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David Klaus has built a career centered around the science and engineering of human spaceflight as a systems engineer, researcher and educator. After four decades on the leading edge, he is embarking on his next challenge: retirement.��

“I’ve been lucky,” said Klaus, a professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences. “I’ve had a really fun career. If you’d asked me 40 years ago what I wanted to do with my life, I would have had no idea, but looking back now, it's easy to see how the dots connected.”

Klaus has supported Space Shuttle launches, played an active role in dozens of research studies that have flown in orbit, worked on designs for future space habitats, crafted curriculum for undergraduate and graduate students, guided federal regulations, and nearly became an astronaut himself.

An impressive list of accomplishments for someone who originally did not see himself spending a career in aerospace.

Growing Up

“Space wasn’t something that was talked much about when I was growing up in West Virginia. Watching the Moon landings as a child, the astronauts were like superheroes to me. How do you do that kind of work? I had no idea,” Klaus said.

After high school, he earned an undergraduate degree in mechanical engineering from West Virginia University and, upon graduation, faced every young engineer’s dream: multiple job offers – he successfully interviewed at Pratt and Whitney, Texas Instruments, and NASA Kennedy Space Center.

He chose NASA.

“I honestly hadn’t thought about opportunities in aerospace, but the possibility that I could work in a program launching people into space? You can’t turn that down,” Klaus said.

Life at NASA

He worked with life support systems in shuttle launch control and before long, had transitioned to Vandenberg Air Force Base and then Johnson Space Center, in Houston, Texas. Klaus’s job in spacesuit testing and spacewalk operations had an almost perfect crossover with some of his hobbies.

“I had my pilot’s license and was a scuba diver, so I got to get in the neutral buoyancy laboratory, the pool—where the astronauts train—with them,” he said.

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In 1990, he came to ɫ��Ƶ���� with an eye toward a master’s degree. The aerospace department’s��BioServe Space Technologies��was researching biological life support systems, which Klaus saw as an important advance from the traditional physical and chemical technologies used on the space shuttle.��

Klaus’s prior experience at NASA became invaluable for the upcoming BioServe payload activities. His background at both Kennedy and Johnson Space Centers meant he was intimately familiar with mission operations and crew procedures.

“I came for the master’s, but the research became really interesting. I got much more into how spaceflight affects microbes and continued on to a PhD. I did my thesis on how bacteria respond to spaceflight. At that time, there were maybe a couple dozen papers on the topic,” Klaus said.

After completing his PhD and a year-long Fulbright Postdoctoral fellowship at the DLR Institute of Aerospace Medicine in Germany, Klaus suddenly found himself without a job offer, the exact opposite of the situation after his bachelor’s degree.

“I was applying for jobs from Germany, but I never got any responses. BioServe said they needed help with some upcoming flights and would I return? My plan at that point was to only hang out in Boulder for a few months while I figured things out,” Klaus said.

Designing Courses

His “few months” in Boulder quickly became a more permanent chance to conduct space life science research and craft what would become the department's bioastronautics curriculum.

“I developed my first class, space life sciences, in 1993 while I was still a PhD student. Human space vehicles were for me at the time mostly focused on the life support hardware – HVAC systems, pumps, and fans. Eventually I became more aware of the human-centered aspects, that’s how I’ve developed the curriculum here. We start with a human in mind and then move on to what is needed to keep them alive and healthy in space,” Klaus said.

In 2002, Klaus became a tenure-track professor within the aerospace department, cementing his leadership role in growing bioastronautics research and education at the university.

“We’re helping students find their place in the world. I love seeing where they go. They’re the real product of the university; our research is important, but the students are the most significant outcome, in my opinion,” Klaus said.

Across his time at ɫ��Ƶ����, Klaus has directly advised 24 PhD students and served on another 30 PhD committees, in addition to teaching thousands of undergraduate and graduate students.

Astronaut Finalist

Klaus twice applied to the NASA astronaut program, both times making it through successive rounds of applicant winnowing and being brought in for NASA’s intense multi-day in-person interview process.

“It’s mostly medical testing, like having a weeklong physical,” Klaus said. “They check everything. Do you have two kidneys? You think you do, but I know I do. NASA checked.”

The culmination is an hourlong meeting with a panel of NASA administrators and astronauts.

“You write an essay that they read aloud to the group, then they sit you down and say, ‘Tell us about yourself. Start with high school.’ I was kind of lucky because I knew a lot of the crew. It could be an intimidating experience if you’d never been there before,” Klaus said.

In both cases, Klaus made it to the last group of around 40 finalists for roughly 15 astronaut slots. Unfortunately, he was not selected.

“The first time was a real letdown, but the second time, my oldest son was born the day before I got the call and having a kid changes your perspective on life and risk taking,” Klaus said.

Recent Research

As a faculty member, Klaus’s recent work has included leading the last four years of a Federal Aviation Administration Center of Excellence for Commercial Space Transportation. The seven-university initiative evaluated how the FAA could meet the needs of the growing space sector.

“It really helped the agency extend itself from an aircraft-centered organization into spaceflight, as the FAA must increasingly deal with both vertical and horizontal traffic. The Center helped them broaden their way of operating into multiple flight domains,” he said.

Although Klaus has graduated his last PhD student and will no longer be teaching, he is still working on several research papers related to his time as deputy director of the��NASA SmartHab Space Technology Research Institute, which ended in 2024. The effort, called HOME, focused on assessing autonomous or ‘smart’ technologies needed for future space habitats on the Moon or Mars.

“When something breaks in low Earth orbit, you can launch up a new part. That’s not an option for a base on Mars. You need to rely on processes like additive manufacturing, 3D printing, so we’re creating the means to integrate those technologies into the habitat. It’s been a cool way to wrap up my career, looking back at things I learned on the Space Shuttle and what worked for it and now determining other areas where we need new possibilities for deep space operations,” Klaus said.

After his retirement in May, Klaus and his wife are planning to travel, but he is also looking forward to no longer having a need for a daily alarm clock.

“I need a little decompression time,” Klaus said. “I want to be bored for a little bit, to take a breath and reprioritize my days.”

In recognition of Klaus’s contributions to the university, aerospace faculty voted this spring to bestow ��him with the title emeritus professor. The distinction recognizes his record of exceptional service and allows him the opportunity to continue research on campus, should he decide retirement can wait a bit longer.