Estimates for the Aerodynamic Coefficients of Ringsail and Disk-Gap-Band Parachutes Operating on Mars

Abstract

Models are presented for the aerodynamic coefficients of Supersonic Ringsail and Disk-Gap-Band parachutes as functions of total porosity, λ T , Mach number, M, and total angle of attack, α T (when necessary). The source aerodynamic coefficients data used for creating these models were obtained from a wind tunnel test of subscale parachutes. In this wind tunnel test, subscale parachutes of both parachute types were fabricated from two different fabrics with very different permeabilities. By varying the fabric permeability, while maintaining the parachute geometry constant, it was possible to vary λ T . The fabric permeability test data necessary for the calculation of λ T were obtained from samples of the same fabrics used to fabricate the subscale parachutes. Although the models for the aerodynamic coefficients are simple polynomial functions of λ T and M, they are capable of producing good reproductions of the source data. The (λ T , M) domains over which these models are applicable are clearly defined. The models are applicable to flight operations on Mars.* An expanded version of this paper, including the source data, will be published as a NASA Technical Memorandum.

Similarity criteria for canopy porosity and environmental impact analysis of air permeability

“…Yang [5] used the Ergun formula to describe the dynamic air permeability of the fabric, that is, the air permeability changes with the differential pressure between the canopy. Cruz [6] obtained the air permeability through experiments, which were transformed into an effective permeability for using in calculations related to parachutes, and created models that related the effective permeability to the unit Reynolds through experiments.…”