From "The Flame Trench" at Floridatoday.com:

Tuesday, March 17, 2009 Live At The Cape: Atlas Delay At Least 48 Hours

LIVE IMAGES: Refresh this page for updates and the latest still images from the Air Force 45th Space Wing Weather Channel (left) and Launch Complex 41 (right).

Launch of an Atlas V rocket and a new-generation military communications satellite is being delayed until at least Friday to give engineers time to investigate the failure of an upper stage engine valve.

The 19-story rocket and its payload -- a Wideband Global SATCOM spacecraft -- had been slated to blast off from Launch Complex 41 at Cape Canaveral Air Force Station at 9:24 p.m.

But a valve in the rocket's single Centaur upper stage engine sprang a leak about 20 minutes into fuel-loading operations. The leak was serious enough to prompt mission managers to immediately call a scrub.

Engineers estimate that it will take most of the night to drain propellant from the Centaur stage and then inert it to make certain no explosive gases remain within it.

The course of action likely will be to remove a box within the engine that holds the valve and try to determine what caused the leak. The timing of the next launch attempt will be dependent on how long it takes to execute a recovery plan.

Engineers also will be sorting out a couple of other problems with gaseous nitrogen and gaseous helium systems. Range safety officers also will need to resolve trouble with one of two instruments required to make certain command destruct signals are properly encoded. The destruct signals would be beamed up to the rocket if it careened out of control and threatened populated areas.

73, Drew