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.

  • Wild_Mastic@lemmy.worldEnglish
    891·
    6 个月前

    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

    • Cethin@lemmy.zipEnglish
      52·
      6 个月前

      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.

      • Wild_Mastic@lemmy.worldEnglish
        122·
        6 个月前

        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.

        • notabot@lemm.eeEnglish
          19·
          6 个月前

          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.

          • Promethiel@lemmy.worldEnglish
            51·
            6 个月前

            If you can trust the human monkeys with the “shaping” of a rock that got us here, how you gonna distrust the widdle trivial matter of taking little bits of something and splitting them.

            It’s shaped charges, it’s totally fine and sane. I’d happily get on the 1,000th Orion flight*.

            *Only if that’s a fresh hull

    • SonnyVabitch@lemmy.worldEnglish
      19·
      6 个月前

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

      • jballs@sh.itjust.worksEnglish
        6·
        6 个月前

        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.

        • SonnyVabitch@lemmy.worldEnglish
          3·
          6 个月前

          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.

          • jballs@sh.itjust.worksEnglish
            5·
            6 个月前

            Ah gotcha. Yeah you should check out the books if you’re liking the show! The books go into a ton more detail and the Staircase Project is pretty cool. Seeing it on the screen is cool too, but if you really wanna nerd out I highly recommend the books.

    • frezik@midwest.socialEnglish
      13·
      6 个月前

      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.

        • frezik@midwest.socialEnglish
          7·
          6 个月前

          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.

            • frezik@midwest.socialEnglish
              9·
              6 个月前

              Implosion-type nukes are all but impossible to make go off that way. They need a whole bunch of small explosives to go off very precisely to squeeze the core in just the right way. A short circuit or a crash won’t have the necessary precision. This isn’t entirely safe, either–it can still cause a small explosion with a flash of fallout and radiation–but it’s a manageable problem.

              Gun-types (Little Boy was one) are easier to go off on accident, but the US retired its last gun-type design decades ago. I don’t think Russia used them much, either. They’re only good for smaller bombs, and their safety issues make them questionable for any use. Smaller nuclear powers aren’t bothering with them.

    • Shurimal@kbin.social
      7·
      6 个月前

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

      You know, the Kzinti lesson😉

      • Wild_Mastic@lemmy.worldEnglish
        3·
        6 个月前

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

        • MightBeAlpharius@lemmy.worldEnglish
          3·
          6 个月前

          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.

    • MonkderDritte@feddit.deEnglish
      3·
      6 个月前

      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?

      • Badabinski@kbin.social
        7·
        6 个月前

        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.

        • GBU_28@lemm.eeEnglish
          3·
          6 个月前

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

    • Evotech@lemmy.worldEnglish
      322·
      6 个月前

      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

      • wizardbeard@lemmy.dbzer0.comEnglish
        15·
        6 个月前

        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.

      • twice_twotimes@sh.itjust.worksEnglish
        12·
        6 个月前

        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.

      • surewhynotlem@lemmy.worldEnglish
        111·
        6 个月前

        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.

          • BearOfaTime@lemm.eeEnglish
            2·
            6 个月前

            No, they don’t change inside (I’ve had them). They do have a slight tint all the time though, which isn’t a big deal.

          • ferret@sh.itjust.worksEnglish
            1·
            6 个月前

            The human brain is very good at smoothing over brightness differences, even an oppressively well lit office is still typically an order of magnitude dimmer than the sun.

  • FMT99@lemmy.worldEnglish
    30·
    6 个月前

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

  • De_Narm@lemmy.worldEnglish
    211·
    6 个月前

    I think sliced bread is overrated as fuck. It used to be nice back when people couldn’t just buy knives for cheap, but nowadays it just means getting stale bread faster.

    • tiredofsametab@kbin.run
      171·
      6 个月前

      For some types of bread, the machine can do it much more uniformly and without crushing. This can be difficult for humans.

    • biddy@feddit.nlEnglish
      41·
      6 个月前

      But sliced bread has become something else that doesn’t exist with loaves. You can’t buy an unsliced loaf of ultra-processed white bread.

      • De_Narm@lemmy.worldEnglish
        8·
        6 个月前

        You can get a wide variety of both sliced and unsliced loaves in pretty much every supermarket in my area. The ultra-processed american type bread is something else entirely and it’s also a bad idea too, like pretty much all ultra-processed foods. Can that stuff even get stale? I remember it staying exactly the same up until it grows mold.

    • deegeese@sopuli.xyzEnglish
      1·
      6 个月前

      For pan loaves, people store it in a plastic bag to keep the crust soft.

      Pan loaves should be presliced, stone baked loaves with thick crust should not.

    • BearOfaTime@lemm.eeEnglish
      142·
      6 个月前

      Transitions are game changing. Sounds like someone who doesn’t wear glasses all the time. I even had transition sunglasses before I needed glasses - got tired of taking them off going in/out all day.

      Not sure who created this (I kkow, XKCD), but it’s mediocre.

      Double-ended extension cords belongs in the top left right corner. Sounds bad and is bad.

      • AdrianTheFrog@lemmy.worldEnglish
        111·
        6 个月前

        Double-ended extension cords belongs in the top left right corner. Sounds bad and is bad.

        Remember, you’re probably more technical than the average person. Double ended extension chords sound fine if you haven’t heard of them before until you think about it for five seconds.

      • Encrypt-Keeper@lemmy.worldEnglish
        8·
        6 个月前

        I’ve worn glasses my entire adult life and I had to get rid of them because being half blind every time I transition from outside to inside was interfering with my job.

        • spikespaz@programming.devEnglish
          2·
          6 个月前

          This. I worked in a hardware store as a floater (I’m good at things, they ask me to do random) and often found myself irritated at how often I need to go outside for a minute to meet a customer or something, and then come back in and all the fucking lights are off.

      • limelight79@lemm.eeEnglish
        4·
        6 个月前

        It might just be a joke. I use transitions in my cycling glasses, where I might be in shade or when it starts to get dark (but I’ll still have something protecting my eyes). I use regular sunglasses in the car, as transitions generally won’t work there.

      • Clbull@lemmy.worldEnglish
        2·
        6 个月前

        My only gripe with them is that if I spend any amount of time outdoors, even if it’s not actually sunny, my glasses quickly turn to shades.

  • yamanii@lemmy.worldEnglish
    17·
    6 个月前

    Every single glasses of mine have had transition lenses, I can’t imagine my life without them anymore.

        • Death_Equity@lemmy.worldEnglish
          2·
          6 个月前

          If you keep one eye closed and expose the other to sunlight, you can see the difference. The lenses tint a dark shade of purple. I have dark brown eyes, so you can’t really notice the difference easily. There is a purple ring that is most noticeable outside of the limbal ring. They don’t turn your eyes black like you had the tint of sunglasses or transitions glasses, which would be cool.

          I would imagine someone with lighter color eyes, like really light blue, would have a very noticeable difference.

          Something I did notice as the wearer is when the lenses are tinted there is like a contrast filter on your vision so colors look better.

        • Death_Equity@lemmy.worldEnglish
          1·
          6 个月前

          They kind of released under the radar because a comedy skit about them came out and gaslighted people into believing they were not a real thing.

          I only found them because I went to order contacts and saw the product category.

          They aren’t as good as sunglasses(but are really awesome) and they don’t work much in the car so you will still want sunglasses.

    • Lux@lemmy.blahaj.zoneEnglish
      22·
      6 个月前

      Diverging diamond interchanges are a type of road intersection that appears very chaotic from the outside, but are actually pretty simple and safe to navigate

      • eksb@programming.devEnglish
        91·
        6 个月前

        Diverging diamonds are great if your only consideration is car throughput.

        If you are considering people walking or riding bicycles, they are shit.

        • Lux@lemmy.blahaj.zoneEnglish
          1·
          6 个月前

          I hadn’t considered that. I was still pretty car-brained when i watched the cgp grey video on them, but now that you mention it, i definitely agree

          • eksb@programming.devEnglish
            5·
            6 个月前

            This is expensive to address because you have to separate cyclists out to the right before the right car lane splits for right turns before the crossover. And then you have to build a bridge or tunnel for cyclists and pedestrians. On each side.

            Really, any road busy enough to justify a diverging diamond probably already needed separated bike lanes. But in America (motto: “If you aren’t in a car, you don’t matter”), there almost certainly was not any cycling infrastructure there before.

            There is one of these near me. Their solution for pedestrians is to make them cross the high speed outer lanes four times (where drivers are encouraged to not slow down). Their solution for cyclists is take the lane and pray or get off and do what the pedestrians have to do.

            Edited for clarity: pedestrians cross four times, not drivers are encouraged to not slow down four times.

              • eksb@programming.devEnglish
                2·
                6 个月前

                To be clear, it is four times that pedestrians have to cross, not four times that drivers are encouraged to not slow down. Drivers are not explicitly encouraged to not slow down, but the point of the diverging diamond is to make drivers not have to slow down.

        • Oinks@lemmy.blahaj.zoneEnglish
          1·
          6 个月前

          It doesn’t help that US diverging diamonds seem to insist on having pedestrians walk through the median.

          But honestly all interchanges are varying degrees of horrible and if you want your city to be bearable to navigate as a pedestrian/cyclist you just really don’t want to do urban highways, or roads above a certain size in general.

      • Jojo, Lady of the West@lemmy.blahaj.zoneEnglish
        7·
        6 个月前

        Significantly safer to navigate in practice than traditional intersections, and very straightforward to navigate, if not quite as easy as a normal intersection you’ve seen all your life.

        • waz@feddit.ukEnglish
          4·
          6 个月前

          Never heard of or seen that, but it makes me think of the ‘magic roundabout’ concept

        • Badabinski@kbin.social
          5·
          6 个月前

          There are many of these where I live. The lights are usually timed so that you just go straight through without having to stop. They’re much better than the traditional intersections that came before.

          I will absolutely concede that they’re shitty for pedestrians or cyclists, however.

          • BearOfaTime@lemm.eeEnglish
            1·
            6 个月前

            The ones I’ve used time the pedestrian lights with the traffic, so it’s safer for them. Still tricky for peds going across turn lanes.

  • UnderpantsWeevil@lemmy.worldEnglish
    12·
    6 个月前

    One of the cooler parts of Three Body Problem was when they attempted the Orion Project to accelerate a probe to 1% of light speed.