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HeebieMcJeeberson t1_j22k5c1 wrote

Maybe 20 years ago I read about a theoretical engine called a Nuclear Lightbulb. It contains basically a large quartz bulb with a cloud of gaseous uranium hexafluoride inside, compressed by air jets blowing in to make it dense enough to fission and not let it touch the bulb. The glowing ball of fissioning plasma emits intense UV, which the quartz is 100% transparent to.

Around the outside of the quartz bulb flows a stream of hydrogen gas doped with some other material (I forget what) which highly absorbs the UV, heating the hydrogen, which expands and goes out through a rocket nozzle to produce thrust.

Power - The specific impulse of this engine would be on the order of 30,000 seconds - something like 60 or 80x that of the space shuttle main engine. The guy who wrote the article gave a design weighing 3000 tons (the weight of a Saturn V), but in the nuclear rocket 1/3 of that would be cargo. A thousand tons of cargo per launch.

Safety - The plasma cloud in the bulb is self-containing, because if it gets too hot it expands, making it no longer dense enough to be critical, so it stops fissioning. The whole thing is in a chamber lined with boron or something (whatever they use in nuclear reactors to absorb neutrons). So there's no emission of radiation or radioactive material, just very hot gas. Even if the entire rocket blew up in the atmosphere it would release 2% of the radioactive material of a typical 1950s atom bomb test.

With so much cargo capacity this rocket could take a fully equipped base to Mars in one shot, along with dozens of inhabitants and provisions, in about three months. It could have a double hull containing a foot-thick layer of water, which would shield the passengers from 95% of the radiation that would hit the ship during the trip. The outer few inches would freeze in space, providing passive self-healing in case of micrometeorites, because punctures would instantly leak water and freeze.

The author mentioned another cool feature. When a rocket is launched it always has a parabolic trajectory and then does an engine burn to circularize the orbit. This circularization burn is aimed toward space, so if it were timed right it could be used to eject a small amount of nuclear waste aimed at the sun. The rocket's exhaust velocity would be sufficient to send material out of orbit on a slow trip ending at the sun. What a great way to gradually get rid of nuclear waste.

I can no longer find the original articles I read, but here's one from 2020

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dern_the_hermit t1_j22zlmo wrote

> What a great way to gradually get rid of nuclear waste.

Well, for its own waste, sure, since it's already out of Earth's gravity well. For current terrestrial stuff I say we just blast it with lasers until it's whittled down to less-harmful elements. Bonus: We can do this with other toxic substances too.

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HeebieMcJeeberson t1_j23042o wrote

Wow that sounds like the magic bullet the nuclear industry has been waiting for. I never even heard of "Chirped Pulse Amplification" before.

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dern_the_hermit t1_j230adl wrote

It's crazy energy-intensive, so only makes sense with a very robust and non-emitting energy grid. So waste is gonna be sitting in those concrete casks for many decades yet.

Still, I favor this option over burying it.

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zdakat t1_j232pk1 wrote

Guess the waste pack atomizer in Rimworld is based on a real thing then

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Pirat6662001 t1_j253bhd wrote

Fusion, basically all of our future techs depend on fusion becoming an actual reality

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dern_the_hermit t1_j254b45 wrote

Renewables, actually, and solar in particular. A large amount of solar installation will create an interesting paradigm: If designed around being sufficient during the annual minimum (ie- winter), seasonal variation will net a huge excess of generation in the summer. Tap some of that excess to break down harmful substances.

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Blakut t1_j2387ey wrote

nuclear waste is made into something more than it is by climate activists, in reality all the dangerous waste ever produced would fit on cube the size of a football field.

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HeebieMcJeeberson t1_j2395rr wrote

Yeah the thing is that it's not a cube the size of a football field, it's in thousands of containers in numerous storage locations all over, and in every place the containers have to be checked and periodically replaced or repaired. I know some people overplay the danger but it's not a trivial problem to underplay either.

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ShaggysGTI t1_j23rvhj wrote

The Goiania Incident

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HeebieMcJeeberson t1_j264fc6 wrote

This is the story of a 1987 incident in Brazil, in which a small canister of Cesium^137 that had been left in an abandoned cancer treatment facility was found by randos who sold it to a junk dealer, who noticed it glowing blue at night and opened it. A handful of cesium chloride crystals and dust ended up being distributed to people around the community, who used it to bling their bodies and possessions. When people immediately got sick the news reached national authorities, who eventually tested over 100,000 people for exposure. Almost 250 people were highly contaminated, 4 died and 20 developed serious injuries, losing fingers and other body parts. A city block of buildings was demolished and the debris was sealed up along with cars, clothing, family possessions, etc. It was the worst radiological disaster in Brazil's history.

It's a good story about the dangers of badly managing radioactive materials, and what can happen when concentrated nuclides used in thousands of hospitals around the world are opened and handled by people who don't know what they're doing. I'm guessing somebody thought this was relevant to my statement that a total rocket failure would release 2% of the contaminants from a single typical 1950s atom bomb test (more than 2000 of which were performed worldwide).

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boh_nor12 t1_j24r3ki wrote

But definitely in the size of a few foot all fields. At least for the North American WIPP site (been there in person a few times).

https://www.wipp.energy.gov/

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HeebieMcJeeberson t1_j25whne wrote

Nuclear waste depositories in America

When WIPP says "disposal" they mean "storage".

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boh_nor12 t1_j26hwfd wrote

You know, that's an interesting thought.... Disposal vs storage. What classifies as "disposal?" Physically altering something? I'm going to think on this a little.

Edit: and apologies for not commenting on your link. You are correct, those are sites of commercial byproduct. From my understanding, the WIPP is only utilized for federal nuclear waste. At the moment, the US does not have a permanent geological storage/disposal facility for commercial waste. Each of those on that map are most facilities that used to have a reactor nearby.

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Withstrangeaeons_ t1_j26j6n3 wrote

Yes. And I think this is kind of good - after all, why bury that much potential energy when you can just use it.

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The_Illist_Physicist t1_j23drw8 wrote

It's a fairly common laser amplification technique, the lab I work in uses Chirped Pulse Amplification for a lot of our pulsed lasers.

In order to get an ultrashort pulse of light (short in the time domain) it must be made of a large spectrum of frequencies/colors (long in the spectral domain). This is essentially the Fourier transform relationship, similar to the uncertainty principle.

The problem with high energy, ultrashort pulses is that they like to burn optics. You'll toast a lens if you send a beam with enough power through it. So what you do is separate the pulse into its many colors, amplify them individually, and then recombine. It's simple yet brilliant at the same time.

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Withstrangeaeons_ t1_j26i3cf wrote

We already have the magic bullet, and we've had it since the US government made nukes. Search up "nuclear waste reprocessing", but also the costs associated with it. Then Google the price to mine one kg of uranium or thorium, and you'll see why reprocessing hasn't been done yet. Sure would be a shame if the unwashed masses decided to just bury all that potential energy, though (in case it becomes more expensive to mine radioactive material), out of fear of anything having to do with radiation.

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HeebieMcJeeberson t1_j27phgg wrote

If you want to go down the government rabbit hole think about thorium reactors, which would be safer and cheaper than uranium/plutonium and with much less waste. We could have had these long ago, but thorium reactors can't produce weapons-grade plutonium, which is why the research money didn't go that route.

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Withstrangeaeons_ t1_j2duwzp wrote

Exactly. My take on those people's thinking:

"Say, boss, I noticed that this thing called thorium is also radioactive."

"Can it be turned into nukes?"

"Uhhhh.... It's harder, but yo-"

"Scrap it! Uranium is better for our purposes, then. Forget about thorium."

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doctorcrimson t1_j2386a6 wrote

Uh, hang on, how does it stay cool? Nuclear reactors require constant cooling to prevent meltdowns, you can't just use the same materials and expect this sort of craft to not begin shooting high energy beams through the hull midflight.

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Dmgfh t1_j23olzp wrote

The hydrogen being pumped around it probably doubles as coolant

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doctorcrimson t1_j2465oo wrote

That checks out if there's enough space between the wall and the bulb where it is being heated to the point of becoming rocket propellant, I think this would actually work pretty well for larger rockets and cargo rockets as was stated.

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Mayor__Defacto t1_j24y9ux wrote

The hydrogen being ejected is coolant and propellant at the same time.

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Weazy-N420 t1_j23gw2x wrote

The water for radiation shielding & hole plugging is absolutely insane level genius I think. It is quite heavy though which could be why it’s not even considered. You’d think even a 12” layer of H2O would provide some protection.

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Blakut t1_j23892g wrote

how would one prevent neutrons from totally wrecking yout shit?

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HeebieMcJeeberson t1_j238pkg wrote

The casing around the thing is a neutron-absorbant boron material, the same as used in conventional reactors. Eventually the boron becomes radioactive and has to be changed, and this is the waste the author talked about ejecting toward the sun.

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Makhnos_Tachanka t1_j24trec wrote

Oh that's nothing. A dusty plasma fission fragment rocket can deliver an ISP of 1-2 million seconds, using technology with already high TRLs.

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HeebieMcJeeberson t1_j25z74f wrote

Thanks, this is yet another design I hadn't heard of. Here's a PDF describing it in detail. The "dusty plasma" engine does have the drawback of being unable to land due to spewing highly radioactive rocket exhaust. So for missions that involve landing it would have to carry a conventional lander with it, or an unmanned one could be sent more slowly to rendezvous near the destination.

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Benway23 t1_j24wd85 wrote

Jesus fuckin chrst. That is amazing.

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serialteg t1_j26h73p wrote

Is ejecting waste into the Sun a plausible solution in general?

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HeebieMcJeeberson t1_j27op8z wrote

Well yeah, it would permanently remove the waste from the Earth and reduce it to indisdinguishable subatomic particles and plasma inside the sun. Adding it a little at a time to a stream of rocket exhaust with the velocity to easily reach the sun is highly plausible.

Could this damage or affect the sun somehow? No, every week the sun spits out about 1 to 20 coronal mass ejections of roughly a billion tons each. All the nuclear waste in the world amounts to about 250,000 tons, and the rocket would send maybe 100 pounds at a time toward the sun. Very tiny farts compared to a continuous series of very large hurricanes.

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serialteg t1_j2c4sb3 wrote

I've theorized about that for a long time.

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ArceusTheLegendary50 t1_j2fome5 wrote

>What a great way to gradually get rid of nuclear waste.

Kurzgesagt made a video on this and explains precisely why this is a terrible idea. The basic gist of it is that "what goes around comes around" is very literally the problem: aiming at the sun isn't actually very easy and there's still a good chance it'll go back to Earth.

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HeebieMcJeeberson t1_j2ftpvm wrote

The Kurzgesagt video is well produced but surprisingly misleading. The drawbacks it brings up are all based on launching all of our nuclear waste into space, using present-day rockets with today's reliability levels, dedicated entirely to this one purpose, and each carrying the largest possible payload of waste. Most puzzlingly, it dismisses hitting the sun as difficult - as if it's any harder than hitting the moon, Mars, an asteroid, or any other space object we've been hitting consistently for decades. "What goes around comes around" is literally a terrible oversimplification that ignores reality.

The impracticalities the video discusses simply aren't relevant to adding a modest amount of waste to rocket exhaust as I described. But yes I agree that the strawman concept of launching nuclear waste into space on the scale described in the video would be a terrible idea.

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