# Experimental Estimation of Kinematic Viscosity of Low-Density Air Using Optically Derived Macroscopic Transient Flow Parameters

## TL;DR

This paper introduces a new method to estimate air viscosity in the stratosphere by analyzing parachute oscillations captured with optical devices.

## Contribution

A novel experimental method for calculating kinematic viscosity in rarefied air using parachute canopy oscillation data.

## Key findings

- The calculated kinematic viscosity aligned well with laboratory data.
- Sources of discrepancies in viscosity estimation were identified and discussed.
- The method can aid in analyzing atmospheric flows and parachute design.

## Abstract

This article presents a novel experimental method of calculation of kinematic viscosity parameter for rarefied/low-density air using the analysis of optically recorded oscillations of the stratospheric balloon mission parachute’s canopy. The parachute behavior was captured by a high-definition optical device in the stratosphere during the re-entry phase, giving the input data for the Roshko and Reynolds numbers, which were used in an adapted formula to determine the kinematic viscosity. The calculated parameter was compared with laboratory literature data, showing good alignment, with any sources of discrepancies indicated and discussed. The canopy-breathing method of determination of kinematic viscosity in rarefied air can be employed for the easy investigation of real atmospheric parameters, helpful in the analysis of atmospheric and ionospheric mass flows and the design and performance verification of various novel types of parachutes and re-entry devices.