Codraroll

Meanwhile, the ghost of SN4: "Don't listen to them! You might even get scattered in more directions than me!"

Isn't she a bit of a walking spoiler, like Sean Bean? She is the sort of actor called in when the main character does something dramatic and heartwarming and then dies. Three guesses as to how Away will end.

If you look at things in a very broad perspective, all we have is "energy transportation mechanisms". There are no such things as energy sources, after all.

I touched upon this in my post above, but I wonder if Retrograde Quarks in itself is broken. My career save doesn't seem to generate contracts for any other Station Science experiment, and I'm unable to get it registered as completed even when all the green boxes are ticked upon landing. Retrieving the spacecraft just resets the contract parameters.

I've read through the entire thread now and I still am not exactly sure what's going on. But it seems like the OP wants to use cold plasma for something, anything, and with that conclusion in mind tries to deduce a question for which it could be the answer. It's a little like me asking "could we make a useful machine out of LEGO and integrate it on the ship?" Any answers to that question is either a flat-out "no", or "Yes in theory, but it would be vastly more impractical than almost anything else". Oh, and by the way, there's a method of extracting energy from a ship in water that doesn't involve the engine: chemical decomposition of the hull itself. A hull made out of pure sodium could yield quite a bit of energy that way, even when the ship is lying quietly at anchor. You'd possibly have time to, I don't know, fry a hamburger directly on the inside of the hull before the whole ship collapsed on itself in a mess of boiling water. Hey, I didn't say it was a good idea.

Would it be polite to remind him that the Soviet, and later Russian, space programs have been trying to design a successor to the Soyuz since the 1960s? Getting from nothing to something roomier, more powerful, and cheaper than the Soyuz in ten years is certainly displaying more competence than his agency has been able to bring to the table in the entire time since Sergei Korolev died.

At this point you might as well just say the engine can be fueled using the rocks as well. Compared to the other engineering challenges you're banking on being solved here, it's not that much more difficult.

The risk of which could be significantly reduced with some plastic wrapping. Bulk bags are used to transport things like cement, grain, or other products that all become spoiled by water, all the time: https://en.wikipedia.org/wiki/Flexible_intermediate_bulk_container

This isn't the 1800s anymore with bags being loaded/unloaded by dock workers walking up and down the gangplank. Bulk material shipped in sacks tend to come in very large sacks to be moved by crane or forklift; I think a standard one is 750 liters. Small sacks are mostly for consumer packaging. For large scale applications you wouldn't want the hassle of opening hundreds of bags per ton of product and be left with a pile of wrapping bigger than the product they contained.

Most likely we're talking about sacks of several hundred kilos, wrapped in plastic, labeled in a language nobody could read. I was taken off a Russian ship after all. You'd need a forklift to move the stuff intact, and to even wish to steal it, you'd need to know what it was and what it was good for. It would be just as reasonable to assume the sacks to contain some industrial waste product intended for a landfill somewhere. A dockworker in Beirut could easily assume "нитрат аммония" meant "contaminated sand" or "residue from plastic production" or "salt slag" or something like that. Just because it's lying around unguarded for years, doesn't mean it's attractive to steal. Precisely because it was lying around unguarded for years, any thief would likely draw the conclusion that the stuff was not worth stealing.

Yes, ammonium nitrate is the most likely explanation. It has been known since 2014 or so that a few thousand tons of it were stored in the warehouse that went up. Apparently it was taken from a confiscated Russian vessel and then kept on storage in the warehouse because there were no plants nearby that could receive it (and/or there were uncertainties about whose responsibility it was to pay for that). A source I saw in a Norwegian newspaper also mentioned that it fits the colour of the smoke cloud, but I don't know enough chemistry to verify that. 2700 tons of ammonium nitrate has a blast yield roughly equivalent to 1500 tons or 1.5 kT of TNT. That's around a tenth of the Hiroshima bomb. However, thanks to the square-cube law (the blast dissipating proportionally to the cube of the distance), its blast force at any given distance from the epicenter would be around half that of the Hiroshima bomb at the same distance. Hence why it looked like a nuclear explosion; it was essentially as big as one. Of course, nuclear weapons tend to release a lot more energy in the form of thermal radiation which then superheats the air and creates a shock wave, while this was a chemical detonation, so the blasts look a lot different in practice. A nuclear blast would have included a lot more light and heat, I think (but possibly less of a shock wave? I'm not sure). As this was a ground blast it wouldn't affect the clouds in the sky as much as an air-detonated nuke does. The clouds in the sky are very far away, after all, and there isn't enough (thermal radiation?) energy to reach that far. The cloud would be spherical because, well, when 2700 tons of ammonium nitrate explodes, it has enough force to expand equally in all the directions it pleases. Minus down, of course, because that's where the ground is. A bit of the ground tends to move out of the way too (crater), but most of the energy goes unimpeded skywards forming a sphere. And I think most of West Beirut should be pretty grateful for that silo standing there. Its great concrete structure likely helped divert some of the energy away from the city center. The downside is, of course, that 85% of Lebanon's grain reserves were located in that silo. I don't think any of it could be salvaged now. And Lebanon is in... kind of a situation ... already, so they'd really have liked to get to keep that grain. But yeah, props to the silo for taking the brunt of the blast in that direction anyway. It's likely easier to replace that grain than what would have been flattened had the silo not been there.

It looks so unreal with that big shiny metal cylinder hovering in the air, in a way big shiny metal cylinders generally don't. And then it manages to land safely too. What a moment!

Several atmospheres of hydrostatic pressure bearing on moving parts of plumbing designed for fluids to flow the other way. You need to shut the water out while also pumping super-hot exhaust gases. The thermal gradients between the sea water and the exhaust gas will do nasty stuff to the metal parts you keep between, assuming you manage to avoid a steam explosion in the process. And then there's all the radioactivity. This is almost as stupid an idea as that two-meter cylinder spacecraft with spin gravity you touted some months ago.

You'll also be taking a rocket nozzle and submerging it in salt water to a depth equal to the length of your ship. That ought to give the valve designers quite a few problems.

The losses due to imperfect efficiency tend to come in the form of waste heat, i.e. energy. So if your goal is only to release energy, the inefficiencies would be towards that goal as well, so you'd get 100% efficiency. That's why electric heaters are 100% efficient; they are all about releasing heat, which is a process that cooperates very nicely with entropy. The other way around would probably send waste heat in all directions, though. Energy-to-matter would be a very inefficient process indeed.

And now for something entirely different: Harry Potter. "Wait, this is a setting with magic," I hear you say. "What type of science could possibly be wrong here, that magic can't explain?" Well, there's one thing, which even the lore (at least if The Cursed Child is disregarded) says is too problematic for magic to meddle with: time. So, am I picking on the time travel shenanigans in the third book? No, I just re-read it, but it's not that. It's simply that the teachers don't have time for all their classes. Hogwarts has been shown to have one teacher and one classroom for every subject. Prof. McGonagall gives all the Transfiguration classes in the Transfiguration classroom. Prof. Flitwick teaches Charms in the Charms classroom. Prof. Snape teaches Potions in the Potions classroom. And so on. Divination is eventually taught by two teachers, and Herbology is spread across multiple greenhouses, but otherwise there's one teacher and one location for every class. Now, we're shown that most classes are usually taught to students of one or two houses at the time. Gryffindor tends to be paired with Slytherin for Potions, for instance, but Transfiguration is always done by Gryffindor alone. Same with Charms, if I recall correctly. The students usually have four classes per day, two before lunch and two afterwards. Each class usually has multiple lectures per week. There may be double-length classes that take up half the school day, such as Potions which usually has one double-length class per week. But Hogwarts has students spread across seven years and four houses. Some classes are taught only for a few years (such as Divination, which is only mandatory for years 3-5), but others such as History of Magic or Charms remain mandatory at least through year five. For the higher-year courses, the classes are small enough that all four houses are mixed in class (such as Prof. Slughorn's Potions class), yet the number of classes per week for a student remains the same. And that's the problem: for most subjects, the numbers don't add up. There simply isn't enough time to teach everybody. Take Transfiguration, for instance. Five years with separate classes for the four houses, plus two years with students from all houses, that's 22 classes per week, even with only one Transfiguration class per student per week. With two Transfiguration classes per week, the teacher has to be present for 44 classes. Yet the calendar only contains room for 20 classes in a week. Potions is supposed to teach all the 12 student groups for at least half a day each over a five-day week, and presumably a typical school week contains some shorter classes as well. And it's all done by one teacher. Something similar goes for Astronomy. Classes take place at midnight, yet there aren't enough midnights in a week for all the school years, unless the teacher never takes a day off and students don't have weekends off for up to two years. "But what about Time-Turners? They allow a person to be in multiple classes at the same time!" Hence the point about each class having only one classroom. Using a Time-Turner, a person may be in several different locations at the same time, but here we're explicitly told that most classes exclusively take place in one classroom, so two classes can't be taught simultaneously. Prof. Sprout's classes occur across several greenhouses, so she might be able to pull of tricks with time-turners, but that's not an option for anybody else, and apparently Time-Turners were destroyed after book 5 anyway. Only Divination and the elected subjects would realistically be able to fit into the allotted schedule. I think any reasonable teacher would complain about the workload, too. In addition to apparently teaching more than forty two-hour classes per week, Prof. McGonagall apparently assigns each of Hogwarts' hundreds of student several pages' worth of homework to write after every class, and she's the only one around to grade it. The Harry Potter series is fun to dissect like this. The books are an absolute joy to read, but as soon as you try to run the numbers on anything, they never add up. Take for instance the beginning of the school year, with the train to Hogwarts from platform 9¾ at King's Cross station. The train leaves at 11 sharp, yet the main characters always arrive only a few minutes before 11, which seems to be a common time to arrive for most people. "Most people" in this case means hundreds of students, most of whom are accompanied by their entire living family. There could be around a thousand people arriving on that platform every September 1st, and it has only one entrance, which means somebody would have to pass through the magical barrier every few seconds for hours, somehow without forming a huge crowd on the outside or attract Muggle attention. Or maybe Harry and his friends are always the only ones to arrive just in time, while it is customary to show up at an assigned time slot between 7 and 10 AM? Everything makes sense when seen through the eyes of Harry Potter, yet as soon as you start considering he's only one student among many, the given explanations for how things work quickly fall apart. J.K. Rowling has apparently admitted that math isn't her strongest suit, and I'm inclined to agree with that. Or maybe it all works because magic.

Nah, the worst that could happen is to give people a vaccine that's no good, while they behave as if it was good. "I'm vaccinated, now I can safely lick the handrails of the escalators on the Moscow metro!"

My biggest problem with Interstellar was when they went down to that planet deep in the gravity well. To paraphrase the scene: "This planet is deep within the black hole's gravity field, so an hour on the surface is like 25 years up here." "Yes, when we go there for an hour, 25 years will have passed on the ship." "25 years on the ship, that will be lonely for me. But you will only feel like you've been away for an hour." "I've also got a Master's degree in physics like the rest of you, and we've been preparing for this mission together for months now, but want to make it clear if we're on the same page here: when an hour passes on this planet's surface, 25 years will have passed elsewhere, right?" "That's right. One hour on surface, 25 years in space. Anyway, let's go down to the surface and check that beacon that has been sending signals to us for 25 years. I'm sure that means the planet is habitable, otherwise it wouldn't have sent signals for 25 years. It would have stopped broadcasting after, ah, an hour or so." (They go to the surface) "Wait, the ship is destroyed, and it happened only recently! I'd say about an hour or so! Wow, the astronaut was waiting for us for 25 years, and then disaster happened only right before we arrived!" "Wait a second ... I just realized! One hour on the surface of this planet is like 25 years outside! The ship has only been here for an hour, even though the signals it broadcast have been reaching us for 25 years! It was destroyed almost immediately upon landing!" "Wow, that's quite a revelation! Good thinking! Sadly, it was impossible for us to foresee this. None of us could ever know that when 25 years had passed on the outside, only an hour had passed on this planet. I only ever thought of it, like, the other way around. Anyway, there's a giant tsunami coming, we better go." (They go back up to the ship) "Wow, pilot, you look a lot older! What has happened, we have only been away for an hour!" "For you, it was only an hour. For me it was 25 years." "Wow, that's crazy. I didn't know! I'm completely surprised!"

I guess that depends how far underground you want to live. In the series, only the spacedocks and greenhouse domes are on the surface.

The problem with storing energy as antimatter is that you have to work very hard to contain it, and with one little screw-up you can kiss your bum goodbye. Any small containment failure will unleash enough energy to ruin the containment device, thus creating a very large containment failure and making your ship (or station, or city) a short-lived star. Antimatter storage is like storing hydrogen if hydrogen spontaneously combusted upon contact with anything including the tank it was kept in, only a million times worse because that's roughly how much more energy it releases.' In short, if you have the technology to reliably create and store a lot of antimatter, you probably have better options for your energy creation needs.

Doing this at Earth orbit because that's the easiest figure to work with. Assume sunlight: 1kW/m2 (good enough for an approximation) Required energy: 1000 *c2 Joules (per @Kerbart's post). That's c2 kilowatt-seconds. And you're getting one kilowatt-second per second per square meter of solar panel. c2 = 9 * 1016. A very big number. But of course, it represents kilowatts multiplied by seconds. If you're not in a hurry, you can have a small energy source and take a lot of seconds. Assume you want the tanking to be done in a year. Since we're already playing fast and loose with the accuracy of numbers here, let's approximate a year to 10 000 seconds. Or 104 seconds. This means you need your solar array to be 9*1012 m2. Let's round that up to 1013 m2, to give room for some gaps between the panels. 1013 m2 is ... kinda big. We can knock off a few zeroes of the figure by converting to square kilometers instead. 106 m2 to one km2, that gives ... 107 km2. Ten million square kilometers (well, nine million, if we revert that rounding up we did earlier). That's roughly the size of Canada. Realistically, to account for various losses and inefficiencies, you could need ten times that. Get the towel ready. Creating "a few tons" of antimatter requires "a few times" more energy than creating one ton of matter. You seem strangely fixated on using antimatter as an energy source, but it's a very dead end. Creating it takes, at the very best, as much energy as you're getting out of it, and you're going to need a whole lot of energy to store it without blowing everything to bits. And of course, after pouring those 1017 Joules into creating one ton of hydrogen, assuming you bring your oxygen and burn it, you'll get ... approximately 1011 Joules of energy out of it, if my math is correct. A year of tanking for a total fuel efficiency of one ten-thousandth of a percent. "Folly" doesn't even begin to cover it.

Aha. In the book you never see what caused it to go down or learn if it was intentionally targeted towards the domes. I think they mention rumours about somebody targeting mirror arrays, but not who does it or why (because both factions wants Ganymede to keep producing food, and its infrastructure is largely left intact after that one crash). The scene with the impact in question begins with the two lab technicians packing up their stuff after hearing an array is coming down in their direction. It could have been falling for minutes or even hours already by then.

Not sure if it's much of a spoiler, but I'll hide it anyway to be on the safe side:

Maybe, but I think a legitimate question wouldn't bungle up the thread title that much, and why is "hide answer choices" there?

Wouldn't that be "Metallic Explodium"? Or at least "Metallic liquid fuel"? But yeah, I agree there. If the problem with metallic hydrogen is that hydrogen can't be metallic, it shouldn't be a problem to come up with a similar substance that can be metallic and use that one instead. Take Minmus, for instance. Real-world physics wouldn't allow it to exist for very long if it was made of ice (at the very least, its mountains should come down pretty quickly), but as far as I can tell the official line is that it's made of a substance that just really looks like mint ice cream without actually being it (to everyone's great disappointment). Who knows what properties almost-mint-ice-cream has. Apart from phenomenal density, that is.