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Go to Technology Today Podcast Episode 55: Fracture Control with NASGRO®

Episode 55: Fracture Control with NASGRO®

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NASGRO® fracture control software analyzes spacecraft, aircraft, structures and more for fractures and fatigue, wear and tear that could pose a risk if not repaired. With data that includes measurements and material composition, the software calculates how a crack could grow and become catastrophic. NASGRO was initially developed to support NASA’s Space Shuttle Program, but is now used by companies around the world to avert danger. Last month, the Space Foundation inducted NASGRO and its developers into the Space Technology Hall of Fame, which honors groundbreaking technologies that began as space programs and have since been adapted to improve the quality of life for all of humanity.

Listen now as SwRI NASGRO developers and Hall of Fame inductees Dr. Craig McClung and Joe Cardinal discuss the world-changing software’s capabilities and that shining moment of the behind-the-scenes technology taking the spotlight.

Visit NASGRO® Fracture Mechanics & Fatigue Crack Growth Software to learn more.


Below is a transcript of the episode, modified for clarity.

Lisa Peña (LP): A world renowned software and its SwRI developers are in the spotlight with a recent induction into the Space Technology Hall of Fame. It's a software originally made for spacecraft that now extends to aircraft and structures, keeping the public safe. All about this Hall of Fame technology and its many uses next on this episode of Technology Today.


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Hello, and welcome to Technology Today. I'm Lisa Peña. We're celebrating the recent induction of the NASGRO® fracture mechanics and fatigue cracked growth software into the space technology Hall of Fame. The Hall of Fame recognizes individuals, organizations, and companies that effectively adapt space technologies for other uses that improve the quality of life for all humanity. The software was originally developed by NASA for space programs. Now, NASGRO is the most widely used fracture control software in the world. Along with the software as SwRI NASGRO developers and engineers Dr. Craig McClung and Joe Cardinal were also inducted into the Hall of Fame. They join us now. A big congratulations on your induction and thank you both for being here, Craig and Joe.

NASGRO logo Courtesy of SwRI

NASGRO® fracture control software is used globally to analyze fractures and fatigue in spacecraft, aircraft, rotorcraft, gas turbines, bridges and more. The software and its developers were inducted into the Space Foundation’s Space Technology Hall of Fame, which recognizes technology initially developed for space programs that has expanded to benefit humanity.

Dr. Craig McClung (CM): Thank you for having us.

Joe Cardinal (JC): Pleasure to be here.

LP: All right, so uses for NASGRO software continue to expand beyond spacecraft. It's now used for aircraft, rotorcraft, gas turbine engines, and other structural components. Southwest Research Institute and NASA have been jointly developing NASGRO since 2001. It's actually a suite of different computer programs for different types of fatigue and fracture mechanics analysis. So let's start with understanding some of the language associated with the NASGRO software. Will you explain fatigue crack growth and fracture, new terms for some of us? And that occurs in structures or mechanical components. Craig, we're going to start with you.

CM: Sure. So if you have a metal component or a metal structure, and you load it repeatedly many, many times, thousands of times, millions of times with a big enough load, eventually you're going to form a very small fatigue crack in that component. That's going to happen a lot faster if you have some kind of a defect in the material to start with, or maybe you made a mistake in the manufacturing process. Well, if you keep on loading that little bitty crack for a long time over and over and over again, that crack is going to grow slowly and slowly and then faster and faster. And finally, it's going to break the structure. And it's not going to work anymore.

LP: When we talk about loads, are we talking about freight, people, temperature?

CM: It could be a mechanical load, or it can be a thermal load. So it could be either of those things. But the most obvious thing is you just put a very heavy weight on something, and you apply it again and again. Or it could be something like a wing loading on an airplane from the wind, you know, vibrating it a lot.

LP: So wear and tear, essentially.

CM: Absolutely.

LP: OK, so we're going to move into today's topic, NASGRO fracture mechanics and fatigue crack growth software. What is it and what does it do?

CM: Yeah, so as you said before, it's a lot of different computer programs in a suite. But the heart of the NASGRO methodology is it's a computer simulation of a growing fatigue crack. You apply a simplified model of the geometry. You've got material properties from experimental data. You've got some assumptions or measurements of the loads you apply, and you do this computer simulation, and it tells you how fast the crack grows and how long it's going to be before the whole thing breaks. This would be used by a designer, a structural designer, who's designing an airplane or a spacecraft or something to say, OK, if I happen to have a crack, I don't want to have a crack, but if I have a crack, I want to make sure that my thing I'm designing is going to last long enough safely until I reach the end of the service life of the part, the end of the mission or the end of the whole service life.

LP: What does the software need to make that analysis? So you're talking about it needs to know maybe what type of material, measurements-

CM: Yeah, so it needs to know the kind of material. And we have a library of material properties for 500 different metals that are built into NASGRO. You need to know something about the shape and the dimensions of the part that you're analyzing. We've got 100 different models or different idealized shapes and geometries. And you put dimensions on those. And then your loads are very often are calculated from analysis. People analyze how this part is going to be used and how much stress is going to be placed on it in its normal function.

LP: All right. And Joe, I want to turn to you now for this next question. Which industries benefit most from the NASGRO software?

JC: Thank you, Lisa. The historical industry was the development of the manned space program for the space shuttle and the use of design and analysis of the space shuttle. But that has expanded into other applications, primarily civil aircraft structures, aircraft, railroad tank cars, pressure vessels, piping, other types of mechanical equipment and heavy steel structures, such as bridges and the like. Other defense applications are also being used for Army and Navy, which is different than aerospace. And in recent years, last couple of years, mostly, the electric vehicle industry has been using NASGRO primarily for electric helicopter design, electric air taxis, and all this. And that's a growing area right now.

LP: So from spacecraft to now EVs. But when it was first used with NASA, so tell us about what they needed to find out. They needed to find out how the spacecraft was holding up launch after launch. What can you tell us about how.

JC: The space shuttle was really the first reusable manned spacecraft. And in order to ensure that the equipment on the shuttle was reusable and safe, it had to be designed to handle repeated loading. And repeated loading, as Craig mentioned, that's what gives rise to fatigue and fatigue cracks. So the analysis software handles those types of issues in the basically lifetime prediction of the structure. And the principles that are used that were used for the space shuttle are the same principles that can be used in any type of fatigue loaded metallic structure.
Hall of Fame ceremony Courtesy of Space Foundation

From Left to Right: Vanessa Wyche, NASA’s Johnson Space Center director and Hall of Fame induction ceremony keynote speaker, Joachim Beek, NASGRO lead at NASA JSC and Hall of Fame inductee, Dr. Craig McClung, SwRI NASGRO developer, Joe Cardinal, SwRI NASGRO developer and Tom Zelibor, Space Foundation CEO.

LP: So how did it come to be that NASGRO was expanded to other industries?

CM: Yeah, so probably the event that kind of kicked that off was a famous accident back in 1988. Aloha Airlines, the so-called pop top airplane kind of turned into a convertible because of some fatigue cracking. And that highlighted a big need in the industry to deal with cracking and aging commercial aircraft. And NASA realized, hey, this NASGRO tool could really help with that. And so they started working on that problem more. But as they got into it, they discovered that NASA's business was flying to space. They couldn't support all the users and all the application differences and all the additional needs that were required to solve everybody's problems.

And so they came to Southwest Research, and we knew the people at NASA Johnson they were developing NASGRO. And they came to Joe and to me and said, hey, would you guys be willing to be our partners in spinning off this technology and applying it to a lot of other industries? They already had hundreds of users, but they just couldn't support them. And so we signed a Space Act Agreement with NASA back in 2000. And under that agreement, we took over the commercialization of NASGRO. And we also became co-developers of the software with NASA. And we've been doing that for over 20 years now. We commercialize, we market, we support the non-space industries. And we jointly develop the software with the NASA team.

LP: All right. And now it's been expanded as we mentioned to many other industries. So at SwRI, we focus on research and development to benefit humanity. And many of us, the public, we may not even realize it, but NASGRO software benefits many of us daily. So how does NASGRO keep the public safe? We've talked about it a little bit. But do you have any specific examples of the NASGRO software really shining in the safety department?

CM: Yeah. Well, you know, I think the very best news about NASGRO is no news. Nothing's fallen out of the sky recently. When something does fall out of the sky, we get kind of nervous that somebody didn't do their job right. And that's really the compelling story is it fact that there are not accidents, that there aren't problems, that that's good. But more specifically, most of the commercial transport aircraft in the world today are designed and certified using NASGRO somewhere along the way. A few years ago, there were four or five different regional jets being developed in different countries around the world. Every single one of those regional jet programs were using NASGRO for their design and certification. And so that was kind of a cool feeling. Everything that NASA does, everything that the European Space Agency does is designed and certified with NASGRO.

JC: And Craig's talking about design of new equipment, new airplanes, new spacecraft, new structures. One of the areas that NASGRO is being used is to analyze and ensure safety of what we all have heard as aging infrastructure. So we're talking bridges, pipelines, other types of pressure vessels that have existed for 50 years or so. So this whole concept of structural safety, many things that are very old have to be requalified, inspected again for safety. And the concept of damage tolerance is safety in the presence of a flaw in a structure. And that whole concept involves more than just crack growth analysis, but it involves using software like NASGRO to predict crack growth life and define how often you need to inspect a structure, whether it be a bridge, an airplane, a space craft, reusable, et cetera, in order to make sure that you find flaws or defects before they become critical and can cause an accident.

LP: OK. And I do want to jump over to discussing the consortium at this point. So for our listeners, a consortium is a collaborative program that enables clients to pool resources to fund research. Consortium participants can then apply the findings to their own products and services, and it brings together companies with similar interests and cuts down on the cost of funding research alone. So SwRI currently manages more than 20 consortia in a range of fields from automotive and aerospace to robotics and energy storage systems. Now, NASGRO has one of these programs. So tell us about the NASGRO Consortium, Craig.

CM: Well, you've explained the consortium very well. The national consortium is a group of companies, mostly large companies, mostly in the aerospace world who collaborate with Southwest Research and with each other on a pre-competitive basis. And they provide stable financial support, as well as technical guidance for the development of future NASGRO versions. So they actually tell us what NASGRO needs to do in the future.
Hall of Fame medal Courtesy of Space Foundation

The Space Technology Hall of Fame medal was presented to inductees at the Space Foundation’s annual symposium held April 17-20, 2023 in Colorado Springs.

LP: All right. And since the consortium, the NASGRO Consortium was formed in 2001, what have been some of the most notable achievements over the past 20 plus years?

CM: You know, I think the most notable achievement is that the consortium has supported the development and release of a brand new NASGRO version almost every single year for 20 years. And every single new version has 20 or 25 new features. So it's just been this steady, steady movement to make the code better and better every single year. If you look at NASGRO 20 years ago and NASGRO now, it's just massive, massive improvement in the features and the capabilities. And you see it also in the funding level. The annual funding level in the consortium is four times larger now than it was in the early days.

JC: I think one of the big accomplishments that is quite remarkable, and this is part of the purpose of a consortium in general, is that we have all these companies together collaborating really on what they want to do and getting some agreement on how to do it. This is that's the purpose of the consortium is you're outside of a competitive environment, and that's the way it's set up legally. And the leveraging that goes on between ideas from different companies and our staff and our engineers here at the Institute has really been remarkable over the years. That's really a big achievement in addition to the technical details of the features.

LP: Yeah, so you're bringing these competitors together for a common goal. And how many companies are currently participating?

CM: 24.

LP: 24 companies in this consortium right now. So what are the benefits of consortium participation?

CM: Well, first of all, they do receive a site license or a corporate license for every new version of NASGRO as soon as it's released. They've always got the latest and greatest version of the code. They get substantial discounts on training courses. But as we just were saying, I think maybe the best benefit is they get to tell us what most needs to be improved or enhanced in NASGRO. So over time, they can tailor NASGRO to better meet their needs.

LP: OK, so much great information about NASGRO today and about the consortium. If someone out there is listening, and they want more information about the consortium and about NASGRO, where can they go?

CM: Go to our website, which is And you'll find information about training, about consortium, about the technical capabilities of the code. It's all there.

LP: All right. And we will have that website on the episode web page for episode 55. So not all your users are part of the consortium, so how can clients who are not part of it obtain a commercial license for NASGRO software? We'll go to Joe for this question.

JC: Thank you. Well, it's really fairly simple. As Craig said, go to the website. There's a licensing button on the website, and it gives you information and my contact information. And send me an email, and we can start a dialogue, or I can send you a quote fairly quickly. But we have licenses to NASGRO worldwide. And probably, it's about a 50/50 split between domestic US licenses and overseas licenses with many in Europe. And the license- one of the frequently asked questions about licensing is are there any restrictions on the software? And NASGRO is not restricted by any ITAR regulations. So pretty much anybody in the world can license it within reason, except for some of the bad actors out there. OK. We have licensed over 1,000 copies of single-seat licenses since we started licensing back in early 2000s and about 60 site licenses, which are unlimited users at a particular site. So there's a lot of flexibility there. We do require you to sign a license agreement, and we're very flexible on payment. Purchase order, credit cards are fast, bank transfers, the usual methods of making a purchase online.

LP: And if this sounds like something that is useful for your company, if you're listening out there, and you say, I think we could really use NASGRO, but how do we use it? Well, you have an answer for that. You offer very thorough training. Tell us a little bit about the trainings.

JC: Right. Craig and I have been doing trainings since 2006. We started out doing the trainings here at Southwest Research and did that for many years. With the pandemic and COVID, we switched over to virtual trainings, which was a learning experience for us. And we have, to date, put on about 90 training courses. These have been either public open courses or site-specific or company-specific courses. So we also do trainings for a specific company for a focus group within that company. And sometimes that's very effective because everybody is focused on the same type of problems. And for a site-specific training or a company-specific training, then we can tailor that agenda for the training to their specific needs.

And we've pretty much done everything online except for one in-person training since to 2020, 2019, the pandemic. The trainings are, we've trained over 1,700 engineers since we started training, which is quite a few. It's a hands-on training, and we go through theory, some basic theories, a little bit of advanced theory, a lot of examples that people run during the class. And there's generally a lot of feedback and question and answer. We have a wide range of customers that license the software, everything from one-man or one-person consultants to large companies that have individual licenses all over their network. So you can purchase one or two licenses. You can use it in-house. A lot of times, one of the success stories that we have is a company that started with a couple of licenses, purchased single-seat licenses. They sent some people to the training. Then they bought a site license. Since more people sent us to their place to do some trainings, and then they joined a consortium and have been in the consortium for a long time.

LP: So from there it grows.

JC: Yeah.

LP: All right, a lot of great information again. The website And we will have that website on our episode web page for more information. And of course, I want to talk about the reason why we are highlighting NASGRO today, a big accomplishment for the software and the developers sitting right here with us today.

The Space Technology Hall of Fame recognizes life changing technologies that emerged from global space programs. And as we've discussed, NASGRO started as a space technology and has been adapted for broader uses. So you recently returned from the Space Symposium hosted by the Space Foundation, where you as developers and NASGRO, were inducted into the Hall of Fame. What does this recognition mean for you and the NASGRO team?

CM: Yeah, well, thanks, Lisa. I'm really glad you said NASGRO team because it's a good reminder that NASGRO is not me and Joe. I mean, me and Joe are just kind of the head of the monster. But we've had some incredible teammates, and we still have incredible teammates here at the Institute, as well as at NASA, and they're the real technical heroes that makes stuff happen. We just come up with crazy ideas and say, can you guys do this? And they say, well, yeah, we can. But to answer your question, it was really gratifying to be recognized for doing something that really mattered to humanity. And you think about space, and we do a lot of space work here at the Institute, and a lot of the publicity focuses on the really glitzy stuff, the dramatic launches and the satellites and the deep space missions and the heroic astronauts. That's the really big time publicity stuff. But the recognition that we receive said that all this very quiet behind the scenes work year after year after year to make the world a safer place, hey, somebody noticed.

LP: We see you.

JC: And one of the things that I think Craig and I both feel very gratified about and our counterpart at NASA currently is that this is also a recognition of Royce Forman, who was the man at NASA for many, many years, who initially began the whole development of the NASGRO software for the space shuttle activities.

CM: 40 years ago.

JC: Yeah, this was 40 years ago. And his vision of NASGRO was just great because it went out to many different industries. And it was also a way of thanking him for coming to the Institute to have us do this work for the last 20 years or so.

LP: So just recognition for everyone, past and present, who has had their hands in developing this software that, as we've said, is benefiting humanity in so many ways. The reach of NASGRO is far and wide. So tell me a little bit about your induction experience. After years of working on the software, what did it feel like to be in that room, on that stage, receiving this honor? You touched on it a little bit, but personally for you, what were your emotions like that day?

CM: Yeah, it was amazing. I think I didn't imagine it being what it was. The induction banquet was a two-hour multimedia production with 500 people and all these dignitaries up on the stage and in the audience. And they were all there because of NASGRO and the other two technologies that were being inducted that night. It was like, wow, you're all here because of me. That's really, really humbling. And the banquet was the final event. It was the climax of the Space Symposium that has like 15,000 people attending. This is a really big deal. And for us to be featured there which like, wow, that's really amazing.

LP: If you didn't know about NASGRO before, you sure knew about it after leaving that symposium.

JC: Well, I certainly agree with everything that Craig said there. And it was exciting. It was overwhelming a little bit. And it was thrilling. Craig and I and the NASGRO team, 20 years ago got an IR&D 100 Award for NASGRO. And that was a big experience. This went way beyond that, as far as the level of involvement, the number of people involved, and just excitement level.

LP: So I want to hear a little bit about you as engineers. Tell us about your journey to working on this Hall of Fame technology. What did your path of developing NASGRO look like?

JC: Well, NASGRO, which is the name of the software that has been in existence since 2000, originally was called NASA/FLAGRO. And back in the late '80s, in the early '90s, that was free software from NASA Johnson. And because we were involved doing damage tolerance analysis for the Air Force and other type of activities, we were users of that software. And that's when I first started using NASA/FLAGRO back in the early '90s on aircraft damage tolerance analysis and also on railroad tank car applications. So we got involved with the NASA folks that were developing software as users but also as technology experts in materials and fatigue and fracture. And so as that experience from a user and as experience from technology expertise became aware, that's how we got involved in the consortium, set up the consortium, worked with NASA to continue that development, it was very interesting and very much a learning experience for us to get involved with the details of the program. And one of the things I didn't mention with the training, and I'm sure Craig will echo this, is that the best way to learn the details of some software is to start training people on it. So as that process went on, we found stuff that we wanted to change in the program, as well as problems that people had using it. And so that was sort of our continuous improvement process.

LP: So from user to teacher...

JC: Yeah.

LP: Essentially.

JC: Yes.

LP: ...has been your journey.

JC: Yes.

LP: Craig, tell us a little bit-

CM: Yeah, I just add on to that. As I look back at especially the last 20 years, it's kind of about doing what we do so well here at Southwest Research, which is talking to people, listening to people, getting close to the customer, developing relationships. We've gotten to know the experts in the industry at these big companies as personal friends in some cases. We have a meeting coming up in a few weeks, and we're going to see old friends again. And just over and over again, you go to these people, and you say, hey, what do you need? Tell us what you need us to do for you. And then we have our relationship with our teammates to sit down and say, what can we do to make this happen? How can we solve this challenging problem and make the code do something different and go do it and then go back out to other companies and say, wow, look what we've built, wouldn't you guys like to use this, too? And just keep growing and growing and just building new relationships and getting to know people and doing more listening.

LP: What motivates you to continuously improve the software and expand its uses?

CM: I think really just realizing that what we are doing is really making a difference in how real stuff, like airplanes and spacecraft, is being designed and certified. And it really is making the world a safer place. It's different because of what we're doing. And we're on top of that. We haven't said this yet. We're helping new companies to get into the marketplace. A lot of new companies that are doing commercial spacecraft and that are doing urban air mobility, and these are little startups, they don't have fracture experts. They don't have a staff to go write a computer program. But they can use NASGRO, and they can play with the big boys. And so we're helping a lot of these smaller companies to get into the marketplace.

JC: And I've found that it's very rewarding and motivating to be able to address these types of problems, fatigue and fracture for new companies, as Craig said, new engineers now. I mean, we are retraining or training new engineers in many of the consortium companies, people just out of school or within 10 years of school. So that's always rewarding. But it's rewarding and motivating to be able to help people solve their problems so that they can build their equipment and use it safely. The thing about NASGRO is that I've been working on NASGRO for 23 years or more as a user. And it's always different. There's always something new or different, whether it's a new capability or a new client that's excited and wanting to use the software and answering questions and the like. It really helps- that's what keeps me going. It's kind of like that's what the Institute is about. And one of the things that NASGRO is, I think it's a really great example of the type of impact work that the Institute does, going from technical expertise to marketplace and technology transfer for a wide, wide variety of people. So going from one industry to another industry and just carrying that out into the marketplace and into the technology space.

CM: So if I can just add one more comment about the motivation. The products that are being developed with help from NASGRO designed and certified, they're going to be flying those airplanes and using those components for decades in some cases and using them safely. And that's a real legacy. I can get on an airplane and say, yeah, we helped to make this safe. I feel good about that. And it's going to be happening for a long time. There's a real sense of a legacy here. We're near the end of our careers, but the stuff that NASGRO has helped to make safe is going to keep going for a long time.

LP: And NASGRO has such a successful past. What's next for the software? What do you envision for the future of NASGRO?

CM: Well, we keep a list of ideas of things we'd like to do in NASGRO. And that list is about 10 years long. And by the time we get a couple or three years into it, we come up with a three or four years of new ideas. So there's just a lot of stuff there that we're excited about doing, and it'll be going on long after Joe and I retire. We have some very specific ideas about making it easier to interface NASGRO with other computer programs and other analysis tools to make the whole design process more efficient and faster and cheaper. And I guess the other thing we're really seeing is looking forward to NASGRO dominating the world market for fracture control, just growing and getting bigger and bigger all over the world.

JC: I can't really add too much to that. I think one of the things that's always interesting is new clients and new industries. I'm sure there are new industries out there new to using NASGRO that can use the software effectively and marketing and training those type of companies is part of the future. One of the new areas that we touched on already is the electric vehicle area, the electric aircraft, air taxis, unmanned aircraft. So those are all areas that have potential growth.

LP: All right, NASGRO is going to some exciting places, it sounds like. So much accomplished and so much more to do. I really feel like today's episode is a clear example of why we do this podcast to highlight technology that's impacting our lives and changing the world. And NASGRO is doing just that, working behind the scenes, as you said, Craig, to keep us safe in so many ways, and it's been great to shine a light on this groundbreaking software and to learn more about its extraordinary developers. Congratulations, again, on your Space Technology Hall of Fame induction. And thank you for joining us on the podcast, Dr. Craig McClung and Joe Cardinal.

JC: Thank you for having us.

CM: Thank you, Lisa.

And thank you to our listeners for learning along with us today. You can hear all of our Technology Today episodes and see photos and complete transcripts at Remember to share our podcast and subscribe on your favorite podcast platform.

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Ian McKinney and Bryan Ortiz are the podcast audio engineers and editors. I am producer and host, Lisa Peña.

Thanks for listening.


NASGRO® is a suite of computer programs used to analyze fracture and fatigue crack growth in structures and mechanical components. The software is developed jointly by Southwest Research Institute and the National Aeronautics and Space Administration (NASA) under a Space Act Agreement, with additional support from the NASGRO Consortium and the Federal Aviation Administration. NASGRO is the most widely used fracture mechanics and FCG software in the world today, including many applications for aircraft, spacecraft, rotorcraft, gas turbine engines, pressure vessels, and other structural components.