Flight Testing of the Capillary Pumped Loop Flight Experiment

Abstract

The Capillary Pumped Loop Flight Experiment (CAPL) employs a passive two-phase thermal control system that uses the latent heat of vaporization of ammonia to transfer heat over long distances. CAPL was designed as a prototype of the Earth Observing System (EOS) instrument thermal control systems.The purpose of the mission was to provide validation of the system performance in micro-gravity, prior to implementation on EOS. CAPL was flown on STS-60 in February, 1994, with some unexpected results related to gravitational effects on two-phase systems. Flight test results and post flight investigations will be addressed, along with a brief description of the experiment design.

Mathematical model of a loop heat pipe with cylindrical evaporator and integrated reservoir

“…Maidanik [11] reveals the low power limit on start-up and recuperation mode in CPLs. There were several flight missions carrying CPLs as scientific payloads and devoted to investigations of its performance under micro-gravity conditions [12][13][14].…”

Theoretical model for fast bubble growth in small channels with reference to startup of capillary pumped loops used in spacecraft thermal management systems

“…Difficulty with startup has, arguably, been the single greatest factor limiting the wide acceptance of CPLs for thermal management of spacecraft. Startup failures and other system anomalies that can be attributed to incomplete or improper priming have plagued flight experiments [9][10][11][12]. Recently, the CPLbased thermal control system that was designed for the Mars Polar Lander (MPL) of the Mars'98 mission [13] was eliminated from the spacecraft due to the CPL's inability to reliably start during system level testing.…”

Test Results for a High Power Thermal Management System

“…CAPL-1 (Butler, Ottenstein, and Ku, 1995) flew in 1994 (STS-60) and showed significant startup issues which were not observed during ground testing due to gravitational effects. CAPL-1 (Butler, Ottenstein, and Ku, 1995) flew in 1994 (STS-60) and showed significant startup issues which were not observed during ground testing due to gravitational effects.…”