Mems Wireless Sensor Networks for Spacecraft and Vacuum Technology
Abstract
Wireless sensor networks are highly integrated across numerous industries from industrial manufacturing to personal health monitoring. They provide several key benefits over traditional wired systems including positioning flexibility, modularity, interconnectivity, and robust data routing schemes. However, their adoption into certain sectors such as vacuum and aerospace has been slow due to tight regulation, data security concerns, and device reliability. Lyophilization is a desiccation technique used to stabilize sensitive food and drug products using vacuum sublimation. A series of wireless devices based on the Pirani architecture are developed to quantify the spatial variations in pressure and temperature throughout this process. The data is coupled to computational fluid dynamics simulations to estimate the sublimation rate over time. This information is then used to quantify the heat and mass transfer characteristics of the product, allowing estimates of product temperature and mass flux to be obtained for an arbitrary cycle. This capability is significant, having the ability to accelerate process development and reduce manufacturing time. Drying performance during lyophilization is highly sensitive to the dynamics of the freezing process. This work therefore also develops a wireless network to monitor both gas pressure and temperature throughout the controlled ice nucleation process, a technique used to improve batch uniformity by inducing simultaneous and widespread ice nucleation via adiabatic decompression. The effects of initial charge pressure, ballast composition, and vial size are investigated. Experimental data is supported by numerical modeling to describe the evolution of the true gas temperature during the discharge event. Finally, The mechanisms governing the lyophilization process are directly applied to the aerospace industry in the form of a novel milliNewton-class evaporation-based thruster concept. The device was tested under vacuum using a torsional balance and demonstrated peak thrust magnitudes on the order of 0.5 mN. A state observer model was then implemented to decouple the dynamics of the balance with the time-dependent thrust input. With this model the true time-dependent thrust output and corresponding thruster performance are analyzed.
Degree
Ph.D.
Advisors
Alexeenko, Purdue University.
Subject Area
Electrical engineering|Fluid mechanics|Mechanics
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