Orbiting Astronomical Observatory heat pipe flight performance data.

The paper describes preflight and inflight performance checkout of the three isothermalizer heat pipes onboard the OAO-C spacecraft. The three pipes are: an axially grooved pipe, a pedestal artery pipe, and a self-priming spiral artery pipe. All pipes are 1/2-inch diameter tube rolled into a 48-inch diameter hoop. They are constructed of aluminum and use ammonia as working fluid. Periodic inflight performance checks have been made since launch in August 1972. No degradation in performance of any of the pipes has been detected. The flight data are in excellent agreement with ground test data.