Action-reaction in space: the “gyrodine war” heats up
by James Oberg
|Lost in all of this exchange of complaints is the fundamental engineering problem of what actually is forcing the Russian thrusters to fire during spacewalks.|
American experts believe that water vapor jetting from a cooling unit in the backpack of spacewalkers is strong enough to turn the entire two-hundred-ton space station out of alignment. This overloads the American stabilizing gyroscopes and triggers the firing of Russian rocket thrusters. The effect has been noticed on past station spacewalks that use the Russian space suits.
For their part, Russian engineers believe a small air leak from their airlock hatch could be cause. Other Russian experts blame it all on a malfunction in the American gyroscopes (which Russians call “gyrodines”), with no Russian problem at all.
In a pre-flight interview February 3, veteran Russian cosmonaut Sergey Krikalyov, commander of the next space station crew, told me that he did not believe the American theory about the Russian spacesuit design causing the disturbance. “I have made seven spacewalks on Mir with that spacesuit,” he insisted, “and if there had been any thrust large enough to push the space station, I would have felt it.”
The latest round in this dispute occurred when an official at Moscow’s Mission Control Center talked with an ITAR-Tass reporter about an incident that occurred February 8 that had no connection with the spacewalk. “Following an incorrect command issued by Mission Control in Houston,” he complained, “all three working American gyrodynes ‘stalled’ because of an accumulation of kinetic moment and went out of control.”
“This happened immediately before a planned maneuver to change the ISS’s orientation,” he continued, “which is carried out by means of the engines on the Russian segment.” The thrusters had to hold the station stable for more than five hours while the gyroscopes were being realigned.
NASA had documented this incident in its daily internal “On-Orbit Status Report”. Its report on February 9 discussed the previous day’s rotation of the station to an Earth-pointed orientation, which was carried out normally with Russian thrusters to reduce stresses on the gyroscopes.
|“The MCC [Mission Control Center] does an extremely good job at minimizing the inevitable human error given the complexity and demanding constancy of the job,” said NASA’s Hartsfield.|
“An incorrect ground command caused unexpected CMG saturation and loss of [attitude control],” the report stated. Orientation then “was taken over automatically by the Russian thrusters and [half an hour] later returned to CMG Momentum Management.” The report added that the “excursion” (the NASA term for going out of alignment) cost about 13.6 kilograms of propellants, “on top of the 9 kg for the original maneuver.”
The NASA report’s account of the loss of the gyrodines occurring after the planned rotation is inconsistent with the Russian claim that it occurred prior to the rotation. Sources report the NASA description is correct.
NASA’s weekly station activity report on February 11 expanded on the internal report: “After a successful preplanned attitude transition maneuver last Tuesday, return of attitude control was interrupted when one of the Control Moment Gyroscopes (CMG) became saturated, or overwhelmed, and lost its ability to control the Station’s orientation,” the press release stated. “Attitude control was automatically taken over by the Russian Attitude Control System thrusters for about one orbit, using about 14 kilograms of propellant. The CMG saturation was the result of an incorrect ground command. The ground team recognized the source of the error and issued the command to properly reposition the CMG. The CMGs then resumed control and the thrusters were turned off. The crew’s workday was unaffected by the events.”
In an email exchange, NASA spokesman James Hartsfield elaborated: “Obviously, it did not have to happen, so the prop did not have to be used,” he explained. “But it did not cause any significant impact to the Station operations or to the crew or to long-term consumables planning,” he continued.
Such minor slipups occur in any complex control process, Hartsfield agreed. However, he insisted—and most space experts agree—that “the MCC does an extremely good job at minimizing the inevitable human error given the complexity and demanding constancy of the job.”
The space station’s Control Moment Gyroscopes (CMGs) are a set of massive spinning wheels. They rotate at a constant speed and their frames are shifted by motorized hinges in order to turn the entire station into desired orientation, or to resist other forces tending to twist it out of a desired orientation.
Four of them are installed aboard the station. First one and then another have broken down, threatening their ability to keep the station pointed properly. This raised the possibility that Russian rocket thrusters would be needed to fire much more frequently, depleting their limited supply of propellant. However, one spacewalk last summer repaired one of the gyroscopes, and while the remaining three are still sufficient for full control, the Russian rocket thrusters are now regularly used for the occasional routine orientation changes of the massive station in order to limit stresses on the NASA gyroscopes.
The American gyroscopes were also in the middle of a controversy that followed the most recent ISS spacewalk on January 26. As reported exclusively by msnbc.com, as astronaut Leroy Chiao and cosmonaut Salizhan Sharipov worked outside the station, a still-unexplained twisting force built up and overwhelmed the strength of the gyroscopes, and as a result the Russian thrusters fired automatically to relieve them. To American experts in mission control in Houston, at least some of these firings appeared to occur when the spacewalkers were dangerously close to the thrusters, threatening to contaminate their spacesuits with highly-toxic chemicals.
Russian officials angrily rejected that interpretation. Russian Mission Control Center spokesman Valeriy Lyndin told reporters in Moscow on February 1 that the spacewalkers were always warned of impending thruster firings: “Sharipov and Chiao were told the jets would be started,” he asserted. “They were even told to have a look at it, since it was going to be a nice show.”
|“Russian space experts consider that NASA recently is using any occasion in order to aggravate the situation around the ISS project,” according to one Russian reporter.|
Lyndin attributed the need to fire the jets to the inadequate strength of the American equipment. “Sometimes the gyroscopes accumulate too much kinetic energy,” he explained, “which has to be reduced by [firing] steering jets.” He added that this was “absolutely routine,” and claimed that the spacewalkers were nowhere near the thrusters when they fired.
But then the Russian complaints got nastier. Writing for the Russian national news website gazeta.ru, journalist Alina Chernoivanova quoted anonymous Russian space officials as calling the American suspicions “contrived” and attributing them to “failures in work with the ISS.”
“Russian space experts consider that NASA recently is using any occasion in order to aggravate the situation around the ISS project,” she continued. “That way, the American side probably is attempting to downplay its failures in the assembly of the station and to place itself in a more advantageous situation.”
“The international space program is not bringing NASA great success,” she wrote, and NASA is uncomfortable in the current situation where Russia is in the driver’s seat. This dims the prospect for future international project, she suggested, concluding that “for the American side, cooperation even in near Earth orbit is apparently given with difficulty.”
“We’re already used to similar complaints from NASA,” another source at the Moscow Mission Control Center told veteran space journalist Konstantin Lantratov. “There’s always something about our work that doesn’t suit them.”
“However,” Lantratov’s source continued, as reported in the February 2 issue of the daily newspaper Kommersant, “there are just as many complaints about their equipment as about ours.” As an example, he described how “even in this space walk, the American antenna periodically shut off due to overcooling, and we didn’t receive any TV pictures from the station.”
Lantratov’s source speculated on motivations for the NASA complaints. “There’s a general impression that because of the interruption of shuttle flights NASA is completely dependent on Russian support and uses even the slightest incident to show who’s boss there,” he rationalized. “Last December, they accused us of not taking stock of food aboard the station and the astronauts were in danger of going hungry. Now it’s the engines.”
What is so striking about this series of Russian press complaints, however, is what was consistently omitted from them. Not one Russian report mentioned the feature highlighted in the original msnbc.com story, that the original cause of the excessive strain on the American gyroscopes was a “phantom torque” probably connected with a malfunction of Russian equipment. In the version as portrayed in the Russian press, it’s as if the station was cruising along peacefully until somehow, out of the blue, the American stabilizing gyroscopes failed to perform adequately.
Nor is Lantratov’s reference to an American TV system partial failure a fair response. The reason that the US TV system was used at all—and it functioned for substantial periods of the spacewalk—is that the Russian’s own exterior television system and the satellite relay communications link are almost totally non-functional. After all, this was a “Russian spacewalk” that was supposed to be using Russian equipment, but their own television monitoring system couldn’t be used because it didn’t work at all.
|The consequences of this still-unsolved problem include significant impacts on crew safety in orbit and on the strained atmosphere of the US-Russian space partnership back on Earth.|
The most recent Russian complaint about the failed American gyroscopes did not allege that the problem was in any way life threatening. A Russian spokesman assured reporters that “the failure of the gyrodynes, which maintain the station in the required position in orbit, does not pose any danger to Salizhan Sharipov and Leroy Chiao”. He added, correctly, that “only three of the four gyrodynes are working at the moment, and we are trying not to overload them.”
For almost a week there was no public NASA or Russian response to the report February 10 on Alan Boyle’s “Cosmic Log” from an internal NASA status report. The “investigation has confirmed that at least one of the international space station’s astronauts [and possibly both] roamed into a “keep-out zone” (or KOZ, in NASA-speak) during a spacewalk last month. In a worst-case scenario, the spacewalkers’ Russian-made Orlan-M suits could have become contaminated with toxic fuel from the station’s thrusters.”
The joint investigation apparently ignored the public posturings of innocence in Moscow, acknowledged that the original NASA anxiety had been fully justified, and decided that spacewalk operations procedures needed to be improved. “Safety procedures are being modified on both sides to ensure future prevention of KOZ violation during spacewalks,” according to the internal NASA status report that described its findings. It added that “no traces of contamination on the [space] suits were found after the EVA incident,” but such contamination would be expected to evaporate over the course of the remaining spacewalk in any case.
Responding to a question at a scheduled press conference on February 17, NASA’s lead ISS flight director, Annette Hasbrook, confirmed that a joint US/Russian investigation team—she was the US rep, and Russian expert Yuri Surskiy represented Moscow mission control—had reviewed the video and the timeline of the EVA and had concluded that one of the spacewalkers (Chiao) had indeed been inside the keep-out zone around an active thruster. How much contamination he received could not be determined, and all of it (however much it had been) had evaporated safely before the men got back inside the station.
On February 15, NASA’s James Hartsfield confirmed the conclusions of the investigation: “The joint U.S. and Russian operations team determined that a crewmember was within a keep-out zone while the thrusters were still enabled during the spacewalk,” he emailed me. “Both teams agreed that for future spacewalks communication with the crew about such critical events needs to be clearer and an affirmation of understanding is necessary from the crew.”
“The joint operations teams will also update joint flight rules that discuss keep out zones,” he continued. “They will clearly define the safe locations where the crew may be located if thrusters need to be enabled and what thruster inhibits need to be in place when a specific task requires the crew to work in a keep out zone.”
This is a productive, forward-looking approach, and is the surest way out of the current exchange of complaints and recriminations. In addition, Russian and American space engineers need to return to the fundamental question of why the space station’s American gyroscopes are being overloaded only on spacewalks from the Russian airlock using Russian spacesuits. As the past few weeks have shown, the consequences of this still-unsolved problem include significant impacts on crew safety in orbit and on the strained atmosphere of the US-Russian space partnership back on Earth.