A delayed SpaceX launch is happening tonight. Here's what you need to know

A SpaceX Crew Dragon capsule will take flight this week, carrying four astronauts to the International Space Station, where they'll spend six months living and working in space. It will be the fourth time SpaceX has sent astronauts to the space station.

The Crew Dragon spacecraft is slated to take off atop a Falcon 9 rocket from NASA's Kennedy Space Center at precisely 9:03 pm ET Wednesday — a time chosen because it's the optimal moment to get the spacecraft on track to link up with the ISS. The astronauts will spend a full day onboard the spacecraft after it reaches orbit and begins slowly maneuvering toward the ISS, with which it's scheduled to dock at 7:10 pm Thursday.

SpaceX had intended to launch this mission, called Crew-3, on Halloween, but liftoff was delayed because of some rough weather over the Atlantic Ocean that could've impacted rescue operations if the rocket were to misfire and force the astronauts to make an emergency splashdown landing in the ocean. Crew Dragon's ability to jettison a crew to safety if something goes wrong is one of the reasons the space agency says it is among the safest spacecraft ever flown. Such an emergency exit has never had to be carried out by SpaceX, but having that option — and ensuring a recovery could be smoothly executed — is one of the reasons the space agency says Crew Dragon is among the safest spacecraft ever flown.