Live coverage: Atlas 5 countdown and launch journal

United Launch Alliance has completed stacking of the major elements of the Atlas 5 rocket assigned to power NASA’s Perseverance rover toward Mars, but the mission’s launch date has been pushed back three days to July 20 after teams repaired an issue with a crane in the Atlas 5’s assembly building.

Investigators probing the Sept. 1 explosion of a SpaceX Falcon 9 rocket on its launch pad in Florida believe a high-pressure gas tank inside the launcher’s upper stage most likely burst due to the conditions of the helium loaded into it, a finding that could simplify fixes needed before the commercial booster can return to service.

NASA’s acting administrator said Tuesday he does not expect Russian cosmonauts to start launching to the International Space Station on U.S. commercial crew vehicles until next year. A proposed agreement with Russia to ensure the space station is always staffed with an international crew is awaiting U.S. government approval.