STS-122 Shuttle Launch Decision on Tap

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NASA engineers continue to repair a faulty electrical connector on Space Shuttle Atlantis’ external fuel tank which has delayed the launch of the STS-122 mission to the International Space Station. An update of the progress on that work will be presented at a mission management team meeting scheduled for Thursday, January 3 and mission managers will perhaps then be prepared to announce a proposed launch date for Atlantis.

The repairs could take several days or even weeks. At a press briefing last week, shuttle program manager Wayne Hale declined to offer a probable launch date. “We’re in the middle of troubleshooting and repair,” he said. “Until that gets a little bit further along, I actually have no valid dates to give you. To avoid what I think would be a totally misleading headline along the lines of ‘NASA Delays the Space Shuttle Again,’ we’re just not going to give you a launch date because that, in fact, would not be accurate.”

The engine cutoff (ECO) fuel sensor system transmitted false readings during two launch countdowns for Atlantis earlier in December. A fueling test performed on December 18 isolated the problem to a 1 ½ -by 3 inch connector called a pass-through connector, located both inside and outside the tank. The wires for all four ECO sensors pass through the same connector. From the data of that test, engineers believe the problem lies in gaps between pins and sockets on the external side of the pass-through connector when the system is chilled to cryogenic temperatures, as when the tank is filled with liquid hydrogen and oxygen.

Engineers have removed the connector and are bench-testing the components in similar cryogenic conditions to try to duplicate the failure. Meanwhile, new hardware is being installed on the tank as the shuttle sits on launchpad 39A at the Kennedy Space Center.

“We have allowed the team that did the troubleshooting to very thoroughly go through all the data,” said Hale. “They have told us they are sure the problems that we’re seeing reside in that series of connectors. Where exactly in that series of connectors is a little bit open to interpretation.”

The connectors on the inside of the tank are being visually inspected. “It is a possibility that the internal connector is involved,” Hale said. “However, all the physics based discussion of the kinds of things that can happen point to something happening on the external connector.”

Problems with the internal connector would involve “more invasive” work, Hale said, that could possibly damage the tank.

A similar repair was done to the Atlas rockets several years ago to fix problems with circuitry in the Centaur stage. ECO sensors protect the shuttle’s main engines by triggering engine shut down if fuel runs unexpectedly low. The Space shuttle main engines running without fuel would likely result in an explosion.

The STS-112 mission will deliver the European Space Agency’s Columbus science module to the station along with a new crew member Leopold Eyharts from France who will take over for Dan Tani. Tani, whose mother was killed in a car accident on December 19, will return to Earth on Atlantis.

“These repairs and troubleshooting activities will determine when we will launch” said Hale. “The plan to go forward will take as long as it takes, but we don’t think this will be a long-term thing. Probably something that will take a couple of weeks.”

Day of Troubleshooting Leads to Clues for Shuttle and ISS

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Tuesday, December 18 was a day of major troubleshooting for NASA, as the space agency tries to hunt down the causes of problems plaguing both the shuttle and the International Space Station. While the day ended with few definitive answers, NASA officials said the data they gathered — and even what they didn’t find — will help them make strides towards solving the issues.

A tanking test on the shuttle’s external fuel tank helped narrow down a problem with the engine cutoff sensors to a “pass-through” connector in the system, but shuttle program manager Wayne Hale said the exact problem is not yet known.

“Exactly what we’ve got to do and where in this three-part connector we have to do it is a little bit of work ahead of us,” he said. “I’m just pleased as punch we know it’s in the connector and not some other place in the 100 feet or so of wiring and sensors and electronic boxes so we know what area to concentrate our efforts.”

But how much work the fix will entail, or how the repairs might affect the proposed January 10 launch date is also in question.

“I do not have any information about a launch date today,” Hale said. “Where the troubleshooting and replacement and repair work leads us will determine what the launch date’s going to be. We are not going to be driven by schedule on this one. We need to get to the bottom of this, fix it and make sure it’s fixed once and for all and then we can fly safely through the rest of the program, at least in this area.”

However, Hale said he felt the problems could be turned around in fairly short order.
He said the problem appears to be temperature related, or perhaps related to the tightly sealed, almost vacuum like conditions the connector operates in.

The 1 1/2-by-3 inch connector is called a pass-through connector because it is located both inside and outside the tank. The part that will be difficult to get to is the socket connector on the inside of the tank. Engineers would have to go inside the ET through a “man-hole cover” in the bottom of the tank, and that would entail a longer time to fix the problem.

Engineers are still troubleshooting some issues in bench tests away from the shuttle, and more data will be presented to program managers on Wednesday.

Meanwhile, two ISS astronauts conducted a seven hour spacewalk on Tuesday, inspecting problems with two unrelated mechanisms that allow the station’s solar wings to track the sun for power. It was the 100th EVA in support of station construction and maintenence.

Station commander Peggy Whitson and flight engineer Dan Tani first looked at a malfunctioning beta gimbal assembly that tilts the the starboard solar arrays to face the sun. Engineers thought that perhaps a micrometeoroid hit may have damaged the device, but the astronauts found no evidence of any impacts. The spacewalkers temporarily disconnected cables and a subsequent test found that the motor most likely is the problem. A new motor will be installed during the next shuttle mission.

The issues with the solar array rotary joint, a huge mechanism that also automatically rotates the solar arrays to face the sun, will require more work, contemplation and likely several spacewalks to fix. No “smoking gun” was found as to what is causing the joint to vibrate and display electrical spikes. In addition, metal shavings were found during an earlier inspection of the SARJ. Space station program manager Mike Suffredini said repairs probably won’t begin until next fall after a station crew can be trained to repair the joint. The shuttle crews “to-do” lists are already filled for the remaining shuttle flights in order to finish the construction of the ISS.

Mike Suffredini said the station team is “challenged” by the issues they are facing in the two repairs.

“The fact that it (the SARJ) looked as we expected is an enormous amount of information for us,” said Sufradini. “It would be really nice if something stood out and said ‘hey, I’m the cause of your problem,’ but we didn’t get that.”

Original News Source: NASA TV