STS-122 Shuttle Launch Decision on Tap

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.”