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NASA Wants to Send Nuclear Rockets to the Moon and Mars
- Arrezz 7y agoHow big is the added risk of toxic waste? I'm not sure how much waste is produced in relation to propulsion energy given but it must be quite small? And I imagine that during travel in space you could just dump that waste out into space considering the vastness of it all.
- api 7y agoI don't know for certain but I'm fairly sure that the idea is that you don't activate the reactor until it's in space. Before a reactor is turned on the fuels are less radioactive. It's once you turn it on that radioactivity increases dramatically and you get all the nasty decay products and such. So not zero but not as much as you might think. Personally I don't like the idea. Environmental concerns are real, but those aside it's likely more expensive than multiple refueling flights with big conventional rockets. These would be expendable and very costly to research, develop, fuel, and launch, whereas for the same cost you could probably put stages in orbit and send fuel up to them with reusable tankers. Like hydrogen this is another example of NASA chasing the sexiness of high performance in a pure sense (high iSP etc.) without doing a total cost analysis. In general SpaceX and Blue Origin have the right approach.
- SketchySeaBeast 7y ago> "The massive amount of energy produced by these reactors could be used to sustain human outposts on other worlds and cut the travel time to Mars in half. >“Many space exploration problems require that high-density power be available at all times, and there is a class of such problems for which nuclear power is the preferred—if not the only— option,” It seems that nuclear reactors has more utility than simple power to weight ratio.
- mlindner 7y agoNuclear reactors will be needed if you're going much further out than Earth/Mars. Solar power falls off rapidly as you go further out.
- Robotbeat 7y agoWhy is this downvoted? This is informative and (in my opinion) basically correct. And while I agree that in the near term, refueling via chemical rockets is a far cheaper (and even higher performance) way of solving this problem, I do support the research because someday we'll want to go even beyond refueling of chemical rockets. When you get REALLY high transfer times between Earth and Mars, the higher Isp makes a significant difference. To explain: Conventionally, it takes about 6-8 months to get to Mars. Nuclear thermal rockets can shorten this time for the same mass in LEO to like 3 or 4 months. HOWEVER, agreeing with what api said, you can get the same exact speedup by using refueling with conventional rockets (and aerocapture/braking/direct-entry). It increases the required mass in LEO, but if you have cheap (especially reusable) rockets, then cost to launch more mass to LEO is not a major factor compared to the cost of a nuclear thermal rocket. And this is exactly what SpaceX has proposed: (see slides 19 through 22) http://www.spacex.com/sites/spacex/files/making_life_multiplanetary_2016.pdf http://www.spacex.com/sites/spacex/files/making_life_multipl... But the Isp (exhaust velocity) advantage is maintained. The rocket equation is exponential: mass full = (empty mass)*e^((mission delta-v)/(exhaust velocity)) So eventually, when mission delta v is much higher than exhaust velocity, the mass ratio explodes. So a factor of 2 improvement in Isp is worth the extra cost, even if you have reusable rockets. The exponential curve eventually beats even the cheap, brute-force approach, if you want transfer times of on the order of 1 month. It's also the kind of work NASA should be doing. Private industry is doing a really good job reducing the cost to orbit, so NASA can focus on these longer-term problems.
- baybal2 7y ago> Why is this downvoted? This is informative and (in my opinion) basically correct. I once wrote that Chernobyl had no chance to explode in a nuclear explosion in rebuke to some guy called Moxie Marlinspike. I had -4 for the next few days on all my posts, and somebody even bothered to find my work email, and futilely tried to troll me and my colleagues into deleting my rebuke for a week. "That" demographic is definitely there, and working in a "tech" occupation does not preclude a person from being a part to it these days.
- scohesc 7y agoI would imagine the engine would be fairly inert if it's not activated until in orbit. I could see issues if the craft all of a sudden loses its orbit with an radioactive engine burning up in the atmosphere spewing radiation (although I'm sure we get bombarded with way more from the sun potentially?) Maybe if during launch something goes catastrophically wrong and blows up mid-air like a bomb of sorts?
- Symmetry 7y agoWhenever you're splitting Uranium atoms the results will tend to be radioactive. The results will build up in the fuel over time and eventually make the reactor stop working. Conventional reactors breed a bit of plutonium too as U238 captures neutrons but most aerospace reactors want to be as light as possible and so use highly enriched Uranium. So after your trip the engine will be quite radioactive but, as you point out, there's a lot of space and outside Earth's atmosphere and Van Allen belts it's moderately radioactive anyways. Thankfully nuclear reactors aren't particularly radioactive until you turn them on, which is a big improvement on the radiothermal generators, RTGs, that we sometimes use in probes headed for the outer solar system where solar panels don't work. It's during launch, before this part gets turned on, that you have a risk of crashing and losing the reactor somewhere on Earth.
- BAReF00t 7y agoWho said anything about uranium? There are elements with far more favorable decay paths. Short decay + using that decay too = pretty much a clean nuclear reactor.
- Symmetry 7y agoWell, I'm no nuclear engineer but I'd hope that if you could make one of those that was light enough NASA would use that instead.
- greglindahl 7y agoIt's called an RTG, and they've been using them for decades.
- Symmetry 7y agoI'm not sure what you're talking about? RTGs don't have short decay paths, they have to have long decay paths to last through a mission. P238 is what we use for most probes and has a half life of 88 years. It decays to U234 which has a half life of 200,000 years, short enough to be dangerous but long enough to almost never go away. RTGs tend to produce on the order of 100 watts of electricity from 500 watts of heat. A good nuclear engine will want to use 100+ megawatts when in use. And more importantly RTGs don't put out nearly enough heat to make a usable nuclear thermal rocket. The important thing is being able to turn them on when you're doing a burn but then turn them off when you're coasting to your destination then turn them on again to stop there. RTGs can't do that.
- logfromblammo 7y agoThe risk is that in a catastrophic launch failure (read: exploded rocket), the radioactive materials could be dispersed downrange. The solution--if that's really a problem--is to use the same escape systems used for crewed launches to eject the nuclear fuel with a parachute and emergency beacon, and keep it all inside a durable shielded container until the craft needs to start up the nuclear engine.
- GlenTheMachine 7y agoEffectively, they already do that. Although the United States doesn't launch reactors, we do on occasion launch radioisotope thermoelectric generators (RTGs). These use a core of sub-critical plutonium surrounded by thermocouples, which turn the heat into electricity. These are used for probes going to the outer solar system, where solar panels aren't effective enough. Anyway - there is certainly a concern with the plutonium in RTGs being dispersed by a launch failure. The engineering that goes into designing the protective system for RTGs is extensive; they each have their own miniature heat shield, and are surrounded by iridium and carbon blocks. Tests show that they can indeed survive the explosion of the launch vehicle.
- m4rtink 7y agoIIRC long ago a US RTG ended up in the ocean due to launch failure, only to be recovered and sussessfully re-launched on a new satellite. These things are tough! And also expensive, so you might as well reuse them once they shrug off the rocket exploding under them.
- mlindner 7y agoExcept that's not a big problem. A non-activated reactor just contains enriched uranium. Uranium is dug out of the ground and you can buy it on amazon and chemically concentrate it yourself. It's safe to hold and handle (wash your hands afterwards so you don't eat particles) and store in your house even. (In the US this is all legal.) Reactors only become dangerous after you activate them and short lived isotopes are created that also happen to be types that are bioavailable, like cesium-137 and strontium-90 which the body will take up and store inside the body.
- wfbarks 7y agoFor the first time, period. Doesn’t look like we had one 60 years ago...
- ceejayoz 7y agoWe did: https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA Tested successfully (on the ground) in the 60s. Real pity about its cancellation, too. It was considered for the "Grand Tour" that the Voyager probes wound up doing; they could've sent nearly 30x the spacecraft mass with NERVA rockets.
- autokad 7y agoI don't have time to verify the video at the moment, but I believe this is them testing said engine 60 years ago: https://www.youtube.com/watch?v=GmxPRCyR-Co https://www.youtube.com/watch?v=GmxPRCyR-Co
- arfaoui47 7y agoAn Arab country will be honored to host the Rocket launching..
- typeformer 7y agoUFO's are real, the government just admitted it (someday they may even admit recovered ET craft), and yet the media is failing so hard at diving in deeper. Until the headline is "NASA now has working vehicles than that can warp spacetime" I just can't be bothered to get excited.
- toxican 7y agoThey admitted to encountering the literal definition of UFO -- "Unidentified Flying Object", which in no way at all proves or even suggests alien activity. If you want to get annoyed with the media, direct it at them convincing people that "UFO" = aliens
- whatshisface 7y agoBy unidentified they probably meant unidentified to anyone without a clearance.
- everdev 7y agoUnidentified != Alien
- logfromblammo 7y agoUFO = ( classified human-built experimental aircraft | meteorological oddity | optical illusion | camera malfunction | intentional hoax ) & !( extraterrestrial artifact )
- BAReF00t 7y agoI’m disappointed. I expected a project-Orion-type interstellar solution. Not a measly ”twice as fast as conventional“ water kettle. Also, no word about what they will acually use. Because classic uranium is a quite limited resource actually. It has been said to run out even before fossil fuels. Also, why not a fusion rocket? Given that we know how to make fusion bombs. Because until we find a massive amount of anti-matter, this will be the next best thing for a loong time. The only limiting factor would be a human body's ability to withstand G forces.
- Robotbeat 7y agoAll of those things are harder than a nuclear thermal rocket. Got to walk before you run. And a fusion reactor is actually likely to be much heavier than a fission one (at least in the near term). They're using Low Enriched Uranium for this design. We have plenty of uranium (resources are huge, but no one bothers to prove them into reserves until the price is right), and not much is required for this project. Don't be disappointed by the first step in a journey not taking you immediately to the destination.
- cr0sh 7y ago> Because until we find a massive amount of anti-matter I honestly hope this never occurs, or we never are able to contain/store such a mass for any real length of time. Because if we can do it, it will be used for a weapon. Seriously - I can't even imagine what - for instance - one kilogram of anti-matter coming in contact with regular matter - the amount of energy that would be released...it staggers the imagination. Today's fusion weapons release only a fraction of their potential energy; anti-matter conversion would be 100% (roughly): https://en.wikipedia.org/wiki/Antimatter_weapon https://en.wikipedia.org/wiki/Antimatter_weapon "Using the convention that 1 kiloton TNT equivalent = 4.184×1012 joules (or one trillion calories of energy), one gram of antimatter reacting with one gram of ordinary matter results in 42.96 kilotons-equivalent of energy (though there is considerable "loss" by production of neutrinos)." So...one kilo of anti-matter would be equivalent to 42 megatons - which is close to yield of the Tsar Bomba: https://en.wikipedia.org/wiki/Tsar_Bomba https://en.wikipedia.org/wiki/Tsar_Bomba ...but in a much more compact package. 50 kg of antimatter - which would be feasible for current launch systems, and comparable in size to current warheads: https://en.wikipedia.org/wiki/W80_(nuclear_warhead) https://en.wikipedia.org/wiki/W80_(nuclear_warhead) Well - that's a 2 GT weapon...while I'm sure such a thing has been considered as to it's effects...I honestly don't know what that would be. Best guess might be that one such warhead could easily take out a good portion of say, the west coast (of the United States)? Ultimately - we are not ready in any manner - socially, morally, politically - as a species to wield that kind of power responsibly. Honestly, even nuclear weapons fall into that assessment, despite recent history - I'm honestly not sure how we have gotten this far without a major nuclear war occurring. Sadly, though, I know that my conjecture (in which I am not alone, I hope) will not do anything to stop the research - right now, though, the cost to produce anti-matter (let alone contain it) is so high as to make even a small mass cost an exorbitant amount of money. I sincerely hope there isn't any breakthrough on that front. I honestly think we, as a species, are not ready for it (that isn't to say none of us are - but those who would be responsible with such "stuff" are likely very few - I know I am not one of them).
- DoctorOetker 7y agowhat happens at the end of such a trip, when the propellant is exhausted, and can no longer evaporatively cool the core? it has to contain enough propellant to come back to Earth orbit to refuel the propellant coolant? even if the core is throttled to its lowest levels, it will still produce heat in the vacuum of space? or will radiative cooling balance the remaining production of heat?
- simonh 7y agoYou do what you would on a terrestrial reactor, and shut down the reactor e.g. by using control rods, or pulling out fuel rods to shut down the chain reaction. These wouldn't be simple radiothermal devices, but proper actively managed reactor cores. Having said that you absolutely would need active cooling even in a 'shut down' state, probably by circulating a cooling fluid to radiator fins. You might use the same fluid as the propellant or might not. In the former case sure, you wouldn't be able to use all of it as propellant.
- om3n 7y agobut what cools the radiator fins, in the absence of air?
- tandr 7y agoInfrared radiation from the hot fins to outer space should be taking energy out (cooling it) a bit, not sure how much though.
- DoctorOetker 7y agoI think he is wondering about the utility of fins geometrically speaking in steradians when it comes to radiative cooling?
- peterwoerner 7y agoIt's radiative cooling. Same way the sun heats the earth.
- stickfigure 7y agoAnyone else just get a JSON 404 page from this link? { statusCode: 404, error: "Not Found", message: "Not Found" }
- u801e 7y agoI tried it just now and was able to see the article. On another note, why do they include the HTTP status code in the JSON body? Isn't it already present in the status line of the HTTP response?
- greglindahl 7y agoPeople using funky software stacks don't always have access to the status line information, so some APIs include the status in json.
- ksaj 7y agoI got that error from another article linked to Wired from HN the other day. After a short time, I clicked again and all was fine. Something wonky is going on there, since it probably shouldn't even be 404 unless they keep deleting their articles and then resurrecting them shortly thereafter (which would be just a little weird).
- new_guy 7y agoLinks dead. Edit: available through outline https://outline.com/nbpE5n https://outline.com/nbpE5n
- bra-ket 7y agothis is great! check out project Orion https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
- inamberclad 7y agoIt's much more likely to look like NERVA than Orion. https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA These types of engines have already been run: https://www.youtube.com/watch?v=eDNX65d-FBY https://www.youtube.com/watch?v=eDNX65d-FBY
- t0mbstone 7y agoHow does one convert nuclear heat energy into directional energy for propulsion purposes?
- rmckayfleming 7y agoTake a look at this: https://en.wikipedia.org/wiki/Nuclear_lightbulb https://en.wikipedia.org/wiki/Nuclear_lightbulb
- sq_ 7y ago> which will almost certainly be used on any crewed mission to Mars. This is interesting. I hadn't seen anything about NASA plans to get humans to Mars requiring nuclear-thermal propulsion. Does NASA even currently have a serious plan for Mars missions with the whole Artemis thing going on?
- ceejayoz 7y agoThey branded Artemis as part of a larger "Moon to Mars" plan, with logo and all. https://www.nasa.gov/moontomars/ https://www.nasa.gov/moontomars/
- sq_ 7y agoInteresting. I'm kinda down on Artemis overall, as it seems like the whole thing is getting bogged down in political maneuvering, as usual. NASA keeps saying it's more than boots on the ground, but all the plans they announce seem to be boots on the ground or overly complicated paths to the surface meant to please contractors. This gem of a line from this week's Orbital Index kinda sums up why I'm preparing for disappointment: >"Meanwhile, contractors (cough Boeing? cough) are pushing for the Gateway plan to be nixed in favor of… The Exploration Upper Stage, a large interplanetary upper stage (launched on SLS Block 1B) in development by (wait for it) Boeing." Boeing and the SLS have taken forever already, and the version that may launch soonish isn't even the "real" SLS.
- ceejayoz 7y agoI'm skeptical of any human exploration plans NASA has beyond 2-4 years or so. Anything more and the next President winds up nixing it to put their own stamp on things. My money's on a commercial program like they one they've been doing for ISS resupply.
- sq_ 7y ago> My money's on a commercial program like they one they've been doing for ISS resupply. Fully agree. If I had to bet right now, I would guess that SpaceX will get humans to the moon before NASA does. They’re moving so quickly on Starship and seem extremely determined to prove their new rocket.
- hesburg 7y agoNASA lies so so much. Hard to believe anything they say. Why don't we have up to date photo of earth ? Only NASA photoshopped marble exist. I am more than skeptical :)
- teslaberry 7y agonuclear thermal propulsion should start right here on planet earth with the shipping industry. biggest low hanging fruit EVER when it comes to reducing oil useage AND reducing cost of refueling AND reducing particulates, sulfate n02 and c02 emissions. oh yea, and it's cheaper!!! .
- teslaberry 7y agostart with nuclear thermal here on earth----tiem to overhaul the shipping industry with nuclear thermal powered cargo and container ships. it's the biggest low hanging fruit EVER when it comes to reducing fuel consumption, cost, emissions, etc....
- anon234345566 7y agoso things got really serious and we need to get out there as fast as we can