The flights typically take about 24 hours. Shortly after reaching space, Crew Dragon lifts open a top lid, resembling the tip of an eggshell, to expose its docking adapter. The spacecraft approaches the space station in a headfirst position and autonomously docks to one of the station’s entry ports.

SpaceX developed the astronaut taxi with roughly $3 billion from a NASA program called Commercial Crew. The goal of the program was that private companies would own the spacecraft they build, with NASA being just one customer among many buying seats for astronauts. The agency’s previous mode of transportation to the space station was the space shuttle. But the shuttle program was retired in 2011, requiring NASA to buy expensive seats for its astronauts on Russia’s Soyuz rocket for nearly a decade as SpaceX and Boeing, the other company working under Commercial Crew, developed their capsules.

SpaceX’s first mission sending humans to space — a revival of NASA’s ability to loft humans to space from American soil — was in May 2020, with two NASA astronauts, Bob Behnken and Doug Hurley, riding Crew Dragon to the space station for a roughly two-month stay. The company has since launched two successful crewed missions for NASA with a combination of American astronauts and crews from Japan and the European Space Agency.

Boeing, the aerospace giant and plane maker, is far behind SpaceX. Development of its Starliner capsule has been marred by a range of technical issues, and it is at least a year away from flying its first crew of astronauts.

Faced with a threat to the zone, the agency worked with Russia’s space agency in Moscow to fire station thrusters that raised its altitude by just under a mile.

“It just makes sense to go ahead and do this burn and put this behind us so we can ensure the safety of the crew,” Joel Montalbano, NASA’s space station manager, told reporters during a news conference on Tuesday.

The debris is a remnant of China’s Fengyun-1C, a weather satellite that launched in 1999 and was decommissioned in 2002 but remained in orbit. In 2007, China targeted the defunct satellite with a ballistic missile on the ground, blowing the satellite to smithereens and creating over 3,000 pieces of debris. The missile test drew condemnation from the United States and other countries at the time.

The wreckage from the satellite was expected to make its close pass of the space station this coming Thursday night, according to Jonathan McDowell, a Harvard astronomer who tracks objects in space. But now that the station has moved, the threat of a collision is minuscule.

A large portion of that debris cloud is expected to stay in orbit for decades, threatening the space station and other spacecraft.

The station has carried out 29 such avoidance maneuvers since 1999, a year after its construction began. In some instances, astronauts had to board their spacecraft and brace for an emergency departure in case the station was hit and sustained damage.

Only the United States, Russia, China and India have launched antisatellite tests. The most recent occurred in 2019, when India blew up a defunct satellite, an effort to signal its capability for projecting military force in space.

The SpaceX mission that carried four astronauts for NASA, Japan and France to the space station in April had a space debris scare. SpaceX mission control alerted the astronauts that a piece of space debris was projected to whiz by the capsule, although nothing came close, and the crew safely reached the space station on April 24.

Days later, U.S. Space Command determined that the alert was the result of a “reporting error” and “that there was never a collision threat because there was no object at risk of colliding with the capsule.” Still, the incident renewed discussion about the growing threat of space debris and other clutter in low-Earth orbit.

Weather around NASA’s Kennedy Space Center in Florida, where Falcon 9 will launch from, is expected to be favorable for an on-time liftoff, with only a 30 percent chance of bad weather that could cause a delay, according to Space Force weather officers.

But “it’s not just what happens at the launchpad,” said Will Ulrich, a launch weather officer at the Space Force’s 45th Space Wing in Cape Canaveral, Fla.

Officials also monitor weather conditions along the path Falcon 9 takes to get to space, a trajectory called the ascent corridor that runs north along the East Coast. If Crew Dragon needs to trigger its emergency abort system to save the astronauts from a problem with the rocket once it launches, the capsule would need to land under good weather conditions anywhere along that corridor.

“Those conditions, unfortunately, are a little less favorable,” Mr. Ulrich predicted. “That ascent corridor is something my partners are going to be monitoring.”

If weather conditions along the ascent path worsen, the Crew-3 launch would be pushed to Thursday or Friday night.

Matthias Maurer, Crew-3’s mission specialist, is a German astronaut representing the European Space Agency. Mr. Maurer, 51, joined the European astronaut corps in 2015 after roles as a paramedic, a materials scientist and an engineer. In 2016, he spent 16 days with a group of other astronauts and scientists aboard Aquarius, a research and training habitat for future space missions that sits 62 feet below the ocean’s surface near the Florida Keys.

Formally designated as Crew-3’s first mission specialist, Mr. Maurer will officially be the 600th person to ever reach space.

Kayla Barron, 34, also joined NASA’s astronaut corps in 2017. She graduated from the U.S. Naval Academy with a bachelor’s degree in systems engineering in 2010, and a year later received her master’s degree in nuclear engineering from the University of Cambridge. She was among the first group of women to serve on a Navy submarine and was an officer aboard a ballistic missile submarine across three patrols.

Also a mission specialist, she will be the 601st human to reach space.

Ms. Barron and Mr. Chari are also members of NASA’s Artemis astronaut corps — a cadre of 18 astronauts who are eligible to travel to or around the moon as part of the agency’s multibillion-dollar program to build a lunar base and test out technologies for future missions to Mars.

Crew-3’s fourth astronaut is Tom Marshburn, 61, who will set off on his third trek to orbit since joining NASA’s astronaut corps in 2004. Mr. Marshburn has flown on two space vehicles in the past, serving as a crew member aboard NASA’s Space Shuttle Endeavour in 2009 and on Russia’s Soyuz spacecraft in 2013.