An artist's concept shows the SpaceX Crew Dragon spacecraft undocking from the International Space Station.
  • SpaceX has completed its historic first flight of people: NASA astronauts Bob Behnken and Doug Hurley splashed down successfully a little before 21:00 South African time on Sunday night.
  • Behnken and Hurley boarded the company's new Crew Dragon spaceship on Saturday, undocked from the International Space Station, and flew away.
  • The crew landed their ship, which they named "Endeavour," in the Gulf of Mexico on schedule and on target.
  • Elon Musk, the founder of SpaceX, had described the landing phase as his "biggest concern" for the mission.
  • Visit Business Insider SA's homepage for more stories.

Bob Behnken and Doug Hurley have returned to Earth.

The two NASA astronauts splashed down, on time and on target, a little before 21:00 on Sunday night, returning America to the status as a spacefaring nation capable of launching people into orbit and returning them successfully.

Behnken and Hurley travelled in a vehicle called Crew Dragon "Endeavour," a spaceship designed, built, and operated by SpaceX. It's SpaceX's second experimental flight of the vehicle, a mission called Demo-2, and the aerospace company's first time putting people on board.

The Demo-2 mission's departure makes SpaceX, founded by Elon Musk in 2002, the first company in NASA's Commercial Crew Program to successfully pull off a visit to the space laboratory.

Behnken and Hurley's return saw them perform a risky descent through Earth's atmosphere - the phase of the flight that Musk had called his "biggest concern."

The landing makes for the first crewed American spaceship to leave and return to Earth since July 2011, when NASA retired its space shuttle program.

The beginning of the end to an historic 63-day mission

NASA astronauts Bob Behnken and Doug Hurley prepare to depart the International Space Station aboard SpaceX's Crew Dragon spaceship on August 1, 2020.

Behnken and Hurley launched to orbit on May 30 and docked to the ISS a day later, beginning their historic 63-day mission chockful of science, space station maintenance, and breathtaking views of Comet Neowise.

But all good things must come to an end, and the crew began loading supplies, experiments, and personal effects into Endeavour early Saturday morning.

Once they were packed up, they said goodbye to the ISS crew members they lived and worked with for two months: NASA astronaut and station commander Chris Cassidy, and Russian cosmonauts Anatoly Ivanishin and Ivan Vagner.

The crew then fired departure burns to build up a protective "keep-out sphere" around the space station, to begin their journey in earnest.

Hurley later tweeted his thanks to the space station crew, called Expedition 63, using Endeavour's Wi-Fi.

"It was an honor and privilege to be part of Expedition 63," Hurley said. "Now it's time to finish our DM-2 test flight in order to pave the way for future Dragon crews. Go Endeavour!"

If all goes well - the path of Hurricane Isaias has allayed early concerns about the safety of landing near Florida - the astronauts will splash down in the Gulf of Mexico on Sunday at 20:48 South African time.

To safely return to Earth, though, the astronauts must perform a series of critical manoeuvres with Endeavour over the next 19 hours.

From orbit to splash down

An illustration of SpaceX's Crew Dragon spaceship returning to Earth with a blaze of plasma ahead of its heat shield.

The first steps Behnken and Hurley took included firing the spaceship's thrusters to slip into the correct orbit. NASA will perform more remotely while the astronauts sleep.

After they woke up on Sunday, the crew prepare for landing. Around 19:45, according to a NASA TV schedule, the astronauts bjettisoned Endeavour's cylindrical trunk. The heavy piece of hardware powered and helped navigate the ship in orbit, but isn't needed during landing. Dumping the trunk is essential to exposing the heat shield of the aerodynamic crew capsule for the next stage of the flight.

Around 19:51, they'll fired Endeavour's built-in thrusters for about 11 minutes to dramatically slow down the capsule, helping it fall from orbit and back to Earth. At that point, the heat shield absorbed heat reaching nearly 2,000 degrees Celsius that's generated by plowing through the planet's atmosphere at about 25 times the speed of sound.

It's this phase that had concerned Musk, SpaceX's CEO and chief designer, more than any other.

"The part that I would worry most about would be reentry," Musk told Irene Klotz of Aviation Week ahead of the launch in May.

The spaceship capsule has an asymmetric design to accommodate its emergency launch-escape system thruster pods. And the imbalance caused by those pods - though very unlikely to cause a problem - is the core of Musk's concern.

"If you rotate too much, then you could potentially catch the plasma in the super Draco escape thruster pods," Musk said, adding that this could overheat parts of the ship or cause it to lose control due to wobbling. "We've looked at this six ways to Sunday, so it's not that I think this will fail. It's just that I worry a bit that it is asymmetric on the backshell."

But Endeavourb automatically deployed a set of drogue parachutes and slow to about 200 kilometres per hour, then four large main parachutes that decelerate Behnken and Hurley's capsule before they splashed into the ocean at around 25 kph.

The astronauts reported all well as they waited for recovery teams to secure the capsule and take them aboard the small fleet that surrounded the site.

An August 1 map shows NASA and SpaceX's landing zones for the Crew Dragon Demo-2 mission amid the estimated path and conditions of Hurricane Isaias. Pensacola (left) and Panama City (right) are indicated with a red arrow. The outer-edge green shows a 5-10% chance of sustained tropical storm-force winds.

Along with getting home, Behnken and Hurley performed an essential step in proving that SpaceX's Crew Dragon ship is safe to fly people in the future, including private citizens. NASA and SpaceX plan to finish reviewing data from the experimental mission over the following six weeks, likely resulting in its crucial human-rated certification from the space agency. 

In a future mission that NASA recently announced, astronaut Megan McArthur (who is married to Behnken) will ride the same Crew Dragon ship to orbit for a roughly six-month stay.

Ahead of the Demo-2 mission, NASA estimated a roughly 1-in-276 chance of losing the crew at any point during the flight.

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