Spaceflight Now STS-100

Spacewalkers play electricians outside station

Posted: April 24, 2001

Scott Parazynski works as an electrician to wire up the base of Canadarm2 to the Destiny lab module. Photo: Spaceflight Now/NASA TV
Two spacewalking electricians wired the international space station's new robot arm into the lab's power grid today, completing the $900 million crane system's initial installation after extensive troubleshooting to activate an initially dead backup circuit.

"And Endeavour, Houston, great job," astronaut Ellen Ochoa radioed from mission control when juice finally started flowing through the backup power cable. "We're all celebrating down here."

"That's great. That's just outstanding news," replied spacewalker Scott Parazynski.

Station astronaut Susan Helms, the robot arm's primary operator, then powered up the crane for its first attempt at heavy lifting. To the delight of flight controllers following along in Houston, the arm smoothly lifted a 3,000-pound cargo pallet away from the station's main lab module.

"I'm absolutely ecstatic," lead flight director Phil Engelauf told reporters later. "I think this was just a red letter day in the program, just an absolutely wonderful experience. We got to where we wanted to be at the end of the day. ... We just got everything done we could have hoped for today and a little bit more. The mission is headed for great success."

Added space station flight director John Curry: "We got our money's worth today. Both flight control teams and the crews - the spacewalk crew, the Expedition Two crew as well as the shuttle crew on orbit - just did an outstanding job.

"It's just incredible to me we're sitting here having accomplished nearly all of the goals we set out to do today given the challenges we had."

The 57-foot-long Canadarm 2 space crane was launched unpowered and folded up on a Spacelab cargo pallet in the shuttle Endeavour's payload bay. The crane itself is valued at roughly $600 million while attachments that will be added later push the cost to nearly $900 million, according to NASA officials.

During a news briefing by Canadian Space Agency officials before the shuttle Endeavour's launch, reporters were told the space station's new Canadian-built robot arm cost $1.4 billion in Canadian dollars. That works out to about $900 million U.S. for design, development and fabrication.

As it turns out, that cost covers the entire crane system, that is, the arm launched aboard Endeavour; a mobile platform that will be launched later to carry the arm along the station's central truss; and a fine-precision robot hand attachment called a dextrous manipulator. A CSA representative said today the Canadian project will total nearly $900 million U.S. over the entire 20-year course of the project.

The pallet was mounted on the hull of the station's Destiny lab module Sunday and the robot arm's two main booms were unfolded and bolted together by Parazynski and Canadian Chris Hadfield during the mission's first spacewalk.

Helms powered up the new crane Monday, unlatched one end and locked it on a power and data grapple fixture on the far side of Destiny's hull.

The high-tech PDGF is designed to provide power to the crane and to relay telemetry and video from four television cameras back to operators inside the station.

The robot arm can lock onto such grapple fixtures with either end, allowing it to move around the station end over end to reach various work sites.

The primary goal of today's spacewalk, the 104th in U.S. history and the 20th devoted to space station assembly, was to connect two power lines just under the lab module's outer skin to route power to the PDGF.

Other objectives included removal of a no-longer-needed UHF radio antenna and attachment of a spare 400-pound direct current switching unit on the station's hull.

Parazynski had no trouble hooking up the primary and secondary power lines for the Canadarm 2 space crane. Helms, inside the Destiny module, then attempted to route so-called "keep alive" power through the backup cable. But the line was dead.

She then routed power to the primary cable. To everyone's relief, electricity finally began flowing.

"Good keep alive on the prime string," Helms reported.

"We copy, very good news," Lisa Nowak replied from the ISS control center.

"We feel a little relieved, too," Helms agreed.

Confident the arm had at least one good source of power, flight controllers told Parazynski to unplug both the primary and secondary cables, inspect the connectors and then plug them back in. He did just that, but there were no obvious signs of trouble.

Helms reconnected both circuits and again, the primary system worked, the backup did not.

Increasingly concerned engineers then asked Parazynski and fellow spacewalker Chris Hadfield to begin unplugging and reconnecting other cables in the secondary circuit, starting with the horseshoe-shaped connecter used to hook the secondary cable directly into the arm's grapple fixture.

The fixture was installed during a shuttle flight earlier this year and the cable in question was bolted into place during that flight.

Using a power wrench to back off the connector's central hold-down bolt, Parazynski unplugged the cable, did not see any problems with the connecter, and plugged it back in. This time, when Helms switched the power back on electricity flowed into the arm.

"And Endeavour, Houston, great job. We're all celebrating down here," astronaut Ellen Ochoa radioed from mission control.

"That's great. That's just outstanding news," Parazynski replied.

Curry said engineers suspect the connector was never fully engaged when it was installed earlier this year.

While all of that was going on, Hadfield was removing the UHF antenna from the Unity module's starboard hatch. While disconnecting the antenna feed lines, a washer-like fastener somehow floated free and disappeared behind thermal covers over the port's berthing mechanism. Hadfield made numerous attempts to recover the lost part, but he was unsuccessful.

The Canadarm 2 robot arm is made up of two long booms connected by a rotating elbow joint. Both ends of the crane are equipped with snare-like grapple fixtures and either one can be used to anchor the crane on a power and data grapple fixture. The other end can then be used to grab station modules, hardware or astronaut work platforms.

The arm draws power from the PDGF and uses it to send video and data back to the arm's operator inside the station. Only one such PDGF is currently installed.

But the station eventually will be equipped with a dozen or so PDGFs. The arm will be able to move from one to another, end over end, to reach various work sites.

Before the arm and its operators can run, however, they must first learn to walk. And today, the arm "switched ends" for the first time when Helms lifted the no-longer-needed Spacelab pallet away from the Destiny module.

With the arm and pallet well out of the way, Parazynski and Hadfield attached the spare DC power switching unit to the station's hull before heading back to Endeavour's airlock.

The spacewalk officially began at 8:34 a.m. and ended at 4:14 p.m. for a duration of seven hours and 40 minutes. Through 21 space station assembly EVAs, 19 NASA astronauts, one Canadian - Hadfield - and one Russian cosmonaut have logged 138 hours and 50 minutes of spacewalk time.

If all goes well, Helms will use the station's new arm to hand the Spacelab pallet back to the shuttle's shorter robot arm Wednesday so it can be restowed in Endeavour's cargo bay for return to Earth. The huge crane will begin assisting in actual space station assembly in June, when Helms will use it to attach the station's main airlock.

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