Making The Case For Nuclear Aircraft

At any given moment, several of the US Navy’s Nimitz class aircraft carriers are sailing the world’s oceans. Weighing in at 90 thousand tons, these massive vessels need a lot of power to get moving. One would think this power requires a lot of fuel which would limit their range, but this is not the case. Their range is virtually unlimited, and they only need refueling every 25 years. What kind of technology allows for this? The answer is miniaturized nuclear power plants. Nimitz class carriers have two of them, and they are pretty much identical to the much larger power plants that make electricity. If we can make them small enough for ships, can we make them small enough for other things, like airplanes?

Nuclear Power 101

Nuclear reactors use the controlled splitting of uranium atoms to produce energy. This energy is transferred into water as heat. The water is kept under high pressure, which keeps it from turning into steam, and allows it to nuclear01become super heated. The super heated water is moved to a heat exchanger, where it heats another source of water to produce steam. This second heat exchanger not only allows for transfer of energy, but also isolates the radioactivity from the rest of the system. The non-radioactive steam from the second heat exchanger is then used to turn a turbine that produces electricity. The steam eventually heads to a condenser, where it turns back into liquid water and is moved to the second heat exchanger.

So now we know how nuclear power works, we get to work on the fun stuff! Our job is to discuss how we can make it really really small and cram it into an airplane. And then examine the consequences of such technology.

The Heat Transfer Reactor


Jet engines use spinning blades to compress air inside a combustion chamber. The compressed air is then sprayed with a fossil fuel and ignited with a spark. The resulting release of energy is expelled from the engine, producing thrust. A nuclear powered jet engine is pretty much the same minus the combustion chamber. Air is compressed and sent to a plenum. A nuclear reactor heats the air to a very high temperature. The super heated air is then sent to a turbine where it produces thrust.

The US government built a nuclear powered jet engine in the 1950s. It was called the Heat Transfer Reactor Experiment – 3, or HTRE-3 for short. It used liquid salt as opposed to water for the heat exchanger. The salt could get much hotter and was more efficient in the transfer of energy to the air.

The idea behind the nuclear powered jet is similar to the nuclear powered ship – no need to stop for gas. A nuclear powered jet would have an unlimited range. However, the advent of the ICBM made such an aircraft obsolete for military purposes.

What About Commercial Jets?

Nuclear Jet Engine

While it might not be practical to make a nuclear powered jet to drop bombs on people, what about for transporting people?  With today’s technology, is it possible to build a small, safe nuclear jet engine that could be used on a commercial airliner? It’s difficult to imagine that it would not be. Material science is much more advanced today than it was in the 1950s. We have the ability to perfect a smaller nuclear engine. The question is – why aren’t we?


The first thing that comes to mind is what happens if there is a catastrophic incident that causes the plane to break apart mid flight. How do you contain radioactive material during such a disaster? Let us rewind to the fall of 1997 when the Cassini spacecraft was getting ready to launch. At its heart was 37.2 kilograms of plutonium 238. You can imagine the controversy with strapping radioactive material atop a giant controlled nuclear04explosion.  NASA ensured that if the rocket exploded, the radioactive materiel would be contained. Cassini of course went on to be a very successful mission that unlocked many of Saturn’s secrets. We were able to mitigate the risks and dangers with Cassini. We should be able to do the same with a much more stable flight vehicle – a jet plane.

It’s Not Weapons Grade

The second thing that comes to mind is somebody stealing one and making a bomb. This is where we need to point out the difference between weapons grade and reactor grade uranium. You might have heard these terms used in the news recently, as they are key points to the Iran nuclear deal. Natural uranium is roughly 99% U238 and 1% U235. The U238 isotope will not work for nuclear power or bombs. You need a higher concentration of the U235 isotope. A much higher concentration of U235 is needed for a bomb, while a reactor requires a much lower concentration. The process of concentrating the U235 isotope is known as enriching.

Enriching uranium is difficult to do because the properties of the U235 and U238 isotopes are very similar. The most common technique separates the two by weight using high-tech centrifuges. This is the sticking point with the Iran deal. Nobody cares if they have reactor grade uranium. The deal is to prevent them from making centrifuges capable of separating enough U235 out of it to make a bomb.

So in short – you don’t have to worry about someone making a bomb out of the uranium from a nuclear powered jet engine.

Impact of Nuclear Powered Commercial Jets

Let us close with thinking about the impact of a safe nuclear powered jet on society. Moving away from fossil fuels is a popular movement. If we could convince everyone that it’s safe, it would have great support from many national leaders. Also, fuel cost is one of the airline industry’s greatest expenses. A plane that doesn’t require fuel would be a huge cost saver, allowing for cheaper plane tickets for all of us.

Now it’s your turn. Nuclear Powered Commercial Jet – Yes or No?

133 thoughts on “Making The Case For Nuclear Aircraft

  1. Enough with the nuclear every time something goes wrong the people suffer for generations and dead zone happen or outright pollution to the masses from minor mishaps. Enough with the wars! when you can hold a track record of no crashes and no planes shot down then lets talk

    1. “Enough with the nuclear every time something goes wrong the people suffer for generations and dead zone happen or outright pollution to the masses from minor mishaps.”
      Enough with the anti-nuclear fear mongering.

      Nuclear powered aircraft are a really bad idea.
      1. Shielding is heavy. It takes mass to shield a reactor and a lot of it.
      2. While the fuel in the reactor is not really dangerous it is the products of the reactor that are. That is why launching a reactor into space is not really dangerous. You do not run the reactor on the ground so it is all fuel. After it has been running for a while you have to be very careful.
      3. Take off and landing are the most dangerous parts of flight and tend to be near population centers.
      4. Cost.
      It is possible to have nuclear powered aircraft that are safe. Use a nuclear power reactor to crack water into hydrogen and oxygen and then use hydrogen and CO2 to make hydrocarbon fuel for the jet. Keep the reactor on the ground.

        1. The enrichment of the fuel is not in the weapons grade level. It is higher than civilian reactor levels but not in the 90% range. I spent multiple years on a sub operating one of those things.

      1. Yeah…so…this is really dumb…I used to be a reactor operator on a virginia class submarine. This had been tried before by the US Air Force and it is completely unsafe and hazardous to the air crew. This would be heavy as all hell due to the shielding weight and those multiple million dollar aircraft expenses would probably more near a billion dollars. The uranium-235 is heavily enriched and if one these things went down, just imagine the outcry from the unintelligible, on the topic, civilian side. Maybe in 20 years when materials catches up with the physics of shielding and the cost, will this be possible. Oh also you need to get the unintelligible on board with it.

        1. As far as shielding goes, far as I know (I’ll defer to your experience in actually operating a nuclear reactor) the only way of shielding is to put as much matter between you and the source as possible. So it’s always going to be heavy, heaviness is the factor you’re actually looking for.

          Now the world’s lucky enough to have ICBMs, there’s no sensible reason to make nuclear aircraft.

          1. Neutrons don’t need high density shielding, they need lots of hydrogen, so stuff like plastic and paraffin. Or water. And don’t need it on most directions. Alpha (helium nuclei) don’t go anywhere. Gamma (X-rays) are pretty easy. Beta (electrons) also pretty easy. From a reactor, none of these are very energetic compared to cosmic rays.

        1. yeah unfortunatelly the technology dosent exist (yet) look at all the talk about thorium reactors none of those projects actually took off so far… lots of theoretical stuff though so who knows maybe in a few years….

        2. I don’t think that will ever be the case in a fission or fusion reaction. You are going to have neutron radiation that is pretty penetrating. Even if you can shield from it, you’ll then have to deal with “activated” materials that absorb the neutrons.

          I think nuclear energy is still a great idea. Reactors moving around high in the atmosphere would be a worry, though.

      2. Fission reactors in planes are a bad idea, that’s why it was scrapped. Heavy shielding, heavy materials, and this little thing called “Decay Heat”. How do you cool the reactor when not in flight? AA reactor just big enough to power a plane will weigh about as much as the plane itself.

  2. Ok, so the fuel is ‘cheaper’ than Jet A and should make flights cost less… what about the cost of the aircraft? 100x the cost is kinda deterrent .

    While that’s fine and good that it doesn’t have enough U235 to make a bomb, the U238 will make a really ugly smoldering hole in the ground when one does come spiraling out of the sky. May not be a ‘bomb’ per se, but the scattered radioactivity will definitely give the crash site a bad day.

    While yes, the idea is great, the implementation and consequences are horrific.

    1. Actually the reactors in ships and subs do use weapons grade uranium but they still can not blow up like an atom bomb.
      It really isn’t the U235 or U238 that you have to worry about. You can sit next to a block of it decades without issue. Just avoid eating or breathing it and you will be fine. The issue are the waste products of the reactor.

  3. Moving out of fossil fuel is indeed a good thing, as we harm Earth using it. But nuclear harms Earth too. Not now (unless there’s an accident happening, in which case you have Tchernobyl or Fukushima), but later on, when you have to dispose the used Uranium cells. That radioactive stuff lasts for thousands of years. It seems cleaner, it seems more efficient, but if reactors are under volumes of water AND concrete, there’s a reason for it. And it’s not weapons grade uranium, but reactor grade.
    I wouldn’t feel safe at all in the plane, knowing there’s what, about 50cm of protection between the reactor and the rest of the plane. I wouldn’t feel safe at all in my house knowing how many planes fly over many human or animal heads, thinking that if the reactor core overheats, then there’s a mini-Tchernobyl happening high up in the sky, resulting in a wider radioactive distribution over Earth.
    Nuclear power is a true technology advance, but let’s keep it locked under concrete and water until we find a cleaner alternative, and let’s avoid thinking of threats only with bombs or terrorists. With nuclear power, human error is a threat. Engineering is a threat too. Heck, even a bird or a lightning up in the sky can be a threat for nuclear-powered planes :)

      1. No, they are not. If you simply consider Uranium we have a 100 year supply that we know about, and you can extract it from seawater. Consider Thorium as well (which would lead to safer reactors and less dangerous byproducts) and the known reserves go up beyond 1000 years. The cost is also a trivial part is f the running cost of a reactor.

        1. Is the 100 year supply based on current use, or potential future use displacing all other fossil fuels?
          I expect the seawater option is fairly low-yielding; otherwise only land-locked countries would be importing uranium, and restricting exports would be pointless.

          1. There’s such an oversupply of uranium and thorium that companies are refusing to prospect more in fears of stock prices dropping. Nobody’s seriously considering extracting uranium out of seawater because the prices are so low it wouldn’t make ends meet.

            Furthermore, we’re using the uranium very inefficiently because governments have basically banned the reprocessing and recycling of nuclear fuel – only couple places do it – and most reactor fuel is put through once with only 3-4% burnup. 95% of fissile uranium is basically just thrown away.

            The thing is that uranium and thorium are byproducts of rare-earth metals production because things like neodymium and indium that are used in the manufacture of wind turbines are solar panels are end products of nuclear decay chains – they’re found in rocks containing radioactive elements. As a result, there are literal mountains of the stuff dug up and just laying around and leeching heavy metals and radioactive nuclides into rivers and lakes, and nobody has any idea what to do with them.

            People who are hysterical about nuclear power totally disregard that the renewables they like so much produce more nuclear waste than nuclear power itself.

    1. You should take a look into fast-breeder reactors. They use NUCLEAR WASTE from old reactors as FUEL, to produce energy at the same time as reducing it into less waste with much shorter half-life. Some liquid-salt cooled designs can even operate under convection, so even if cooling pumps fail it coools itself off and comes to a controlled stop on it’s own.

    1. Even if Cassini did explode on the ground the RTG reactors are tough suckers. They were built to be able to withstand such an event. The energy they produce is much lower than the what would be needed to power a plane though. On order of hundreds of watts of electricity…not the high heat thermal loads required to propel a plane.

      1. There was one incident of a launch failure with an RTG on a satellite. The RTG was recovered from the Atlantic, repaired and refitted then installed in the replacement for the lost satellite.

        RTGs are built like the casks used to transport radioactive materials like old reactor containment vessels and spent fuel. It would pretty much take close range exposure to a nuclear bomb to break them, and if that happens the contents of the cask or RTG are nothing to worry about.

        Old Soviet RTGs have contributed to some deaths when people stole them from lighthouses and peeled off the shielding to use them instead of campfires to keep warm. But those weren’t made to be launched into space.

        1. RTGs are easy to heavily shield because the ones you are describing have very low power output compared to the amount you would need to power an aircraft. You would need to increase the output at least two orders of magnitude which means much, much more weight to have the same level of shielding.

    2. “Many, many other examples that didn’t go that well”?
      I hadn’t heard of any – can you elaborate?
      I’m pretty sure Apollo 13’s RTG survived re-entry and landed in the ocean without any leakage. They’re tough.

  4. “If we could convince everyone that it’s safe,[…]”
    Great idea. If humaninty can’t get rid of the rest-risk while standing on ground, what makes you think we could when we put it into the air? Plus, why is it that everyone thinks that Plutonium is cheaper than fuel? Look at the supply chains! In fact, if you calculate all costs together, including storage for a couple of thousands or millions of years, it is the most expensive, risky an stupid thing that anyone could ever imaging.

    1. In reality it costs comparatively nothing to store nuclear waste, because you drill a hole 5 miles deep, drop it in, and fill the hole. That’s called deep borehole disposal.

      The next time it has a chance to come up, ice-ages have come and gone and the North American continent has collided with China.

      1. Point being that you don’t actually have to contain nuclear waste for millions of years because the radioactivity decays down to naturally occurring levels in a few thousand years. If you worry about what comes up a million years from now, boy, you should be scared shitless for what comes up the volcanoes today!

  5. No!

    Nuclear energy needs to be explored to its fullest potential on platforms that are much less prone to things like GRAVITY. The weight trade-off for shielding and associated safety systems makes the use of a small power plant on a plane much more expensive pound for pound than petrochemical propulsion.

    Perfect Thorium-cycle, Molten Salt and Gen IV and later reactor designs, get our main power generation over to a non carbon polluting source (in a method that produces only low grade, low half-life waste) and allow carbon emitting technologies to continue where they continue to make sense. Over the decades I think we can perfect energy storage technologies to all but remove petroleum based chemistry from the things we use….but until then, we will continue to use them.

    Battery powered planes? Some undiscovered power source? Maybe……Nuclear? Not until you can make the reactors super light and super safe!

  6. > NASA ensured that if the rocket exploded, the radioactive materiel would be contained. Cassini of course went on to be a very successful mission that unlocked many of Saturn’s secrets.

    Something good happened, therefore nothing bad could have happened.

    Some quality logic right there.

  7. This is stuff that’s been rehashed for decades and discontinued for obvious safety reasons as other comments have noted.

    The real advances towards an “aircraft powerplant” (something that will produce a lot of power, be light and be safe) will be in things like shielding materials and other “smaller” developments. The thought of a nuclear powered drone that flies for years without refueling is both intriguing and terrifying…

    1. The thought of such a drone is particularly disturbing, as it would likely elicit the kind of thought and feelings that would convince certain types of individuals that it must be brought down..

        1. There’s a difference between power and energy. Power is the rate of energy production/consumption. Energy is power integrated over time. To say that power “is released over very long periods” doesn’t make sense. Energy can be released over very long time periods, but power is, by definition, the speed of energy release.

          RTGs are very heavy compared to the power they can produce. They are, however, relatively lightweight for the amount of energy they produce during their lifetime.

  8. Battery-electric plane, keep the Uranium on the ground where you can at least place guards around it. Centrifuges aren’t a complicated thing to build. The last thing we need is more nations with nukes, especially unstable ones. Besides being a penis-extender for idiot demagogues, they’re also capable of wiping out cities and ending the world if you have enough of them. This isn’t the 1950s. We should be extremely cautious when it comes to looking after nuclear material.

  9. We should concentrate on harvesting as much energy as possible from the sun (light, bio mass, wind, waves) and on improving energy storage devices.

    The next fairytale the industry will tell us: Fusion is a clean energy.

    It is not!

    Fusion emits hard radiation and that pollutes the reactor chamber which will turn into radioactive waste needing to be replaced periodically.

    Probably nuclear fission and fusion are only one thing: A big opportunity for some few getting ridiculously rich on the behalf of other’s health.

    1. Solar, wind, wave and bio-mass electricity generation is also harmful to the environment, why the fuck would you even think it’s not?
      The sheer size of such power plants that would be required to satisfy all the demand would on their own would be a environmental disaster. Then there’s also the crapton of distribution networks needed to keep this hippie wet dream sustainable, since you can’t just shut down all the factories in the region because it’s a calm, cloudy day…
      Just try to imagine how huge a several gigawatt solar farm be. Same for any “alternative” powersource. And then imagine the massive distribution network that would allow stable supply of power without fossil or nuclear power.
      Massive windfarms would make some birds species extinct in the region.

      Bio-mass as a major source of power is total bullshit, just look at how long it takes to grow the plants and how much energy you can realistically get, you’d be (quite literally) orders of magnitude better off if you build a photovoltaic powerplant and keep the plants for food.

      1. Yeah, I did some back-of-the-envelope math and the USA would have to turn over most of its agriculture production to fuel crops if we were to make the total change to bio-fuel. It was a crushing blow I dealt to my hippie friend, but it was necessary. And terribly funny. Maybe people should work on consuming LESS energy rather than producing more.

    2. well fusion could be clean if they can get aneutronic fusion and direct conversion to work. however I’m kind of pessimistic i will see fusion work at all in my lifetime….(they have been at is since like what 75 years without any results at all?? don’t think that’s gonna change soon)

    3. Altamont Pass, CA wind turbines shut down due to bird deaths. Real reason is probably the cost of maintaining such old turbines but whatever. Environmentalists fought for years on this one.

      Ivanpah, California. The solar towers there are known to burn birds alive as they fly through the “zone”. Blind airplane pilots flying overhead. It also blinds golfers on their game but I don’t care much for them. The company is breaking ground for a new, larger, facility.

      Just two examples.

      These companies don’t give a rats ass about safety or the environment. They follow the money. Did you really think “Carbon Credits” did any good or was it just a complicated scheme to line the pockets of the few rich?

      1. Altamont Pass started replacing their old turbines with new ones at a rate of about 40 old to 1 new because the old turbines were crap. Problem is, the pass produces electricity exactly when there’s no demand for it, because the winds pickup towards the late night and die off for the day and early evening, so it’s nothing but trouble for PG&E. The only reason it exists is because of federal and state tax credits that net the company more money than the cost of the damn thing.

        Ivanpah California is also producing 1/3 the electricity it promised because is just hasn’t been sunny enough. Solar thermal facilities have significant thermal inertia – they don’t turn on and off instantly – so having clouds pass in front of the sun every few minutes reduces the temperature of the collector and the efficiency of the turbines drop. That means it extracts less energy out of the sunshine between the clouds as compared to having a continuous view of the sun, and the estimates sold to the public based on the expected number of hours of sunlight it recieves were simply bullshit.

        But, the whole thing was basically paid off by subsidies and tax credits before a single watt of electricity was put into the grid, so the operators don’t actually care if it produces enough energy to justify the cost. They’re already making profit.

  10. Ok so the reactor grade uranium is presented like a soft uranium without danger in this article. But Tchernobyl? does it ring a bell? It was no weapons grade uranium but when it exploded it didn’t spread candy bar around…
    So if every year 2 to 5 planes crash, it’s 2 to 5 nuclear contamination per year, and yeah Tchernobyl is still deserted 29 years after the catastrophe! Thanks but no thanks.

    1. Tchernobyl did not have any containment, because the Soviets found it too expensive. Note that none of the other plants that were built the same way ever suffered the same problem. The irony of Tchernobyl disaster is that on that night, they were performing a safety test :P
      Fukushima was fine after a very strong earthquake, it took a nearly 15m tsunami wave to destroy the backup generators and paritially damage the distribution grid. Had the plant (somehow) had power, it would safely cool off.
      Also note that the Fukushima Daichi reactor was one of the oldest running in the world. Newer ones are much safer.

      All and all, it takes very extreme measures to make a reactor fail catastrophically, if you count the number of deaths, injuries and forced relocations, nuclear power is still one of the least harmful :P

      1. Chernobyl is the only commercial electricity producing reactor that has suffered a catastrophic failure. Far as I can find, it’s only the second nuclear reactor that has had a core explosion due to accident. The other one was the SL1 test and research reactor at INEL in Idaho, where the reactors for the Nautilus submarine and the Nimitz aircraft carrier were developed.

        SL1 exploded due to a design flaw where the control rods could be pulled completely out of the core, they weren’t large enough relative to the mass of fuel and the main rod alone when pulled would allow the reaction to start. To fix the size problem, strips of boron were attached to the sides of the rods to absorb enough neutrons to damp the reaction. The high temperature water caused the boron to swell and flake, causing the rods to get stuck in the core.

        On the day of the incident, maintenance work was being done on the control rod motors. After removal and servicing, it was time to reinstall them. The rods had slipped down and needed to be lifted to reconnect to the motor gearboxes. From the aftermath it was surmised that the main rod had stuck and one of the three men stood on top of the containment vessel, took hold of the main rod shaft and yanked up. The rod snapped free, popping completely out of the core inside the vessel. He likely had enough time to think the first letter of “Oh shit!” before the core went to a runaway condition and flashed all the water to steam which blew the top of the vessel and him into the ceiling. A worldwide search found only one other similar reactor (IIRC in Iceland) with a control rod design where pulling one rod could have the same result. A safety stop was installed to the main rod could not be pulled all the ay out of the core.

        Why do they call them Nimitz Class carriers when the Nimitz is a significantly different design from all the others? The Nimitz had eight reactors, pretty much copies of the two small ones used in the Nautilus submarine. All subsequent USN CVNs have used two larger reactors.

        1. You’re thinking of the recently decommissioned USS Enterprise (CVN-65), which had 8 x A2W reactors. The Nimitz (CVN-68) has 2 x A4W reactors, as do the other Nimitz-class carriers.

    2. “Tchernobyl is still deserted 29 years after the catastrophe! Thanks but no thanks.”

      The half-lives of the most problematic isotopes like Caesium released at Chernobyl happen to be around 29 years, so right now is about the time when most of the affected area has dropped down to harmless levels. Another 30 years and practically all of the place would be safe for people. The only problem would be eating local animals and mushrooms, because heavy metals become concentrated in them. Growing grain and vegetables in cleared fields should be no problem.

      You could live there – there’s just nothing in there for anyone anymore.

  11. > Nuclear Powered Commercial Jet – Yes or No?

    Not yet.

    Watching a world falling apart,

    – where most so-called developed nations aren’t capable or willing to mitigate the most pressing problems of humans
    – where shareholder value tops just anything
    – where the decisions of “democratic” nations are dictated by bigcorps, and those by their beancounters

    I’d wish a more mature humankind before we have big clumps of semi-enriched uranium (and all the nasty stuff which develops in there while being run) zipping over our heads.

    Nimitz all well, but remember: those haven’t the cost pressure an airline has. Problems in e.g. France’s nuclear reactors started developing once they left the “military strategic” cosy zone and entered the harsh cost-cutting environment of “business as usual”.

    Thanks, but as long as above problems persist, I’ll stay a staunch anti-nuclear. And yes, I’m a physicist.

  12. The answer to the shielding problem is simple. Use electromagnetic shielding. There’s plenty of power from the engine itself. Turn the thing into a homopoler generator and put some coils around the reactor.

      1. Yeah but using a solid is infinitely easier, and better. You’ll never get the density of a solid by compressing gas, or plasma. Plasma is ions flying all over the place, a solid is squillions of atoms just sat there, nice and tight.

    1. Would be like a dirty bomb. If there’s no fuel on board that is combustible the towers may never have fell. Nuclear cleanup, sure…but I don’t know that the same number of people would have suffered.

      1. Before any conspiracy nuts chime in… The steel didn’t have to *melt* for the buildings to fall. It only had to *weaken*. Ordinary construction steel loses a large part of its strength at around 1,500F. There wasn’t just the jet fuel burning, there was all the other things like office furniture, dividing walls, plastic housings for office equipment like printers, FAX machines, monitors and parts of computer cases.

        But the nutcases want to believe that metal works like ice, that it retains full strength right up to the melting temperature then changes from solid to liquid phase.

        1. I’ll point out that building codes have long required that steel-framed buildings have insulation sprayed onto the framework that’s more than sufficient to insulate the framework against a fire of the normal contents of the building. But the building codes don’t require sufficient insulation to maintain structural integrity while a large load of jet fuel is dumped on the building to create an accelerated fire. Who knows, but maybe without all that jet fuel, the buildings would have suffered less damage, even with a nuclear powered plane. Not that I believe a nuclear powered plane would ever be practical, though.

          Incidentally, the fact that building codes require the framework to be insulated against fire is also a point many conspiracy nuts ignore. If fire can’t weaken a building’s structure, why would the building codes require fire insulation for the structural beams? And if this particular building fire had more added fuel than any previous one, more than the building codes required the insulation to withstand, might that explain why the damage was more severe?

          1. From some of the reports I’ve read, the insulation was deficient in some areas due to some factors like cost cutting, accidental dislodging of material or just plain human error. Also the design of how the floors were attached introduced weaknesses that wouldn’t have been able to withstand a plane hit. The two hit buildings probably would have come down anyway.

            Most office equipment cases are made from Brominated flame retardant plastics which should have just charred with a non jet fuel enhanced fire.

            That other building that just dropped neatly within a few hours though was a bit suss

    2. I wonder if the building down the road would have still been blown up. If the self destruct hadn’t been set off, the secret service would probably still be operating from that floor.

  13. It would be simpler to use a nuclear reactor to produce more portable fuel for the plane. I don’t know how it works, but Navy has done proof of concept on extracting jet fuel from seawater. Even hydrogen fueled aircraft would have more manageable technical hurdles.

  14. I think there are 2 key engineering issues (I’m not an engineer – this is just what I’ve observed) that need solving before we look at economics and finally consumer acceptance:

    1) Power / weight ratio. Yeah nuclear fuel has lots of energy, but the weight to manage it cannot be trivial. Might as well suggest a coal powered steam engine for your airplane. RTGs in space? The power/weight ratio is still brutal, but the 20+ years of continuous power is very appealing. Also note that RTGs produce hundreds of Watts, not millions.

    2) Heat management. Nuclear power plants take a while to ramp up / down. An airplane on the ground or cruising/landing uses much less power than during take off. How do you deal with all that extra heat when not running at full thrust? Might work for a (semi-)permanently flying reconnaissance, I mean communication drone.

    1. You forgot one: pilot shielding.

      The original plans for ‘nuclear’ aircraft were ultimately abandoned simply because the dosage to the pilot was too high, and there was no feasible way to shield the pilot/crew sufficiently without too much weight to get off the ground.

      There was an old testing ground in northern Pennsylvania where these experimental engines were tested in the 50’s. Used to be a bunker, several ‘blowout’ ponds, and an in-ground reservoir presumably for cooling water. A few years ago, the government came in and covered everything in mounds of dirt.

  15. Runtime : What about safe starting / stopping of a reactor ?
    Shielding : If the entire radiation (primary and secondary) could be limited to Alpha particles, no heavy shielding would be necessary. Even Beta (electrons) are easily shielded with light materials (organic glass for example), or perhaps some electric/magnetic fields.

    1. that would be nice, but that just isn’t how fission works. about 5% of the power from a fissioning Uranium 235 atom is high energy Gamma radiation.nothing can change that. so you will have to use a different fuel/process to get rid of that type of radiation. 2.5% of the total energy is beta radiatiion, and that can be stopped by a piece fo paper.

    1. HOLY COW! I had no idea that this was even considered. Given the context of the time I can see why this would be appealing but honestly a nuclear powered missile with nuclear warheads, that then uses its supersonic shock-wave to do ongoing destruction then finally crash and containment! I am truly at a loss for words.

  16. My Nuclear Engineering degree will be Useful today!

    The short answer is no, not without a different process other than fission of Uranium.

    The Reason you see nuclear aircraft carriers, but no nuclear passenger liners is the economics of that 25 year lifetime of the reactor cores.

    First, that reactor core has tons of fuel in each core. That fuel is 90% enriched, which makes it really, really expensive. It took over 100 tons of uranium ore to create the fuel in each reactor.

    Why, you may ask, does the navy waste so much money to use this higher grade of fuel? The answer is control. You control a reactor by inserting or removing control rods. This is common sense, but what isn’t as widely known is that the lower your fuel grade, the more involved it is to throttle your core. If a carrier did not use this high grade fuel, it would be unable to provide the power to go full throttle without hours of a run- up period. (And that is being generous, most nuclear power plants takes week to change the rods position)

    Also, the navy doesn’t expect their ship to be running full time. The general cycle is 1 deployment (6-9 months) 1 shipyard period (6-9 months) and a period of time in port, doing one week a month out to sea to provide training to pilots learning to fly, and other training missions off the cost of the US. (6-9 months) and every 3 cycles or so, and extended shipyard period is expected. This means that the ship’s core is shutdown at least 1/2 the time of its life, if not 2/3.

    So that 25 years is now 12.5 years of actual use, best case scenario.

    Also, there is the shielding issue. The two most effective shielding materials for gamma radiation are iron, and water. Steel is about half as good as iron. I never remember hearing the effectiveness of titanium, but I do not think it’s very good. Iron actually is very effective right along the most common wavelength that Uranium fission usually emits, so its works well on many levels.
    So your shielding is going to be heavy, and unless accept you have special air strips for radioactive planes with shielded terminals, but then what happens if a crash occurs?

    Lastly, there is the Cooling problem. I’ve seen some mention of the Air Forces attempt at a nuclear powered airplane above, but the issue is cooling. You would have to use air cooling, and unless you want to strap on huge radiators, you are air cooling the core itself. This poses some interesting problems, mostly in the speed of controls, and allowing the computer to control the rod position very quickly. This is great if everything is working, but as the air force found out, one sensor failure can cause the reactor to become slag.

    The answer to why we don’t have nuclear air planes is the same as for nuclear cars. As long as nuclear power plants use Uranium fission as their fuel and process, they really can’t me miniaturized any further. Than they are to power quarter mile long ships or huge power plant installations.

    1. You might have a point, assuming they make an actual leap in battery technology, which would require one of the 100+ ‘breakthrough’ discoveries to be finally become usable.
      But it would be limited to slow planes though since you can make props electric but AFAIK not jet engines.
      But now that you mention it, perhaps something is possible there, some way to design an ‘air-jet’ kind of deal? I mean we now are quite a bit on in technology and I’m not sure anybody tried to research such a thing seeing what we have seems to work OK. And as I recall some guy, a brit I think, made a breakthrough discovery on jet engines a few years back related to getting air into it, which is an example of new addition to the arsenal of knowledge that might be useful.

      1. Air transport planes use high-bypass turbofan engines. The thrust primarily comes from the fan, not the jet. The jet is used to turn a turbine, which spins the fan. This may seem roundabout, but it is much more efficient that using the jet’s thrust directly. The fan moves a greater mass of air at a lower velocity than the jet would.

        The fan could be powered by something other than a jet’s turbine. At least in theory, if you had a plentiful, lightweight supply of electrical energy, you could use electricity to power a ducted fan, and get something similar to a turbofan engine’s efficiency and speed. The problem, of course, is that the energy density of any battery technology is far worse than the energy density of jet fuel.

    1. Yeah, elementary particles stick to their guns – and properties.
      But since they are doing away with pilots (in planes) and it’s all remotely controlled or autonomous drones.. we might have lower requirements for shielding, even if electronics needs shielding it will fit in a smaller box than a human after all.

      But there its still the insane risk to health, and sure you can argue it’s not weapons grade and not too bad, but 1 death in 100K people is still someone’s mom, or it might be you; the reader.
      And look at the reports about those soldiers fighting in iraq and their exposure to the depleted uranium ammo.. it’s a shitty and sad thing to be fucked by such ‘harmless’ things.

      Plus the output of a nuclear reactor is either low when using a turbine in a plane-sized reactor (and it would have a gyroscope effect too come to think of it) or iit uses the space-probe type direct decay system, which is a bit pricey and risky but would still only get you electricity and as I said in the other comment, you’d be limited to propeller engines. So it’s still a silly idea.

      They did however once propose a rocket engine for spacecraft that consisted of many consecutive nuclear explosions for propulsion.
      And funnily enough I saw a article about how Elon Musk also proposed a constant stream of nuclear explosions above the Mars pole to terra-form Mars. So the wacky ideas around nukes are hard to eradicate. (I still don’t see how Musk imagines you’d get a million nukes to mars, and who would pay to build them and where you’d get the weapons grade nuclear material for so many.)

  17. Others have made many valid points, but I’ll just comment on the closing paragraph:

    “Also, fuel cost is one of the airline industry’s greatest expenses. A plane that doesn’t require fuel would be a huge cost saver, allowing for cheaper plane tickets for all of us.”

    I’ll believe that after nuclear power plants become huge cost savers that cut the cost of electricity enormously. Nuclear power plants, like nuclear aircraft, don’t use fossil fuels. Nuclear power plants don’t have nearly such stringent constraints as aircraft would — weight in particular is much less of a concern for a power plant at a fixed location. Nuclear power plants were supposed to cut the cost of electricity so much that it would be “too cheap to meter”. We all know how that has worked out…

    I don’t intend to debate the reasons why nuclear electric power generation hasn’t lived up to the hype from decades ago, but I’ll just point out that nuclear airplanes would probably face at least as many cost-increasing problems, if not more.

    If it IS possible to make nuclear really cheap, it will probably be possible to do so on ground-based electricity generating facilities before it will be possible to do so on airliners. If the problem of generating electric power cheaply is ever solved, you could use the cheap electricity to synthesize jet fuel from water and carbon dioxide, and thus give us cheap airfares, while avoiding the use of fossil fuel.

  18. I get as sick as anyone of the comments on HaD whingeing about general-technology-not-a-hack articles, but seriously this is jumping the shark. This article is such ill-researched, click-baity ignorant bullshit it’s not funny.

  19. “If you are willing to deploy nukes on the battlefield, you might as well drop them from orbit” seems to apply here. This article isn’t even click-bait. It’s “Texas Home-Schooled Click Bait” – Yes, Texas is debating to make home schooled kids actually learn something at “school.”

  20. Does anyone else remember this article? Popular Mechanics May 2004. I haven’t seen anything on Hafnium reactors since.


  21. In the 80’s Teledyne did a design study for nuclear-powered tank using Helium as the moderator and the fluid for the gas turbine. Conclusion: could be done, would be practical from a combat standpoint, but WAY too expensive … stick with big diesels and gas turbines

  22. This was a painfully ill-considered article. Nuclear shielding is, without exception, very massive/heavy- doesn’t work with a plane. Planes, commercial and military, still crash all the time, and having a nuclear reactor on board could make that a huge disaster. But the worst is that you actually suggest that a plane running on nuclear fuel is an economic alternative to standard jet fuel- even calling such a plane one that runs “without fuel” (second to last paragraph). Nuclear fuel is insanely expensive:, and yes, you need nuclear fuel for a nuclear reactor.

  23. Gah… Okay… While the Nuclear Engine concept is a great idea, people need to understand that one of the reasons this project failed was because there is NO SUCH THING AS A HEAT ENGINE! Heating air does virtually nothing in terms of thrust produced. Just look at a sterling engine, a flame heats the air, the hot air rises, and causes the little piston to go up. The problem here is that a typical jet engine does NOT operate using HEAT, it operates because of combustion. Combustion (while it produces heat as a bi-product) releases stored energy, like letting go of the end of a filled balloon, it produces thrust because of expanding gases, or gases under pressure. The ONLY reason a jet engine needs an air intake is so it can mix the fuel with the air and ignite it in a combustion chamber and then the expanding gasses push on the blades of the turbine. Now lets imagine there was no such thing a heat, or temperature. Lets imagine it’s all the same temp. The same jet engine would still operate because it’s the force of the expanding gases pushing on the turbine blades, not waste heat. In fact, any heat produced can be seen as “waste heat” as it really does not do much. Even your car engine could run without any heat as an IC engine is also driven by expanding gases(please STOP calling it a heat engine people!). Back on point, this Nuclear Engine thing did not work because the thrust produced was so low as there was no expanding gases, but just heated air alone which trapped in a closed space, heated air will cause “some” thrust. The ONLY way a Nuclear engine would work is if it was an electric ducted fan engine driven by generator, that is in turn driven by a nuclear reactor. There is no need, or reason to introduce the heat from a reactor into a jet engine.

  24. Fission? no chance really… too much shielding required, and too much anti-nuke sentiment in the USA still (last I heared you still bury all your waste with no reprocessing! that is just mad…)

    Fusion? possibly. lets just wait and see what the Skunkworks brings us with compact fusion..
    If they succeed I can see many things turning to fusion power… anywhere a gas turbine is used to generate power, these will take over I expect! (or I certainly hope)

  25. I am neither for nor against the idea (it has good possibility), however I would like to point out one thing (and this idea is not a direct contributor, but would be an aid): If this idea were in full use September 1, 2001, not only would we have had burning and collapsing buildings (that also had asbestos), but we would have had *a dirty bomb* effect. Vaporized nuclear material, asbestos, fire, collapsing buildings… it would be another concern to a bad situation, and one that would not be quite as easy to address–even though the health issues are reasonably low in the situation, the panic alone would have compounded the situation.

  26. So what hapens in a crash? Those old Navy reactors are horrific dangers for thousands of years. If they can ever make nuclear where there is no down side then I’m all for it. Until then it’s messing with death.

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