Image: Spacewalk operation
NASA
An artist's conception shows how two spacewalkers should be positioned at the international space station's service module to free a stuck antenna.
By NBC News space analyst
Special to MSNBC
updated 12/1/2006 8:09:47 PM ET 2006-12-02T01:09:47

If at first you don’t succeed in space, try, try again … with better tools. That proverb with a twist applies to the struggle to free up a jammed antenna on a cargo ship attached to the international space station.

Space station crew members tried unsuccessfully to yank the antenna loose during a spacewalk last month – the same spacewalk that featured Russian cosmonaut Mikhail Tyurin’s much-ballyhooed commercial golf shot. Although Tyurin didn’t need a second cut at the golf ball, he and NASA astronaut Michael Lopez-Alegria will have to take another swing at getting the antenna freed up, possibly in February. To make the job easier, a heavy-duty cutter is being added to the manifest for next week’s space shuttle mission.

The roots of the problem go back to October's automatic docking of the unmanned Progress cargo ship: At the last moment, one of the craft's hinged guidance antennas failed to retract as planned. Instead, it rammed into the back end of the station and lodged itself under a handrail. The mechanical linkup was still successful, and the supplies aboard the ship were later transferred into the station.

But Russian space controllers in Moscow were concerned that the jammed antenna might "hang up" on the station structure when it separates from the station in March to make room for a new manned spacecraft. Broken structural elements could create sharp edges that would threaten future spacewalkers working in the area. The worst-case scenarios include the departing vehicle being yanked into a tumble and recontacting the back end of the station or solar panels in the area.

Hence, they will have to try again, as reported in a NASA internal daily update issued on Monday: "After the spacewalkers' inability to break the mechanical contact of the Progress Kurs antenna on the SM [service module] handrail, another EVA [extravehicular activity] will be required to do the job prior to undocking.”

Extra time and extra tools?
There is plenty of time to develop and perform the contingency spacewalk, since the expected Soyuz launch on March 9 will probably be delayed a full month for other reasons. NASA spokesmen in Houston have provided no official confirmation of this, but Russian sources (and press accounts) have been discussing the delay for weeks.

The time-critical angle to these new plans was the possibility that NASA would need to add some new cutting tools to the shuttle Discovery's STS-116 mission, now slated for launch next Thursday. Such tools could cut right through the jammed struts rather than just poke and pull at them, as the spacewalkers tried fruitlessly to do during the first attempt. NASA even briefly considered adding the task to the spacewalks scheduled during this shuttle mission.

On Friday, NASA planners decided to install a 17-inch-long (43-centimeter-long), 6-pound (2.7-kilogram) general-purpose cutter on the floor of Discovery's middeck, for transport to the station on a "just-in-case" basis.

Image: Frozen antenna
NASA
A picture taken by the international space station's spacewalkers — and published here for the firtst time — shows the stuck antenna in detail, with the dish beneath the handrail on the right edge of the image.
The antenna in question folds out and forward, in order to get a clear view of a cooperative transponder (radar echoer) on the station. Structurally, it is a small dish mounted on one end of a flat tubular frame, with pairs of hinged arms attached at the front and back end of the cylinder and at corresponding hinge points on the side of the robot freighter’s nose. As it swings forward — and then back, just prior to contact — the antenna stays parallel to the line of approach.

The problem was noticed just as the Progress was making its "soft docking" on Oct. 26, when Mission Control picked up telemetry indicating that the antenna didn't swing back. Controllers gingerly completed the docking process — and decided afterward to have the spacewalkers take a closer look at the antenna during their planned Nov. 22 spacewalk. The crew was going to be in the area anyway, to move another antenna out of a position that was interfered with a protective cover over a rocket thruster.

Spacewalkers strike out
On the day of the spacewalk, the two spacewalkers started out with the much more photogenic "space golf" stunt, then moved around to the back end of the Russian-built Zvezda service module, out of sight of the exterior television cameras.

Without the helmet-mounted TV cameras used regularly on American spacesuits, no live images of the worksite or crew activity was possible. Instead, the spacewalkers took about three dozen photographs for downlinking later.

First using their hands, and then a prybar brought for that purpose, the men tried to swing the antenna structure away from where it had lodged. Moscow also sent commands for the motorized drive mechanism to retract — all to no avail.

“There is a big scratch on the surface,” Tyurin reported. “The internal gear must have been blocked – it cannot be folded, it does not move.” Russian specialists later told their NASA colleagues they suspected something was “frozen in the linkage for the antenna’s drive mechanism.”

Tyurin offered to “hammer it a bit,” but Mission Control disagreed, advising him “to let it live a little more.” It was clear by then that another attempt would have to be made later.

Sources told MSNBC.com privately that this second attempt, with much more serious tools, will be made early next year, possibly in late February. The schedule pressure comes from the need to separate the supply spacecraft safely to make room for a Soyuz craft carrying a replacement crew to the station.

Flight planners are still working out which spacesuits and air lock would be used for the spacewalk — the U.S. suits from the Quest air lock, or the Russian suits from the Pirs air lock. NASA planners would prefer that the U.S. suits be used, since adding a fourth spacewalk after the three already-scheduled U.S. outings would be more efficient. They say starting up the full preparations for a new Russian EVA would take two to three times as much crew time.

The Russians, however, are concerned about the barter obligations that using a U.S. suit for Russian requirements would entail.

Soyuz flight delayed
Fortunately, the crew should have some extra time to get this new task done. Last October, a Russian space official told journalists in Moscow that the planned March 9 launch of the new Soyuz would be put off.

“The idea is to sensibly time the crew’s landing in Kazakhstan,” said the official, who spoke to the Russians under conditions that ruled out direct attribution. “All spring landings of crews are now to be shifted from March to April,” since severe spring flooding in recent years has made recovery operations difficult. “Landing on a flooded steppe may be quite dangerous,” the official pointed out.

Furthermore, the official slip of a shuttle mission from Feb. 22 to March 16 also makes the original Soyuz launch date impossible. NASA spokesmen told MSNBC.com they had no information about any change in the Soyuz date, but multiple sources agree that it is now April 9 rather than March 9 — and that is good news for the station crew’s spacewalk sequel.

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