The flight is an "historic milestone on the road to full and rapid reusability."

This evening, nearly a full year after it first launched a payload into orbit, a Falcon 9 booster will attempt a second launch. Some might call this a "used" or "reused" rocket, but in a wonderful marketing euphemism, SpaceX has characterized the booster as "flight proven." One day, clearly, rocket manufacturers like SpaceX and Blue Origin hope to convince satellite operators that used rockets are, in fact, more reliable than new ones.

But first SpaceX has to prove it can actually reuse a first-stage booster. That may happen as soon as today, with the SES-10 mission to deliver a communications satellite to geostationary transfer orbit. The launch window opens 6:27pm ET (11:27pm UK) today, and extends for two and a half hours. After launch SpaceX will attempt to land the booster on a drone ship in the Atlantic Ocean. Should weather (which appears good) or a technical issue force a delay today, a backup launch window opens on Saturday, at 6:27pm.

SpaceX has been circumspect about the extent to which this Falcon 9 first stage had to be refurbished for the reuse flight. In earlier remarks, SpaceX president Gwynne Shotwell has said it took about four months to test and prepare for the second flight. The company has not disclosed how much it spent refurbishing the rocket, but SES is believed to have paid about 30 percent less than a typical launch.

In a press kit for today's launch attempt, SpaceX described the flight as a "historic milestone on the road to full and rapid reusability." Last year Blue Origin achieved a vertical takeoff and landing of a suborbital rocket, but now SpaceX has a chance to repeat that feat with the more muscular, orbital Falcon 9 rocket. It is, indeed, a historic flight.

https://youtu.be/xsZSXav4wI8

The webcast tonight should begin about 20 minutes before the launch window opens, and we wouldn't miss it for anything.

This is going to be very interesting.