Only six other women have participated in 159 U.S. spacewalks, and only one has gone on any of the 118 Russian spacewalks. A major reason for the lack of female spacewalkers is the spacesuit, which isn't designed for small sizes, said Piper, who is 5-foot-10.
"If you fit in a suit then the easier it is to work," she said.
Walking in space was hardly a reach for Piper, reports CBS News correspondent Peter King.
"Now I get to see how long my arms really are," Piper told Mission Control.
Piper was joined Tuesday by spacewalking veteran Joe Tanner on the first of three carefully choreographed spacewalks planned for the 11-day mission to attach a 17½-ton addition to the space station.
Piper rotated four solar array blanket boxes into position, appearing in spectacular video against the backdrop of the Brazilian rain forest and the Amazon River 220 miles below, says CBS News Space Consultant Bill Harwood.
The truss and still-stowed solar array blankets dwarfed Piper in the stunning video, giving viewers a taste of things to come when the solar panels are unfurled Thursday, stretching 240 feet from tip to tip.
Piper struggled a bit to push one of the two sets of solar array blanket boxes from the stowed to deployed position and Tanner had to lend a bit of elbow grease to get the job done.
"I guess all that weight room stuff was worth it," Tanner said.
"That's right," agreed "spacewalk choreographer" Dan Burbank inside Atlantis.
While the truss is weightless in space, it still has 17½ tons of mass.
Before they started, astronauts Steve MacLean and Jeff Williams, from inside the space lab, used the robotic arm to install the 45-foot addition on the left side of the space station's truss system.
The spacewalk started a short time later at 5:17 a.m. EDT. Tanner was first to enter the void of space tethered to the space station, followed by Piper.
"Welcome to the world of EVAs," Tanner told Piper, using the NASA term for spacewalks — extra vehicular activity.
Piper responded, "Aaah. Wonderful."
Tanner and Piper then started connecting wiring and cables to the $372 million truss segment that was moved Monday from space shuttle Atlantis' cargo bay to the space station's robotic arm. Wearing bulky suits and gloves, the spacewalking electricians also installed and disconnected bolts, connected tubes and activated latches — tasks that had to be performed quickly so the electronic components do not get cold.
The team worked briskly, at one point putting themselves 45 minutes ahead of schedule. But the work was demanding.
"This is a lot harder than it was in the water," said Tanner while hooking up a power cable, referring to the swimming pool where astronauts practice their space construction chores at the Johnson Space Center.
He jokingly radioed his crew mates inside the space station to "stick your head out the window so I can say 'hi!'"
Astronauts Burbank and MacLean planned to follow their colleagues with another spacewalk on Wednesday.
The crew got some welcome news while the two worked outside the space station early Tuesday. Burbank relayed news from Mission Control that Atlantis' heat shield is so trouble-free that NASA engineers don't see a need to examine it again for damage.
"That's wonderful," Tanner said. "That means we've got a good vehicle."
The astronauts spent the night inside the Quest airlock at a reduced pressure of 10.2 pounds per square inch to help purge nitrogen from their bodies, reports Harwood. The so-called campout procedure was designed to shave about an hour off the time needed to prepare for today's spacewalk while helping ensure the astronauts don't get decompression sickness working in their 5-psi spacesuits.