The SpaceX Falcon 9 rocket that boosted astronauts Douglas Hurley and Robert Behnken into space provided a slightly rougher ride than expected during the later stages of the climb to orbit, but both said Monday they enjoyed their historic trip and marveled at a smooth-as-silk docking with the space station.
And yes, the Crew Dragon brought a "new car smell" to the lab complex.
"It absolutely did," said station commander Chris Cassidy, the lone American aboard the station until Hurley and Behnken arrived Sunday. "Then when we got that hatch open, you could tell it was a brand new vehicle, with smiley faces on the other side, smiley face on mine, just as if you had bought a new car, the same kind of reaction.
"Wonderful to see my friends, and wonderful to see a brand new vehicle," he said.
It was the first piloted launch to orbit from U.S. soil in nearly nine years, the first flight of a SpaceX rocket carrying astronauts and the first new crewed spacecraft to fly in space since the first shuttle mission 39 years ago.
Both Hurley and Behnken are space shuttle veterans, familiar with the initially rough ride when the orbiter's powerful solid-propellant boosters were firing and the transition to a much smoother experience after the boosters were jettisoned and only the ship's liquid fueled main engines were running.
The Falcon 9 is a two-stage rocket powered by liquid oxygen and kerosene. The first stage, featuring nine Merlin engines, generates 1.7 million pounds of thrust at liftoff. The rocket's second stage is powered by a single vacuum-rated Merlin engine.
"Shuttle had solid rocket boosters, those burned very rough for the first two-and-a-half minutes," Hurley said. "The first stage with Falcon 9 ... was a much smoother ride."
He said the shutdown of the first stage engines, the separation of the first and second stages and then the ignition of the upper stage's single engine was similar to the memorable launch sequence depicted in the movie "Apollo 13."
"So the first stage engines shut off, and then it took some time between the booster separating and then the Merlin vacuum engine starting," Hurley said. "At that point, we go from roughly three Gs (three times the normal force of gravity on the ground) to zero Gs for, I don't know, a half a second probably, and then when that Merlin vacuum engine fires, then we start accelerating again.
"It got a little rougher with the Merlin vacuum engine, and it'll be interesting to talk to the SpaceX folks to find out why it was a little bit rougher ride on second stage than it was for shuttle on those three main engines."
The Crew Dragon is designed to rendezvous and dock with the space station autonomously, without any direct input from the crew. But for the first piloted test fight, Hurley took over manual control twice to verify astronauts can fly the ship on their own if necessary.
There were no problems and when the Crew Dragon docked with the station Sunday morning, Hurley and Behnken were unable to detect the impact.
"The thing that really stood out to both of us, and we mentioned it as soon as we docked, is we didn't feel the docking," Hurley said. "It was just so smooth."
Hurley is a former test pilot and Behnken, who holds a doctorate in mechanical engineering from Caltech, is a veteran Air Force flight test engineer. They were selected for the first piloted Crew Dragon flight in part so they could bring those skills to evaluating the spacecraft before it begins operational missions to the space station in the late-summer timeframe.
"We're there to evaluate how it does the mission and so far, it's done just absolutely spectacularly," Hurley said. "It's a very clean vehicle. ... It does everything we need it to do for this mission, so we're very happy with that part of it."
Including the operation of the Crew Dragon's toilet. While he did not provide any details, Hurley said it is "very similar to the one we were used to in the space shuttle, and it worked very well. We had no issues with it."
NASA managers have not yet decided how long Hurley and Behnken will remain in orbit. The Crew Dragon is certified for up to four months in space, but the crew could be ordered home earlier depending on how the space environment affects the capsule's solar arrays, the weather in the Atlantic Ocean splashdown zone and other factors.
Not knowing when they might be coming home is "a little bit strange," Behnken said. "I'm trying to explain it to my son, just six years old, and from his perspective, he's just excited that we're going to get a dog when I get home. And so he's accepting that uncertainty and continuing to send messages to me while I'm on orbit."
The mission is expected to last at least six weeks and possibly up to four months, far longer than their relatively brief shuttle flights. Staying in touch with their wives, both veteran astronauts, and their two sons is a top priority for both Hurley and Behnken.
"One of the things I was most excited about (after launch) was being able to make a phone call home," Behnken said. "It's been a long time since I launched into orbit, and I've got a little boy who got a chance to watch me do that for the first time in his life. And I just wanted to understand what his experience was and share that a little bit with him.
"He was able to make the trip back to Houston after watching the docking from down in Florida and was pretty excited about the whole thing. So that was wonderful for me."