This paper describes the development and results of numerical models describing parachute inflation behavior. The models were developed using Fluid Structure Interaction (FSI) techniques in the commercially available transient dynamic finite element code LS-DYNA. Prior to 2009, FSI simulation methodologies developed at Airborne Systems had restricted analysis to the steady-descent phase of parachute operations. That is to say the modeling was performed in an infinite mass scenario, where the parachute does not influence the freestream air velocity; such models can be compared to tests conducted in a wind tunnel or during the steady descent phase of operation. Funding provided by NSRDEC in 2009/10 enabled Airborne Systems to develop a simulation methodology that is capable of assessing parachute performance in a finite mass scenario. Such a scenario enables the more complex inflation phase of a parachute to be investigated. In addition, the availability of experimental data, describing parachute inflation, has until recently proved limiting in quantifying the accuracy of simulation techniques. The availability of test data from a series of indoor vertical parachute tests conducted at the Space Power Facility at NASA Glenn Research Center Plum Brook Station provided an excellent means of code result validation. The experimental test setup produced a sufficiently controlled and instrumented environment specifically developed for basic parachute performance data collection. The results of the modeling, discussed herein, compare favorably with the indoor vertical parachute tests, with good prediction of both inflation force and post inflation breathing frequency. The models were developed prior to test data reduction and analysis, and as such acted as a true prediction. Nomenclature Cd = Drag coefficient D 0 = Nominal diameter PIA = Parachute Industries Association
This paper describes the analysis of a ribbon parachute system using existing parachute analysis software and techniques currently available within the parachute industry. A novel combination of an internally developed trajectory and loads analysis code and a commercially available Finite Element Analysis code was used to provide a detailed parachute analysis methodology. System level analysis was performed using an internally developed code DCLDYN (DeCeLerator DYNamics). DCLDYN was used to generate a parachute inflationary model based on existing drop test data. The inflationary model was then used to assess parachute performance parameters at edge-of-the-envelope operational conditions. This phase defined the maximum parachute forces for all nominal parachute performance scenarios. In order that the predictable variability observed in parachute performance was considered, a Monte Carlo stochastic simulation was conducted to provide a probabilistic understanding of the maximum parachute forces. The Monte Carlo simulation utilized the variability of inflationary performance identified in the drop test data as well as parachute knowledge and experience from Airborne Systems. The end result being that the nominal and maximum parachute forces were obtained for each corner of the current operational envelope. The nominal and maximum parachute force conditions for the worst corner of the operational envelope, for each parachute, were then assessed at a more detailed level using the commercially available code LS-DYNA. Utilizing a combination of the two codes enables the user to draw on the benefits of a broad source of experimental data from 90 years of recovery system design at Airborne Systems and at the same time exploit the powerful finite element methods now available from commercial codes. This work identified the design driving operational scenario and will also be used to help guide future test conditions.
A repositioning event is defined as when a payload must change orientation during steadystate parachute descent to prepare for landing or other operation. This paper describes one methodology for the design of a repositioning system along with a generalized case study. A simulation of an unmanned aerial vehicle repositioning is performed to give qualitative data comparisons that would otherwise only be available through flight testing. The repositioning event simulation is used to demonstrate compliance of a three-legged harness system with given repositioning design requirements of the case study. Additional simulations are performed to demonstrate the effects of different stiffness materials as well as use of attenuation to control rotation motion. Nomenclature UAV = unmanned aerial vehicle CG = center of gravity MOI = moment of inertia
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.