From: ISS Science Operations News
Posted: Friday, September 27, 2002
Science research bubbles aboard International Space Station
The crew of the International Space Station this week continued their research into unwanted bubbles that can become defects in metal alloys used to produce jet engine turbine blades and semiconductor crystals for electronic devices. Space Station science experiments and payload operations are managed by the Payload Operations Center at Marshall Center.
Flight Engineer Peggy Whitson and the science team on Earth conducted the second experiment with the Pore Formation and Mobility Investigation (PFMI) on Monday and Tuesday.
The PFMI research, conducted in the Station's Microgravity Science Glovebox, began with an initial test run last Thursday. The experiment is designed to study bubbles that can become trapped in metal alloys used to produce jet engine turbine blades and semiconductor crystals for electronic devices. Using a furnace to melt samples of a transparent modeling material, scientists on the ground can watch via video downlink as bubbles form, move and interact in the samples before they cool down and re-solidify.
"We melted the sample and were re-solidifying it but the drive motor did not move the sample forward as it should to initiate controlled freezing," said Dr. Richard Grugel, PFMI lead scientist at NASA's Marshall Space Flight Center in Huntsville, Al. "We are not sure if it's a mechanical or software issue, but we fully processed half the sample, and it looked very good. Qualitatively, we're in agreement with the theoretical predictions. We can't compare bubble size and temperature gradients until we can fully evaluate the video and thermal data on the ground. The key point is to get the hardware back up and running.
"The experiment run was also interrupted by a temporary loss of Ku-band communications coverage, which allows scientists to command and monitor the experiment. The science team and ground controllers are troubleshooting the drive motor behavior this week. The next PFMI science run is planned for Monday, Sept. 30.Bubbles are more likely to get trapped in samples processed in space.
Bubbles trapped in metals or other manufacturing materials are defects that can diminish a material's strength and usefulness, whether it's processed on Earth microgravity, which makes the Space Station a good place to study their movements and interactions. Information collected from PFMI is expected to provide insights into the processing of metals and alloys in space and on Earth.
PFMI includes 15 samples. Each sample tube is 0.39 inches (1 centimeter) in diameter and 7.87 inches (20 centimeters) long. The research is sponsored by NASA's Microgravity Research Program at the Marshall Center and by the Office of Biological and Physical Research in Washington, D.C.
Also on Tuesday, Whitson continues removing fluid from the Advanced Astroculture experiment as part of the plant preservation and drying process for ending the experiment and preparing it for return to scientists on Earth.
On Wednesday and today, selected members of the crew participated in the weekly Crew Interactions survey, a computer-based questionnaire intended to identify and characterize important interpersonal and cultural factors that may affect the performance of the crew and ground support personnel during Station missions.
On Friday, the crew will take pre-spacewalk readings of the EVA Radiation Monitoring badges worn in the U.S. EVA suits.
The crew and ground controllers last week completed a series of hyperextension and bumper containment tests with the Active Rack Isolation System in preparation for upcoming Zeolite Crystal Growth experiments. After testing, analysis of the test data by experts on the ground indicated something was constraining the free movement of the rack. Whitson was requested to adjust the computer laptop cables and search for any other potential interferences.
ARIS is located in EXPRESS Rack 2 and uses a system of sensors, actuators and pushrods to isolate the rack and delicate microgravity experiments inside from any vibrations caused by crew motion, operating equipment and other low frequency disturbances. The system required recalibration after the rack was moved August 31 to repair a smoke detector.
"We commanded the actuators and pushrods through their full range of motion to make sure that the bumpers re-installed after the smoke detector repair properly limited rack motion and protected the ARIS hardware," said Jim Allen, ARIS project manager with The Boeing Company in Houston.
Photography subjects for the Crew Earth Observations project this week included: the Lower Amazon River basin, Buenos Aires in Argentina, Lake Poopo in Bolivia and Lake Eyre in Australia.
The crew continued its daily payload status checks of automated science payloads to make sure that all experiments and payload facilities continue to operate properly. Completed Expedition 5 experiments currently awaiting return to Earth include: Microencapsulation Electrostatic Processing System, Stelsys, and Zeolite Crystal Growth.
// end //