Thermal management plays a key role in any successful spacecraft mission. Although space would seem to provide the ultimately cold sink, the net heat rejection capability of any spacecraft is limited by its overall surface area, its allowable maximum operating temperature for long spacecraft life, and the Stefan-Boltzmann equation, to first order. Historically, spacecraft have increased in power and complexity bringing many new challenges. This presentation focuses on trends in geosynchronous communications satellites and the advances made in their passive thermal management architectures and hardware. The driving trends include increases in size, lifetime, power, onboard-processing, and heat flux. The focus of the presentation will be on interesting problems associated with use of constant conductance heat pipes (CCHP), loop heat pipes (LHP), and the relatively new oscillating heat pipes (OHP) in real-world systems. These include reflux operation of CCHPs during spacecraft ground test. Satellite systems must be designed not only for operation in space, but they must also allow spacecraft system validation during thermal vacuum testing on the ground. Unique oscillatory thermal performance is presented for a CCHP in reflux along with a method to control and diminish this interesting but unwanted behavior. LHPs provide the necessary heat transport path from the body of the spacecraft to substantial deployable surface area required for high heat rejection. The fundamentals of LHP operation will be discussed along with measurements and modeling of their sintered wick’s thermal conductivity, the relative effects of secondary heat addition (parasitic or controlled), and some interesting zero-g LHP start-up data from STS-87. Oscillating Heat Pipes are finding useful application in addressing many thermal needs that are not addressed by CCHPs and LHPs, such as providing cooling for high heat flux electrical components in tight geometries and integrating two-phase thermal management directly into 3D spacecraft structures. OHP performance limits will be discussed along with 1-g and zero-g validation of these limits on the ASETS-II flight experiment aboard the X-37B. Finally, there will be some discussion of thoughts and lessons learned on technology development and the path to successful insertion of technologies into operational flight systems.
About the Speaker
Dr. Bruce Drolen is a retired Boeing Senior Technical Fellow (STF) having worked at their satellite design facility in El Segundo, CA as well as supporting a wide variety of high-profile efforts across the Boeing enterprise. In his 44 years of thermal management experience, he has developed and modeled the radiative and thermophysical properties of real engineering materials, heat pipes, loop heat pipes, oscillating heat pipes (OHPs), pumped fluid loops, and other heat transport devices under both typical and non-ideal operating conditions. A significant professional accomplishment has been the application of loop heat pipes (LHPs) to high power spacecraft to allow their heat rejection capability to increase 3-fold using LHP-fed deployable radiators. Since 2017, Dr. Drolen has consulted with ThermAvant, leading the development of OHPs, specifically focusing on establishing a thermal and performance modeling capability for OHPs. Dr. Drolen has more than seventy technical journal and conference papers, fourteen patents and several more patent applications in review. He has served as an Associate Editor of the ASME Journal of Heat Transfer and is continues to serve as Associate Editor of the AIAA Journal of Thermophysics and Heat Transfer. In 2017, he received the prestigious AIAA Thermophysics Award. He is a University of Illinois alumnus, BSME-77, MSME-79, with a Ph.D. from U.C. Berkeley in 1986.
Host: Professor Tony Jacobi