Heading into the homestretch of their 6½-month mission
aboard the International Space Station, Expedition 8 Commander
Michael Foale and Flight Engineer Alexander Kaleri spent the week
conducting biomedical experiments and performing maintenance on a
key Station component.
Foale and Kaleri spent two days replacing a liquids unit and a
water flow system in the Russian Elektron oxygen-generation device
in the Zvezda Service Module after weeks of troubleshooting efforts
failed to coax it back into service. The Elektron produces oxygen
for the Station atmosphere through electrolysis – the
separation of hydrogen and oxygen from water that flows through a
series of pumps and valves. The hydrogen is vented overboard.
Russian specialists spent several weeks trying to track down the
most probable cause for repeated shutdowns of the system after just
a few minutes of operation each time. They concluded that particles
of potassium hydroxide electrolytes – a by-product of the
electrolysis process – that created air bubbles in the
liquids unit, resulting in the unit’s repeated shutdowns,
were the most probable cause of the problem.
Since last Saturday, the crew has derived oxygen from solid-fuel
oxygen generation (SFOG) canisters activated in Zvezda. The crew
has been using an average of two SFOGs each day since available air
and oxygen were depleted from tanks in the Russian Progress supply
vehicle following the first shutdown of the Elektron.
Russian engineers now plan to activate the refurbished Elektron
Saturday for a few days of checkouts and diagnosis. If the Elektron
repair proves successful, the SFOG canisters will no longer be
needed. There is an ample supply of those canisters, as well as
oxygen contained in the Quest airlock tanks, that could provide
oxygen for the Station for several months.
To accommodate the Elektron repair, a few lower-priority tasks
were moved to other days, including routine proficiency training
for Foale on the Canadarm2 robotic arm.
On Friday, Foale did a leak check of the window in the Destiny
laboratory. In January, a flex hose that helps to vent air from the
inner panes of the window was found to be causing a minor pressure
decay from the Station. The flex hose was replaced a few weeks ago,
and the leak check revealed an airtight system.
Foale and Kaleri took advantage of the recently repaired
high-tech treadmill to get in several rounds of intense exercise. A
lengthy overhaul last week brought the system back into full
Foale spent some time this week conducting experiments with a
cellular biotechnology device to test methods for improved cell
culture growth and with a device designed to measure the forces
imparted on the joints of the lower extremities and the feet in the
absence of gravity.
Foale and Kaleri also took time out from their schedule to
answer questions from a syndicated talk show host from the Premiere
Radio Networks and from students at the Howard Bishop Middle School
in Gainesville (FL).