Original URL: http://www.theregister.co.uk/2007/12/28/shuttle_launch_delayed/

Space shuttle launch knocked back again

Pesky fuel sensor woes continue

By Lester Haines

Posted in Science, 28th December 2007 10:54 GMT

Pesky fuel sensors have forced NASA to put back the launch of space shuttle Atlantis beyond the current target date of 10 January, Reuters reports.

The offending sensors - which monitor liquid hydrogen levels in the vessel's fuel tank - have twice caused cancelled lift-offs. Of the first incident in early December, NASA explained: "On Thursday morning, two of the four engine cutoff, or ECO, sensors inside the liquid hydrogen section of the tank failed a routine prelaunch check. Following the launch postponement, the tank's liquid oxygen and liquid hydrogen were drained.

"While the tank was being emptied, engineers monitored and collected data on the liquid hydrogen sensors that failed. During that process, another sensor gave a false reading, indicating that the tank was 'wet', when it was dry."

NASA subsequently proposed splicing jumper cables into "about 100 feet of wiring that runs between fuel sensors in the shuttle's tank and the ship's engine compartment", and reckons it's now identified the problem - a "two-sided, plug-like connector" which relays electrical signals from the sensors.

NASA will remove the suspect part on Saturday and send it off for testing at the Marshall Space Flight Center in Huntsville, Alabama. Engineers, meanwhile have suggested that if the fault can't be traced, they can simply dispense with the connector altogether and solder the wires in place.

The upshot of the latest episode in the sensor saga is that the launch of Atlantis will be put back by "a few days to a few weeks", according to programme manager Wayne Hale. He told reporters: "We need to get the problem resolved. Then we'll look at schedules." ®