EPISODE 161: NASA’S ZERO GRAVITY RESEARCH FACILITY

Transcript

[SFX background chatter and movement inside a spacious building] 

Andres Almeida (Host): There’s a building at NASA’s Glenn Research Center in Cleveland that looks ordinary from the outside, but inside, it holds one of the most unique laboratories in the world: the Zero Gravity Research Facility. It’s essentially a drop tower that extends 510 feet below the ground, and it’s the largest of its kind in the world. Here, researchers can drop experiments, including test spacecraft, in a vacuum chamber for a fraction of what it would cost to do in space.  

[SFX thud sound] 

Let’s dive into it in this episode of Small Steps, Giant Leaps.

[Intro music] 

Welcome to Small Steps, Giant Leaps, the podcast from NASA’s Academy of Program, Project and Engineering Leadership, or APPEL. I’m your host, Andres Almeida. 

Today, lead mechanical test engineer Vittorio Valletta is here to talk about how the Zero Gravity Research Facility has supported decades of breakthrough research and why simulating microgravity on the ground is critical to advancing human space exploration. 

Hey, Vittorio, welcome to the podcast. 

Vittorio Valletta: Hey, thank you so much for having me. I really appreciate 

Host: Can you explain your role? 

Valletta: I am a mechanical test engineer for the Zero Gravity Research Facility, so my job pretty much entails setting up all the tests, coordinating with researchers, with what kind of testing they want to get done, scheduling the tests, you know, during the week, during the year, working with the facility manager on figuring out, financially, what type of tests we can run, and getting cost estimates for new work coming in, and then just making sure that the tests are done safely, getting as much data out of them as possible. 

As a test engineer, we’re not really looking for the data itself. We’re not going to be the ones analyzing any of that stuff. So what we’re pretty much looking at is, when a researcher comes in, you know, what kind of data are they looking to get, and then, with the constraints of our facility, what kind of testing can we design to meet as many needs as possible within a budget, and hopefully get them the data that they want, and do that all safely. With, you know, some stuff that we’re working with, there are a lot of hazards associated, so we want to make sure that we can go through all the safety processes correctly. And that also is one of the jobs that I have to do. 

Host: What capabilities does the research facility have? 

Valletta: So, I guess a little bit of background on the facility itself: The way that we can do zero-gravity research or testing, or microgravity testing on Earth, is you need to be able to put an object in a state of free fall. So, our facility, specifically, it’s a 460-foot steel vacuum chamber below the surface that we drop our hardware (our test hardware) 430 feet in free fall to create 5.18 seconds of microgravity time, which doesn’t seem like a lot, but it’s a lot more than you think, especially for the cost considerations and everything like that. 

Basically, we run in a vacuum to get rid of air resistance, and we drop our vehicles in free fall to create that micro gravity environment. Some of the capabilities that we’re able to do a lot of, because it’s run in a vacuum, we need to run inside of pressure vessels.  

So, we have a few different rigs that operate differently. Again, most of the stuff that we’ve done lately is combustion and or fluid physics. A lot of the pressure vessels are centered around those types of tests. So with, you know, one of the rigs, it’s only able to get up to about atmospheric pressure, but it’s a flow tunnel in which we will blow across a sample, maybe like a cotton fabric, or, you know, other types of samples that, where we’re trying to see how it reacts in a combustion atmosphere, whether it’s, you know, at low pressure, at a specific oxygen concentration, to see where potential flammability limits are. 

We have another rig where we’re able to do up to 5,000 psi [pounds per square inch] and 1,000 degrees F, which is very high pressure, high temperature. A lot of that is for combustion that you might see in, like, a diesel engine or a rocket engine, jet engine, stuff like that. And also, like fluid injection in that same rig to do high-pressure fluid injection and see how the fluid physics change in its super critical state. And then the most unique capability of our facility is to do partial gravity. That one’s kind of a unique one. 

So, the way that that one works is the pressure vessel itself will rotate and spin, and at a certain rate of rotation and position from the center of the position of rotation, the distance from the center, the radius, you can create an artificial gravity. So basically, if you think of, if you’ve ever been on like the Gravitron rides at amusement park, where they spin, and you kind of get pinned against the wall, it’s the same kind of concept. So, at the certain speed, speed and our rate of rotation and distance from the center, you’ll get a,a centripetal force that points towards the center of rotation, and that force is how we’re able to create partial gravity. 

So, on Earth, if you have something spinning, you have that force pointing inwards. And then you also have gravity. Well, when we’re dropping, if you get rid of that, that gravity vector, because we’re in microgravity, then the only thing you have left over is a gravity vector pointing inwards. So again, it’s very specific, and I’ve mentioned it twice already, but certain speed of rotation and a certain distance from the center, we can create artificial gravity. 

So, if we’re doing like Martian or lunar, anywhere, basically from zero to 1g, we’re able to have the capability of doing that partial gravity testing to kind of get an idea for, you know, especially for like flammability limits, how do things react in, like, lunar gravity? That’s something we’ve actually been actively looking at for, like lunar habitat stuff. 

Host: So then, you can get enough data in five seconds? 

Valletta: So, a lot of the data is high speed video, so if you’re operating at 150 frames, and then you have two seconds before the drop, where you’re getting some of the ignition data. And then you have the six seconds of the, of the drop, plus the little bit after. You can get a lot of data in that and then, based off sampling rates for actual data, whether it’s temperature or pressure or anything like that, you can get a lot of data at a high sampling rate. 

But to get an idea of how things burn differently, because scientists and researchers have kind of found that there’s this kind of weird Goldilocks zone that they call it, where things are burning in lunar gravity when they don’t think it should, which is kind of changing the way that scientists think of what kind of materials they want to build these lunar habitats with once we eventually go there. 

So that’s kind of been, like I mentioned, a big proponent of a lot of the testing that we’ve been doing, especially in this last year. 

Host: What did you and the team see, as far as how a flame behaves in space, which is important as we prepare to send humans into deep space (out to the Moon and beyond)?  

Valletta: Let’s say you have, like, a candle. And you light a candle. If you hold that candle straight up, or you hold it to the side horizontally, you’ll get this teardrop shape of a flame. That happens due to convection. 

As you heat up the air, you get this less dense, hotter air, or the particles are moving faster, and left behind is this colder, more dense, heavier air. That heavier, more dense air is pulled on by gravity. And what ends up happening in this case is you get this naturally occurring cycle where you’re re-oxygenating the flame to keep breathing, because one of the things you need for a fire in the fire triangle is oxygen. So, convection basically keeps continually feeding fresh oxygen to the flame to keep breathing and keep burning, as long as there’s a fuel source. 

In zero gravity, there’s nothing to pull down on that more dense, heavier air. So, what ends up happening is, if you lit that candle, that teardrop shape is no longer there, and you end up having this very spherical shape that is very dim and very blue. And what ends up happening is if there’s no additional source to continue feeding the flame with oxygen, it’ll actually suffocate itself and self extinguish. There could be potential for more danger around the flames if they do have a[n] external source on them. So, a lot of testing, you know, in the facility in the past 20-25 years, has been around ISS safety and flammability extinction. 

If you can imagine, ISS is surrounded by air ducts and air vents that are blowing out, you know, 21% oxygen standard atmospheric pressure, what we live and breathe today. And if a fire were to ever break out on ISS, how can we attack it? Because you can’t just take a standard house fire extinguisher up on ISS and expect it to work. So, what kind of flame extinguishing methods can we do to eliminate that? And then, what kind of materials can we put on ISS and have we put on ISS to mitigate something burning. So, what materials burn worse in a zero-gravity environment at standard atmospheric conditions?  

And that’s kind of transitioned now to where we’re doing research into, like, the lunar habitat, because that’s going to actually change from what they’re expecting from, like, the lunar habitat compared to ISS.  

Yeah, I mean, so far, a lot of good data has come out of it. There’s plans for testing in the future to eventually send stuff up to the Moon and kind of prove that what we’ve been doing is valid, and, and vice versa for our stuff to best, best suit what we’re going to send up so that it’s, you know, it’s worth the cost of what we’re sending to the Moon. 

Host: And it must be interesting because you don’t fully know until you get to the Moon, right? 

Valletta: Exactly. It’s based on data. But we won’t, you’re right, we won’t know until we actually have physical data on the Moon. 

As a test engineer, I just want to make sure that the test gets done. It gets done safely. All of the data that they get is appropriately done and its quality, right? It’s, it’s as repeatable, as controlled as possible. 

Host: Just briefly, what other notable research has been conducted on there? 

Valletta: Some of the big ones that have been done in the past, way before my time, which are pretty cool, were a couple jobs that were done for the Apollo programs. 

So around, you know, the mid-1960s, the engineers were trying to figure out a way to solve the problem of restarting the service module propulsion system when they were, like, on their way to the Moon, right? And a lot of the struggles were around the surface tension of the fluid inside the tank. 

So, you know, you can imagine, if you had a gas tank in your car, right, the fluids are all going to be sitting at the bottom of the tank. So, you know that the fluid is always going to be at the bottom no matter where you are. So, if you wanted to, you probably put a fuel pump right at the bottom. That’s not how they obviously operate, but you could, because it could just be gravity fed, and that’s really easy. 

Well, in deep space, and you’re just kind of on your way coasting, you know, where’s the fluid? Is it going to be near the pump enough that when you go to start the engines that you’ll have fuel ready to burn or is it just going to be floating wherever it wants to float (which is the case)? 

So, they did a lot of surface tension fluid studies in the beginning to design a retainer to hold enough fuel close to where the engine would need to be fed in that tank. So that way, when they when they needed to start their engines, they could and, you know, when they were in deep space, if they if they needed to refire them, they would be positive that they could get ignition. It wasn’t just like they were going to be at a complete guess. So that was like one of the big projects in the beginning of the life of this facility. So that was critical to the Apollo Program.

The second one, very similarly, there was a problem with the Saturn third stage rocket. When the engine would shut down, similarly, they actually used, like, hydrogen peroxide thrusters. And basically, during coasting, the propellants were maintained at the bottom of the tank by the thrust obtained when the boiled-off gas would be ducted through small thrusters. 

Host: And you’re talking about the Saturn V?  

Valletta: Yes, the Saturn V, correct. And so, there were studies done at this facility to kind of determine the proper size of those thrusters. So again, that they could, when they needed to use them. They could, could ignite them and continue on their way. So, a lot of fluid physics was done early on at the facility. We’ve definitely shifted to combustion now. 

And again, like the research that we’re doing is still really valid. It’s, it’s, you know, aiding in our mission back to the Moon. So, it’s kind of, it’s kind of funny that, like, we’re going back to the Moon, we’re still doing really critical drop data.  

Host: Can you share any lessons learned from your time as a test engineer or your career at NASA in general? 

Valletta: For me personally, I’ve struggled a lot with imposter syndrome, and I think a lot of people are in the same boat, they just don’t voice it. And, you know, I’ve always struggled knowing, like, if I was good enough to be an engineer, if I was fit to be in the positions that I’ve been in. And the one thing that’s always been, you know, in the back of my head is, you know, just work hard. Work hard. You know, ask, ask questions, make sure I’m doing my due diligence to learn, even if I don’t know it, to try and learn. 

For me, personally, kind of proving to myself that the effort that I put in, whether it’s, you know, the extra time, or, you know, trying to solve problems that maybe haven’t been thought of because they’ve been around forever, and everything’s working – that doesn’t mean it’s the most efficient, right? So, trying to improve facility capabilities, trying to aid in any, any design that of things that may be outdated, instead of, you know, just assuming the norm. 

And working like I said, really hard, just putting your nose down as soon as you get into work, and grinding and kind of proving to myself that like, hey, I do belong. The position that I’m in now is because of the work that I put in for the past six years, right? That’s very rewarding. And that lesson that if you put in the work and you put in the time and the dedication and the energy and the emotion you will eventually get rewards. Someone will see what you’re doing in the effort that you’re putting in, even if you don’t think someone’s noticing it every day. In the long term, you know, it will show up to those around you. 

So that for me, has been really rewarding and kind of eye opening. 

Host: What do you consider to be your giant leap? 

Valletta: Probably the biggest leap for me, which wasn’t necessarily like a very risky leap, or anything like that, but one year ago is when my former mechanical lead ended up retiring from the facility, and I had been at the facility at that point for six years now, kind of studying under him, learning under him, taking in all the knowledge that I could. And then eventually, when they opened up the position to replace him, of course I was going to apply with the hopes that I would be able to get the job with all the knowledge that I did have. And, you know, that was really scary. 

There were so many things that, you know, when I started that I had to learn kind of learn on the fly that, like, he didn’t necessarily shield from me, but he was taking care of those projects while I was taking care of other stuff. So, there was a lot of learning very early on to get into kind of that leadership position and to be more open to, like, delegating tasks now, instead of being the one that was delegated, to owning the projects, more being the main point of contact, being the one that is, you know, assisting in the engineering design estimates and cost estimates for people coming in to do the testing. Basically, being the lead mechanical engineer in the area that I’m in now was a was a very scary and very huge step for me. 

And it all happened at the same time that I had my one-year-old child. He was just born, like, two weeks after I took on the role of leads. So, it’s a very hectic time for sure, so that kind of added another layer to taking that, that leap, right? And it’s not that I wasn’t ready, right? I felt confident. I knew what I was getting myself in for, but it was definitely scary knowing, like, I’m the guy now, I’m the point of contact. I’m the one that everyone’s going to be coming to for answers. So, I’m obviously grateful to be in that position. And, you know, be talking to you about it, it’s, it’s really humbling. 

Again, I have to kind of remind myself that I put in the work to get here, but I don’t take it for granted one bit. I’m super appreciative to be in the role that I’m in, in the facility that I’m in. To get the to do the work that we do on a daily basis, it’s really rewarding. I have to pinch myself when I come into work every day. When I was a kid, all I wanted to do was work here, and I didn’t know I’d be doing microgravity research. I thought I’d be working on rockets, right? But nonetheless, it’s, it’s very rewarding to be able to work here and, you know, see the reaction out of scientists when we’re getting the data that we are, which a lot of the times, is groundbreaking. It’s stuff that’s never been tested before. Like I said, I know I said “rewarding” like eight times now, but it truly is. 

Host: Well, thanks for your insights, thanks for your time, Vittorio. 

Valletta: Thank you so much. I really appreciate it.

Host: That’s it for this episode of Small Steps, Giant Leaps. For more on Vittorio and the topic we discussed today, visit our resource page at appel.nasa.gov. That’s A-P-P-E-L dot NASA dot gov. And don’t forget to check out our other podcasts like Curious Universe, Houston, We Have a Podcast, and Universo curioso de la NASA.