for example.

Of course, that one is a medical design, and wouldn't work for this purpose, but there are various industrial CT systems out there, and I'm pretty sure there have to be some that would work for this as well.

To point out the obvious, this isn't necessarily evidence of malfeasance. If you look at code contributions at a company, you'll find that a small number of code reviewers miss a disproportionate number of bugs, too, but it is often because they're reviewing code that is hairier than the stuff that other folks are reviewing, making the review process harder.

Are these papers similar to the average paper that the journal(s) normally publish? Are these papers that most people would have refused to review because they seemed questionable even at a glance? Are these papers in areas that are so specialized that nobody can adequately review them, and only a few people were even willing to try?

Do certain groups of authors tend to request the same reviewers because they've worked with them in the past, and is the higher rate of retraction correlated with higher rates of retraction by those specific groups of authors? Or are reviewers assigned randomly as they should be?

Are those reviewers' acceptance rates similar to the acceptance rates for other reviewers? It says they reviewed 1.3% of papers published by the journal and accounted for 30% of the retractions, but that tells us nothing about whether they had a higher acceptance rate than other reviewers. They could easily have published a smaller percentage of papers because they rejected *more* papers, but reviewed papers in areas with a higher rate of mistakes or disagreement about methodology (e.g. maybe they review a disproportionate percentage of meta-analytical papers).

Are these papers being retracted because of things that should have been obvious from reviewing the paper, or were the reasons obvious only after getting more information?

The portion of the (paywalled) article that I could read seems like at least some of these are likely to be situations where authors and reviewers were inadequately independent, which is problematic. This is a strong reason to require at least one randomly algorithmically picked peer reviewer for all papers, chosen by the journal.

Something besides the ratio of surface area relative to mass?

Clearly you can, because you could easily add 1 kg to the internal mass of the Apollo capsule and it would still be able to safely re-enter the atmosphere.

Why? I mean yes, eventually, but you can put the reactor up there inert, put the fuel up there inert, and have a manned mission to assemble the thing. Nothing inherently requires that the reactor be active or in a ready-to-activate state during launch.

Besides, you need to be able to do a safety inspection with a CT scanner or similar to verify that there are no weld failures or other damage caused by the launch process or the landing process, or else you risk the thing immediately spewing radioactive steam as soon as you turn it on, and contaminating the reactor vessel in such a way that renders it irreparable, all because you cut corners, so you're probably going to want to have a manned mission to activate it anyway, or else some very high-end robot tech. Either way, you should be able to come up with a way to then unwrap the fuel and install it into the reactor after you've safely landed the whole thing on the moon, because that's relatively simple compared with all the other stuff that needs to be done before you can safely start up the reactor.

You're making a huge number of very questionable assumptions about how this should be done, and dismissing my comments based on those flawed assumptions. I'm not the one being absurd here. There are ways to do this that are very, very low risk. Whether they choose to do it that way or not is a different question.

Not particularly. U-235 has a half-life of 704 million years. This is not the stuff that makes reactors scary. It's the short-half-life byproducts that are super dangerous to be around.

The NIOSH workplace exposure limits for Uranium are 0.05 mg uranium per cubic meter. That means as long as the explosion evaporates the material over at least 20 million cubic meters, even if it evaporates into the air, you're not likely to cause too much harm. This is only about twenty empire state buildings worth of air, by the time you're flying at an altitude where fuel could realistically evaporate, it should evaporate into many orders of magnitude more air than that.

And realistically, AFAIK, no failed spacecraft has ever completely evaporated during reentry other than tiny satellites that are designed to do so, so that isn't a realistic concern anyway, IMO, unless you're planning to ship fissile material inside tiny satellites, and realistically, probably not even then, given the quantities involved.

Or to put this another way, if the entire 1 kg chunk of U-235 got somehow flattened out into a sheet (so that the uranium wouldn't shield you from most of its own radiation) and you were to lie down next to it, you'd still probably get less than the equivalent of one chest x-ray per hour of radiation. Mind you, I wouldn't want to leave a kilogram of uranium lying around on a children's playground, but realistically, the swingset is probably more likely to kill someone. The risk is nonzero, but not so nonzero that it's worth worrying about, IMO.

From a safety point of view, the highest risk would be it landing on the ground somewhere, and some terrorist finding it and stealing the nuclear material before the government does. And given that there's only a 29% chance of it hitting land, and maybe a 0.1% chance of any given land region being within a short distance of a terrorist cell, I'm not sure that's worth thinking about too hard, either.

The risk is nonzero, but it is so laughably small that I'd be more worried about the spacecraft physically hitting someone and killing them on impact than the tiny amount of U-235 killing someone.

I guess if the spacecraft missed you by a few meters and you somehow didn't die from the dust cloud, the criticality event from the impact might give you cancer someday, but...

Easily prevented by doing a few hundred unmanned tests at full depth for progressively longer periods of time, and using a portable CT scanner to see if there are any signs of hull damage after each descent.

I mean, for real companies, the free market does sort it out, because regardless of the payout for the deaths and whether it bankrupts the company, nobody is going to ride in a submarine knowing that the company's last design collapsed on the first try.

The problem is the existence of concepts like shell companies and the corporate veil. Most people don't like the idea of rich billionaires being able to create products and services that kill people without meaningfully getting punished for killing people, but the corporate veil is strong, so there's a real chance that the punishment would bankrupt the company, but the person who set up that company could be almost completely unaffected financially.

Worse, the company that goes bankrupt could be a shell company that's deliberately designed to fail, at which point the larger company that owns that shell company and all of its IP rights could then move on to a similar project with a similar shell company under a different name, and go on to kill again. Think of it as the murdering version of what Chinese companies with random 5- to 7-letter gibberish names do on Amazon when they get too many bad reviews, and you'll understand the problem.

Now imagine importing cars under similar conditions. Car catches fire and burns your family alive? Your one remaining living relative leaves a negative review, people stop buying from that company, and MIXFLIP motors goes under, and MIXFITZ motors is born, and has only five-star reviews, until the next family is toasted, and MIXFITZ dies and GENFLIP spins up. And because of jurisdictional boundaries, there's no accountability.

And this is why we have safety laws, and this is why companies going out of their way to avoid being regulated is so dangerous to everyone. The market can only work things out if there is actual accountability for bad enough failures, and corporate law is designed to limit accountability in ways that could easily turn them into mass murdering machines in the absence of regulation.

By forcing products that could be dangerous to undergo certain levels of testing and certification before they can be sold or used in the U.S., you ensure that the cost of entering the market is high enough to make those shell company tricks infeasible, thus ensuring that there's only one name for the company when it sells in this market, and that if they screw up badly enough, they'll genuinely be destroyed by the market.

Doesn't matter. The absolute worst case heat situation should be reentry. Apollo's ablative heat shield is only three inches thick. Putting a three-inch ball of phenolic epoxy resin, wrapped around a half an inch of lead, wrapped around something the size of a golf ball is well within the realm of what can be done.

Steering things in the wrong direction, apparently — solar panels, the country, etc.

I don't think you realize how little radioactive material we're talking about here. 1 kilogram of U-235 would power a 100 kW reactor for more than two decades, if my math is right. That's about the size of a golf ball. You're telling me you don't think they can put enough lead around a golf-ball-sized chunk of uranium to ensure that it doesn't end up exposing anyone if the ship explodes during launch?

Once again, the environmentalist fringe has set standards so high that they are impossible to meet so that they can berate folks for not meeting them.

Meanwhile, PLA 3D printer output can be trivially mechanically shredded and extruded into new filament several times. It's hard to say that PLA isn't recyclable with a straight face.

+1. In my home town, the pay phone by the high school was used for exactly two things: calling parents to pick kids up after away games and calling in fake bomb threats(*) to get out of tests. I would expect similar behavior from public phones today, sadly, minus the kids calling their parents part.

* When I was a freshman, this is what the seniors told me people had done in previous years. I cannot corroborate the story with any actual evidence. Also notable: this was in the early 90s, before school shootings and bombings were really a thing.

Lots of things are pointers under the hood. But that's really irrelevant to the point.

Yeah, EVERYTHING is implemented at the base level in assembler, so pointers are in use everywhere. And I learned assembler first. But if that's your idea of where one should start, someone else can say we need to start with transistor theory, with just as valid an argument.

Pointers aren't required for most purposes. They're often just an optimization, frequently a questionable optimization. It's true that C pretty much requires pointers, but in C++ references can generally be substituted with greater clarity. Pointers are almost never used in Java (are they ever?), and certainly not in Python. Or many other languages I could name. (Yeah, they still exist "under the hood", but that's not the point of an exam of early or intermediate programming skill.) For that matter check out D https://dlang.org/ . That's a language that would be my favorite if they had a better way to document your code (last I checked Doxygen didn't do a good job) and it it had a slightly better library. (As it is I currently prefer C++ except for stuff that's heavy in unicode, where I'll switch to Python.)

C is actually easier than Java, though doing anything complex is harder.

A C++ subset doesn't have to be any harder than Java, and can be at least as capable. (The problem would be documenting it...and for students, learning to use only the subset.)

What's the storage *density*? I have the impression that grid scale batteries often use (relatively) low density storage, so they take up a lot of space. Lithium batteries are relatively high density (lots of storage/volume). Dense storage is, of course, part of what makes them so dangerous when they catch fire.

Perhaps it you wanted this to last through a blackout you'd need to give up your basement, rather than just part of it as with lithium batteries.

Unnh....there must be a reason Japan was researching whether uranium could profitably extracted from sea water. I believe that it was because decent ores for uranium were becoming scarce. (I used to know whether that was the reason they gave, but I can't certainly remember any longer....I think that was it though.)