Photos: Atlas 5 rolls out for launch

Bound for an orbital rendezvous with the International Space Station on Wednesday, a commercial Cygnus freighter was successfully launched by an Atlas 5 rocket Sunday to restart American cargo deliveries to the research outpost.

NASA has agreed to consider a Boeing proposal to extend the first piloted test flight of its commercial CST-100 Starliner crew capsule from two weeks to up to six months with an extra crew member for the International Space Station, hedging against potential delays that could jeopardize U.S. crew access to the orbiting outpost.

A troublesome liquid oxygen valve on the Space Launch System’s first flight-rated core stage will keep NASA from performing a second test-firing of the rocket’s four main engines this week.