Here's how a boat wrecked SpaceX's chances for a historic rocket launch

Sunday evening was scheduled to be SpaceX's third attempt at its second launch of the year. However, a series of unexpected set backs, which began with a boat, ultimately led to an abort for the evening.

It was definitely a close call. The countdown clock actually reached T-00:00:00 and the rocket looked like it was about to lift off at 7:21 p.m. ET, when all of the sudden the computer in control of the rocket shut the engines down.

Here's what the abort at the very last second looked like — you can actually see the engines begin to fire:

Despite Sunday evening's scrub, SpaceX reported that its Falcon 9 rocket is still healthy.

Why the launch was aborted

The problem began around 6:45 p.m. ET when when a boat strayed too close into the danger zone. The launch was temporarily held to give the boater time to vacate, and SpaceX was still expecting lift off, albeit a little later than scheduled.

However, in the 40-or-so minutes between waiting for the boat to move and restarting the countdown sequence, something had happened to the rocket's fuel, according to SpaceX founder and CEO, Elon Musk:

SpaceX began using a new kind of fuel with its upgraded Falcon 9 rockets last December. The rockets now run on deep cryo liquid oxygen (LOX).

This fuel has the benefit of being more dense than other rocket propellants, so you can pack more of it into rocket fuel tanks — which adds to its power — but the trade-off is that you have to chill it at -340 degrees Fahrenheit.

However, the launch team didn't know that the fuel had warmed by the time the rocket was go for launch. That's why the countdown clock reached T-00:00:00.

It was the rocket's internal computer that kicked in and aborted the launch seconds before lift off. 

The rocket's internal computer takes control of the launch sequence with one minute to go before every SpaceX launch. During that time, it analyzes the fuel, the engines, and other aspects of the rocket to make sure everything is functioning properly. This is standard safety procedure.

SpaceX has yet to establish another launch date to try again.

A historic rocket launch

Sunday's launch could have been SpaceX's chance to make history. The launch itself isn't necessarily historic, but the rocket landing scheduled after lift off could have been.

Since its first attempt in January 2015, SpaceX has been trying to land the first stage of its Falcon 9 rockets on a floating ocean platform. So far, none of the landings have been what you could call a perfect success.

Sunday's attempt would have been SpaceX's fourth attempt.

NOW WATCH: Epic footage of SpaceX’s gutsy rocket landings

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