Starliner launch scrubbed by trouble with a valve in the Atlas 5’s Centaur upper stage

In a blog post early Tuesday, NASA said launch of Boeing’s Starliner astronaut ferry ship will be delayed until at least Friday “to complete data analysis on a pressure regulation valve on the liquid oxygen tank of the Atlas 54 rocket‘s Centaur upper stage and determine whether it is necessary to replace the valve.” If the analysis concludes it’s safe to launch the Atlas 5 as is, NASA, Boeing and Atlas 5-builder United Launch Alliance could recycle for a second attempt at 9 p.m. EDT Friday. If the valve has to be replaced, the rocket would have to be hauled back to ULA’s Vertical Integration Facility for repairs, delaying another launch attempt to Sunday or later next week. More

(Source: SpaceFlight Now - May 7)