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I think you put your finger on it within the first two sentences. Everything else is going to be situational, and highly dependent on available technology. Again, as you said yourself, having a crew in the loop for decision making is an advantage - unless you have a robo-mind capable of thinking like a human. Alternatively, FTL comms could remove the need to have a crew onboard for decision making purposes. Take maintenance for example? Is it easier to have repairable systems or redundant systems if you want reliability? Is there any reason why those repairs can't be done by robot? Even present day space vessels have robots to help with maintenance - see DEXTRE on the ISS for example. Can the repairs be done 'in the field' at all? Fixing a busted nuclear reactor might be difficult, replacing a worn thruster nozzle less so - assuming that the nozzle was designed to be replaceable. Also, life support systems and crew compartments have a fairly substantial mass penalty. If you do away with those, is your warship light enough that you can give it acceptable performance with a simpler, more reliable propulsion system? For that matter, is a repairable vessel worth the extra cost and complexity? Might it be more practical to have a swarm of drone vessels and just accept that you're going to lose some over time due to lack of maintenance? What weapons are your ships using and defending against? How long do you expect the ship to need to last between engagements? Is battle damage likely to be survivable or not? If a single engagement is likely to damage a warship beyond repair then a) there may not be much point worrying about maintenance and b) you're probably not going to put a crew on it. Don't get me wrong - you can absolutely have a setting with crewed, repairable warships if you like but it's difficult to say what the advantages or disadvantages of having a crew are without knowing more about the available technology in that setting - and the rest of the setting for that matter. There are various 'soft' reasons for crewed warships that have been explored fairly thoroughly in science fiction. Are you writing in a setting where AI has been banned, such that any computer more advanced than a desk calculator is a dangerous heresy? Does your setting have a tradition of honourable combat aboard crewed warships? (True warriors don't send machines to fight for them, even if the machines could probably do a better job.) Or maybe you're leaning Starship Trooper-wards, and service aboard a warship is a necessary part of winning political privilege and influence back home, assuming that you survive your tour of duty.

Pick up rock. Sneak up behind enemy combatant. As per Mr R Heinlein, this may be facilitated if the enemy mudfoot is loaded down with gear and too busy reading a vernier to notice you. Bash them over the head with rock. Steal their weapons and ammunition to use against them. Stretch goal - reverse engineer magic boom bullets for own use. Edit. More seriously, how do modern militaries deal with grenades, mortars, tanks, and all the other sundry nastiness that lie between ‘small arms fire’ and ‘tactical nuke’? Reading up on that might be a good place to start. Edit the 2nd. If you want a science fiction take on this, what you’re describing sounds like a standard Bolter from Warhammer 40K, albeit one that doesn’t require the strength of a genetically enhanced supersoldier to use. Unsure if you’ll find any way of countering Bolters other than ‘throw more bodies at the problem’ or ‘deploy space magic’, but it might be worth a look.

@Vl3d Cheers for the examples. Definitely an 'eye of the reader' situation here, I think. To me, those examples were mostly callbacks to the old 'dumb kerbals' (OK, lets be nice about this 'cheerfully haphazard kerbals with ramshackle technology') and 'parts lying by the side of the road' memes from the early versions of the game, with a sprinkling of pop-culture references in there too. And I think even those memes largely came from the playerbase, or from the "It's hardly rocket science" comics put out by one of the early devs (apologies - I don't recall their name). If you see them differently, that's cool, but they weren't especially edgy or gutsy to me.

As I said, I haven't played the game so obviously can't speak to the writing quality, but I have to admit that that mostly sounds pretty good to me. I could go with feel good vibes from diverse green aliens with emotions and helpful personalities, and I suspect 'cute and silly' is likely in the eye of the reader. That's all probably helped by the fact that I never really saw the KSP1 kerbals as stupid crash-puppets (and have probably spent more time writing kerbal headcanon than actually playing the game - see signature file ), but YMMV. Genuinely curious about the astronaut humor from KSP1 and Squad kerbals talking back with scientist and astronaut tongue-in-cheek jokes though, because that's not what I remember at all. Again, probably in the eye of the reader, but if you could sling out a couple of examples, I'd be interested in seeing them.

To me, the soul of KSP1 was three kerbals (probably but not necessarily drawn from Jeb, Bill, Bob, and Val) in a capsule orbiting the Mun, with ear to ear grins on their faces. To a lesser extent, it was also about the 'parts found by the side of the road' attitude, which always gave me an early rocketry club vibe. Basically, imagine the British Interplanetary Society and their Soviet or German counterparts, but with the actual resources to put their ideas into practice. Small green aliens heading into the unknown for no better reason than it seemed like a fun thing to do. The actual 'parts by the side of the road' meme though, got rather overdone in my opinion, as did the junkyard aesthetic. Aesthetically, I imagined early Kerbal technology as being similar to early Soviet technology. Rugged, not too pretty, but by thunder it got the job done. If you're curious, go do a web search for the "Cosmonauts: Birth of the Space Age" exhibition at the London Science Museum, and check out some of those images, particularly of the early Soviet satellites. I'm quite positive that they weren't cobbled together from whatever the Soviets had lying around, but they sure do look like they could have been. I found the KSP humour and 'dumb kerbals' memes to be mostly ignorable at best or actively irritating at worst. The short descriptions veered all over the place from 'played straight' to 'humour that didn't quite land' to 'WTAF'. I'm talking about sensors powered by black magic and fuel tanks that were allegedly even more adorable than their larger counterparts and should be handled stoically and with care. I haven't played KSP2 so I don't know what its overall vibe is, but there's an awful lot of memetic fandom baggage from KSP1 that I wouldn't miss in the slightest.

Each to their own, but I disagree with this. Trial and error is boring. If you want to gatekeep a quality of life feature, gatekeep it behind something I can plan and execute, like putting something in a high orbit around Eve or Laythe to measure the extent and density of its atmosphere and give me some data (or better, a visual aerobraking guide) to help me plan a landing mission. Please don't make me have to do a bunch of save scumming before my first landing, after which I'm deemed to have 'learned' how to aerobrake and can get the nice visual guide. Because I promise you that I'm not learning about heat flux or whatever, I'm just grinding through a bit of boring gameplay to avoid having to do it again. More generally, I'm not really onboard with the idea that KSP2 has to be a learning experience and the notion that the players can start with in-game tools for these skills (like calculating delta-V requirements) but just have to git gud at these skills (like aerobraking) before they're deemed worthy of unlocking an in-game tool. I say this as someone who a) doesn't have KSP2 so doesn't really have a stake in this discussion, and b) who found that the best bit of KSP1 was the learning to play part and that once I'd done that, the actual game was pretty thin. But just because I liked it, that doesn't mean that everyone should. And even then, the 'learning to play' bit was mostly about how I stopped fiddling around and learned to love the navball to do things like docking or powered landings.

I wondered when those were going to turn up. And yes, you probably would, which is exactly why I mentioned needing rapid attitude changes, say for a Moon lander.

I think there's no distinction between a large creature compressing itself to become small and dense, and a dense creature spreading itself out to become thin. I think this website might be helpful for calculating how much bioballoon you need to lift a given weight - actual calculator is at the bottom of the page. However, if you want some ballpark figures, then assuming you're in Earth's atmosphere and your hot air is heated to 100 o C, it requires about 4 cubic metres of hot air to lift a kilogram of mass. Going the other way, it takes about 0.1 cubic metres, or 100 litres of hot air to lift 26g of mass - which is the mass of a slightly larger than average, common frog. A 50kg human would therefore require 200 cubic metres of hot air. Assuming that hot air is contained within a spherical bag, that bag is going to have a 3.5 meter radius, give or take and a surface area of 150 square meters, give or take. I think that's a lot of membrane to manage. I think that any worries about having the organs work OK are moot because if you want to fly like a hot air balloon, then you're going to be shaped like a hot air balloon, with all your organs, limbs etc. in as light a package as you can manage, attached to a large, thin, gasbag. At most that gasbag is going to have blood vessels and perhaps very fine tendons running through it to assist with repacking, but I honestly can't imagine it containing more complex organs. I think the idea of having complex organs which can be stretched over a 3.5 meter sphere, and then squashed together into a jello-like mass, which then semi-hardens is... implausible. I think that a protein heavy diet is possible, but a balanced diet consisting of some protein, plus a lot of energy dense nutrients such as fats or sugars would work equally well. I think that you need to be less concerned about the laws of physics and more concerned with anatomy. TL:DR, I don't think this critter is going to work as a shapeshifter, unless you count caterpillars as shapeshifters because they turn into butterflies.

I did a quick search for 'Shuttle RCS firing', since the Shuttle is one of the heavier spacecraft launched to date, so I figured that its RCS would be correspondingly more powerful. I found this image which isn't exactly plumes of fire territory but it's a bit more than a puff of white vapour. Also its from NASASpaceFlight, so should be legit. Unless you absolutely need to make rapid attitude changes (say, for a Moon lander or something), I don't think there's any particular advantage in being able to do so, especially for heavy spacecraft. Faster attitude changes require more powerful RCS which typically means carrying more propellant for that RCS, particularly since you need propellant to both start and stop your maneuver.

Oh sure. Give me a trolley problem with my friends and family on one line and Mr Flopsy the fluffy bunny on the other, and it’s goodnight Mr Flopsy, however much I like fluffy bunnies - and I do. Then again (and hell I may as well go full Godwin on this), give me a trolley problem where the upper echelons of That Party are stacked up against Mr Flopsy, then sorry (not sorry) Mr H, I choose the fluffy bunnies. It’s just that ‘look at superior us with our higher intelligence and higher morality’ attitude that gets my goat. Sure, that’s what we aspire to and on a good day most of us might live up to it. On a regular day though, ‘higher morality’ can be alarmingly expedient and ‘higher intelligence’ is a poor second cousin to ‘following my gut’. That includes me by the way. Going all mushy over a picture of Mr Flopsy ain’t going to stop me tucking into a rabbit stew. Let’s not even get into the question of ‘what is morality’ because we’ve been arguing about that pretty much since we came down from the trees. TL: DR (and I’m probably butchering this quote), a person is smart but people are dumb, panicky animals.

As the pandemic and assorted other global challenges are proving - nor do humans. Ahh yes. That great human morality that leads us to slaughter ourselves wholesale, that leads us to treat The Others (insert others of choice here) as inferior to ourselves, and that leads us to actively connive in the extinction of other species for profit. And our much vaunted intelligence which appears to be rather adept at dreaming up new and interesting ways of causing our own extinction rather than avoiding it. Frankly, I'm betting on the animals. They don't tend to foul their own nests, when they fight (as opposed to hunting for food) more often than not, displays of submission are respected, which avoids the death of either combatant, and, in the words of the great philospher Ellen Ripley, you never see them screw each over for a goddamn percentage. You are placing humans on a lofty and unwarranted pedestal.

The grouchy chemist in me isn’t a big fan of unobtainium in any kind of science fiction. Room temperature superconducting alloy? Sure, why not. We have no idea what that alloy would be, but hey - science fiction. Superconducting elements? Shove them in the same dumpster as any other ‘elements hitherto unknown to science’. We know what the naturally occurring elements are, and for the extreme end of the Periodic Table we can still extrapolate properties with reasonable confidence (hi Mendeleev). Besides, any element at that end of the Table tends to have a half life measured in milliseconds. There are so-called islands of stability (don’t recall if we’ve actually reached them yet) where certain Superheavy isotopes are expected to be more stable on theoretical grounds but that just means a half life of minutes to days, rather than anything useful. That’s assuming the theory is correct - as far as I know, islands of stability haven’t been experimentally verified.

It pains me to admit that I don’t remember ‘Launch Clamps Aweigh’ Not to worry. It’s two hours to lights out, I have 25% charge on my phone, a KSP forum to search, it’s dark, and I’m wearing sunglasses have a cat on my lap. Hit it.

Don’t stop believing… Kerbfleet launching… *shredddd!* Still remember that strip - probably because of the music.

Unless a state actor decides to get involved with this, I would have thought that the selling part almost goes without saying? I can't see SpaceX for example (not ragging on them specifically for this, but they seem like the only outfit that will be capable of shipping people to Mars in the near future) letting people book flights on their spacecraft free of charge out of the goodness of their hearts. Not outside of marketing stunts anyway. I agree with your expert pioneers comment and for sure they'll need to be smart and skilled. However, I don't think we can assume that they'll necessarily be smart and skilled at aerospace engineering, since it'll presumably take a lot of specialists in different fields to get an off-world colony going. I'm also still reminded of the Apollo astronauts. Very smart, very skilled - in most cases at aeropsace engineering - and they were still only trained to be experts on particular parts of their spacecraft, rather than the whole vehicle. TL: DR, I honestly don't know how much information one would need to do a decent assessment on a spacecraft design, and whether that would be possible even for a smart, skilled, expert pioneer, even assuming that the company building and/or operating the spacecraft was inclined to give them that information. But I'm spinning my wheels here. I'll sign off by hoping that private spaceflight will be the domain of companies that do it right. That's not saying that I expect them to be omnipotent and magically account for all possible risks before putting people on their spacecraft, but that I hope that if and when accidents happen (which they almost certainly will), they'll only be because of the "unknown unknowns" in the situation, to paraphrase Secretary Rumsfeld. Unfortunately, I think that OceanGate is the more likely model. With lots of hiding behind waivers. Humans gonna human, and humans have been screwing each other over for a profit since... well probably since the notion of 'profit' was conceived. Even - in fact especially - in a field like medicine, where one would kinda hope that anyone with half a scruple of scruples or humanity, would not sell their fellow humans any old crap (sometimes, quite literally, I'm sure) to ingest, for the sake of making a quick monetary unit or two. Sadly, I don't see why space travel should be, or will be, an exception.

Some clarity required here, I think, because I’m not sure how well (or even if) I explained myself. When I say’rushing’, I mean having the procedures in place to do something safely but having a workplace culture where the procedures aren’t followed because getting the job done now is more important than getting it done correctly. In Pharma terms, it’s being unsure whether a batch was manufactured properly but letting it slide because it’ll probably be OK, and ditching this batch and starting again isn’t an option because you’ll be fired. Or it’s falsifying QC measurements either because the measurements weren’t done at all or because they were done but gave the unacceptable answer. Corner cutting in other words. Also, I’m quoting this because it gets to the heart of what I’m trying to get across. If the passengers getting onto that submarine knew about all the crappy things at once then - well, I think that calling them morons is harsh, but yes, they knew what they were getting into. It’s the situation where they don’t know what they’re getting into that I’m concerned about. They don’t know about the crappy management and oversight (because how could they?). They don’t know enough about submarines to be able to judge whether it’s a crappy design - and if they ask about it because they’ve seen stories in the media - then they’re told all about this wonderful safety system that monitors the hull and sounds the alert if it becomes unsafe. Or they’re fed a lot of impressive sounding but meaningless information about the window thickness. Both of which are which are also a load of crap - but how is the passenger supposed to know that? Edit. Re the above, and more importantly, expecting the customer to know whether the design was bad shouldn’t absolve the company concerned from putting customers on a bad design. Because if the customer is supposed to be able to tell whether the design is bad (to make a judgement call as to the risk involved in getting on board), then for damn sure the company should be able to tell too.

Disagree. The people at the sharp end of this endeavour are the people flying the spacecraft who, increasingly, will have to take it on trust that the people building the spacecraft have done a thorough job. Even Apollo style astronauts, who knew every relay, valve, pipe, and switch of their particular part of the spacecraft, didn’t have that in-depth knowledge of the rest of the spacecraft, let alone the booster. The people on the sharp end won’t have any choice in the matter of cutting corners or not. Hell, the first time they’ll find out about it is when something goes wrong mid-flight. And corners will be cut because that’s what private industry does. It cuts, and it cuts, in the name of doing things more efficiently, which usually means doing things cheaply. Sometimes that works. Sometimes it doesn’t, but at least the people involved weren’t being criminally reckless or negligent. Sometimes the people involved just plain don’t care that they’re endangering people (see the various FDA inspection horror stories from the pharmaceutical genetics industry). Sometimes the people involved are fixated on disruption and established industry practices are nothing to do with safety and all about ‘incumbents protecting their market’ (see a certain recent submersible tragedy). The folks flying out to any off-world colonies are going to be shouldering enough risk as it is. It would be nice to think that they weren’t taking on any extra risk because the spacecraft they’re flying was built by a company helmed by a ‘disruptor’ CEO with their head up their backside, or a Go Fever CEO fixated on pointless deadlines over safety. Or, more briefly: I am OK with people choosing to risk gasping their last on a godforsaken ball of rock if that’s what they want to do. I am not OK with that happening because their spacesuit is a collection of single points of failure in a beta-cloth shell because building a proper one wasn’t profitable enough for the company involved, or would have taken too long. And in the vast majority of cases, the person wearing the suit won’t be able to tell either way until it’s too late.

I’m sorry but I really don’t agree with this. OK, I might agree (with heavy reservations) with that last part, but not the part in which off world colonies have to happen or we die. The only scenario in which an off-world colony is absolutely essential to our survival as a species, is one which makes the Earth utterly uninhabitable to human beings, whilst somehow leaving the off-world colony intact. I can think of vanishingly few naturally occurring ways for that to happen. Even if we got clobbered by a second Dinosaur Killer sized rock, I believe we would survive. It wouldn’t be pleasant, there would be a lot less of us afterwards, but I don’t believe we would go extinct. I can think of various more or less apocalyptic ways in which we could try and wipe ourselves out but even then actually doing it is a tall order. But assuming that we can find a scenario that does wipe out humanity on Earth, I believe the more rational response to risk mitigation is to find a way to stop the scenario from happening rather than relying on an off-world colony as a lifeboat. An off-world colony might (heavy emphasis on the ‘might’ for at least the reason that @mikegarrison gave) provide some additional mitigation, but I don’t believe they provide sufficient extra mitigation to make them inevitable in that ‘if we don’t do this we die’ sense. Besides, outside of terraforming, an off-world colony is an inherently less stable situation than any settlement on Earth, simply because it would be an entirely artificial habitat that requires constant, active maintenance and, more importantly requires that its inhabitants not go out of their way to break it, start wars in it, or whatever. And, historically, indefinite periods of mutual cooperation have not been humanity’s strong suit. In practice, if humanity-on-Earth gets wiped out, I would give off-world humanity about a century at most. The fact that the colony is then in a precarious situation might provide a temporary brake on a war breaking out, but the very precariousness of the situation would make the impact of a war far more severe.

Couldn't ask the dinosaurs but I did ask a little birdie - is that close enough? They thought that getting off this rock and going anywhere else in the solar system sounded like a terrible idea compared to staying put in this nice warm environment with breathable air and food for the taking. They did reckon that detecting and deflecting any space rocks that threatened to mess things up, would be a good plan, and conceded that a big rocket could probably help with that. Maybe I just spoke to a particularly short-sighted birdie but I'm inclined to agree.

Tell that first part to the employees of that private enterprise. Even, taking that article with a large pinch of salt, it's still pretty damning. And I suspect that passing the mantle to other companies isn't a long term solution to the problem. I'm not going to rehash what I've already said on the 'A City on Mars' thread on these forums, and this is probably skirting too close to politics anyway but my answer to @SunlitZelkova's question is: Musk is insane because he's charging headlong towards a goal of dubious value without caring who gets chewed up and spat out in the process. And now, I'll shut up in the interests of keeping this thread open.

And respectfully, I think you're overplaying the volunteer thing. Sure, space colonisation will be risky and dangerous. No way around that, and I agree that people should be able to choose the level of risk they're OK with. But the way I see it, is there's a big difference between accepting the risk that things will go wrong despite the best efforts of everyone involved, and accepting the risk that something's going to go wrong because somebody decided that the 'best part for this is no part', or used the wrong grade wiring tape, or wedged in an accelerometer upside down, or decided that they didn't need a flame trench for this launch. The kind of thing that's given Go Fever a deservedly bad name - and as far as I see it, the one company seriously pushing for space colonisation at the moment, has Go Fever writ large. Maybe not in individual launches but very much in the 'pushing this as fast as possible otherwise its not going to happen' mindset. Relying on volunteers shouldn't be an acceptance that any level of risk is OK. Deciding what level of risk is OK - well that's a whole other can of worms. I don't have an answer to that one, but I'll freely admit that I'm biased against private industry deciding it unilaterally - because given the choice, private industry will invariably go for the faster and cheaper option. I suspect we may disagree on that point. Edit: Actually I have a sort of answer, which is that any volunteers should be volunteering on the basis of informed consent, but that's going to be damn difficult in practice. I kind of agree with your second point in general (although I'd lump societal dogma in with state coercion and violence) but I suspect we'd disagree over the specifics. Sticking to a single path can be beneficial for getting things done though, provided that other paths have been fairly considered, and folks have had a chance to make their case for alternatives. Sadly, what worked for the Apollo Program is considerably harder to implement at a societal level. Anyhow, thanks for an interesting debate - and thanks for keeping it civil. Happy to read your answer to this post, but shall we then agree to disagree, and let other folks get a word in edgeways on this thread?

OK, that makes more sense. In which case, I would say that humans are the only species on the planet capable of trying to fulfill that push. To use your own words, the push is inevitable, success is not. I also disagree that off-world colonies are the only obvious job we have. As the book which kicked off this thread apparently concluded: "this will be really hard to do and possibly should even never be done, but definitely should not be rushed into." For what it's worth, that pretty much sums up my opinion. Is somebody going to try building off-world colonies? Probably yes. Are off-world colonies important enough that they're worth rushing, cutting unnecessary corners for, and killing or injuring people for entirely avoidable reasons in the here and now? Certainly not.

The point I was trying to make is that your second paragraph was treating off-world colonisation as inevitable, something that was part of the flow of life as we know it, a fundamental aspect of existence that you couldn't see any point in opposing. Whereas, in your first paragraph you were fretting that off-world colonisation would never happen, because of human nature. They're both reasonable viewpoints, they're just opposed to each other.

So which is it? Something that isn't going to happen at all without urgency because human nature, or a fundamental aspect of existence? Those two paragraphs look contradictory to me. Surely if it's a fundamental aspect of existence, then human nature isn't going to stop it? Conversely, if human nature is strong enough to stop it, then doesn't that imply that it's not actually fundamental?

Not going to bother rehashing the 'settling the Americas isn't remotely like settling Mars' arguments yet again. No part of human civilization is technically or economically ready for settling other planets. We have a couple of billionaires talking about it, but one has failed to make much progress at all so far, and the other is focused on one part of the endeavour, namely building the rockets to get there, and mostly ignoring (as per the original post here), the vast swathes of other technical, economic, sociological, political, etc. parts. As per my previous post, justifying a Mars city as a backup plan for an extinction level event is a flimsy argument at best, and I would argue that the economic case is even less substantial than that. I say city, because optimistically, I could imagine a small, internationally funded, scientific outpost on Mars, or a small mining outpost /control centre for monitoring the robots that are doing the actual mining. That's making the bold assumption that offworld mining becomes economically viable of course. At this point in time, a city on Mars is basically one big Elon Musk vanity project which he's driving hell-for-leather with a 'move fast, break things, and damn the health and safety' company culture. If there was a good, waste-anything-you-like-except-time, reason for building a Mars city, that attitude might be justifiable, but I don't believe there is. As for the fact that every putative Mars settler is volunteering with no illusions? Even assuming that's correct (I certainly wouldn't trust Musk to be impartial about the potential risks), having a bunch of eyes wide open volunteers lined up is no excuse for slapdash corporate corner cutting. If anything, it makes that carelessness even more reprehensible. I'm dumping on Musk here but if we end up with more companies competing to go to Mars, I doubt they'd be any better than SpaceX. Edit. To answer your thought experiment - almost certainly but possibly not in the way you had in mind. We've already seen Bezos' legal shenanigans over the Artemis lander bid. I fully expect any private actors in this space to deploy their full panoply of lawsuits, FUD, and lobbying tactics against each other, in the name of competition. TL: DR. Take with a grain of salt the purported intentions of those calling for putting on the brakes is fair advice, but I'd take the purported intentions of those who resist any calls to put on the brakes with two grains.