HOUSTON - As the crew of the international space station prepares to kick off a blitz of spacewalks for construction and repair work, U.S. and Russian space officials have finished negotiating what at first may seem a trivial question: What suit to wear to the party?
Although the ultimate solution took some hard bargaining, the results underscored yet again the importance of having two independent spacewalk capabilities from the station. NASA's spacesuits, known as Extravehicular Mobility Units, or EMUs, require astronauts to use the station's U.S.-built Quest air lock. Russia's Orlan suits are built for Russia's Pirs docking module. All station crew members are cross-trained for both systems.
The “party” in question will be the last in a series of four spacewalks set to begin on Wednesday. During the fourth spacewalk, scheduled for Feb. 22, Russian cosmonaut Mikhail Tyurin and American astronaut Michael Lopez-Alegria are to make another attempt to free a jammed antenna strut at the back end of Russia’s Zvezda service module. They failed to budge the mechanism during their first try, back on Nov. 22, but the crew took 35 digital photos of the antenna for ground analysis.
The strut, mounted on an unmanned supply ship, did not retract prior to its docking last October and is now lodged underneath a handrail. Russian engineers fear it could tear loose and leave behind jagged metal that could endanger future spacewalkers — or even worse, could cause the departing vehicle to tumble while it was dangerously close to the station.
“Now we have a clear picture of what happened,” Nikolai Sevastianov, the head of Russia's Energia rocket company, told reporters this month. “If necessary, the cosmonauts will apply tools to release the jammed antenna” in order to prepare it for undocking on April 8, a day before the planned launch of the next Soyuz crew.
The case for the U.S. suits
Initially, NASA had proposed that the antenna removal work be performed in U.S. suits. There were many attractive features of this option:
- The suits are already scheduled to be used during the first three spacewalks in the coming month's series. Adding a fourth would take only a few days of servicing and refurbishment. In contrast, activating and testing the stowed Russian suits would take two crew members the better part of a week, and there wasn’t that much slack in the crew’s time line.
- The U.S. suits come equipped with “helmet cams” that send live images to Earth, where specialists can observe the delicate work and make real-time suggestions. The Russian suits do not have that capability, and the back end of the service module is out of sight of all exterior television cameras. As a result, the ground would have very little insight into the progress and problems of the repair work, and would have to rely totally on oral descriptions.
- There is a communications requirement that any Russian spacewalk occur on those several orbits each day that cross directly over Russia. This meant the astronauts would have to go through several hours of "sleep shifting" — that is, going to bed and getting up significantly earlier — to make the transition from the U.S. spacewalks to the Russian spacewalk.
- American operators remember the still-unresolved issue of
Because the first attempt to free the antenna failed, several tools from the American kit were selected for the second attempt. These include some powerful pry bars and bolt cutters. However, the tools would work just as well whether the astronauts were wearing U.S. or Russian suits.
In addition, there was at least one “political” factor. NASA owed Russia a spacewalk, from the time when the station's gyroscope guidance system needed serious repair but American spacesuits were inoperative. NASA had to ask the Russians to use their spacesuits to get to the U.S.-built module needing repair. The Russians had made various monetary suggestions for cashing in the IOU — and a one-for-one swap of equivalent services would probably be the cheapest way for NASA to redeem it.
But in a series of meetings over the New Year holiday, Russian officials insisted on using their own suits — and argued strongly that it was, technically, the correct choice.
The case for the Russian suits
They pointed out that although Tyurin was familiar with the U.S. suit, he was not fully qualified for it and had never used it for an actual spacewalk. Since he would be the lead spacewalker on the Russian hardware repair, the Russian side argued that he should be using equipment he’s most familiar with.
It also turned out that NASA would have needed a lot more work to develop and verify a safe route from the Quest hatch all the way to the Russian end of the station. This is a non-trivial challenge — American operators refer to that area bristling with antennas, spars and stand-off docking targets as “the hanging gardens.”
Slideshow 12 photos
Month in Space: January 2014
And because the crewmen would be over the back edge of the station and out of line-of-sight contact with antennas on the distant Quest module, there was some question that the helmet cams would even function reliably.
Nor was the still-resolved “phantom torque” problem as serious as it had once been. The Russian side had developed an entirely new software package for using maneuvering jets on docked Progress robot freighters to orient the entire station, and they deliberately chose jets at the back ends of these vehicles so they would be as far as possible from any nearby spacewalkers (and also pointed away from newly deployed solar wings, as well). It is less efficient than more direct methods, but that’s only a matter of a few extra pounds of gas in tanks that will get burned up anyway when the supply ships dive back into the atmosphere.
During the last spacewalk to inspect the jammed Kurs antenna, flight controllers in Houston noticed that the torque — which built up rapidly when the men first got there — could be automatically counterbalanced by the station’s autopilot over time. Since the men remained stationary for an extended period of time, and the "phantom torque" thus stayed fairly constant, the autopilot’s response was effective.
As for the extra time, the Russians agreed to absorb it all from their own schedule of assigned work-hours. A number of Russian experiments and internal crew systems improvements will have to be delayed until the next crew arrives in April.
“Ultimately, those conservative types over there elected to dance with the devil they know rather than gamble with a make-better,” one flight controller told MSNBC.com privately. “It may crunch the schedule, but they think it has a higher probability of success.”
That success, in turn, is founded on the availability of two totally independent spacewalk systems on the station, a design feature that originally looked duplicative and wasteful. In recent years, temporary troubles with one or the other system threatened the schedules for critical spacewalk repairs — and each time, the availability of an alternate exit pathway saved the day.