SpaceX plans to rocket a sleek new spaceship for NASA astronauts into orbit on Saturday. Here's what Crew Dragon must do to prove it's safe to fly people.

SpaceX has been working for years with NASA toward the first launch of Crew Dragon.

Following series of thorough tests — including blasts of sound to simulate the vibration of launch, and exposure in a vacuum chamber — Crew Dragon was shipped to Florida late last year.

There it was then integrated, or attached, to SpaceX's partly reusable Falcon 9 rocket.

The spacecraft will be flown into orbit by the latest and arguably safest version of the Falcon 9, a model called "Block 5."

SpaceX has wheeled the entire launch system out to a site called Launch Complex 39A.

No astronauts will fly in this demo — the spaceship is designed to be autonomous. But Crew Dragon will hold a spacesuit-clad dummy, or articulated mannequin. The plan is for a crew to fly the vehicle in the coming months.

The test flight is part of a larger effort called the Commercial Crew Program, or CCP, which aims to find a way to fly NASA astronauts to and from the space station. NASA lost that capability in July 2011, after it retired its space shuttle system. Astronauts currently fly in Russian Soyuz spacecraft.

In 2014, after developing and launching uncrewed cargo spaceships for NASA, SpaceX was awarded a $2.6 billion contract to develop and certify its Crew Dragon space capsule, then launch at least two (but up to six) operational missions to the space station.

Musk's company has worked closely with NASA astronauts to refine the controls and functionality of Crew Dragon before it was finalized.

Boeing also won a $4.2 billion CCP contract for its CST-100 Starliner spaceship. After each company performs an uncrewed mission to the space station, and a series of abort tests, NASA will let eight of its astronauts and one retired astronaut (now a Boeing employee) fly them into space.

SpaceX is launching its vehicle first. The Demo-1 mission is scheduled to launch at 2:49 a.m. ET on Saturday from Cape Canaveral, Florida, though there's a 20% chance of a weather delay.

On the launch pad, SpaceX briefly test-fired the Falcon 9 rocket's engines to ensure the system was working correctly.

The Block 5 version of SpaceX's Falcon 9 rocket was redesigned to improve the reuse of its expensive 16-story booster. The improvement also aimed to correct a problem that arose with a previous version of the rocket, which exploded during a launch pad fueling test on September 1, 2016.

The Crew Dragon will be loaded up with about 400 pounds of cargo, including a dummy crewmember.

The dummy will be packed with sensors to gather data for SpaceX and NASA. It will help determine if Crew Dragon's automated life support systems function as designed.

The last dummy SpaceX flew into space was a mannequin in a spacesuit called "Starman," which the company launched in a Tesla Roadster out to Mars orbit.

If the weather cooperates and there are no glitches, the rocket should lift off promptly at 2:49 a.m. ET under the cover of darkness.

In just over 1 minute, the rocket will accelerate faster than the speed of sound.

About 80 seconds into the launch, Crew Dragon and its rocket will enter a phase called "maximum dynamic pressure" or "Max Q." That's when there is the most stress on the rocket due to its high speed and the relative thickness of Earth's atmosphere.

Approximately 2 minutes and 30 seconds into flight, the Falcon 9's booster or first stage — the biggest section of the rocket — will separate from the upper stage, which will continue flying Crew Dragon to space.

The booster will then turn around, re-light its rocket engines, and slow down. This will cause it to fall back to Earth. A little more than 8 minutes after launch, it will try to land on a robotic ship in the Atlantic Ocean.

Landing the booster is not critical to the mission, but if all goes smoothly, it will get towed back to land for use in a future launch, saving SpaceX millions of dollars in rocket hardware.

Around the same time as the booster landing, the upper stage will help send the Crew Dragon into orbit, then detach from the spaceship.

On Sunday morning, Crew Dragon will catch up to the football-field-size International Space Station.

In SpaceX's previous launches of its uncrewed Cargo Dragon (or Dragon V1), the spaceships have been captured by a robotic arm on the space station.

But this time, Crew Dragon has to prove it can safely dock with the roughly $150 billion orbiting laboratory.

A crew of three crew members is already aboard the space station: NASA astronaut Anne McClain, Roscosmos cosmonaut Oleg Kononenko, and Canadian astronaut David Saint-Jacques. They will welcome the cargo and dummy if all goes according to plan.

Around 2 a.m. ET on March 8, Crew Dragon and its dummy passenger, along with what NASA says are "critical research samples" loaded up by the space station crew, will depart from the ISS.

Then Crew Dragon will scream through Earth's atmosphere at dozens of times the speed of sound, then slow down using its ablative heat shield. Finally, it will deploy three landing parachutes.

If that all happens according to plan, the space capsule will splash down in the Atlantic Ocean near Cape Canaveral around 7:30 a.m ET on March 8.

A boat will then recover the spaceship, its cargo, and the dummy passenger, and return them to land for SpaceX and NASA to scrutinize.

If the Demo-1 mission is successful, SpaceX will then have one more uncrewed flight-abort test to complete before turning its attention to flying astronauts.

As soon as July of this year, SpaceX may launch Demo-2: The company's first-ever crewed mission.

"Human space flight is basically the core mission of SpaceX," Hans Koenigsmann, SpaceX's vice president for build and flight reliability, said on February 22. "There is nothing more important for us than this endeavor."