Snapshots from Atlas 5 launch

Giving every opportunity for the storm clouds to blow clear after a four-hour hold, the United Launch Alliance Delta 4-Heavy rocket counts down Thursday afternoon at Cape Canaveral until the clocks had to be halted for the day.

A year after a launch mishap left Orbital ATK’s Cygnus supply ship without a ride to the International Space Station, company officials say the cargo delivery system is on the verge of a comeback, thanks to deals with United Launch Alliance and a decision to redesign its Antares booster with new rocket engines.

SpaceX’s proposal to land astronauts on the moon using the company’s reusable Starship vehicle could be “game-changing” for space exploration, but comes with risks and complexity that “threaten the schedule viability” to achieve NASA’s goal of returning crews moon by the end of 2024, agency officials said.