skip to main content
Home  /  Interviews  /  Robert L. Behnken

Robert L. Behnken

Robert L. Behnken

NASA Astronaut and Acting Deputy of Flight Operations, Johnson Space Center

By David Zierler, Director of the Caltech Heritage Project

January 31, 2022

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Wednesday, January 5, 2022. I am delighted to be here with Dr. Robert Behnken. Bob, it's great to be with you. Thanks so much for joining me.

ROBERT BEHNKEN: No problem, David. Good to talk to you today. Happy 2022.

ZIERLER: Happy 2022! Bob, to start off, the reason we came together today, tell me what it was like when you got word that you had received the Distinguished Alumni Award from Caltech.

BEHNKEN: It was actually a really cool honor for me. I did get a letter in the mail. A FedEx package came with a letter, kind of old school rather than electronic or a phone call, even. I know when I was selected for the Astronaut Office, that came via phone call. But this came with a letter in the mail, which was pretty cool to actually receive. I had been, like everyone else, living through the pandemic, so things were relatively quiet. As a part of my post-flight experience from my most recent mission, I didn't visit a lot of locations, and Caltech was one of the stops I'd hoped to make in person at some point but hadn't had a chance to go out and meet them. Receiving the letter was very much appreciated and kind of exciting, since I hadn't been able to reach out to them or visit with them post-flight, like I would've expected to. It was great to see that the mission was recognized and appreciated, and my roles and responsibilities were something the university had been following along with, even if we didn't get to shake hands and see each other in person.

ZIERLER: In what ways was it a moment for you to reflect on how your education at Caltech has helped you achieve all that you've done in your career?

BEHNKEN: Whenever you're recognized by an organization that you sought out to be a part of–I had, of course, like all students, applied to attend Caltech and then spent several formative years there in a research group, both amongst the students and the faculty–and when that group reaches back to you and recognizes you as somebody that, in addition to being a part of the institution, you're a part of the things that they're proud of going forward, it's really, truly an honor. Caltech has Nobel laureates, a rich history, some outstanding scholars that have been a part of it, so to be recognized by that community was something I was able to reflect back on. And of course, it was formative for me to have gone through my education at the university, but at the same time, it was something that, for them to be able to reach back and recognize me was truly, truly an honor.

ZIERLER: Just as a snapshot in time circa January 2022, what are you currently working on, and what's exciting that's happening now at the Johnson Space Center?

BEHNKEN: Here in 2022, we are looking forward to continued operations on the International Space Station. I think it might've been New Year's Eve or thereabouts that we got word that the Space Station was going to be extended. The White House recognized and announced that their plan was to extend it through 2030, so that is pretty neat, as somebody who built that space station during my Shuttle missions, along with all the other astronauts who were part of that assembly process. Then, to have lived on board and been a part of maintaining it, to see it continued was exciting news. At the same time, we're moving towards, hopefully in the March timeframe, getting a chance to launch Artemis 1, which is the next further-out destination vehicle. We'll be launching the Orion Capsule and demonstrating that we can go back to lunar velocities and return to earth safely on the first flight of that new system prior to launching crews with the Artemis 2 mission here in just a couple of years. That's ongoing at the Johnson Space Center.

My role, I'm currently the Acting Deputy of Flight Operations at the Johnson Space Center, which is kind of funny because it's flight operations, but it's primarily spaceflight. We do have some aircraft, but it's primarily a space station. And that's one step up from the chief of the Astronaut Office. Now, I work in a supervisory role, at least in an acting capacity. I'm still an active astronaut, but I've taken a step up there to help with managing the Flight Director's Office, the Astronaut Office, the flight controllers who make all these missions possible, and kind of empower them to be able to go forward. For us, it's exciting times. The Orion spacecraft, the Dragon capsule that I flew on, we do have another low-earth orbit capsule that's headed into orbit, the Starliner that Boeing is building. There are new suits to do surface missions, there are landers for the moon that are under construction and development. It's just a wonderful time to be a part of human spaceflight.

ZIERLER: A question at the intersection of politics and space science. For someone who came of age during the Cold War, to think now, in 2022, there remain tensions with Russia, China is, in so many ways, partly an enemy, partly an ally, how do you see space exploration both as an opportunity to mitigate those tensions, and where do you see inevitably space science and space exploration as simply a new frontier of competition?

BEHNKEN: From my perspective, I think it's really important to kind of maintain a separation between civil space and military space and continue with a civilian space exploration venture and civilian space utilization efforts. Whether that's for satellites for communication, whether it's DirecTV, internet access, or wireless transfers, all those things that utilize that infrastructure in a civilian way, it's important to maintain that infrastructure and keep those lines separate. Of course, there are military reasons why you want to maintain much of those capabilities as well. We at NASA are lucky to be a part and have a robust position relative to continuing with the civilian space agency, and I think that's what's really important.

As much as we can, internationally, to go forward and engage in the civilian side of space exploration and space utilization, I think that creates the opportunity that, while there's competition, it's not in an offensive and defensive posture. We're in a competition to provide capability potentially on the civilian side, not in an offensive/defensive countermeasure sort of posture. For us as a nation, I think it's really critical that we continue that civilian and commercial aspect as kind of a centerpiece, if you will, of something we're trying to grow rather than retract from that and focus solely on building the military side. I think that would not set us up for the greatest success and utilization of space, and of course, it doesn't set us up to cooperate, if you will, with the international community rather than compete with the international community in maybe a less productive way.

ZIERLER: Another question on cooperation and competition, another major transformation in space science, the rise of private companies like SpaceX and Blue Origin. How has that changed NASA for the better?

BEHNKEN: It's interesting as to who changed who, if you look through that. Over the last decade, I do know on the military front, there were discussions as to how to create the opportunity for there to be more commercial space by creating more rocket launch opportunities and a push to create more opportunity. That more opportunity allows the commercial marketplace to leverage things that might be developed a little bit on the more military side. SpaceX with the reusable booster has created pressure against the alternate launch capabilities that were out there. Those reusable boosters have provided the opportunity for a lot more spaceflights and hardware to head into orbit, and there are pros and cons to that.

If you look at the size of the Starlink constellation, for example, there are folks who definitely have opinions as to how much is too much in terms of satellites or other things we're able to put into orbit. At the same time, to see Inspiration4 fly on the SpaceX front so quickly after we were able to accomplish the development of a new capsule and capability for launching from the Florida coast and see a private community be able to fly on that vehicle that had been primarily developed with the aid of NASA but not have NASA be the exclusive customer for it is very, very exciting. It's opportunity, and that's exciting for me.

ZIERLER: Before we take it back all the way to the beginning, one more question, one we've all been dealing with you. For you personally, and for the Johnson Space Center, how have operations been during COVID and the seemingly unending pandemic?

BEHNKEN: The operations from a space program perspective have been pretty impressive with what we've been able to continue to accomplish. We haven't really missed a beat in terms of being able to operate, get into low-earth orbit, and continue with the missions that were in front of us. It's been pretty inspiring to see what we've been capable of in the face of a pandemic. For those of us who have launched into space and been a part of the business for several years, quarantine's a routine part of human spaceflight. I know some folks probably remember or have seen pictures of what the Apollo astronauts went through after returning from the moon, being in an Airstream, behind the glass, waving to people, speaking on the microphone while they were separated, in case there was some sort of pathogen that came back with them, or they were changed in some way that would be detrimental to everyone else.

Quarantines have been a part of our business for a long time, and we're pretty comfortable phasing in and out of them. It's been a much longer-duration quarantine, if you will, but it's all stuff that we're pretty comfortable with and kind of know how to operate in and amongst. My quarantine for my flight probably started around the very beginning of the pandemic. At the time, I was traveling to Hawthorne pretty routinely. Probably weekly, either commercial or via NASA transport. We recognized that, at the time LAX started to have luggage screeners that were testing positive for COVID, which was the red flag that said, "OK, there's some sort of community spread happening in the Los Angeles area," and we're marching towards spaceflight, so if we were to pick up an illness, we'd be down to the backup crew.

In our case, did we have suits built for the backup crew? That could be a schedule impact. We were able to transition, if you will, to really focus on what things we needed to be a part of to preserve the schedule, the mission, the readiness to be able to launch, and the team, without missing a beat, was able to jump into that posture because it's what we do for every single spaceflight we launch people on.

ZIERLER: Well, let's go back and develop your personal history. First, tell me a little bit about your parents and where they're from.

BEHNKEN: My parents grew up in the St. Louis area. My mother worked at McDonnell Douglas, which was later kind of purchased by Boeing, and my dad was a construction worker who grew up in the area as well. During my formative years, if you will, my dad would take me on the weekends if there was extra construction site visiting that he needed to be a part of, that I might get some small task, putting grass seed or straw down to keep a hillside from washing away, spreading rock out, nailing things together, picking up parts of the construction process, debris that had been left behind. As I got older, hauling bags of cement from point A to point B because that seemed like a good idea for an adolescent boy to get some energy out from my dad's perspective. I had some of those responsibilities, but I grew up in the St. Louis area, and eventually, after going to high school at a place called Pattonville High School, I went to Washington University in the St. Louis area and stayed there through my undergraduate education before heading out to Caltech for graduate school.

ZIERLER: As a young boy, were you always interested in science?

BEHNKEN: I was definitely always interested in science, and I don't know exactly how I talked my father into it, but I talked him into getting the encyclopedia set, a hardcover set of encyclopedias at the house. That was something you used to do a lot, and now with Wikipedia and the internet, it's less necessary in terms of getting information and access to information. But in the 80s, I looked forward every year to what was called the Yearbook. It was the annual update you had to pay a little bit extra for to get the hardcover encyclopedia. At the time, it was in that annual writeup where I would get my best insight into what the Voyager probes that headed to the outer solar system had collected or to find out the latest number of moons around Jupiter or Saturn, and I looked forward to that.

I definitely was always interested in science. I had some great elementary school teachers. Mr. Weisenberg was one of the ones I always remember who pushed the scientific method on us, and he always challenged us to have a science activity or experience to demonstrate to the rest of the class in our desk. At random times, he would seem to pop up with, "Hey, who's ready to demonstrate something?" You would go up there, and he had a file cabinet to keep the things that were a little bit more hazardous, like the Bunsen burner or otherwise. You were supposed to have a plan, then he'd let you demonstrate some science activity.

That sense of wonder, and the requirement, from his perspective, that you explained what you thought was going to happen, then explain why it did, if it did happen, or explain what you didn't know and that you learned as to why your prediction was wrong. The scientific method training was something that, from an elementary school perspective, I was always excited about, and Mr. Weisenberg always created that spark, if you will, probably with 100 Bunsen burner lights to make it happen. But that's where my interest in science was kind of piqued.

ZIERLER: Where were you when the Challenger disaster happened, and what kind of effect did that have on you?

BEHNKEN: I was actually in high school when the Challenger disaster happened. With a teacher on board that mission, many schools across the country were following along in real time when we did lose Challenger. I was watching in a classroom, and we watched it happen in real time. Didn't understand what really had happened. I think no one really understood what had happened at the time, but I watched it in real time, and I think after it happened, the schools were challenged with figuring out, "Now, how do we explain this?" The loss of the astronauts became the real focus of the lesson, which was not a direction I think most of the schools were expecting. We ended up in a very different part of our education, if you will, of dealing with that loss, that tragedy, and the feelings that came along with it as a part of the education process.

Maybe a science teacher who was giving a presentation needed help from some other teachers relatively quickly once the scenario played out. For me, over the next several months, in an interesting way, I kind of pored over the news coverage that was available, and I watched the hearings, and I remember seeing Richard Feynman pull a piece of O-ring out of a Styrofoam cup in ice water and asking his questions. It struck me, even at the time, that somebody could find the crux of the problem and then communicate it so effectively, so broadly with something as simple as, "I have a piece of your O-ring material that you say is supposed to be good, and I put it in ice water. It appears to, with my little clamp, stay smashed and not be flexible anymore. Your whole explanation seems to have a hole in it, and I've been able to demonstrate it here," and to a wide audience.

And everyone understood when Richard Feynman laid the problem out in front of them in that way, and the importance of being able to communicate the science or your understanding to a wide audience was really effective, in his case, and it's what the nation probably needed. It's what we needed to get past the Shuttled disaster we'd had and move on from there. I had that keen interest in understanding, and once we understood it, had a keen desire to see us get back to flying for whatever reason. When Space Shuttle Endeavor was announced, that we'd invest, build a new Space Shuttle, and continue, at the time, I certainly didn't expect to fly on Space Shuttle Endeavor a couple of times as part of my astronaut career or a career that would take me into space, but I definitely pored along and watched C-SPAN or whatever the equivalent coverage was to follow those hearings and see how they played out. Again, not because I expected to fly on the Space Shuttle, but because I needed to know and get the closure, having seen that disaster firsthand.

ZIERLER: Tell me about the significance of being an Air Force ROTC scholar as an undergraduate at Wash U.

BEHNKEN: As a student at Washington University, in my position, it was not a cheap school, and I did need a way to pay for my education. My father had been in the military and also didn't have the means necessarily to pay for my education outright, so a lot of the burden for that would fall on my shoulders, whether it was loans or otherwise. I was comfortable, based on my dad's experience, joining the military, and that ROTC scholarship provided that opportunity. In order to get the scholarship, the Air Force actually asked me to be a physics major, not an engineering major, and I had interest on the engineering side as well, but I did discover that if you did both, you could have what you wanted and what the Air Force wanted as well.

There was a process where you could try to change your scholarship to be some other discipline. That was a long way, and you had to continue to do your physics education while you were trying to change your major, so you would be in this mode of getting yourself further behind if you started down your physics path and changed it to something else. If you were unsuccessful, and you had tried to do your engineering, you would be in a hole from a physics perspective. If you did it the opposite way, where you bet that you should do mechanical engineering, you'd be in a hole on the other side. I was able to do both and let the process play out. When I actually finished my undergraduate education, probably the most advantageous thing that happened was that the Soviet Union collapsed, and the number of ROTC scholarships that had been awarded was much greater than the need of military officers they needed to bring on active duty.

My start in the Air Force was delayed, and I knew I could at least work towards a master's degree. I did apply at Caltech, and I did have the luxury of a young faculty member named Richard Murray, who reached out to me and was willing to take that risk on me. I didn't know if I could stay around long enough to work on a PhD or not because I could only get chunks of time approved by the Air Force, and I had gotten the first chunk, which allowed me to get started on a master's degree after having wrapped up at Washington University, and then was able to extend with the Air Force and continue on into graduate school.

ZIERLER: Any idea why the Air Force wanted you to focus on physics as an undergraduate? Did you do particularly well on some aptitude test or something like that?

BEHNKEN: I had done well on the generic aptitude tests that were out there, but I really do think, on the Air Force side, every year, they felt they needed a certain number of physicists, and those physicists would get positions in various research laboratories, there'd be roles and responsibilities, whether it was optics or they otherwise had needs they were trying to fill. I think I met the aptitude for physics, and interestingly enough, one of my high school cohorts actually went off to MIT on an ROTC scholarship for physics as well. We both had done well enough in our high school education and the generic aptitude test that that was the direction they sent us. It wasn't either one of our first choices, but it was what the opportunity on the military side presented to us.

The funny part about it from my perspective is, I actually never worked as a physicist in the Air Force when I came on active duty in the Air Force, they said, "Hey, you could do this mechanical engineering job. [Laugh] And they sent me off to do that, never considering my physics education. I think that happens a lot on the military side, where they gave me a scholarship and didn't need me to come on active duty. They had told me to study physics, but they needed a mechanical engineer when the time came. It just happens that way sometimes when folks are looking at how you're going to, from a human resources perspective, create opportunity for folks in the future. It's a little bit of a challenge to predict the future, but keeping opportunities open is important as well.

By getting folks and giving them good educations, they're able to create the officers or engineering and science workforce they need, and that's what's important, they've created that set of people who are able fill a diverse set of roles. Physics is not a bad place to start if you're looking to be able to address most of engineering, anyway, so it's a good place to get people started.

ZIERLER: I'm curious, as an undergraduate, did you see your ROTC training as at least a possible avenue to a career in NASA or as an astronaut?

BEHNKEN: As an ROTC student, I did look at the various services and how they utilized the officers they had. The Air Force was the one service that actually took engineers straight out of undergraduate education and employed them as engineers, and there were positions in what's called the Air Force Research Lab. There are, I think, four different bases now. The number of bases and where they have facilities is kind of hard to keep track of. But single-digit locations around the country with various different focus areas, if you will. They will utilize their engineers in that way. For the Marines, you might still need to be an infantry officer first, then seek an opportunity as an engineer later. The same in the Army, where maybe you'd have another role, then when you were more senior, you might come back and do support for acquisition, development of new programs, and things like that.

But the Air Force would take people right out of school and send them off to do this engineering development work, and I was interested in that. I picked which ROTC I did in order to create the opportunity to go off and be an engineer or scientist for the Air Force. My expectation was probably not to stay for 20 years in the military as an engineer. You don't have a lot of general officers in the military that are just developmental engineers. And I say "just" because they're called generals for a reason, because they are generalists and cover a wide spectrum of areas and problems that need to be addressed. I picked my service based on what that opportunity was going to go off and potentially be.

ZIERLER: When you were thinking about the graduate school and settled on Caltech, I wonder if seeing Richard Feynman and his elegant description of the problem planted a seed in you as to what a special place Caltech was.

BEHNKEN: It probably planted part of a seed. I didn't associate Richard Feynman with Caltech, but later on, I did recognize him as a Caltech person. I recognized him as a scientist able to jump into that engineering world and, in a very simplistic fashion, point out and communicate the crux of the matter. I didn't associate him necessarily with Caltech, but as an undergraduate, when I was considering graduate schools, my advisor at the time, I sat with him and asked him what to consider. He knew the conundrum that I was in as far as whether I had to go on active duty with the Air Force or take advantage of this opportunity of I could, if it was the best time, right out of undergraduate school.

My undergraduate advisor had taken a little bit of a different path, where, with a family, he had gone back to school, and that limited a little bit in terms of where he could go to school because he had a family that also needed to have a solution to what the future was going to hold at the same time that he was trying to prepare himself for what he was going to do next. The one thing he did tell me was that where you went to school could open doors. You can get a great education at a lot of places, but where you go could open some doors. He said, "Hey, consider MIT and a couple of other places." Then, off on the side, he said, "Or someplace like Caltech."

He described it in a way that nobody really has enough experience with Caltech to know anything other than it's a special place because there are so few undergraduates and graduate students who then go off–and people who are touched with interactions with Caltech, I don't want to overstate it, but he was kind of implying a little bit of a mythology associated with Caltech as this wonderful place, but not everybody has enough experience with it to have it be completely firsthand. "It will always be someplace that, if people see you as a Caltech graduate, they're willing to consider that you might be able to fit into an organization in a way that they couldn't necessarily anticipate." I don't know if I'm describing that very well, but this idea that a Caltech person may come in with a multidisciplinary approach.

If you grabbed your person from Caltech who was a mechanical engineer, they may have an opportunity to do something completely different somewhere else, whereas another university, you might be very stereotyped as the type of engineer or subject matter expert you were, and that might be limiting in some way. In some sense, he described Caltech as this special place where people didn't have enough experience to pigeonhole you in some way, and he thought very highly of it. It intrigued me, and I applied. Of course, when the time came for folks to reach out to who the graduate students were going to be for a couple of those schools, Richard spoke to me and contacted me by phone, and I think for MIT, I got a form letter that said, "You could come," and they would figure out what I was going to do once I got there.

But Richard had some ideas, and I had the positive from my undergraduate advisor saying, "Having gone to Caltech will never close a door or take away opportunity for you in the future. Consider that in whatever choice you make." He didn't say, "Go to Caltech," but, "Consider keeping doors open throughout your career as maybe a strategy for not having to decide just yet and limit what your future possibilities are going to be."

ZIERLER: Just to clarify, the degree in mechanical engineer was your call or the Air Force saying, "This is what we want you to study"?

BEHNKEN: That was my call. I added a mechanical engineering degree. The Air Force wanted a physics degree, and to keep the scholarship people happy, I did that. At the same time, while they were paying for the school, you may to get a waiver, but you can do whatever number of hours in a semester that you can safely accomplish, so that's what I did. I did a double major as an undergrad.

ZIERLER: What kind of research did you want to accomplish at Caltech?

BEHNKEN: I was interested in robotics primarily. I think that was an area I wanted to focus on. I know that was an area that Richard had some experience in. I was also interested in control systems. Richard kind of pulled me in that direction. I think my first task at Caltech was as a teaching assistant for a class that wasn't going to be taught the first quarter I arrived but later in the year. It involved working on some hardware and getting a control system and interface up and running for it. That was interesting to me, that robotics flavor of things. After working on that aspect for a couple of years–folks who have met Richard know he has a very broad spectrum of interest and applies what he learns in one area to someplace completely different potentially, and that's one of his superpowers. If you look at what I was doing the first couple years, what came out of it was a focus on nonlinear control.

The next nonlinear problem that came out after some flexible robotic manipulator activities was one associated with jet engines, rotating stall and surge. It was a joint project that had MIT, a NASA connection on the East Coast, and UC Santa Barbara, and maybe a connection with another university. Richard picked up some funding from AFOSR, and that was a project I got hooked up with as well to focus on my PhD research. But it was still fundamentally connected back to the control systems idea, and robotics was the first step, but the more complicated nonlinear control associated with that was easily applied or transitioned to something probably completely unexpected, which was this rotating stall and surge and compressors.

It's kind of a funny story, as an undergraduate, I had worked on a project where we built a natural gas vehicle, and it had to have some gas injectors for the fuel injection for the system. We actually got the folks at Washington University to box up and send some parts from the natural gas vehicle project to Caltech so that we could wire them into the axial-flow compressor and use those fuel injectors for the GMC pickup that we had taken to competition as an undergraduate into what turned into the hardware that was used for my PhD thesis for controlling rotating stall and surge in this compressor box that had been built.

ZIERLER: How much interface did you have with JPL at all while you were at Caltech?

BEHNKEN: Really, none. I visited JPL a handful of times, and I know they had some micro-machining workshops that I went down for, did a couple of tours, but that was the extent of it. There was another student or two who were kind of in Thomas Building, where I was working, and they were working on master's degrees or other degrees, maybe an engineering degree. One of them was even focused on a PhD. But they were JPL employees who were working with Joel Burdick, I think, for the robotics work they were focused on. But I didn't have a connection, really, with JPL.

ZIERLER: During your time in graduate school, what kind of contact were you in with the Air Force? Was there a lot of uncertainty about whether you might be called up, when you might have to pause your graduate studies?

BEHNKEN: There was really not much contact at all. I think when I initially arrived, the program I was on was called an administrative delay for the first year, just to basically postpone the time I was going to go on active duty. As a part of that, UCLA wanted me to come down weekly to attend part of their program. But it was a little bit ambiguous, and my schedule really didn't allow taking the time to go down to UCLA during the week. The Caltech first year of graduate school in the master's program doesn't lend itself to spending a day at UCLA. [Laugh] That just didn't work out for me. They didn't push too hard, and they contacted me close to the end of my education at Caltech, when it was probably six months or so from when I was supposed to come on active duty, and I was looking to see where I could take the education I had and find a place to apply it because after completing a PhD in mechanical engineering, taking a position that was expecting an undergraduate degree in physics would've been a little bit strange.

Wouldn't have maybe been the best utilization of their manpower, to take me and put me in the wrong spot. That AFOSR contract or project that Richard was working on allowed me some connections with a couple of AFOSR recipients that were also inside the Air Force. The Air Force Research Lab has some facilities at different bases. There was one at Kirtland Air Force Base in Albuquerque, there was one in Florida at Eglin Air Force Base, there were folks at Wright Patterson, some others. I reached out to a couple of those places to find out where would be a good fit, and I did have a pretty good dialogue with a team that was at Kirtland Air Force Base, and they were doing what was the airborne laser program at the time. They were propagating a laser between two airplanes and trying to cancel out the atmospheric disturbances with adaptive optics or otherwise, so that they could put energy on a target or do imaging of a target, something they were looking at.

I was working towards potentially going there but was derailed in that effort. I know that team was interested in me. They actually offered to bring me out. There was a government shutdown that year, maybe the kickoff of all the government shutdowns back then. I was scheduled to go to Kirtland, and that trip got canceled with the government shutdown, and I ended up getting redirected and going to the base at Eglin instead. It worked out for the best long term for me. I still got to where I got to. But just really limited interaction right at the beginning when they thought I might need to do some extra stuff with that UCLA. Then, at the very end, when they were trying to figure out what to do with me, there was some connection with the Air Force, but other than that, I was mostly left alone.

My funding came through the National Science Foundation for maybe the second through the fourth year of my graduate studies. The Air Force really wasn't paying anymore for me. They had paid for my undergraduate school for ROTC, but graduate school was a fellowship through NSF or a teaching assistantship with Caltech, so they did leave me to my own devices to get through things. But in the end, they said, "You've been waiting too long. We just started clearing the books. You've got to come on active duty." I had a good conversation with Richard as to, "Hey, now's the time. I've got to go. Once they take me, it will be really hard to extract myself to come back and work on a thesis defense or otherwise." He worked hard to help me complete the activities I needed to get completed, and without his support, I'm sure I wouldn't have finished in the time that the Air Force allotted me.

ZIERLER: What were the central conclusions of your thesis research at Caltech?

BEHNKEN: We showed that you could control rotating stall and surge with a relatively simple model. The central conclusion was that you could take a complex system that included a staged compressor and the nonlinear dynamics associated with it, develop a very simplified model, apply it to that system, and then apply some relatively rudimentary nonlinear control to it, and get that system under control. You could reject the disturbances. We tried to model it a couple of different ways, with low fidelity, a much higher fidelity model, then did some system identification to show that we were capturing enough of the dynamics. There are some techniques where, based on how you sample, you can predict how many degrees of freedom need to be included in your model.

Maybe not the structure that the model has to take, other than it has to have this many degrees of freedom from a nonlinear perspective. We were able to demonstrate that that complex system could be simplified and therefore, controlled in a nonlinear fashion. Which was pretty cool. It was kind of a neat idea, neat concept. And we were able to bring it full circle from modeling, experimentation, controls, and system identification perspectives. It was pretty complete, if you will, in putting a bow on all the different aspects of that system.

ZIERLER: As a way to understand your motivations, what you had hoped to accomplish, while you were at Eglin, did you see that as training grounds for the Air Force Test Pilot School at Edwards Air Force Base?

BEHNKEN: When I was at Caltech, I was trying to consider what I was going to do next. That project with AFOSR, Air Force Office of Scientific Research, had an industry partner in Pratt & Whitney. United Technologies was the research piece in support of Pratt & Whitney. I did get a call at one point to ask if I had an interest in potentially working at United Technology when I wrapped up. I did talk to them. I remember having a conversation with an individual that we had been working closely with, and he was asking me what my future thoughts were. He said, "Should we try to explore the possibilities of navigating around this ROTC requirement? Is there a way to buy back? Can you take a loan or get some separation from this, maybe work with us?" I thought a little bit about it, and I told him that when I didn't want to pursue that.

If I could get to test pilot school and fly 25 different airplanes, pursue, if you will, the dream of being an astronaut, that was going to be something as a life experience I would regret giving up, that I would be really proud if I was successful when I was 50. I don't know if they would've offered me a position once we found out what it really entailed, but he was asking me what he thought my future held. I declined. When I got to Eglin, my goal for my Air Force career was to get to the Test Pilot School because I thought as an engineer, that life experience working on the development of a new airplane and maybe using some of the same ideas of trying to incorporate control systems, recognizing it's a complex system, that you need to simplify in some way if you have any hope of really being able to control it, at least with the computation power we had at the time, we would need to do those sorts of things.

I was interested in going that direction. Luckily, or maybe this opportunity presents itself everywhere, but the research lab I went to had a test pilot who was in charge of the organization, and I had the opportunity to work with a couple of those folks who had gone, done their test pilot careers, come back, and were doing leadership and management inside of that research laboratory, and they helped steer me towards that opportunity. At the first opportunity, I sent in an application, and I think on paper, I didn't meet the requirements. I didn't have enough time as a military officer to apply to the test pilot school. For whatever reason, I was selected anyway. I was at the Test Pilot School relatively quickly. As a Test Pilot School student, we all vied for the positions we wanted to do. The application of the AFOSR project, that rotating stall and surge challenge, part of it had to do with when you have airplanes that fly in unusual attitudes or make rapid turns, the airflow that goes in the inlet is pretty disturbed, which is a challenge for the engine to ingest in a way that doesn't cause bad things to happen. That was for the F-22 program.

I actually went from Test Pilot School off to the F-22 program as my next stop, if you will. While I was working there, I was picked up for NASA. If you wrap that whole story together, my ROTC career came with a four-year time commitment to the Air Force that you had to invest back to them to pay for your undergraduate school. Before I was done with my four-year commitment, I was in Houston in the Astronaut Office. I went through that whole experience and then looked back on it and said, "Wow. I'm here already." It wasn't the pathway that I expected. I didn't reach back to Mark and that team back at United Technologies and say, "I'm not 50 yet, I'm 28, and I've managed to get to what we had talked about just a few years ago," which was pretty cool.

ZIERLER: I wonder if you can convey what it's like flying an F-22 at the speeds they're capable of.

BEHNKEN: As a flight test engineer, the F-22 was all single-seat, so I didn't get to fly one. I got to do maybe the next best thing, which was fly in the F-15s and F-16s that would fly close to the F-22 while it was going through its test program until the F-22 flew away, and we couldn't keep up with it anymore. [Laugh] It's exhilarating. Most of the testing we did was at altitude, supersonic, and really, the work area out there at Edwards is pretty big when you're flying around in it, but when you have a new airplane that flies high and very fast, you get an appreciation for what you thought was a big work area, and very quickly, at the speeds the airplane can fly, you spill out into LA center or out of the work area. You've got to line up, set your test point, get it right at the beginning of the window, and get stopped, figure out an exit strategy because there's not much time.

When we went to fly the Space Shuttle when I went on missions later, there was a similar sort of perspective in terms of the criticality of accomplishing your burns at the right time to achieve the rendezvous profile or ascent profile to get to Space Station, or to get the reentry burns accomplished so that you come through the atmosphere at the right rate in a way that is one that the Space Shuttle can support as you come back. It was good training and good experience, but definitely a healthy respect for how fast and what the air crew that learned to operate and live almost in that environment, flying those airplanes, either fighting another airplane or ensuring something is safe by the type of maneuvering and flying that they're able to do.

ZIERLER: What was the process like, applying for and ultimately being selected for the Astronaut Candidate Training Program?

BEHNKEN: I was at Edwards Air Force Base at the time. I actually applied when I was a student at the Test Pilot School. In those days, selection process came around every two years. An awful lot of the test pilots at Edwards and at Pax River–I say test pilots, but the graduates of the test pilots, which includes both engineers and pilots–I would say, at some point, probably 50% of the folks in those schools actually apply to the Test Pilot School program. As a student at the Test Pilot School, I applied, and on the bases they'd have the test pilot schools, on the Navy side and the one on the Air Force side, probably half of the base, it seems like, applies to the Astronaut Office.

A large chunk of my class at Test Pilot School applied. I think four of us from the class were selected for interviews. If you went on the base, it was an interesting process, you needed a recommendation letter from the wing commander, the senior leadership in order to get approved to get a physical because you had to submit a physical as part of that process. The base didn't have enough resources for everybody who felt like they needed to apply to go off and get the high-end physicals, the pilot physicals you needed. It was an interesting process, and I think a lot of the folks on the base looked at me as a pretty junior person. Historically, folks who get selected in the Astronaut Office often apply two or three times before actually being selected. I was lucky enough to get interviewed with my classmates and end up being one of the two from my class who were selected that year.

Interestingly enough, one of my classmates, Garrett Reisman, he and I worked in Thomas Building together. He took the candidacy exams a year ahead of me, but we knew each other pretty well. We had socialized, done some hiking things together, were reasonably close. And he applied right after leaving NASA for the 1998 class. I knew I was probably not likely to get selected as a military officer until after I had been through Test Pilot School. He was selected with that 1998 class, and at that point, even as a student at the Test Pilot School, I was pretty confident I would be a good candidate because I knew Garrett, I knew he had been selected, and as peers at Caltech, I thought, "They selected him. Now, I've gone to Test Pilot School. They've got to picture me because I've done one more step than he did through that process."

When I went through the interview, he, it sounded like, had told a story about me during his interview process. Two years later, when they did my interview, they asked me to retell that story from my perspective when I got there. It was interesting to kind of go through that. Garrett is a super funny, humorous guy. It was an interesting experience that we can both laugh about afterwards, both the experience itself and having retold that same story to the same crowd of people two years later. I asked afterwards if we had told them the same story, and they said, "Well, pretty much. [Laugh] The hero in each of the stories might've been a little bit different."

ZIERLER: Were you still on active duty while you were in the training program? How does that work?

BEHNKEN: I stayed on active duty when I arrived in the Astronaut Office. There are some reasons why that's advantageous. If NASA got done with you and sent you back, then you at least have guaranteed employment going back to the service. But also, once you start investing in your career in the military, there are things like retirement. In general, the military officers that come across, NASA agrees to take them and then maintain proficiency in their flying and otherwise to keep them relatively proficient if they needed to go back to the military for whatever reason, the needs of the military, they could bring you back and put you back into your old role, and you could pick up where you left off. That's part of the agreement with NASA. Typically, most people don't go back. They typically stay with NASA and eventually transition to civil servant, then retire from their service. I've actually started that process now. I'm now on what's called terminal leave, and my Air Force retirement will become official in 2022, but I have started working as a civil servant astronaut at NASA.

ZIERLER: That's to say, theoretically, for example, after 9/11, the Air Force could have called you in for service in Afghanistan or Iraq.

BEHNKEN: They could. As an engineer, that would probably not be the most likely place for them to call me back, but they could've said, "We have this new need to do development of a system for IEDs, so we're going to have an airplane that can fly that detects, or activates them, or tracks people who use them," and I could've been tasked to go off and do the development work associated with something like that. Typically, the services are big, so the amount of benefit one person could make isn't high. Of course, if the needs were extreme, they could've definitely brought us back.

ZIERLER: What was the process like going from astronaut candidate training program to being an astronaut? What does that look like?

BEHNKEN: Really, the astronaut candidate program is about familiarizing you with the NASA systems that are out there. For me, it was basic training on the Space Shuttle and the Space Station. That equipped me to fill various roles. At the time–we've since retired the Space Shuttle–we had astronauts who operated the Shuttle when it was on the ground, we had astronauts that weren't assigned to the missions but that needed to operate it pre- and post-flight. We also had astronauts who serve as what's been called the Capsule Communicator, even though they're not all capsules anymore, who assist the crew through their daily operations or the activities that they have while they're headed into or on orbit, and that requires a pretty detailed knowledge of the systems and a recognition of what the crew members are actually going through so that you don't call them at an inopportune time, or you use the right words to get them most efficiently through the process that you need them to do while they're on orbit.

It really is focused on that familiarization with the systems astronauts use. It's also some indoctrination. We visited pretty much all the NASA centers, we went to Kennedy, we went to JPL, so I got a good tour of JPL, even though I had been at Caltech and been there a few times. I got a detailed tour as an astronaut. NASA Ames, Glenn, Goddard, Kennedy, Stennis. We visited all those places and interacted with those teams to understand what the different centers did, and that's really what the Astronaut Candidate Program is about. The majority of folks that are hired, that's a luxury.

The Astronaut Office gets the opportunity to select from a huge pool of people, and they can select a ton of qualified individuals. In some sense, we have way more qualified individuals that can do the job, so we have a really high success rate of folks making it through that first couple years of learning about NASA, about the systems, being able to jump in with the roles that we need astronauts to do, even on the ground, before they're assigned to missions at the end of that two-year period.

ZIERLER: Tell me about the first Space Shuttle mission, STS-123 Endeavor in 2008.

BEHNKEN: In 2008, I did launch on Endeavor for STS-123. It took two modules, if you will, to the International Space Station as part of the assembly sequence. The first Japanese module, which was a logistics pressurized volume, was the first component of a series of three major components on the Japanese laboratory that was added to the Space Station. We also took what was called Dextre, or the Special Purpose Dexterous Manipulator, SPDM, and it is a series of kind of two fingers, if you will, and it has a grapple piece as well that you can add to the end of the robotic arm that's on the Space Station.

There are end effectors and bolt-turning equipment that allow it to change out parts on the exterior of the Space Station that otherwise would need to be done with a series of spacewalks. I went to Space Station, and we installed that module, then there's some outfitting, once things are attached, that has to be done on the exterior. That one didn't need power, but it needed some thermal blankets to be installed. The robotic manipulator actually had to be assembled, so it came in about a dozen pieces that had to be attached. It's not exactly a dozen, but it's a series of pieces. We had to add the little fingertips, if you will, on each of the arms, had to get the arms off the platform and attach those to the body, there was a platform that we had to attach, there was a tool carrier that had to get installed.

Then, it removed a bunch of thermal blankets that were involved with that. We brought a Canadian and a Japanese piece to the International Space Station. It was also the first night launch after we had lost Columbia. When we lost Columbia, some insulating foam came off of the external tank that provided the fuel for the initial part of ascent and hit the underside of the orbiter, creating a hole, which was not good when it came time to come back through the atmosphere. As part of the return-to-flight, we developed a lot of systems to collect imagery to ensure that the heat shield of the Space Shuttle was still in good shape after the ascent, figuring out a way to do that in daylight, and then transition back to being able to launch at night.

As you can imagine, imaging systems might like the daylight a little bit better than the night in some cases. It was a step for us to be comfortable with being able to launch again at night. It was pretty neat. Unfortunately for my launch guest, the mission was only about 18 or 20 seconds before we disappeared into a deck of clouds, so they traveled to Florida to watch the ascent of a Space Shuttle for about 20 seconds. That was the end of my launch into space. [Laugh]

ZIERLER: Take me through the morning of launch day. What's going through your mind? What are the preparations? What does it look like?

BEHNKEN: It's interesting, it depends a little bit on your personality, I think. I'm the kind of person who goes through the training process, and I kind of have the excitement afterwards, if that makes sense. On the day of launch for me, I just have a series of stuff that I know has to be accomplished, and I have to do it by specific milestones, otherwise I'm not going to be on time to the spaceship launch, which would be at least embarrassing, if not something more significant. I got up, got some exercise, had a light breakfast. You have to meet with a flight surgeon typically to get another once-over on launch date to make sure you don't have any congestion or anything they aren't aware of that might impact your ability to go off and do the mission.

I got some light exercise in. For me, I wanted to get some exercise in, but I didn't want to overdo it and be dehydrated, sitting in my space suit, after having gone for a long run on the beach in Florida. A little bit of exercise because you know you're going to be sedentary, sitting on the Space Shuttle for a couple hours prior to launch. I picked my meal, always a turkey sandwich, jalapeño chips, and a drink, for the launch. Some folks historically have gone with steak and eggs because there's a tradition from some of the really old-school astronauts of picking something like that. I just picked something that I eat. My wife says I eat that every day, a turkey sandwich, but that's what I did for my meal.

As you start to get closer to the process of heading out to the orbiter, to the Space Shuttle, or to the Dragon capsule, in my case, for the third mission, you've got to put on the right outfit, which is some undergarments you wear under your space suit, you get some last-minute weather updates so you'll understand the weather that you might–in Dragon parlance, it's called weather you might escape into, on the Space Shuttle, it was abort into. If you couldn't take the Space Shuttle to space, you might have to take it someplace else. You needed to understand if it was raining in France or Spain, what the right place to go actually was. Similar with the Dragon capsule. If you're going to end up in the ocean, there are times when it's better to end up in the ocean, or if you can get across and make it to Europe, or make it to the US coast again after that first orbit. You get some details about that part of the story as well.

ZIERLER: Are you a bachelor at this point, or you're already one-half of an astronaut couple?

BEHNKEN: For my first flight, I was not married. I had a significant other, but I was not married. My future-wife was down in Florida for the event, and you've got family and everything, but you don't see those folks typically on the day of launch for a Shuttle mission. You see them in the lead-up, and in the week leading up, they're in a special quarantine as well. You might have a meal with them once a day as you complete your last minute studying and preparation for the mission. For the Shuttle missions, we had changes right up until the end, so the latest details on a spacewalk. There might be updates to the lighting conditions when you were going to arrive at Space Station, what the weather was doing in France, Spain, North Africa, depending on your mission. You were chasing that in the few days leading up. Your days were busy, but you did have a little bit of family time as a part of that. But you didn't interact with them particularly on launch day, they were not a part of the sequence for heading out to the launchpad.

ZIERLER: Emotionally and physically, I wonder if you can talk about the sensation of a spacewalk. What's it like?

BEHNKEN: I've done ten spacewalks now, and having been through that process a lot of times, I can tell you that for the first one, I was really focused on doing everything that needed to be done. You do have the ground bugging you and reminding you of what your next step is. And those Shuttle missions were very packed. Typically, every minute of the spacewalk was choreographed and required, and if you didn't get it done, you didn't have the luxury of adding another spacewalk in because the Space Shuttle typically had a lifetime it could stay in space before it had to come home. It would be pretty significant to add even a little bit of time, but to add another spacewalk would be super challenging potentially for being able to come home on time. Definitely, we were focused on getting that activity complete. I was able to open the hatch on my first spacewalk, which is not normal. Usually, you have an experience where an experienced crew member will open the hatch, and then the other member will egress and follow them out of the hatch.

I was able to do that on my first mission, which was just to open the hatch, pop out, and at the same time as realizing, "Hey, I've got all this stuff that has to happen," I've got this clock in my head, and I've got people bugging me to go forward, there's something wondrous happening right in front of me. Trying to manage and compartmentalize the distraction that comes with seeing the earth for the first time, climbing out in your own little spaceship of the hatchway and floating, if you will, in low-earth orbit by yourself, managing that, it's both exhilarating, and at the same time, there's some anxiety associated with, "I hope I don't screw this up because there are a lot of people watching at this point, and they're going to let me remember it for the rest of my career."

ZIERLER: Physically, are you hot or cold? Or is it just the right temperature?

BEHNKEN: Inside the space suit, it's a little bit akin to either doing winter camping, hiking, or snow-shoeing. You need to figure out the rate that you can manage yourself so that you don't overheat or overcool. You don't want to get too cold because then, you can start getting things like condensation in the helmet, which makes it hard to see, and that's not good. You really do have to stay ahead of the cooling that you can manage on your suit. You either need to adjust it or change your work output, move faster or slower, to keep the suit in a happy state. That's true for temperature as well as carbon dioxide. I'm on the bigger side as far as astronauts who fit in the suit and generate carbon dioxide. I can generate my share, and then some extra.

You need to manage that as well. I'll get to why this is a nice thing sometimes in a minute, but you need to pace yourself so that you don't over-breathe the space suit, if you will. It can scrub out carbon dioxide at a specific rate, and if you're working too hard, you make too much carbon dioxide, you can get yourself in a case where it starts to degrade the performance of that overall system, which means your spacewalk will be shorter, which is no fun for anybody. But at the same time, it could be life-threatening for somebody if you were far away from the airlock and had messed up your CO2-scrubbing capability. On some of my subsequent missions doing the spacewalk, we had a little bit more time for several reasons. On one of my flights, the second flight, we actually took a module to the Space Station that required a lot of outfitting. It had to come out of the Space Shuttle payload bay, immediately get installed, then the spacewalk had to connect a power and some keep-alive things to that new module that was being installed.

The trick was, they needed us at the beginning of the robotic operation to move the module to Space Station, and they needed us at the end, moving the module to the Space Station to get it connected up. That meant our spacewalk had to last long enough to be able to cover both ends of that, which meant if we worked super hard in the middle of it, we might not have enough carbon dioxide-scrubbing capability to stay out there. On that mission, I did have the luxury a couple times of being able to tether myself up. We have what we call a ball stack. It's one of those camera-grippers you can wrap around a pole, and it's a string that's got a series of balls in it that you can kind of adjust, and it's still a little bit rigid.

You can attach yourself with this third arm, if you will, and cinch it down so you're just floating out there and not have to move, take a chance to relax, watch the earth go by, watch the clouds move at a different speed, different cloud levels moving at different speeds. It's pretty mesmerizing when you look down on it on the earth. If you're lucky, there'll be a series of thunderstorms you can watch kind of dance through the sunrise and sunset, which is always cool. I had a couple of opportunities to just sit and watch, and that was your job because you were preserving your carbon dioxide-scrubbing capability, which is a luxury that not every space-walker gets, and I cherished the time I was able to do that on my second Shuttle flight because we had to do it.

ZIERLER: In what ways was the second Shuttle flight, Endeavor STS-130 in 2010, different from the first one?

BEHNKEN: The first one, I think, you don't know what you don't know. You're super prepared for a bunch of things that end up being easier, if you're lucky, than you expected. But you definitely put a lot of focus on doing things, and you probably over-prepare in a lot of areas. It turns out once you know what you know, you might have a different perspective in terms of how many times you might want to train something or how prepared versus figure-it-out-when-you-get-there you want to be. For my second mission, it was a much more relaxed pace. The first mission I did had two big payloads that had to get installed, both requiring a significant amount of space-walking. We also did a tile repair objective, which was to protect the Hubble servicing mission that was going to go up.

After Columbia, and we had that damage to the leading edge and lost the orbiter, we developed a space-walking technique for being able to go out and repair part of the heat shield. As part of that first mission, we added, at the last minute, some space-walking activities to demonstrate that you could do those things. We had to do it, we had to go out and spackle up some damaged tile or heat shield material, then have them bring it back and test it to make sure that the space-walking techniques were reliable, that what we had done would get a vehicle back through entry or understand in what cases it would and wouldn't. That mission had five spacewalks. It was the longest dock to Space Station at the time. It was super busy, and we had this disparity of all these different space-walking things we were doing. For my second mission, we had two space-walkers, the mission was shorter, and it was just a simpler pace because I knew much more about what I already knew to kind of help in that respect as well.

Those two missions were very different. My third mission was a completely different flavor, which was very much a developmental mission to test out a new spaceship, so that made it completely different. Then, just a few months prior to launch, they decided we were going to stay a longer duration on Space Stations. Instead of going for a week or two, like we thought, we were going to stay for a few months and do some spacewalk maintenance on Space Station that it required to try to buy down some time to allow another vehicle to come home and get off of the Space Station if I was able to help Chris Cassidy to get the spacewalks down. That one was just crazy in a different way. The first one was crazy because of the different stuff we were doing, and we were packing in everything we knew how to do in a really small amount of space.

My second mission was a more relaxed space, we kind of knew what we were going to go off and do, and we did it. The third mission was one that just kept changing. "What are we doing?" "I don't know, we'll find out when we get up in the morning." [Laugh] That was exciting and rewarding, and folks had to have confidence that you were going to adapt and figure out a way to cover whatever mission needed to be done on the given day.

ZIERLER: What did it mean to you when, in 2011, NASA ended its Space Shuttle program?

BEHNKEN: In 2011, it meant a couple of things, as we went to wrap up the Space Shuttle program. When I had arrived at NASA, we only talked about working in low-earth orbit. We only talked about building Space Station. We didn't talk about further out destinations. That changed when we lost Columbia. We talked about retiring the Shuttle, returning to the moon, going further out, maybe reinvigorating human spaceflight to some extent. 2011 rolled around, and we didn't have our system for going to the moon, we didn't have a new system for going to the Space Station, but we were retiring our Space Shuttles. It was a little bit disconcerting, of course, to be at the end, to retire your last spaceship. You don't have any more spaceships, and you're an astronaut.

That, by definition, could mean that you're not an astronaut. It was a little bit disconcerting. I went to all three of the final Shuttle missions and did something you normally don't do. I went down for a landing. Typically, people go for the launch. You don't hear a lot about people heading down, in the Space Shuttle days, to watch a Space Shuttle return. It was something people might do from happenstance, but I wanted to see it because it was potentially going to be the last time you could see something like that. I was serving as the Deputy Chief of the Astronaut Office, or in a branch chief role, kind of working towards that around that time and took over as NASA's Chief Astronaut in 2012. As the Chief Astronaut, when the US had this many spaceships, zero, I took it as kind of a responsibility to get as many of the astronauts as I had over to Kazakhstan.

We had astronauts who came in who hadn't seen the launch. I wanted them to be able to be a part of seeing what human spaceflight was because I knew when we started launching again off the Florida coast, they would really relish it once they all understood what it was like to be a part of going to Kazakhstan and launching on the Soyuz with our Russian colleagues. It was an interesting leadership position to be in, to be a part of developing the new spacecraft, but at the same time, keeping the energy going so that everyone had an appreciation for the mission in front of us, which was operating Space Station, providing crews via Soyuz, at the same time as we developed these new vehicles. It was a challenging time, but it was very rewarding, and I wouldn't exchange the experience. Somebody asked me at one point recently–we were talking about support roles, so it was a little bit of a different conversation, but I was able to reflect and pull out some old pictures of me actually in Kazakhstan as the Chief Astronaut, carrying Chris Cassidy's rocking chair.

They carry you in a rocking chair from the Soyuz to the medical tent you go to after your landing. I was in the support role with him as that. Probably two years later, Chris took over as the Chief Astronaut, so he had to carry somebody else's rocking chairs for a while. Then, a couple years later, he and I were on Space Station, doing our tenth spacewalk together. Interesting how our roles ended up reversing and swapping around. Sometimes, what people see as the astronaut, the person launching into space or living on Space Station, we have a wide spectrum of roles that make the mission possible.

ZIERLER: A question on sequencing. Did you understand NASA's decision to end the Space Shuttle program as an end of a chapter, or was it simply a transition on the way to what became the commercial crew program?

BEHNKEN: From my perspective, it was the end of a chapter. The real mission of the Space Shuttle and what it was good at was hauling a lot of stuff into space and assembling the Space Station. The primary assembly sequence was finished for the Space Shuttle program. At the same time, the Space Shuttle was old technology, and there was risk associated with continuing to operate it. For me, from a human spaceflight program US perspective, it was kind of the end of a chapter, and we picked up with the new chapter. Assembly of Space Station is kind of complete. There's a little bit more assembly, there were some modules that were able to come up on the Russian side. Then, we transitioned to a phase of really utilizing the International Space Station. Then, there's this next phase, which is commercialization, which is creation of the Dragon capsule, the Starliner capsule, from a low-earth orbit perspective. At the same time, we're opening a new chapter in a different book maybe that's further out, and after closing the chapter on Apollo, it's the next chapter after Apollo, as we try to head back towards the moon. A new book hopefully will start pretty soon about migrating onto Mars.

ZIERLER: Tell me about your early impressions of SpaceX and if you ever had the chance to interact with Elon Musk.

BEHNKEN: It's interesting because people ask about my impressions of SpaceX, and I'll say that it was an evolution. If you asked me about early SpaceX, I would give you a different answer then, as we migrated our way towards our first flight, and maybe where they are now, as they start to operate in a more routine fashion. And that's been true on their boosters as well, as things became more routine or regular, on a regular schedule, if you will, versus just trying to get something accomplished, which is a different place. When we arrived and started working with SpaceX, there was often a challenge to figure out, "How does the schedule for what SpaceX is trying to accomplish match up to what we predict it will be or allow us some semblance of matching up with what we need to do, which is know when we need to have a crew ready to launch on something different than a Soyuz?"

This is happening at the same time that SpaceX is trying to learn a lot and take risk in terms of the engineering or science endeavors they're focused on. But at some point, you have to flip the bit and say, "Failure's no longer an option because we put humans on board. You can do your engineering tests. Let's all get on the same page that this one's going to take risk, and we're not going to know everything, and if it blows up, that's OK. We're going to flip the bit and transition over to human spaceflight, and we're going to do that with 100% success as our goal. Failure isn't something we're going to entertain as part of the plan." When I first started working with them, it was almost all that, "Hey, we need to learn and go fast. We're going to break some things and move forward from that." We saw them lose CRS-7, which was a cargo resupply vehicle to the Space Station. From an astronaut perspective, what I took away from it was that we'd signed up to flying with them with humans, and this was their first major mishap with one of their capsules.

We lost an EMU, which is the space suit we do the spacewalks in, which was a high-dollar asset, but it was a space suit. But it's an emotional thing because there are only a handful of those space suits, less than 20 for sure, and they lost one. And folks consider, when they put cargo on vehicles, particularly for first flight, you put cargo you can lose. And that's why it was on CRS-7. There was not a space suit on CRS-1. We were migrating towards the cargo that we loved a little bit more than we were in the early days. But I saw that team kind of take that as an emotional hit and say, "Hey, we lost this vehicle, and we're under contract to start flying humans. We need to redouble our efforts and have a healthy dose of paranoia associated with our engineering development effort in addition to our audacity." This is a conversation I've had when I've brought it up with Elon or when we've talked with him in general.

We went through that process. A few years later, SpaceX lost a launchpad down in Florida, which was a pretty significant event because they were much further down the pathway and closer to flying humans, and that was an emotional event for them, but it was a step on that pathway. It was those experiences, having been somebody who saw Challenger, somebody who was on the runway for Columbia when that Space Shuttle didn't come back, I think I had a very healthy appreciation that spaceflight is dangerous and unforgiving, and the consequences are real, in a way that maybe that team, not having ever lived it, didn't necessarily have. Seeing them in the days before those events and the days after those events, how they dealt with them, kind of allowed me to see them go from that seat-of-your-pants, "We can take risk, go fast, and figure it out," perspective to having that paranoia, to the audacity that is SpaceX. It's tempering and creating a balance, if you will.

These are hard things, and you have to have confidence when you go off and do them, but you also have to be worried that you don't know everything at the same time. Being confident but paranoid is a tricky balance. I saw them make that transition as we moved toward spaceflight. I'll honestly say, on the NASA side, we probably moved more towards the audacious side in terms of working with them going forward versus complete risk avoidance.

ZIERLER: Coming to 2015, in comparing your experiences flying with SpaceX versus NASA, is it apples to apples? Or is it really apples to oranges because the missions and organizations are so different?

BEHNKEN: I think maybe it was apples and oranges, and now we have a smoothie, so we've brought the two things together, to some extent. And that was really the only way we were going to get there from here, if you will. Because we do have to take the Dragon capsule to the Space Station, and the Space Station has to accept people who are arriving and coming aboard, but that resource, that infrastructure that's in place, is super high-value and of international significance. It's that balance I described before of, "You have to have the confidence and say that you're going to go off and do it, but you have realize that you're a piece in a giant puzzle and figure out how to fit in at the same time. You don't control Space Station despite"–and SpaceX is a company that very much has been successful by controlling its play space, if you will, of how they were going to operate, what their suits would look like, making their launchpad look different than the other launchpads, creating a Silicon Valley sort of work environment inside of an aerospace company. They've been in control and been unique, but at the same time, that's great, but we needed to fit it into the puzzle that was the International Space Station Program and all the international partners that go along with it. And we've managed to do that.

ZIERLER: To broaden the lens a little bit, in what ways has SpaceX provided a service that has allowed NASA to branch out into new endeavors that might not have been possible otherwise?

BEHNKEN: I think continuing to operate the Space Shuttle for NASA was going to be a challenge. And frankly, continuing to operate at the International Space Station is a challenge. It's a huge facility. Managing the schedule for all the international vehicles that arrive–the progress vehicles from Russia, we went through a phase with the ATVs, the autonomous vehicles from the European side, the cargo transfer vehicles from the Japanese side, managing all of that infrastructure for the Space Station is still a challenge. Doing it as we continue to operate with the Space Shuttle, with the infrastructure at Kennedy, the multiple buildings, the engineering workforce, the contracts that go forward with that, was a burden as we tried to go forward. And we frankly didn't need the capability anymore. I described before that Space Station was built, the lion's share of the assembly sequence was complete, and we needed to rotate crews.

Doing that with Space Shuttles is not an efficient way to do it. Space Shuttle's big. It takes a lot of fuel to get it into orbit, a lot of maintenance to kind of get the vehicle turned and do it again, and it was beyond the scope of what we could afford to do simultaneously. We needed a small capsule to go off and do this, and they invented a commercial crew program that tried to get Boeing and SpaceX to both create vehicles. The intent was that, in addition to NASA being a customer, there would be other customers for those vehicles as well. Inspiration4 has flown at this point, there is an Endeavor with a company called Axiom that's planning to take a SpaceX vehicle, fly it to the International Space Station, dock for a few days, then come home. That's potentially two flights, and I know that there's a lot more on the manifest coming forward.

But to have that quick turn from, "Here we are with the Crew 3 vehicle and the Crew 3 crew on board," that means four NASA missions have flown, and we're going to fly our second commercial mission, which means a third of the missions now flying on that vehicle are not NASA missions. That leverage, if you will, to kind of keep the infrastructure churning forward so that you have your opportunities to fly, but at the same time, you don't pay all the development costs, you don't pay for the refurbishment costs, you don't pay for the facilities completely dedicated to you has created this opportunity to much more cheaply get into space. Reusing the boosters is another huge factor as well, so that first stage comes back and is ready to go again so quickly. It makes a huge difference. What we've been able to accomplish with a commercial crew is this leveraging, if you will, of another marketplace. There was an idea a long time ago that NASA, with the Space Shuttles, would launch both DOD's payloads and do science missions as well.

You'd fly both, marry those missions together. There'd be synergy, it'd be cheaper for everybody. But then, we realized that if you had a hiccup, and you couldn't launch satellites anymore because you didn't want to put human life at risk, you've completely shut down the whole process. This is a different model, where we can leverage the same hardware, and we don't have the humans involved, except for when we need to have the humans involved. They can launch boosters, reuse those boosters, build another booster, all with the same manufacturing infrastructure that we use for the human spaceflight side, and that just multiplies what our capability is because that investment and the support infrastructure is not something that has to all be on the burden of human spaceflight. NASA has been able to transition and focus on a different mission, which is going back to the moon or building a vehicle, consider landers, rovers, space suits, and push in that direction as well.

But going forward with each of those missions, the same question comes back up of, it's not going to help us if we build a moon base, and we do that where NASA and the US government have to invest in all the infrastructure to make it possible and foot that bill on the order of billions of dollars per mission, meaning you can only do a couple of them per year, doesn't provide you any economy of scale and otherwise. That concept of thinking as to, "How do we get as many users of our infrastructure in place that aren't all us so that we can share the cost?" is really what we've gotten out of commercial crew and what has manifested itself with the government. And I want to give more credit than just NASA. The overall government's investment in working with SpaceX to try to push for that reusable booster or create an alternative or multiple capabilities for getting into low-earth orbit.

ZIERLER: Coming to May 2020, along with Douglas Hurley, when you went to space on SpaceX's Crew Dragon Endeavor program, what did it mean for you, for NASA, even for the United States to be one of two Americans to launch to space from American soil, on an American-made rocket in nearly a decade? How important was that?

BEHNKEN: For me as an individual who had led the Astronaut Office through a chunk of time when we had no capability to launch our own crews into space, it was personally rewarding to be a part of the team that was able to accomplish it again. I had kind of certainly a sense of personal satisfaction to be a part of that. At the same time, I think I was also kind of daunted a little bit with the responsibility that goes along with that. And thankful that our nation was willing to invest again in that capability. As somebody who was motivated, as I described earlier, with what NASA had done for exploration and had followed so keenly, even when we lost a Space Shuttle, and then dedicated my career and was risking my life to kind of continue in those footsteps and in that endeavor, I was thankful that we were able to invest, and focus, and successfully go and accomplish that. I was also, in some sense, disappointed that not more people could come to Florida and live that experience in person.

Having seen so many Shuttle launches and returns, it was truly rewarding to see humans ride on the end of those rockets into space. I don't know if you personally have seen a rocket launch or then seen a rocket launch with humans on board. For me, it's always a different experience to appreciate and realize that there are humans on board. When you watch it, it's just got a different perspective, and I have a different feeling in the pit of my stomach as I watch it actually go off and get accomplished. I was a little bit disappointed that not as many people were able to see our mission launch again with humans on board.

But at the same time, with the pandemic and how virtual the world had become, I think we reached a much wider audience just based on the state of where we were as a nation and a world when it actually happened. I guess I'm proud, happy, thrilled, and thankful is the best way to describe it. There are a lot of deserving people who could've been a part of that and a lot of people who would've been qualified to go off and do it. But I'm proud to have been a part of it, and I'm glad that we did it as a nation.

ZIERLER: What was the work at that time when you joined Expedition 63? What was the mission?

BEHNKEN: The mission for Doug and I on Expedition 63 was really focused on accomplishing a series of spacewalks that were needed to upgrade the power system on the International Space Station. When I arrived, I mentioned earlier that our mission had evolved. At one point, we had been told we would do seven to ten days, we'd accomplished the test objectives associated with the Dragon capsule, get it to Station, make sure people would do the engineering analysis during our flight as it continued. We'd launch, check out the thruster system, approach Space Station in a careful, controlled manner, and they would look at the data, then we would get docked, they would leave us there, watch to make sure the systems were performed, then we'd bring it home and go through the entry process in a very similar fashion, then get recovered and check off those boxes that you could actually do this with this vehicle.

But at some point, some folks looked and said, "Hey, these spacewalks need doing, and Doug, Bob, and Chris can accomplish this mission as well." We didn't know how long it would be before the next SpaceX vehicle would be able to launch. We had never launched two SpaceX vehicles, and folks were a little bit iffy about what is the possibility, what is the schedule like, and what state will Space Station be in if we don't get this work done? When I got on the Space Station, Chris, the commander on the station and the guy we were going to do the spacewalks with, asked me, "How long are you guys staying?" And I said, "As long as it takes to get these spacewalks done, as long as it takes to get the work done." Because he was the only US crew member on board the Space Station at the time, so there were things he couldn't do by himself, and Doug and I were there to get things done. Once all that work was done, they were probably going to bring us home.

My prediction at the time was that we would finish the space walks around my birthday, which was July 28, and what I would get for my birthday was a plan to come home and a weather report that said it was a good time to go do that. Lo and behold, I was lucky, and that's what happened. We did those four spacewalks. They'd originally talked that it might be seven spacewalks we'd have to do. Chris and I are pretty experienced and were able to move at a pace that was well above what they had expected and got done almost in three. Had a little bit of cleanup that we needed to go off and do. They had some other work that they were happy to have us go off and execute, so we went out a fourth time and were easily done before my birthday.

ZIERLER: After coming home, what was it like as a spectator, looking at the Crew 2 mission, to have, of all people, your wife, Dr. Megan McArthur, be a part of that mission?

BEHNKEN: It was really special for me to watch my wife launch and kind of go through the role reversal, if you will, of her headed to Space Station. She flew on the same capsule that I flew on, the Endeavor Dragon capsule again. She flew in the same seat position. I think she might have had a little bit different size, so she may have had a different leg length or seat pan, but she flew in my spot and put her sticker for her mission next to the sticker that Doug and I had installed while we were on orbit to kind of christen the vehicle as the Demo 2 vehicle. That was pretty rewarding. We have a 7-year-old son, and so I was Mr. Mom through that almost seven-month period while she was on board the International Space Station.

It was interesting because I think having lived and had the same experience, particularly so close together, there were a lot of things we just didn't have to say. She'd start a sentence, and I'd be like, "Yeah, this is at that location," or, "Try it this way," or, "I know exactly what you mean. They did the same thing to us when we tried to do that activity on board the Space Station." It was both rewarding but also comforting because our experiences were so similar and commiserate if you will because they were so close together.

ZIERLER: At that point, just as a matter of sequencing, are you already at Johnson Space Center? Or that only came after the mission?

BEHNKEN: No, we landed near Pensacola, Florida, and I had traveled back to Houston straight away, so maybe six hours or so later, I was back in Houston. When Megan launched, she went to Space Station and got docked, then we traveled back to Houston. I was in Houston for the next six or seven months, and then all the way through splashdown, I was at home with my son. We watched on a computer system her return, and then we met her late that night at the airport and got to go aboard the airplane and have a little bit of a reunification privately before she came off the plane and greeted the managers and support folks.

ZIERLER: Was that her first mission in space?

BEHNKEN: It was not. It was her first mission to the Space Station. Previously, she had headed to the Hubble Space Telescope and been a part of the crew that had done the final servicing mission for the Hubble Space Telescope back in 2009, which was a really cool experience for her, and I think she is in a little bit of a discussion with the space-walking team because the space-walkers described themselves as the last people to touch Hubble, but she was actually the person who operated the robotic arm, pulled it out of the Shuttle payload bay, and released it into free space. It was her hands on the controls of the robotic system that sent that telescope on its way, not the gloved hand of the person who gave it a pat-pat before they came inside while it was still attached to the Space Shuttle.

She did that servicing mission, and interestingly, for part of the time, I was on a rescue crew. Just by virtue of having lost a Shuttle previously, NASA had a plan to launch a second Space Shuttle and rendezvous if there was a problem with that orbiter, Atlantis. It was Endeavor that was going to go and rescue Atlantis. I was trained and preparing to go and do that rescue mission because I was the most current crew. My crew from STS-123 were the ones on the hook in late 2008. It turned out there was a mission delay, and another couple missions flew in between, so they had a different rescue crew when they actually flew. But that was an interesting part of our life experience as well.

ZIERLER: And just to bring our conversation right up to the present, what have you been working on in the past year or so since the end of these missions?

BEHNKEN: At the end of your mission, particularly a long-duration flight to the Space Station–and even though it was just over two months, it's long in terms of your body adapting to the space environment and has to readapt when you get back, even after just two months. I had about six months where I was focused on that, and in that time period, my wife was working towards her launch as well. To allow her to focus, it was good for me to have some schedule flexibility, working through that. After that, I picked up some responsibilities supporting Commercial Low Earth Orbit development, which is how we can utilize Space Station to introduce more commercial partners. I supported some of those efforts. That includes this Axiom mission that's headed to Space Station here in a few months with the commercial crew that's going to fly on Dragon but with no NASA crew members.

At the same time, there are some other payloads that are commercial in nature. After that, I picked up as the Acting Director of Flight Operations at the Johnson Space Center, which means the flight directors and flight controllers in the Astronaut Office report to my boss, but I'm the deputy for that whole organization. I used to be the Chief of the Astronaut Office, but now the Astronaut Office reports to the next level up that I'm a part of. And that's where I'm at right now. I've been doing it for going on five months now.

ZIERLER: To round out our conversation, a few questions looking to the future. Right now, with so much difficulty relating to science and trust in society, albeit from vaccines to climate change, because you're so devoted to public engagement and demonstrating the Inspiration at NASA, what role do you see in terms of showing how important it is to effectively communicate science to the broader public?

BEHNKEN: It's an interesting question, and I think it's one that we all, as scientists and engineers, have to figure out a way to take ownership of. I think many of us maybe gravitated towards science and engineering because we may have shied away from public speaking or some other career that may have required more communication skills. If we found things we felt were hard to understand, once we understood those, we sometimes used them as a crutch that they're hard topics. Everybody maybe doesn't need to understand them. We can kind of focus on that. But flipping that around a little bit and taking some responsibility to try to take ownership of communicating the science, engineering, or discoveries that are made is a responsibility we need to embrace and probably really try to push from an education and experience perspective.

We all have had experiences that may make us shy away from careers like sales or otherwise, where we view maybe tricking somebody as part of the process versus really fundamentally, the facts being the facts and decisions being based on those facts as part of that role. And I think that we have, in some sense, maybe done a disservice as a whole by shying away from some of that communications responsibility. I'm not saying that it's easy, and I understand why we shy away from it. But that responsibility is one we have to take along with understanding things and pushing the scientific community forward, pushing those boundaries of our understanding forward. Being able to explain it and communicate it is a critical portion of that.

Because in our experience, we know that facts dictate the outcome. We collect the data, we sample it, we lay it out, and we know what the future will hold based on those facts. There might be a probability associated with it, and we may argue about the assumptions that go into it, and that's a healthy part of that process, but taking ownership of that communication is something I hope we can all do better with.

ZIERLER: For young people today who are interested in a career in space science, or maybe even becoming astronauts themselves, reflecting on your own experiences and background, coming of age when obviously NASA was the only game in town, would you recommend a similar career trajectory as the one you've taken? Or is the situation so different right now that it's really difficult to extrapolate?

BEHNKEN: I would say that there are things I did to kind of keep the options open. What those things are might be slightly different. But really, I wouldn't recommend, "The only path is to go into the military, try to go to Test Pilot School, get a scholarship from ROTC, then you'll be an astronaut." That's not what I would recommend to folks. If nothing had changed, I wouldn't recommend that. What I would recommend is kind of a strategy or posture of considering the future in the decisions that you make and trying to keep opportunities open. And I described this a little bit earlier, that if I had an opportunity to do something like go to Test Pilot School, and I closed that door, that might reduce my opportunity.

I don't think working at an aerospace company reduces your opportunity for flying in space maybe the same way for everybody as it would for me because I was already in the military at the time, I was already on a pathway where getting to Test Pilot School was a matter of 15 months, not a matter of enlisting or getting a college education and then starting a military career, working that direction. When I made those decisions to keep options open, the options that I kept open were ones that made sense based on the trajectory I was on. This most recent class of astronauts has a SpaceX person in that class being hired on the NASA front as an astronaut. It's not the first time we've brought folks in from commercial companies to be members of the NASA astronaut corps.

If you want to fly in space, become a billionaire. That'll be a solution. That's not new. You could do that with the Soyuz. Dennis Tito, there's some history with the Space Station of folks being able to buy their way into the flight opportunity. But for people who don't magically turn out to have the financial means to purchase their way into the situation, I think there are lots of opportunities going forward, and the underlying suggestion that I would have for them would be to keep your options and opportunities open as you go forward.

ZIERLER: Last question, looking to the future. In light of all you've accomplished, what's left for you? What are the frontiers in your research and career?

BEHNKEN: That's a good question. Of course, I would love to fly to the moon, I would love to go to Mars. I do get asked because we sometimes have the questions about going further out, "Are you OK with a one-way trip?" For me, I don't think that's a good pathway. [Laugh] Just like when Kennedy made his famous speech, the part about launching someone to the moon and then returning them safely, that was a key part of both the engineering challenge, the technical challenge, but also really what we need to accomplish the overall Endeavor. We're not at launching people one-way into space yet. We should have a destination for where they should be going. But on a more serious note, I do think that I have contributions I can make.

If I can't be the person who heads off to the moon, then somebody else can, and I can contribute and share that experience. And I did describe earlier that, as a community, trying to motivate folks, whether it's other astronauts or scientists, to take ownership of communicating the facts and data that go along with what it is we do, or can predict, or expect to come in the future is kind of a critical part that I feel strongly I want to be a part of going forward. It's not just, "Hey, let's go to the moon." Let's go to the moon with a purpose. And that purpose could be manifold. It could be for a scientific endeavor. It could be to open up commercial opportunities. Let's get on the same page and communicate what those objectives are, then make that solution happen. That's the part that I'm passionate about, picking your target and creating the pathway to get there.

ZIERLER: Well, Bob, this has been a phenomenal conversation. I'm so deeply grateful that we were able to do this. There's so much pride in what you've been able to accomplish and what you represent at Caltech, so I'm so happy for this. Thank you so much.

BEHNKEN: Thank you very much.