Spaceflight Now: Space Station/STS-98

Space station gyros spin up in successful test

Posted: February 13, 2001

Computers in the newly installed $1.4 billion Destiny laboratory module began controlling the international space station's orientation for the first time today, spinning up four massive, fuel-saving gyroscopes in a critical milestone for the orbiting complex.

Assuming tests and checkout operations go well - and so far, the computer-driven gyros are performing flawlessly - day-to-day operational control of the station will shift from Russian flight controllers to NASA shortly after Atlantis departs Sunday.

Illustration of the station at the completion of Atlantis' visit. Photo: NASA
"We're extremely pleased with how well all of the station operations have gone to this point," lead station flight director Andrew Algate told reporters. "This has been an amazingly complex mission when you look at all the new systems being activated ... and all those things have come together just as it was planned.

"It says a lot for the folks in the program and at Boeing, who designed the software and hardware and tested it and put it all together, as well as the operations folks who built the procedures to use it. So we're just extremely pleased at this point."

The only problem of note so far has been the apparent failure of a vacuum pump in a critical carbon dioxide removal system, one of three components in a rack of equipment inside the Destiny module.

During the rack's activation overnight, a flight controller "noted that a pump that evacuates some of the lines for normal operations did not come on so we commanded a shutdown of the system from the ground," said Algate.

"Right now, the engineering community is off looking at what the options are, what we should try to do next. There's no real rush to try to come to a resolution of this problem. The normal CO2 removal system for this timeframe is up and operating in the Russian segment just as it was prior to the lab docking."

The Russian system he was referring to is known as the Vozdukh. A spare Vozdukh was carried into orbit aboard Atlantis, but it has not yet been installed. The case it was packed in for launch turned out to be too large to fit through the hatch into the station and the astronauts will first have to remove it from its casing.

With one fully operational Vozdukh, a healthy spare and enough lithium hydroxide on board for two weeks of emergency carbon dioxide removal if necessary, Algate said the station has plenty of redundancy and there is no great rush to fix the U.S. CO2 scrubber in Destiny.

"This is something we'll want to get resolved, but it's not a piece of equipment that's needed in the short term," he said.

The major items on the agenda today were boosting the station's altitude another 4.6 miles; activating a new S-band audio communications system that uses NASA's Tracking and Data Relay System satellites; and spinning up the gyros for attitude control.

The upgraded communications gear will allow station crews to talk with flight controllers in Houston up to 70 percent of each orbit, a vast improvement over the limited time available for communications through Russian ground stations.

Likewise, activation of the gyro control system marks another major milestone in the station's development.

Up until this point, the station's orientation has been controlled by a computer system in the Russian Zvezda command module that orders periodic rocket firings to nudge the 105-ton station into different attitudes as required.

By switching to gyro control, station crews can conserve propellant and avoid jarring rocket firings that would disturb sensitive microgravity experiments.

During the first two-orbit test of the gyro system early today, one in which thrusters were occasionally fired to keep the gyroscopes properly aligned, only a half kilogram of propellant was needed.

"In that test, we used about one eighth of the propellant we'd been using previously for station control," said lead station flight director Andrew Algate.

"This afternoon, we're going to start another test of the control moment gyros and in that test they control in a mode that normally uses no prop at all."

The guidance, navigation and control computers also provide the capability to track the sun with the station's huge P6 solar arrays.

Stretching 240 feet from tip to tip, the solar arrays were installed during a shuttle flight last December. Until now, the electricity generating panels have been manually oriented as required.

"Having the guidance and navigation computers up also gives us a capability on our solar arrays to automatically point at the sun and they're now operating in that mode and that lets us produce power more efficiently," Algate said. The gyroscopes were attached to the station last fall as part of the Z1 structural truss on the upward-facing hatch of the Unity module. But the gyros could not be operated until arrival of the computers in the Destiny module.

The lab was attached Saturday, the computers were powered up and checked out and overnight, the gyros were spun up to their operational speed of 6,600 rpm for today's testing.

If all goes well, the gyros will remain in control until early Wednesday when attitude control will shift back to Atlantis for the third and final spacewalk of the STS-98 mission.

During an in-flight interview today, spacewalker Thomas Jones said the lab module's smooth testing was the result of rigorous pre-launch testing and he urged NASA to continue that practice for all subsequent flights.

"My hat's off to all the people who put in so many thousands and thousands of hours and days getting the lab ready," Jones told CBS News. "I saw it when it was just a shell, a metal cylinder, over in Huntsville, Ala., and the people there worked really hard to ship it out to the Cape about two-and-a-half years ago.

"The people at KSC took the lab, which was about half finished, and completed its testing and a very rigorous end-to-end testing program that we as a crew participated in.

"And that's the essential thing that we want to keep practicing in the future," Jones said. "There's no substitute for practicing through the actual vehicle the actual procedures we plan to carry out on orbit. We did that in Florida and that's got to be the case for other elements of the space station."

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