Video: Falcon 9 test-fired before fourth Starlink launch (members only)

A Falcon 9 booster that flew into space last year is set to launch again Thursday from Florida’s Space Coast with an SES communications satellite on a historic mission that could make major strides in validating SpaceX’s audacious goal of recovering and reusing launchers, an achievement the company says will revolutionize the rocket business. Liftoff is set for 6:27 p.m. EDT (2227 GMT).

Sierra Nevada and United Launch Alliance have announced the most powerful version of the Atlas 5 rocket, with five strap-on boosters and a twin-engine upper stage, will send the first two Dream Chaser cargo missions to the International Space Station from Cape Canaveral in 2020 and 2021, a schedule that still must be confirmed by NASA.

The U.S. Government Accountability Office has denied a protest filed by Sierra Nevada Corp. challenging NASA’s selection of competitors Boeing and SpaceX to build commercial human-rated space capsules to fly astronauts to the International Space Station.