SpaceX’s Crew Dragon spacecraft will take off from Kennedy Space Center’s launch pad 39A riding atop a Falcon 9 rocket.

39A has a rich spaceflight history: It was the starting point for 11 different Apollo missions, including the first-ever moon landing in 1969. It was later used for the majority of NASA’s Space Shuttle launches.

SpaceX signed a contract with NASA in 2014 to lease the pad for the next 20 years.

What’s happening: SpaceX will make its second attempt to launch two NASA astronauts on a mission to the International Space Station.

Why it’s important: If successful, it would be the first crewed spaceflight to take off from US soil in nearly a decade.

  • This will be the first time that astronauts launched into space from US soil since 2011.
  • It will be the first-ever crewed mission for SpaceX.
  • It will also be the first time ever that a privately developed spacecraft launched humans into Earth’s orbit.

Round 2: Bad weather on Wednesday scrubbed SpaceX and NASA’s first attempt.

Go/No-go: The mission is slated to try again today at 3:22 pm ET.


Why launch from Florida?

It’s hurricane season in the Sunshine State.

And the fact that a full day of launch preparations was already dashed by inclement weather earlier this week, has a lot of people wondering: Why do NASA and SpaceX launch rockets from a place with such notoriously fickle forecasts?

There’s a few reasons:

  • The ocean: It’s dangerous to launch rockets over populated areas. If something were to go awry, pieces of debris could be damaging or deadly on the ground. So the rockets take off from Florida’s coast and fly out over the Atlantic ocean.
  • The equator: The Earth actually spins fastestat the equator. So, when launching a rocket from North America, it’s best to go as far south as possible. That way, rockets get more of a speed boost by launching with the direction of the planet’s spin. The extra boost is small — but saving any little bit on fuel costs and weight can be a big win in rocketry.
  • Empty land: Kennedy Space Center was built in Brevard County, Florida, in the mid-20th Century because there happened to be a patch of empty land and a nearby military base.

Still, Florida’s weather has long made it difficult to predict exactly when a space mission will actually take off.

About one third of launches since 1988 have been delayed as a result of bad weather, according to the 45th Weather Squadron.

But the astronauts know this is part of the drill.