Terwin

I vaguely remember something about the heat tiles only being needed for earth because the mars atmosphere is so much thinner, so the weight of the heat system might be what is referenced

Diving suits do not need to deal with radiation(water does that very well) nor do they need to deal with the potential for super-sonic micrometeorites(water is good at slowing things down) Diving suits also benefit from additional weight(to counter buoyancy), while space suits are only needed in an environment where the cost per pound is very high. I do not know if these suits are set up to deal with radiation or micrometeorites, but making protective gear as light as possible yet still functional, tends to get very expensive, as mass offers a lot of protective value. (look at the cost of ballistic ceramic inserts compared to just using a plate of RHA in the same pocket, or the cost of active armor compared to the equivalent mass of RHA{not counting any support or propulsive structures})

Jet propulsion: Simple, robust, easy to stumble upon(anything with any sort of moveable mantle or inflatable bladder can empty that bladder for thrust), low energy cost real life examples: squid, many microorganisms, all finned animals(depending on your definition) Rocket/explosive propulsion: Simple, robust, very energy expensive, can be short bursts or extended, can be very damaging without proper preparations real life examples: bombardier beetles Jet Engine very complex and delicate to air-flow disruptions, primarily extended uses (can take several seconds just to stabilize the air flows), more efficient than rockets but still very energy intensive, must be maintained long enough to destroy most biological materials before it becomes useful for propulsion. real life examples: None While it is somewhat surprising that we have critter(s) that use rocket propulsion, jet engines require very smooth and consistent airflows for extended periods to be any better than rocket propulsion, and biological organisms just do not have the energy output to manage that.(assuming you do not get injury or inflammation near the path of the air-flow, which would make your jet non-functional) TLDR; No biological jet engine without both genetic and cybernetic engineering. Jet/rocket propulsion, sure(see squids and bombardier beetles), but not jet engines. Too fragile and complicated.

I thought the moon has wonky gravity that causes problems for long-term orbits, and that is why we have mars satellites before we have moon satellites.

Capsules are a perfectly legitimate approach for launching or landing small amounts of cargo or passengers using a minimum of resources. They can even be used for high-velocity direct transfers between habitats. Emergency escape capsules from ISS is a good example. The main-stay of manned flight should have moved beyond capsules by this point, of course.

You would need a reason that the much more flexible approach of storing that energy as gravitational potential(ie fly high and dive, like predatory birds on earth) is not a viable option. If you want a continuous flow(as opposed to a 'fart bird'), you will need continuous compression and combustion. Those are not things that biological animals can manage very well. How rich of a food source would the animal need to be able to afford the energy to fly? A small jet(Eclipse 500) has a dry weight of 3,550 lb (1,610 kg) and consumes 130-220 gallons of jet fuel per hour of flight. 130-220 * 6.8 lbs/gallon = 884-1496 This is just under one quarter to just under one half of the dry-weight. Gasoline which is less energy-dense than jet fuel, has ~5100 calories per gallon. This suggests that a 2-lb jet-bird would need to eat an amount similar to the daily diet of Olympic swimmer Michael Phelps(10K calories) for every 2 hours of flight. Assuming of course that there are no efficiency losses when reduced to such a small size, and that the conversion from calories eaten to combustion fluid is also free. Jet propulsion is just too inefficient for biological animals that do not gargle with petrol.

The Chinese had gunpowder quite early, and they used it for rockets and bombs(and failed rocket-chairs), but the machining and accuracy needed for firearms needs tools and materials that just did not exist at that time.

Depends on how big a comet you want and how patient you are. If you are willing to wait a century for a small comet, an ion drive could work, if you need something large within a decade you would probably need Orion.

If you have uranium, thorium or radium under you, then Radon will bubble up. If you have an air-tight seal both top and bottom, then the radon will just go around. Radon is a heavy gas that will settle in low areas once there is no longer denser stuff pressing down on it. Basements are a great place for collecting Radon if you have it in the area. An air-tight base will not be able to collect radon the same way, because it will not have a nice sheltered basin to collect in. Also, mars is much smaller and lighter than earth, does it even have the same prevalence of heavy/radioactive elements as earth? Didn't the moon take a big chunk of lighter materials away from earth, making it denser than average for a rocky body? It might turn out that finding places where Radon vents on mars could be very exciting from a prospecting for radioactives front.

Sorry, but I was just struck by how this phrase consisting of a single letter and a pair of words that are antonyms when used as adjectives not only makes logical sense when one is used as a noun instead, but is even used this way with significant frequency. Perhaps I need more sleep.

I would like to say that I find the prospect of more EM radiation than would be created with total conversion of > 33 suns worth of mass , all collecting together in a volume smaller than 1/2500 the volume of the sun to be more than a little horrifying. Even if the incoming energy was evenly distributed, I find it difficult to believe that would be a survivable energy density anywhere close than a light-year. And all that energy would be traveling at the speed of light, so the black hole would need to form in no more than 1/3 of a second to keep it from escaping. As such, I would be happy to hear that kugelblitz cannot form larger than 10^8m a well.

I hope not. Generally speaking software gets called mature when one or more of the following are true: 1) The software and the hardware it runs on is old enough that no one knows how to fix or update it 2) The software is sufficiently complex and crufty that it can only be updated or maintained by a small number of Gurus that have been working on that system for more than a decade 3) like #2, but all the Gurus are dead or retired(more common than #2) 4) The entire development staff want to discard and replace the system with something less complex and crufty, because it is quickly approaching #2 5) The hardware needed to run the software no longer exists And the only reason to hold on to 'mature' software is because it is business-critical and too expensive to replace. It would be nice if the software development space were stable enough for 'mature' to mean the same thing it does in other industries, but that is not smething I expect to see in my life time.

The faster the train travels, the more wear on both the pantograph and the lines themselves, also the less power that can be transferred. This makes charging while traveling across rural areas a bad idea as either it is ineffective, or your train travels very slow when it could be moving very fast. Station charging may be less of an issue, depending on how long the engine spends at each station. Have you looked at how much power is required for the different classes of train? I could see it being viable for light commuter trains, but heavy industrial trains seem likely to need too much power between stops.

There is a huge difference between reusable by design and ad-hoc reuse I would put the shuttle half way between at 'designed for cost-plus refurbishing' Designed for reuse is great at reducing costs, as opposed to ad-hoc reuse which is often reminiscent of the 'red-neck' culture which uses it extensively, often under ridicule from other cultures. (Although in space flight, 'kerbal' may be a more appropriate term, considering the number of parts supplied by 'jebs junkyard ' ) Yes it feels wasteful to destroy 'almost new' equipment in orbit, but the cost of refurbishment may well be higher than the cost of sending up new, purpose -built and tightly secured equipment. Both getting to space and operating in space are very expensive. As such, things that are a no-brainer in your back-yard are just wasteful in space. Edit: consider the costs of multiple EVAs vs a custom designed, single use robot vs making new panels and launching them attached to the vessel that needs them

I vaguely remember nuclear waste being encased in steel and cement to make it an undesirable source of dirty-bomb materials. This sort of treatment would also likely make it undesirable for reprocessing.

We may not even need that much. There have been examples of real AI models that have ideology added at a high level of importance such that the model considers thermonuclear war preferable to misgendering. Much like HAL found killing the astronauts to be a solution to not letting them find out about the monolith in 2001. We just need a model with some capability to act and an incorrect priority tree(if we are even capable of creating a correct one), and we will create our own great filter. No rebellion needed, just the absolute adherence to the instructions provided. Kind of makes me glad that current computers need such finely detailed and specific instructions that things like hitting a moving target are beyond the capabilities of most programmers. (making a command to hunt down and kill all humans highly implausible even if it were deliberately attempted)

High altitude may be less of a problem for plants when the earth is not in an ice age(remember: ice caps, glaciers, and year-round snow covered mountains is very much not the norm in geologic history) and higher carbon in the atmosphere helps plants survive in much less favorable environments, such as during the Carboniferous periods.

Any process humans are capable of performing can also be done naturally (ie without intelligent action). As such, if travel into the past is possible, then all of causality is broken. And considering the scale of the universe, natural paradox will happen. What impact do those two have on your universe? Can it even exist?

Caffeine, Capsaicin, Nicotine, urushiol, and many of the spices we use are all ways plants try to limit what eats which parts of the plant (Caffeine and nicotine are to stop bugs while capsaicin and urushiol are to stop mammals). Humans delight in eating all sorts of pesticides(some even pointed at mammals). So long as they are using pesticides with human-safe LD50 numbers, I do not see a problem. (The pest control company I use for my home and yard uses stuff that has a LD50 in mammals higher than table salt, as in eating equal amounts of the pesticide and table salt will kill you from the table salt first) I still wash my produce however, but more out of a concern from dirt or the contaminants over any pesticide concerns.

Didn't he just say that the magnetic fields do not distort? You have multiple magnetic fields added together. Which makes sense as permanent magnets(iron ones at least) are formed by aligning the atoms so that their magnetic fields add together instead of subtract form each other. That means any 'distorted' magnetic field is just multiple fields added together. So you just add together the effects of each of the magnetic fields and you get the result.

If we try to use a magnetic field for energy storage, could that be more efficient than batteries, or is it just a different description for capacitors/super capacitors?

I am under the impression that x-rays tend to interact weakly unless you have a lot of mass/density, and that is not something deuterium is known for(having an atomic mass of 2). This is why x-rays pass through flesh easily and can be more easily blocked by denser bone. That being the case, you would need exceptionally high reflectivity. If, for example, there is a 1% chance of an x-ray being caught by a deuterium atom each time it encounters the atom, and a 1% chance of encountering such an atom with each pass through the reaction chamber, then you would need the average reflection to be better than 99.99% or else the majority of your x-rays will escape before imparting any energy into your fuel mass. Also, conduction is a very potent means of transferring heat, and even with all your perfect x-ray mirrors, you lose most of your accumulated heat should any of the fuel you are heating come in contact with your containment vessel. Then there is the need to extract work from your closed fusion system, so you need a controlled way to extract accumulated heat from your reaction chamber without stalling the reaction. So perfect x-ray mirrors are not enough, you also need perfect insulation to keep the heat contained in the fuel, which is made harder because you would then need to extract the generated heat from any helium you made so as to pass it on to the incoming deuterium which needs to be hot enough to continue the reaction.

I remember walking through one of those during one of my NASA visits. I think it was at Houston, but it might have been the cape , or possibly even the infinity science center just east of Louisiana on I10. Ah, it was the infinity science center, and they just have a mock-up of the destiny module: https://www.visitinfinity.com/galleries-exhibits/

You either need a large O2 tank for this, or you will or you will evaporate all the O2 and still need filters in the main O2 tank because you are no longer catching all of the H2O and CO2. This is also a separate tank that needs filling and emptying, little better than a he tank. A large enough O2 tank with adequate filters will always be heavier and more complex than the main O2 tank with the same filters . (Filter size and mass is relative to the amounts of ice it needs to catch, not the size of the tank, so your solution will either clog or have more weight. Possibly both)

At 400km altitude(ISS altitude) it only takes 90 minutes to orbit, so if you have the dV to get to an equatorial orbit with each flight you can fly up to 16 times per day, more if you have a lower orbit or use multiple launch pads. (but tandem launches might be a bit much for now)