Spaceflight Now STS-110


Station's new mobile transporter takes a test-drive
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: April 15, 2002

Astronaut Carl Walz restarted rail service aboard the international space station today, sending a $190 million flatcar creeping down the length of the lab's new S0 truss, from one station to another, after tests were interrupted earlier in the day by a subtle glitch.

The mobile transporter itself is working flawlessly, but the effects of weightlessness, which cannot be fully simulated on Earth, are interfering with the operation of sensitive position sensors that provide feedback on the cart's location. The problem only occurs during an automatic sequence to lock the mobile transporter down at a work site. Flight controllers are able to latch it in place by manually uplinking commands.

"All the electronics, all the systems, all the software on the mobile transporter are working very well. There are no glitches," said Ben Sellari, the S0 launch package manager. "This is not a software problem. The system is operating exactly as we instructed it to. I think what we're finding out as we go through this is how the mobile transporter works in zero G."

The transporter eventually will be used to carry the space station's Canadarm2 crane to 10 different work sites on the completed solar array truss. Two such work sites are available on the S0 truss element currently in place, one on each end of the 44-foot-long beam. The transporter is designed to latch itself down at each worksite with up to three tons of force to provide a stable platform for the crane during future operations when it will be used to move massive outboard truss elements and other components into place.

The transporter is equipped with two magnetic sensors that detect the presence of a pair of magnetized strips at each work site. When both strips are detected, the transporter's control software knows it is properly positioned to being the latch-down procedure. But during today's initial operation at work site 4 on the starboard side of the truss, the sensors apparently lost contact with the strips as the latches engaged, presumably because the cart floated upward very slightly.

After lengthy troubleshooting, engineers decided to order the latches to disengage and when they did, the correct position indicators reappeared. Confident the cart was in the proper position all along, controllers successfully sent commands to manually drive the latches closed to verify their operation. They then ordered the latches to disengage and Walz, sending commands through a laptop computer, ordered the transporter to move back down along the track to the far side of the truss to work site 5.

Again, the movement itself was smooth and again, the position indicators lost lock as the latches were engaged by the automatic software sequence. Ground controllers took over the operation as before, sending commands to manually engage the latches, before having Walz send the cart back to work site 4 where it will remain until the next shuttle visit.

"The mobile transporter, of course, is a very complex piece of machinery," Walz told . "I think it has some 20-odd motors that control its motion and also the latching systems. And when it did move, it was almost anticlimatic. It started to move very, very smoothly - and of course, very, very slowly - and then it got into position and started to latch and something went wrong with the automatic software. Bt the ground was able to latch it manually."

Asked if the initial failure made him a bit nervous, Walz said "we knew it wasn't going to keep rolling right off of S0. So we were fairly confident we were in a safe configuration. We called the ground and they started to do the troubleshooting. So our hearts really didn't skip a beat because we knew it wasn't going to continue moving. But we certainly were concerned, we always want to see the hardware check out the first time."

Sellari said engineers ultimately may decide to modify the automatic sequence software to ignore the temporary loss of data from the magnetic sensors during the latch-down procedure.

Apollo 12 tribute DVD set

New! Featuring the jovial crew of Pete Conrad, Dick Gordon and Alan Bean, the Apollo 12 mission was struck by lightning shortly after liftoff but proceeded on the second successful exploration voyage to the lunar surface. This three-disc DVD brings the mission to life with extraordinary detail.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Fallen Heroes special patch
This special 12-inch embroidered patch commemorates the U.S. astronauts who made the ultimate sacrifice, honoring the crews of Apollo 1, Challenger and Columbia.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Women in Space
Women of Space: Cool Careers on the Final Frontier is for girls, young women, and anyone else interested in learning about exciting careers in space exploration. Includes CD-ROM.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Mars rover poster
This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
 Choose your store:
U.S.

Columbia Report
The official accident investigation report into the loss of the space shuttle Columbia and its crew of seven. Includes CD-ROM.
 Choose your store:
U.S.

John Glenn Mission Patch

Free shipping to U.S. addresses!

The historic first orbital flight by an American is marked by this commemorative patch for John Glenn and Friendship 7.
 U.S. STORE
 WORLDWIDE STORE

Final Shuttle Mission Patch

Free shipping to U.S. addresses!

The crew emblem for the final space shuttle mission is available in our store. Get this piece of history!
 U.S. STORE
 WORLDWIDE STORE

Celebrate the shuttle program

Free shipping to U.S. addresses!

This special commemorative patch marks the retirement of NASA's Space Shuttle Program. Available in our store!
 U.S. STORE
 WORLDWIDE STORE

Anniversary Shuttle Patch

Free shipping to U.S. addresses!

This embroidered patch commemorates the 30th anniversary of the Space Shuttle Program. The design features the space shuttle Columbia's historic maiden flight of April 12, 1981.
 U.S. STORE
 WORLDWIDE STORE

Mercury anniversary

Free shipping to U.S. addresses!


Celebrate the 50th anniversary of Alan Shephard's historic Mercury mission with this collectors' item, the official commemorative embroidered patch.
 U.S. STORE
 WORLDWIDE STORE

Fallen Heroes Patch Collection
The official patches from Apollo 1, the shuttle Challenger and Columbia crews are available in the store.
 U.S. STORE
 WORLDWIDE STORE

ERROR: Random File Unopenable

ERROR: Random File Unopenable

The random file, as specified in the $random_file perl variable was unopenable.

The file was not found on your file system. This means that it has either not been created or the path you have specified in $trrandom_file is incorrect.
Get e-mail updates
Sign up for our NewsAlert service and have the latest news in astronomy and space e-mailed direct to your desktop (privacy note: your e-mail address will not be used for any other purpose).

Enter your e-mail address:

Soviet Space
For the first time ever available in the West. Rocket & Space Corporation Energia: a complete pictorial history of the Soviet/Russian Space Program from 1946 to the present day all in full color. Available from our store.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Viking patch
This embroidered mission patch celebrates NASA's Viking Project which reached the Red Planet in 1976.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Apollo 7 DVD
For 11 days the crew of Apollo 7 fought colds while they put the Apollo spacecraft through a workout, establishing confidence in the machine what would lead directly to the bold decision to send Apollo 8 to the moon just 2 months later.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Gemini 12
Gemini 12: The NASA Mission Reports covers the voyage of James Lovell and Buzz Aldrin that capped the Gemini program's efforts to prove the technologies and techniques that would be needed for the Apollo Moon landings. Includes CD-ROM.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide


INDEX | PLUS | NEWS ARCHIVE | LAUNCH SCHEDULE
ASTRONOMY NOW | STORE

ADVERTISE

© 2014 Spaceflight Now Inc.