Photos: Atlas 5 rocket aims for International Space Station

SpaceX’s Falcon 9 rocket ignited its nine Merlin main engines for several seconds Thursday at launch pad 39A in Florida, moving the previously-flown booster closer to a scheduled blastoff Monday with a Bulgarian communications satellite.

Successfully put through its countdown paces in a critical pre-flight test Thursday, America’s largest rocket currently in service moved closer to a June launch for the U.S. intelligence community.

A Chinese rocket measuring around 100 feet long that launched earlier this month will likely plunge back into Earth’s atmosphere some time Monday, becoming the most massive object in decades to fall out of orbit in an uncontrolled manner.