Having finished out the Amazon Prime series "The Expanse" I'm now working my way through the novels and I keep coming up against a problem with with railguns. Specifically, the way that railguns are used in The Expanse doesn't mesh well with the way they're portrayed.

First, some background. Ships in The Expanse are generally unarmored. There are a bunch of reasons for this but the short version is "most things that can hit you in space will kill you anyway" and armor adds mass which makes every manuver more expensive in terms of reaction mass. So no one has armor. This is important because it means that ships in the Expanse can get ripped up by something as mundane as a stray bullet from a Point Defense Cannon (PDC). PDCs are... well, they're guns. Regular guns which are flinging around much less mass and at much lower velocities than railguns.

Thus, ships in the Expanse are equipped to handle impacts but nothing much bigger than a sand-grain moving at a few km/s.

When we're introduced to rail-guns in the series we're given to understand that they use magnetic acceleration to chuck a 5kg chunk of tungsten and/or uranium at a target at an "appreciable percentage of C." That's much faster than a bullet or any micrometeors ships are likely to encounter. Even 1% of C is ~3,000 km/s.

5 kg of Tungsten is less than you think. Some back of the envelope math suggests that's about cube about 2.6 inches on a side... which is not big. That works out to an incredible energy density which would make a lot of sense if railguns were routinely being fired at planets or asteroids but, since they seem to mainly target ships, the vast, vast majority of the energy that goes into flinging that slug at its target is going to carry through to the other side of the ship.

All total we're talking about 488.5 million Newtons of force for 1% of the speed of light. Helpfully, this scales roughly lineraly so long as we don't get too close to C and induce relativistic mass issues, so 10% of C is 4.8 billion Newtons and so on. So, that railgun slug is carrying a lot of energy. At 1% of C it represents 22.5 trillion joules of kinetic energy. Written out long-ways so we can appreciate all those zeros it's 22,500,000,000,000 J. At 10%, we're talking 2.25 quadrillion joules. To give some sense of scale, that means that, at 1% of C, three rail-gun slugs are delivering about as much energy as the bomb that destroyed Hiroshima in 1945. At 10% of C one round carries about 537 kilotons, or about the yield of a modern, city-busting hydrogen bomb.

Those are absolutely titanic amounts of energy but, realistically, they'll never deliver that much power to a target. After all, a railgun round can only push on its target as hard as the target can push back on it. If the round just punches through the entire ship like it's made of paper, most of the energy stays in the railgun slug as it exits the other side of the ship and you get a neat hole rather than a gigantic flash as trillions of joules of kinetic energy turn into heat.

And obviously, if we're trying to kill things, we want the latter. The solution to this problem is fairly obvious: you need fragmentation. While it's great to have a tungsten cube all tightly packed together as you accelerate it, if you're shooting at a ship, you want a fairly diffuse impact, especially if we're talking about a 10% of C railgun slug. There aren't a lot of things out there in the solar system which can take 500 kilotons of hate and come out the other side in one piece. Moreover, at the distances at which a rail-gun fight happens, that spread would help ensure that you hit your target. Like a shotgun loaded with birdshot, a fragmenting railgun round would provide a cone of impact rather than a line, making dodges less effective.

And, as I mentioned earlier, you don't need a ton of mass to make this work. If a PDC round can go straight through a military craft then we can safely assume that a chunk of tungsten with the same kinetic energy will do the same thing. PDCs look rather a lot like the close in weapons systems in use on many naval ships today so we'll use those as a guide. The 20mm cannon on a Phallanx CWIS tosses out rounds at about 1,035 m/s. Those rounds weigh about 100 g (0.1 kg) which gives them a kinetic energy at the muzzle of 53,422 J.

So, if we could predictably shatter our 1% C railgun round into 421,136 pieces, each would have about the same kinetic energy as a PDC round and be able to hole the ship. At 10% C we could go even smaller and do the same thing with upwards of 40 million shards. 1% is plenty though. Each hull-penetrating piece of our original 5 kg bullet needs only weigh about 1/100th of a gram, which works out to being about 1/100th of the size of a grain of sand.

Put another way, if the fragmentation of a rail round could be precisely controlled, a target ship would experience hundreds of thousands of individual hull breaches with the mean distance between them determined only by the geometry of the ship and the angle of the attack. The result of this would be either the delivery of a titanic amount of energy to the ship itself as the armor attempts to absorb the impact or, if no armor is present (as seems to be the case in the Expanse) the rapid conversion of the interior of the ship to a thin soup.

This, however, seems never to happen in the series and what leaves me scratching my head. As a book and TV series, The Expanse does an otherwise bang-up job with hard science fiction. Most things in universe make sense. This, however, does not. We have take as a given that the materials science technology exists to allow the mounting and firing of a railgun on a ship -- there are a lot of challenges there -- but the straight-line-of-fire use of them is a rare problem with the world-building.

Any fans have any suggestions to help me square this circle?

I thought it was pretty good, it's just that the whole season seemed a little off. I feel like the actual overarching plot of the season didn't even start until over halfway through.
Still enjoyed it overall and can't wait for the next season.

Some very mild spoilers for The Mandalorian

I have not been really following Star Wars since Disney took over, I think I saw one or two of the new sequels (they were forgetable) and I saw Rouge One (It's great, would even call it the most Star Wars Star Wars movie)

I had some time last weeks and I saw Andor and I was just stunned. Good to great actors, great worldbuilding, a bit on the nose but still engaging social critic and themes, an interesting and intense story based in gritty realism while still being very Star Wars. I think everybody who likes science fiction and/or spythrillers should watch it.
So I was like: oooooh so they finally found a way to do new and interesting stuff with the Galaxy far far away. Everybody says nice things about the Mandalorian, let's check that one out. It got 92% on RT so I'm shure it's nice....

I seem to hate it and it makes me angry that it turned out the way it did, because i still like a lot about it. It makes me sad that they botched it so badly.
Maybe having a main character whitout a face is not helping? so i need a robot to tell me what Mando is feeling? Pedro Pascal is actually doing an incredible job working with body language and voice, but I don't think it's enough to actually be able to salvage this dumpsterfire of an realisation. Or maybe they should have kept with Mando being an unrelatable asshole, and not make him a disney daddy?
And then they still show his face.... in the most anticlimactic way ever... why? just why do that? It makes me angry just thinking about it, how can you fuck that up so badly, that could be a series defining payoff, but no! They just waste it in the most boring and unconcequencial way ever.

Then there is the Rule of Cool or Why is Everybody a Badass?. Mando is cool, i get it. He has an amazing Look (obviously the helmet is crazy good). He has very interesting and powerful weapons. But then I he still gets mostly his as kicked by nearly everything and everybody all the time?? I mean why do you tell me with every character and all his design that he is a force of nature and than he gets his ass kicked by a fucking dinohead on two legs that looks like a joke and is a joke (I dont actually mind that, i like the design and the joke) I just makes no sense to me.
Nearly everybody else looks cool and is presented as a badass as well, there is just to much of it. there are no weak people, there are no hurt people, there are just badasses and cannonfodder.

Then there is the storytelling... It ranges from quite ok to fucking horrible. I mean, who thought it is a good Idea to NOT cut the motherfucking prisonship episode? It's some of the worst TV i saw in a long while. It does nothing for the overall story. it does nothing for the characters. It does nothing for the viewer. It does nothing for nobody. Its just full of bad acting, bad direction, bad and lazy set design, bad editing, bad jokes, and the worst storytelling. why did they leave that piece of shit in there? the whole series is worse for it. It makes me angry.

So I finally checked the wikipedia page and I understood. Jon Favreau.... Jon Favreau!!! I mean not all of his work is that bad. I liked Iron man and Chef, and I love Cowboys and Aliens (really! it's so bad it's good, but you can not expect differently with that name) I hated his Lion King.

I don't now where I'm going with this. I think I just needed to share my feelings about it. It's just so full of potential, there is so much they could have done with it. they could have explored so many themes and share so much lore... but they just fucked it up and everybody seems to like it, i dont get it.

/rant

so are the other Star Wars shows worth a watch?

So I used to be quite a fan of Dr. Who, but life got in the way shortly after Smith ended his run. Hearing about Tennant's return, I'd love to catch up, but also don't have time to watch filler.

Do any tilderinos have some advice for an abridged viewing that minimizes the episodic filler without missing too much of the main plot?

This post will include spoilers from all first 3 episodes.

Arcane came out on Netflix a few hours ago. I binged the first 3 episodes. It easily exceeded my expectations. I played the game for many years and I can't believe how they managed to bring those characters to life. Now I'm really hoping that they develop the Runeterra universe more like Disney is doing with Star Wars.

The character that teleports Jayce and his mom is called Ryze (Maybe I'm wrong and it's not him?). He is considered the main protagonist of Runeterra. Some other characters that I've spotted include Vi, Jinx, Ekko, Singed, Jayce, Viktor, Twitch(?), Caitlyn, Heimerdinger, Warwick(?).

One of my favorite thing about League of Legends is it's art department. This show has some great music and the video is like a painting. I really like how bright the images were, especially during that first robbery scene. The view on the cities was breathtaking. They went for a really stylized look and I really like what it does to the effects like lightning or smoke. Sometimes they draw extra lines around the objects or characters' silhouettes to make them stand out.

The story itself was good too. I was pretty engaged with all the characters. Many of them we've never heard about before in the lore. There's a meme in the community about how characters have a "dark and secret past". It's nice to finally get rid of the secret part of the quote. Seeing it animated was pretty emotional they really didn't pull any punches :D. It gives so much context for why those characters behave the way they do.

It's definitely a show I'll have to rewatch multiple times to catch all the easter eggs. For example Vi wears these goggles in the game.

I'd love to hear what people unfamiliar with the game think about this series so far. Also for those that didn't know, this series will end up being around 6 hours long once it's fully out. The second act will launch on November 13, and the third act will release on November 20.

btw for those that want to read more about this universe, there's a map here. The story is happening in Piltover & Zaun. They publish a lot of short stories here.

Edit: Arcane showrunner interview: how League Of Legends broke the video game movie curse