Exactly one year ago, the Isothermal Dendritic Growth Experiment (IDGE) completed its third and final orbital space flight aboard the United States Microgravity Payload (USMP) on STS-87. The IDGE conducted 180 experiments on dendritic growth in 5-9's succinonitrile (SCN), a BCC material used on USMP-2 and USMP-3, and over 100 experiments on 4-9's pivalic acid (PVA), an FCC material used on USMP-4. IDGE film and telemetry data provide benchmark tip velocity and radii versus supercooling for critically testing transport theory and the interfacial physics of diffusion-limited dendritic growth. Post-flight application of optical tomography is providing the first tip shape data allowing quantitative tests of three-dimensional phase field calculations. Several new discoveries were made during each flight concerning the behavior of dendrites at low driving forces, and the influences of time-dependent pattern features and noise. A summary of these scientific highlights will be provided.
The IDGE instrument was upgraded on each successive flight, improving its optics and electronics, especially the capability for teleoperational control. Near real-time, full gray-scale video was accommodated on USMP-4, allowing investigation of non-steady-state features and time-dependent growth dynamics. A short example of video from space will be shown. USMP-4 science was teleoperated by a student cadre for 16 days from a remote site established by NASA at RPI. This operational experience provides valuable insights, which will be drawn upon for future microgravity experiments to be conducted on the International Space Station.