Terwin

light waves also get stretched in the same manner(called red-shift), but as the amount of space between here and there grows faster than what could be covered when traveling at the speed of light, it can never get here. Those stars are not moving compared to the local space, it is just that there is more space being created between here and there than could be covered if you were moving at the speed of light. If there is more space-time, then both gravity and light must travel the same distance and would get 'stretched' the same amount. Unless gravity waves can travel faster then the local speed of light, they can never 'pass' light that is traveling through a vacuum, and have the same range limit due to the expansion of space-time. Just because the speed of sound may be higher in a stretched rubber sheet than in a relaxed rubber sheet, does not mean that gravity waves can travel faster than a photon in a vacuum, regardless of how that space is stretched or warped.

I see no reason that gravity waves would not have the same limitation. Gravity waves do not get to exceed C just because the points they are traveling between are further apart than they were at some point in the past. They may get to stay at C instead of occasionally getting absorbed and re-emitted like EM waves, but that is the only difference I see between their travel speeds. Perhaps you can explain how a gravity wave travelling in a straight line can get ahead of a laser traveling parallel to that wave through a perfect vacuum without breaking relativity? Without this, gravity waves are stuck in the same light cone as EM radiation, and only have greater coverage within that cone because it is much easier to shield a region from light than it is to shield it from gravity. A light-wave and a gravity wave traveling through 'stretched' space would travel at the same speed unless blocked by other obstacles, and both would get frequency-shifted by the same amount by the expansion of the universe. Perhaps you could argue that gravity waves of a high enough frequency and amplitude could be detected more easily at a certain distance than light of the same frequency and amplitude, but the light would still be there, just less of it because light is easier to block or re-direct.

That does not seem particularly mentally healthy, are you confident that spending time with those people is not having a deleterious effect on your own mental health?

Sounds like good practice for remote operation of robots for construction in hostile environments such as orbit, Luna, or Mars.

Cold water tends to work so long as the cold is being applied, but for longer lasting relief, take water just below the temp where it is painful on healthy skin, and apply it to the irritated skin. If it is not painful on healthy skin, it should not cause any damage, but on the irritated skin it will be painful, then after you remove the heat it will not itch for a while. I suspect it is related to either desensitization or using up neurotransmitters for your pain receptors, so that it takes a while before the itch can return. (often long enough to fall asleep if you hold it under the hot water until it is no longer painful) This is the most effective method I have found for dealing with the itch of poison ivy without damaging the skin by popping all of those fluid filled blisters with scratching.

Musk wants to 'go fast and break things' so making mistakes and learning from them is part of the game plan. 'If you do not need to put it back at least 10% of the time, you are not removing enough parts' sounds like another 'make mistakes and learn from it' Verifying safety for human passengers by successfully launching unmanned lots of times with plenty of safety margin seems more reliable than proving that the vehicle is theoretically safe on paper like they did for the shuttle(before they realized it was a lot less safe then they thought).

Maximum dV is usually achieved with a TWR close to 1. There may be a desire to 'get them out' quickly, and thus have a higher TWR at launch. a TWR of 1.1 is fairly high, Super heavy with Starship has a TWR of 1.4, which is rather high (according to this 6 year old reddit thread: https://www.reddit.com/r/SpaceXLounge/comments/ae79vi/any_idea_about_the_thrustweight_ratio_of_super/ ) Anything over 1.5 is often considered wasteful for a rocket. Your missile would need a TWR of 1.64 to get off the ground. Missiles will often have a higher TWR for the sake of speed(and not getting shot down) Wiki (https://en.wikipedia.org/wiki/Intercontinental_ballistic_missile ) says that ICBMs burn for 3-5 minutes to a velocity of 4km/s with solid fuel burning out faster. If we take 4000m/s over 180 seconds we get an average thrust of 22.2 m/s/s The best possible scenario for your heavy rocket would be a thrust of ~32m/s/s which would result in a total thrust of 19.5m/s/s or a twr of just under 2 for your version compared to a little over 3 for the original. But that would be a very poorly designed rocket because it would almost always be throttled lower than it could be. Usually you get much more thrust towards the end of your burn than towards the beginning, so you would probably spend a significant percentage of your fuel before lifting off, just because the engine is too weak to lift the much higher mass.

It already got TOTM for Nov 2023, is it even eligible for more than one?

Makes me think back to family road-trips where the back of the van was packed with coolers, bedding, etc. until it was roughly even with the back seat. If that room has a 40' celling, they will probably have so much stuff packed into that room that they do not see the beds until they get back to earth orbit.(not even then if it is half-filled with surface samples)

I think step size is related to average leg or stride length. Then again, kids with more energy can jump up multiple steps with shorter legs, while older people with less energy can struggle for the one step at a time, so perhaps not?

How much money have they saved on being able to use this booster 23 times? Even if the engines are only $1M each, that is 198M in engines alone.

To be fair, if you discover proof that the universe is not compatible with the rational mind, then the only rational thing to do is to disconnect from the universe...

'Nearby thunder usually has a sound pressure of 165-180db and sometimes more than 200db' 'A sonic boom is typically around 110db'. 'Sonic booms can be particularly loud and startling from large supersonic aircraft' 'Technically thunder is a sonic boom' Boca chica, TX averages 78 days of rainfall per year. Sounds like regulatory paperwork requirements more than a specific identified need to me.

I expect any fuel will burn more effectively, so probably hotter if you use the same fuel/air ratio, but if you adjust that ratio then your fuel use should be very similar, you will just need less air-volume to achieve the same effect. Fires would start easier and be harder to put out, so tech would be more dangerous in general.

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.