Experiment-to-Experiment Disturbance of Microgravity Environment

The STS-87 Shuttle mission carried the Fourth United States MicroGravity Payload (USMP-4) as one of the primary payloads. Four USMP-4 science experiments were installed on two carriers in the cargo bay of the Shuttle. The Confined Helium Experiment (CHeX), located on the aft carrier, was particularly susceptible to vibrations in several frequency ranges due to structural resonances of the CHeX apparatus and the extreme sensitivity of the sample to vibrations. Shortly after activation of the USMP-4 payload, a strong, vibratory disturbance within the susceptibility region of the CHeX apparatus was detected. After investigating the characteristics of the disturbance and the time at which it first appeared, it was deduced that the vibration was generated by cooling fans in the Isothermal Dendritic Growth Experiment (IDGE). This paper will summarize the development of the conflict, briefly describe the disturbance source, and the susceptibility of the CHeX apparatus, and summarize the results of post-mission tests of IDGE.