SpaceX has swapped out a faulty check valve on a Merlin engine on the Falcon 9 rocket and approved plans for a second launch attempt at 3:44 a.m. EDT (0744 GMT) Tuesday. You can follow the entire flight on Spaceflight Now with live video and comprehensive coverage. Computers aborted the countdown a half-second before launch Saturday due to high pressure in one of the Falcon 9 rocket's nine first stage engines. Engineers opted to replace a check valve in the first stage's center engine - engine No. 5 - after inspections. "The failed valve was replaced on Saturday and after...