SpaceX launch abort
Engines sputter and die just as the Falcon 9 rocket is about to take offSpaceX

Elon Musk's SpaceX aborted its third try in five days at a rocket launch, a heartbeat before lift-off, because of a problem with liquid oxygen. The engines began to fire, then sputtered and died.

The mission at Cape Canaveral Air Force Station in Florida on 28 February was a no-go after the rocket's internal computer pulled the plug just as the countdown reached zero because the liquid oxygen wasn't cold enough, Musk explained later in a tweet.

The oxygen apparently warmed too much after an earlier planned launch was delayed as officials waited for a ship to clear the area, reported the Orlando Sentinel. The wait caused liquid oxygen loaded into the rocket's propellant tanks to heat up, and a "helium bubble triggered alarm," Musk said.

The scrub was "out of an abundance of caution," but the Falcon 9 rocket "remains healthy," said a statement from the commercial space company. The mission's first two launch attempts were scrubbed after SpaceX said it was having trouble keeping the rocket's liquid oxygen supply chilled to near its freezing point.

SpaceX began using a new kind of fuel with its upgraded Falcon 9 rockets in December 2015. The rockets now run on deep cryo liquid oxygen. The fuel is denser than other rocket propellants, so more can be packed into rocket fuel tanks — which adds to the power — but the trade-off is that it must be chilled at -340 degrees Fahrenheit (-206 C).

The liquid oxygen appeared to be behaving in the most recent attempt until the boat delayed the lift-off.

The rocket will carry a satellite for Luxembourg-based SES into orbit that will help telecommunications and broadcasts in Asia. SES has more than 50 satellites already in orbit.

SpaceX will also attempt to land the rocket after it delivers its payload on an ocean barge for the first time, a move some say will help the company as it progresses toward a mission to Mars. A tweet from the Air Force's 45th Space Wing indicated that the next launch date wouldn't likely be until the first of March or later.