Cold Weather Testing
The following is a summary of the analysis and results obtained through a cold weather testing experiment performed on the envelope of a non-rigid airship. This experiment is an attempt to comprehend the correlation between the deformation behaviour of a helium filled envelope's shape with respect to changing atmospheric humidity and temperature. In order to collect data on deformation of the envelope shape, local atmospheric humidity and temperature, high resolution cameras are installed strategically at locations inside the cockpit and outside of the envelope. The gas was held at atmospheric pressure in the envelope to isolate the impact of temperature and humidity change. The following figure shows a screenshot of the pictures obtained through these cameras.
Dr.Barry Prentice conducting cold weather testing.
High sensitivity temperature and humidity gauges are used to monitor and collect extensive data at constant intervals of time (i.e. each set of data was obtained at the same time every day). The deformation of the envelope shape is determined using the pictures captured through the cameras and employing digital image correlation. The data collection spanned a duration of roughly three months to ensure high confidence and low error in measurements. After an appropriate amount of data is collected, a regression analysis is performed to evaluate the correlation between this data. The following graph demonstrates the relationship among the envelope shape deformation, local atmospheric temperature and humidity.
Figure 1: A screenshot of multiple cameras focused on different parts of the Airship.
From this graph, it can be seen that at low temperatures and humidity higher levels of deformations are experienced over an 81 day period. During this period, temperatures fluctuated between +8°C and -23°C. A regression analysis was undertaken to better understand the relationship among these parameters. The results from this analysis are shown below.
Figure 2: A graphical representation of the changes in temperature and humidity versus deformation.
From the equation evaluated using the regression analysis, it can be seen that a positive relationship exists between the deformation of the envelope shape and the temperature and humidity of atmospheric air around the envelope. The t-statistics and Multiple R value indicate that the coefficients are within the 95% confidence interval and capture most of the impact.
Figure 3: Regression analysis results obtained through collected data.
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