Photos: America’s 100th EELV blasts off

Sierra Nevada Corp. has booked at least six launches on United Launch Alliance’s new Vulcan Centaur rocket to carry Dream Chaser supply ships into orbit on cargo runs to the International Space Station beginning in 2021, becoming the first confirmed customer for ULA’s next-generation launcher.

Space station astronauts closed hatches to the SpaceX Crew Dragon spacecraft Thursday, setting the stage for undocking early Friday and a fiery unpiloted plunge to splashdown off the coast of Florida. A successful return to Earth will help clear the way for launch of the first piloted test flight of the new ferry ship in the mid-summer timeframe.

Ground teams are buying more time to study two sluggish valves inside the Juno spacecraft’s fuel pressurization system and postponing a major engine burn that was scheduled for next week to reshape the probe’s orbit around Jupiter, officials said Friday.