Date of Award


Degree Type



Mechanical Engineering

First Advisor

Ibrahim, Mounir

Subject Headings

Heat flux transducers, Heat -- Transmission, Thin films, Stirling engines, Radioisotopes, Electric power systems, Heat flux, Heat transfer, Thin film thermocouples, Stirling engine, Stirling Radioisotope Power System, Heat addition, Net heat input


Stirling convertors are being operated by NASA Glenn Research Center for many years to demonstrate a Radioisotope Power System (RPS) capable of providing reliable power for potential multi-year space missions. Techniques used to monitor Stirling convertors for change in performance include measurements of temperature, pressure, energy addition, and power output. It is difficult to measure energy addition to Stirling convertors due to the complex geometries of the hot components, temperature limits of sensor materials, and invasive integration of sensors. A thin-film heat flux sensor was used to directly measure heat energy addition to a Stirling convertor. The one micron thick, Gold vs. Platinum thermocouples were designed to make a noninvasive temperature measurement on the surface of an Alumina ceramic disk located between the heat source and Stirling convertor. Fabrication techniques included creation of ceramic substrates, which hold the thermocouples, using the slipcasting technique and creation of the thin metallic film thermocouples using Physical Vapor Deposition (PVD). The effort succeeded in designing and fabricating unique sensors which, for the first time, were integrated into a Stirling convertor ground test and exposed to test temperatures exceeding 700°C in air for 10,000 hours. The heat transfer measurements are discussed. Also, the sensors were examined after being removed when the test was completed