2009

Starr Ginn decided she wanted to work for NASA after interning in their Summer High School Apprenticeship Research Program (SHARP) following her junior year in high school. She is currently the Deputy Branch Chief of the engineering directorate’s aerostructures branch at the Dryden Flight Research Center. An expert in aircraft ground vibration testing and flight flutter testing, she recently designed and developed a unique aircraft jacking system that allows a test specimen to “float” during ground vibration testing.

NASA Tech Briefs: Your first experience with NASA Dryden came as an intern in the Summer High School Apprenticeship Research program following your junior year in high school. What prompted you to apply for that program?

alt Starr Ginn: Well, I was sitting in my chemistry class and we had some engineers come by and tell us about this high school program, and as soon as they said they worked for NASA, of course, it kind of stretches your imagination as to the possibilities. So obviously, that sparked an interest. Secondly, I’d have to say just my competitive nature; I wanted to get my resume in there and beat out the rest of my friends to see who could get this job. It was just the right timing, and I had the right information on my resume, and they gave me an opportunity.

NTB: What impact would you say the SHARP program had on your decision to eventually pursue a career in engineering?

Ginn: It was actually the best thing that’s ever happened to me in my life. I was one of those students that came from a family with no college graduates. I knew I was good at math and science, but I had no idea exactly how you applied that, other than being a teacher. So, having that experience, I came out to Dryden and it was love at first sight. I was just overwhelmed with the possibilities of what I could do. I knew right then and there, right after that summer, that I was going to become a mechanical engineer and I was going to work at Dryden.

NTB: Were any of the guys in your class interested in this program? And did you take any ribbing from them, you know, being a woman and going into engineering, and wanting to work for NASA?

Ginn: I think the boys knew better by then that I was pretty competitive and they were always up for a competition with me in that respect. I’d say the class I was in wasn’t even 50/50 girls to boys. But no, I guess just them knowing my personality, they really didn’t give me a hard time about it at all.

NTB: You are currently the Deputy Branch Chief of the engineering directorate’s aerostructures branch at the NASA Dryden Flight Research Center. What does the aerostructures branch do, and what types of projects do you typically get involved with there?

Ginn: I’m pretty sure we are the biggest engineering branch in the directorate, and we do a plethora of things starting with dynamic thermal and structural analysis. That includes finite element modeling, aero loads analysis, flutter analysis, aero servoelastic analysis, aero heating. We also have a laboratory attached to us, so we do dynamic thermal and structural ground tests. Some of those tests are ground vibration tests, structural mode interaction testing, and we do structural loads calibrations and equation derivations, proof load tests, and combination thermal/structural testing.

Another feather in our cap is that we do advanced structural instrumentation, which includes strain gauges, temperature and deflection gauges, and the biggest thing right now that’s becoming world-renowned is our fiber optic strain and temperature sensors. And, of course, all of that results in doing flight test support, which is what we’re doing at this particular NASA branch.


NTB: You recently designed and developed a unique aircraft jacking system that allows an aircraft to “float” during ground vibration testing. Please explain for us, if you will, how that system works and how you came up with the idea.

Ginn: Every time we do a ground vibration test, we always want to come up with a way to isolate the vehicle from the ground so we can get the most pure data when we excite the vehicle, and it’s the easiest for the analytical modelers to update their models with the information. So, there are different techniques for doing that. You can use bungee cords…

NTB: That’s not very sophisticated, is it?

Ginn: No, it’s not very sophisticated. Some of the things you do just always work, and sometimes you just need to do them even though they’re not sophisticated. But then people started trying to figure out how to put test articles on air bearings. Right before I started with the branch we actually had a company design this air bearing for us, and it’s big, and it’s heavy, and you have to get it underneath an airplane under the jacking points, and to do that it’s a very hazardous situation. You have a big crane that’s suspending an entire F-18, and you have to retract the gear, and then you have three people move these huge air bearings underneath the vehicle. It takes three people to move each one into place, so you had a lot of people spending a lot of time under suspended aircraft. It’s not ideal, so it was just one of those things that you see a couple of times and people in our group started to say, “We’ve got to come up with a way to incorporate these air bearings in some sort of aircraft jacking mechanism.”

Even after I knew I was going to work at Dryden, I decided not to do aerospace as my background; I was much more mechanical-minded. Any kind of opportunity that comes with trying to figure out how to fix something or make something work better, sparks my interest, so as soon as somebody mentioned that, I said, “Put me on the job. I’ll figure something out.”

It was one of those things where it was not on the front burner of any of Dryden’s projects so they could say, “Yeah, let’s put a bunch of funding into this idea,” so it really took a lot of my own resourcefulness. After I’d get all my project work done, I’d be spending time working on designs, vetting it with some other engineers, making sure it all looked kosher. It actually took several summers. I’d have co-ops or interns helping me, just so that I could still get my day-to-day work done. But it was definitely worth the effort.

What's great about this system is, you have an airplane now that’s sitting on its gear, and you just roll the system right underneath at the jacking points, like you would an aircraft jack. It’s electrically activated, so I have electric motors driving these actuators that then pick up the vehicle, and while the vehicle is resting on the soft support we’re able to retract the gear, because that’s a critical testing consideration. We need to be in “gear-up,” because that’s how the airplane is most of the time. Then we just inflate the system. It takes all of a half-hour, which before, we had to have meeting after meeting after meeting to coordinate such a hazardous task. It would take a whole day just to get an airplane on the isolators, so it saved a lot of time, and it saved a lot of money in terms of not having anything fall that’s one-of-a-kind.

We've now had three opportunities to use it. We’ve used it on our G3 airplane; we used it on our F-15 airplane; and I just got done using it on the Orion Pad Abort Crew Module.

NTB: That’s the new crew vehicle, right?

Ginn: That’s correct. That’s the new crew vehicle.

NTB: How long did it take you to get this system in place and operational?

Ginn: Once we started cutting metal, it was probably, I guess, about a year-and-a-half to get all the parts and get it assembled. I had to build up manuals for it. I mean, it’s a very formal system. It had its own task analysis; it has its own maintenance book. Then I had to set up the whole proof testing for it. We put 108,000 pounds on the entire system to proof test it. So I designed all the fixturing that it took to do the proof test. As soon as that test was done, within a month, we were actually using it. I actually completed it in December 2005 and it was used for the first time in January 2006.

The whole idea started in 2002, just to give you an idea of how long it took to come up with the money. It’s a system that, throughout the years, has added up to at least $200,000 of materials and off-the-shelf parts, so part of the money resourcefulness was, each year, kind of going around and trying to get people’s end-of-year money, or find little scraps of money or people who were interested in investing in it, and it took a couple of years to build up all the parts we needed.


NTB: You also have considerable experience in the area of flight flutter testing. What is flutter, how do you test for it, and more important, how do you control it?

Ginn: Flutter is a natural phenomenon that happens, and it’s a case where you get just the right aerodynamic conditions where you’re exciting two different modes of a test article at the same time. Each mode is trying to beat out the other one, so what happens is, you have these two natural frequencies that are trying to occur at the same time and they just keep beating each other up until something structural catastrophically fails.

One example that everyone can relate to is the Tacoma Narrows Bridge. That was a situation where you had the wind speeds just right coming over the bridge that day, and it was trying to excite the bending mode and the torsion mode of that bridge at the same time. You saw the result of that. The two modes were trying to overtake each other, and neither of them won.

We do the same thing with aircraft. Any structure has natural frequencies. First of all, you have somebody who builds up a big finite element model and they say, “This is how I want you to build the vehicle.” And, of course, the vehicle gets built and, number one, maybe it’s not built exactly the same as what the model showed. Number two, anything in real life is not linear, and most all modeling techniques are linear-based. So what happens is, before we actually go to flight with a test article, we have to do ground tests to it to make sure that we do understand what it is that we’ve made, and then we try to update the model the best that we can – even though they are linear models – with what we know about the vehicle. So, when these structural models get updated, we run an aerodynamic code over the models and we do this flutter analysis. We tell it the flight conditions we’re going to have the test article at, and it tells us how the frequencies are going to be changing as the dynamic pressure increases. So what we look for are any of these natural frequencies going to go divergent or coalesce at these higher dynamic pressures that we’re going to flight test in.

NTB: Of all the disciplines that come under the general heading of mechanical engineering, what sparked your interest in vibration analysis, which is probably one of the more math-intensive subjects?

Ginn: I’m one of those people who think that everything just happens for a reason. I did most of my interning at Dryden doing mechanical design tests, and when it actually came time for them to give out job offers, they had to fill spots in certain areas and the offer that was sent to me was, we have a spot for you in structural dynamics – take it or leave it. And I absolutely was going to take it because this was my dream job and this was where I’ve wanted to work forever, so I took it.

It was very much a challenge for me because some students in mechanical engineering have to take one vibrations class – it just depends on the school you go to – but I didn’t even have a vibrations class. I came in completely open-minded to a brand new subject, so the first year was all on-the-job training. I spent most of the time doing all ground vibration testing, getting up to speed on different kinds of testing techniques in that area, and then I realized I’ve got to get some theoretical background so I really understand what it is I’m doing. So, about a year after starting in the group, I ended up slowly taking some masters courses to get myself up to speed on what my everyday job entailed. NASA has a graduate studies program where they’ll actually send you for a year to go get your masters degree, so I got into that program and I ended up going to UCLA and I got my masters in aerospace engineering, with an emphasis in aeroelasticity.

NTB: Here’s a chicken-and-egg question for you. When you’re not working at Dryden, you enjoy flying your own aircraft. Was it your work at Dryden that inspired your love of flying, or was it your love of flying that prompted you to pursue a career at NASA?

Ginn: It was absolutely my work at Dryden that made me want to start flying airplanes. Besides just being around flight tests – which I compare to the movie Top Gun, that’s how inspiring it is to me – there are actually a lot of engineers here who are all into flying personal aircraft, and it was just being around both of those environments. And, again, it’s really my competitive nature. One day somebody took me flying, I’d never been before, and this was actually when I was a student in the co-op program – I was 21 – and another full-time engineer took me flying, and I said, “Man, if this guy can fly an airplane, I can fly an airplane!” So that’s where it started. I decided I was going to go get my license, and it’s become more than just a hobby. My husband and I actually ended up building our house on an airport so that we have our airplanes in our backyard and we can taxi right out and go somewhere.


NTB: You’ve made several promotional videos for NASA encouraging young women to pursue careers in engineering. Do you think more needs to be done in this area?

Ginn: I do. And I think it’s more at the younger ages, though, because I think our society’s still kind of segregated – girls and boys – at the young ages. Girls are supposed to play with dolls and play in the kitchen, and boys are supposed to be playing sports or building with LEGOs. There are just these stereotypes that still a lot of families kind of push. So what needs to happen is, at a younger age girls need to realize that they can do absolutely everything that a boy can do, and they might find that it’s more interesting than the toys that they were given to play with because they were girls. So I’d like to try to hit more of the elementary age schoolgirls. Even up to the 8th grade, I think you still have a bit of an influence on the girls. The girls, after they’ve started school, realize they’re pretty good at math and science, but maybe they get intimidated that the boys think they know more about math and science from their natural play.

NTB: Or they think, like you did, that the only route they can take with that kind of interest is teaching.

Ginn: Right! Exactly. How do you apply this stuff?

NTB: They need someone like you to expose them, I suppose, to other career paths.

Ginn: Because I feel like I had so many perfect opportunities that all seemed to fall into place at the right time, and most all of that was done during my school-age years, I try to give back as much as possible to our education programs that we have here, whether that be going out to the schools during engineering week, or going on recruiting trips to the colleges, or just anything I can do. We try to take, even personally outside of work, when we see kids that seem like they have an edge in one of the stem fields, we’ll take them flying in our airplane just to start getting them enthusiastic about the things you can do. But we still have to do a lot more in that area. NTB The only long-term goal I have is, I know that I will be working for NASA for my whole career. It’s an amazing place to work. As far as what particular job I’ll be doing, it’s always just been what opportunities pop up at the right time that just make sense. After doing a lot of technical work in the structural dynamics group, I had a short opportunity to act as a chief engineer on a new potential x-plane. Unfortunately the program got canceled when it moved into the second phase, but that was very exciting. Then, this branch chief opportunity came up and it just really fits my personality, being a real people person as well as being technical. So I’m having fun doing that. I’m not sure where everything’s going to steer from there.

NTB: Looking ahead, what are your long-term goals at NASA?

Ginn: The only long-term goal I have is, I know that I will be working for NASA for my whole career. It’s an amazing place to work.

As far as what particular job I’ll be doing, it’s always just been what opportunities pop up at the right time that just make sense. After doing a lot of technical work in the structural dynamics group, I had a short opportunity to act as a chief engineer on a new potential x-plane. Unfortunately the program got canceled when it moved into the second phase, but that was very exciting. Then, this branch chief opportunity came up and it just really fits my personality, being a real people person as well as being technical. So I’m having fun doing that. I’m not sure where everything’s going to steer from there.

For more information, contact Starr Ginn at This email address is being protected from spambots. You need JavaScript enabled to view it..

To download this interview as a podcast, click here

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.