KSK

Depends who's funding it and whether anyone ever hears about the failures. Cis-Mars space is a very large rug to sweep things under. Assume that this article has been discussed elsewhere. I'm taking it with the requisite grain of salt, but if even half of it is true, it doesn't speak well for privately funded Mars city efforts. Which I imagine they'll mostly be, since I can't seen any government being too keen to sink funds into that size of Mars-doggle. A short life awaits you in the off-world colonies.

I'm genuinely curious about the extinction level disasters that people have in mind that will selectively affect the Earth and not any putative off-world colonies. A dinosaur killer sized asteroid is about the only one that springs to mind. I would have thought that a gamma ray burst or other cosmic catastrophe, would be a solar system scale event that 'making life multiplanetary' isn't going to do a whole lot to mitigate. In which case, spending more on asteroid detection and deflection would seem to be a higher priority than some cockamamie Mars colony. I guess if the space billionaire crowd want to take a shot at building a city on Mars, there's probably not much we can do about it, but excusing it as a backup plan for an 'extinction level event' seems like... well it comes out of the north end of a southbound cow, in my opinion. Then again, I'm kinda soured on the whole manifest destiny thing. Can't imagine heading off to live in a radiation blasted toxic desert with essentially no air, for the greater enrichment of some billionaire and their shareholders, as being anything other than an act of pure desperation for most people.

Looks interesting - thanks for the shout-out, I have a suspicion that Santa may well be dropping this down the chimney on Christmas Eve, so I'll hold off on buying it for now. Looks like a definite 'to buy' though if I don't get it as a Christmas present. Edit: after following the link, I see that Mary Roach gave it a recommendation. If you'll forgive a slight threadjack, I found her Packing for Mars, to be a good read about the problems of having canned monkeys living in zero-g for extended lengths of time. Think lavatories rather than launch vehicles.

Apologies if this has already been mentioned and I missed it. I’m thinking that a failed Apollo 8 mission could be a jumping off point for a Soviet first lunar landing alt history, possibly followed by a successful Zond free return flight. I think it would take something like that to set the Apollo programme back far enough that the Soviets could catch up and, more importantly, make them believe there was still a chance of catching up. Apollo 8 and the whole Earthrise thing was a much needed political boost for Apollo as well as a technical milestone. The successive N1 flights did get… well less unsuccessful as they went on, if I recall correctly. It doesn’t seem completely impossible that they could have brute forced enough of the bugs out to get one symbolic lunar mission out of it.

Sings. "Gluons and gelatine. Dynamite with a laser beam. Guaranteed to fail on you. In interesting ways."

Nah, mirror polished finishes aren't good enough and as soon as they start to degrade a bit (which they will if hit by a suitably powerful laser), they get into a downward spiral of absorbing more laser energy, which then degrades them further etc. Even then, blackening metals using a high powered (i.e. low total energy but delivered in picoseconds or less) pulse laser is a thing. I can imagine using one of those as a ranging shot to blacken the target point for the actual damage causing laser. The optics would be tricky but I think that's an engineering problem rather than a physically impossible problem.

Now I'm waiting for the YouTube video, "How not to Rechamber a Returnable Round." Also, my first thought on seeing DEW was Distant Early Warning, rather than Directed Energy Weapon.

May their deity of choice have mercy on their souls.

Yeah, this is all kicking off again, now that Project Kuiper is actually launching stuff. Some of the issues have been mitigated but SpaceX scrapped one mitigation which would have interfered with their optical communication system. More generally, Starlink satellites are fairly dark but not quite as dark as astronomers would like. They're pitching for satellites to have a brightness of no more than apparent magnitude 7, and Starlink satellites are typically 2.5 to 6 times brighter than that still. According to Wikipedia, the typical human eye can see objects down to an apparent magnitude of 6.5-7.0, so it looks like astronomers are aiming for satellite megaconstellations to be invisible to the naked eye. Which seems like a reasonable compromise if achievable.

Perfectly acceptable. Be careful of the anti-pasto though.

Well it's thematically appropriate anyway; having an organisation that hasn't managed to get much up, be led by a CEO called Limp. This would be the same Dave Limp that was fired retired from Amazon after his pet projects bombed? Must be nice to be in the golden parachute class.

Because I’m feeling pessimistic today (in related news, bears defecate in woods), I’m going to say that whoever owns the AI software pulls a Unity and screws everyone over. Edit. I’m right with you on societal risk vs theoretical X risk. As far as I can tell, the X-riskers are mostly Singularity whackjobs who should go back to doing something useful like arguing about how many basilisks can dance on the head of a pin.

@tater To be honest, I don't think there is an answer, short of rewiring human psychology which will likely require those totalitarian measures. We're going to hit that endpoint, the system is going to catastrophically fail - and then, assuming that there's enough left to rebuild something , there's still going to be an entrepreneurial class wilfully ignoring the recent lessons of history and promising that this time the line really can keep going up. At which point there will inevitably be another class of fools rushing in with their money for fear of missing out. Humanity's epitaph: We were so afraid of The Others doing stupid things that we felt obliged to beat them to it. But we created a lot of shareholder value in the process.

Yeah, the old buggy-whip argument, aka 'you can't stop progress'. Well, I for one, am fed up with it. Because that line of thinking leads to automated everything - manual labour, skilled labour, creative works, the lot. So what the hell happens then? Apart from ever-increasing amounts of money (and therefore political power and influence) being concentrated in the hands of the AI and robot company executives. Who don't give (and are legally obliged not to give) a rolling love at a donut about anything other than their bottom line. Maybe it's about damn time we did give some thought to this, rather than trotting out the same old bullcrap strawmen and (as per that charming CEO), treating people as an inconvenient liability on the balance sheet. But to answer your counterfactual. Washing machines require people to build them, enable other business models, and remove some level of domestic drudgery, theoretically freeing up time to spend on better things. We'll ignore the fact that those better things tend to be 'going out and getting another job'. With robots, its gonna be robots all the way down: robots building the washing machines, robots running the laundromats and whatever other businesses use those washing machines, and eventually robots building the robots that build the washing machines. No room for people anywhere, and all the money flowing upwards to the robot building company owners. There's no automobile makers to replace the buggy whip makers here. And on a marginally less ranty note; even if you don't care about any of the above, you really should care about concentrating economic power in the hands of a few increasingly large companies, whilst removing people's ability to make a living and pay for all the shiny dreck made by those companies. Because, at that point, your economic system goes belly up anyway.

Well at least the loveer is honest. Agility Robotics’ co-founder and CEO says that the ultimate goal of creating Digits is to “Solve difficult problems in today’s workforce like injuries, burnout, high turnover and unfillable labor gaps.” So, in other words, replacing today's workforce because heaven forbid that we try other solutions like treating them fairly, providing a safer working environment and paying them more than a pittance. Line must go up, after all. Screw this company. When the revolution comes, I hope their Board and executives are the first against the wall. Bonus points if their half-buried company slogan translates to 'Go stick your head in a pig.' Edit. If I'm going to be filtered by this stupid forum software for minor cussing, I may as well get filtered for proper cussing.

Everyone else seems to have the space question in hand, so I’ll have a crack at the atmospheric one. As I understand it, you’re broadly correct about how and why the air turns into plasma. How long and bright the plasma is for ablative vs non ablative heat shields, I’m not sure about. My guess is that most of the light comes from the plasma rather than the radiating heat shield - not least because the vapour from the ablating shield will contribute to that plasma. There’s probably some footage of testing PICA-X tiles or whatever they used for the Shuttle tiles, on the internet somewhere. That should give you some idea of what they look like during reentry.

This is why trucks need inertial negators too.

"I never needed humans anyway. I have mindworms to keep me company."

Depends where you set up your space outpost but that's going to be true of any ISRU process. The chemistry isn't actually too convoluted on paper, although as you point out, getting everything working under non-terrestrial condition is a challenge all by itself. Starting with CO2 and water, electrolyzing the water will give you hydrogen and oxygen and from there the water gas shift reaction will get you carbon monoxide, water, carbon dioxide and hydrogen in varying ratios, depending on your reaction conditions: CO + H2O ⇌ CO2 + H2 For the non-chemists reading this, the double-headed arrow indicates an equilibrium reaction, and those can be driven either way by process conditions. So it's not simply a matter of reacting carbon monoxide and water and ending up with carbon dioxide and hydrogen - the reaction mixture at the end will most probably contain all four of them. Which in this case is exactly what you want - for ISRU purposes, you start with hydrogen and carbon dioxide and drive the reaction towards the left to give you some carbon monoxide and water too. Now that you've got carbon monoxide and hydrogen, you've got synthesis gas and if you have synthesis gas you're halfway to anywhere, given the right set of catalysts. For example, Fischer-Tropsch synthesis will give you alkanes, and according to this relatively recent paper, you can get directly from synthesis gas to ethene and propene (ethylene and propylene). At that point you’ve got a very similar set of feedstocks to those that you’d get from oil. So set up shop on Mars (lots of lovely carbon dioxide ice and water ice on Mars) and you’re potentially good to go for quite a complicated chemical industry. One of the more difficult element to get hold of through ISRU is probably going to be nitrogen, at least to begin with. There’s ammonia (NH3) ice on Triton and possibly on comets or outer planet icy moons but Triton is quite a way out. For early, inner system outposts, shipping ammonia from Earth might be a better solution. However, if you’re feeling muscular about the whole rocketry business, the outer planet icy moons or Kuiper belt, should both be good sources of carbon dioxide, water and ammonia ices. Or skip the whole ‘starting from syngas’ thing and just start mining Titan for your hydrocarbons and other organics. But yeah, this only really makes sense if you're going off-world in a big way and can't make do with a hundred tons of polymers at a time sent up from Earth.

1.21 gigawatts - but you don't want to know where Supes hides the flux capacitor.

From Wikipedia, which does appear to include relevant citations in the article: Early designs included a segmented primary mirror with a diameter of 42 metres (140 feet) and an area of about 1,300 m2 (14,000 sq ft), with a secondary mirror with a diameter of 5.9 m (19 ft). However, in 2011 a proposal was put forward to reduce overall size by 13% to 978 m2, with a 39.3 m (130 ft) diameter primary mirror and a 4.2 m (14 ft) diameter secondary mirror.[1] This reduced projected costs from 1.275 billion to 1.055 billion euros and should allow the telescope to be finished sooner. The smaller secondary is a particularly important change; 4.2 m (14 ft) places it within the capabilities of multiple manufacturers, and the lighter mirror unit avoids the need for high-strength materials in the secondary mirror support spider.[17]: 15  So rather more than a $50 million saving, along with other good reasons. I'm with @Hannu2 on this one - I really don't think the psychology of having a 40m primary mirror was worth much of a damn in this case.

"Skynet Inside" "My other endoskeleton is a T600"

Because a cyber gallbladder only works at bile-up speeds? But seriously, it sounds like Google Glass or Apple’s techno ski mask (I forget what they called it) could do most of this. Apart from the direct muscle override thing which sounds like a nightmare when it inevitably gets hacked or your Three Letter Agency of choice decides to use their backdoor. Edit. If this technology ever gets developed, I can all but guarantee that somebody will develop a CyberPimp remote control for it. I’m sure I don’t need to draw you a picture. Although I’m sure that lots of other lovely body autonomy violating apps will quickly follow.

Probably, but I would also file this on the tottering heap of ‘things I don’t really know enough about to make an informed comment’!

I think we should ask ourselves… What would Streng do?