The Idaho National Engineering Laboratory (INEL) is conducting intensive research in the design and development of a small, excore heat‐pipe‐thermionic space nuclear reactor power system (SEHPTR). Progress in this research effort has identified the need for an in‐space flight demostration of a thermionic heat pipe element. The proposed demonstration will examine the performance of such a device and verify its operation in microgravity. This paper focuses on the design of a microsatellite‐based technology demonstration experiment to measure the effects of microgravity on the performance of an integrated thermionic heat pipe device in low earth orbit. Two scenarios, THERMION‐I and THERMION‐II, emerged from the design process. Selection between the two will depend upon yet undermined experiment lifetime requirements.
THERMION‐I is designed for a long‐lifetime (greater than one year) investigation of the operations of the thermionic heat pipe element in low earth orbit. Heat input to the element is furnished by a large mirror which collects solar energy and focuses it into a cavity containing the heat pipe device. THERMION‐II is a much more simple design which is utilized for short‐term (approximately one day) operation. This experiment remains attached to the Delta II second stage and utilizes energy from 253 kg of alkaline batteries to supply thermal energy to the heat pipe device.
