UPDATE: CEO Elon Musk said upper level winds caused Tuesday’s scrub.

Pushing launch to Friday due to extreme high altitude wind shear. Hits like a sledgehammer when going up supersonic pic.twitter.com/Gr8T5upaLd

— Elon Musk (@elonmusk) March 1, 2016

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SpaceX scrubbed three attempts last week.

Fuel used in the Falcon 9 rocket is causing the delays. SpaceX started using chilled liquid oxygen. By cooling the fuel to a very low temperature, SpaceX can load more into the rocket and increase the Falcon 9’s efficiency.

But during the last launch attempt, a boat drifted into the launch zone putting the countdown on hold. While SpaceX waited for the boat to clear, the fuel warmed up a bit too much, and that forced technicians to scrub the launch.

The so-called super-chilled liquid oxygen was used successfully only once before in a launch from California earlier this year. SpaceX CEO Elon Musk says this technology – along with landing and reusing the spent booster – will lower the cost of launching rockets into space.

If successful, this will be the private space company’s first launch from Florida this year. The launch window opens at 6:35 PM EST.

SpaceX will try and land the lower portion of the rocket on a barge at sea.