A conversation with Nettie Roozeboom, aerospace engineer in the Wind Tunnel Division at NASA’s Ames Research Center in Silicon Valley. For more info on Nettie’s works, visit https://www.nasa.gov/ames/nisv-podcast-power-of-pink.
Transcript
Matthew C. Buffington (Host):This is episode 25 of the NASA in Silicon Valley podcast. Today’s guest is Nettie Roozeboom, and aerospace engineer in the Wind Tunnel Division at NASA Ames. When it comes to air travel, NASA is with you when you fly. Working in the wind tunnels, obviously Nettie works on aeronautics. But she also plays an important role in testing rockets. Recently, even testing the big SLS, Space Launch System, rocket that will take us out of Earth’s orbit and on a journey to Mars. We also mention in the conversation a previous story on her work called the Power of Pink that you can find at NASA.gov/Ames and an audio version on the podcast feed. Here is Nettie Roozeboom.
[Music]
Host:How did you get to NASA? How did you come to Silicon Valley?
Nettie Roozeboom: Yes. I’m very happy to say I was an intern here in 2007, summer of 2007, and worked in the Vertical Motion Simulator, world’s largest simulator.
Host:Wow.
Nettie Roozeboom: Yeah. I will forever be thankful for my mentor that summer and the whole division that I worked with that really just opened my eyes — actually, that summer I realized maybe I do want to go to grad school. At that moment I just kind of —
Host:Kind of fell into it.
Nettie Roozeboom: Yeah.
Host:Are you from California or how did you end up –?
Nettie Roozeboom: Good questions. There may be a little bit of an accent, maybe most of it . . .
Host:Is California taking over your accent?
Nettie Roozeboom: Yeah, yeah, sadly. But I grew up in Tennessee and spent all my life there. I went to undergrad in Tennessee. And actually, I think a reason why I’m here is I ran cross-country, indoor/outdoor track in college on scholarship, so that was one thing that they noticed whenever I sent my resume for an internship.
Host:You stand out amongst all the other scientists.
Nettie Roozeboom: Yeah, yeah. There’s this student that has really good grades, but she can run year-round and compete year-round. The gentleman that hired me for my internship was like, “If you can do that, you can work here.” And yeah, it was really a blessing that they noticed that, because there’s so many things that you try to be well-rounded and be a part of different parts of the undergrad life. I mean, that was a big part. That paid for my undergrad schooling. So to have that acknowledged that, “Hey, that’s valuable also in the workplace” —
Host:And that was school in Tennessee, and then you moved to California —
Nettie Roozeboom: Yeah.
Host:— to start your job.
Nettie Roozeboom: Yeah, yeah.
Host:This was your first job.
Nettie Roozeboom: Yeah, yeah.
Host:Or internship.
Nettie Roozeboom: Right. And I interned that summer. It went amazing. Made a huge difference in my life. I always like to tell people that they were very kind. I told them, “I think I want to go to grad school.” And they proposed, “Think about grad school here. Think about working here.” I just couldn’t imagine anything but getting back to Tennessee. [Laughs]
Host:Did you end up going to grad school out here?
Nettie Roozeboom: Yes. So, I told my mother that, and she said, “You’re going.” And I appreciate her pushing me to say, “Do this. This is a once-in-a-lifetime chance.” So, I said, “Great, let’s do it.” So I moved out here the following year after I finished undergrad, and I started working here as a civil servant. And I did my master’s at Stanford part-time.
Host:Was it like a Pathways Fellowship or something like that, or a different program?
Nettie Roozeboom: No. It was just kind of through the training budget that I completed this. It was a great opportunity — like, you are working full time, you have a full-time job. And of course trying to get classwork that complemented my job, but yeah, it was a lot.
Host:That’s always the ideal situation. If you can actually work in the field you’re doing, and then studying, I’m sure that also helped your classes.
Nettie Roozeboom: Yeah, yeah, yeah.
Host:Because you’re sitting in classes, and you’re like, “Well, let me just go to NASA and sort this out.”
Nettie Roozeboom: Yeah, yeah. No, and it was really great to kind of have that hands-on application when I’m taking advanced fluid dynamics, which is probably — it brings so much joy to me, like thermo and fluid dynamics. But I’d go back and try to work out a problem with one of the engineers at the wind tunnel, and say like, “Well, I’ve been studying these equations, and this is what I just learned.” Yeah, that was a lot of fun.
Host:That’s so much fun.
Nettie Roozeboom: I will give the full disclosure, it was stressful.
Host:Of course.
Nettie Roozeboom: You come to work and everyone is on their A game here, and then you go to school and everyone has their homework turned in, and you’re —
Host:People go home to like relax, watch some TV. And you’re going to class.
Nettie Roozeboom: Yeah, yeah. It was very enriching and of course a wonderful opportunity.
Host:And your graduate degree was in –?
Nettie Roozeboom: Mechanical engineering.
Host:Okay. So not a scientist; an engineer.
Nettie Roozeboom: Yes, I’m an engineer, yes, yes.
Host:Excellent. So, when you came in as an intern, you were working on the VMS. That is the Vertical Motion Simulator.
Nettie Roozeboom: Yes.
Host:Unfortunately, I’ve only seen it from the outside. So, describe a little bit of what is a Vertical Motion Simulator.
Nettie Roozeboom: Yeah. Matt, we have to get you there, because it’s really incredible to see. You can imagine it being the world’s largest simulator. It’s a fairly large facility.
Host:It almost looks like a bus on stilts — or kind of elevated up.
Nettie Roozeboom: Yeah, yeah. So the Vertical Motion Simulator is six stories tall, and they have what they call cabs. And these cabs are interchangeable. And this cab is on a system that has six degrees of rotation. So it can go up, down, side to side, and left and right. And then it can also tilt in all three directions. So pitch, roll, and yaw.
And how that’s important is, during the shuttle days, astronauts that were going to fly the shuttle would come here, and they would train in the VMS. So, they would have different simulations, because there are several different landing sites around the world. If there was a problem and you couldn’t land in Florida or California, so you could land in Spain. But you don’t always get to practice landing in Spain. [Laughs]
Host:So you could practice it with a machine.
Nettie Roozeboom: Yeah, yeah. And then, what makes it even cooler is that you could practice landing in Spain with a 40-degree headwind, with rain —
Host:And it has monitors that kind of circle all around. I bet you really feel your stomach pulling.
Nettie Roozeboom: And one of the cool things that I got to do that summer I was interning was land a lunar rover on the moon. [Laughs] So it’s really cool. And they have the different cabs, so you can have like —
Host:Does that whole top part get replaced?
Nettie Roozeboom: Yes.
Host:When you say “replace the cab,” there’s a shuttle cab.
Nettie Roozeboom: Yeah.
Host:There’s a moon lander.
Nettie Roozeboom: Yeah, like a 747 cab. There’s a moon lander cab. There’s a helicopter cab. So there’s all these different cabs. Different pilots come in from different walks of life that have different missions, and they can simulate that.
Host:So it’s not just NASA.
Nettie Roozeboom: Right.
Host:This is like other folks can come in, use the space, and practice.
Nettie Roozeboom: So another great facility, along with the VMS, is the CVSRF [Crew-Vehicle Systems Research Facility]. At this facility, they have a 747 cockpit, and then they have one that they can adapt to different airplane configurations.
Host:Oh wow. So big planes, little planes, different —
Nettie Roozeboom: And you’d never guess who is a big user of this facility, is UPS pilots.
Host:Really?
Nettie Roozeboom: I mean, it’s just amazing the outreach that NASA has. No one would ever think that NASA and UPS have something in common.
Host:Well, you’re flying planes. It’s like —
Nettie Roozeboom: And to go back to the first day at NASA Aeronautics and how that has a huge impact here at Ames.
Host:You mean Ames was a NACA facility before NASA even existed.
Nettie Roozeboom: So it’s really fun to just keep thinking of all the things that NASA does. You have UPS pilots coming here and training in all the different facilities. There are airports that they’re going to land out to. It’s really, really neat.
Host:That’s fascinating. So, you were an intern working in this Vertical Motion Simulator, landing on the moon. Just like a normal internship.
Nettie Roozeboom: Yeah, you know, just a normal Friday.
Host:So, that landed into a job in like the engineering organization?
Nettie Roozeboom: Yeah. And actually, I started my career in the air traffic management group.
Host:Cool, okay.
Nettie Roozeboom: Yeah, ATC ATM [air traffic control, air traffic management]. I would encourage everyone that’s listening to go and look and discover everything that NASA is doing for the airspace. And of course, the new topic that you have talked about is UTM, the unmanned air traffic management.
Host:The air traffic control for drones.
Nettie Roozeboom: Right, right.
Host:We’re basically developing that software, the platform — developing that platform of what could be used in the future.
Nettie Roozeboom: Right, right. It’s amazing. I mean, if you’re studying math and you’re thinking, “What am I going to do with a math degree?” there’s like a huge optimization problem there to solve. It’s really amazing. I would encourage everyone to talk about it. And like, how do you get more planes in the sky? Which is, how do we increase air travel but decrease the workload on controllers? Because there is a conversation that happens between a pilot and a controller every time they move through the airspace. Yeah, it’s really cool to think about.
Host:It’s interesting for people who live in the Bay Area or anybody who’s visiting, if you’re driving on 101 and you go past NASA and you see a big hangar and the big buildings, one of them is holding this Vertical Motion Simulator. Then the other ones are these big wind tunnels. And I know you’ve been doing a lot of work in the wind tunnels, and this is some of the stuff you’re working on now.
Nettie Roozeboom: Yes. I work in the Wind Tunnel division. I work in a building called the Fluid Mechanics Lab. We have six small wind tunnels. We have wind tunnels that are — actually, I should call it like a fluid — it’s a water channel.
Host:Okay. So it’s like you put the design in water, so then that way you can actually see, visually see how the air flows over.
Nettie Roozeboom: And that’s the beauty of this water channel which the flow is going one inch per second. So you can see how this flow is developing nice and slow, and how it would flow over an airplane.
Host:Do you put dye in that water?
Nettie Roozeboom: Yeah.
Host:Or –?
Nettie Roozeboom: We put fluorescent dye. We turn out the lights. We can excite the dye with some blue lighting, and you can see how this dye will move around an airplane, or a car, or a soccer ball; everything that moves through a fluid, how it would react.
Host:I remember you were doing a story back around the Super Bowl —
Nettie Roozeboom: Oh yeah, yeah, yeah.
Host:— where they were trying to — it was different dynamics, trying to see how — like a soccer ball, or how sports objects would have — you know, the air —
Nettie Roozeboom: Yeah, streamlines coming over it, and how the flow would go over the football, and how did the ties mess with the flow, or change the flow. Yeah, and having a spiral ball flying through the air, what does that look like? It’s a really great way to visualize the flow.
Host:And super helpful for airplanes or spacecraft or anything that’s going through an atmosphere. You can kind of try to see how does that work, and then adapt your design.
Nettie Roozeboom: Right, right. And also in the Fluid Mechanics Lab we have several different wind tunnels ranging from low-speed — there will be a desktop wind tunnel — up to a facility that runs .6 mach, so six-tenths the speed of sound.
Host:Oh wow. I imagine that’s a big wind tunnel, and powerful.
Nettie Roozeboom: Yeah, it is more powerful. And the test section is fairly small so that we can get those high speeds. But as you can imagine, these are very small facilities. We can design models, create ideas that we have brainstormed — having a machine out of wood or plastic, or whatever would be necessary — or even metal, and throw them in these small facilities where it takes maybe one, two people to run the facility.
Host:So for people who have no idea what a wind tunnel even is, it’s almost like you have a big chamber where you would put an airplane. And is it something almost like a loop where air gets circulated? How does that work?
Nettie Roozeboom: Great question. What is a wind tunnel? [Laughs] Yeah. A wind tunnel is a machine or facility that we put vehicles in, vehicles of all different types, and see how the air moves across them. Instead of having the vehicle move through the air, we have the vehicle stationary and then have the air moving over it.
Host:How do you get that air moving?
Nettie Roozeboom: Every wind tunnel needs some kind of fan, some kind of fan to move the air over the vehicle. So every wind tunnel will have a fan, and every wind tunnel will have a test section. And that’s where we mount the model.
Host:For the folks listening to the podcast, I believe it’s maybe the sixth or seventh episode in, because we do episodes where we talk to people, but also we have other stories that people have written, and we do audio versions of them. But one of them was about the PSP paint.
Nettie Roozeboom: Yeah, yeah.
Host:Tell me a little bit about that, because I know you were involved in it.
Nettie Roozeboom: Yes. Part two, PSP. Yeah. I’m very passionate about pressure-sensitive paint. That’s my job here, is to lead our pressure-sensitive paint measurements. So, this is a paint that glows or fluoresces under UV or blue light. And it sounds really futuristic, something that NASA would work on is this glowing paint. And we apply this to wind tunnel models.
And why would we care about applying this to wind tunnel models? When we’re testing a wind tunnel model, an airplane say, we’re interested in the pressures that are acting over the vehicle. And typically we will, on a traditional wind tunnel test, we’ll have what we call pressure taps on all parts of the model. We’ll have it on the airplane wing, on the fuselage, on the tail. We’re interested in knowing what the pressure is at that very specific location. And so, this is done by having a wing — usually it’s made out of metal, and we’ll drill a small little hole, and then hook up a tube to it, and that tube will go to a piece of instrumentation that will read what pressure it is.
Host:How fast, how much pressure is it sustaining.
Nettie Roozeboom: Right, right. Yeah. And so, that works well. And that’s what we traditionally use on a wind tunnel model. But what happens when you need to know the model on a really thin surface and you can’t drill a hole? Or what happens when you need to have a global distribution of pressure on a wind tunnel model? And that’s where PSP comes in.
Host:How does that exactly happen? So you’re taking a model. You paint it. It’s glowing pink, or it’s pink —
Nettie Roozeboom: Yeah, yeah.
Host:— and you just put it in, run it?
Nettie Roozeboom: Yeah, yeah.
Host:Does it change? Since it’s pressure-sensitive, what happens to that paint?
Nettie Roozeboom: Right, yes. Great question. First we have the model. I will paint the model. And I think this is kind of interesting, because we paint it just like you would paint a car. We put down a primer. We put down a base coat. We sand it, make sure it’s nice and smooth, as much as we can. And then we’ll put on this top sensitive layer. And this sensitive layer has luminescent molecules.
Host:Are you going in with a paintbrush and you’re actually painting the thing, or is it a spray?
Nettie Roozeboom: It’s a spray, yeah. Luckily it’s a spray. I think it would be fairly hard with a brush. I don’t know. Maybe I should try a brush sometime.
Host:It would probably be uneven, I would imagine.
Nettie Roozeboom: Yeah. [Laughs] Yeah. But you do get to be creative. In the top coat there’s these luminescent molecules, and these luminescent molecules you can excite with some kind of energy. And we use blue LEDs.
Host:Like the light shining on it?
Nettie Roozeboom: Yeah, yeah. And we will turn on these lights and point it towards the model, and it will excite the paint.
Host:Thus it glows.
Nettie Roozeboom: Yes. And it will excite these luminescent molecules and make them shine really bright, and they say, “I’m here, I’m here. I’m glowing nice and bright.” But then when you turn the wind tunnel on — you said pressure-sensitive, so what is pressure? Pressure — so in the wind tunnel is partial pressure of oxygen is equal to the partial pressure that’s happening on the wind tunnel model. Maybe a better way to say that is like, pressure is sensing how much oxygen is in the air.
Host:Okay.
Nettie Roozeboom: Actually, the paint is oxygen sensitive, but we’re measuring pressure via the amount of oxygen in the air.
Host:The oxygen that’s pushing on it. Okay.
Nettie Roozeboom: Yeah, yeah. So, where the glowing of the paint will change is when there’s oxygen present or higher levels of oxygen present, i.e., higher pressure; it actually is quenching these molecules and making them shine very dim, so that the model will be very dim in places, and then in other places it will be very bright. And so there’s a lack of oxygen there. So it’s a low pressure there. And with this, we paint the whole wind tunnel model. I have eight scientific cameras mounted around the wind tunnel, and these 40 lamps just zapping away at the paint, and we’re taking images of how the paint is responding when we’re on a certain condition.
Host:How long would you run it for?
Nettie Roozeboom: Yeah. A typical wind tunnel test that I work on will run for 160 hours, so two weeks for two shifts a day.
Host:So it’s just the wind is flowing that entire time?
Nettie Roozeboom: Yeah, and we’ll stop for model changes and of course shut down for people to go home and things like that.
Host:Of course.
Nettie Roozeboom: I guess that’s one of the functions of a wind tunnel, is that you know very precisely what are the conditions. Like, we know what the speed is; we know what the pressure is; we know the velocity of the air. And now we’re measuring the small pressure changes on the wing with these pressure taps, and then, oh, let’s apply PSP. And now we know the global distribution of the pressure on this vehicle.
Host:It’s fascinating because it’s like, you know, from the early days of Ames where they had these wind tunnels, and then as supercomputing became a thing and they had all these sophisticated computer models, but they’ve noticed that, it’s like, even though you can run it in a model, you still almost like — you need to check the answers at the back of the book. And so by putting a real model, they can perfect it on the computer, but then actually put it in the wind tunnel to see is it really correct, and they can learn things that they would’ve never figured out.
Nettie Roozeboom: Right, yeah. And I’m glad you brought that up, because let’s say 20 years ago wind tunnel testing was very different. If you had a design, you had to go to a wind tunnel to understand how it worked. And of course, this is when CFD is coming onboard. But even in my tenure here — I’ve been at NASA almost nine years — wind tunnel testing has changed dramatically. Like, now we do have very sophisticated CFD models, and we understand the flow —
Host:CFD stands for —
Nettie Roozeboom: Is computational fluid dynamics. Yes.
Host:Nice.
Nettie Roozeboom: On a previous cast you talked to Stu Rogers. I work very closely with Stu. And that’s very important — and other CFDers in his branch. But I think the change that wind tunnel testing has had over the past several years is that the tests are getting more complicated. You don’t need to just put in an average plane and run two weeks non-stop, understanding, “How does this react?”
We kind of understand that with CFD. But now when you start having complex flows, like let’s say we have a vehicle named Orion and there’s a launch-abort system, and say we need to get the astronauts away from — like there’s a problem with the rocket and we need to get the astronauts away. Oh my gosh, how do you solve that? That’s super complicated. And we do run CFD, but then we also go into the wind tunnel and run these very complicated tests.
Host:What’s the safest way to do that?
Nettie Roozeboom: Right, right, yeah. And try and understand, like, are we going to abort and just put the astronauts back into harm’s way? So we need to understand how is that going to work. So it’s really advantageous if we can marry all of these technologies. So take CFD, and you know where CFD works really well for you, but you also know where is there some shortcomings. And you also know, hey, wind tunnel testing works really well, but it’s also really expensive and time-consuming, so where do I need to focus? And so if you can marry, like, what do you know with CFD, what do you know with the wind tunnel, and also cross-check each other with that, then you can come up with a really great answer.
Host:Recently, you guys actually ran some tests — was it on the Orion — or on the Space Launch System, the SLS rocket?
Nettie Roozeboom: Yes. We recently had a test campaign for the Space Launch System, and I love it when these large NASA projects come through the wind tunnels. The wonderful thing about NASA is that it’s not one person, it’s not one center, it’s not one division, it’s not one piece of instrumentation. Like, it takes the whole body of NASA to design, build and execute SLS. And so when it gets to come to different facilities like the Unitary Plan Wind Tunnel that I spend a lot of time at, there are so many people there that have so much expertise, and they get to apply their expertise to make this better. It’s everyone from engineers, scientists, mechanics, people like myself — it’s awesome.
SLS was here recently. They tested at our 11-by-11 foot, which is a transonic wind tunnel. And then they also tested at our 9-by-7, which is a supersonic wind tunnel.
Host:Oh wow.
Nettie Roozeboom: Yeah. And I conducted a steady state pressure-sensitive paint measurement for it. And the reason I did that was to give data to the CFDers that are running computations for SLS and help them understand, like, is your answer correct, or how do your loads compare to the loads that I’m computing. So, it’s really great to —
Host:Because it should match. And if it doesn’t, then you’re like, “All right, we’re going to have to look at this.”
Nettie Roozeboom: And also, one thing with PSP is that — I’ve been mentioning, like, global pressure distribution. So you have a lot of information on a tiny little area, and you don’t get that with pressure tap. So, this is really helpful to CFDers because I build a grid —
Host:That’s right.
Nettie Roozeboom: Yeah. I build a grid. They build a grid. And so we have these very fine incremental changes, and we can compare — see, how does their model work compared to PSP measurements, and like where could you refine it?
Host:It’s really smart, because if you think of — you drill the hole, you put in the instrument, the tube. You know where the air is hitting in that one spot. But like, having that paint covering the whole thing, seeing how it changes colors, you get that whole — it’s not just that one little spot.
Nettie Roozeboom: Right.
Host:Because there may be other interesting stuff going on all over it.
Nettie Roozeboom: And its changing intensity, so it’s changing from bright to dim. That’s what we’re measuring. And often we’ll map it to like a color map.
Host:And you’d mentioned the cameras, these crazy sophisticated cameras that are in that wind tunnel all looking at this.
Nettie Roozeboom: Yeah, yeah.
Host:Talk a little bit about those.
Nettie Roozeboom: If I just quickly make one distinction — we did steady state PSP using scientific cameras, and then we also did unsteady PSP.
Host:What’s the difference between steady PSP and unsteady PSP?
Nettie Roozeboom: Great question. Steady state PSP is — we’re on condition for several seconds, so we’re taking data for, say, one to three to six seconds. And so we’re taking that pressure measurement over that time, and we call that a steady state measurement. Everything has kind of come to equilibrium, or we’ve averaged over six seconds.
Now we’re looking into developing unsteady PSP. What does that mean? Unsteady — the pressures are changing. Sometimes it could be 50,000 times per second, or 100,000 times per second.
Host:Really?
Nettie Roozeboom: So with the unsteady PSP, we can measure up to 20 kilohertz, 20,000 times per second. And so we have these high-speed cameras that are measuring the oxygen change.
Host:So it’s like as that paint changes color, depending on the pressure, like, you’re getting very granular images of not only that it changes, but like by how much and when.
Nettie Roozeboom: Yeah, yeah.
Host:Oh wow.
Nettie Roozeboom: And what’s the frequency that it’s changing? And this can be used to compare to aeroacoustics, like taking acoustic measurements. You can also understand, like, are there these low-frequency buffet forces that are acting on a rocket that may cause it to become unstable? So that’s what I’m trying to develop over the next year to help answer some questions that may be involved with SLS.
Host:So, for people who are listening, of course they’re going to go back and listen to the story from earlier, but then also who want to learn more information about pressure-sensitive paint or even just the wind tunnels and what you’re working on, I guess they can just go to NASA.gov, or –?
Nettie Roozeboom: Yeah, yeah. And that story that you’re talking about, if you just say “NASA, Power of Pink,” that will come up.
Host:Excellent. For anybody who has any questions for Nettie, we are on Twitter. We are @NASAAmes. We’re using the #NASASiliconValley. This is awesome. Thank you so much for coming.
Nettie Roozeboom: Yeah, my pleasure. Go NASA.
[End]