Krikalev replaced a liquid processing component of the Russian Elektron oxygen generation system on Thursday, but it failed almost immediately prompting additional troubleshooting Friday. The system separates hydrogen and oxygen molecules from water, and injects the oxygen into the Station's atmosphere. Late Friday systems experts in Russia reviewed information gained from the earlier efforts. Oxygen is being supplied as needed from tanks in the Progress cargo ship, one of several oxygen supplies available.
Phillips was called upon to do some on-the-spot maintenance of a balky treadmill on Friday. It had stopped working, so he inspected electrical connections and prepared to downlink data from his last run so that biomedical engineers on the ground can try to track down the problem. Resistive exercise equipment and stationary bicycles will be used to provide the 2 1/2 hours a day of exercise prescribed for each crew member.
Also Friday, both crewmembers used the Robotics Work Station in the Destiny laboratory module to guide the Station's Canadarm2 robotic arm through movements designed to enable later remote operation by ground controllers. The hour-long session also served as proficiency training for the crew.
Earlier in the week, Krikalev fixed the Russian dehumidifier by clearing blockage from one of the system's lines. Krikalev also transferred wastewater from the Station into the Progress cargo ship's storage tanks. Phillips packed items that will be returned to Earth on the Space Shuttle Discovery, and did routine checks of emergency medical equipment. Scientific investigations for the week focused on work with a kidney stone experiment. Both crew members took pills - either a placebo or potassium citrate, which has been proven effective in reducing the formation of kidney stones in patients on Earth - recorded what they ate and drank and collected urine specimens for 24 hours. The samples will be returned to doctors on the ground for analysis and correlation with the dietary intake information.
Expedition 10 Commander Leroy Chiao and Flight Engineer Salizhan Sharipov remained at the Gagarin Cosmonaut Training Center in Star City, Russia, undergoing medical examinations and debriefings following their landing in a Soyuz spacecraft after six-months on orbit. They are expected to return to Houston in mid-May.