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The US government is taking a step toward space-based nuclear propulsion
- mdorazio 3y agoFinally! This is one of the few fission uses I'm genuinely excited about. Nuclear-thermal just makes so much sense for in-space propulsion of large vessels compared to chemical rockets.
- somenameforme 3y agoI think the obvious concern would be failure scenarios. There will always be failures in space technology. As space expands exponentially (as it is likely to do so in the future), failures will become relatively regular. So the obvious question would be what would happen if a nuclear rocket, with reaction in process, crashed to Earth. Or even if it broke up in the atmosphere.
- ethbr1 3y agoThe idea is also to use this for solar system propulsion, rather than Earth to orbit. Consequently, reactor payloads would be carried on a very small fraction of launches, then used in space for an extended amount of time.
- semi-extrinsic 3y agoI assume here you mean to denote by "space" the number of human spacecraft, and not the negative pressure contribution in the cosmological stress-energy tensor. In that case, why should it be likely to expand exponentially in the future?
- sebzim4500 3y ago>As space expands exponentially (as it is likely to do so in the future), failures will become relatively regular. It's possible that reliability/safety will improve as fast as the launch cadence does, in which case we could see the accident rate staying flat or decreasing.
- pdntspa 3y agoIsn't there a way you can shoot the whole apparatus into the sky while it is inert and then activate in space?
- nukeman 3y agoYes, you can have the reactor offline, with control rods inserted for launch. Then when you reach the requisite altitude, withdraw the control rods and start up the reactor. In the event of a launch accident and potential destruction of the reactor, the enriched uranium fuel would be a chemical hazard (uranium is a heavy metal like lead), but only a mild radiation hazard (since there are no high-gamma fission products, and the uranium has undergone heavy purification prior to fuel fabrication).
- m4rtink 3y agoI think this is the default for any launch of reactors from Earth - launch inert, possibly in pieces and ideally in re-entry proof capsules so you prevent contamination and can re-launch after a failure.
- aziaziazi 3y agoIt already happened with Kosmos 954 and will probably happen again soon: ~20 other satellites had been sent in space with the same tech. Kosmos crashed away from (human) life centers but that was a huge stroke of luck. Research area was 100k+ km2. Launches are less to be feared because they are oriented toward sea and the most critical moment are the first minutes. The device discussed is intended to travel away from earth so as you noted it won’t be dangerous after it quit orbit. Disclaimer: not skilled in any related field, just a consumer of space science popularization videos for newbies.
- flagrant_taco 3y agoIt's crazy to me that people largely consider it safe as long as the unspent fuel or nuclear debris is dumped into the ocean. (Not a direct comment on your opinion specifically, just building of the general idea)
- adastra22 3y agoBecause it largely is? It ends up on the sea bed, covered in sediment, then eventually recycled into the Earth’s mantle some millions of years from now. It doesn’t enter the biosphere.
- aziaziazi 3y agoOceans, marine fauna and marine flora are part of the biosphere.
- adastra22 3y agoNone of those exist in the regions where these satellites and rocket stages crash. These are natural dead patches.
- aziaziazi 3y agoAny evidence/reference to back this up? Oceans are the cradle of life and are still populated by fishes, mammals, zoo and phytoplancton even away from coastlines. http://comlmaps.org/gallery/footprints/ http://comlmaps.org/gallery/footprints/
- avar 3y ago> Or even if it broke up > in the atmosphere. The atmosphere we've already detonated over 500 nuclear weapons in?
- pixl97 3y agoMostly about the ocean it would typically fall into in the most common failure shortly after launch scenario.
- Retric 3y agoNuclear testing got to carefully select locations to minimize harm, uncontrolled reentry of nuclear rockets has significantly less control. It’s not the 99 rockets falling into the ocean shortly after launch that are problematic, it’s the 1 that almost works but then lands in the city we should be concerned with.
- TheSpiceIsLife 3y agoHow often do failed rockets, or any space debris, fall on cities?
- askvictor 3y agoNot falling on a city, but debris from Russia's launch last week was seen and heard in Melbourne, Australia: https://www.abc.net.au/news/2023-08-08/space-junk-leaves-trail-across-melbourne-sky/102700674 https://www.abc.net.au/news/2023-08-08/space-junk-leaves-tra... That's pretty close for what would be high level nuclear material.
- flagrant_taco 3y agoWe might see more obvious direct human impact from debris landed in cities, but nuclear debris falling into the ocean or land that isn't densely populated by humans still has plenty of bad side effects.
- m4rtink 3y ago
- SkyMarshal 3y ago>As space expands exponentially (as it is likely to do so in the future), failures will become relatively regular. Or it could go the way of the airline industry where failures become less regular as the industry develops ways of systematically reducing them. Also, nuclear rockets should probably be launched to earth orbit in pieces, separately, so that if any one launch fails it won’t create a nuclear accident in the biosphere. Then assemble and power up the nuclear rocket as far away from earth as possible.
- numpad0 3y agoThe solution to this is to build it in the moon from moon rocks and send it by maglev trains. Full scale spaceships can be 3D printed in parts, assembled on-orbit, and Dragon/Starliner class rowboats can be used to board it.
- m4rtink 3y agoLonger term - definitely thats the way to go. But first we need to build all this infrastructure & nuclear termal propulsion might be already necessary to get there.
- jamesaurichs 3y agoUS seems to be in a hardware/science renaissance, now that there is a new Cold War enemy, and manufacturing and research are being brought back to US.
- echelon 3y agoPeace time = smart phone incrementalism, social media, ad tech, Bitcoin, NFTs, WeWork, low interest rate malinvestment, Twitter/Tumblr pessimism Cold war = rocket science, new fuels, materials science, major computing advancements, supply chain changes, innovation, science hype, broad optimism I know most of this is happenstance and that peace time doesn't itself cause lackluster development, but it is interesting and palpable. I was so down on 2000 - 2020, but the decade ahead is exciting, and I'm filled with motivation.
- vkou 3y agoBroad optimism? Science hype? Are we living in the same country?
- rbanffy 3y agoOne thing I learned from the outside, the US - like any large country, BTW - is wildly diverse in pretty much every aspect.
- cheese_van 3y agoIt's almost intuitive if you consider the distance from Bangor to LA is pretty much the same distance as Madrid to Moscow. Think of the diversity between Madrid and Moscow. Bangor to LA won't take you through an equal amount of diverse cultures, the US is a single country after all, but the diversity is certainly there.
- rbanffy 3y agoNot that intuitive, as the country has a language in common and one can simply drive from Bangor to LA without any local government asking questions. I have the impression cultural differences spring more from the economic and educational ones, unlike Madrid and Moscow, which have very long histories that are almost completely disconnected for most of that time.
- asu_thomas 3y ago[flagged]
- zaptrem 3y agoInvestment in space has historically led to a disproportionate return in economic growth.
- FirmwareBurner 3y agoProbably because there is no oil in space and nobody to sell ads to.
- version_five 3y agoIt's funny because it's this, turning inward and waging war on ourselves after there wasn't an obvious enemy anymore that's responsible for the decline the upstream comment was talking about. Post WWII through the 90s saw massive increases in global standard of living, 2020's the west has gone back to religious squabbles over absurd ideological things. Watchmen had a similar idea.
- pixl97 3y agoPost WWII understood how terrible war was. Post 90s those that experienced it in mass were going extinct. We forgot what fascism did to the past and too many are embracing it again.
- WalterBright 3y agoOr the definition of fascism has expanded to cover all one's political enemies.
- pixl97 3y agohttps://youtu.be/9XTJNy_OrjE https://youtu.be/9XTJNy_OrjE Why does the definition need expanded?
- honeybadger1 3y agoThe more adoption of nuclear technologies with practical application, the better.
- bigfudge 3y agoThat’s an odd thing to say. Almost as if you’re in favour of nuclear for nuclear’s sake? Plenty of people have reasonable reservations about use of nuclear, not least the social /political ones of where to store waste that are still mostly unsolved. Blasting fission cores into space on rockets with fairly high failure rates in absolute terms seems like a fairly fine balance to strike?
- 23B1 3y agoProbably depends on your risk profile. Do we find new ways to safely generate energy using nuclear, or slowly cook ourselves alive on the planet's surface? Or to put it another way, at what point should we throw a Hail Mary in the energy demand game?
- honeybadger1 3y agoPeople here tend to run to extremes when they disagree with something. I am not here to detail out every individual practical application for nuclear energy; I am also not here to say where it should be avoided. Something something naysayers have a problem for every solution. There is and has been a anti-nuclear sentiment when it comes to energy written in media for quite a few years and seeing that sentiment be turned around is positive. I am convinced(and it's just an opinion) the negative portrayal of nuclear energy is directly related to the financial influence that oil and other energies have over many sectors of the economy and government.
- randallsquared 3y agoYou don't need to store nuclear waste, since you can burn it up in some fuel cycles. Essentially all the problems of nuclear power on the ground are political issues -- entrenched interests, weapons proliferation, and so forth -- not technological ones like safer reactors and nuclear waste.
- deleted 3y ago[deleted]
- mvdwoord 3y agoSo they are strapping a nuclear power plant to a huge vessel of explosive liquids.. Will the first launch be on PPV?
- JumpCrisscross 3y agoRTGs have been going to space since the 60s [1]. [1] https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_generator https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...
- flangola7 3y agoRTGs do not use fission and do not create fission products. Nuclear fuels are harmless in comparison to Strontium-90 and Cesium-137.
- 65a 3y agoThen you are going to love SNAP-10A https://en.wikipedia.org/wiki/SNAP-10A https://en.wikipedia.org/wiki/SNAP-10A
- moffkalast 3y agoAnd the 31 RORSAT reactors https://en.wikipedia.org/wiki/BES-5 https://en.wikipedia.org/wiki/BES-5
- philipkglass 3y agoThere won't be any fission products in the fuel if the chemical launcher fails to take the nuclear payload to orbit. The reactor activates for the first time after the initial orbital launch. The virgin fission fuel is less radiotoxic than RTG fuel.
- flangola7 3y ago>The reactor activates for the first time after the initial orbital launch. So they're going to launch an untested reactor into orbit without even turning it on first? Getting a reactor up and running is hard enough on the ground. I would expect any reactor to have had thousands of hours of testing and tweaking before being placed on the launch pad; that is the process for military boats and we have 60 years of experience in that environment.
- devanatha 3y agohttps://en.wikipedia.org/wiki/TEM_(nuclear_propulsion) https://en.wikipedia.org/wiki/TEM_(nuclear_propulsion)
- credit_guy 3y agoThis is not the same. It's nuclear electric propulsion, not nuclear thermal propulsion. A nuclear reactor generates electricity and that electricity drives an ion thruster. The specific impulse is astounding (7000 seconds vs 450 seconds for the best chemical rockets), but the thrust is absolutely wimpy (15 Newtons, vs 250 kilo-Newtons for the US NERVA nuclear thermal rocket engine).
- yieldcrv 3y agoIf we can build them in space I would be interested
- dtagames 3y agoThis might be a good time to review the number of failed rocket launches we've seen in the last few years. Now, imagine them with nuclear materials aboard.
- Tuna-Fish 3y agoUranium that has not been in a reactor is almost nonradioactive and inert. It only gets spicy after you let it go critical for a while, and fission products accumulate. Any reasonable nuclear-powered craft would not start up the reactor until it's already in a nice, safe, high orbit.
- valine 3y agoReusability helps with long term reliability. You would probably want to avoid launching nuclear material on a new rocket, but a human rated rocket like Falcon 9 would be totally fine.
- ben_w 3y agoDepending on the design, failure during launch can be anywhere from "meh" to "basically high-altitude Chernobyl" — random actinide decay products (and plutonium fuel) are bad, unreacted uranium fuel is mostly a heavy metal hazard rather than a radiation hazard. (Could be worse, but the Orion drive is currently illegal by treaty and hopefully nobody is dumb enough to use that in Earth's ionosphere anyway).
- aio2 3y agoI remember learning that when they started testing atomic bombs (I think?) the nuclear debris in the air spread basically throughout the whole united states and the government tried to keep quiet about it. Something similar will probably happen here if they mess up with the launch. Btw, the video I saw was on Veritasium.
- PartiallyTyped 3y agoI remember that video; the long story short was that a manufacturer of films for photography noticed that their films had spots on them, they initially thought it was defects, but because they had samples prior to testing, they saw an uptick. But maybe I remember wrong. Edit: the video in question is [1] and the conpany was Kodak. [1] https://youtu.be/7pSqk-XV2QM https://youtu.be/7pSqk-XV2QM
- pseingatl 3y agoBut, can we get to .99c?
- speed_spread 3y agoStarting now, within your lifetime? No.
- whycome 3y ago> Wernher von Braun, the German engineer who defected to the United States after World War II, recognized the potential of nuclear thermal propulsion even before his Saturn V rocket landed humans on the Moon with chemical propulsion > German engineer Why does von Braun get such a pass from his Nazi past? Because he was useful?
- themodelplumber 3y agoYeah, I think a lot of people would say that one's actions post-war are worth some weight in the equation, and culturally this person was positioned so as to not only make a big positive contribution in that quite separate context as far as values go, but a contribution which was also part of "our side" of a pitched cultural battle which is still raging. So like, how Nazi could you still be, in that actions-speaking sense. Plus, people-controversy is a topic that's actively avoided in writing for a lot of audiences, especially if it invites fault-spreading, like if it's going to end up as a big whataboutism-fest. Difficult topic in its way. Including of course the WW2-and-prior way involving terrible aspects like forced labor working under him, etc. So, less of a defense of a person here and more of a guess about rationale in authorship.
- Arkhaine_kupo 3y ago"If Hannibal Lecter ran a 4.3, the NFL would call it an eating disorder". People who are extremely succesful in certain fields get an impressive amount of leeway to break every conventional rule, law or protocol. Allowing nazis to clean up their past and work for NASA is not the only horrible things the US did during the war or immidietly after either...
- schiffern 3y ago>Why does von Braun get such a pass from his Nazi past? Partly it's because his Operation Paperclip dossier was conveniently misplaced before it could be declassified. Who knows what was in there? Not historians, that's who... Source: https://www.archives.gov/iwg/declassified-records/rg-330-defense-secretary https://www.archives.gov/iwg/declassified-records/rg-330-def...
- version_five 3y agoThe basic idea is straightforward: A nuclear reactor rapidly heats up a propellant, probably liquid hydrogen, and then this gas expands and is passed out a nozzle, creating thrust. But engineering all of this for in-space propulsion is challenging, and then there is the regulatory difficulty of building a nuclear reactor and safely launching it into space. Can anyone give a eli5 explanation of what makes this better than a conventional rocket? There still needs to b some mass ejected obviously. Is it that nuclear heat is able to make it go faster and provide more reactive force than burning it? What does the analysis look like?
- rich_sasha 3y agoThe propellant is important for its bulk (some mass to shoot out the back) and it's energy. In a chemical rocket, the propellant provides both the bulk and the energy. As it happens, there isn't that much energy in chemical propellants per kg, but the rest of the engine is light enough that these things can fly to orbit. In a nuclear rocket, the energy comes from a nuclear reaction and the gaseous fuel only provides the bulk. This is way more efficient. But such rockets likely cannot achieve orbit on their own because the whole set up is too heavy.
- morkalork 3y agoWould it be possible to skim the upper atmosphere while in orbit around a planet and top-up the gas reserves?
- MPSimmons 3y agoAlmost definitely not. If there's enough material to collect in a realistically short timeframe, there's enough drag to bring the craft back into the atmosphere.
- dgoldstein0 3y agoAlso you'd be fighting conservation of momentum - if the material you gather isn't going your speed and direction, you lose some of your speed and direction to pick it up. Given how fast anything has to go to reach orbit (about 17000mph for low Earth orbit) and escape velocity is about 41% higher, that speed difference would be a major problem. For atmospheric flight the closest thing is a jet engine which is "air breathing", i.e. requires air to run and works in part by sucking air in, using some of the Oxygen in it for combustion, and shoving the extra air out the back. This gives them much higher efficiency than chemical rocket engines, as they don't have to carry their own oxidizer or the mass to eject for propulsion - but only works because the air is dense enough where they operate. Which is not true for space flight. Commercial jets typically fly a bit under the speed of sound in air which is 767mph. Of course supersonic air craft exist - I think mach 5 is achievable by some military jets - but that's still a fraction of orbital velocity. Anyhow running in the atmosphere means jets don't "scoop up air" in any sense but rather just use it immediately - so any lost momentum can be immediately countered by the engine. Another direction to think about it - a simple model for air resistance says that air resistance increases with the square of your velocity (and with the density of air, which exponentially decays with height though also depends on temperature. I think the height wins out though. Not sure if the equation works at extremely high altitude. But certainly this favors using air at lower altitudes and probably also lower speeds https://en.wikipedia.org/wiki/Drag_(physics) https://en.wikipedia.org/wiki/Drag_(physics) https://en.wikipedia.org/wiki/Density_of_air https://en.wikipedia.org/wiki/Density_of_air
- foreverobama 3y ago[dead]
- zgluck 3y agoThe reason communications with the Voyager 1/2 twin probes have lasted for like 45 years: Voyager 2 is equipped with three Multihundred-Watt radioisotope thermoelectric generators (MHW RTG). Each RTG includes 24 pressed plutonium oxide spheres, and provided enough heat to generate approximately 157 W of electrical power at launch.
- secondcoming 3y agoIs Anthony Zuppero involved? [0]. He is/was a scientist who wanted to build a rocket that could travel the Solar System [1] [0] https://www.theregister.com/2009/11/15/zuppero_solar_system/ https://www.theregister.com/2009/11/15/zuppero_solar_system/ [1] http://www.neofuel.com/inhabit/inhabit.pdf http://www.neofuel.com/inhabit/inhabit.pdf
- tiffanyg 3y agoAw man, forget all that noise. Bring back "Project Orion"*, baby! If we're not gettin' out our (NASA-approved) Huarache sandals, "waxing down" our pusher plate, and surfing "the pocket" of those sweet nuclear detonations in the near future, then, I'm afraid our species is utterly consigned to the category of "posers"!! See, Kilgore knew how to put this kind of (heavier) ordnance to good use: https://youtu.be/8XJYnKhI_x0?t=1m06s https://youtu.be/8XJYnKhI_x0?t=1m06s ... and it don't get heavier than nuclear for us, currently! * https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
- api 3y agoI loved hearing this called “the Devil’s pogo stick” once. There were some paper studies showing that a thermonuclear version could theoretically work and reach speeds up to 10% the speed of light, which would be the Centauri system in a bit over 45 years. Of course you would have to slow down too which probably adds another few years. If this can be theoretically done with technology contemporary with the Summer of Love, it really does make the Fermi paradox seem like something real.
- Grimburger 3y ago> Of course you would have to slow down Not particularly necessary, most of the starshot type plans made seem to be fly-bys.
- credit_guy 3y agoFor anyone who wants a refresher on the UNS nuclear thermal rocket propulsion program from the '60s, here's the final report. It's a very good read: https://ntrs.nasa.gov/api/citations/19920005899/downloads/19920005899.pdf https://ntrs.nasa.gov/api/citations/19920005899/downloads/19... For this new initiative, I can see 2 big differences. On one hand they will use medium enriched uranium (up to 20%), while the original program used highly enriched one (85%), so it's going to be more challenging to extract as much power from a compact reactor. On the other hand, in 2023 we have computers and nuclear reactor simulation software that was not available in 1960, so that could provide a huge advantage. The biggest challenge I see is how to power down the engine. You can't simply flip a switch a turn off a nuclear reactor. You can stick in all the control rods, and the fission stops in less than a second, but the fission products will continue to generate heat for a few hours, initially at about 10% of the full reactor power. During this cool-down period, you will use the same coolant (hydrogen) as during normal operation, but you won't get the same exhaust velocity. With a traditional chemical rocket you don't have this problem. If you get a specific impulse of 450 s, you always get that. If a nuclear thermal rocket can get 900 s running at full throttle, but it goes down to 100 seconds in cool down mode, the main advantage might not be so great after all.
- leereeves 3y ago> During this cool-down period, you will use the same coolant (hydrogen) as during normal operation, but you won't get the same exhaust velocity. That seems like a waste of propellant. Once the reactor has cooled enough that you won't get the desired exhaust velocity, couldn't you allow it to finish cooling down by radiative cooling?
- m4rtink 3y agoI think the internal temperature might get high enough to melt things ? You could have a separate cooling system, but that will add more complexity and mass.
- fallingknife 3y agoWhy are they nerfing the uranium like that?
- entriesfull 3y agoCan they take a step forward and fix their drug crises, homelessness, and corruption first? Oh wait, helping the poor doesn't make those holding stocks in these companies any money. Maybe they can propulse their rockets with their politicians hot air.
- corn13read 3y ago[dead]
- eslaught 3y agoDoesn't hydrogen have issues with embrittlement [1]? I'm no expert, but why are they choosing that as the propellant instead of something else? [1]: https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement
- panick21_ 3y agoHydrogen embattlement is a long term issue, it isn't really a big problem for this application.
- panick21_ 3y agoI would much prefer the US to focus on space based nuclear reactors, both for surface and for in space propulsion for electric transport. Much better reward.
- yioijj78798798 3y agoGiven that we clearly have UFOs in US Army bases that have been reverse engineered what's the point of all this old stuff ?
- bagels 3y agoIt's not clear that we have technology from outside of earth. These statements are from a guy who has said that another guy told him about aliens.