NASA astronaut Bob Behnken said the fiery plunge on SpaceX's Crew Dragon 'felt like we were inside of an animal'

• The NASA astronauts Bob Behnken and Doug Hurley completed their mission on SpaceX's Crew Dragon spaceship when they landed in the Gulf of Mexico on Sunday.
• The spaceship's scorching-hot fall through Earth's atmosphere, parachute deployments, and splashdown went as planned.
• From inside the Crew Dragon, Behnken said the return trip felt like being "inside of an animal," with violent jolts along the way.

The NASA astronauts Bob Behnken and Doug Hurley plunged through Earth's atmosphere at 25 times the speed of sound on Sunday, slowing just in time to land safely off the coast of Pensacola, Florida.

The splashdown concluded their two-month mission flying SpaceX's new spaceship — the Crew Dragon — to the International Space Station and back, making them the first people to fly aboard a commercial spacecraft.

Each step in their return trip to Earth went as planned. But inside the spaceship, the astronauts said, the flight didn't feel as smooth as it may have looked.

"The landing was — I would say it was more than what Doug and I expected," Behnken said in a press briefing on Tuesday. "I personally was surprised at just how quickly events all transpired."

Though they were pleased with the process, Behnken added, "it felt like we were inside of an animal."

Of the mission in general, he added, the astronauts will have suggestions to help SpaceX and NASA make the Crew Dragon "a little bit more comfortable" for future astronauts.

The pivotal moments of the landing process — the capsule separating from its trunk, the parachutes deploying as they approached the Gulf of Mexico — felt "very much like getting hit in the back of the chair with a baseball bat," Behnken said.

The first of those jolts came when the capsule jettisoned its trunk — a lower section outfitted with fuel tanks, solar panels, and other hardware, which the astronauts no longer needed. The ride only got bumpier from there.

'It doesn't sound like a machine'

Once they started edging into the atmosphere, Crew Dragon "came alive," Behnken said, firing its thruster to stay on course. The astronauts could hear the atmosphere rumbling around them.

"As the vehicle tries to control, you feel a little bit of that that shimmy in your body," Behnken said. "So we could feel those small rolls and pitches and yaws."

The spacecraft fired its thrusters continuously, pushing itself further into the atmosphere. Behnken said he recorded some audio of the sounds, which got louder as they descended.

"It doesn't sound like a machine — it sounds like an animal," he said.

That's when he felt the capsule heating up, and the force of Earth's gravity pulling on them for the first time in two months. He said it felt like being in a centrifuge.

That strong force restricted their movements, so they didn't get to crane their necks to look out the windows below their feet. If they had, they might have seen the layer of scorching-hot plasma that was wrapping around the spacecraft — a "really thin, pinkish hue," as Hurley described it from his prior experience on the space shuttle.

Then the parachutes deployed, giving them "a pretty significant jolt," Behnken said. A few minutes later, the capsule landed in the ocean.

"We felt the splash and we saw it splash up over the windows," Behnken said. "It was just a great relief, I think, for both of us at that point."