Scientists study unusual gel material aboard station
Posted: January 31, 2002

Operations continued on the slow fractal sample initiated earlier this month by the Experiment on Physics of Colloids in Space (EXPPCS) science team.

The first attempt at mixing a colloid with a salt to initiate fractal gel growth began Jan. 16. Although all mechanical components worked properly, a tiny rubber valve that had been clamped closed failed to unseal after unclamping during the mixing operation. A second mix of the salt with the colloid was successful and clustering of the colloids was immediately detected. The clumping of the colloids to form a gel is continuing normally, the science team reported. The team completed a 12-hour run on Sunday and a 24-hour run on Tuesday. The next test is scheduled for Friday, Feb. 1. Scientists hope the fractal network will eventually span the entire sample cell to form a gel as they continue to record the process.

This microscopic image of a colloidal gel taken on the ground is a snapshot of the formation process being studied in the Experiment on Physics of Colloids in Space on board the International Space Station during Expedition Four. Credit: Harvard University
Fractal research is expected to continue for eight weeks. A fractal is something that appears to have the same structure under different degrees of magnification. One example is the coastline of a continent. Maps showing 25 miles or 250 miles of coastline will appear somewhat similar in the apparent amount of roughness.

Scientists are interested in studying the fractal structure of this colloid gel, which is 99.992 percent water and only 0.008 percent colloid. Among their questions is whether something with so little material will be able to form a gel. They are also studying aging of the gel.

Fractal gels are of interest to manufacturers and materials specialists on Earth. A primary mechanism for degradation of motor oil is the formation of fractal clusters of soot. Another example is the aging and spoilage of food. Fractal gels are also found in a specialized material known as aerogel, which is only 0.5 percent solid and possibly the best thermal insulator known. EXPPCS is managed by NASA's Glenn Research Center in Cleveland. The principal investigator is David Weitz of Harvard University.

"The fundamentals of fractal structures are well understood, but the applications of these amazingly low density materials is poorly understood and relatively untapped," said Art Bailey, senior scientist with the colloids experiment with Harvard University. "The research we are conducting to explore the limits of fractal behavior will play a role in the expanding the areas of application beyond petrochemicals and food."

Astronauts Dan Bursch and Carl Walz on Saturday, Jan. 26, tested themselves with a lung function experiment called Pulmonary Function in Flight (PuFF). PuFF studies possible changes in lung function due to microgravity inside the Space Station, as well as the low pressure environment of the space suits used aboard the Station. The test followed Bursch's spacewalk last Friday and served as Walz's regular monthly test.

On Tuesday, Jan. 29, the crew collected background radiation readings of the radiation badges with the EVA Radiation Monitoring (EVARM) experiment. The badges are stowed in pockets in astronauts' cooling undergarments to measure radiation dosages at specific areas of the body. Bursch on Tuesday also logged in diet and other data for the Renal Stone experiment, which is testing a possible preventative for kidney stone formation in space. He and Walz are performing the second session of the experiment this week.

The Active Rack Isolation (ARIS) team is working to learn the cause of a broken pushrod on the experimental vibration dampening device. Bursch reported a noise on Thursday, Jan. 24, during crew sleep. He later determined that the pushrod on the upper right side of EXPRESS Rack 2 was broken. It is one of eight pushrods designed to keep the rack and delicate microgravity experiments inside isolated from vibrations caused by crew movement, equipment vibration and other disturbances. The science team is working with Station controllers to remove and replace the broken pushrod with a spare today (Jan. 30). The crew is being consulted on details of the damage. On-orbit inspection with close-up photos may reveal more. A pushrod also broke during Expedition Three due to a loose nut designed to hold it in place, but Bursch and Walz reported Saturday that it was tight when they inspected it. Expedition Three Commander Frank Culbertson, who performed the pushrod repair on his expedition, talked with the current crew on Tuesday to pass on his experience.

Planners have moved up operations with the Earth Knowledge Acquired by Middle School Students (EarthKAM) one week early to Monday, Feb. 4, to allow for a full four-day operation without communications outages expected during the original operating period. EarthKAM allows middle school students to send photography targets to a camera onboard the Station to support a variety of classroom studies. Since Expedition Three, several new schools in the United States have joined the program as well as school in Germany.

Recent photos of Materials International Space Station Experiment (MISSE) show that one of the samples may be peeling off. More photos may be taken during a February spacewalk to learn more. MISSE is a suitcase-sized package of experimental spacecraft materials.

The list of sites for the Crew Earth Observations photography research this week include ice in the South Sandwich Islands, industrialized Southeast Africa, brush fires and smoke in Angola, water levels in Lake Eyre in Australia, and Patagonian glaciers in Chili.

Editor's Note: The Payload Operations Center at NASA's Marshall Space Flight Center in Huntsville, Ala., manages all science research experiment operations aboard the International Space Station. The center is also home for coordination of the mission-planning work of a variety of international sources, all science payload deliveries and retrieval, and payload training and payload safety programs for the Station crew and all ground personnel.