STS-90 Day 9 Highlights

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On Saturday, April 25, 1998, 1:00 a.m. CDT, STS-90 MCC Status Report # 16 reports:

Due to problems with equipment which removes carbon dioxide from the cabin atmosphere, Columbia's crew went to bed about two hours late Friday and will awaken at 6:39 a.m. CDT, about an hour later than originally scheduled.

The crew's sleep period was scheduled to begin at 9:39 p.m. CDT Friday, but at about 10:45 p.m. CDT, the Regenerative Carbon Dioxide Removal System aboard Columbia shut down, ringing a cautionary alert onboard. Flight controllers asked the crew to switch to a second set of control electronics for the unit and restart it. However, about 10 minutes later, the equipment shut down again. At that point, flight controllers asked the crew to install backup carbon dioxide-absorption canisters in the laboratory and crew cabin. Called lithium hydroxide canisters, a supply is stored aboard Columbia as a backup to the recyclable system which shut down.

The lithium hydroxide canisters are not recyclable and must be replaced daily with fresh canisters as they become saturated with carbon dioxide. Members of the crew were still awake when the problem occurred, with some crew members still wrapping up science work in the payload bay laboratory.

The crew was never in any danger due to the equipment problems and carbon dioxide levels in the crew cabin always remained normal. Flight controllers will continue to evaluate the problem with the recyclable carbon dioxide removal system and may ask the crew to perform further troubleshooting activities after they awaken. Due to the later wake-up time, a few activities planned for early in the crews day have been canceled, including a ship-to-ship conversation by the crew of Columbia with astronaut Andy Thomas on Mir.

However, members of the crew remain scheduled to talk with students in three events during the day. Commander Rick Searfoss, Payload Commander Rick Linnehan and Payload Specialist Jay Buckey will speak with students at the McAuliffe Planetarium in New Hampshire at 11:39 a.m. CDT. Canadian Space Agency astronaut Dave Williams will speak with students at York University in Ontario, Canada, at 3:49 p.m. And Buckey will talk with students at Dartmouth College at 4:34 p.m.

And, from Mir, Thomas remains scheduled to answer questions sent to him by Australian school students at 9 a.m. CDT

On Saturday, April 25, 1998, 7:15 a.m. CDT, STS-90 MCC Status Report # 17 reports:

The STS-90 astronauts will begin the start of their second week of on-orbit science operations today, and also will support some troubleshooting procedures following the shutdown of a carbon dioxide removal system last night.

Flight controllers on the ground continue to review data associated with the Regenerative Carbon Dioxide Removal System (RCRS) unit aboard Columbia which shut down late last night. Engineering teams will meet this morning to consider what troubleshooting activities they may ask the crew to undertake later today to try to recover the RCRS system.

With the regenerative system at least temporarily unavailable, the crew has installed the backup carbon dioxide-absorption canisters in the laboratory and crew cabin. A supply of 28 lithium hydroxide canisters is available aboard Columbia. The canisters are a passive and very reliable CO2 removal system.

Should a decision be made that the RCRS system cannot be recovered, the 28 lithium hydroxide canisters available onboard Columbia would allow about five more days of science operations to be conducted before the mission would have to be concluded. Approximately four canisters are needed each day to support the removal of CO2 from the crew cabin and laboratory environments. Eight canisters would be held in reserve to support the two day landing wave-off reserve in case weather or technical problems delayed Columbias return to Earth.

Crew members also may work with an air circulation fan associated with the Rodent Animal Holding Facilty (RAHF) being carried in the Spacelab. Data indicate that a fan associated with RAHF unit #7 may no longer be working. These fans are important to the health of the animals being carried in the RAHF as they deliver fresh air into the RAHF and facilitate the removal of CO2. Current plans call for the crew to run a malfunction procedure to determine if the #7 unit fan has in fact failed. If it has, the crew will then perform an in-flight maintenance procedure to set up a bypass system that will allow the fan in RAHF unit #3 to support the #7 unit.

Science operations for Flight Day Nine will include continued work with the ball catch experiment which is part of the Sensory Motor and Performance Team. The ball catch experiment utilizes an apparatus that propels a ball from above in a downward motion toward a seated astronaut. Investigators will monitor the astronauts performance to see if the crew uses visual cues to compensate for the cues missing in a microgravity environment.

The crew also will perform more work with the Effects of Gravity on Postnatal Motor Development Experiment which is one of the Mammalian Development Teams projects. Ground research has indicated that gravity plays a significant role in how rats learn basic motor skills such as swimming and walking. The rats being studied in this experiment were launched when they were only a few days old and scientists will be looking to see if motor skills develop normally in the weightless environment. The rats will be videotaped as they move around in a special walking apparatus that has various surfaces to allow them to walk and climb. Additional motor skill tests will be performed after the flight to see if the rats are able to readapt to the force of gravity.

Columbia remains in a 153 x 133 nautical mile orbit, circling the Earth every 90 minutes.

On Saturday, April 25, 1998, 6:30 p.m. CDT, STS-90 MCC Status Report # 18 reports:

A one-inch piece of aluminum tape and a measure of ingenuity by engineers on the ground today breathed new life into the STS-90 Neurolab mission.

Commander Rick Searfoss opened up a balky Regenerative Carbon Dioxide Removal System (RCRS) aboard Columbia about 3 p.m., removed a hose clamp and used the tape to bypass a suspected check valve that had threatened to cut the flight short by several days. The valve, part of the air-scrubbing systems plumbing that recirculates nitrogen back into the cabin atmosphere, apparently was allowing cabin pressure to leak into the system and throw off its electronics control unit.

Half an hour later, Mission Control told Searfoss the repair had succeeded after watching the system go through one of its 26-minute operational cycles. The RCRS system uses two beds of the chemical amine to alternately adsorb and release excess carbon dioxide given off by the crew and the research animals on board as part of their normal respiration. With the bypass in place, the system will vent about four extra pounds of nitrogen overboard each day. But nitrogen supplies on board are sufficient to support a full 17 days of research if mission managers decide later this week to grant an extension day.

Crew members also restored air circulation to one of the Research Animal Holding Facilty (RAHF) pens being carried in the Spacelab. The fan associated with RAHF unit #7 stopped working and they set up a bypass system that is allowing the fan in RAHF unit #3 to support the #7 unit.

Science operations for Flight Day 9 included continued work with the ball catch experiment which is part of the Sensory Motor and Performance, and the Effects of Gravity on Postnatal Motor Development Experiment that is one of the Mammalian Development Teams projects. Columbias astronauts also spoke with Astronaut Andy Thomas, nearing his 100th day on the Russian Space Station, and answered questions posed by visitors to the New Hampshire McAuliffe Planetarium, and from students at York University and Dartmouth College.

Columbia remains in a 153 x 133 nautical mile orbit, circling the Earth every 90 minutes. The crew will begin its sleep shift at 9:19 p.m. A planned half day off on Sunday will be moved to the first half of the crew's day so that they may sleep in after losing about an hour of sleep because of the RCRS shutdown on Friday night. The next STS-90 status report will be issued about 6 a.m. Saturday or as events warrant.

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