NASA is still hoping to launch the Space Shuttle Endeavour in early February as engineers scramble to repair broken hoses on the new space station module set to ride aboard the orbiter.

Endeavour is slated to launch the new Tranquility module to the international space station Feb. 7 from the Kennedy Space Center at Cape Canaveral, Fla. But two of the module’s four ammonia coolant hoses have failed standard prelaunch checks, prompting engineers to come up with a repair plan while others try to build new hoses from scratch, station managers said Jan. 11.

“Folks are working really hard to get the hoses checked out, completed, certified [and] tested,” said Pete Hasbrook, NASA manager for the Expedition 22 mission to the space station. “We are still working toward the Feb. 7 launch date.”

The new Tranquility module, like other space station rooms, uses liquid ammonia to keep its computers and other electronic equipment cool in space. The coolant hoses are routed on the exterior of the space station and must function at a pressure of 3,000 pounds per square inch to keep the ammonia supply liquid and moving, Hasbrook said.

But two of Tranquility’s coolant hoses failed at a pressure of only about 1,500 pounds per square inch, apparently due to a defect in their exterior braided-metal sheath covering, Hasbrook said. The metal braids began separating from the hose connector during the test, he added.

The test was performed in Florida, where Endeavour is waiting atop its seaside launch pad for the delivery of Tranquility, a seven-window observatory port called the Cupola, and other supplies to the station.

Tranquility initially was slated to be attached to an Earth-facing berth on the station’s main Unity connecting node, but the misalignment of ammonia coolant lines on that node led managers to move the new module to an open berth on Unity’s port — or left — side. To attach Tranquility there, engineers built four so-called jumper lines to route liquid ammonia from Unity to the new module. The hoses are custom-made and are 4.2 meters long — longer than typical station hoses.

Hasbrook said station engineers have successfully tested a “beefed up” version of the coolant hoses using an extra layer of braided metal in Florida, though the final approval of the repair is still under review. Meanwhile, another team at NASA’s Marshall Space Flight Center in Huntsville, Ala., is working to modify spare station hoses to replace the damaged ones in case the repairs do not pass muster, he added.

Still another option is to launch Endeavour and the Tranquility module as planned, but to delay Tranquility’s full activation until March or later, when new hoses could be launched on a different shuttle flight, Hasbrook said. That option would require spacewalking astronauts to install extra heaters on Tranquility that would allow astronauts to install the module and power up some systems temporarily. The module would feel more like a dark, cool cellar until the new hoses arrive later and allow for the full activation, Hasbrook said. “That’s about a Plan C,” he added. “The other two options are looking pretty good.”