Design, Qualification and Integration Testing of the High-Temperature Resistance Temperature Device for Stirling Power System

Abstract

The Advanced Stirling Radioisotope Generator (ASRG), developed from 2006 to 2013 under the joint sponsorship of the United States Department of Energy (DOE) and National Aeronautics and Space Administration (NASA) to provide a high-efficiency power system for future deep space missions, employed Sunpower Incorporated's Advanced Stirling Convertors (ASCs) with operating temperature up to 840 °C. High-temperature operation was made possible by advanced heater head materials developed to increase reliability and thermal-to-mechanical conversion efficiency. During a mission, it is desirable to monitor the Stirling hot-end temperature as a measure of convertor health status and assist in making appropriate operating parameter adjustments to maintain the desired hotend temperature as the radioisotope fuel decays. To facilitate these operations, a Resistance Temperature Device (RTD) that is capable of high-temperature, continuous long-life service was designed, developed and qualified for use in the ASRG. A thermal bridge was also implemented to reduce the RTD temperature exposure while still allowing an accurate projection of the ASC hot-end temperature. NASA integrated two flight-design RTDs on the ASCs and assembled into the highfidelity Engineering Unit, the ASRG EU2, at Glenn Research Center (GRC) for extended operation and system characterization. This paper presents the design implementation and qualification of the RTD, and its performance characteristics and calibration in the ASRG EU2 testing.

A Comparative Study about Accuracy Levels of Resistance Temperature Detectors RTDs Composed of Platinum, Copper, and Nickel

“…The acceptance of accuracy is correlated with accuracy level. The RTD correlation can predict the accepted temperature with acceptable accuracy [31]. In many applications, the necessity of accuracy comes with the focus on each of repeatability and stability of the sensor, therefore, the features of stability and repeatability are often confused with the accuracy level, but the important thing is to understand the difference between them in order to choose type of metal to application purpose in designated location.…”

“…The analysis from [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] in above section (5. Methods and materials) will summarized as in table 2.…”

Advanced Stirling Radioisotope Generator EU2 Anomaly Investigation

“…By using the thermal bridge, the RTD is not exposed to the full hot-end temperature, but it is able to project hot-end temperature for monitoring purposes. 5 Convertor dimensional inspection uncovered some small dimensional changes that point to the possibility that the RTD thermal bridge could be influencing heater head geometry. However, a detailed review of the data showed that the dimensional biases towards the RTD thermal bridge seen with ASC-E3 #2 preceded the installation of the RTD thermal bridge, and the changes simply grew over time.…”