After nine years without a human launch from Florida, it's about damn time, isn't it.

During Wednesday's technically smooth countdown, NASA astronauts Doug Hurley and Bob Behnken came within 17 minutes of launching before a scrub due to poor weather.

The company's Falcon 9 rocket will lift Hurley and Behnken, aboard SpaceX's Crew Dragon capsule, into outer space, and the Crew Dragon will carry them to the International Space Station.

The big concern again today is the development of thunderstorms near the launch site this afternoon, which could violate a number of weather criteria, including not just precipitation, but also residual electric energy from lighting in the atmosphere.

Overall, the chance of acceptable weather at launch time is about 50 percent, forecasters estimate.

This is nothing new for NASA or US human spaceflight.

It has been such a long, long road for NASA and SpaceX to reach this moment—thousands of engineers and technicians have labored to design, develop, test, and fly hardware for the Dragon spacecraft and Falcon 9 rocket over the last decade.

But now the hardware and crew are ready, and at just the right time, to go fly.

Should Saturday's mission scrub, there will be another launch opportunity on Sunday at 3pm ET (19:00 UTC), potentially with marginally better weather.