Rebecca Lawler used to be a hurricane hunter, flying directly into storms to collect crucial data. Imelda Muller was an undersea medical officer, staying at dangerous depths in hyperbaric chambers for days at a time. Both women have faced some of the most extreme conditions on Earth—why not become astronauts?
The two Hopkins affiliates are among 10 individuals selected from a pool of more than 8,000 applicants for NASA's 2025 astronaut class. Since September, they've been consumed with astronaut training, a rigorous, two-year program that ensures astronauts are mentally and physically prepared for flight assignments, which could include exploration missions to low Earth orbit, the moon, and even Mars.
The Hub caught up with Lawler, who earned her master's degree in space systems engineering through the Whiting School of Engineering's Engineering for Professionals program in 2018, and Muller, who was completing a residency in anesthesiology at the Johns Hopkins School of Medicine when she was accepted to NASA, to learn more about what it takes to become an astronaut.
How did your previous work experience inform your decision to become an astronaut?
Muller: I worked as an undersea medical officer as part of a health profession scholarship program through the Navy. As you're going through your medical training, you can do further training in diving medicine, as well as nuclear medicine, to support our diving teams, our sub[marines], et cetera. It was an environment where we worked with a lot of multidisciplinary teams. There were a lot of scientific questions we were trying to answer, and that really appealed to me.
I was stationed for the majority of my time at the Navy Experimental Diving Unit, and that location does a lot of scientific research on both manned and unmanned diving—testing equipment, testing different diving profiles—and we have a really robust saturation diving program. Saturation diving is a special sort of diving where you dive deeper than you would traditionally on a regular scuba regulator. And you stay for longer periods of time on the order of days, sometimes weeks, living out of a hyperbaric chamber. And I think that environment in some ways is very, pardon my pun, out of this world, and the parallels to space are definitely there.
Lawler: I started out my career as a naval aviator. I went to the United States Naval Academy, also in Maryland, and studied mechanical engineering and was really drawn to serve my country and do it in a way where I could eventually solve technical problems.
I was fortunate enough to be selected for US Naval Test Pilot School, Class 149. That was actually the moment that set me on the idea that test pilots [can] become astronauts. We had an astronaut come and speak at test pilot school, and he made the connection that every space mission is a test flight. And I was like, I want to be a test pilot. This is incredible. So I started out my career as a test pilot, in the back of my mind being like, well, what is the next step? Could I possibly be an astronaut? And that was the first time I applied, and the answer was "no" at that point in my career.
After [I attended] JHU … I applied and was accepted to NOAA, and I got to fly not just during hurricane seasons, but also [work on] coastal mapping and marine fisheries. … I applied to NASA again, and the answer was "no thanks."
A former mentor brought me into United Airlines [to work for] the test team, and that world became even bigger for me. I'm working in the international industry, and we're talking about ways we can use the aircraft to further science. We're really focused on safety at a global scale. And at that point, I was like, I'm loving this career trajectory. I'm doing all the things I want to do. Do I want to apply to NASA one more time? And in 2024, I started the application process and in fall of 2025, I was selected. It wasn't a straight trajectory, but I loved it. And as I was telling someone earlier today, at any of those junctures early in my career, if I had been selected, I wouldn't have this full breadth of experience to bring in with me to be a useful member of the crew.
What has training been like so far?
Muller: Our training as a candidate is approximately two years, and we do training in many different disciplines to prepare us for missions on the International Space Station and our future missions to the moon and hopefully beyond. So that involves some training on the logistics of the international space system—the different hardware systems, different electronic systems, just getting familiar with the station itself and the anatomy of the station, if you will, and what it looks like.
We use [a swimming] pool as an analog for practicing our space walks. We go through robotics training. And then we do other things that are really translatable no matter what environment we're in, [like] team dynamics and working with others.
There are also a lot of physiologic changes that go along with being in space for a long period of time. We have an entire group of people here that support us from a physical standpoint and also a mental standpoint on how to prepare for going to space and also how to recover when we come home.
Lawler: Training's been fun. It's a lot of studying, which is great because everything that we study is really interesting. It involves flying T-38s [supersonic training jets], robotics, Russian language training, and spacewalks—and then I'm sure there's probably a bunch of other things that I'm missing. For me, I've been flying T-38s and [I'm] at the very beginning of learning how to do a spacewalk, and there's a lot of prep going into that. My first run, which is going to be me in the space suit with a classmate in the neutral buoyancy lab, will be at the end of February.
What happens after training?
Muller: Whatever NASA needs us to do, we do. A large component of our job is not just going to space, but also supporting our fellow astronauts and our astronaut office and integrating with different disciplines here at NASA for the larger support of those missions.
This is a really interesting time in space right now, because while we have a presence in low Earth orbit on the International Space Station, we're also with the Artemis program moving toward moon missions and looking to establish a presence on the moon, which will then help us to develop further technology and give us more of an understanding of how to go even deeper into space, like [to] Mars. I'm young in my career and hope to see a lot of that throughout my lifetime.
What are you looking forward to most about potentially going into outer space?
Muller: The experience for myself in terms of what it feels like on your body is something I'm very curious about, I think from having a medical background. I really am looking forward to the moment where you can look outside whatever space vehicle you're in and see Earth from that perspective. I think that's probably a common thing among people who gaze at the sky and who also have had that experience in the past. And I guess one other thing I'm interested in is I'm always curious what it's like to sleep in space. That sounds like a really odd thing to be excited about, but I felt the same way about saturation diving, and I have that same curiosity for what it'll feel like up there.
Lawler: What I'm looking forward to the most is, whatever mission I get assigned for, seeing that I've built a strong enough foundation [in training] to be a useful member of the team. I'm just really excited to do the work and to be able to contribute in some way.
