Fifth time the charm?

SpaceX will make its fifth attempt to launch an SES-9 satellite on its Falcon 9 rocket on Friday Mar 4 after high-level winds were too strong on Tuesday. The first two were scrubbed because of problems with the superchilled liquid oxygen (the oxidizer that is mixed with kerosene fuel in the rocket motor). Superchilled liquid oxygen was first used in December.

Liquid oxygen (LOX), just below the boiling point of -297.3 deg F at sea level, is about 900 times more than dense than oxygen at room temperature, but the LOX tank must be insulated, have a venting process, and, to put this heavy a satellite into geosynchronous transfer orbit with fuel left over to recover the first stage, be topped off just before launch. SpaceX is getting more LOX in the same tank by cooling it down to -340 degrees F which makes it about 10% more dense but trickier to keep cool. The first stage will try to land on a barge about 400 miles out in the Atlantic Ocean.

The satellite was built by Boeing for Luxembourg-based SES for use over east Asia and the Pacific for video, government and commercial communications.