Here’s what you need to know:
When will the astronauts arrive at the space station, and how can I watch it?
On Saturday, two NASA astronauts, Robert L. Behnken and Douglas G. Hurley, were launched into orbit atop a SpaceX rocket. It was the first time the private company, founded by the billionaire Elon Musk, had ever launched humans into space. It was also the first time since 2011, when NASA retired its space shuttles, that astronauts had lifted off for the International Space Station from American soil.
Mr. Behnken and Mr. Hurley’s trip required a 19-hour trip around the planet as the spacecraft they were traveling in steadily caught up with the orbital outpost. Their capsule, the SpaceX Crew Dragon, is scheduled to dock at the space station at 10:29 a.m. Eastern time on Sunday. NASA Television is providing ongoing coverage of the trip to the space station. The Times is also providing live video.
A little after 8 a.m. Eastern time, the astronauts’ capsule was visible from the space station’s cameras.
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.
When the Crew Dragon was about 720 feet in front of the space station, the astronauts tried out the manual control of the spacecraft as they continued 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.
After the manual flight testing was completed, Mr. Hurley said to the flight directors at SpaceX’s headquarters in Hawthorne, Calif., that “it flew really well, very crisp.”
The computer then took 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.
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