Saturday's spacewalk to fix a ripped solar panel on the International Space Station might be likened to threading cords through grommets of a camping tarp – except that the "tarp" was gently waving and electrically charged and the "repairman" was standing on the top rung of a stepladder attached to another stepladder.
The repair means the panels will be able to provide electricity for the space station. But it also points to the vital role that on-orbit maintenance will play – and the exacting demands it imposes – as visionaries set their sights on outposts and factories on the moon or Mars or on hotels and commercial laboratories orbiting high above Earth.
For engineers, the long-term challenge is to design simpler, more forgiving hardware for use in space. But for those dreaming of living on and beyond low-Earth orbit, Saturday's spacewalk is a reality check about what it takes to keep deep-space facilities running – and about the risks to people and investments if repairs fail.
The solar-panel spacewalk was "really kind of a wake-up call," says Adam Bruckner, who heads the aeronautics and astronautics department in the University of Washington's College of Engineering. Concepts for colonizing the moon or for commercial facilities on orbit "are interesting," he says, "but when you actually ... think about doing it over there, a lot of the maintenance ... and operational problems have been swept under the rug."
As reality TV, "Survivor" has nothing on Saturday's webcast of the tense, seven-hour spacewalk by astronauts Scott Parazynski and Col. Douglas Wheelock. Earlier in the week, the shuttle and station crews had moved a solar-panel assembly from a temporary spot on the ISS to its permanent location at one end of the station's backbone, or truss. As the space-station crew tried to unfurl the panels on Oct. 30, segments of one of the assembly's four wing-like arrays snagged and ripped, halting the deployment.
From engineers on the ground devising a repair strategy to Dr. Parazynski himself, the repair effort stretched everyone and everything to their limits, notes Derek Hassmann, the lead flight director for the shuttle mission.
Parazynski made the repairs farther from the airlock than any astronaut had ever been, his boots locked onto an extension at the end of a 50-foot boom. The station's robotic arm, in turn, gripped the boom like a relay runner's baton. (Picture those stepladders stacked one atop another.) Colonel Wheelock, meanwhile, tethered himself to the truss at the base of the solar array to serve as spotter for Parazynski and the crew members operating the robotic arm.
Once near the panel, the 6-foot, 2-inch Parazynski stretched to his physical limit in order to thread cuff-link-like cords through grommets in the array, which held it together when he cut the frayed wire that had snagged the segments. Each step required subtle moves by the boom operators. Parazynski had to remain close enough to the array to do the work. But he also had to keep far enough away to avoid the risk of electrical shock from the "live" solar cells or further damage to the array as the boom and array shifted back and forth in response to his movements. The boom-robotic arm combo stretched to within two inches of its maximum reach.
Typically, astronauts spend weeks, even months, training for an assembly spacewalk that makes no use of robotic arms, says Mr. Hassmann. For Saturday's spacewalk, a small army of engineers and astronauts in the US, Canada, and Russia worked around the clock to devise the repair strategy and to make or modify the tools needed to pull off the repair.
"People always said that we're going to encounter problems we can't even think of right now and have to be ready for them in some way," says Tom Jones, a former shuttle astronaut who conducted spacewalks to help attach the US lab module Destiny to the space station in 2001. "Well, here it is, that actual unexpected. And it always throws everybody a curve. We'd better get used to this."
The farther from Earth astronauts travel, the more acute maintenance challenges become, notes Larry Bell of the Sasakawa International Center for Space Architecture at the University of Houston.
Planners try to build redundancy into critical systems and to provide the tools and materials for making some repairs. Indeed, one tool Parazynski used to handle the undulating solar array took shape from a sheet of Teflon and some insulating tape in the space station's workshop. But mission planners always face a trade-off between trying to plan for maintenance needs and keeping materials within the weight limits during launch.
Especially when talking about trips to the moon or Mars, "it's a long way back to the hardware store," Dr. Bell says.
For the people involved in such repairs, coping requires several things, specialists say. Managers must make quick decisions about which problems are most crucial to fix, for instance. Crew members must be sufficiently trained and practiced in generic mechanical and spacewalking skills to allow them quickly to adapt what they've learned to unforeseen problems.
As for hardware, Russia's experience with the Mir space station may hold some lessons, Dr. Jones suggests. Its space-station segments essentially were plug-and-play; no spacewalks were needed to make the newly attached modules habitable. But that meant snaking power and cooling lines inside the hull, something ISS designers tried to avoid for safety reasons as well as for more flexibility in configuring the station's various elements. Still, it will be important to reduce the number of adjustments or amount of handwork newly arriving crew members must perform, Jones says.
What comes through loud and clear is that just as the 30-year-old space shuttle remains an experimental craft, the space station as well as habitats on the moon and Mars are, and will be, experimental in their own ways.
"In space, there's no such thing as run-of-the-mill," Dr. Bruckner observes.