028 Stephen Johnson, Director, Space Nuclear Power and Isotope Technologies at INL

[00:00:00] Stephen Johnson: two weeks ago we hosted a American Nuclear Society topical meeting called Nuclear Emerging Technologies for Space Applications.

Typically that conference, which is held every year, is around oh 200, maybe 225 people. We had it here in Idaho Falls a couple weeks ago. It brought in 400 people. And we had people here from a total of nine different countries three different continents.

You’ve got everybody from like Dubai, launching a mission to Mars. You’ve got people, from India launching things to go to Mars. Russia you know, it’s just exciting. It’s a good time to be in the field of power systems for NASA applications.

[00:00:48] Intro: Just because the facts are A, if the narrative is B and everyone believes the narrative, then B is what matters. But it’s our job in our industry to speak up proudly, soberly. And to engage people that are in energy poverty, they need us. America cannot meet this threat alone. If there is a single country.

Of course the world cannot meet it without America. That is willing to. We’re gonna need you. The next generation to finish the need scientists to design new fuels. And focus on net public benefit. We need engineers to invent new technologies. Over absurd levels of radiation. Entrepreneurs to sell those technologies.

And we will march towards this. We need workers to operate a. Assembly lines that hum with high tech, zero carbon components. We have unlimited prosperity for all of you. We need diplomats, businessmen and women, and Peace Corps volunteers to help developing nations skip past the dirty phase of development and transition to sustainable sources of energy.

In other words, we need you.

[00:01:52] Mark Hinaman: Okay. Welcome to another episode of the Fire de Fission podcast, where we talk about energy dense fuels and how they can better human lives. We’re joined today by Steven Johnson, the Director of Space Nuclear Power and Isotope Technologies division at National or at the space, nuclear Power National Tech.

Technical director. No, I think I messed that up. It is kind of a long title, but at IDO National Labs. So Steven, how you doing today?

[00:02:18] Stephen Johnson: I’m fantastic. Yourself?

[00:02:21] Mark Hinaman: Excellent. Super excited to dive into this conversation, and hear about what you guys are doing with space and nuclear and space. But before we get to that, let’s hear a little bit about you.

Why don’t you give us kind of a brief introduction about yourself and let’s dive into some of your background.

[00:02:37] Stephen Johnson: Yes. I’ve been at the lab here, a little bit over 31 years. I have a PhD in chemistry from Iowa State names Iowa. Did a year or so at Los Almos National Laboratory and joined the staff here at Argonne National Laboratory West, which was then turned into the Idaho National Laboratory.

I’ve been doing things in space, nuclear power since 2002. Wow.

[00:03:03] Mark Hinaman: Have you seen a change a bunch since then?

[00:03:06] Stephen Johnson: Oh, I don’t know whether the change is external or internal. A little bit of both, I imagine. But it’s been an exciting last 20 years. There seems to be a fair number of missions on the NASA side that want and need to be enabled by nuclear power.

And things were much more exciting early on where we had to move a program from the Midwest to out west and do it in very, very short time. Build a building, hire 70 people and get a product down to Kennedy Space Center for a launch. Those were. Very exciting times. I’m kind of glad that kind of excitement and schedule pressure’s a little bit behind us now and things are much more regular, but still interesting.

Our last launch was the 2020, perseverance Rover. I don’t know if you’ve ever been down to Cocoa Beach, but when you get down there in early April of 2020, After the governor DeSantis had shut down Florida, and there’s nobody on the highway, nobody in Cocoa Beach. There’s a, guy with a clicker to get into, be one of the 200 people going into the Walmart store with everyone wearing masks and little arrows on the, aisleway saying, go this way or go that way, but, you know, don’t go against the street.

So that, that was a unique experience. I hope is never repeated.

[00:04:31] Mark Hinaman: Absolutely. Me too. Be before you got into space or at i n l? What were you doing? How’d you come upon it?

[00:04:40] Stephen Johnson: Yeah, so I was running the electron microscopy lab here and I had a high level waste form characterization group. We did some testing with waste forms using plutonium 2 38. As a doint and that was the heat source material that’s used with the radioactive thermal electric generators for nasa.

So when D u E came calling I was picked as the person to write the proposal, which was way outside my field really. But, I’m a trooper, so I. Put stuff together. Had, a really good engineering partner and managed to write a proposal for $15 million in about two weeks. And got the project moving in here.

And then I had a, time of to learn about nine months of interstate trucking to 28 tractor trailer loads of equipment from Ohio to here. Design a building. And then in the subsequent six to nine months after designing it, getting it built, there’s nothing like boring concrete the end of January in Idaho, when it’s six degrees outside.

It just makes you feel good.

[00:05:50] Mark Hinaman: Gotcha. Okay. And this division is in Idaho, obviously,

[00:05:54] Stephen Johnson: you just said that. Yeah. The Idaho National Lab right now is about 5,700 people. We have several campuses Kind of stretched out over 890 square miles in the eastern Idaho desert. And we employ, oh, 50 to 70 people bring in anywhere from 20 to $50 million a year business volume.

[00:06:17] Mark Hinaman: Who’s paying that or, what kind of business or revenue

[00:06:20] Stephen Johnson: are you guys bringing in? Yeah. So, right now NASA picks up the full bill. So, this yeah, so, they’re paying everything and, um, it’s you know, it’s an interesting way to go. And we are one of three laboratories on the D u E side that support this program.

Oak Ridge National Laboratory supports it, and Los Alamos National Laboratory and New Mexico supports it.

[00:06:46] Mark Hinaman: Got it. Okay. So tell us a little bit about the program. Why nuclear in space?

[00:06:52] Stephen Johnson: Okay, so nuclear is used as a, can’t do it any other way or something where it enhances the mission a great deal.

For example, if you’re going to the dark side of the moon solar power and batteries probably aren’t going to do it for you. If you wanna go the far reaches of space where solar panels. Our would have to be so large that you couldn’t envision in deploying them. For example, 1977, August and September, Voyager two and Voyager one were launched.

They were to go through and tour our solar system. All the planets send back images. They needed a power system that would work when they were very far from the Sun Radio, ice tilt power systems, where they were powered with something that had a half life. Radio ISO about 88 years. So, those probes were launched.

Not quite 50 years ago, but more than 45 years ago, they’re still working. They in 2013 and 15, they passed that little spot on the edge of our solar system, which said, you know, last stop for food and drinks, next solar system, X flight years away. And so they are now out in interstellar space.

They’re still, the power systems are still functioning. That’s the thing that’s really kind of neat. Those two probes are out there, pioneer 10 and 11 are out there. And the New Horizons, Pluto, we did the power system for the New Horizons Pluto, and that was launched in 2006. Those are the type of missions where you can’t pull ’em off any other way, or, you want something to operate on Mars and operate all the time.

Radio life still power, nuclear energy powered is the way to go. You get a good return on your investment and it keeps going for a long time.

[00:08:43] Mark Hinaman: Do you know the expected lifespan of the Voyager systems?

[00:08:49] Stephen Johnson: Here, this’ll probably make you laugh. They were launched in 77 and the answer was five years.

[00:08:56] Mark Hinaman: So they were under promise, over deliver, right?

[00:09:00] Stephen Johnson: Yeah. Either we’re really bad at counting or, yeah. We under promise and over deliver. That’s been, the hallmark for the radio ISO power systems. Currently, we shoot for about. A 17 year, certified lifetime, three years of storage in a 14 year mission. And so Voyager is always our poster child.

The Cassini probe that was launched in 77 and it orbited Saturn the planet Saturn. That was finally, it had done everything it intended to do by 2017. So they then diverted it into, the planet and it burned up on the way down. But I mean those nice. With Mars, we’ve got two current rovers up there working.

One was launched in November of 2011. That was curiosity. Another one was launched July of 2020. That was perseverance. That’s the one with the helicopter. That ingenuity that people get to see. They’re both working. So the power system for curiosity was actually fueled in 2008. So, it’s approaching that magic 17 year certified lifetime, but it’s still getting data.

And so that’s the exciting thing you get. A good long payoff for your investment.

[00:10:21] Mark Hinaman: Got it. Yeah. I mean, the solar fluxx just from, as you move away from the sphere, from the point solar source you know, it’s a cubic function for how fast your power drops off. Right. So, like, because Mars is further away. I think I read recently, solar reduction or the solar fluxx is reduced by like 50, 60%.

Um, and so the size of the solar panels you’d have to have just would be enormous. Exactly. Okay, so you guys are focused on the power systems for these, satellites, these exploration rovers. Is there any, well, lemme ask, what is the power system that’s typically used? Is it like a Starling engine or, um, you just got a little micro nuclear reactor on board.

[00:11:07] Stephen Johnson: It’s a heat source made out of plutonium 2 38, so about an 88 year half-life. That puts off a fair bit of heat. It sets kind of the inner core of the radioactive, so thermal electric generator. And you surround that with thermal electrics that are electrically connected. So you make a hot side and a cold side, and you set up, a kind of a small electron pump.

Based on your delta T between inside and outside. And you hook all that stuff together and you end up having a passive no moving part, thermal electric generator. Now your conversion efficiency is five to 7%, not the highest, but there’s no moving parts. There’s nothing to break. There are different power systems, different converter systems that are under development.

You mentioned one, a sterling engine where you have a movable piston and you’re working on a working fluid, of gas, of some sort. And the advantage of that is you can get 20, 25% conversion efficiency much better than five to seven. The downside is you’ve got moving parts. So if something goes wrong, once, it’s up there, it’s up there, there’s no uh, no repair man.

That’s gonna make a yeah. Road trip there.

[00:12:27] Mark Hinaman: Moving parts leads to failure much faster. It can. Thermal electric generator. I mean, there’s not like a battery pack on board that, this is charging or

[00:12:35] Stephen Johnson: There are, on several of them. You’re absolutely right. On perseverance and on curiosity, there are battery packs.

And, the radio ice to power system is essentially a battery charger now on the unit that’s intended to go to Titan, which is a moon of

Neptune, actually of Saturn, sorry. There they are going to use the power system directly. And that’s kind of an interesting thing. It’s actually going to be something, you know, closer in size to a small car and it’ll be a quad copter. And speaking to the principal investigator one point Dr.

Zepi Turtle from the applied Physics lab, Johns Hopkins, Columbia, Maryland. The gravity on, Titan is very low, and the density, the atmosphere is very high. So to put it in layman’s terms, if you could have a human being there, survive the cold and flap your arms, you could fly.

That’ll be more of a direct use of the heat and the electrical power from the R t G. We’re actually working on, a slightly customized R t G right now for that mission. And latest launch date that I have from them is a 2027 launch date.

[00:14:00] Mark Hinaman: Okay. Fascinating. I mean, there’s so many different types of systems that are advanced and, they’re not typically used on Earth.

Well, that’s a great question. Why don’t we typically use these systems terrestrial?

[00:14:15] Stephen Johnson: Yeah. So, there are some that are used terrestrial. Usually they’re powered by, um, By Strontium 90, which is ope, with about a 29 year half-life. We’ve had several of those. They’re used for things like let’s say weather buoys, maybe things that you wanna put somewhere.

Only make one trip there like Antarctica would be a possibility. Another country in the world that had several of those was Russia. They put over a thousand on their northern shoreline. As surveillance systems, then they kind of forgot about ’em, which is the downside. But they had over a thousand of those deployed along the northern coast of Russia and, I believe they’ve collected most of those ’cause people thought they were really neat if they ran across ’em because, you know, they’re warm and it’s great.

The bad part is when you get radiation poisoning not so good. But, um Use ’em as in-home heaters. Yeah, so typically Straussian 90. The reason for that is it does give off a good amount of heat. It also gives off some radiation that takes lead shielding to make ’em safe to be around and weight costs a great deal to get up in the space.

So you want something that’s as light as possible for space use. Hence plutonium 2 38 for that.

[00:15:37] Mark Hinaman: Got it. But you don’t necessarily have to use uranium or fission, fission atoms or heavy elements to create the heat. Right? I mean, on these thermal electric generators, I just looked up a picture of one.

It’s essentially just a solid state metallic block that gets hot on one side and is cooler on the other side, and then when the heat fluxes, it generates the current. Am I thinking about that correctly, or is it.

[00:15:59] Stephen Johnson: Yeah, that’s you’ve got the right model there. As far as the uranium the US has flown one space reactor back in, in the mid sixties.

The Snap 10 A the Soviet Union at the time flew, oh, I’m gonna say somewhere in the 30, 35 different. Satellites that had small space reactors on them. And that’s where you are doing a fission reaction that is producing energy, producing heat, and then you use a similar type of, converter to take that heat and turn it into usable electrical power.

Um, the US is working on a couple different reactor technologies. One would be for, say, a base on the moon or Mars, where it would concentrate on taking that thermal energy that’s created by the Visioning Act and turning it into electrical power, where you need, say, tens of kilowatts of electrical power.

Another one would be nuclear thermal propulsion, where you’re using the reactor essentially to provide you with a stream of hot hydrogen. Hydrogen’s ejected one way, your rocket ship goes in the other way. That would be a way that we could get say, human beings to Mars and back in a reasonable amount of time.

We can get things there now using chemical rockets. We just can’t get them back.

[00:17:26] Mark Hinaman: Yeah. It’s a one way ticket. Yep. Okay. I mean, we’ve kind of bounced around a little bit from our prescripted list of questions, so, I’m fascinated by the topic. But you covered it a little bit with some of the advances that have, I guess we’ve progressed from kind of the voyager to the spacecraft that’s going to Titan.

Um, but let’s just dive in a little bit more. I mean, you know, In my mind, I see Sterling engines in it for like commercial energy reactors. We see them hooked up to a power system, like a turbine or reciprocating engines all the time, but we don’t necessarily use those systems for space.

[00:18:08] Stephen Johnson: Yeah, I think Sterling’s, if it’s for shorter length of time, then say, the 17 years I mentioned earlier, and if they’re were, they can be serviced.

Excellent choice. But if it’s where they can’t be serviced, and let’s say if you’re going to Titan and you take four to six years to get to Titan before you even start doing the fun stuff, all of a sudden reliability is your number one thing that you’re concerned about. Yeah,

[00:18:38] Mark Hinaman: that makes sense. Um, do we have a lot of satellites and other space objects that are nuclear powered?

The US has launched I forget whether the number is 27 or 28 over the years. But it’s in that ballpark and some of ’em had more than one power system on there. So it’s 27, 28 missions and probably approaching a little bit shy of 50 power systems up there. Okay. Cool.

[00:19:06] Stephen Johnson: I mean, you mentioned that, you know, we use plutonium as one of the fuel sources and people are paranoid about plutonium and proliferation concerns.

Um, are there any safety or security concerns? I mean, one of the disposal or one waste Handling methods that has been proposed is well, if we can’t put it anywhere, let’s just launch it into the sun. People then get freaked out about, well, what if it blows up when it launches? Um, is that still a concern with these size systems or is the source just so much smaller that it’s,

Less of an issue?

We do an extensive launch safety package for every mission that goes up. We look at it several different ways. We do public outreach in that regard. I won’t say the probability is zero, the probability is very low, and we try to engineer in to the heat source a good probability that even if you had an accident, you’re not gonna be spreading material around.

It’s very robust. It is extensively tested at. Typical what I call a skydiver velocities, which is how it, the speed that it would come back into the earth about 120 miles an hour or something in that range. And so it’s something that we plan for. It’s something that we model. It’s something that we test to, so we can say, Hey, you know, this is a safe system.

And so that’s how we address that.

[00:20:32] Mark Hinaman: Got it. I mean, in my mind there’s just so little fuel, and maybe I’m conceptualizing it wrong. How much of the payload is actually the fuel for most of these

[00:20:41] Stephen Johnson: systems? In terms of the plutonium fuel or in terms of the chemical rocket fuel,

[00:20:48] Mark Hinaman: The nuclear fuel.

I mean, the chemical rocket fuel I get then. Yeah,

[00:20:51] Stephen Johnson: yeah, yeah. No, the, I mean, The current power system, which is a multi-mission radioactive thermal electric generator, M M R T G for short has approximately 10 pounds of plutonium oxide on. Okay. And so, that is a very, very small percentage of the total cargo, much under, I would say, much under 1% for the most part.

[00:21:18] Mark Hinaman: Versus if we had to use the same amount of hydrogen, it would be thousands of times more

[00:21:24] Stephen Johnson: feasible. It’s little apples and oranges there. But, um, yeah, no plutonium is a good concentrated heat source. And again, the scientists and engineers are very clever in terms of exactly how little electrical power they need because they’ve got a.

I’ve gotta manage all that on a daily basis. Right, right.

[00:21:50] Mark Hinaman: Okay. So you mentioned Mars once, but can we chat a little bit about NASA’s Mars Scientific

[00:21:56] Stephen Johnson: Laboratory Mission? Certainly M S L took off let’s see. It was launched the Saturday after Thanksgiving in 2011. And, arrived at at Mars approximately, let’s see, seven, eight months later.

’cause it came in hard time zone. It was about 11 o’clock on August 5th of 2012th. And it was yeah, it was exciting. They had two satellites on Mars that they could. Time meant so that when it was coming down in and screaming down at supersonic speeds and deploying a parachute and finally a sky crane to lower it down the last bit, they had two satellites that were observing it, which was a pretty, pretty cool actually.

And, for my team here, we were all back here in Idaho Falls. So we actually rented out a establishment at one of the hotels and. Took over the live screen and had the NASA channel on, and, it was exciting. And then the next day was Monday and I was at the front gate along with others handing out about 800 Mars candy bars.

So, I mean, when you only have a party every few years, you try to do the best you can. Hey,

[00:23:14] Mark Hinaman: so that’s super cool. And your guys’ power system is on that spacecraft, right?

[00:23:19] Stephen Johnson: Yeah. Yeah. So, we also, you know, you can work your entire life on certain neat projects, but you never get an opportunity like to have a Hot Wheels car.

This is a Mars Rover, or I. Or a Lego set.

[00:23:36] Mark Hinaman: So yeah, they made replicas, for folks that are just listening, Steven just held up a Hot Wheels toy car and then an actual Lego set of Yeah, the systems that it’s

[00:23:46] Stephen Johnson: built, right? Yeah. The Lego set, I should have bought a lot of, they were going for 50 bucks, and if you have an unopened one like I do, they’re now four to $700.

So. Like I said, you can work your entire life and never have, a project with toys, you know, so, hey, you gotta be excited.

[00:24:04] Mark Hinaman: Yeah. That’s awesome. Would you say interest in nuclear technologies for space applications is increasing

[00:24:10] Stephen Johnson: now? I think so. Just

two weeks ago we hosted a American Nuclear Society topical meeting called Nuclear Emerging Technologies for Space Applications.

Typically that conference, which is held every year, is around oh 200, maybe 225 people.

Last year in Cleveland it was 379 people, all time attendance.

We had it here in Idaho Falls a couple weeks ago. It brought in 400 people. And we had people here from a total of nine different countries three different continents.

You’ve got everybody from like Dubai, launching a mission to Mars. You’ve got people, from India launching things to go to Mars. Russia you know, it’s just exciting. It’s a good time to be in the field of power systems for NASA applications.

[00:25:05] Mark Hinaman: Absolutely. Is there more interest from the

[00:25:08] Stephen Johnson: private sector right now? There’s a great deal of interest from the private sector. Everybody’s interested in going to the moon. They’re interested in commercial Flights going to the moon, which would be under the administration of the f a a in the United States.

And they’re interested in power systems. So, they’re looking at lots of different radioisotopes, lots of different power systems. And as well as the US Space Force is interested in that as well for small satellites. So all these things are going on, everybody’s scrambling through new technologies.

Whether it’s a reactor or a radio ISO power system, it’s an exciting time to be in the business. Absolutely.

[00:25:53] Mark Hinaman: We chatted with Ottum of Space a couple weeks ago and hope to have ’em on the podcast too, and they’re doing some pretty cool stuff with space vehicles or a tow vehicles and radioisotope propulsion.

So, we’ve seen a little bit of it. Um, so what other uses of nuclear technology do you See in promoting space exploration, I

[00:26:14] Stephen Johnson: mean, we covered a lot of them, but I think we covered most of the ones that I see. There’s always small amounts of other radioisotopes alt 60 or various neutron emitters that are used as a portion of an analytical instrument in order to get additional analysis capability.

Those are long, even on solar emissions. But big ones radioactive to power, and nuclear reactor fission power are the large ones that really make a huge difference in the success of emission. And once you get up there, how much data you can get and how fast. Got it.

[00:26:59] Mark Hinaman: We talk a lot about propulsion systems and accelerating and, you know, how can you travel or have interstellar travel. But not a lot of people talk about decelerating or slowing down. Um, I mean, some of, the systems that got to Mars, we haven’t used any for strict propulsion purposes, have

[00:27:18] Stephen Johnson: we?

No. Not at this time. Yeah. Is there any plan or roadmap for that? There’s certainly a plan. I think nuclear thermal propulsion, which uses the stream of hot hydrogen is something that is in the works for maybe about 25 or no I’m sorry, 15 to 20 years from now. With fission surface power, that’s something they would like to send to the moon for a demo you know, by the, the end of this decade.

There’s a military, D O D funded effort under darpa, and they’re hoping to get something that’s in a earth orbit as soon as 2027 demonstrated there. It wouldn’t be capable of going to Mars, but it would be a demonstration of a reactor in a earth orbit situation, and they’re looking, that’s only four years away, so.

Cool.

[00:28:17] Mark Hinaman: That’s awesome. What are some of the biggest challenges that you see with nuclear and space in the future?

[00:28:25] Stephen Johnson: It’s always challenging getting enough people in the door here in the states to staff things. It is challenging depending on what isotope you’re using to obtain that isotope.

It was much easier. When we were involved in the Cold War because that people were out there making lots of different isotopes for military purposes, and so NASA could kind of piggyback on that effort. Now it’s more of a standalone type effort and you can make some of those things with the current research reactors in the us but those are kind of few and far between, so it.

The technology’s not unknown. We know how to do things. We know how to separate things from a chemistry point of view, it’s just finding enough time in reactors to make the isotopes that you want, that can be a challenge. Interesting.

[00:29:19] Mark Hinaman: Yeah. I mean, if we’re creating, literally performing alchemy and creating elements from radioactive K, then yeah, you gotta have a system that does that, right?

And yes those systems aren’t infinite. Um, so, do you guys engage with the

[00:29:36] Stephen Johnson: N R C at all? No. D u E is its own regulatory capability. And so we’re, on that side, with the most current setup that was developed over the last four years. You basically have three authorities. N R C is pretty, pretty much strictly commercial nuclear plants.

D u e is on the d u e side. And the f a a was set up to do commercial type things that fly, that. Those are the three agencies that are involved in the us.

[00:30:08] Mark Hinaman: Cool. Okay. Um, well, Steven, this has been great. Just a couple more questions for you. So, how can people help if they wanna get involved or if they, wanna be part of it or if there’s anything that they can do to just be cheerleaders for you guys?

How can people

[00:30:25] Stephen Johnson: support you? We’re always looking for people to help do outreach as something that a lot of my staff does, whether it’s, at the school level, elementary school. We do anything from there to rotary clubs. Any type of club that people are interested in. I don’t think we’ve ever turned down a request.

Well, I’ve had some odd ones where you go out to the school and they didn’t really tell you, what age group, at the school, and you get there. It’s a consolidated school district, so you have first graders through 12th. You know, I mean, what do you. But I remember somebody repeatedly asking me, well, hey, yeah, so where do the astronauts go?

And I kept on saying, it’s an unmanned mission. And, and they kept on coming back. There’s no people. They were like, yeah. And finally I was like, Hey, I said, you know, they just missed the launch. They were late. We had to leave ’em behind. And So, that’s good. And if they’re interested in really being involved, I mean, take the STEM courses, take the science of technology, engineering, math.

I have all sorts of people, engineers, technicians, quality assurance people that are, part of it. And, um, there’s no perfect background to be it, but, um, There’s plenty of opportunities out there, both, at the Idaho National Lab, other national labs, nasa, places like the Jet Propulsion Lab.

And you know, there’s a lot of times when things are fairly ordinary in between missions, but then you get a mission and it’s the greatest group dynamic. You ever see, you get down there and you’re one of like 12 groups. There may be a thousand people focusing on the, mundane question of making the pointy end go up.

I mean, and, that’s what it comes down to. And so, it’s always exciting at that part. And usually when we’re down in Florida, which we are for four to six months, you get to see lots of Falcon nines go up or other missions, and that’s exciting too. So, yeah.

[00:32:27] Mark Hinaman: That’s awesome. Okay, Steven, this has been great.

Why don’t you leave us with kinda your most positive vision of the future. What’s the world gonna be like in 10, 20 years and how how is nuclear and space gonna be involved in that?

[00:32:39] Stephen Johnson: Well, let’s say if you go out 20 years, I hope that we’re going to be talking about man missions to Mars. And perhaps a colony on Mars.

I think that would be way cool. And, a halfway colony, or less than halfway a sustainable city on the moon, I think would be a, good thing to be going on in 20 years time. Hopefully I’ll live that long. We’ll see. I bet you will.

[00:33:05] Mark Hinaman: So that’s great. All right, Steven. Thanks so much. Appreciate

[00:33:08] Stephen Johnson: it. Thanks.

You have a good day.

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