Astronaut-in-Training Hayley Arceneaux Climbs Mt. Rainier with Prosthesis in Leg: 'Daunting'

Hayley Arceneaux/Inspiration4 Hayley Arceneaux on Mount Rainier

Hayley Arceneaux is heading to space — and along the way, she's taking PEOPLE readers inside her out-of-this-world experience by sharing her personal diary entries. Though the 29-year-old has a career as a physician assistant at St. Jude Children's Research Hospital in Memphis, Tennessee, where she beat cancer at the age of 10, Arceneaux is adding astronaut to her resume by training for the first all-civilian mission into outer space alongside billionaire Jared Isaacman (the Shift4 Payments CEO who is sponsoring the SpaceX flight), Christopher Sembroski and Dr. Sian Proctor. Together they are striving to "inspire support for the lifesaving work of St. Jude," the hospital says of its $200 million fundraising goal. Before the Inspiration4 crew blasts off to space for a three-day mission this fall, check people.com for more entries from Arceneaux's diary.

Let's just say I've become an expert at living out of a suitcase. For the last few weeks, the Inspiration4 crew and I have criss-crossed the country, from Alabama to North Carolina to Los Angeles to Las Vegas, as we continue training for our upcoming mission to space.

I can't believe how much we have learned over the past few months, especially as the training pace has picked up these last weeks. In altitude chamber training, we experienced brief moments of low oxygen and high carbon dioxide levels; turns out, not surprisingly, that my handwriting and math skills decline significantly when my oxygen saturation drops below 30 percent. We visited NASA's Space Camp in Huntsville, Alabama, where we played with all of their cool toys, including one that simulates moon gravity (yes, there was lots of moonwalk dance moves). While there we were also spun quickly in all directions in the suspended Multi-Axis Trainer, a quintessential space camp experience. We continued our academic studies as well as spent more time together in the Dragon capsule stimulator at SpaceX to make sure we are well prepared for any situation that could arise on our mission.

John Kraus/ Inspiration4 Hayley Arceneaux (center left) undergoing zero-gravity training with her Inspiration4 crew (l-r): Chris Sembroski, Jared Isaacman and Dr. Sian Proctor

Perhaps most exciting about our recent training was the zero-gravity flight also known as the "vomit comet." To achieve zero gravity, the plane — from cruising altitude — ascends straight up in the air then descends straight down. It's when the plane is coming down that we experience 20 to 30 seconds of weightlessness. We did this 16 times. This was one of the most fun experiences of my life! Getting to float and do multiple flips in the air gave me a feeling of freedom.

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Scott Poteet/ Inspiration4 Hayley Arceneaux with her Inspiration4 crew on Mount Rainier

Astronauts make zero gravity look easy, but it's pretty challenging and requires technique. I hit the ceiling and walls several times and learned that the secret is if you're heading toward a wall to lightly tap it in order to change directions. The harder you hit the surface, the harder it will propel you in the opposite direction. After that training, I feel much more confident going into three days of zero gravity.

Of our training sessions, the most daunting was climbing Mt. Rainier in Washington. This experience served as crew bonding and "getting comfortable being uncomfortable," as our commander Jared put it. I trained strenuously in the gym for a month before the climb, but I still wasn't sure if I'd be able to physically do it given the prosthesis in my leg. The first day we hiked for almost 10 hours through the snow. Making it to our destination at 10,500 feet high filled me with such pride.

Throughout training, especially in the difficult moments, I don't often think about my own cancer journey. I think about the patients I treat at St. Jude. They are my inspiration. We ask so much of them during treatment, yet they never complain; instead, they uplift the adults all around them. When I was climbing Mt. Rainer, I thought about how I could share the experience with them. Climbing a mountain is a lot like battling cancer. You have to keep the end goal in mind, but also take one — sometimes hard, painful, difficult — step at a time to reach your destination.

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In addition to all that I've learned about space, rockets and astronaut-ing, I've also learned so much about myself. This experience has made me feel stronger than I even knew I was. That invaluable lesson will stay with me for the rest of my life.

To learn more about St. Jude Children's Research Hospital, the Inspiration4 mission and ways you can support and participate, visit stjude.org/inspiration4. Fans can also follow Hayley's personal journey into space on Twitter.