International Space Station Flight Director Royce Renfrew discusses the complexity of the orbiting laboratory as NASA counts up to 20 years of continuous human presence in space.
ISS is a major engineering feat that has pushed the boundaries of human exploration and problem solving – representing the most complex space exploration program ever undertaken. Over the past two decades ISS has evolved into a unique microgravity laboratory with about 300 active investigations during each crew rotation and has built understanding of how humans can safely live in microgravity, made groundbreaking advancements in medicine, and tested technologies that will further space travel. In the second segment of a two-part series celebrating the 20th anniversary of continuous human presence in space, Renfrew shares experiences and observations from the perspective of a flight director.
In this episode of Small Steps, Giant Leaps, you’ll learn about:
- ISS complexity
- The importance of international collaboration on the space station
- The significance and impact of ISS on humankind
Related Resources
International Space Station Facts and Figures
Episode 46: ISS 20 – Living in Space
Remote Manipulator System (Canadarm2)
APPEL Courses:
Complex Decision Making in Project Management (APPEL-vCDMPM)
Leading Complex Projects (APPEL-LCP)
International Project Management (APPEL-IPM)
The Best Teams: Introverts, Extraverts and Ambiverts (APPEL-vTBT)
Royce Renfrew serves as International Space Station Flight Director and is the leader of the ISS flight control team responsible for pre-flight mission development and real-time mission execution. Renfrew also serves as Artemis Flight Director and leads the NASA operations team working with the SpaceX/Starship vehicle team for potential final selection as an Artemis Program lunar lander. He has held NASA flight director or flight controller positions for almost 20 years. Renfrew was a high school mathematics, computer science and history teacher before joining NASA’s Johnson Space Center in 1997 as an ISS Robotics Instructor in the Mechanical and Robotics Systems Group. He has bachelor’s degrees in computer science and history from Trinity University.
Transcript
Royce Renfrew: That’s the legacy I think that’ll be most relevant coming from the space station is the international cooperation. It’s the I in ISS.
It’s a monstrously complex vehicle.
You name the system, there has been an evolution in there about how we actually operate that system on board station. And that’s been the most fascinating part from a pure flight controller perspective to watch that evolution over the 20 years that we’ve been there and to imagine what that would look like 20 years from now, something I probably couldn’t even recognize.
Deana Nunley (Host): Welcome back to Small Steps, Giant Leaps, a NASA APPEL Knowledge Services podcast featuring interviews and stories that tap into project experiences to share best practices, lessons learned and novel ideas.
I’m Deana Nunley.
We’re approaching 20 years of continuous human presence in space on the International Space Station. Today, we’ll conclude our two-part series – ISS 20. In the first part – Episode 46 – we talked with NASA Astronaut Tracy Caldwell Dyson about her experiences living and working aboard the ISS.
Our guest in the second segment of this series is longtime ISS Flight Director Royce Renfrew. Royce, thank you for joining us.
Renfrew: Thanks for having me. Happy to be here.
Host: ISS has been part of your career with NASA for many years. Would you share with us your story and how you currently support ISS?
Renfrew: Sure. Happy to. Let’s see, coming up on 24 years at Johnson Space Center, the majority of that as a civil servant. I started out there as a contractor years and years ago. United Space Alliance was looking to expand their instructor corps from just a bunch of mechanical and electrical, et cetera, engineers, to folks who actually had some background in education plus a technical degree. And believe it or not, one of the reasons I got the job is because I was a high school math teacher for seven years and had a degree in computer science. And that was one of the reasons they thought I would be able to do good at the job. I started out there before the first element flew, and I trained the Expedition 2 and 4 crews how to operate the robotic system onboard the space station, the Space Station Remote Manipulator System, or SSRMS.
Part of the rationale they hired me for that as well is because I put myself through college as a heavy equipment operator, so I had the hand-eye coordination that was necessary to do the job. I had several different jobs out there. From being an instructor, I transferred to be a flight controller in the ROBO group and then I transferred out of there, which was a specialist position. I transferred to a group that doesn’t exist anymore called ODIN, which was one of the core system flight control positions that manages the computer system on board the space station. And I was the first line group lead for ODIN when I was selected as a flight director in 2008. Been out there for a very long time, I’m currently in the Flight Director Office.
The other hat that I wear in the Flight Director Office is as one of the flight directors who is working on Artemis. in particular, I’m working the Human Lander System, or HLS, portion of Artemis where we’re currently competing with three different companies, settling that down to two, to select the two companies that will take the crew down to the lunar surface and support them while they do spacewalks. Unfortunately, because that’s still somewhat of a competition, I really can’t tell you too much about what I’m doing with Artemis.
Host: Okay, well, we’ll try not to pry too deeply here. From your perspective as flight director, what’s most remarkable about 20 years of continuous human presence on the ISS?
Renfrew: It really is a remarkable accomplishment when you really step back and look at that. My daughter is 24 years old — it’s one of the reasons I can always remember how much time I’ve spent out there. But for the vast majority of her life and the entirety of a lot of people’s lives, there’ve always been human beings that aren’t living on Earth. They’re out there on the space station. We’ve had a continuous presence out there on the space station for coming on 20 years here, really close. That I think is one of the most interesting things about the space station is the continuous human presence. The fact that we’ve had all earthlings are not on Earth. The fact that we have representatives from countries all around the world who have been there from Japan to Russia, to Germany, the United States, obviously. We’ve had Canadians. A large number of countries around the Earth have flown crew members to the space station through either the Russians or us.
But that’s the legacy I think that’ll be most relevant coming from the space station is the international cooperation. It’s the I in ISS. It’s the International Space Station and we do have people on board the station and have been there and little boys and girls that live somewhere in some country that I have never been to can turn on the news at night and see their hero or read it in the paper and maybe inspire or set that spark in their mind that something in engineering or they want to be an astronaut or they want to be a flight controller. Maybe that’s something that I can contribute to the human spaceflight program generically by supporting those folks on board. I think that’s the most interesting thing that you get out of the space station is the international cooperation that allowed us to get there.
Host: How has working on an international program enhanced you and your team’s experience supporting ISS?
Renfrew: It’s been a very interesting experience. We haven’t always seen eye to eye with our international partners. And I think if you asked them, they would say they haven’t always seen eye to eye with us. But once we, as a community came to understand that we’re all really driving for the same end goal to expand humans’ presence in the solar system — we just go about it in different ways or we have different approaches to how to do flight control or we’d have different approaches on how to do training. What I think I and the rest of the team really got out of that relationship is a growth in our own ability to operate in space because obviously we don’t do everything perfectly and there are a lot of people who do things better than we do. And the ability to see somebody generate a procedure or execute some type of commanding or build a tool to generate timelines or what have you, amongst our international partners, we all learn from each other. When you broaden the input availability and the number of really smart people who are contributing to the program, everybody gets better.
I’m sure they’ve learned stuff from us and we’ve learned stuff from them. I honestly believe that when we go to Mars, it’s going to be an international program. Leveraging on what we have done on board the space station with our international partners, for these two decades now, to leverage that into designing and building a mission that’s going to allow the human race to go to Mars or build a colony on the Moon or a Deep Space space station or what have you, I think that benefit from the International Space Station will be immeasurable because we won’t be starting from scratch like we did with the space station.
Host: Could you walk us through some of your experiences and what you’ve observed as the space station has evolved over the past couple of decades?
Renfrew: Okay. Like I said, I started out as a robotics officer. The Canadian Space Agency, CSA, contributed the Space Station Remote Manipulator System and the Special Purpose Dextrous Manipulator. When we first started with the fledgling space station and the arm arrived there on the ISS-6A flight, we really only had the arm and we knew how to operate it, but we didn’t know how to operate it as we do today. And when we first got the arm on board, every time you wanted to operate that system, crew had to move it. We designed procedures for the crew and we verified all the trajectories and we understood all the forces and moments and how much the arm could take and how fast it could move and we did all that legwork for them and then produced a procedure for them to go execute it. And they did that.
In today’s world, the crew hardly ever touches the SSRMS, except to do grapples of free flying cargo vehicles. But the rest of the operations for that system is done from the ground, either from Houston or from Montreal, with the flight controllers doing those activities remotely. They are actually operating the arm from Houston or from Montreal, doing all those maneuvers. The crew to my knowledge has never actually even operated the Special Purpose Dextrous Manipulator, the SPDM. And we use that all the time to change out broken hardware or do this survey or a number of closed doors on payloads. We’re doing a number of things with the SPDM. The point there is that where we started from and where we are today has evolved greatly over the years. And the same thing holds true for all of the systems on space station.
I remember being a robotics flight controller on console for some shuttle mission. When the shuttle arrived there, the flight, it had suffered a failure going uphill and did not have its vernier jets available. It only had its course jets available. Per the flight rules, going into the mission, the step down from shuttle vernier jets was to use a Progress or a Soyuz, I don’t remember which one it was. It must have been a Progress — jets to maneuver the ISS backwards, which is the way we always flew with shuttle missions. And it took us the entire Progress vehicle worth of fuel to do that. And today we can, we’re very smart about how to do those things. We can actually translate or rotate the ISS 180 degrees using just a pittance, maybe 11 or 12 kilograms of prop because we do these things called zero prop maneuvers. The point is that’s another evolution.
We went from having to fly all of our water up to recovering 80 percent of the water on station that we do today. The CD8, the Command and Data Handling System has evolved to where we have new processor cards. And you name the system, there has been an evolution in there about how we actually operate that system on board station. And that’s been the most fascinating part from a pure flight controller perspective to watch that evolution over the 20 years that we’ve been there and to imagine what that would look like 20 years from now, something I probably couldn’t even recognize.
Host: Thinking about the complexity of ISS, how would you characterize the magnitude of the space station and what it takes to keep it operating with humans living and working in space 24/7 year after year?
Renfrew: Yeah, it is very complex vehicle. It really is. And the complexity is increased obviously because of the international component. We have to match up all of those systems on one international partner’s element to another international partner’s element so the code that some person here in the United States writes and the code that somebody in Japan wrote, have to talk to each other. When you get down to engineering and computer science, it’s probably easier to do that than it is to do it with the humans talking to each other, but it is a hugely complicated vehicle. And what we try to do with the ISS is manage all of it from the ground. We fly it. We keep it pointed straight and level or backwards and upside down, depending on what the case may require. We make sure the air is breathable and the water is drinkable and the toilet works and all of those things that would normally have to be done by the crew member on board, let’s say the shuttle, we do from the ground and what that enables is the crew to do as much science as they possibly can.
And that’s really been the biggest evolution that we’ve had for ISS is going from a vehicle that we were assembling until we got to the point where we called it assembly complete even though we still added a few more modules and updated a few things. But at assembly complete, we started looking at how to do scientific research on the vehicle. That’s what we use the crew for — do as much scientific research as they can hands-on and then every now and again, help us out because we need somebody to turn a wrench or throw a switch or check a circuit breaker or something, power cycle a laptop that we can’t actually do from the ground.
You take all of the complexity of the vehicle and you add five international partners and control centers all over the world, the vehicle itself is complicated, the systems we have developed on the ground to be able to coordinate the operations between all of the control centers adds to that complexity. I really think it is a hugely complicated vehicle. Fortunately, you never really hear a whole lot about space station anymore. You used to a lot, when we were building it. Had a lot of failures, but we really know how to much better about how to operate the vehicle now so you don’t hear a lot about ISS in the news anymore because — the complexity — we have managed to start getting our hands around the complexity of the vehicle and understand how it actually operates in orbit.
Host: Royce, what’s it like to be a flight director and to be that person who is ultimately responsible for the wellbeing of humans in space and the orbiting facility that keeps them safe and provides valuable science for our planet?
Renfrew: Being a flight director is eight hours and 45 minutes of not doing a whole lot, followed by 15 minutes of sheer terror often. It really is. It’s staggering sometimes when you allow yourself to think about the responsibility that you have, the six human beings that live on board the space station whose lives are literally in your hands when you’re sitting in the control center at the flight director console. That’s where the buck stops. There is no other option. The flight director has to make the calls in real time. Those are the agreements that we have with the program, by the way. And those are the same agreements we’ve had with all programs that NASA has flown in the human spaceflight program, is that the flight director is authorized to take any action that he or she deems necessary to save the crew or their vehicle or to complete the objectives of the mission.
That’s an awesome amount of power and an awesome amount of responsibility. But I will tell you that even though I shoulder all that when I go on console, what enables me to do that are the people who surround me. The people who are sitting at those consoles around me in ETHOS or the CapCom that’s sitting beside me, or the EVA or spacewalk officer who’s sitting behind me or the ground controller who’s operating the building. I am heavily reliant on all of those individual console operators at any time I’m in that room. It’s we talked about the complexity of it earlier. It’s a monstrously complex vehicle.
There is no way that a single person can operate all of it. Not even the flight director. The flight directors don’t know everything, which sometimes surprises the junior flight controllers, but I am very much dependent on the junior and senior flight controllers in my room and the flight controllers in Munich and those in Tsukuba and those in over at the TsUP in Moscow, all of those folks who are professional flight controllers. It is their job to monitor those systems and control the vehicle under the direction of a flight director sitting there. And the flight director in Houston is the person that is the last gasp. The person who has the last say on how something is going to occur is that person that’s sitting in that flight director console in Houston.
Host: What are some of the key lessons learned from ISS that you think could be difference makers for program and project managers across the agency?
Renfrew: I think it’s very important for people to understand going forward in what I envision as a renaissance of space exploration in this century where we really start looking to the Moon, we start looking, we have a space station that’s been there for 20 years, maybe we build another one. We’re going to go build a facility on the Moon. More than likely we’re going to go build a facility on Mars where people can live their lives for long stretches at a time. The biggest lessons learned that I would take away from ISS being able to do that is it’s not the hardware, it’s not the software, it’s not the whizzbang new drive that we’ve developed for some spacecraft. It literally is the people that make that happen. It’s the people that work for the program. It’s the people that work for flight operations. It’s the people that work in the engineering directorates and that do all the tests and the analysis.
I can’t go do something that’s as outrageous as build a habitat for someone to live on the surface of the Moon for extended periods of time and not be in excessive danger without that person who did all those tests on that software, who did all those tests on that processor for the O2 system or that water system or that toilet system or whatever system you want. That’s the biggest takeaway. It’s always going to be the people and that’s what we should recognize going in and do whatever we can as managers to enable the people to do their job quickly, successfully, efficiently, and have all the materials and communications links as flat as we can get it communications lines.
Let them do all that vertical integration to us, but make sure they have the ability to do all that horizontal integration to all those other people that are doing all those other things. That’s the most important. That’s the biggest takeaway I think I’ve got out of working in the space program, period, is that one of the things they say at JSC all the time is that it’s the people that make us fly and that is absolutely true.
Host: When you reflect on the ISS team and success stories over these 20 years of continuous human presence, what are a couple of your favorites?
Renfrew: One of the favorite stories I have about ISS generically, or tying the last conversation that I had talked about, people into that conversation, Houston several years ago, had the ill fortune of being on the dirty side of a hurricane named Harvey that came in well south of us and we all thought that we were going to get a little bit of rain and that was going to be okay because it was going to come in south of us and we weren’t going to get the brunt of the hurricane force winds in Houston. As it turned out, it did come in south of us and the folks down south of us really got battered by those hurricane force winds. But what Harvey did was set up a chain of rain bands that effectively rolled right over the city of Houston and Clear Lake, Webster, where Johnson Space Center is, effectively straight up Interstate 45 from Galveston to Houston, just got rained on perpetually for five days.
And it was a huge event. Everybody in Houston was somehow impacted. We had hundreds, if not thousands, of houses that were flooded and cars that were stalled. And it was just a mess. As it turned out, there was a flight control team in Mission Control in Houston, because we literally had not anticipated that Harvey was going to be that bad. We have a bunch of protocols that we use during hurricanes, where we send people to Marshall to stand up a backup control center if we need to, et cetera for a hurricane. And we’ve exercised that a number of times over the years, but because of what we thought was going to happen with this hurricane, we did not exercise that protocol because we thought we were going to get some rain and it was going to be bad, but it wasn’t going to be terrible. No one ever expected the 500-year flood.
We had a group of flight controllers who were in Houston in the control center and we actually had enough flight controllers there to stand up two different teams. Each team was executing 13-hour shifts with a one-hour handover in between perpetually. We normally have three shifts a day, so we were down to just two. And they were literally sleeping in the control center because they were trapped there. The only way that they’d get out of the control center is with a high-water vehicle. And my house is close enough to the control center that I managed to ford some of the streams and get there in my high-water pickup and I spent some time with those folks.
And I have to tell you the only time in my entire career at NASA that I ever saw the white flight control room — where we used to fly the shuttle all the time — the only time I’ve ever seen that room completely powered down was during this event where they turned off all the lights and the clocks and the whole nine yards and went in and put in cots between the consoles there, where people could come off console and grab some sleep before they had to go back on console 12 hours later. And to me, the fortitude and the professionalism of the people who did that during Hurricane Harvey just really demonstrates the caliber of people that NASA attracts. They weren’t complaining about the fact that they were scavenging out of the vending machines. Nobody had a place to shower for five days. We finally found a building close enough that people could walk to, they could go over, take a shower, but they didn’t have any clean clothes with them because they were trapped there.
But there wasn’t any complaining about this or complaining about that. They just did their job. And I think the really telling piece of this relatively long story and I apologize, is that the crew did not know that the flight controllers were trapped in Houston. One of the flight directors who was on console happened to be friends with a kindergarten teacher, first grade teacher or whatever it was, and they were communicating back and forth about what was going on. And they were trapped in the building, et cetera, et cetera.
This kindergarten teacher had all of her students make some really adorable little cards for the flight controllers, saying, ‘Thank you for keeping the astronauts safe and I’m sorry, you can’t get out of the building,’ and blah, blah, blah. And sent them all to this flight director who then turned around, she thought they were adorable. She turned around and sent them up to the crew on orbit. And a little while later, somebody opened their email and called the flight director console and said, ‘What does this mean? You guys have been trapped on console for the last five days?’ And she had to confess that that was true. They couldn’t get out of the building.
But I think that is completely indicative of the professionalism of the people that NASA attracts. The timelines were not any different. The commands were coming up and when they were expected. The crew was still executing. They were doing science. They were doing in-flight maintenance. They were doing whatever tasks needed to be done on board the station at a rhythm and a pace just like we had when Harvey wasn’t there. One of my favorite stories about NASA in general is that story about the flight controllers who did their job so well the crew couldn’t even tell that they were having a problem.
Host: How would you summarize the significance of ISS and its impact on humankind? Do you find that people understand the significance of ISS?
Renfrew: I don’t. I don’t think that the public at large really has a good understanding of what ISS is and what ISS does for them. There are literally hundreds of scientific experiments or longtime, long-duration research projects that are being conducted on board the space station every day. Some of them involve the crew, some of them are outside. You have a really fascinating payload on the outside called the Alpha Magnetic Spectrometer that is trying to find dark matter in the universe. It’s a collaboration by a bunch of astrophysicists that work out at CERN in France that have a collaboration with hundreds of like-minded scientists around the world and built and we flew this piece of hardware called the AMS and put it on the outside of the station. And we’re looking up to see if we can discover dark matter. And the crew members on board the station are perpetually using themselves as research subjects. We’re looking at osteoporosis and how vaccines could be generated. Salmonella actually mutates incredibly fast on board the space station, which allows researchers to really understand that particular bug. And it’s not the only one that mutates fast, something about being in a zero G environment that does that.
And we’re also spending a great deal of time looking down on the Earth from a very unique perspective with human beings taking pictures or robotic cameras taking pictures or various instruments that are looking at wave heights and ozone concentrations and deforestation or the growth of Phoenix, Arizona, for the last 20 years, because we fly over it every couple days and we can take pictures out of it.
I think the population at large really doesn’t appreciate or understand what the ISS is trying to do for them. And I think that primarily comes from the fact that we don’t launch things. There’s no fire and smoke at Kennedy with a vehicle lifting off the pad. We just go around the Earth 15-and-a-half times a day, traveling 17-and-a-half-thousand miles an hour every day for the last 20 years. And if something doesn’t break on board station or one of the crew members is not doing a public affairs event with their hometown high school or something, public at large really doesn’t know we’re there.
And I’ve had a number of people over the years express alarm that NASA still exists and tell me that I can’t believe Johnson Space Center is still there after the shuttle stopped flying. What have you guys been doing for the last umpteen years? And that’s always disheartening. I don’t know how to solve that problem, but I do know that station long after I’m gone, they’ll still be figuring out answers from the research that is going on on board station today.
Host: What do you anticipate as the future of ISS?
Renfrew: One of the things that we have been working on diligently is what’s referred to as the commercialization of low-Earth orbit. There are a number of contractors out there who are looking at adding elements to the space station that the contractor buys and builds and flies and we attach to space station that allows them to use the space station as a platform with the power and data and video and all the resources that they need right there, but then they can add their element to do whatever scientific research that they want to do. There are a number of entities out there that are doing things like talking about flying civilians to the space station. I’ve seen that in the news a couple of times.
It is my belief, and maybe I’m paraphrasing a bunch of folks who have said this, is what NASA needs to do is get out of low-Earth orbit, the business of low-Earth orbit, and turn that over to commercial partners, commercial entities, maybe eventually someday actually turning over the ISS to some commercial entity to continue operating and redirect those funds that NASA is currently pouring into the ISS to pushing the envelope out to the Moon, out to Mars, maybe another, the Gateway Space Station we’re talking about orbiting the Moon or maybe there’s something in one of the Lagrange Points that we need to build. Something. I’m not sure, but I do think that we have demonstrated enough over the years that people can fly safely in low-Earth orbit and we should turn that over to commercial elements and do things that governments need to take the risk on rather than companies.
It’s a very risky proposition to fly somebody to the Moon. It really is. Yes, we did it a long time ago, but now we want to go back to stay and that is a very risky proposition and that risk pales in comparison of flying people to Mars and maybe building a habitat on Mars where we can stay. I think, do the Moon first, get comfortable with that, go to Mars and eventually turn over the Moon to those commercial entities and eventually turn over Mars to those commercial entities so we can go look at things like the moons of Jupiter or move farther into the solar system. I think that’s the progression that we need to go through. And I think we’re going to see that first step when more commercialization of low-Earth orbit occurs.
Host: Royce, it has been so enjoyable having you on the podcast. Thank you so much for joining us.
Renfrew: I am happy to be here. Thanks for having me and asking a lot of good questions. Hopefully folks got some insight.
Host: Oh, I’m sure that they did. I know I did, and really do appreciate it. Do you have any closing thoughts?
Renfrew: I have done this for a very long time. I was thinking about the other day, I’m almost 60. I’ve spent a large portion of my life involved in the brand that is NASA. I think that it is recognized worldwide as the really cool people, the science folks that work at NASA. One of the things I always tell young flight controllers that come to work out at JSC is that they should take a vacation at least once a year where they travel at least 100 miles away from Johnson Space Center, go home, go someplace they’ve never been, go to a breakfast place or go to go to a bar sometime in the evening. Then eventually somebody is going to ask them what they do for a living. And when they say they work for NASA, that’s going to be the start of a conversation because you can’t tell someone in the United States, anyone, you can’t go anywhere in the United States and say, ‘I work for NASA,’ and have that person shrug their shoulders and say, ‘Well, that’s cool.’ It just doesn’t happen. They’re curious, they’re interested. They want to know what you do and where the aliens are buried and all of those questions that you get.
And to me, what that does for those young flight controllers is explain to them again, or emphasize to them again, why they came to work out here in the first place and recognize how cool really the job is that they have, that they get a push the envelope of the human presence in this solar system. That’s really what they do for a living. They might be a flight controller or an engineer or they might work for a program or they might design the flux capacitor or whatever it is that they’re working on. The job description really is if you work for NASA, that you are pushing the envelope of human presence in this solar system. That’s what you do, no matter what your job title is.
And if you lose that excitement for too long, you shouldn’t be working out here. You really shouldn’t. But if you start losing that excitement, go somewhere and let people recharge your batteries. But if you can walk into your office or, I walk the distance from my bedroom to my dining room these days with all this COVID stuff going on, but I’m still completely jazzed every day to sit down and talk to people about how we’re going to land human beings on the face of the Moon and return them back to Earth happy and work through all those problems and look at all those engineering design cases and talk about this control or that control or this aspect of that system or another. And that’s what I spend my day doing.
If I can’t get excited about doing that job, then I should quit. I should just hang up my spurs and go home because that’s the coolest job on Earth. There is no cooler job. You throw a job out there and I will challenge you that an ISS flight director whose real job description is I sit on console and operate a multibillion-dollar orbital spacecraft where we do scientific research with six human beings. That’s my job description. If I can’t get excited to do that, I should just be done.
Host: Links to topics discussed during our conversation are available on our website at APPEL.NASA.gov/podcast along with Royce’s bio and a show transcript.
For more interviews about the 20th anniversary of continuous human presence on the ISS, check out Houston, We Have a Podcast and other NASA podcasts at nasa.gov/podcasts.
If there’s a topic you’d like for us to feature in a future episode, please let us know on Twitter at NASA APPEL – that’s APP-el – and use the hashtag Small Steps, Giant Leaps.
As always, thanks for listening.