A method for predicting deployment and inflation of reefed ribbon parachutes is presented. The method is based on integration of axial and radial momentum equations developed in the paper. Axial and radial forces are assumed to be describable by drag and radial force coefficients. Computer solutions of the equations are compared to measured parachute loads and to parachute mouth and maximum diameters from tests of 23and 76-ft-diam conical ribbon parachutes. Comparison of load histories indicates that snatch loads depend to a large extent on deployment bag design and packing influences. Computed loads and parachute size histories for the inflation process compared favorably with flight data. The concept of a radial force coefficient appears to have considerable merit as a means of computing inflation for most types of parachutes.

Analysis of Deployment and Inflation of Large Ribbon Parachutes

Nomenclature CD = drag coefficient based on S CDS — drag area of fully inflated parachute, ft2 (CiwS)r == drag area of reefed parachute, ft2 d = constructed parachute diameter across base of conical parachute, ft Di = inflated diameter, f d, ft hr — release altitude, msl, ft j£t = outflow coefficient (approximately 0.6) Ki = inflow coefficient (a value o^f 0.7 is used for a first approximation, and adjusted as determined by experimental data) Lr = circumferential length of reefing line, ft AP = pressure across canopy, lb/ft2 q = dynamic pressure JpF2, lb/ft2 R = radius of canopy during inflation normal to mean local canopy contour, ft Rm = maximum inflated radius of canopy, ft (approximately | of constructed radius) RQ = initial radius of canopy at start of inflation, ft (radius of suspension lugs or pack radius) s = tensile stress, lb/ft2 S = area of base of conical chute, 7rd2/4, ft2 t = thickness of ribbon, ft if = filling time, sec T — ribbon tensile load, Ib V = vehicle velocity, fps Fo = vehicle velocity at start of parachute filling, fps w = ribbon width, ft W = vehicle weight, Ib XG = geometric porosity of canopy p = air density, slugs/ft3

Aerodynamic decelerators - An engineering review

.............................................................................................................................. ii Acknowledgements............................................................................................................. ii Table of

Velocity Field Measurements in the Near Wake of a Parachute Canopy

Webbings are used in parachute assemblies as reinforcing units for the strength they provide. The strength of these seams is an important characteristic which has a substantial influence on the mechanical property of the parachute assemblies. It is well established that factors such as fabric width, folding length of joint, seam design and seam type will all have an impact on seam strength. In this work, the effect of these factors on seam strength was studied using both Taguchi's design of experiment (TDOE) as well as an artificial neural network (ANN). In TDOE, two levels were chosen for the factors mentioned above. An L8 design was adopted and an orthogonal array was generated. The contribution of each factor to seam strength was analyzed using analysis of variance (ANOVA) and signal to noise ratio methods. From the analysis it was found that the fabric width, folding length of joint and interaction between the folding length of joint and the seam design affected seam strength significantly. Further, u...

Predicting the Seam Strength of Notched Webbings for Parachute Assemblies Using the Taguchi's Design of Experiment and Artificial Neural Networks

N a tethered wind energy conversion system, usually the tether is designed with the assumption that the tether static profile is a catenary.1"4 The catenary behavior is assumed because the equations of a catenary are well known and can be obtained analytically without much difficulty. However, a catenary cannot accurately represent the tether profile in situations where the wind drag is of the same order of magnitude as the weight of the tether. The tether drag varies as the tether diameter, while the tether weight is proportional to the square of the diameter. Consequently, for smalldiameter tethers or when the tethers are made of materials with high strength-to-weight ratios, the deviation from a catenary behavior may become appreciable. In this study, we have considered the effect of wing drag on the static profile and force transmission efficiency of a tether connected to a kite-like system. Calculations have been made assuming that the velocity and density fields due to the wind do not vary with altitude.

Effect of wind loading on the design of a kite tether

Parametric Study of Parachute Pressure Distribution by Wind Tunnel Testing

Kevlar-29, an aramid fiber manufactured by DuPont, is being used on parachute systems requiring high strength-to-weight ratios or resistance to sustained high temperatures. Tests of parachutes using Kevlar webbing, braided cords, ribbons, and thread have demonstrated that these Kevlar materials can be used successfully in ribbon parachutes with no detrimental effects on performance. A few changes must be made in the design of a ribbon parachute to accommodate Kevlar's high modulus. Examples of parachutes that use Kevlar suspension lines, radials, ribbons, reefing lines, bridles, and skirt bands are presented to show that they are much lighter and more resistant to aerodynamic heating than their all-nylon counterparts.

Application of Kevlar to parachute system design

A total of 70 tests, including static tests, rocket sled launchings, and rocket-boosted and aircraft drops, have been used to develop the 24-ft diam. hybrid Kevlar-29/nylon ribbon parachute for recovery of the 760-Ib store. The parachute has been deployed successfully over an environmental temperature range of -65° to 160°F and has operated successfully over the design range of deployment speeds from 330 KCAS to Mach 1.2 at sea level.

Design and Development of the 24-Ft Diam Hybrid Mevlar- 29/Nylon Ribbon Parachute

The design and testing of a two-stage parachute system to recover a space telescope weighing up to 2000 pounds is described. The system consists of a 15-ft dia ribbon parachute reefed to 50% for 10 seconds and a 73-ft dia paraform or cross second stage reefed to 10% for 10 seconds. The results of eight drop tests and one operational rocket launched flight and recovery are presented. A successful operational recovery of a 1600-lb NASA space telescope was conducted. The payload was launched by a second stage Minuteman rocket to an altitude of about 300 miles above sea level.

/pdf/development-of-the-aries-parachute-system-35hoog4c8t.pdf

William B. Pepper

Papers

Aerodynamic decelerators - An engineering review

Parametric Study of Parachute Pressure Distribution by Wind Tunnel Testing

Application of Kevlar to parachute system design

Design and Development of the 24-Ft Diam Hybrid Mevlar- 29/Nylon Ribbon Parachute

Development of the Aries parachute system