Microgravity research included a session with the semiconductor crystal-growing experiment known as Solidification Using a Baffle in Sealed Ampoules, or SUBSA. Whitson set up and activated the experiment in the Microgravity Science Glovebox inside the Destiny laboratory. In the experiment, semiconductor samples are heated to their melting point and allowed to cool and solidify. Whitson downlinked television pictures of the experiment, which thanks to a transparent furnace design allowed scientists to see the solidification of indium antimonide crystals in space for the first time. The objective is to develop techniques for making larger, purer semiconductors for a variety of computer and electronics applications on Earth.
Whitson also took electronic images of soybean plants growing in the Advanced Astroculture experiment package, which scientists on the ground used to confirm that the plants have begun to flower. Scientists hope to develop soybeans with improved oil, protein, or carbohydrate content as a result of this research, which will feature the first seed-to-seed grown of soybeans on orbit.
All three crewmembers worked with biological experiments associated with their upcoming spacewalks on Aug. 16 and 23. They took turns blowing into a tube attached to sensitive instruments on the Pulmonary Function in Flight, or PuFF, experiment, which looks at the effects of spacewalks and long-duration spaceflight on human lung function. They also took background radiation readings that will help to calibrate readings from sensors that will be placed in pockets on the liquid cooling underwear they'll use during the spacewalks.
Korzun and Whitson will make the first foray out of the Russian Pirs docking compartment and airlock to install panels designed to protect the Zvezda living quarters from space debris, as well as a new set of Russian materials samples to be exposed to the rarified atmosphere of atomic oxygen at the station's altitude of 242 statute miles. Korzun and Treschev will make the second excursion, installing similar samples in a Japanese experiment and two additional amateur radio antennas.
The workweek began with removal and replacement of remote power converter modules in the Quest airlock. The modules had been exhibiting signs of malfunction, and although recoverable, these signs led engineers on the ground to recommend their replacement. Korzun and Whitson completed the swap, and flight controllers in Houston confirmed that the new units appear to be working properly. The older units will be returned to Earth for detailed inspection and analysis.
Mission Control also followed up on repair work on the Carbon Dioxide Removal Assembly by Korzun and Whitson. The pair had replaced one of two absorbent beds for the system last week. On Tuesday, flight controllers attempted to activate the replacement bed, which contains Zeolite crystals to absorb the excess carbon dioxide breathed out by the crew. But the replacement bed showed signs of leakage similar to that seen from the original bed, but at a lower rate. Life support systems engineers on the ground suspect there may be another leak elsewhere in the CDRA that was not corrected by the bed replacement, but are still studying the data and considering further options. They verified that the system can still function properly with just one bed in operation. In the meantime, scrubbers in the station's Russian segment continue to provide all of the carbon dioxide removal required by the Expedition 5 crew and visiting taxi crews.
On Thursday, the crew reported hearing "clattering" noises as they ran or walked in place on the Treadmill Vibration Isolation System. As a result, exercise on that equipment was suspended. Instead, the station inhabitants will use a variety of other stationary bicycles and resistive exercise devices to maintain their cardiovascular health and muscle tone. Treadmill experts on the ground are working to replicate the problem on a duplicate TVIS so that they can design an effective repair.
A full-up fire drill and checkout of emergency equipment such as fire extinguishers and portable breathing apparatus made sure that Korzun, Whitson and Treschev are ready to respond in the unlikely event of a fire inside the station.
The crew wrapped up its work week filming demonstrations for Toys in Space, an educational outreach project intended to inspire students to study science, engineering and mathematics so that they can become the next generation of space explorers. They operated toys, such as yo-yos, gyroscopes, soccer balls and a miniature hockey game, documenting the way the toys react in microgravity.
Russian officials conducted routine Progress thruster manifold tests in preparation for a reboost of the International Space Station about 11 a.m. CDT Aug. 1. The reboost will put the station at the best altitude to welcome the next unpiloted Russian Progress supply spacecraft and Soyuz crew return vehicle in September and October.