"Just take it real slow," said Atlantis pilot Mark Polansky, who was directing the test from inside the shuttle's crew cabin. "No rush."

"Mission Control concurs," astronaut Mario Runco chimed in from NASA's Mission Control Center at Johnson Space Center in Houston, Texas.

Coming at the end of NASA's milestone 100th spacewalk, the so-called "Dead Guy Test" was meant to simulate action that would have to be taken if a spacewalker somehow became incapacitated while carrying out construction or maintenance work outside the outpost.

The going was tough at times for both astronauts. Floating in weightless space, each found it difficult using one of two techniques tested to make their way to safe harbor while pulling his partner along with a leash.

"Man, that's a job I wouldn't want to have all day," Jones said.

The disaster drill capped the last of three spacewalks planned for the Atlantis crew's weeklong visit to the station, now occupied by U.S. astronaut Bill Shepherd and two Russian cosmonauts -- Yuri Gidzenko and Sergei Krikalev.

The station's first full-time tenants continued outfitting the newly arrived U.S. Destiny science laboratory while the spacewalking work unfolded outside the outpost.

Job Number One for the spacewalkers was stowing a spare communications antenna on a girder-like outpost truss. Curbeam used a pistol-shaped power tool to bolt the antenna in place and then yanked it back and forth to make certain it was secure.

"Shake test, and it's definitely not going anywhere," Curbeam reported.

"Beamer slammed it in there -- gently, of course," added Jones.

"Outstanding," Runco exclaimed. "You guys are awesome."

The spacewalkers then unlatched a station radiator and watched on as it unfolded in orbit, the crew inside the shuttle having sent the requisite computer commands to deploy it. A wowed Jones called the resulting view "out-of-this-world."

"That's an understatement," Curbeam said with a laugh.

"Man, that radiator is reaching right out to the horizon," Jones added.

~

Next up: Inspections of quick disconnect fittings on four ammonia coolant lines between the $1.4 billion Destiny lab and the end of the station's Unity module, where the bus-sized research facility was mounted last Saturday.

One of the coolant lines sprang a leak of toxic ammonia that day as Curbeam was rigging it up. A cloud of frozen ammonia crystals enveloped Curbeam, prompting an unprecedented decontamination effort as he and Jones wrapped up their first excursion outside the station.

Wielding cameras tethered to their suits, the astronauts snapped pictures of the coolant line connectors, which appear to be properly mounted. No coolant leaks were evident.

With cameras in tow, Curbeam and Jones then scaled to the top of the 17-story outpost and took pictures of a metal latch at the base of the station's massive American-made solar wings, which stretch 240 feet (73 meters) from tip to tip.

One of four such latches, the device failed to firmly lock into place during a station assembly mission in December. The pictures are meant to help engineers figure out how to fix the latch during a future flight.

The lofty photo opportunity, meanwhile, afforded the two spacewalkers a spectacular panoramic view from a perch 90 feet (27 meters) above the black-and-white nose of Atlantis.

Said Jones: "This is high country up here."

Some electrical work followed as Curbeam and Jones checked out power cables routed between the lab and a shuttle docking port mounted to its end.

Then came the emergency drill, which involved testing two methods for hauling an incapacitated spacewalker back into the shuttle's airlock.

The so-called "daisy chain" method called for Curbeam and Jones to hook their own waist safety tether to their "unconscious" partner and then tow the limp crewmate into the airlock.

In the other -- known as the "strap method" -- Curbeam and Jones were told to form a rope-like loop with the passive partner's waist tether. The spacewalker playing the role of lifesaver then placed his arm inside the loop as if he were carrying a purse.

Both spacewalkers found the "strap" method the more difficult of the two -- primarily because it afforded little breathing room between the astronauts.

"I can tell you already it's much harder to control his body position with the strap method," Curbeam told ground controllers. "I'm working a heck of a lot harder on this run than the last one -- much harder."

Added Jones: "The daisy chain keeps you out free and floating clear."

Runco and astronaut Greg Harbaugh carried out a similar test during a January 1993 shuttle mission, but the drill largely was considered a bust. The two astronauts tried to pull themselves down the shuttle's sidewall with one hand while tugging their partner along with the other -- a method that proved too difficult to rely on in a real emergency.

This time, however, the drill went relatively smoothly. And that was welcome news to Harbaugh, who now serves as chief of NASA's spacewalk projects office in Houston.

"I feel much more comfortable today that we are in a position to take care of somebody if we should ever find ourselves in posture where they might need some assistance returning back to the safe harbor of the airlock," he said.

~

Coming 36 years after Edward White exited a Gemini capsule for NASA's very first EVA -- or Extravehicular Activity -- the 5-hour, 25-minute excursion marked the agency's 100th walk in the deadly vacuum of space.

The first 40 of those spacewalks were carried out during NASA's Gemini, Apollo and Skylab programs, and 60 since have been staged from U.S. space shuttles.

The two Atlantis spacewalkers took time at the end of their sortie to mark what Curbeam called "a golden anniversary of sorts."

Displaying a commemorative sign outside shuttle windows, Jones and his partner tipped their helmet visors in a tribute to the thousands of NASA and contractor workers that have been involved in spacewalking work to date.

What's more, they predicted that future spacewalks would take astronauts to work sites far beyond the current outpost construction zone some 230 miles (368 kilometers) above the planet.

"We think that in the years to come -- in the very near future -- we'll see not only the construction of the space station completed, but spacewalkers will take their place not only in low Earth orbit, but back on the Moon, and on asteroids and perhaps even on Mars," Jones said. "We look forward to that day, and we're ready for this next century of EVA."

"Great words, Atlantis," Runco replied. "We look forward to 100 more."

Said Jones: "Hope we can be a part of that."

The spacewalk Wednesday was the 16th to be carried out as part of a 16-nation effort to build the international station, which eventually will weigh 480 tons and span an area nearly as large as two football fields set side by side.

And with another 152 still required to finish the station over the next five years, spacewalking excursions will become the rule -- rather than the exception -- until the outpost is completed in mid 2006.

Nineteen more spacewalks -- or a total of 22 -- are to be carried out at the station this year, compared to nine in the year 2000, a tally that tied a longstanding NASA record.

The spacewalking workload then will ramp up in fast fashion: 29 sorties are scheduled in 2002 and 43 are on tap for 2003. The next year will be relatively light, with 17 spacewalks planned in 2004, and station construction will be capped with 30 excursions in 2005.

"So you can see that the pace is quickening, and it's not going to get any easier. We've got our work cut out for us," said veteran NASA spacewalker Michael Lopez-Alegria.

Lopez-Alegria noted that spacewalking work at the station to date largely has come off without major problems -- a small miracle considering the degree of difficult and potential dangers involved in any venture into open space.

Maintaining that record, however, is not expected to be an easy task.

"We have to keep our fingers crossed," Lopez-Alegria said. "It's kind of like an undefeated team. The streak can only go on for so long. But so far, so good."

Hatches between Atlantis and the international outpost -- which also is known by the radio call sign "Alpha" -- swung open for a third time late Wednesday afternoon so the joined shuttle and station crews could continue outfitting the Destiny lab.

That work will continue Thursday as the two crews spend their final full day together in orbit.

Atlantis remains scheduled to depart the station Friday after a final farewell and hatch-closing ceremony set for 7:18 a.m. EST (12:18 GMT) that day. The shuttle and its crew are due to land at Kennedy Space Center at 12:52 p.m. EST (17:52 GMT) Sunday.