Michelle Obama, Tom Cruise and Floating M&Ms: Inspiration4 Relive 'Amazing' SpaceX Journey

Inspiration4 The Inspiration4 crew in the Dragon's cupola

What's it like flying atop a SpaceX rocket and leaving Earth? Just ask the Inspiration4.

Speaking with PEOPLE in their first interview since returning to the planet on Sunday, the world's first all-civilian astronaut crew relives their breathtaking journey to space after launching from Kennedy Space Center in Florida last Wednesday.

"It was one of the smoothest rides I think we could have expected compared to what we'd heard," mission specialist Chris Sembroski, 41, says in this week's issue.

"It was amazing just to ascend up into space," he adds of the launch, which was powered by the Falcon 9 launch vehicle and lit up the Florida sky. "It's like you're driving down a gravel road in a pickup truck, but not an old one — kind of a newer model."

"It was still better than described," adds commander Jared Isaacman, 38, who helped design the six months of intense training he underwent alongside his crew members.

"I was very surprised," pilot Dr. Sian Proctor, 51, says of their fun ride into orbit, which reached 17,000 mph.

SpaceX Inspiration4 launch

Launch viewers could feel the joy emanating from Proctor, who gave two thumbs up as she became the first Black woman to serve as pilot for a space mission. But what viewers didn't know is that former First Lady Michelle Obama had just given her a congratulatory call.

"I could say, 'Thank you. You're my hero,' and she was amazing. I'm just so thankful that I got to share with my crew that moment," says Proctor, a geology professor who thought she'd missed her shot at space after being passed over as a NASA astronaut finalist in 2009.

For more on Inspiration4's history-making mission benefitting St. Jude, pick up the latest issue of PEOPLE, on newsstands Friday, or subscribe here.

As they approached space, "we were laughing," says medical officer Hayley Arceneaux, 29, who is now the first person with a prosthesis, the first pediatric cancer survivor and the youngest American to orbit Earth. "We were talking throughout the whole thing and celebrating each milestone that we hit."

After reaching orbit, they marked another milestone: opening the hatch of the Crew Dragon Resilience's giant cupola — which SpaceX says is the largest continuous window ever in space.

"It's burned into my brain, that image of our planet from the cupola, and I just keep seeing it again and again — and I'm just amazed," says Proctor. "So beautiful."

Inspiration4 Hayley Arceneaux in the Dragon's cupola

Though the Dragon is a little larger than a minivan, all four crew members were able to squeeze into the cupola at the same time.

"That was a questionable moment," quips Isaacman. "It would be really awkward if we were all stuck here."

"Oh my God, this guy," says Sembroski.

Looking back, his most hilarious memory involves some floating treats in between meals of pizza and lamb.

"It was hilarious seeing Jared and Hayley fail so badly at first catching M&Ms," says Sembroski. "Then they got better and their batting average definitely improved as we went through the flight. But yeah, we had M&Ms bouncing around all over."

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Thanks to zero gravity, Arceneaux found she actually slept better in space.

"Just floating above my seat, I was comfortable," she says. "I was surprised. I was wondering how I would sleep without a pillow. I think that was my biggest concern about sleeping, but I was comfortable."

Making it even sweeter was a video call with St. Jude cancer patients — a full-circle moment for Arceneaux, who beat cancer at St. Jude when she was 10 and now works as a physician assistant there. Isaacman — the billionaire and Shift4 Payments CEO who paid for all four seats — designed the mission to raise $200 million for St. Jude and donated $100 million himself. One of their top priorities, he tells PEOPLE, was spending time with St. Jude patients while the crew was in space.

"Even before the mission, what I was looking forward to the most was talking to the St. Jude patients, and that is going to be the thing I take away the most from the mission," Arceneaux says. "Getting to share that with the kids and show them what their future can look like was a huge honor for me."

St. Jude Children's Research Hospital/YouTube Inspiration4 crew speaking with St. Jude patients

"That was special because I love Hayley," says Proctor. "We've become really close over the last six months [of training]. This mission has been all about doing good and there's nothing better than knowing that we could inspire these kids and give them hope. I think that eclipses everything else, even talking to my family."

"Hear, hear," adds Isaacman. "Nothing comes close to the conversation with St. Jude."

That even includes their chat with Tom Cruise, who called into the Dragon on Friday. "Maverick, you can be our wingman anytime," the Inspiration4 tweeted.

Inspiration4 Inspiration4 splashdown

"That was certainly a cool conversation because the four of us, during the 30-hour simulation, I won't say who, but it was discovered that at least one crew member had never seen Top Gun before," Isaacman says, teasing an unidentified crew member. "We tried to right that by all four of us on our flight tablets hitting go at the same time, watching Top Gun."

Isaacman and Sembroski also watched Mel Books' 1987 classic Spaceballs as they were gearing up for re-entry on Sunday — but it wasn't all fun and games.

"I think it would be fair to say — and everybody should chime in here — I do think there was probably a greater degree of stress on the way downhill than there was on the way up," says Isaacman.

SpaceX Inspiration4 crew after splashdown

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"I think there were a lot of things going through our minds, but [we had] total, complete trust in SpaceX and the team, just as there was in the beginning," he adds. "We carried that through all the way to splashdown."

"We were so excited to see what those bright orange glows would turn out to be — and we saw the flashes, we saw some of the orange," Sembroski recalls. "It wasn't a big fireball like you see in the movies, but it was really, 'Wow, we're being hurled through the atmosphere and we get to see what that plasma looks like.' "

The crew's mic-drop moment came when they stepped out of the Dragon on Sunday and danced — a feat considering some NASA astronauts who have had longer periods in orbit have needed to be carried out on stretchers.

Jared Isaacman/instagram Jared Isaacman and wife Monica with their children after his return to Earth

"I was just so happy that we splashed down, we completed our mission and we got onto the boat," says Proctor. "I was just dancing with joy."

"We were determined to send that inspiring message that anyone can go to space and walk away from it with ease," says Sembroski. "We were feeling great and ready to walk out like the astronauts that we are."

To donate to St. Jude, go to stjude.org/inspiration4.