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General Electric HTRE-3 Nuclear Jet Engine
- JKCalhoun 2y agoSuch a wild concept from a wild time in history. I have wanted upon occasion to put together a YouTube channel where I drop in on nerdy road trip destinations to try and get others to roll out and check these places out as well. I think in fact it was my stumbling upon the Experimental Breeder Reactor 1 [1] where I first hatched the idea. Such an amazing place and with those crazy nuclear jet engines just sitting outside.... So sublime: a picnic lunch with the wife and kids at a table by the experimental nuclear engines.... [1] https://en.wikipedia.org/wiki/Experimental_Breeder_Reactor_I https://en.wikipedia.org/wiki/Experimental_Breeder_Reactor_I
- sneak 2y agoI wonder if a RTG could produce enough to run an electric quad or optocopter? For certain applications if unmanned you wouldn’t really need to worry about shielding. I wonder how long those motors can run continuously?
- alejohausner 2y agoThe RTGs on the Voyager spacecraft weigh 38kg. They initially produced 160 Watts. That sounds like a no-go to me.
- FredPret 2y agoIt might not have great power density but boy does that thing keep going for decades
- jaggederest 2y agoFull power for ~10,000 years, give or take.
- fragmede 2y agoNo. You're thinking of nuclear waste. Voyager's RTG lasted "only" a few decades.
- jaggederest 2y agoDesign choice, not an inherent constraint. Plutonium has a half life in excess of 25000 years
- chickenbig 2y ago> Design choice Presumably this is why Pu-238 is used for RTGs where power density matters; a half life of 87.7 years means a reasonably long working life using with only 1/3% of the mass compared to Pu-239.
- jaggederest 2y agoOh yeah you're probably right, I didn't think about it being a different isotope. I figured they just kept it near-critical to keep it toasty instead of a shorter half life.
- mlindner 2y agoLong half life also means low energy output.
- Gibbon1 2y agoI think you need 1 hp per 10-15 lbs of weight to fly. I think that's around 130 W/kg. I checked a piper cub is something like 100. Other hand Pu-238 produces 570 W/kg. A piper cub with it's 48kw engine would need 87kg of Pu-238 to produce the same energy. I looked up the cost, $1968/g. So 48kw would cost $171 million. Interesting idea but doubt.
- Gibbon1 2y agoForgot the efficiency of an RTG is at most 10%. So you'd need 870kg of Pu-238. Which is twice what a Piper Cub weighs.
- brnt 2y agoI wish Toshiba would have actually sold that RTG laptop battery. Imagine never having to charge!
- hypercube33 2y agoNot just Voyager but the mars robots as well.
- beefman 2y agoDragonfly is NASA's RTG-powered octocopter. It launches for Titan in 2028 https://dragonfly.jhuapl.edu/ https://dragonfly.jhuapl.edu/ https://en.wikipedia.org/wiki/Dragonfly_(Titan_space_probe) https://en.wikipedia.org/wiki/Dragonfly_(Titan_space_probe)
- doctor_eval 2y agoI got nerd sniped by this and asked GPT some questions. Given a 45kg RTG plus the weight of the drone itself, you’d need to be able to lift, say, 60kg. Energy required to hover 60kg using a 4-rotor drone at 70% efficiency is about 10kW - according to GPT. I don’t know enough to say if this is true or not. Assuming it’s correct, and that a 45kg RTG generates about 300 watts, give or take, the answer is: no.
- namibj 2y agoThere is no technical minimum; the only thing to keep in mind is that lift/drag ratio relates potential energy (moving mass up against gravity) to travel distance. This applies independent of speed and vehicle type (even running counts!).
- mr_toad 2y agoNuclear Stirling engines can run for a decade or more, but are still too heavy for a helicopter.
- riffic 2y agoDid they just expect these aircraft to never crash?
- SoftTalker 2y agoNo, that was one of the practical problems with the concept.
- kristopolous 2y agoAs far as I can tell, aircraft and space nuclear propulsion still hasn't actually be used in flight, right?
- colechristensen 2y agoCorrect depending on if you count spacecraft with electric propulsion powered by radioisotope generators.
- topspin 2y agoReactors have been flown and made critical in flight, but never used to provide power for aircraft propulsion. The Soviets got the closest, but they abandoned it as well. Recently Putin has revived a nuclear powered cruise missile design. Status is unknown publicly, but it is believed to have been set back by a major test failure and contamination event. Today, one can imagine solving the crew shielding problem of these large, nuclear powered bomber concepts by simply eliminating the crew and foregoing most of the requisite shielding. Had that been possible at the time these concepts might have been deployed.
- acidburnNSA 2y agoCorrect. Snap-10A was a nuclear fission powered satellite. It was not propulsion.
- kolinko 2y agoNot in flight, but Nerva had multiple prototypes built and tested - the longest run being over an hour long. It was cancelled due to politics, not technical viability. https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA
- jaggederest 2y agoHere's another fun one: https://en.wikipedia.org/wiki/Supersonic_Low_Altitude_Missile https://en.wikipedia.org/wiki/Supersonic_Low_Altitude_Missil... An unmanned nuclear-powered ramjet designed to spew warheads, with a predicted range of 116,000 kilometers.
- colechristensen 2y agoAnd for scale that’s circling the earth three times.
- viraptor 2y agoWell, that's the best setup for the roadrunner ACME missile launcher joke I've ever heard.
- jesperwe 2y ago...at ground level.
- japanuspus 2y agoThe correction for cruising height would be insignificant. A ram-jet is an air-breathing engine and would be confined to the atmosphere. Even a 60km cruising height (which is much higher than what would be used) would only correspond to a 1% increase in flight path circumference compared to the surface value of 40.000km.
- ballooney 2y agoI think the GP might have meant that Mach 3 at ground level is even more technically astonishing - a lot of the historial benchmarks for airspeed (mach 2 fighters and interceptors, the SR71's mach 3) were only valid at very high altitudes were the atmosphere is sufficiently thin to make the achivement teneable from a drag and heat-flux perspective. To cruise along at Mach 3 at sea level is a quite astonishing display of brute force.
- worstspotgain 2y agoI see your GE HTRE-3 and raise you a https://en.wikipedia.org/wiki/Ford_Nucleon https://en.wikipedia.org/wiki/Ford_Nucleon
- acidburnNSA 2y agoThis was never serious. Technical writing e.g. in textbooks in the 1950s explain that a nuclear-power car is 'not within the bounds of reality'. https://babel.hathitrust.org/cgi/pt?id=mdp.39015003994194&view=1up&seq=19 https://babel.hathitrust.org/cgi/pt?id=mdp.39015003994194&vi...
- creshal 2y agoToday, we have nuclear powered cars on Mars. And with their amazingly powerful (checks notes) 0.13hp engine, you'll have plenty of time to admire the view.
- worstspotgain 2y agoHey, don't knock it, the West was won on 1hp.
- stragies 2y agoToday?, Curiosity landed 2012 in the Gale Crater on Mars: https://en.wikipedia.org/wiki/Multi-mission_radioisotope_thermoelectric_generator https://en.wikipedia.org/wiki/Multi-mission_radioisotope_the...
- boxed 2y agoWith no humans close to them.
- worstspotgain 2y agoHmm, I don't know, it's a concept car, not a sci-fi car. Show me a big shot realist and I'll show you an even bigger dreamer.
- torrefatto 2y agoI guess the author gets paid by word count. The piece could have been written in one third of the length.
- Toutouxc 2y agoI see you’re getting downvoted, but that was my first, second and third thought when reading the article. It’s suspiciously hand-wavy about the technical details, things are repeated several times and it really does feel like the writer was trying to stretch the article with the help of a LLM.
- AlphaGeekZulu 2y agoThe piece was definitely written by an AI. And a bad one at that. It is a redundancy nightmare. To save your time: "In 1951, the United States military initiated a program aimed at developing a nuclear-powered aircraft capable of unlimited range (ANP program). The program’s goal was to create a nuclear reactor small enough to fit into an aircraft yet powerful enough to provide the necessary thrust while ensuring the safety of the crew from radiation. General Electric (GE) initiated the HTRE (Heat Transfer Reactor Experiment) series to create and refine the technology necessary for integrating a nuclear reactor with a jet engine. The reactor in the HTRE-1 was essentially a modified version of existing nuclear technology adapted for aviation use. The HTRE-2 tested different configurations and setups to optimize the efficiency of the nuclear jet engine concept. The HTRE-3 featured a more compact and efficient reactor design that was closer to what would be needed for actual aircraft implementation. The HTRE-3 incorporated a modified General Electric J47 turbojet engine, which was a well-known engine in military aircraft at that time. The HTRE-3’s design was sophisticated, involving a direct cycle in which the air passed directly through the reactor core, getting heated in the process and then expelled to generate thrust. Moreover, the HTRE-3 featured improved radiation shielding techniques While the HTRE series ultimately did not result in operational nuclear-powered aircraft due to various strategic, technical, and ethical considerations, it significantly advanced the understanding of nuclear propulsion."
- b112 2y agoWe've come a long way in material construction in the last 50 years, I wonder if this could now be built.
- hubraumhugo 2y agoSitting here with my morning coffee and reading about a nuclear jet engine I've never heard of makes me realize how special HN is. Please, never change!
- Harmohit 2y agoThey have also tried to use nuclear power for space propulsion. Here is a fun one: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
- User23 2y agoNeal Stephenson put this to good work in his novel Anathem.
- hagbard_c 2y agoAnd, much earlier, Larry Niven and Jerry Pournelle in Footfall.
- cubefox 2y agoThis is not just a curiosity though. Nuclear pulse propulsion like Orion is actually the most advanced form of space propulsion that is within technical reach and doesn't use science fiction ingredients like large amounts of antimatter. When you read the article, you see that Orion was considered quite doable even decades ago. There actually is one system that would be even more efficient than Orion, the Medusa: https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medusa https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#Medus... Though the Medusa design is less fleshed out than Orion.
- zidad 2y agoSounds like a keeper. I don't see what could possibly go wrong with deploying these at scale everywhere.
- pfdietz 2y agoWe could see nuclear aircraft engines deployed on Titan. They would work great there.
- cabirum 2y agoThis one didn't get cancelled https://en.m.wikipedia.org/wiki/9M730_Burevestnik https://en.m.wikipedia.org/wiki/9M730_Burevestnik
- rthnbgrredf 2y agoDoes someone know how long an unmanned unclear powered aircraft could fly?