Monday, October 29, 2007

Working the Bugs Out In Space

If you see metal shavings in the oil you change out of your car, that's not an encouraging sign. But what if your vehicle cost several billion dollars and is flying hundreds of miles above the ground at fifteen thousand miles an hour? That is the problem faced by the engineers and astronauts trying to build the International Space Station.

News reports this week say that space shuttle Discovery mission specialist Daniel Tani opened a plastic cover on a gearbox during a spacewalk to reposition some solar panels. He was following orders from ground engineers who had noted excessive vibration and power consumption from the motors that move the 30,000-pound solar panels so as to collect the maximum amount of sunlight. Inside the box, Tani found an abundance of metal shavings, and collected some for analysis back home.

Everything is harder in space: repairs, inspections, lubrication, and even engineering and design. Although there are a few expensive giant vacuum chambers around that let engineers test satellites and other small to medium-size objects in something close to the reality of space, these don't simulate zero-G conditions. So the only way to check out most space-bound systems in 100% realistic conditions is to fasten them on a rocket and send them out there to see what happens. This is one reason that space exploration is so expensive and fraught with failures.

Readers of this blog know that I have serious reservations about the continuing use of the Space Shuttle (it ought to be replaced yesterday, not in two or three years) and the wisdom of spending billions on a space station which is too shaky for really good science and too small for really meaningful colonization of space. All the same, it's good to know that when something goes wrong on a system as big as the Space Station, you can send up a guy to take off the covers and have a look around, even if the service call costs millions of dollars. Discovery's latest trip was not only for maintenance—it is part of a tightly scheduled program to keep the Space Station's construction on track for completion by 2010.

Since this effort is costing several countries (Russia, the U. S., Japan, and Canada are major partners) both money and lives (if you count those who died in the 2003 Columbia disaster), it is only reasonable to ask what good it is doing. There is a scientific answer, an engineering answer, and a political answer. As is the nature of these things, they all blur into each other.

The scientific answer is, so far, not much. I cannot think of a single major scientific discovery that has resulted from work performed directly by astronauts, as opposed to research enabled by the Hubble Space Telescope or other unmanned lunar and planetary probes. This of course may change once the station is "completed" (such a project is never really finished for good, but the bulk of work will eventually shift from construction to use). But right now, it's too early to say if there will be any significant scientific payoff from the project at all.

From an engineering standpoint, building and operating the space station can tell us loads about the problems of building and operating a space station. We've had a smoke problem, a computer problem, and now a ground-up-gear problem, possibly, and those are only the ones that made headlines. As the first system of its kind, the International Space Station is bound to have all kinds of engineering issues that we can learn a lot from, assuming we try to do something like this again. As every engineer knows, the first time is mainly learning from mistakes. If your funding goes long enough to let you try a second time, you have a chance at getting it mostly right.

From a political view, the space station is an experiment in international cooperation on an intensely complex technical project, and by and large, this aspect of it seems to have gone well. When the U. S. manned space program went on hold for two years after the Columbia disaster, the Russians stepped up to the plate and kept the station in business with Soyuz launches. So far, the politicians have mostly kept out of the way of the committed engineers and managers in all the countries involved who want to see this thing go. Engineers have a way of forgetting about nationalities or political differences when they share a common technical goal, and the International Space Station is a good example of how that can work.

In the meanwhile, there's the question of where all those metal shavings are coming from. The ten-foot boxes that serve as pivots for the large solar panels could be replaced, I suppose, but that would be a major undertaking. On the other hand, if the bearings freeze up that will severely limit the amount of electrical power available to the station. I hope this turns out to be something trivial, as one engineer on the ground hoped that the shavings were just chewed-up foil insulation. My instincts tell me that such a hope is wishful thinking, but we'll just have to wait and see.

Sources: The New York Times article describing the metal-shaving problem is at Wikipedia has a good articles on the International Space Station's history and construction.

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