To date, though, SpaceX has launched only things like satellites and cargo (and one Tesla sports car), not astronauts.

On Saturday, SpaceX is aiming to get one step closer to its goal with a demonstration flight of a crew-capable capsule even though there will not people on this particular flight.

When is the launch and how can I watch it?

If you’re in the United States, you’ll have to stay up late or wake up very early. The launch is scheduled for 2:49 a.m. ET Saturday. NASA Television will be broadcasting coverage on the web and on YouTube at 2 a.m.

What are SpaceX and NASA trying to accomplish with this launch?

This is an end-to-end test of the spacecraft, known as Demo-1, from launch to docking at the International Space Station to splashdown in the Atlantic Ocean. The idea is to uncover problems (and fix them) before putting astronauts aboard.

If the mission gets off the ground Saturday morning, it’ll get to the space station Sunday. It would leave on March 8, parachuting into the ocean after it re-enters Earth’s atmosphere.

Is there anything on board the Crew Dragon?

The capsule can seat up to seven astronauts. For this flight, one of the seats will be occupied with a sort of artificial person — what NASA calls an ATD or “anthropomorphic test device” — which will be wearing a SpaceX spacesuit. The device includes sensors to measure forces and accelerations that a person would experience on the trip.

The SpaceX engineers named it Ripley, after the heroine in the “Alien” movies played by Sigourney Weaver.

It will also carry 400 pounds of cargo like any other journey to the space station, as well as inserts that simulate the mass of a more completely filled capsule. Engineers on the ground will use information from the flight to understand how the spacecraft responds to being loaded.

Who else is building a capsule for crew to get to the space station?

NASA awarded contracts to SpaceX and Boeing in 2014 to develop spacecraft for taking astronauts to orbit. The crewless test of Boeing’s capsule, named Starliner, could occur next month.

Why does NASA need these privately built capsules?

Since the retirement of the space shuttles in 2011, the only way for NASA astronauts to get to space has been to pay for trips aboard Russian Soyuz spacecraft.

NASA had been developing its own rocket, the Ares I, but that was much more expensive, and the Obama administration canceled the program. NASA had already started using commercial companies to take cargo to the space station, and the thinking was that commercial companies could provide cheaper rides for astronauts as well.

NASA is still developing a larger rocket, the Space Launch System, and capsule, Orion, for deep space missions. And NASA astronauts will continue to fly on Soyuz, and their Russian counterparts will fly on the Crew Dragon and Starliner; the idea is to make sure everyone is familiar with the workings of all the various spacecraft.

When will the Crew Dragon carry people to space?

Both SpaceX and Boeing are aiming to launch their first crewed missions this year, but if there are any additional delays, the flights could slip to next year. NASA is considering buying more Russian Soyuz seats.