The designers at Boeing Co.'s Rocketdyne Division (Canoga Park, Calif.) are riding high, thrilled that the power system they crafted for the International Space Station is working successfully in orbit after almost a decade of development on earth.
Many of the engineers at Rocketdyne have worked on nothing else over that span. While some have moved on, others will help maintain the space station indefinitely, spending the bulk of their careers with a single program that presents an unusual set of design challenges.
"I think this is the most ambitious project ever undertaken, to build and assemble something 200 miles out in space," said Sandra Stoller, electrical-cabling project engineer at Boeing. "Then you have to think about the environment this has to survive in, and that it has to last several years. Just designing to withstand the launch loads is very challenging."
Many of the power-system engineers at Rocketdyne have attended launches. Watching a liftoff brings dry technical specifications forcefully to life.
"Seeing and feeling the launch is just amazing," said system engineer Patrice Dupass. "You can feel your clothes move, you can feel it in your chest. And that's when we're miles away from the actual launch site."
Surviving the vibrations of liftoff is not the only thing that separates the Rocketdyne design from power systems destined for more mundane equipment. For starters, the space station's lifetime is pretty much indefinite. And the temperature range it's built to endure 250°F to --250°F isn't quite within normal component specifications.
"One thing that's unique about the space station is that it's got a 15- to 30-year lifetime," said Fred Cohen, product engineer. "The components have to last that long, and the modules must be restorable indefinitely. Things will change, modules will be replaced in orbit. A big challenge is to be robotically accessible. Another big difference is that the thermal interfaces we design for are not anywhere close to standard."
Above all, there's the knowledge that when astronauts are aloft, they can't dial 911 or Jiffy Repairs if a fire starts or something breaks. Near-fatal problems with Russia's Mir spacecraft and, earlier, the U.S. Apollo 13 spacecraft are a constant reminder that the engineers' work could ultimately mean life or death for someone.
"Not one of us goes through the door now without realizing that there are people living up there every day," Stoller said.
That means paying attention to all kinds of details most engineers never have to think about and explains, at least in part, why the development cycle is so long.
"If qualification for man-rated missions extends even to the batteries used in a camcorder, we have to look at the possibility that a battery leak in the flight cabin could get in an astronaut's eye," Cohen said. "That's not likely to happen in our lifetime, but if it's a possibility, we have to consider it. It can take two years to get through a safety review. The schedule is so stringent for that exam that we cannot even get on the schedule until we're on the manifest to fly."
The Boeing engineers often meet with the astronauts themselves to make sure their designs can be easily manipulated in space. The International Space Station is being assembled by floating people in bulky pressure suits, so parts must be easy to handle.
"The astronauts officially have final say on what goes up," Cohen said. "They work with things and give us suggestions. There's a large swimming pool in Houston, and the astronauts assemble things in the pool to simulate weightlessness."
While the bulky space suits are a hindrance, weightlessness can be a plus. The Battery Orbital Unit designed by Rocketdyne weighs in at 365 pounds. It has to be moved from the space shuttle into the space station for installation, but that can be done with a gentle nudge once the craft is beyond the pull of the earth's gravity.
The unit's battery modules and dc/dc converters are key to the power system. The modules are recharged by solar arrays during the 55 minutes of sunlight the space station experiences during its 90-minute orbit. The battery system is based on thirty-eight 1.25-volt battery cells linked in series, ganged together with a second module.
If the space station is perhaps the most challenging technical site ever created, it's not the most cutting-edge. Some of the systems are one of a kind, but much of the technology is old hat. Indeed, many of its microprocessors are of the 386 vintage, the Boeing team said.
"This may be older technology, but it's very robust," Stoller said. "Part of the initial philosophy was that we would use tried-and-true hardware. We did not intend to push the envelope. The integration is state-of-the-art, but the components are not necessarily the latest."
As the various space shuttles took off to deliver equipment to the space station, life became intense for the engineers at Boeing. Many spent extra time at work. And duty demanded they be ready to help out in the event there were questions that only the designers could answer.
"We had to have 24-hour coverage," Cohen said. "If you weren't in one of the special rooms around here, you had to have an electronic leash, and you had to answer a call within 15 minutes. People were here all night long, sometimes even when they weren't on call." Everyone gathered in the office "when they turned on the dc-to-dc converter," Stoller said. "There was not a dry eye in here when it worked. That's our baby."
Undoubtedly the space station will reap many scientific benefits over the next few years. But even now, the Boeing crew believes it has already had an impact.
"If nothing else, this got a lot of people, especially children, interested in space," Dupass said. "Even my hairdresser gets excited if there's a fly-by. That's pretty important to us, and it's important for the country to get people interested in technology. There's a lack of a technically skilled work force."
Reactions at Rocketdyne to the recent plunge into the South Pacific of the Mir spacecraft indicated where the designers' hearts lie. "I think about the Russian engineers who have devoted their lives to that. To see it come to an end has to be hard," Stoller said. "We have worked with the Russians a fair amount."
But the look back was fleeting. "Mir was a great learning platform," Dupass said. "But for the space station, this is a good deal." With Mir gone, "The Russians are now focusing their efforts on the space station."