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Tap into the experiences of NASA’s technical workforce as they develop missions to explore distant worlds—from the Moon to Mars, from Titan to Psyche. Learn how they advance technology to make aviation on Earth faster, quieter and more fuel efficient. Each biweekly episode celebrates program and project managers, engineers, scientists and thought leaders working on multiple fronts to advance aeronautics and space exploration in a bold new era of discovery. New episodes are released bi-weekly on Wednesdays. 

NASA Langley Research Center Retired Chief Scientist Dennis Bushnell discusses highlights of his 60-year NASA career and the future of the agency.

When NASA employees retire from the agency, they may leave behind critical knowledge gaps for their teams and missions. Anticipated change in the agency’s workforce demographics due to attrition through retirement of the most experienced personnel — many of whom cannot easily be replaced — presents a serious knowledge retention challenge for NASA. The challenge of knowledge capture and transfer is especially pressing as knowledge loss and insufficient expertise can present risks to projects and mission success.

In this episode of Small Steps, Giant Leaps, you’ll learn about:

  • Ways to capture and transfer rich experiences of longtime NASA employees
  • Balancing creativity and perseverance with real-world metrics
  • Why mavericks are essential to success


Related Resources

Knowledge Capture and Transfer

Ensuring Knowledge Continuity during Employee Transitions

Video: Stories of Apollo: Dennis Bushnell

Societal Futures to Inform Space and Aero Planning: A Technological Projection

Commercial Crew Program

NASA Lessons Learned Information System

APPEL Courses:

Pay It Forward: Capturing, Sharing and Learning NASA Lessons (APPEL-vPIF)

Creativity and Innovation (APPEL-vC&I)

Foundations of Aerospace at NASA (APPEL-vFOU)


Dennis Bushnell Photo Credit: NASA

Dennis Bushnell
Photo Credit: NASA

Dennis Bushnell served as NASA Langley Research Center Chief Scientist the past 23 years before retiring from NASA in June 2023. Bushnell was responsible for technical oversight and advanced program formulation. He has more than 60 years’ experience as a research scientist, section head, branch head, associate division chief, and chief scientist. His technical specialties include flow modeling and control across the speed range, advanced configuration aeronautics, aeronautical facilities, advanced power and energy, planetary exploration, and hypersonic airbreathing propulsion. Bushnell holds 15 patents and is the author of 300 publications/major presentations as well as reviewer for 40 journals and organizations. He has a bachelor’s in mechanical engineering from the University of Connecticut and a master’s in mechanical engineering from the University of Virginia.


Dennis Bushnell: You can’t be too married to one idea. You have to be enough of a person with enough perseverance, a monomaniac with a mission if you will, with raw peasant toughness to carry something forward. But you also have to realistically analyze it in terms of the real-world metrics.

We got too much married to success versus looking in more detail. And so, a lesson learned that hopefully we’ve learned — we keep saying we’ve learned it — is to question everything.

As I sit here on my last day of 60 years, what I’m thinking about is the future of the agency.

Deana Nunley (Host): Welcome to Small Steps, Giant Leaps, a NASA APPEL Knowledge Services podcast where we tap into project experiences to share best practices, lessons learned and novel ideas.

I’m Deana Nunley.

Organizations put a lot of emphasis on capturing knowledge before it walks out the door. Knowledge capture and transfer are integral to achieving NASA’s goals, and agency teams do well when they establish a culture that supports continually sharing and advancing knowledge.

NASA Langley Research Center Chief Scientist Dennis Bushnell retired from NASA June 30 after more than 60 years with the agency. Our APPEL Knowledge Services team had the privilege of catching up with him that day during his final hour with the agency.

Here’s our conversation.

Host: Dennis, thank you so much for joining us today. Sixty years of experience at NASA. It’s hard to know where to start this conversation. What’s top of mind for you today as you retire from the agency?

Bushnell: The fact that I’ve been in NASA, especially since the beginning. I had an experiment on the third Gemini Titan shot in ’65 and worked Apollo, worked shuttle, worked most of what NASA has worked and a lot of things that other people have worked over these 60 years.

NASA was set up in ’58 to commercialize space and to enable humans in space. And NASA has just about done that now. So, the issue that is, what’s happened since NASA was commissioned to do these missions? And the answer is space is now mature. Aero has been mature. And so ARMD has shifted to government-specific, which is air traffic control and emissions and acoustics and safety and infrastructures and so forth. So, what does space and NASA now do, which is most of NASA, now that space has matured? Well, what we’ve done so far is we have done Commercial Crew, commercial transportation. We’re becoming passengers, users, as opposed to developers. And now that space has matured, we’re going away from operations. We’re not operating space shuttles anymore. Musk is operating his rockets.

So, the question is — the centers that were set up when we started NASA in the late 50s, early 60s to do technology development and operations — what are they going to do? And with space as a whole matured as well as Aero, aside from government-specific, which is far less than 10 centers, what should NASA do going forward? So, NASA is involved now with the 2040 study to figure out what NASA 2.0 is now that space has matured and we’re becoming users and passengers.

And so, as I sit here on my last day of 60 years, what I’m thinking about is the future of the agency. As I leave, I have written a paper on the next 30, 40 years in society based upon the many new technologies, the many existential societal threats, the situation in space, and where society is going, to inform the NASA 2040 study. And I just hope that the 2040 study will result in a much more viable and stronger agency focused on what the nation really needs going forward. But we have changed from where we operated and developed within the centers just about everything to now we’re a customer.

Host: So, Dennis, you’re such a wealth of knowledge. Creativity is one of the topics we want to explore with you. What do you see as elements of the creative process, elements conducive to creativity?

Bushnell: First and foremost is knowledgeability. Humans invent by inputting facts, figures, data, knowledge into the subconscious. And the subconscious is constantly doing quasi random combinatorials of that. And then system-level evaluations. And when it finds something it likes, it reports back to the conscious when the conscious is no longer first-order occupied. Showering, shaving, driving, walking, running, whatever. And these are the eureka moments. And now the AI, the GANs approaches, ChatGPT, is now using the same process. Except the AI in the ChatGPT, they have now loaded the web into AI and therefore the AI now knows much more — many, many orders of magnitude than humans know in order to do ideation. And this adversarial generative business so-called is the same process humans use. So the AI can now ideate as good or better than humans from experience thus far. And I think that’s only going to get better going forward.

So going forward, it’ll be initially a partnership between the AI and the humans to do ideation. But to do ideation, you need two things. First and foremost, knowledgeability, but then you need also to know knowledgeability about what? And therefore you need very cogent, explicit, detailed issues. Take human-Mars, for example. We have looked at humans-Mars for decades. And essentially what was affordable was not safe, and what’s safe is not affordable. And what we needed to do was to get the cost down so we could afford safety. Because what the astronauts could stand in six months is different from a three-year Mars journey out and back. So, I’ve been working and have written several papers on the approaches and technologies to enable humans-Mars both safe and affordable. But that’s a barrier problem.

There’s barrier problems in Aero. Aero is now working AAM, advanced air mobility. And the issues there are safety, because the starting AAM safety record is some factor of a hundred to a thousand worse than scheduled airlines. So, we’ve got to get better there. Also, these AAM vehicles, many are being developed now and there’s 530 of them in development worldwide, developed to be personal air vehicles — affordable, safe personal air vehicles to replace automobiles, essentially. That vision since the early 1920s that people have had of a personal air vehicle is just about here. The vehicles are going to be here within a couple years. The issue that is, what about the ‘Mother may I?’ to get in the air with these things? And so we’re talking about instead of tens of thousands of aircraft in the air, we’re talking about many tens of millions. And things popping up from people’s driveways all over the place, not from airports. So, what you’re talking about is the Air Traffic Control system that is very different from what people are now considering and involves what has to happen to both the vehicles and the Air Traffic Control system, which is total autonomy and advanced AI and no humans.

And because the human latency and the human knowledge is way too slow and way too limited to take on this personal air vehicle, which by the way, is projected as a two-and-a-half trillion dollar new aero market. It’s essentially the auto market. So those are really basic issues. And you need those specified in all of their glory, including the metrics associated with all of that. Because as we here at Langley have looked at out of our IRAD program and out of our Aero program, which what of what we produced could be commercialized? And so, we went to professionals on commercialization, and they came back and said, ‘Not very many.’ And so, I looked at, why not very many? And it turns out that we in NASA do not understand, as many don’t, all of the huge number of application issues out there in the real world.

All of the engineering difficulties, all of the safety and regulatory issues, all of the economic competitive issues. There’s about 40 or 50 of those. And each of them has a pull-down menu for a particular application issue. And so, the universal experience within industry is you need many, many ideas, and then you evaluate them against all of these real-world issues to come up with one viable new commercial product. So, we here in NASA for ideation, need to understand much more about the real world, what the real world metrics are so that we can do what we weren’t doing, which is to carry the research far enough so that somebody might be interested in picking it up.

Host: And that’s where the creativity comes in?

Bushnell: Well, the creativity is coming up with enough ideas so that after you run them through the filter of all of these requirements in the real world, that you’re left with something viable. But people typically come up with an idea and they think, ‘Oh, this is wonderful.’ Well, the benefits of that idea are never bigger than the first microseconds you think of it. And thereafter, as you do the triage, as you work more the systems aspects, you find out that weight goes up, cost goes up, and safety is a problem and all kinds of other problems. You can’t be too married to one idea. You have to be a person with enough perseverance, a monomaniac with a mission if you will, with raw peasant toughness to carry something forward. But you also have to realistically analyze it in terms of the real-world metrics.

Host: And you’ve made the statement during recent presentations that mavericks are essential. How so?

Bushnell: Well, the studies indicate that going into kindergarten, most children are very imaginative. Coming out of second grade, not many are. The regimentation of society, the regimentation of education system tends to kill a lot of the creativity and imagination of people. You can reinstitute it, but it takes hard work to do that, but it can be done. But those children who were brought up with a great deal of independence, and by the way many of them were only children, are able to circumvent all the regimentation and come out with much more of their imagination intact. And those are the technical mavericks. And the technical mavericks are, according to the Harvard Business Review, the key to the new econometrics we’re now in. In the industrial age, we utilize natural resources to create wealth. Now today in the virtual age, we create wealth by inventing things.

And so, here at Langley and other places, the mavericks are the ones that do the inventions, produce the patents, and these people are very curious. These people do their knowledgeability. These people are very dynamic. They have tremendous perseverance. And these people question everything. And therefore, they’re very hard to supervise. And therefore, historically, most organizations have not been kind to their technical mavericks. And this has happened in NASA periodically also. So, what you need is a creative culture and there’s various attributes of that. And unfortunately, one of them is you need funding for creativity, and that has not been large within NASA recently.

Host: What are some of the key lessons learned over the years?

Bushnell: The major lessons learned by me is that I was here at Langley for 20 years before I figured out that what they really want me to do was invent. And so, I started inventing. And after I invented for a while, I studied the science, if you will, of invention and its technology and figured out that I had figured out how just about how to do it. And I’ve been fairly successful in inventing stuff going forward since then. With respect to the agency, the lessons learned, Ralph Roe, who just left as Chief Engineer a while back now, was a very great advocate for lessons learned and trying to figure all that out. He compiled a huge list of lessons learned. But we do not heed them.

It turns out that I was asked to certify the shuttle Thermal Protection System before the first flight, which was the first man foot. And I spent largely a sleepless week going around the country at the various contractors trying to figure out how that was designed and what it was. And then indicated what the steps and gaps on the TPS were supposed to be and what to do to make it safe. And when it was launched, I certified it. It was what we’d said. After that first shuttle flight, which thankfully was successful, landed, there were over 3,000 discrepancies between pre-flight and post-flight, as I remember with the steps and gaps and odd times. And as we’ve flown the thing over the years, there has been a great change in the location of bond air transition where the high heating occurs, flight to flight, because there’s been different damage flight to flight.

My personal evaluation of that was that there was a hydrogen dump line coming off the central hydrogen tank that passed very near the TPS system. And pre-flight after they put the hydrogen in and that dump line is very cold, ice forms on it. And when the thing launched, the ice would shake off and bang into the TPS, which could stand very little stress. When we first flew the drop test with the TPS on the shuttle initially, low speed drop test, the shuttle tiles just fell off. And we found out that they had very little pliable shear strength. So, this was a problem. And the CAIB study, which is part of our lessons learned, several of them, showed very well that we didn’t listen to that kind of information. We didn’t question why all this different stuff was happening and what its effects could be.

We got too much married to success versus looking in more detail. And so, a lesson learned that hopefully we’ve learned — we keep saying we’ve learned it — is to question everything, i.e., be like a maverick. Question everything. Be in a constant state of constructive paranoia. And by the way, that works for safety too, because personally, every time I relax, I get in all kinds of messes. You need to be constantly on your toes and never relax and look for things that while they haven’t created an accident now or haven’t cost us a lot of money now, could in the future depending on what happens. And then you have to have the knowledgeability for what could happen, and the associated tests associated with that.

Host: And would you say there’s an attitude of humility in that mix?

Bushnell: Well, of course. That’s the basic stance of all of this. I ran into this with the Navy. I’ve consulted for the U.S. Navy submarines for decades. And we were very quiet, and quiet is everything at undersea warfare. And then the Russians became really quiet also. And the Navy had trouble figuring out that this could happen. It’s the business of assuming you know everything you need to know and a feeling of confidence. That’s not useful.

Host: As people like you with such rich experience retire from NASA, how do you think the agency can capture and transfer knowledge?

Bushnell: What you’re trying to do with a knowledge capture is to rack up individual things often on projects and issues that are in the past. What you need for this for knowledge capture is to typify, take and document in detail what the most effective engineering approach is to various types of problems. And determine that from people leaving, determine that from the huge literature that’s involved with this. And then carry that forward. My experience in this agency over 60 years is that when we started, we had money on the streets. We had the extreme cooperation of the best minds in the country. And we had the best minds and superb leadership. Space is no longer the go-to go-go technology that it was in the 60s, for obvious reasons.

AI is the latest thing. And so the general intellectual milieu that you’re working with needs all the help it could get. And to go to Mars with humans successfully, I have looked seriously. I just wrote a paper with a physician who has been in space medicine with the Air Force and us for 40 years. And we racked up all of the really major issues in space. And it turns out that radiation, galactic cosmic rays, which is particles of radiation, at 30 to 50 gigaelectron volts of fully ionized iron. So, it’s not just gamma. It’s not just the Hiroshima stuff. It’s orders of magnitude more of the particles. It turns out that this is not just carcinogenesis. This affects your heart, your nervous system, your immune system, your DNA, everything, in very bad ways. And right now, there is no cogent way for the three-year missions to make sure that we can maintain human health for that long under those conditions, because we haven’t yet invented a way to produce a radiation protection system which is useful.

But here at Langley as it happens, we have borrowed a 40-year-old idea from the CERN accelerator people that very small curved silicon crystals, when they’re hit with galactic cosmic rays set up an electric system, which diverts them. And so, this is a very lightweight potential way to protect from radiation when they’re on Mars. The cartoons show that people are wandering around Mars, it looks like they’re playing golf sometimes. And surface habs. The surface habs do not protect you from radiation. On Mars, you need to have three to four to five meters of regolith between you and irradiation or a very, very thick, icy soil. Not these things that you see in the cartoons. We need to get serious about what human health really requires and then figure out how to pay for it. That’s very necessary going forward.

Host: Dennis, this has been fabulous. Thank you so much for taking time today to talk with us and we wish you the very best in your retirement.

Bushnell: Thank you.

Host: Are there any final thoughts that you might want to share with NASA’s technical workforce that might be helpful in the future?

Bushnell: Only that myself, and I’m sure the other retirees, some have told me this, are available. We don’t disappear over the horizon and we’re not accessible. I’ve given everybody and his brother and sister my home email and expect to be pinged on. When you say capture, one way to capture that is to capture our home email too. But it’s also important to develop the best minds worldwide, because technology worldwide is now flat. There was a book out in the middle ’00s that proved that everybody has about the same technology. And there’s brilliant people worldwide. And unfortunately over the years when I’ve asked my people about something, they will tell me what’s going on either at the center or possibly if they’re really good, what’s going on in the agency. But the research in the agency is a pale shadow, a minor dot in the research that goes on worldwide. And in fact, now 70 percent of the research is now done outside the U.S. and 75 percent of it is industry. So, we talked about being arrogant. Well, it’s not really arrogance. It’s a combination of culture. And people need to be much more knowledgeable and that’ll go a long way going forward.

Host: You’ll find link to topics discussed during our conversation along with Dennis’s bio and a show transcript at

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As always, thanks for listening to Small Steps, Giant Leaps.