https://xkcd.com/2929

Alt text:

While it seemed like a fun prank at the time, I realize my prank fire extinguishers full of leaded gasoline were a mistake.

97 points
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So, about Project Orion from Wikipedia

In August 1955, Ulam co-authored a classified paper proposing the use of nuclear fission bombs, “ejected and detonated at a considerable distance,” for propelling a vehicle in outer space.

Excuse me what the fuck

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58 points

All chemical propulsion is just controlled explosions that we use to push a thing forward. It’s not that different, as long as you don’t use it in the atmosphere or near humans.

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11 points

Yeah I know, it’s the same principle behind modern fuel engines. Still, using nukes for propelling something forward is a bit of a stretch.

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22 points

Not just nukes, but nuclear shaped charges, at a rate of maybe one per second for a manned vehicle or even more for a faster cargo only mission.

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28 points

Ah the 50s, when everything atomic was rad.

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6 points

::Fallout theme starts playing::

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2 points

“I don’t want to set the world on fire…”

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19 points

It’s not uncommon in scifi. Netflix’s Three Body Problem also explores such a solution in quite some depth.

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6 points

I love The Three Body Problem, both the books and the show. But it bothered me to no end to read Netflix’s Three Body Problem.

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3 points

I’m not familiar with the books, and the plot summary of their Wikipedia article does not mention nuclear propulsion whereas the article for the series does, so I went with that.

Unless what bothers you is the x followed by the apostrophe and the s, which I never know when to omit the s, so it is what it is.

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14 points

It would probably work just fine, but it needs a huge ship. It could get up to a few percent of the speed of light.

FWIW, nuclear test ban treaties are considered to outlaw it. I think we’re more likely to solve the technical difficulties of antimatter propulsion than we are to get over the political difficulties of nuclear bomb propulsion.

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-3 points

It could get up to a few percent of the speed of light.

So could a person sticking their head out and blowing, but it’s still a terrible idea.

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8 points
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Just as an observation, there was a time when everyone on the Internet was gaga over the idea of Project Orion, and you didn’t dare speak out against it lest you get a hail of downvotes.

It’d work fine in deep space. It’s not a good idea to launch from Earth this way. But again, we’ll probably find something better once we’re at the stage of needing it.

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13 points

Read “Footfall” for a hard scifi story featuring such a ship.

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4 points

Will do! Thanks

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4 points

I like Footfall, but it’s also a little over the top for me.

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3 points

Co-written by the guy who tried to sell the US military the concept of “rods from god” (orbital kinetic weapon). I wouldn’t expect anything less.

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7 points

Not worse than a fusion torch. Or open-cycle nuclear propulsion. Or an antimatter drive.

You know, the Kzinti lesson😉

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3 points

Never heard of those, but if they are on par with project Orion I have some nice readings to do today.

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3 points

If you’re into hard sci-fi and you’re looking for a good read, they actually dropped a pretty good recommendation with that reference at the end - Larry Niven does a great job of blending real-world theories like Dyson spheres and advanced propulsion drives, with some of the more far-flung standards of the genre like an intra-planetary teleportation grid.

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3 points

Aren’t there plans again?

Considering that you need huge shields and dampening and you only have the mass of the bomb itself as propelant, is it still as effective as controlled propulsion?

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7 points
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I think you may be mixing up Project Orion (let’s chuck bombs out of the back to make us go zoom) with NERVA (a nuclear thermal rocket engine where the heat from chemical reactions is replaced with heat from a nuclear reactor to generate gas expansion out of a nozzle). Something like NERVA is actually a great idea. Let me tell you why!

  • It’s completely clean (unlike Orion and fission-fragment rockets)

    • the reactor and fuel never touch, the fuel goes through a heat exchanger and is not radioactive
  • it provides extremely high efficiency

    • chemical rockets top out at ~400-500 isp in vacuum
    • NERVA tests in 1978 gave a vacuum isp of 841
    • ion thrusters like NEXT has an isp of 4170
  • it provides lots of thrust

    • NERVA had 246kN of thrust
    • NEXT (which was used on the DART mission) is 237 millinewtons
    • That’s 6 orders of magnitude more thrust!
  • No oxidizer is needed

    • All you need is reaction mass, just like ion thrusters

For automated probes, the extreme efficiency and low thrust of ion thrusters makes perfect sense. If we ever want to send squishy humans further afield, we need something with more thrust so we can have shorter transit times (radiation is a bastard). Musk is supposedly going to Mars with Starship, and the Raptor engine is a marvel of engineering. I don’t like the man and I’m not confident that he’ll actually follow through with his plan, but the engineers at SpaceX are doing some crazy shit that might make it happen.

Just think though, if the engine was literally twice as efficient and they didn’t need to lug around a tank of oxidizer, how much time could they shave off their transit? How much more could they send to Mars? Plus, they could potentially reduce the number of big-ass rockets they have to launch from Earth to refuel. If you can ISRU methane, then I imagine you could probably get hydrogen.

There are problems that still need to be resolved (the first that comes to mind is how to deal with cryogenic hydrogen boiling off), but like, the US had a nuclear thermal engine in the 70s. It was approved for use in space, but congress cut funding after the space race concluded so it never flew.

I’m happy to see that NASA is once again researching nuclear thermal rockets. Maybe we’ll get somewhere this time.

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1 point

I’m more with VASIMIR though, maybe with a nuclear reactor for power, since it’s variable.

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Don’t forget the mass of whatever ablates from your shield!

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3 points

They spoke to that and found it manageable. The ablation isn’t there deal breaker

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60 points

So soup sounds like an idea and is actually an idea. Checks out.

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9 points

I dont know, soup has always been a better idea than it first seemed to me

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3 points

Depends on the soup I find.

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1 point

At least when you make soup yourself it good

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1 point

YMMV. For me soup sounds like a good idea but I find it annoying to eat so for me personally it is a bad idea.

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42 points

What is this transition lense slander

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33 points
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I know right, I recently replaced my glasses with transition lenses and it’s pretty nice.

Who doesn’t want automated sunglasses? Not seeing any downsides yet. Only thing I know they don’t work in cars, but I don’t generally drive so it’s ok

The technology has come a long way since the 90s

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17 points

I find that they don’t “un-tint” when going inside fast enough for my liking, personally.

Creates kind of the opposite effect of going from a dim room into a bright space. Instead of evrything seeming extra bright, it just dimmed everything and made it more difficult to see.

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14 points

One problem my mom did not anticipate was that she would be stuck effectively wearing sunglasses for my brother’s outdoor wedding, where was sitting up with the bride and groom for the whole thing (Indian wedding). She just looked like an asshole, and continues to look like an asshole in the just about every photo of the ceremony. Oops.

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Why would wearing sunglasses outdoors make someone look like an asshole?

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2 points

Haha. Good point. You pretty much always have sunglasses on outside like it or not. Even when its shady

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11 points

In the cold they take too long to transition to clear. So you end up taking them off for a few seconds when you go inside. It’s only minorly annoying.

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12 points

To be fair, regular glasses mist up anyway when going inside from the cold, so you take them off anyway

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3 points

Didn’t really notice much in the winter here

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7 points

Can confirm, it’s all positives with the only downside being that it costs a little more.

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3 points

They have different varieties, some do work in the car

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4 points

But then they would probably work in a well lit office too.

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33 points

I was under the impression that bloodletting could in some cases actually be beneficial.

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34 points

Yeah, for people with hemochromatosis (too much iron in the blood) the main treatment is still bloodletting.

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4 points

Or go piss off Magneto

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15 points
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Yeah, it’s still practiced. But the whole four humors thing is a bit old hat.

I think there’s a few of these misplaced. Heelys>transition lens.

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7 points

And also often in such cases, blood donation is suggested instead.

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3 points

Heelys>transition lens.

I dunno, seems kinda unrelated…

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8 points

Also leeches are used to help veins heal after reattaching fingers/ears/other dangly bits, which is a form of bloodletting

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7 points

Yeah it can reduce PFAS levels in your system. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2790905

Though better to just donate that blood than let it go to waste.

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1 point
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Didn’t Paul McCartney write a song about blood letting?

🎵if this ever-changing world in which we’re living makes you give in to need… Live and let bleed!🎵

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26 points

Excuse me, what about pizza in squares?

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28 points

I guess because there is no crust to grab. Gotta get grease and maybe sauce on your hands to eat the inner squares.

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6 points

But square pizza is the sort you eat with fork and knive tho?

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13 points
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Not necesarilly. I fear we have to face it: This is one of the rare cases where xkcd fucked it up.

https://youtu.be/Oc9Wigm_kCE?si=AIaUu9123D9k4kGB&t=343

https://en.wikipedia.org/wiki/Pizza_al_taglio

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8 points

There is no pizza acceptable to eat with fork and knife.

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-1 points

Any pizza that requires utensils is not pizza.

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3 points

As a fork-and-knife pizza eater, I have come around to pizza squares.

That said, PIZZA BELONGS IN A TRIANGLE

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2 points
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This can be solved by using a napkin

(Or just not caring about the problem anyhow)

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1 point

Or by cutting it into standard slices. But yeah napkins and apathy work too.

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5 points

If the pizza is a square or rectangle (like Detroit deep dish or a flatbread) it is on, but round pizza cut in squares is just bad

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3 points
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The only correct way to cut (not too gigantic) round pizza is into six parts so you get equilateral triangles (well, modulo a curved section) which is ideal for holding.

Home-made pizza rarely if ever is round, though, in which you probably don’t want to go for squares but eyeball some appropriately-sized rectangles.

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