SpaceX Docking: Highlights From Astronauts’ Arrival at the Space Station

Astronauts board space station, completing historic trip to orbit.

The Crew Dragon has arrived.

A SpaceX capsule carrying two NASA astronauts docked at the International Space Station on Sunday morning, less than a day after a historic launch that marked the first time humans had ever traveled to orbit in a spacecraft built and operated by a private company.

The approach of the Crew Dragon proceeded smoothly, about 15 minutes ahead of schedule, with a camera on the space station capturing the red, green and white lights of the capsule as it steadily crept up over the course of a couple of hours. The astronauts, Robert L. Behnken and Douglas G. Hurley, took over manual control for a while, firing the thrusters to nudge the position of the spacecraft, before turning control back to a computer for the final steps leading to docking.

Once the docking was completed, Mr. Hurley congratulated staff at SpaceX and NASA and said “It’s been a real honor to be just a small part of this nine-year endeavor since the last time a United States spaceship has docked with the International Space Station.”

The docking indicated that the first portion of the test flight with crew aboard was successful. The trip will be considered a complete success once the astronauts return to Earth in the near future, opening the way for more travel to the space station and orbit by astronauts and perhaps space tourists in the years to come.

The astronauts’ 19-hour trip began on Saturday with a launch from Kennedy Space Center in Florida. It was the first trip to orbit from American soil by astronauts since NASA retired its space shuttles in 2011. The capsule blasted off atop a Falcon 9 rocket, also built by SpaceX, the company founded by billionaire Elon Musk.

Just after 1 p.m., close to three hours after docking, the hatch was opened between the Crew Dragon and the station. Soon after, the three astronauts already on the station welcomed Mr. Behnken and Mr. Hurley aboard, and the two new visitors were greeted with embraces and handshakes.

What happens during a space station docking?

The space station, at an altitude of about 250 miles, zips around Earth at more than 17,000 miles per hour. The fundamental principle of orbital dynamics is that objects in lower orbits move faster, and those in higher orbits move slower.

At launch, the Crew Dragon started out trailing the space station. But traveling in an orbit below the space station, it was moving faster and catching up. Through a series of maneuvers, the capsule raised its orbit, allowing the capsule to approach the station at a lower speed.

While the astronauts could dock with the station manually in an emergency, the Crew Dragon’s computers will automatically begin the capsule’s close approach to the space station at about 8:27 a.m., when it is about 4.5 miles away.

At a series of predetermined points along the approach, the spacecraft stops so that mission controllers on Earth can make sure everything is working as planned. At one point, when the Crew Dragon is about 720 feet in front of the space station, the astronauts will try out the manual control of the spacecraft as they continue to approach. This mission is a test flight, and NASA wants to make sure that astronauts would be able to successfully dock the capsule in case of a computer malfunction.

The computer will take over again for the final approach. Once docked, Mr. Hurley and Mr. Behnken will still have to wait a couple of hours for the completion of tests needed to ensure that the seals between the spacecraft and the space station are airtight.

Has there ever been a docking accident at the space station?

Not at the International Space Station. The chances of a damaging collision are small because visiting spacecraft approach the station at very low speeds. But there have been a couple of instances in which the approach systems of spacecraft have malfunctioned.

SpaceX sent Dragon, its crewless capsule that carries cargo, to the space station for the first time in 2012. During that mission, the vessel’s navigation system encountered problems because of stray reflections off one of the station modules. SpaceX engineers reconfigured the system from the ground, and the Dragon made a final approach that allowed it to be grabbed by one of the station’s robotic arms.

In 2017, another cargo Dragon aborted an approach because of a problem with its GPS system. It successfully approached the station the next day.

In 2019, an uncrewed Russian Soyuz spacecraft on a test flight similarly called off a docking problem because of a problem with its automated system. But it successfully docked on the second try.

SpaceX’s new Crew Dragon capsule made its first test flight to the space station last year with no astronauts aboard. After that visit, Russian space officials raised concerns that a possible sequence of malfunctions could put the spacecraft on a collision course with the station. Although the series of events that could cause such an error was unlikely, SpaceX’s engineers made changes to eliminate that possibility for this mission.

While the International Space Station has been spared, unintended collisions have occurred at earlier outposts. In 1997, a Russian Progress cargo ship crashed into Mir, the former Russian space station, during a test of the vessel’s manual docking system. That punched a hole in a laboratory module, knocked out power and caused an air leak. With makeshift repairs, the station’s crew was able to keep Mir operating.

What have the astronauts been doing since they were launched?

Crew Dragon has never gone to space with humans aboard. That means SpaceX and NASA have a great deal to learn from this trip to orbit.

One of the most important goals of this trip was for the astronauts to get their first try at flying the spacecraft manually when they were still far away from the space station — essentially taking the spacecraft out for a test drive and seeing how it handles to the commands.

They also took a pause during the trip to give the public a tour of the capsule’s interior.

Mr. Behnken and Mr. Hurley also had time to change out of their fancy new spacesuits, eat a meal and sleep. They also promised they’d try out the bathroom.

In a video update on Sunday, Mr. Behnken said they were “surprised, I think, at how well we slept aboard the vehicle,” adding that it was quieter than the space shuttle.

They said they got their first view of the space station from the capsule during the night, and described the results of their manual flight test after their launch.

“The vehicle flew exactly like the simulators,” said Mr. Hurley.

What did they name the Crew Dragon capsule they traveled on?

Mr. Hurley revealed that he and Mr. Behnken had decided on Endeavour as the name of the capsule. Endeavour was also the name of one of the space shuttles, which in turn was named after the H.M.S. Endeavour, the ship commanded by James Cook as he explored the Pacific.

Each astronaut had his first trip to orbit aboard the space shuttle Endeavour, one of their reasons for choosing the name.

How long will they stay aboard the space station?

Originally, Mr. Behnken and Mr. Hurley were scheduled to stay at the space station for only one or two weeks. But those plans were made when NASA thought the mission would fly in 2019. With delays in the development of Crew Dragon and another capsule, Boeing’s Starliner spacecraft, NASA ran out of available seats aboard Russia’s Soyuz capsule to the space station. It now finds itself short-handed there, with only one NASA astronaut, Christopher J. Cassidy, currently on the station with two Russian counterparts, Anatoly Ivanishin and Ivan Vagner.

Thus, Mr. Behnken and Mr. Hurley are now expected to stay at the station at least a month to help Mr. Cassidy and potentially as long as four months.

What will they do aboard the space station?

When only three crew members are aboard the space station, astronauts have time for little beyond the day-to-day work of keeping the station running. That means less time for science experiments or more involved procedures like spacewalks. The presence of Mr. Behnken and Mr. Hurley will allow more work to be completed.

The two new crew members will also take on specific tasks. Mr. Behnken has trained to perform spacewalks, and Mr. Hurley took refresher classes on how to operate the station’s Canadian-built robotic arm.

What will happen when they go home?

When the mission ends, Mr. Hurley and Mr. Behnken will get back into the Crew Dragon and undock. A firing of the thrusters will cause the spacecraft to re-enter the atmosphere. Slowed by parachutes, it will splash down in the Atlantic Ocean, close to where it was launched.

If no major problems arise during this test flight, NASA will use data from this flight to certify that the Crew Dragon is ready for routine flights to the space station. The next Crew Dragon mission — and the first operational one — is to carry four astronauts: three from NASA and one from the Japanese space agency.

How does Crew Dragon differ from capsules of the 1960s?

The Crew Dragon is roughly comparable in size to the Apollo capsule that took NASA astronauts to the moon in the 1960s and 1970s. Earlier NASA capsules — Mercury and Gemini — were smaller.

The inside is far sleeker than what NASA astronauts sat in 50 years ago and even the space shuttles. The computing power available is much greater now, allowing touch screens to replace the buttons and joy sticks that were used in earlier spacecraft.

“Growing up as a pilot, my whole career having a certain way to control the vehicle, this is certainly different,” Mr. Hurley said. “So it’s a little bit different way of doing it. But the design in general has worked out very well.”

If you think you’ve got the right stuff to fly a Crew Dragon yourself, SpaceX has provided a web version of the system that the NASA astronauts would use if they needed to override the spacecraft’s automated systems. Some YouTube users have helpfully explained how to actually complete the docking.