Title: Microgravity Testing of Phase Change References on the International Space Station
Author: Shane Topham
Organization: Space Dynamics Laboratory
Co-Authors: Fred Best

Orbital sensors that will monitor global climate change during the next decade are exacting low drift rates from their onboard thermometry that is unattainable currently without some means of on-orbit recalibration. Phase change materials (PCM) such as those that make up the ITS-90 are seen as the most reliable references on the ground and good candidates for orbital recalibration references.

The University of Wisconsin and Space Dynamics Laboratory have both been developing miniaturized phase change references capable of deployment on an orbital blackbody for more than six years. A critical question remains to be answered to determine their potential utility as orbital references. How, if at all, will the microgravity environment affect the phase transitions?

To answer this question three experiments will be conducted on the international space station. Through long-time contacts at the Institute for Biomedical Problems (IBMP) in Moscow Russia, SDL has negotiated all of the flight qualification, launch and return vehicles, and crew time necessary to carry out these experiments. The experiments will test melts and freezes of three different phase change materials in various containment apparatus.

A brief history of the development of PCM references for space implementations, descriptions of the experiment hardware, microgravity considerations for the experiments, current status of experiments, and results from pre-launch ground testing will be presented.