Check 6 Revisits: Atomic Ambitions—Destruction To Discovery

In the decades since two modified B-29s dropped atomic bombs over Hiroshima and Nagasaki, Japan, bringing World War II to a close, there have been many ideas about how the power of the atom might be harnessed for other uses, including space exploration and aircraft propulsion. 

On this episode, Aviation Week editors comb through our archives to discuss the legacy of the atomic bomb missions and the evolution of nuclear power in aerospace through to the present day—and beyond. “We hold in trust a power that is capable of unraveling the very fabric of our civilian…We have proved the destructive use, while the constructive applications are still in the realm of speculation.”-AW&ST, Sept. 1945

Check 6 Revisits delves into Aviation Week's more than 100-year archive. Subscribers can explore our archive here and read key Aviation Week articles related to this episode here:

• ‘Atomic’ Aircraft Development Seen Far Off By Industry Heads (Aug. 13, 1945)
• Army-Navy Post-War Plane Needs Seen Large Despite Atomic Bomb (Aug. 20, 1945)
• The Atom | New Source of Energy; A Tide In The Affairs Of Men (September 1945)
• Atomic Transports 15-20 Years Away (Feb. 6, 1956)
• Nuclear Reactor Tests Include B-36 Flights (Jan. 16, 1956)
• The Soviet Nuclear-Powered Bomber (Dec. 1, 1958)
• Skunk Works Reveals Compact Fusion Reactor Details (Oct. 15, 2014)
• Debrief: Signs Of Life For Russia’s Nuclear-Powered Cruise Missile (Aug. 18, 2025)

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AI-Generated Transcript

Christine Boynton: Welcome to Check 6 Revisits, where we comb through more than a century of Aviation Week and Space Technology archives. On this podcast, our editors explore pivotal industry moments and achievements of the past while considering how they might relate to the events of today. I'm your host, Christine Boynton, Aviation Week senior editor for Air Transport. And on this episode, we start out in 1945.

President Truman: With this bomb, we have now added a new and revolutionary increase in destruction, to supplement the growing power of our armed forces in their present form. These bombs are now in production and even more powerful forms are in development. It is an atomic bomb. It is a harnessing of the basic power of the universe. The force from which the sun draws his power has been loosed against those who brought war to the Far East.

Christine Boynton: What you've just heard is President Truman speaking from the USS Augusta on Aug. 6, 1945, as he announced that the United States B-29 Enola Gay had dropped the atomic bomb Little Boy on Hiroshima, Japan. Three days later, a second atomic bomb was dropped on Nagasaki, one known as Fat Man, by the B-29 called Bockscar. The destruction and death toll were catastrophic and the Japanese government accepted Allied surrender terms on Aug. 14, 1945. In an attempt to understand this force one unlike any other seen before, a report published by Aviation Week three weeks later offered an account of all the known facts and explored the implications of atomic power. "We hold in trust a power that is capable of unraveling the very fabric of our civilization," wrote then-President of McGraw-Hill, James McGraw Jr. "Equally, it may be susceptible of development as a mighty force for human welfare, but we have proved the destructive use while the constructive applications are still in the realm of speculation."

In the decades since, civil and DOD authorities have explored how the power might be harnessed for other uses, as that editorial suggests. The idea surfaces in our archives throughout the years, one 1956 headline optimistically stating that atomic transports could be 15 to 20 years away, but for reasons we'll get into, the technology never came to be. Today, we may be coming closer to realizing some of the things that they were talking about all those decades ago. Joining us today to get into this topic are Aviation Week defense editor Steve Trimble and senior editor Guy Norris. I gave a pretty high-level overview at the start. So before we get into it, Steve, could we back up a little, and can you talk about those two missions in 1945?

Steve Trimble: Yeah, sure. Obviously these are sort of fraught things to talk about when you're talking about deployment of nuclear weaponry, and it was even at the time. Notwithstanding that, to get into the details, there were a lot of things preceding this. Obviously the Manhattan Project was what led to the creation of the atomic bomb. The demonstration at Trinity test site the month before proved that this theory of splitting an atom, creating fission and harnessing the energy to generate this type of explosion, proved it could be done. That gave Truman the confidence to go to Potsdam where he met with Stalin and Churchill and they issued the famous Potsdam declaration where they warned Japan to surrender immediately or face significant dire consequences. Japan did not heed the warning, nor did they believe that there was anything like an atomic bomb in development. And so the mission was authorized to proceed.

And of course, Col. Paul Tibbets famously of the 393rd Bombardment Squadron with the Enola Gay, took off from the north field of Tinian at 2:45 a.m. local time, flew about six hours to Hiroshima and released the bomb, known as Little Boy. It was fused to explode at 1,800 feet over the target area in the central area of Hiroshima, letting the blast wave go down and spread out, which then of course created the mushroom cloud effect. For Tibbets and his crew, what he knew was that after releasing the bomb, he had about 45 seconds or so to get as far away as they possibly could, get the aircraft away so that it wouldn't be affected by the blast. So they do a hard turn back in the other direction and accelerate as fast as they can to get, I think it was 11 miles was the minimum distance.

They were told by the Manhattan Project scientists that they needed to be in order for their aircraft to actually survive the blast, which of course they did, although they felt when the blast or when the shockwave from the blast hit them still several miles away, it was enough to cause a 3G load on a bomber, which on a four-engine large aircraft feels pretty rough. But they were able to get back and land. And of course Japan did not immediately surrender. And the second mission was authorized. It was actually authorized to go after a different target than Nagasaki. The primary target was Kokura, but the clouds prevented the crew in Bockscar from hitting that target. So instead they went to their secondary target and were able to release their bomb in the same way. Now, there was a difference between the bombs. The first one, Little Boy was an enriched uranium gun activation type bomb, whereas Fat Man used by Bockscar on Nagasaki was a plutonium weapon and it had a very similar effect, although the topography of Nagasaki made it a lot different, shielded some of the areas, whereas Hiroshima was on a flat plane.

And of course we all know five days later, that's when Japan agreed to formally surrender with the one condition of allowing Emperor Hirohito to remain in his post. Although subject to or subordinate to the Supreme Allied Commander, in that case, Gen. MacArthur.

Christine Boynton: And Guy, I think you actually met Capt. Paul Tibbets, right?

Guy Norris: Yes. Thanks Christine. I did actually. And he struck me as being a very no-nonsense guy, very straightforward, very down to earth and very, very intense actually as you'd imagine for somebody who'd been promoted and given that awesome sort of responsibility. The things that he mentioned were the fact too that obviously the B-29 itself was a pivotal aircraft at that time. It was the only aircraft that could safely deliver these payloads over Japan at that time because it was capable of such high altitude and long range and such a high heavy payload. And his attention to detail was such that when he got involved in the program, he actually went to the factory where there were four factories that made the B-29, and this one was in Omaha, near Omaha, Nebraska. It made 536 of the, I think 3,970 B-29s ever built.

And he knew from his early experience of basically taking over development and test of the B-29 that this aircraft, because of its massive wing, had this huge great big wing, was able to get higher and faster than most fighter aircraft at the time. So he thought altitude is the key. So they ordered these specially modified B-29s with 7,200 pounds of weight removed to make them capable of even higher altitude. And they did this by basically taking out all of the gun turrets apart from the tail guns, which was the only sort of self-protection that they left. And they also took out a lot of the armored protection for the crew as well. So they basically sacrificed a lot of their self-protection for safety of altitude. They also augmented the fuel with 600 gallons of extra fuel in the aft of the aircraft.

So these were really specialized versions. The world's only purpose-built, if you like, nuclear bombers. And they were called the Silverplate versions, and he ordered 15 of them. I mean literally he was the one that signed off on this, ordered 15. And as he was walking around the production line, somebody came up to him and said, "By the way, Colonel, if you want one of your better airplanes, you should go for this particular one, 86292. It's the only one we've gone through the tired testing with and didn't get a single writeup. She's absolutely beautifully made." So that one ultimately became Enola Gay, which was named after his mother. So anyway, just talking to him about the actual mission, the things that really struck out to me, and this Steve mentioned this in his introduction there, was that he took advice from Oppenheimer himself. Robert Oppenheimer, of course was the scientist, the chief scientist leading the Manhattan Project.

And he said, "How do I get away from this thing?" And he said, "Turn tangent to the ever-expanding shockwaves." And he actually said, "You'll need to go 159 degrees in either direction away from the blast." He said, "Well, I didn't have 159 inscribed on my instruments, but I went for 160, which is close enough." And he said he practiced, Steve mentioned he only had 42 seconds before he knew the bomb was going to explode. So he made this 160-degree turn, which at altitude, I mean he dropped from 31,700 feet. And because the air's so thin at that altitude in a B-29 turning rapidly to try and get back away from the bomb meant that the aircraft was on the verge of stalling. In fact, the tail was stalling as he was making that turn shaking the aircraft. "We practiced it over and over, told the rest of the crews how they could do it, and finally got this 160 degree perfected."

The bomb exploded. The turn took 40 seconds. So he had two seconds there as he was racing away. And as Steve mentioned this massive shockwave, there were two shockwaves. The first one hit the aircraft directly from the blast itself. The second shockwave hit the aircraft that had bounced off the ground and then up and hit the aircraft. And he said the airplane crinkled, what was his word for it? Crinkled as it struck it. He was exhausted. At the end of it, he went to sleep in the little tunnel, which connects the two pressurized compartments of the B-29. The tunnel kind of lies between the cockpit section and the aft section. So he must have been exhausted. And then the other thing I think we should just quickly mention is the second mission, Bockscar, that you mentioned, Christine, in your intro. The amazing thing about that was how close it came to calamity. This fuel tank that I mentioned earlier on in the back, just before takeoff, the electrics controlling the fuel transfer failed.

So it was too late to get rid of the fuel. They had to go on the mission, but at the same time they couldn't use it. So they were overburdened and took off with this reduced fuel load. They dropped the Fat Man bomb that Steve mentioned. And because of issues getting there, when they got to the target area, one of their escort aircraft hadn't showed up. They'd spent almost an hour waiting for it. So they had all that fuel burnt as well. So by the time they got to having decided Kokura, the weather was no good. Getting over Nagasaki, the secondary target, they only had enough fuel for one actual run, and it was still mostly cloudy over the area. So they decided to do a radar-based target run, which again consumed more fuel. But at the last minute, a hole in the cloud opened up and they were able to do a visual delivery with that weapon. By then, they knew they couldn't get back to Tinian, they didn't have enough fuel, so they diverted to Okinawa, which was 350 miles away. As they approached the airfield, one engine died from fuel starvation. Second engine died on touchdown. The third engine stopped as they were rolling out. So by the time they switched the engines off or the last remaining engine, they only had seven gallons of fuel left. So it was an astonishingly close call.

Christine Boynton: Wow. Well thanks for that, Guy. And Steve, I wonder if we can move a little bit into Aviation Week's coverage of this. I sort of talked about it a bit in my intro, but they were looking at the atom as a new source of energy. The seven-page report called it "A Tide in the Affairs of Men," and you put together kind of an incredible list, Guy, of past headlines from 1945 to 2023, which I think really illustrates the kind of ebb and flow of ambitions for this technology. I think maybe you could also give us just a quick nuclear 101, difference between fission and fusion, that kind of thing before we start getting into those archive pieces.

Steve Trimble: Sure, yeah. A quick tutorial on fission versus fusion.

Christine Boynton: In 30 seconds, go.

Guy Norris: Right, okay, fission versus fusion. Well, obviously there are two different ways of releasing nuclear energy. So this nuclear energy is a sort of unit, it's energy that's released from the nucleus, the core of atoms, and of course the core of an atom is made up of protons and neutrons and within each atom is a nucleus. So that's the tiny, tiny packed core which holds the protons and neutrons that are bound together by something called a strong nuclear force. So when a neutron strikes the nucleus of certain of these atoms, say uranium that we've talked about here already, the atomic center can sort of break into pieces. And that process is called nuclear fission because it's breaking apart, and that process releases enormous amounts of energy in form of radiation and heat. So that's the basics. So if you can imagine that nuclear fission is the process that was used in the bombs, nuclear fusion is another way of releasing nuclear energy.

Whereas fission involves sort of splitting these heavy unstable nuclei into two lighter nuclei, fusion is sort of the reverse. It combines two light nuclei to form a heavy nucleus. So in very simple terms, nuclear fission is this splitting of these uranium or plutonium nuclei, whereas fusion is like the sun, it's all the stars. They generate this, all the light that you see from the sun is generated through a process of nuclear fusion. So two very different ways of getting energy from the same sort of fundamental source.

Christine Boynton: So this was kind of like a sudden awakening of power and weapons possibilities. What were those early reports? How were they seeing this technology?

Guy Norris: Yeah, I mean I think what struck me about it, and Steve mentioned it's a difficult subject now to talk about, but at the time I got the feeling that Aviation Week was very pragmatic about the whole thing, and it was a raw kind of time. The war was literally days over, it was just over a week or so when we started to write about it. And the whole attitude was very different I think to what it probably is in the sort of reflection of years gone past sort of thing. I think looking in the rearview mirror, it's easy to see why these precepts and conventions had changed. But at the time I think that the big realization was that this was a massive leap in available energy source. It was a huge leap in strategic capability. It just was a world-changing discovery and really science had managed to do something together with the massive might of the U.S. industry to do something that nothing like this had been achieved in the history of humanity.

And so there were all of those great big realizations in the first few weeks. To me there was very little attention paid to the human cost. Obviously as I mentioned, the war was just over and it was still very much "we did it, we won and it's over." But at the same time, the focus was much more on, well, where can we go from here? This is like a dream come true. We have this almost inexhaustible energy source. We can do anything with it. So I mean, looking through some of the coverage, I mean, I'm looking at one for example, this is actually from I think 1951, but it goes "the heat that vaporized Hiroshima and Nagasaki was released in the millionth of a second. It was unled, uncontrolled power production, but there were thoughts of controlling it, ways to slow down the process and make the enormous power reserve in the atom available to drive turbines, wheels, propellers." And that was literally the start of it. And what we see over the entire run of the fifties is this incredible enthusiasm for getting it into airplanes. Later on, you see it starting to get into rockets for space travel and massive use of it to replace even the power in road vehicles or trains. It was anything you could use this for. It was the next big thing. But of course, as we know, the truth turned out to be a lot more difficult than that.

Christine Boynton: And Steve, I think at one point there was an article you found that was questioning all the major aircraft manufacturers, whether this would mean a need for fewer military aircraft.

Steve Trimble: In fact, that appeared just a couple of weeks after the bombing on Nagasaki, and you really do. Guy alluded to this, I think very well. You have to put your head back into what it was like in mid-August, 1945, 80 years ago, this war that had been fought in Europe for the last six years and in Asia for eight years had suddenly spectacularly come to an end when everybody thought it was going to continue for at least a couple of years. And suddenly this changed. And so there was this, everybody was just sort of scrambling. You have to remember the War Department and the Navy Department in August of 1945, certainly some of them were aware that the atomic bomb was in development and coming and could have an effect on the outcome in the very near term. But you know that they were planning for the worst for Operation Downfall and landing millions of American and actually Soviet troops in Japan. So they were going to order more airplanes, order more bombs, order more tanks, order more artillery, order more bullets, order more ships. And all of that was so the defense industry was gearing up for all that or continuing to just maintain the momentum that they had created. And then all of that ends. And so now the defense industry is worried about this sudden collapse in demand. Now that's a good thing obviously for humanity, but it's an existential thing if you're the CEO of Lockheed or the CEO of Consolidated Vultee or even of Boeing.

And on top of that, you've got this whole new thing that nobody had really sort of absorbed. Obviously the scientists involved in the Manhattan Project were fully versed on what the potential of splitting the atom would be. And people have been talking about it ever since. The Germans actually created fission, successfully split the atom in experiments, I think back in 1939. So the physics community was preparing for this day, but really nobody else was. And so now it's like, well, with this new energy source, with this new raw material for explosives or for explosive power, what do we need? How do we think about the future? Is everything different? Do we need aircraft or do we need just one?

And so the entire industry is thinking about that. And Aviation Week did go ahead and interviewed several executives. They've got quotes here from, let's see, Harry Woodhead, the president of Consolidated Vultee, which would become Convair of course. And he says "to call a halt now at the end of the war on military aviation research and the manufacturer of planes to equip a strong Air Force would be comparable to a man canceling his life insurance after having just survived a catastrophic incident." Robert E. Gross, the president of Lockheed Aircraft had very similar comments. "The atomic bomb, rather than threatening the aircraft industry has done the industry a service in emphasizing the need for continued and aggressive research." They're already learning how to spin a negative into a positive and try to keep this going. And they're not wrong. Just in a few years, we would slip into the Cold War. At this time, the thinking was that maybe there wouldn't be. The Soviets were still our ally in the war.

Guy Norris: Well, you can say, Steve, I think you're right. There was one of your distant relatives, maybe G.S. Trimble, vice president of Advanced Design at the Glenn L. Martin Company. It was...

Steve Trimble: Definitely one of my relatives.

Guy Norris: But yes, he was asked, where is this atomic thing going? And he was quite sort of actually quite philosophical about it. He goes, "Maximum progress must await application of a motivation superior to the fear of war. Yet optimism in considering this factor leads me to believe that essentially all commercial transportation in 1985 will be via air in vehicles operating on principles not yet conceived." So well, I mean, it wasn't quite that dramatic, but there were much more realistic views from, I mean, for example, I'm thinking of Art Raymond, who very famously was vice president of engineering from Douglas Aircraft. He in fact had led the engineering team that designed the DC-3, one of the world's most famous airplanes. And in fact, I had the very great honor and privilege of flying on a DC-3 to celebrate the, I guess it must've been the 60th anniversary of the first flight of the DC-3 with Art Raymond actually onboard the aircraft.

It was shortly before he passed away, but it was an amazing thing to do. But anyway, Art Raymond said that he didn't think that by 1985, Aviation Week was asking where people thought airplanes would be by '85 and whether nuclear power would be part of this. And he said, "By 1985, I should expect all current civil aircraft to be in service somewhere. And perhaps, who knows, airlines will still be looking for a DC-3 replacement." He said he did not expect many aircraft to be flying at supersonic speeds because of the cost. All very true. But he really didn't see a role for nuclear, which I thought was interesting. So anyway, sorry Steve, I know I interrupted you.

Steve Trimble: No, no, sure. But anyway, everyone's trying to get their heads around this whole idea and what it means for the industry going forward. And in fact, military aircraft, notwithstanding the words of these defense executives, aircraft production did fall off a cliff after 1945, and the defense industry did go into a nose dive for a few years, and a lot of them tried to do other things. I think Boeing at one point started making refrigerators and stuff like that to kind of convert to the civil economy. But at the same time, there was this idea that maybe we could use nuclear, the principles of nuclear fission, not just for weapons, but also for productive purposes, not just for commercial energy, but also for military energy. Think of missiles that could fly for as long as you want them to with air breathing engines. Same thing goes with larger aircraft.

In fact, there was an article in Aviation News, our progenitor on Aug. 13, 1945, saying, "Overall though, success of the Manhattan Project and the atomic bomb attack on Japan have brought out initial speculation that the first fission reaction will be converted to aircraft propulsions through the medium of rockets." And of course, we knew that was pursued quite heavily through Project Pluto, which the goal there was to create a ramjet-powered fission reactor, or actually a reactor-powered ramjet to power a cruise missile that could operate for hours, days, for as long as you like. And there were other projects, obviously NB-36 with Convair. The nuclear-powered bomber obviously didn't lead to much. Lockheed Skunk Works worked for several years under a project known as WS-125 as weapon specification 125 to try to come up with a feasible design for a fighter, a tactical aircraft that would be powered by a nuclear engine.

Kelly Johnson, the founder of the Skunk Works, worked on that for several years. He published some really interesting papers on it as well as a little sketch drawing of the configuration at one point, I think in 1956 or '57, but ultimately abandoned it. And he wrote in his autobiography that it would take 40,000 pounds of shielding to protect the pilot from being immediately radiated from the reactor. That doesn't really work very well in a fighter. So that project was dropped as well, but the idea was still there, and we saw it in spacecraft, the SNAP-10A with radioisotope thermal electric generation or generators, that form of nuclear propulsion without something that's short of a reactor and just using the decaying isotope for energy. The Soviets actually used that to power lighthouses all across Siberia because it gave them this 80-year energy supply for these very remote facilities.

Just a bizarre side note, but the Soviets also took this much further. They used fission nuclear reactor-powered spacecraft through the, I think late 1960s to about 1978. And that's when Cosmos 954, one of their nuclear-powered satellites accidentally, mistakenly, I'm not sure what the right adverb is, reentered the atmosphere and crashed in Canada, creating luckily in a very remote area of Canada, which is most of Canada, and creating a radioactive problem that the Soviets, the Canadian government compelled the Soviets to pay for the cleanup of that. But when that happened, and that drove the whole industry away from nuclear-powered spacecraft for generations. And on top of that, there were other things that Three Mile Island happened right after that. Chernobyl wasn't that much further down the line. And of course more recently there was Fukushima in Japan with the effect of the tsunami and the meltdown of that reactor as well.

So they're having these concerns over time about using nuclear propulsion in space. That said, when you talk about space travel, and if you're talking about getting access to the cislunar space, the space out beyond the geosynchronous orbit, all the way up and even beyond the moon, and then especially if you're talking about going to Mars, certainly it's much harder to do it without nuclear propulsion. If you're just using solar or some kind of solar electric combination or even liquid fuel. You either need very large fuel supplies and somehow some way of refueling it, or you go with a nuclear reactor and that's a big thing, but it gives you not quite unlimited range, but a lot of range.

Guy Norris: Yeah. Well, just going to say, Steve, I think probably worth at this point, I know you want to talk about DRACO in a minute, but one of the things I was thinking about was probably we should say one of the two great ways of using nuclear power in space and the difference between them. And as Steven mentioned, obviously the nuclear thermal propulsion is the way that most sort of sci-fi writers probably look at it. Nuclear electric propulsion is the other option. So these are the two major ways of it. And what's the difference? They both generate thrust, obviously. So NTP, which is nuclear thermal propulsion, that directly heats a propellant with the nuclear reactor, and it's usually something like hydrogen and expels it for thrust. Whereas NEP, the electric one uses a nuclear reactor to actually generate electricity, which then powers an electric thruster like an ion thruster.

So NTP is really great because it has high thrust, it would be very dynamic. So you could use it as Steve mentioned, for say, cislunar operations outside the Earth's atmosphere in all the way to the moon and around the moon. It would be great for dynamic space operations, and it's got much higher, relatively higher specific impulse compared to chemical rockets. The great thing about that is say on a Mars mission, it would reduce flight times if you used it correctly by sometimes around a year. So you'd reduce the exposure of the crew to humans anyway aboard to cosmic radiation and that sort of thing. And you'd get there and back a lot quicker, of course. And the thing about the NEP option, however, is that it's great for really long endurance missions and it's got excellent fuel efficiency, so you wouldn't need such massive propellant tanks. And it's also great for station keeping, orbit raising and those sort of long duration missions, they reduce the need for large propellant tanks, and it's great for things like station keeping and orbit raising so much longer thing. But anyway, back to you Steve. I'm sorry, I was going on there, but I thought I was kind of intriguing to reference the difference between the two main in-space propulsion concepts.

Steve Trimble: Sure, yeah. And of course, I mean this is coming back. There have been attempts to make this comeback. The first was with DRACO, which got started in the last months of the first Trump administration, and then it was carried forward through the Biden administration. The idea was the Defense Department and NASA partnered together to create a nuclear reactor and a spacecraft and integrate them together, launch them, and use that as a spacecraft that could reach cislunar and perhaps even the moon. And depending on the mission, either the military would use this for its own type of spacecraft or NASA could use it for say, travel to Mars. Now, the reactor was a very special kind of reactor, and it's something that's come up pretty, it's a modern innovation in nuclear energy. That's a small modular reactor with high-assay low-enriched uranium.

This is uranium enriched to 20%, which is of course far below weapons grade. If anybody's keeping track of where Iran was with weapons-grade uranium, that was 90% was supposed to be the standard, even though it was only 80% enriched for Hiroshima. But the point is reactor is 20% enriched and uses special kind of fuel, these little pellets called TRISO fuel pellets. And the whole idea is that even if there's a failure of any kind, the chance of a meltdown is significantly diminished. That's the theory that has to be proven in practice. And there's all kinds of questions that you could ask about that. But in the case of DRACO, our colleague Vivienne Machi reported back in January after getting a long-sought interview for an update on where this project was because it kind of went dark for several months. DOD and NASA finally confirmed last January that they were putting DRACO on hold and phasing out the program due to the problem of trying to test a nuclear reactor on U.S. soil in the modern day with modern regulations and concerns about the effects of radiation. So that project has stopped. Now, we know China based on news reports in China, are pursuing something very similar. We don't really know how far along they are with it. It appeared they were a little bit further behind where DRACO was when it stopped, but we don't know anything more than that. But the idea of nuclear energy in space, maybe not for spacecraft, but for lunar bases also might still be a possibility.

Christine Boynton: And how about nuclear-powered aircraft projects, Guy? I think the ambitions along that track kind of died out maybe in the sixties or so. Where are we now and what was kind of a turning point for those ambitions to come back?

Guy Norris: Yeah, yeah. Thanks Christine. I think it's sort of worth looking back before we go forward very briefly. It's astonishing to me how early, we mentioned this early on in the podcast, but it's astonishing to me how early people grasp the idea of potentially putting this power into aircraft. And I've been doing some digging into this. And it turns out that six months before the first ever nuclear explosion at Alamogordo in New Mexico, the Trinity site test that Steve mentioned at the start, the Air Force actually began discussions with Dr. Vannevar Bush, who was then director of the Office of Scientific Research and Development on the possibilities of nuclear-powered flight, which is amazing to me. And then they followed this up with discussions with Maj. Gen. Leslie Groves, again, who Steve mentioned, who was head of the Manhattan Project. And that's sort of led to this contract in May 1946.

Can you imagine it that long ago between the Army Air Force as it was, and Fairchild Engine and Airplane Corporation to look at nuclear energy for the propulsion of aircraft or the NEPA project. I think this was, it wasn't officially taken up with the Atomic Energy Commission at the time, but they did make space available for NEPA at the Oak Ridge facility in Tennessee, which had been built as part of the Manhattan Project. And MIT became involved in this study group, and they were designated the Lexington Project to look at the feasibility. So I think what the force as it was becoming by then was really didn't like the results of this because the Lexington Group estimated that a program to develop a nuclear-powered airplane would take 15 years and cost well over a billion dollars. So they thought, well, we don't like that answer.

So as a result of these conclusions, the NEPA effort was phased out, and the AEC joined the Air Force in this sort of much more dynamic effort called the Aircraft Nuclear Propulsion or ANP program in 1950, which Aviation Week covered as much as it could because remember, it was pretty secret in those days. We only really used to get sort of very, very preliminary views of what was going on. But we did begin to build up a picture, and if you'd follow through our own archives, you'll see how we did sort of get mostly through congressional hearings and those sort of reports, some sort of vision of what was going on. But anyway, to sort of cut to the chase, the idea of ANP was to develop this hybrid propulsion system. So what you do is you combine turbojets with a reactor, and there were two real versions of it, ANP's two designs, General Electric looked at this direct cycle where the engine airflow actually cooled the reactor and the Pratt and Whitney's indirect cycle where they would take heat through a heat exchanger and use that instead to heat the airflow.

The Pratt effort eventually didn't go so well. So they changed their mind and went to this liquid metal coolant system, which carried heat from the reactor to the engines. They actually ground tested some engines as well. It's astonishing, really, a modified J-47, which was called the X-39, HTRE-1, that was in 1956. And of course, these were all supposed to fly or at least be flight tested on a modified Convair B-36, which was going to be called the X-6. That part of the project was actually canceled and didn't happen, but there was another B-36 famously converted to test the reactor in the air, and it was a tornado or hurricane damaged airframe, which was refurbished and made into this astonishing airborne test bed. And what it really did was it flew the reactor, the ANP project, but didn't actually connect the reactor to any propulsion systems.

It was just basically a way of saying, can we fly a reactor in the air and protect the crew and stop them from frying basically. So this is an astonishingly heavy aircraft. Even the nose section, which was purpose-made to protect the crew, was 12 tons of lead and rubber shielding. Even the cockpit windows with leaded glass between six and 12 inches, like 30 centimeters or something thick. It's amazing. They could even see out of it. And they put the reactor, they hung the reactor in the number four bomb bay. It weighed 35,000 pounds, but it was only one megawatt. Interestingly, when you think about hybrid electric propulsion systems that are being developed today, and this aircraft, it was called the NB-36H, and it looks beautiful, by the way, some great photographs of it that Steve and I have found. It clocked up over 200 hours of flight time, 89 hours of which the reactor was active.

And weirdly, every time it flew a Boeing C-97, which was carrying a platoon of Marines escorted it, and they were ready to parachute to the ground and protect the area if the aircraft crashed. You just couldn't make it up, could you? Anyway. But the point is that these efforts were made, these engines were run. And then you get to this point in the late fifties where the reality is beginning to set in, people are thinking these projects are just so heavy, they're so difficult to do. And as Steve mentioned earlier on, the shielding alone makes it so unwieldy and heavy to fly, let alone all of the pumping and the piping anyway, just when things were dying down, Aviation Week itself stoked the fires of this whole craziness, if you like, when it reported on Dec. 1, 1958, famously stories of what appeared to be a Soviet nuclear-powered aircraft turned out to be...

Steve Trimble: M-50 Bounder was the...

Guy Norris: Thank you. Yeah, fantastic. That's what it was turned out to be. It was an elaborate hoax, but really convinced a lot of people in DC that the U.S. was falling behind and that the Soviets were going to take a leap.

Steve Trimble: And it was immediately denied by the White House, one of Aviation Week's less glorious moments.

Guy Norris: But weirdly, I mean, it turns out that the Soviet Union was in fact doing similar tests to, of course, the U.S. with the modified B-36. They had a modified Tupolev Tu-95 equipped with a reactor, and they did in fact have all these plans to go the same way as the U.S. And of course, what happened instead was that we suddenly developed all of these very capable, long-range nuclear-powered submarines, which were capable of delivering ICBMs from hidden from beneath the waves anywhere around the world. It made this idea of these long endurance standoff aircraft completely obsolete. In fact, they were much more vulnerable. So from a strategic perspective, the whole idea of nuclear-powered aircraft basically lost its headway. And of course, in 1961, famously President Kennedy basically terminated funding. He said "15 years, and about a billion dollars have been devoted to attempting development of nuclear power aircraft. But the possibility of achieving a military useful aircraft in the foreseeable future is still very remote."

Steve Trimble: Well, I could almost excuse Aviation Week for just, they got the scoop on the Soviet nuclear-powered aircraft. They were just about 70 years too early, which in a way is a heck of a scoop because now we know the Russians, not the Soviets, but pretty close, well geographically, if not politically, but the Russians are pursuing a nuclear-powered missile, a nuclear-powered cruise missile. It was unveiled on March 1, 2018, by Putin. On the same day, the Ministry of Defense in Moscow released a video. What they said was a test flight of this new missile. They called Burevestnik, and I forget the actual nomenclature. I think it's 9M730 something. But the NATO, of course, they call it Skyfall. This missile has been in development. There was a horrific accident involving this program reportedly by multiple sources in 2019 that led to the deaths of several of the nuclear scientists involved in the project.

But there's been a lot of recent activity, in fact, just a couple of weeks ago, two arms control experts, Jeffrey Lewis and Decker Eveleth came out with photos that have been supplied to them from Planet, which has an orbital constellation of remote sensing satellites of the test site at Novaya Zemlya, which is the Arctic Archipelago where Russia does a lot of its nuclear testing. And that test site has been reactivated. There's been significant activity over the past few months, and there was a NOTAM issued around Novaya Zemlya in areas that have been previously used for Burevestnik flight testing. And that NOTAM lasted from Aug. 7 to Aug. 12. We know that WC-135 sniffer aircraft from the U.S. flew up north around the same time perhaps to check on something that was going on there. We don't have any further details about that or if anything indeed happened, but there's also been evidence of other preparations.

Eveleth and his, if you go to his Twitter feed, both in April of this year and September of last year, posted photos showing what he believes is the deployment site for the first Burevestnik company, launch company. And it's a fixed site. It's not a mobile site, and it's several hundred miles north of Moscow and several hundred miles east of St. Petersburg. And if that capability goes operational in the next maybe one or two years, it adds another very interesting weapon to Russia's arsenal, probably nuclear arsenal with that particular missile, not just in terms of the power source and the power generation, but also with the warhead itself. And there's no other weapon around that does that sort of thing. Now, there's a lot of argument over the value of something like that and whether it's really that beneficial for Russia to have a weapon like that, even looking at it from their perspective. But it does appear to be something that they're actively doing at the moment and ushering in really the first nuclear-powered aircraft into operational service. So in that way, the dream of nuclear-powered flight lives on.

Christine Boynton: And there's one other part I wanted to touch on is something in 2014 came out is this right Guy where we thought nuclear power for aircraft might be back on the agenda, something from I think Lockheed Martin.

Guy Norris: Yeah, thanks Christine for reminding me on that. And this is interesting, and in fact, in the story that we did, I did in fact reference the fact that Lockheed had quietly come out with this idea of something called a compact fusion reactor in 2013. But in 2014, I got this call to sort of say, come to the Skunk Works and come and see what we're doing on this. And it was an amazing opportunity to go inside the fabled, the sort of inner sanctum of the Skunk Works, go up into, it was all the way up. Skunk Works is the Palmdale facility. It's a very tall building. It was built to make, I think, Steve, the L-1011 airliners.

Steve Trimble: Oh yeah.

Guy Norris: In the late sixties. And so it's a very tall building. And this facility inside called T4 was housed in one of the sort of side buildings, sorry, side rooms inside the upper floors of this. Anyway, it was a project that was really run by Thomas McGuire, an aeronautical engineer in the Skunk Works' Revolutionary Technology Programs unit. And basically the idea was to, as we mentioned earlier in the podcast, the difference is is it nuclear fission or nuclear fusion? And of course, this was an idea to this sort of holy grail of power is really fusion. Fusion is probably, there's two great things about it at least. One is that you don't get this byproduct of radioactive waste that you get with nuclear fission. And the other thing is that you can, it's a safer process because if you can control it correctly, it just immediately stops.

If that control, it doesn't produce a sort of runaway chain reaction, which you can get with fission, which is what the bomb was basically. So the intriguing thing about fusion here, and the way that they were trying to look at it was you've got this fusion fuel, which in this case was made up of these hydrogen isotopes, deuterium and tritium, and that started off as a gas, which was injected into this sort of a containment vessel, and then they zapped it with radio frequency heating to break the gas into ions and electrons and forming this sort of plasma. So the big trick really was to control this super hot plasma in using sort of magnetic fields, which sort of prevent it from touching the side of the vessel. And this was the key breakthrough I think that McGuire was hoping to master, really.

And if you can control it, keep that confinement sufficiently constrained, if you like, the ions overcome their mutual repulsion and actually collide and fuse, and that process is the magic. That's what you want to happen, because that creates helium-4, which frees neutrons that carry this released energy kinetically through actually out through the magnetic fields. And these neutrons heat the reactor wall, which then you could wrap a heat exchange around the wall. And then that's, hey presto, that's where you get your heat to drive generators. So they thought this was the possibility people had tried since the 1920s, believe it or not, to try and work this out. And he thought that with a fresh mind team of youthful, enthusiastic researchers, he could come up with a way of cracking the nut on this. A lot had happened over the past 40, 50 years that could enable it, and it could be done on a scale where you could basically put it in the back of a C-130 and that, hey, there you go. Finally you get your nuclear-powered aircraft. As it turned out, of course, I can see Steve shaking his head here as it turned out, of course it was a bit over optimistic, but it did spark a lot of interest, and it did eventually, unfortunately, go the way of all of these projects far as we know. But it did in fact spark a lot of enthusiasm and reignite the possibility.

Steve Trimble: Well, I loved your very elegant and astute technical description of it. But the one thing that sort of leaves out is the fact that you're super heating a plasma to 180 million degrees Fahrenheit and you're containing it with that magnetic field. And that's a really hard thing to do because if you can't contain it, you immediately melt the reactor wall, what is it? 10 times hotter than the surface of the sun or even way hotter than that. I mean, it is this ball of not even fire compares to the energy at the center of the sun. So that's what we're talking about doing. And you can do it right. They have done it very successfully with these huge, massive tokamak reactors, fusion reactors. Now they're still trying to get positive energy out of those things, but as they scale them up, they think they can do that on the ground.

But with something that's the size of the Eiffel Tower or something like that, I mean, it's massive, right? And so what they're trying to do is use those cusp and the high beta pressure and all these other little tricks to repackage all that tokamak magnetic field into something that could be carried in a C-130 and still get the same kind of reaction out of it. That is a huge order now in the Skunk Works. I mean, they carried it through for several years and they got through, I think T5, their fifth reactor, but they were one experiment away from actually adding the deuterium and tritium, which would've required a massive investment, several hundred million dollars plus somehow getting California to agree to put a nuclear reactor on their property at Skunk Works. Or maybe they'd have to go somewhere else for it. But of course, that funding never happened. And I confirmed with the Skunk Works boss, I think in 2021 maybe, maybe 2022, that the program had been canceled as of 2020, I think or so. They just didn't want to make that investment and they weren't sure it was going to work.

Christine Boynton: So I guess we are coming to the end of our hour. We've touched on a lot, but where are we now? Are we behind, I know we mentioned DRACO very briefly. Was it shortsighted for that program to be cut off kind of in its prime, opening it up back to both of you?

Guy Norris: Well, just starting off, I know Steve really got into this in a big way around the cancellation time, but personally, yeah, I think as Steve mentioned, one of the critical reasons it was put on ice and basically shelved was the fact that it was so difficult to test in anything like any configuration before launch. So you have to have this willingness to accept the risk of launching a system into orbit that has never been fired up and tested. And I think that's where people are still not comfortable doing that's massively costly, it's hugely risky, and it's a real chicken and egg situation. So I know Steve probably got more comments to go on this, but I think that inevitably it will happen. I think the attractiveness of NEP or NTP is just too great to give up, and it's a natural evolutionary development for humanity's exploration of space, let alone any defense requirements or sort of dynamic space needs. So for military purposes. But I just can't imagine our future without some form of nuclear power in space. It just doesn't make sense.

Steve Trimble: Yeah, I mean, two things could probably happen if the small modular reactors that are using HALEU with TRISO fuel pellets work out, and the Nuclear Regulatory Commission and other stakeholders in that whole process start becoming comfortable with the idea of this. I think it makes it a lot easier for a U.S.-based nuclear reactor project for spacecraft. And the second thing is we don't know what China's going to do. Maybe the ball's in their court, maybe they're going to hit it out of the park and do something that we can't do because of our regulatory structure. I don't know. China is not a reckless actor in that regard. Their commitment to safety is pretty well known. I wouldn't see necessarily a crash effort in that sense, in the pejorative version of the sense, but this may be an opportunity for them to gain an advantage.

Christine Boynton: And one thing that I've seen that is really interesting is this idea that actually AI might push the development of small modular reactors forward. Why is that Guy, can you speak to that?

Guy Norris: Well, I think in every aspect of advanced technology right now, we're seeing this huge impact of AI, whether it's real or not, it's still to be determined. But the main area that you see, particularly in things like small modular reactor where there's been decades of fundamental work already done, is the fact that AI is bringing a faster pace of iteration with design concepts and testing of those concepts, at least in a sort of virtual sense. So I think that it could be coming at the perfect time to help push these processes into reality again. And I think that there's certainly an appetite for small modular reactors now. And as Steve mentioned, the fact that there's this low-enriched uranium availability, which, and the reason that's so interesting is that it's basically, it's a non-weapons-grade material. So that kind of makes it attractive from the nuclear proliferation side of things, which has been a huge great big hindrance to development over the decades.

And you're seeing even Denver Airport for example, recently looked at, put out an RFI for its future expansion, initially included the possibility of a small modular reactor as part of that. I mean, that's unthinkable, isn't it? Even a few years ago. As it turns out, they withdrew that. But the fact that it was even mentioned, I think is something to show that the pace is picking up and people are becoming more aware of it. And one last thing I should say is that AI, the massive energy demands of all of these systems are itself, is itself driving the need for greater and greater energy supplies, and which cannot literally be met at the moment the way things are going with either sustainable or non-sustainable traditional fuel supplies. Steve, I can see you dying to say something.

Steve Trimble: No, no, I totally agree. And I really do hope that at some point, ground-based fusion reaction, not a compact fusion reactor, I think that's very difficult to achieve, but a large-scale fusion reactor that would be perfect for that because of significantly reduced environmental hazard, you just need a handful of water to power it for years. And it would be a massive change, not just for AI and supercomputing and whatever comes next after that, but for society as a whole. But that's a much broader topic.

Christine Boynton: Anyone want to try a prediction on where we'll be with this in 10 years from any of the angles we've discussed?

Steve Trimble: Exactly where we are now? Think possibly with a few dozen Burevestniks pointed at us from Russia.

Guy Norris: And I think it all depends on China, to be honest. I bet you just as a, we predicted in 1958 quite falsely that the Soviets were about to fly their nuclear bomber, maybe the same thing will be happening. I don't know if we'll be reporting on it, but I certainly see if that happens that we may in fact, don't forget, as Steve mentioned, I think earlier on, there is this plan to put now a reactor on the surface of the moon to support lunar operations. So does that mean it's sort of something that's been acceptable and crossing the Rubicon maybe?

Steve Trimble: Maybe being the operative word?

Guy Norris: Yes.

Christine Boynton: Well, we're at the end of our hour and that is a wrap for this episode of Check 6 Revisits. A special thanks to our podcast producer Cory Hitt, and of course also to Guy and Steve. If you haven't already, be sure to follow Check 6 on Apple Podcasts, Spotify, or wherever you listen so you never miss an episode. And if you found today's discussion interesting, please consider leaving us a star rating or a review. Better yet, share the episode with a friend or colleague. Thank you for your time and have a good week.

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