Planetary Radio: Space Exploration, Astronomy and Science - Space Policy Edition: Mars via the Nuclear Option

Episode Date: August 6, 2021

Can nuclear propulsion fundamentally transform our ability to send humans to Mars? Bhavya Lal, a policy and nuclear engineering expert now working at NASA, helped write a new report on the topic for the National Academies of Sciences. She joins the show to talk about the advantages of various types of nuclear propulsion, the engineering and policy challenges that face them, and the role of government versus the private sector in developing and deploying transformational technologies. Discover more here: https://www.planetary.org/planetary-radio/0804-2021-spe-bhavya-lal-nuclear-propulsionSee omnystudio.com/listener for privacy information.

Welcome back, everybody, to the Space Policy Edition at Planetary Radio, joined as always for this monthly installment of SPE by the Senior Space Policy Advisor for the Planetary Society. He is also our chief advocate. Welcome, Casey Dreyer. Hey, Matt. Glad to be back. Good to have you. And we have a number of things to get to before we get to a terrific, a second appearance by the great Bhavya Lal on the Space Policy Edition. You're going to talk with her today, just a tease here about nuclear propulsion or other forms of nuclear energy and how handy those would be out there beyond Earth. The nuclear option at Mars, just not the one that's been, not at the polls, but to get there faster and more efficiently.

Really interesting discussion. Really interesting stuff happening behind the scenes for a lot of us. Something that the Planetary Society is getting very interested in. And how that could be used, not just for, frankly, getting humans to Mars, but where else in the solar system can we benefit from that type of power and propulsion? So really fascinating stuff happening and very exciting potential future related to that. So we will go into the details with that with Bhavya. Atoms for peace, this time for real. I couldn't resist. I used to watch those old videos they showed us in elementary school about too cheap to meter. We do have some other things to talk about. And Casey, something that we have not regularly talked about, we both have newsletters. Yours is out. And so it's appropriate to mention that during the Space Policy Edition. How do people's a monthly newsletter where I write a little bit about what's going on.

I highlight some important pieces of space policy or politics. And it's got a great readership already. I'd love for people to sign up. And it kind of comes paired with this podcast. It comes about the second week of every month. And that's at planetary.org slash space dash policy. There's a link there to sign up, or we will put a link in the show notes of this very podcast. So I hope you sign up. It's free. So it's a fun

newsletter to do, and it's always great interacting. One of my favorite parts is when people write back and interact with me on the topic of the time. That's always great to be pushed and challenged and really explore some of these issues. So if you can't get enough space policy, have it show up in your email inbox. And I can tell you, it's terrific. I'll save talking about my newsletter, which is also monthly, usually comes out a week after Casey's. We'll tell you how to subscribe to that as well. How about hopping over to planetary.org slash join as well and consider becoming a member of the Planetary Society to enable newsletters and radio shows and social media. Oh, my. All of the great stuff that the society is up to, including the terrific policy work that Casey and Brendan, our man in Washington, do.

It all happens because of our members. Now, yeah, we do have some other sources of funding, but just like they say on public radio stations, it really comes down to our members. We could not exist. We could not do what we do without those tens of thousands of members. And just think how much more we'll be able to do

if you and other policy geeks like you join up as well at planetary.org slash join. Think of it as Patreon, but direct to the Planetary Society. It really does enable us to do this. Speaking of bucks, the kind that they print out of the Department of the Treasury, I think, isn't it, Casey? There is more budget news for NASA out of the House. Yeah. So we got the first step from Congress this year for NASA's upcoming fiscal year 2022

budget. The president's budget request came out a few months ago. It had proposed a roughly seven or so percent increase for NASA. Overall, pretty solid budget. A few tweaks to be made, I think. The House of Representatives, one chamber of Congress, made its first appropriations legislation, released it, passed it through committee. It's awaiting a vote by the full House. It seems relatively uncontroversial on the NASA side. And we got to see what Congress is thinking, at least part of Congress. We saw an even bigger boost, a modest one, but about an extra quarter billion dollars on top of what the Biden administration requested. So it's about a $25 billion budget for NASA adjusted for inflation that puts that, you know, if that passed as is, it would put NASA

back at about mid 1990s levels in terms of buying power. So that's a it's a really nice step in the right direction, in line with what we've been recommending these slow and steady increases of budget every single year. And what they do with that extra money, they, you know, they move some things around. They put more money into the SLS program as usual. They restore funding for the Sophia Flying Observatory, which the administration had proposed to cancel. And they add some money for nuclear thermal propulsion, something that Bobby and I are about to talk about. That's an ongoing area of somewhat division between NASA and the Congress

right now about how to allocate some of those research funds. And otherwise, it's a pretty solid, but they even give a few extra tens of millions to Mars sample return, which would make a record level of funding for the Planetary Science Division. So again, overall, a very solid budget. I would like to see a few tweaks, you know, as I always do, maybe throwing some extra money towards actual, you know, fundamental scientific research in planetary science to enable more scientists to work and more students to work. Those are things we'll keep pushing on the Senate side, but very promising overall pathway to getting a budget this year for NASA. So I have updated all of these numbers. You can read all the gory details of this

on our fiscal year 2022 tracking page, including links to the original source documents. That's on planetary.org. We'll put a link to it in the show notes here, or you could just Google, you know, NASA FY 2022 Planetary Society, and it'll show up right there. That's nice to know. That's a big kudos to Google for putting you up near the top when people search for something like that. I have a message for you, Casey. Amy Meinzer says hello. We talked about NEO Surveyor and Planetary Defense.

We talked about NEO Surveyor and Planetary Defense. And your name came up because we were talking about how you have documented the very impressive and very welcome growth in funding of planetary defense activity within the NASA budget. And she, of course, is delighted to see all of that. Oh, I couldn't be more excited for her and for the team and for, frankly, all of humanity that we're starting to actually build this deep space telescope dedicated to looking for near earth objects. That's one of the key, really positive aspects of this Biden budget that came forward this year. We're really excited about that. We do have a petition online that you can help encourage Congress to fund it in the house.

They did very happy. They were seem to be happy to do so. So this is just a great step forward. And this is just such an important mission. Actually, I'll be having an op-ed publishing in Scientific American on the 25th, talking about this very important investment that we can make in light of what we have learned in our pandemic year coming out of COVID, right, another type of low probability, high impact natural disaster that is at some level preventable, or at least you can mitigate the consequences of it if you pay attention early, if you act early and you're ready, if you've put the proper investments in protecting humanity. And so I think there's quite a bit we can learn, good and bad, from our experience with COVID

into how we plan and prepare and invest in preventing near-Earth object collisions with the Earth. After all, we're just trying to save the world, right, as the boss says. Get us into this conversation with Bhavya. We've given people a little bit of a preview. Yeah. So the big motivation for this discussion with Bhavya, and Bhavya Lal, by the way, I should just introduce, she has held a number of hats over the last few years, but right now she's a senior advisor for budget and finance at NASA. Now she's briefly served as the interim chief of staff before Administrator Nelson came in. And prior to that, she was at Space Policy Institute, Science and Technology Policy

Institute, STPI, and had done a number of very interesting reports and analysis on various aspects of human spaceflight, scientific spaceflight, nuclear propulsion, and others. In April, there was a release of the National Academies of Sciences, Engineering, and Medicine focused on the role of using nuclear propulsion to enable human missions to Mars. And of course, that rings our, gets us excited at the Planetary Society, getting humans to Mars ultimately is one of our big goals. What is this kind of enabling technology used for? How close is it to being real? How important is it that we invest in that technology first before

going to Mars? Or is it something that can come after? And what else can it be used for? Can it be used for things at the moon? Can it be used for scientific missions? Can it be used to create power in addition to thrust? These are non-trivial questions. Space nuclear power has been investigated in the past. It was programmed at NASA in the 1960s, early 70s, before it was canceled. Russia has flown fission power systems in space a number of times in the 20th century. And it, on paper, solves a couple of problems. Theoretically, it could solve, it could get you to Mars really fast.

It can give you a ton of propulsion, a ton of thrust, I should say. It can also generate a lot of electricity. Electricity is one of those very limiting aspects of space hardware design that we have to grapple with. And if you have lots of electricity, you can do lots of stuff with it, including power electric propulsion engines,

like the ones we've seen on smaller scale ones we've seen on Deep Space One or Dawn. Medium scale ones we'll see on the Gateway. So that can be a very enabling and important stuff. So we talked through this report, which tried to analyze the differences of nuclear electric propulsion and nuclear thermal propulsion, why those are important, and then also really

try to address some of the fundamental engineering challenges. What are we actually asking for if we want to pursue a serious development effort for one of these? So it's one of those things. We're at this kind of, I think, key point in history. You already said this is a very interesting times we live in. How do we make sure that 10, 15 years from now, we're also living in interesting times? And that means that we have to be investing in fundamental technology now that pay off in a decade or two. And if we don't, you know,

we're faced with the same set of physical constraints that we face now that prevent us from doing certain types of missions that we might like to do. So this is, again, when and how do we make these decisions? This report's a big aspect of that. Bhavya is an expert. Her background is not just in policy, but in nuclear engineering, very helpful in this field. And we really get into the details of it.

I think it's a fascinating discussion we had. Well, let's listen to it now. It is the return of Bhavya Lal of NASA to the Space Policy Edition. Here is her recent conversation with Casey Dreyer. Bhavya, welcome back to the show. I am so excited to be here, Casey. I love your podcast. I eagerly await it every week.

So thank you for doing these. They are so wonderful for the community. Well, thank you. I appreciate that. And this is an area that you are, I'd say, relatively intimately familiar with. Your background is in nuclear engineering. Is that correct? That's right. My bachelor's and master's degrees are in nuclear engineering. However, having said that, space nuclear is a totally different kettle of fish. So there's a lot of learning that's happening on that front. Well, let's dive right into it then. So you were on the National Academies Committee that released in a report earlier this year called

Space Nuclear Propulsion for Human Mars Exploration. Nuclear propulsion is something that just organizationally here at the Planetary Society, we've been growing really interested in. I personally have been growing really curious and interested in it. But as you point out, nuclear engineering is not like an easy thing to wrap your head around. So I'm really excited just to ask you some, most of these questions just be honestly things I do not understand. I'm very curious to hear your input and perspective on. And so let's just kind of talk maybe big picture for a second to help define some of the terms of what we mean by nuclear propulsion and in space nuclear. In this report, you're talking about fission nuclear as opposed to the use of plutonium-238.

So what's the difference between what NASA has already been doing with nuclear power in space and what this report is talking about? Great question. For the last 60 years or so, NASA has been using what are called radioisotope thermoelectric generators or RTGs to produce power and heat, never any propulsion. So that's the first distinction. Both RTG and fission reactors use nuclear reactions to generate heat. However, the two reactions are very different. Nuclear reactors, such as the ones we would use for propulsion, or even power generation, involve what's called controlled nuclear fission. We use slow or fast moving neutrons to split a nucleus. And because this is done in an active, deliberate way,

the rate of the reaction can be controlled with neutron absorbing control rods, for example. So power can be varied and you can even shut it off. And RTG works entirely differently. Heat is produced through spontaneous radioactive decay. So plutonium-238 is artificially created, but it decays with a half-life of about 87 years and releases alpha particles. So the heat produced during this decay process can be converted

into electricity using a device called the thermocouple. And, you know, there are some other more advanced approaches as well. In an RTG, and that's a pretty key difference, heat generation cannot be varied with demand or shut off when not needed. It is not possible, for example, to save more energy for later by reducing the power consumption. It's like a hot rock. You got it hot and it's going to get cool at the rate it wants to be. So yeah, so we've been using this plutonium-238 fuel devices since the 60s. The first RTG was launched aboard a Navy satellite in 1961. And since then, we have had an RTG in almost every NASA mission, including several Apollo flights, the Viking 1 and 2, Mars landers,

the Voyager 1 and 2 probes that went to the outer planet of the solar system, the New Horizons mission to Pluto, and most recently, the Mars Perseverance rover. In fact, the upcoming Dragonfly mission to explore Titan will also include an RTG. Moving to use of nuclear reactors, the United States has only ever launched one nuclear reactor called the SNAP-10A in 1965. Russians have launched lots of fission power systems. To the best of my knowledge, we have never launched a propulsion system, though the SNAP-10A did include an experimental thruster that could be useful for a nuclear electric propulsion system.

Basically, what we're talking about here for nuclear fission, it's kind of like the same conceptually power generating source that's used in nuclear power plants. Is that correct? So for nuclear electric propulsion, that is correct. Okay. In an EP system, basically, yes, you produce heat in the reactor, which is converted into electricity, which then propels ions, electric thrusters that get shot out the back of the system. NTP, a nuclear thermal propulsion system, it's a different process. NTP is actually pretty similar to how chemical rockets work.

So for example, in a chemical rocket, a combustion chamber creates a hot gases that are then expanded in a nozzle to produce thrust that pushes a spacecraft forward. In an NTP system, the energy source is not that combustion, but rather the heat created when the atom fissions. So this heats a propellant, which is most often hydrogen, which then goes out the back as a traditional system. So very different

approaches to NTP and NEP. so we don't do this soup of acronyms for the rest of the discussion, for sending people to Mars. And that's kind of something I want to emphasize here, too, that this report that you worked on was tasked to evaluate a very specific set of requirements, specifically for sending people to Mars in a NASA type mission, right? And that really drove the requirements in terms of how you evaluated the nuclear thermal option, which was, again, let's just emphasize that kind of this classic rocket where you're using nuclear energy to heat up, basically, hydrogen to expel it out some nozzle propulsive pushing you forward versus nuclear electric, which is kind of an upscaled

version of what we've seen already on some small NASA missions that use otherwise solar power. So basically, you're using nuclear energy to create electricity that then expels ions out the back. And they're two very different types of propulsion, even though they both use nuclear fission at their core to create that energy. That is accurate. And in fact, one of the biggest challenges we had as part of our committee deliberations is to better understand the different challenges in both systems. Nuclear thermal systems, it's almost a single, single system. And it's a kind of system we have a lot of experience with since we know how to operate chemical rockets.

It's what I call complicated. You know, it's hard. You know, we have to heat a propellant to very high temperatures, 3,000 Kelvin, 2,700 Kelvin, for example. But it's doable. It's just a matter of investing in it. You know, we need to solve some materials challenges, but we can do that. NEP is actually a combination of a lot of subsystems. There's the generation subsystem and the conversion subsystem and the electric thruster subsystem. It's what I call a

more complex system. Complicated and complex is kind of the distinction I'm trying to make here. Complicated, it's hard, but we'm trying to make here. Complicated, it's hard, but we know how to do it. Complex, we don't even fully understand. So one of the findings of the Academy's report was that, and you know, our assignment was to kind of assess if we could get to Mars with one of these systems by 2039. And our assessment was that with nuclear thermal systems, there is, you know, with aggressive investment in R&D, and we don't have it right now, you can make it to Mars by 2039. However, the committee assessed that even with aggressive investment, 2039 is a, is what I would call a sporty date to Mars.

is what I would call a sporty date to Mars. Let's step back for just a second before we start really comparing nuclear, thermal, nuclear, electric, because I want to get to the core of why you were even asked to investigate this. Assuming either one, what fundamentally, what's the pitch for using nuclear propulsion and doing all this work to figure out

these complicated and complex systems to begin with? What advantage do they give over the technology we have now? Okay, so now you're testing my fundamentals, Casey, and I'm going to give it a shot. I'm going to already apologize to my mentor, Mark Lewis. He will say I'm oversimplifying things, but let's get to it. Let's start with the simple, yeah. Yes. So to answer the question, we actually first need to understand the concept of specific impulse. Speaking plainly, a specific impulse or ISP is a rough measure of efficiency, sort of like a car's gas mileage.

So a propulsion system with higher ISP produces more thrust for the same amount of propellant. Put another way, the higher the ISP of a system, the less propellant you will need for the same level of thrust. So you can see where I'm going with this. With nuclear propulsion systems, we get high ISP. Nuclear thermal systems have twice the ISP of chemical systems, and nuclear electric systems have five, ten times the ISP of chemical systems. Therefore, to get to Mars, you will need less propellant if you use nuclear systems. And since all the propellant we need today is launched from Earth,

this translates into less cost. So an SLS launch may be a billion dollars a launch, so if you're doing 20 launches versus 40 launches for chemical systems. So now you will ask me, why is the ISP high for a nuclear system? That's a harder question. So if you remember the rocket equation, and maybe you can put that on the episode webpage, you will see that the ISP is roughly proportional to the exhaust velocity in the rocket. In a thermal system, because the molecular weight of hydrogen, which is a propellant and the coolant for the reactor, because the molecular weight is lower than that of water vapor, which is essentially what comes out of the chemical rockets,

for a given temperature, the hydrogen is moving faster because of its low weight, and therefore giving a higher ISP. In a nuclear electric propulsion system, the charged particles can be sped up to even higher velocities. And so the ISP is even higher, five to 10 times higher than chemical systems. So basically, the problem nuclear is solving is that it reduces the amount of propellant needed for a distant journey. And because it uses propellant more efficiently, for the same amount, nuclear can provide much higher acceleration, which means we can reach the destination faster.

So now I'm coming to your core question. It's a really long way of saying that all else being equal, nuclear reduces the length of time it will take to make a round trip to Mars compared to chemical systems. And given how far away Mars is and how much, you know, galactic cosmic radiation astronauts might get exposed to, that's desirable. I think that really is what resonates with me is thinking about the time question. I've, you know, we've talked about this and many people have talked about this over time, but, you know, the difficulty in sending humans to Mars, when you just think about the requirements for perfect functionality of all of these thousands of systems for using chemical propulsion, talking about two to three years or so for a round trip.

And you look at something like the ISS, which constantly needs repairs, constantly needs to be resupplied, constantly things are breaking and is in constant communication with the ground. And to then say, we're going to go from that to basically an autonomous, human-capable, supporting-life spacecraft that will be on its own

with almost no supply improvements, like no ability to provide new materials for years at a time that starts becoming just very hard. So I bought, you know, if you think about can if you can reduce the length of time, things have to function perfectly by reducing your trip time, it could actually simplify to some degree a lot of different problems, right? Life support, psychological issues, health from radiation exposure, as you mentioned. And that seems to me to be this really compelling fundamental motivation for humans to Mars. And just to emphasize here, you know, I'll try restating something and you can tell me

if this is a correct way to think about it. Emphasize here, you know, I'll try restating something and you can tell me if this is a correct way to think about it. But nuclear, in a sense, offers this huge advantage in energy density that then you can use for propulsion, right? Because chemical rockets, you're kind of limited to how much energy can be stored per unit volume in hydrogen combustion at some level of combustion. combustion. Nuclear, by definition, you're very, very dense, huge amounts of energy in small spaces that allow you to use just way more energy in general than you could possibly bring with you in a chemical system. That's exactly right. You could get the same kind of performance with chemical, but you just need so much more chemical propellant. And you know, you need to set up, and again, I don't have the exact numbers with me and I don't think SpaceX has released them,

but you would need hundreds of launches of a starship to be able to do Mars with chemical systems. So yes, you can do it, but you are going to be taking so much more mass. And there are actually a lot of challenges with aggregating these tanks. And again, like you said, all of this may need to be

done autonomously. So you're arranging around a spacecraft, you know, these tens of tanks or hundreds of tanks, and then you're pre-positioning these propellant tanks throughout the way. So yes, so you cut a lot of risk by having nuclear. Having said that, Casey, I mean, there are other long poles in the tent as well, right? So we don't really understand the effect of galactic cosmic radiation, extended exposure, right? I mean, the Apollo trips were a few days max. The ISS is in low Earth orbit, and it is not the radiation environment of deep space. So we need to figure out what is the effect of being in deep space for long periods of time. And actually, that's one reason a moon is a good testing ground, right? Moon is in deep space. And there's other long poles. You

mentioned an environmental control and life support system, right? All the oxygen we need, all the water we need, all the food we need, everything we have to take. So it's sort of like, you know, if you have a car ride, you know, and it's a 30 year car ride, and you have to take everything, there's no gas stations, there's no convenience stores, grocery stores, everything you need in your 30 year journey. Well, I guess three years for two to three years from March, if you're coming back, you know, you have to take everything with you. And that's a whole lot of logistics we need to understand and worry about. Yeah, it seems like there'd be like a lot of predictive statistical analysis to say what things are most likely to be needed for

repairs, what are most likely to break and how you would have the this proper balance of mass to useful repairs, you know, prioritizing things that will keep you alive. I always think about Kelly's year long stay on the space station in the book he wrote about it. He kind of talks about half his time is spent fixing the CO2 scrubber, and how we'd get these terrible headaches and NASA would be walking him through on the ground, like these intricate repairs of these machines that keep them alive. And they, you know, they have to send new materials to repair these machines with. And how would you do something with your CO2, you know, scrubber or whatever machine broke on the way to Mars, you would hope you would have the right tools

to fix it. Otherwise, you're, you're done for, right. And I think that just emphasizes, again, the complexity. And also, again, this is where I come down to, like, if you can reduce that trip time, your requirements for assuring performance, I imagine scales at some nonlinear way, right? If you want to assure performance for three years, it seems like it would be much harder than assuring performance for a year and a half. That's intuitive, an engineer may correct me on that. But that seems to be the types of improvements you would get from reducing trip time. That's exactly right. So even though the trip time only goes down, let's say 40%, it is an extraordinary accomplishment to be able to do that. So every month we reduce is

that exponential effort. So actually nuclear offers a couple other reasons. So it's not just reduced trip time, but it also, we have a broader set of windows to launch. So we are not stuck with a particular timeframe and for which you might cut corners, for example. I mean, not that NASA would ever do that, but it allows, like we have just more windows to launch, which is important.

And also, and this leads up to the point you were making just right now a nuclear also gives us more abort capabilities than chemical with the chemical system once you're on your way you're going like there is no coming back there is no changing course uh with nuclear you can abort for at for for a little bit longer than than for chemicals and those are important points. And actually, I mean, across the board, Mars is really hard. So, you know, folks who say, you know, why aren't we, you know, why don't we just go to Mars? Obviously, we do. And it's a horizon goal. But there's so much that needs to be done and so much that can be done in the vicinity and on the surface of the moon. These sorts of things that you brought up, you know, what are those statistical, you know, what is the

data that would go into those statistical models to figure out how things break? I mean, we just need to be in deep space for us to be able to answer some of those questions. And again, I mean, NASA and folks outside NASA have been working on this for a while, right? Well, I understand Juan Brown wrote the first plans for Mars,

the day Apollo 11 landed back. So we've been thinking 60 years, more than 50 years for how to get to Mars. So there's a lot of information we have, a lot more we need, and we just need to get going. I want to just hit on one point that you made, which is it opens up more opportunities to launch to Mars if you have nuclear propulsion. Specifically for this report, you were actually tasked with looking at what was called opposition class launches. Do you want to just briefly mention what those are as compared to what we're usually used to in our 26-month cycle of conjunction class launches? Yes. Opposition class missions are missions which reduce the amount of

time we have to be in space. Conjunction class missions force us to stay on the surface of Mars for a year or longer, so we are back in a specific alignment between Earth and Mars. With opposition class missions, you're not forced. You can be on the surface of Mars for 30 to 50 days, for example. And again again there's advantages for especially for the first trip or the first few trips for us not to be uh be on the surface and and it's this is controversial there's you know folks like robert zubrin who say that when we go to mars we want to stay there's so much to do uh and and there's others who say well maybe the first trip can you know we can focus on the more of the the trip rather than the day, because in order for you to be

on the surface of Mars, you need to pre-position a lot of cargo power, for example. I mean, you absolutely need to have power on Mars before the first humans arrive, right? So yeah, so with opposition class missions, you can spend less time on Mars, especially for the first time, which is important. The trip time, like the amount of time you're in space is longer, especially for the return journey. Often you have to fly by Venus. But I guess those are things we just need to figure out better. The one downside of opposition class missions, and that's why actually nuclear really comes in handy, is that it has a very high delta V requirement. And you cannot get that as easily with with chemical or even NTP systems as as

easily but but it is it is feasible. And that's where the trades start to get very complicated. And delta V just to remind people is that the change of velocity required so and which takes more energy, which takes more propulsion, and depends on the type of system you're using. And again, just to really make sure I understand this, we talk about opposition and conjunction. Conjunction is basically when Mars is kind of close to Earth is when you launch. And that's what we do when we send spacecraft to Mars now for like perseverance. Mars was kind of coming close to Earth.

We launch and it hits Mars on the other side of the solar system. Opposition is when we launch, when Mars is kind of on the other side of the solar system and we catch up with it. And I love the idea of like, let's just do a swing by a Venus on the way and wave. I would love to do that mission from an experiential thing. You open up a lot of opportunities. And one question I actually didn't see mentioned in the report is, you know, these broader uses of in space nuclear, which would in addition to propulsion, these broader uses of in-space nuclear, which would, in addition to propulsion, would they be able to provide energy for the spacecraft as well? Power for the spacecraft is also such a precious utility and a limiting factor in so many ways.

Does this open up other options for that or kind of serve a dual purpose for getting to Mars? So I think the systems we are currently thinking about do not have the power attached to power piece attached to it. But there is this thing called bimodal operation for nuclear thermal reactors, where you can generate power. And obviously, for any P systems, you are generating power already. So yes, so that would be very helpful. In fact, we are talking about human missions to Mars, but let's say we talked about science missions. You know, science missions don't have as strong a need for high delta V or, you know, fast propulsion systems, right? We actually don't mind if it takes a few years to get to Jupiter, although it would be nice to get there faster. I don't know if you remember the Galileo mission, you know, it had to use multiple gravity assists

around Venus, around Earth, and even then it took 10 years. So with nuclear electric propulsion, you may not need as many or any gravity assists. And you have the power which science missions need for instrumentation, for communication and other things. And of course, the advantage that gives you is, you know, you can conduct extended investigations rather than brief flybys of bodies of interest. You can visit multiple bodies much more easily.

And actually, if you find something interesting, you can alter a spacecraft's trajectory in response to, you know, whatever particular thing you want to make a change about in a particular mission. So certainly, having both power and propulsion would be a good thing to have both for human missions, but especially for science missions. And that is something that, you know, folks like John Cassani and others have written about, you know, the value of NEP for science missions. Sani and others have written about, you know, the value of NEP for science missions. Yeah. Is that why? Because I was interested to say, why is nuclear thermal not generally associated with science? Is it merely because nuclear electric is theoretically better? Or

would science still not benefit from a nuclear thermal propulsion system? Or is there something fundamental? No, I don't think there's anything fundamental i think a nuclear thermal is just you know it's it's associated with high thrust emissions when you need to be when you have a need for speed with science missions that is not the most important criterion so and also science missions don't need um megawatts of power you know they would be perfectly right now an an rt that, for example, was on the Mars Perseverance rover is 110 watts. I think the New Horizons was, I think, 300-ish watts. Cassini was 500 watts. A kilowatt of power, for example, on a science mission is good enough. An NTP reactor tends to generate 500 megawatts of thermal power, not electric. I want

to make a distinction. And an NEP that we are thinking about for human missions, you know, we are looking at one to two megawatts. So the NEP system for science missions is a kind of a different, a smaller system generating, you know, a few kilowatts of power, which is a lot more doable than some of the bigger systems we need for Mars. Don't leave us. Casey and Bhavya Lal of NASA headquarters have a lot more to share about nuclear propulsion to get around quickly and efficiently in space. You're listening to the Space Policy Edition. There's so much going on in the world of space science and exploration, and we're here to share it with you. Hi, I'm Sarah, Digital Community Manager for the Planetary Society. Are you looking for a place to get more space? Catch the latest space exploration news, pretty planetary pictures, and Planetary

Society publications on our social media channels. You can find the Planetary Society on Instagram, Twitter, YouTube, and Facebook. Make sure you like and subscribe so you never miss the next exciting update from the world of planetary science. Let's dive in and talk about each of these systems a little more detail so we can emphasize the challenges, the technical challenges that would require to pursue them and just emphasize kind of their distinction a little more.

So let's start with nuclear thermal. And this is what you just said, that a nuclear thermal creates thermal energy. And this is what you just said that the nuclear thermal creates thermal energy. And I think that's really the key word here, right? That it's not generating electricity, it's just generating the heat that heats up, generally uses hydrogen feedstock to expel hydrogen atoms out of its propulsion system, and that creates the thrust. Nuclear thermal tends to be, he said, associated with high thrust. So I saw it in the report. This is generally more similar in concept to an existing

chemical rocket. Does this make it a more straightforward system overall or is there some inherent advantage of nuclear thermal and just how it works that it seems familiar? Yeah, there's nothing you said that I disagree with. I'll just reinforce. So conceptually, they're identical to chemical systems. However, they do have to operate at high operating temperatures. You know, the reactor system must heat the propellant to 2700 Kelvin. And we don't currently have materials that can handle that kind of temperature, especially the environment, the corrosive environment.

But there's other challenges as well. So we need a lot of, even though we need less propellant than chemical, we do need a lot of propellant and it needs to be stored in space. Hydrogen is notoriously difficult to store because it is such a small atom or such a small molecule that it just leaks through. A lot of R&D needs to be done to be able to store liquid hydrogen in space. Also, testing. In the 60s, when we tested nuclear thermal systems, and we have tried to develop them in the past, we didn't really worry so much about releasing radioactive gases. Remember, this gas is flowing over a reactor, right? So it is in some ways activated.

And there's some radioactive particles there. So we need better ground-based test facilities that currently don't exist. They may cost hundreds, if not billions of dollars to make. So there is a cost to that. But going back to your original question, yes, NTP is, and the report says so too, that by 2039 with aggressive R&D investment, we can have an operational NTP system. Obviously, we would want to test it by maybe using it for cargo for a while.

We don't want the very first system to have humans on it, but it's doable. On NEP, the challenges are quite different. The complexity of the interaction between the various subsystems, the parallel development of all of these different pieces, and then putting them together is something that we don't know how to do. And while NTP, nuclear thermal propulsion, we have data from the 60s, for example, or some experience,

I don't know how useful the data would be. But for an EP, we have not done anything. For nuclear thermal, let's just key on this for a little more, I want to follow up on a few of these challenges you mentioned. You said one of the first challenges for nuclear thermal is how do you deal with something that is heating up hydrogen to 2700 degrees Kelvin, which is something around, it's over 4000 degrees Fahrenheit, extremely hot, something that I was kind of noticing, and I don't know, perhaps I was reading between the lines too much on the report, which was that heat, that temperature is actually a byproduct of the requirement of what you went back to way at the beginning, this specific impulse, right? So if you want a specific impulse of about 900 seconds

or something, I think was the threshold, you do your calculations backwards. Okay, that means we need to heat up hydrogen to about 2700 degrees Kelvin. Is that locked in stone? Is that a fundamental problem that what drives that 900 second ISP requirement? And is there any way to get around that without having to develop completely new materials that will withstand this incredible amounts of heat? Yeah, so that's a really great question, Casey. For the Academy's report, this was a given to us. So these are very complicated trajectory calculations that folks with deep expertise, you know, they work kind of backwards from high level goals. And the

ones that we were talking about earlier, for example, how long are we willing to have astronauts be in deep space versus on the surface of a planet? How much mass do we want them to be carrying with them? How big the habitats, you know, basically, how can we adjust the mass that the system needs to carry. So they're kind of worked backwards from that. My understanding is that even switching to a conjunction class mission reduces the ISP to about 850 from 900. So it is not a huge reduction. And I guess as we start to do these developments, and if it looks like it is really not possible to get 2700 nozzle exit temperature, then yes, so there would be these trades that would continue to get made and maybe we would need to back away. But for the moment, just based on the models and other computations, 900 seconds is the ISP that is kind of our target.

Okay, so basically, if you want to have this range of options, opposition and conjunction classes, you need to have performance that then requires this exit temperature, this extremely high exit temperature. We're talking about materials science here, materials engineering, just the really extreme environment, right? Like that we shouldn't diminish that was actually called out by the report as one of the fundamental technology challenges is like, how do you build something to withstand temperatures to this degree? Something that fascinates me about this type of discussion now is how our desires translate into the fundamental challenges that we face when engineering these types of things. I just find it fascinating. Okay, because we want to launch

an opposition, because we want to have these set of options, because these are basic physics, therefore, it would be in NASA's best interest to figure out how to develop materials that can withstand beyond hellish levels of temperature. That seems like a fundamentally just a useful thing for a variety of broader applications, but it's driving it all because we want to send humans to Mars within these certain constraints. And I just find that very interesting conceptually, that that's how we end up with these specific engineering challenges to decide whether to tackle or not. That's a great point. And actually, that also kind of shows, you know, one of the differences between, you know, how governments think and how, you know, commercial entities think, you know, the government start with the requirements.

And if the requirements push the technology to its absolute frontier, then that's what we do, right. And in this particular case, and the Department of Energy has a lot of, you know, they're really, you know, longstanding world-class labs that do materials research, not just for nuclear, but other reasons as well. In principle, between industry and these DOE labs and academia, some of these challenges will get addressed. And then maybe you dial down requirements. I mean, I think commercial folks kind of think about it differently. They think about, you know, what can we do? And then go from there to developing systems.

So it's just a different approach. And I just think we need to actually take the time and start to think through these things. I don't think that as much of it has been done as I would like to see. Unfortunately, as you know, well, NASA has a 10 pound mission in a five pound bag, there's a ton of stuff we are trying to do. And this is just one more thing we need to kind of get just make those trade offs differently. That's such a good point. And I think really important for anyone listening to remember, yeah, that fundamental philosophical difference of approach between a commercial or private sector and the public

sector. I mean, and this is kind of why we have both in the ideal case that they're complementary. But the public sector is saying, okay, this is what we want to do. Therefore, this drives all of our investments. It's such an interesting shift when you flip it the other way and say, what can we do that becomes useful to some degree that then we can maybe build on, which is kind of, you said, the more commercial private approach to it. So, Bobby, I just want to touch on two more challenges you mentioned offhand that just to emphasize, again, on nuclear thermal, and then we'll move a little bit more to nuclear electric. The amount of liquid hydrogen is not a small problem. amount of liquid hydrogen is not a small problem. I think if I remember from the report, you're talking something around 20 megatons of liquid hydrogen propellant. That sounds about right. Yes. And that's a lot of launches. Yeah. I mean, I think there was a plot. I think it was in the

report. I've been reading a lot of these lately. The International Space Station is around 400 megatons. Yeah. 400 metric tons. That is correct. Metric tons Station is around 400 megatons. Yeah, 400 metric tons, that is correct. Metric tons, sorry, not megatons, metric tons. And so we're talking about a similar, like half of that being in propellant. This is the efficient, this is nuclear thermal, this is the straightforward. So we're talking about launching huge amounts of liquid hydrogen that then have to be encapsulated in this hyper efficient manner in these giant amounts to last years, right? Because it's again, if this boils off, you don't have a ride home from Mars.

And so that again, this is like, how do we make really efficient, reliable storage for this volatile material? Again, I found that as one of these fascinating challenges. And there's one more aspect you said, which is ground testing. I'll rephrase it back to you can tell if I understand this correctly, because you're effectively running through hydrogen, basically right through the core of a nuclear reactor that uses uranium, you can get some nuclear material coming or radioactive material coming out with the hydrogen on the other side. To test it on the ground, you don't want to spew all that stuff into the air.

You need to capture it and control it. And that's where these facilities just do not exist anywhere on Earth. That's correct. And as I said, in the 60s, we didn't mind as much. It was a different environment. Literally, yeah. the 60s, we didn't mind as much. It was a different environment. Literally, yeah. Now, we absolutely do not want to be having any radioactive material, you know, beyond,

obviously, you know, there's safety limits going into our biosphere. And yeah, these facilities would be very expensive to construct. You know, there are some proposals I have read, which are really interesting, that instead of testing on the ground, why don't we test in space? Space already has a very, you know, it's a very high radiation corrosive environment. Our capabilities in autonomous operations are getting better. So it's actually an intriguing idea. I don't have strong views one way or the other. The Academy's report did have strong views. I don't think they wanted to see

just space tests bypassing a ground test. But yeah, it's something, I mean, it's something we need to continue to think about. So let's move on to nuclear electric just a little bit to kind of emphasize again some of these challenges. And you've given a few previews of this basically, which is, so nuclear electric, again, it's using conceptually technologies we know how to use in pieces, right? We've done electric propulsion for, I think, Deep Space One, Dawn spacecraft uses xenon thruster. We're developing kilowatt scale electric propulsion for the Gateway. We're talking here about megawatts. So we're just scaling that up to a huge degree, and then using a nuclear fission generator to create basically there's a ton of electricity to drive this type of thing. So what are the fundamental challenges from just

doing that, that you said, we don't know how to even start doing these? Why? You know, what are the key things that we don't know how to start doing? So I'll tell you one really key one on earth, you know, just from sort of, you know, from college physics, you may remember that when you generate electricity, only about a third of it actually gets converted into into power, remaining two thirds, just, you know, is heat and it's waste heat, right. And on power plants on earth, we just, you know, we have pooling towers, we have, you know, all sorts of kind of ways to conduct away that waste heat. In space, there's no atmosphere. So conducting away waste heat is an enormous challenge. If you've seen, you know, if you remember 2001,

a space odyssey, you know, the big spacecraft, there's an NEP one. And, you know, even actually in the Martian, you see these big things that look like solar panels they're actually fins to to radiate away that heat and these there's just such an enormous amount of heat we need to get rid of that it's a third the size of the the solar panels on on the ISS so so we do not know how to get such large amounts of heat in a quick way. And then you already mentioned the electric thrusters we are currently working on are the ones that were used for Dawn and other space missions, wherein the single kilowatts or tens of kilowatts, right?

So now we need to be having megawatts of power at the thruster end. Again, the scale up is a huge challenge. And it's a scaling, not just those peas, but for each subsystem, there is a scale up challenge. And then you need to combine it with a compatible chemical system, because NEP by itself, nuclear electric propulsion by itself, it will not have the thrust we need to get to Mars, especially for human missions. So the proposal for NEP is always combining it with a chemical system. So now you need to make that marriage happen.

We need to do a lot of cryogenic fluid management research, modeling and simulation research, testing safety, and other sorts of regulatory research. And a lot of these work can can happen in parallel. But there's just a extraordinary amount of work that needs to be done to make nuclear electric propulsion systems come to fruition. There's something you said there that I was trying to wrap my head around in the report, I didn't feel it was discussed as much. So nuclear electric that we're talking about here, you and you kind of mentioned this earlier, it's incredibly efficient, but it's very low thrust, right? Like it has to fire for very long

periods of time to change your velocity. And so in order to get humans to Mars within the time scales that were kind of these upper bounds provided by NASA to consider this report, the committee said you basically have to also augment that, as you just said, by additional chemical propulsion. So like in order to get you moving like out of the initial gravity wells, right? Is that right for Earth and Mars initially, and then you can use nuclear electric in between? Yes. These are big chemical propulsive things. And it was like, did I read this correctly? Because do you not then get any time advantage with a nuclear electric propulsion system? If you're worried about getting there fast enough that you need to augment it with chemical propulsion? Do you save any time on the transit compared to nuclear thermal? Or is this just because it's

efficient, it's useful? Yeah. So I mean, just so in the in the study, we we kept the time as a as a constant. So we were looking at, I think, a 650 or 750 day round trip. And we didn't change that for NTP or NEP. And we work backwards from that to figure out, you know, some of those details. So so looking for a time advantage wasn't wasn't our goal. Our goal was to understand more. If this is the ISP requirement, this is a round-trip requirement, what is the NEP system that's needed? What megawattage would we need the reactor to be? What would be the level of the chemical propulsion system?

And then, of course, we worked from that to developing a roadmap. How would you actually get from here to having a working system by the end of the 2030s? So yeah, so to answer your question, we weren't looking for a time saving out of NEP. Is that the correct interpretation, though, from my end, that if you are required to add a chemical propulsion system to keep that same amount of time, that NEP is generally going to be slower than nuclear thermal? Is that fair to say? So I think for the single megawatt, so you could have a 200 megawatt. Sure. Right. So then you can match up. But our current capabilities, we don't even think anything more than one to two megawatts is feasible. So the answer, you would be correct if we were only looking at those small levels.

But eventually, you know, at some point, NEP would be capable of doing everything. NTP level speeds, science level power. But for the moment, for the next 20, 30, 50 years, I think if we need high thrust, we need to combine NEP systems with chemical systems, which is why NEP is great for science missions because over long periods of time, tens of years, you can get very high levels of acceleration, right? So over time, you can get that velocity you want. But Mars in the grand scheme of things isn't as far away as, you know, Pluto or the Kuiper belt. Right. So let's start talking about some of the policy implications of all of this in our last few minutes here, because people hear nuclear, and I imagine

there's a good segment of people who might be worried about safety, right? There's going to be a lot of, I imagine, regulatory issues that you've already mentioned in terms of environmental control and safety for analyzing nuclear materials. We're talking about here, uranium, right? We're not talking about plutonium, naturally decaying, creating heat, we're talking about fissionable materials. And so what are some of the big policy challenges that you see that are going to be slowing down or potentially complicating this process, either side, whether it's nuclear electric or nuclear thermal, that we have to begin to tackle? So if you'd asked me this question a couple years ago, I would have had a different answer. In 2019, there was a presidential memorandum on how nuclear systems could approve launch or how the government could approve the launch of nuclear systems. And there was a policy in place before, but it was very high level.

It was very vague. We didn't even know if it really could apply as well to nuclear fission systems. So in 2019, the policy was updated. the policy was updated, it really laid out very specific ways on how you would approve, for example, an RTG system or a nuclear system with highly enriched uranium versus low enriched uranium. And it's a very stepwise, detailed process will take many, many years to get through. You know, first you have a NEPA, National Environmental Policy Act statement that says, you know, what the environmental effects would be. Then there is a detailed safety analysis called SAR, safety analysis report, which report is then reviewed by this interagency nuclear safety review board, which includes all federal government agencies. This board issues a report called the SAR,

the safety evaluation report, which depending on the level of risk of a launch, would either go to the president or stay with NASA. So there is a process in place which would help regulate a nuclear launch system. So that is no longer as much of a challenge. I mean, obviously, there's a public perception challenge, which we just need to work through, right? We just need to explain that nuclear reactors, when they're launched, they are not launched active, right? It's a cold reactor, and it's basically just a metal that gets launched, and the reactor isn't turned on until it's in deep space. And actually, this is a really interesting thing. You know, at launch, 3.5 kilograms of plutonium-238, which is what's in an RTG, you know, has about 60,000

curies of radioactivity, whereas 30 kilograms of uranium has about, you know, single-digit units, curies of activity. So a fission system is actually a lot safer for launch than an RTG system. And these are the sorts of things we need to communicate with the public. We are a democracy and, you know, what the public says matters. And it is, you know, it behooves us to do our job, to explain. I kind of wonder about this, this policy, again, of just this, the environmental review, the safety review, are those types of things, I have to say this carefully without, the safety review, are those types of things, I have to say this carefully without, you know, being blithe about it. But I mean, they're coming out of hard lessons learned in terms of dismissive approaches to safety and environment in the past. But at a certain point, are they limiting the

amount of technology that we can develop, even if they were created for good intentions. I mean, it sounds like to some degree launch is being revised. But I was thinking a lot of this work is going to have to be done through the Department of Energy, just in my very limited experience with the Department of Energy working through plutonium, which is, again, non weaponizable level of plutonium. They're quite secretive. And, you know, there's all this environmental additional cost to launching missions with plutonium because of all these environmental reviews. Are those things worth reconsidering for these specific situations? Or is this kind of an inevitable outcome of working in this nuclear arena that we have to just accept a heavy regulatory burden that's going to add cost and add time?

I think one reason DOE had a lot of bureaucracy around plutonium is because it is weapons grade, right? So they actually had to put that heavy bureaucracy on top of the plutonium generating infrastructure. And, you know, if you've seen some of those diagrams, you know, you produce plutonium by irradiating neptunium-237 targets at Oak Ridge, you know, sort of one DOE lab, and then it gets transported to, you know, another DOE lab, and then it goes to Los Alamos to get separated. So there's a lot of process and a lot of transportation which needs to be protected. My sense is that for fission systems, it may not be as onerous, mostly because we have, you know, we plan to use low-enriched uranium,

which we have a lot of experience and expertise. I mean, the United States has had nuclear reactors for, you know, many, many decades, and the Nuclear Regulatory Commission has figured out how to make transport, et cetera, in safe ways. So my hope is that for fission systems, the bureaucracy would be less onerous. The other part, and we've kind of been touching on it throughout, I mean, I think there's a lot more private sector interest in space nuclear systems. And I think they have put pressure on the government to make some of these rules easier to understand, easier to follow. And some of that is underway as well.

And I think as more commercial entities enter the fray, the easier things may become. And RTGs are a good example. So right now we have this one plutonium 238 driven RTG. So, you know, right now we have this one plutonium 238 driven RTG. These commercial companies that I know about, they are producing RTGs from other materials that are not weapons grade. They don't have to have, you know, an RTG is, you know, 110 watts. But what if you only need a few milliwatts for, you know, keeping an instrument warm on the moon? But you're stuck with this super expensive, because the government only has, it's like Ford said,

as long as you can have any color you want, as long as it's black. So these new companies are coming up with ideas with much smaller RTGs, which will have a totally different regulatory regime. And that's a good thing. Is there any fundamental, when people hear commercial companies doing nuclear work, is there any reason we should worry beyond what government does?

I mean, they're bound, obviously, by safety standards and so forth. But at what level can private companies work with nuclear material? And is it really, again, this distinction between what's weaponizable versus not? Is that going to be the fundamental difference between the two regimes? Great point, Casey. In fact, that is one reason NASA chose to... So all of NASA, not just all of NASA, in the whole entire world, every reactor we've ever launched has been highly enriched uranium. The one we launched in 1965 and the dozens of reactors the Russians have launched, the Soviets launched over the years, all HEU. NASA has made a decision, a conscious decision to switch to low-enriched uranium.

And one reason for that is it reduces the barriers to collaborate with the private sector, reduces the barriers to collaborate internationally. And it grows the number of players that can be involved. It doesn't have to be just DOE labs. We can work with private labs. Other people can get involved. Startups can come into the game, as we've seen that happen in recent years. Last question is something that I've been stewing on for a while. I'd be very interested to hear your thoughts on this, which is, we're looking at nuclear, whether it's thermal or electric just to put aside we're looking at this opportunity to say we could invest in a fundamental technology advancement

that obviously can enable changes and advantages to sending humans to mars but a lot of things as you just said commercial interest um there's a scientific interest in having these propulsive systems but we just mentioned commercial stuff, they're not going to make these scale of propulsion systems. This is a fundamental government R&D thing. It's not going to be cheap to do this. I was just kind of for context, I was looking back to the 60s about what NASA was spending on its nuclear rockets propulsion systems at that point, it scales out to roughly rough numbers, half a billion a year. NASA's right now spending 100 million. So we'd need to ramp up a lot to really tackle this. Is there so much value in doing this type of fundamental advancement and propulsion for sending humans to Mars that it's

worth waiting until this is done, and then designing missions around this enabling technology? designing missions around this enabling technology? Or is this something that can only or should happen in parallel with getting humans to Mars using the technology we have now? Or should we prioritize getting humans to Mars with the technology we have now instead of using that money to do nuclear propulsion, which, you know, won't pay off for 20 years? How do we make that decision given a limited set of resources to work with? Wow, really great question, Casey. And we'll take a lot of thinking by a lot of people. My initial reaction to that question is nuclear propulsion isn't just about getting to Mars. You know, we want to be a spacefaring civilization, not just for getting humans out into the solar

system, but getting science, you know, robotic missions out into the solar system, but getting science, robotic missions out into the solar system. You know, this is a technology we need to eventually develop. So there is no reason to not get started. Having said that, I think that if there's alternatives that we are seeing, we should be supporting them. So again, I'm just thinking aloud here. So if, for example, SpaceX is planning to go to Mars with chemical systems, I think we need to see how they're doing and if there's ways that can be supported. Because if they can focus on that piece, maybe NASA can focus on

NEP, which is sort of long-term, you know, everything. And the very initial thing we need to do in terms of thinking what limited resources, what do we do? I think nuclear power is a higher priority than propulsion. When humans get to Mars, they will need power. Mars is, you know, 1.6 times farther away from the sun, and there's 50 to 60% less solar flux. Solar power is not an option on Mars. And you remember what happened to the Opportunity rover, all covered with dust. You know, so if even if we do put solar panels, it'll be the size of a football field. In fact, somebody I was speaking to was kind of saying five football fields if we if we account for dust storms. So let's start with power.

It's not as expensive as propulsion and it has traceability to propulsion. So, for example, for NEP, you know, the core is power. It's not as expensive as propulsion. And it has traceability to propulsion. So for example, for NEP, you know, the core is power, right? So if we start with power, we can continue to make it out to go to NEP. Obviously, it will be small NEP, as in NEP for science missions, not the human missions, but that's a start. So that's kind of my recommendation. And I think the direction NASA is going in as well, although obviously we have a lot of constraints, we have congressional direction to invest in NTP, and we will, we always follow the law. But I would say that power is something we need to prioritize over propulsion for the moment. And power, of course, works at the moon too,

to the more immediate needs for your two-week lunar night, in addition to Mars, right? Power is like a fundamental constraint in space that you're always working against, right? And the more power you have, the more you can do with it. So that's an interesting point. And then again, that's the frustrating contrast to me is that it looks like, you know, nuclear thermal seems like a very useful as propulsive, in my opinion, more than nuclear electric, just because of the thrust advantage. But then you don't have that multi-use utility that you get from nuclear electric, where you're just generating all this electrical power. So nature has not done us a favor in this decision.

Unfortunately, we have to like, really think through this. But again, that's kind of the point. And what's exciting to me, fundamentally, why I enjoy this report and why we're looking into this is that this is being evaluated and committed to in a very serious way. And I think we haven't seen in decades, this could be one of those fundamental enabling technologies that we finally start investing in again, that can really change how we get into space and stay in space. That's exactly right, Casey. I think in the past when we started and then we stopped and we started and we stopped,

it was almost one step forward, two step back. However, I am very optimistic that this time it is going to stick. Not only do we have this launch approval, we actually have Space Policy Directive 6, which lays out a national strategy for responsible and effective use of space, nuclear power and propulsion. There's an executive order that requires that NASA develop a plan for human robotic missions using nuclear systems through the 2040s. The Biden administration is supportive of at least surface power. So I think there's a it's a things, you know, the constellation is coming together at least surface power. So I think there's a, it's a, it's a things, you know, the constellation is coming together as they say, and I'm, I'm super excited that we

will finally be moving forward. Great place to end it. Bhavialal, thank you for joining us on this month's Space Policy Edition. Let's stay in touch and join sometime in the future. There's always so much to talk about. It was so fantastic to talk to you, Casey. Talking to you is always sort of, you know, brain expanding for me. You know, love, love everything that Planetary Society does. A proud member and keep doing the good work. Thank you. Casey Dreyer and his guest, Bhavya Lal of NASA, often founded NASA headquarters nowadays, advising the new administrator. Great conversation, Casey. This is one that a lot of us who are science fiction writers and believers in a future where we zip around the solar system,

we've been looking forward to for a long time. There are all those other concerns that you began to talk about with Babia, though. Absolutely fascinating. That's all we need to do today, except that I will remind you of Casey's newsletter that you can subscribe to, that monthly newsletter we talked about up front. Do you have that URL in front of you again, Casey? Yeah, it's the Space Advocate Newsletter. You can search for or planetary.org slash space dash policy. And we'll link to it also in the show notes for this episode.

Also planetary.org slash join. The most important URL we will give you today. No slight against the newsletter. One enables the other. Exactly right. And this is the enabling URL. It's the one that will allow you

to join us at the Planetary Society. I'm a member. Casey's a member. We would love to welcome you. And we're very happy to have welcomed you once again to the monthly Space Policy Edition. We will be back almost certainly on the first Friday in September of 2021. Till then, we'll have several weekly episodes of Planetary Radio for you that I hope you'll join us for.

Some great guests coming up there as well. Casey, keep up the great work, and I look forward to talking again soon. Always good to be with you, Matt.