Design and development of a gas controlled heat pipe radiator for communication spacecraft application. Life test report

Two heat pipes P1 and P2 were life tested over a period of about three years: P1 (axial grooved ammonia heat pipe; profile type DS-WR4); P2 (same type heat pipe with a coupled gas reservoir; N2 as the inert gas). The life test conditions did not change during the test period of the 3 years. Each 6 months the life test was stopped for a periodical performance test. The latest performance tests were carried out after a test period of 36 months. During life test, each heat pipe was loaded with about 25 Watt heat input and was cooled by radiation and convection to the surrounding atmosphere. Both pipes were arranged in a horizontal position, the operation temperature was around 50 C. No gas generation or performance degradation was noticed in the test period.