attached to the canopy.

Author : H. D. Melzig
Publisher :
Page : 78 pages
File Size : 50,57 MB
Release : 1966
Category : Parachutes
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An experimental investigation and correlative analysis were conducted to determine the pressure distribution over the surface of parachute canopies during the period of inflation for the infinite mass case and to correlate pressure coefficients with inflating canopy shapes. Parachute canopy models of Circular Flat, 10% Extended Skirt, Ringslot, and Ribbon designs were tested under infinite mass conditions in a 9 x 12 ft low speed wind tunnel. External and internal pressure values were measured at various locations over the surface of the model canopies throughout the period of inflation, and generalized canopy profile shapes were obtined by means of photographic analysis.

Author : H. D. Melzig
Publisher :
Page : 94 pages
File Size : 30,50 MB
Release : 1969
Category : Parachutes
ISBN :

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An experimental investigation was conducted to determine the differential pressure distribution over the surface of parachute canopies during the period of inflation under mass conditions. Full scale parachute canopies of the circular flat, 10% extended skirt, ringslot and ribbon types were utilized during the free-flight test program, and differential pressures on the gore centerline and on the cord line were measured by means of four pressure transducers distributed over the canopy in equal distances from the skirt to the vent. In order to analyze the relationships and dependencies between the pressure distribution, projected canopy area, canopy shape, generated force, and dynamic pressure, graphical displays of these quantities were made as a function of time for each type of parachute canopy. The results of the pressure distribution measurements permit a better understanding of the physical nature of the dynamic process of parachute inflation. The stress distribution in a parachute canopy can be calculated if the corresponding canopy shape is known. For this purpose, the evolvement of the canopy shape with the corresponding time is presented for each of the canopy types. (Author).

Author : Charles H. Whitlock
Publisher :
Page : 30 pages
File Size : 15,92 MB
Release : 1969
Category : Parachutes
ISBN :

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Exploratory wind-tunnel tests of the disk-gap-band and modified ringsail parachute configurations have been conducted at dynamic pressures between 0.24 and 7.07 lb/ft2 (11 and 339 N/m2). Both parachutes exhibited positive inflation characteristics over the range of the tests within technique limitations. The disk-gap-band configuration required less time and distance to inflate than the modified ringsail configuration did.

Author : H. D. Melzig
Publisher :
Page : 137 pages
File Size : 14,63 MB
Release : 1965
Category :
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An experimental investigation and correlative analysis were conducted to determine the pressure distribution over the surface of parachute canopies during the period of inflation for the infinite mass case and to correlate pressure coefficients with inflating canopy shapes. Parachute canopy models of Circular Flat, 10% Extended Skirt, Ringslot, and Ribbon designs were tested under infinite mass conditions in a 9 x 12 ft low speed wind tunnel. External and internal pressure values were measured at various locations over the surface of the model canopies throughout the period of inflation, and generalized canopy profile shapes were obtained by means of photographic analysis. Pressure coefficients derived for the steady state (fully open canopy) are quite comparable to the results of previous measurements. Peak pressure values during the unsteady period of inflation were found to be up to 5 times as great as steady state values. The relationships between the pressure distribution and time for each of the canopy models deployed at free-stream velocities between 70 and 160 ft/sec are presented in detail and correlated with changing canopy shape. A complete shape analysis is made and a mathematical model is proposed. (Author).

Author : Helmut G. Heinrich
Publisher :
Page : 62 pages
File Size : 23,73 MB
Release : 1965
Category : Parachutes
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The stresses occurring in the cloth of an opening parachute and at steady state are calculated. The method is based on assumed instantaneous and steady state shapes and related pressure distributions. It is general and may be applied to any type and size of canopy built out of solid cloth. The presented analysis is limited to canopies constructed of triangular gores, but can be extended to other gore patterns. A numerical calculation is made for the Solid Flat, Circular Parachute during the opening and at steady state.

Author : John W. Watkins
Publisher :
Page : 7 pages
File Size : 23,54 MB
Release : 1995
Category : Parachute troops
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This paper describes the development of a reefing system used to speed up inflation of a round parachute canopy. This reefing system, called Mid-Canopy Reefing (MCR), was developed in response to a need to reduce the minimum jump altitude of a developmental low-altitude troop parachute. This reefing system temporarily reduces the size of the parachute canopy, causing it to inflate more rapidly than the same canopy without reefing. Use of this system made it possible to cut the inflation time of the troop parachute in half, and there was a significant reduction in the minimum jump altitude.