Time-lapse: Falcon 9 lifted vertical on pad 39A (members only)

Holding up a photo taken by China’s new Mars lander, NASA Administrator Bill Nelson warned Congress Wednesday that his agency faces increasingly stiff competition on the high frontier and that sustained funding for a new moon lander, infrastructure upgrades and other critical programs is vital for America’s space program.

Two Russian cosmonauts floated outside the International Space Station Thursday for a planned six-hour spacewalk to manually launch five small satellites, to test a variety of spacesuit upgrades, to retrieve an external experiment and to carry out routine inspections and maintenance.

Mission managers are weighing a motley mix of weather models, safety criteria and astronaut workload considerations as they decide when SpaceX’s Crew Dragon spacecraft might have the best chance to launch from the Kennedy Space Center.