Assembly (Nearly) Complete
NASA's space station manager looks back with satisfaction at one of history's greatest construction projects.
- By Paul Hoversten
- Air & Space magazine, May 2011
Almost finished: NASA's Michael Suffredini, with a model of the International Space Station.
NASA/Paul E. Alers
When Mike Suffredini joined NASA in 1989, planning for the International Space Station was already well under way. This year, as the program's manager, he'll have the satisfaction of seeing the orbiting outpost finally completed after more than a decade of construction. This year's winner of the National Air and Space Museum Trophy for current achievement (on behalf of the space station program), Suffredini spoke with Executive Editor Paul Hoversten in January.
Air & Space: Before assembly began on the International Space Station, there was a lot of concern about the complexity of the project. Were those worries overblown?
Suffredini: I wouldn’t say they were overblown. There were an enormous number of spacewalks involving very complicated tasks. What happened was, we took heed and did a lot of work to try to mitigate the risks. Along the way, we added some training, particularly with the ammonia quick disconnects [used to cool station modules] which are difficult to operate on orbit. We did quite a bit of work on the ground to verify how the systems were going to operate on orbit before we flew them. So we took a number of steps to make sure we could accomplish all the objectives.
A & S: Did any surprises pop up during construction?
Suffredini: There were times when we found it more difficult to manipulate a mechanism. The use of the quick disconnects was a challenge. Over time, we’ve had challenges with many of the devices we had to manipulate, such as the power connectors, the ammonia connectors, and the bolts we drove. One surprise we had with the big external drill driver we use to drive bolts, was we found that we had a calibration issue and weren’t torquing the bolts to the right level. So we had to go back and retorque some of them.
A & S: Which element was the toughest to install?
Suffredini: Probably Node 2 [delivered by the STS-120 crew in October and November 2007]. Not because it was more difficult, but because when we came up, we docked where Node 2 ultimately had to go. So we installed it on a temporary port, on Node 1. And while it was docked there, we had to connect power to keep it warm enough. Then the shuttle left, and we had to disconnect the port we were docked to. During an EVA [extravehicular activity or spacewalk], we had to grab that module, put it on the end of the U.S. lab where the docking module was, then put the docking module on the end of Node 2. Then we had to hook up all the ammonia and power lines and all the rest of the reconfiguration.
A & S: How hard was it to ensure that modules and connectors built in different countries would fit together in space?
Suffredini: Yeah, and keep in mind that no two modules or trusses ever physically saw each other before they got to orbit. We had a test jig that that we brought for every common berthing mechanism interface, the way the modules tie to each other. And then the segment-to-segment systems, the way we put the trusses together. For every system, we had a test jig that we put up to it that drove the bolts and made sure everything was right. For avionics, in some cases we did integrated testing on the ground where we just ran wires from modules to modules or modules to trusses to confirm that those systems worked.
A & S: How has the ISS managed to avoid the sort of calamities, such as a fire, that occurred on Mir?
Suffredini: We learned a lot from Mir with our Russian counterparts, and we’ve tried to take all of our knowledge over the years and use that in deciding how we’re going to build and operate a space station. Every single thing that flies to the station gets assessed for its flammability and off-gassing. You know how you paint your house and it smells; with a space station you can’t air it out. We worried about toxicity and stowage. We put in smoke detectors. Most importantly were the steps we’ve done to mitigate our design. To make sure we have oversized wires so you don’t get inadvertent warmups, and to make sure our cables are built carefully so you don’t have a concern for short circuits. By design, you can’t cause a fire [aboard the ISS] with a short circuit. In the case of Mir’s fire, that was specific to their oxygen generation system, which is a common system by the way. It’s used in the Navy on our subs.
A & S: Early ISS crews used to spend a good part of each day maintaining the station. How has that changed, even as the station has grown?
Suffredini: In the early stages, we were learning about the systems. A lot of them were new, and we were working the bugs out. We’ve gotten pretty experienced now, and we’re just about done with the assembly. So that has helped us learn when we need to do preventive maintenance. You haven’t noticed it as much because we have six crewmen now.
A & S: There’s been talk of extending the mission until 2020. How likely is that to happen?
Suffredini: I think it’s very likely. We’ve pretty much gotten indications from our lawmakers and from our partners that they’re willing to do that. When we did our analysis, we looked at a total 30-year life, from the first element launch in November 1998. So that takes you to 2028 and our analysis is we make it to 2028. The system will be fine. Although it’s not formalized in some of our agencies, all the agencies have indicated an interest in extending [the ISS] to 2020.
A & S: Will station crews continue going up for six-month stays?
Suffredini: From an ISS operational and research standpoint, six months is a pretty good stay. It takes one to two months for a crew to get really efficient. They have to learn where everything is, how to bounce around, what order they have to do things, all the procedures. You want them efficient, but you don’t want to wear them out. Eventually, I could see us extending an increment crew to longer than six months to practice and train for long-duration spaceflight like a trip to Mars. But if we’re just doing normal research, then six months is a good way to rotate your crews.
A & S: Will the size of the crew come down?
Suffredini: No. In fact, we’re designed on the U.S. side to take four crew. The ISS design is actually for seven. We operate with six because first, we can get all our work done with six, and second, we don’t have a vehicle that allows us to fly a seventh crew member. Our requirement for the new vehicles being designed is for four seats. So I don’t expect us to go down in crew size. I would expect us to increase it.
A & S: Will the ISS be the last space station we build?
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