by: Veronica Benitez - Thermal Engineering Intern at Goddard Space Flight Center and MEng Student
This summer I had the opportunity to work at NASA Goddard Space Flight Center. I interned in the Thermal Engineering branch and worked with the thermal team of the Global Precipitation Measurement (GPM) satellite. Working in the Thermal Engineering Branch has been an incredible learning experience. Aside from my primary project, I was able to work on many important tasks that a thermal engineer would complete in a typical work day including both analysis and testing.
On the thermal analysis and modeling side, I gained familiarity with the software used at GSFC mainly Thermal Desktop and SINDA Fluint. I was able to work with Thermal Desktop in tutorials and real thermal problems. I used SINDA Fluint to create the multiple cases of my primary project.
On the integration and testing side, I created multiple Work Order Authorization forms and helped test real flight hardware. I was put in charge of a thermal blanket bakeout for GPM Multilayer Insulation blankets as well as a Chotherm bakeout. I created the Work Order Authorization forms for both, made sure they were approved by the Quality Assurance Engineers as well as the Contamination Engineers. I was able to contribute to the thermal vacuum testing of the solar array drive assembly (SADA) by attending shifts to monitor the temperature of the chamber and the various components of the SADA. I also helped install thermocouples on the avionics module of the GPM satellite and route them to the proper location for connection.
My primary project at GSFC was the statistical analysis of the thermal margins of the GPM spacecraft. The average spacecraft designed at GFSC is proposed to last three to four years; however, the majority of these spacecraft are consistently lasting anywhere from ten to fifteen years. The result of the longer spacecraft life may be due to overdesign by assuming accumulated worst case scenarios. The purpose of my study is to assess the degree of margin and conservatism in the GPM thermal design that may be masked by designing to stacked, worst case conditions. The assessment contains the analysis of how the temperature and heater power of the critical spacecraft components vary over the lifetime of the spacecraft when four different variables are adjusted: power dissipation, optical properties, beta angle, and seasonal flux.
A distribution plot of the temperature ranges was created to analyze what percent of the mission lifetime the spacecraft critical components will spend at various margin ranges from operational. The impact of conservatism on each of the four variables can be studied independently to evaluate how much margin is absorbed or generated by using the extreme variables instead of nominal values. The end result of this study will be a way of quantifying the degree of conservatism in the GPM Observatory thermal design based on the traditional design approach used by the GSFC Thermal Branch.