Terwin

The heat must go somewhere and any time you move energy up a gradient (ie moving heat from cool to warm) you generate waste heat. As the atmosphere acts as a thick blanket, how do you plan to remove more heat from the planet(including the air) than you generate in waste heat? Also, as we are already in an ice age(polar ice caps are NOT normal for the earth nor are glaciers), is further cooling even a good idea?

I would very much refuse to put a used battery of unknown providence into any of my devices. (even with less risky batteries like 12v car batteries, I stick to new or refurbished by the manufacturer) I have no objections to the batteries themselves, only to swapping in a potentially adulterated battery to save a few minutes of charging time. From google: A battery typically makes up around 40% of a new EV's price. How that battery is treated is key.

In spite of movies, shooting a can of gas will not cause an explosion. Having a battery-pack land on a sharp rock or bit of metal will likely cause a chemical fire that will destroy the entire battery facility. Just plugging in a damaged or faulty battery pack could do the same. Also, Batteries and tires are the two most wear-sensitive parts on a BEV, and who wants to get an 'old' pack with only 2/3 the range of their brand new pack?

Google says that up to 25% of EV mass is the battery, and 25% looks like a good estimate when I spot checked a couple vehicles(model 3: 26-27%, Cybertruck: ~24%). I cannot imagine that 'swapping out' ~25% of a multi-ton automobile is something that either automotive engineers or public safety officials would find appealing, or even tolerable. That is entirely ignoring the fact that a newer battery is worth much more than an older battery and that anything with that much power density *will* be explosive if it is mishandled. The fact that merely puncturing a battery with the currently favored automotive battery chemistry will start fires/explosions is probably a consideration as well. note: v8 engines weigh 400-700 lbs, so this is similar to swapping out the engine multiple times to fill the fuel tank. Edit: This is also ignoring that a lot of EVs look like they are incorporating the battery hardware into the undercarriage super-structure to improve handling and reduce weight/cost, making a swappable BEV even more of a premium item than current BEVs)

I thought most microwaves running at X% power were actually turning on and off so that they run x% of the time at full power and 100-x% of the time it is off and just giving the heat time to spread out.

Still a couple days early for that

Fusion does not have the same waste, but it still produces neutrons and thus neutron activates near-by materials(something reactors hope to use for lithium production) so the pusher-plate of either will quickly become radioactive and thus dangerous for proximity.

I do not see either engine being useful on pusher-plate sized vessels. Sub-sonic airliners need 10-20% of their mass in engines, and that would be totally inadequate for something as unaerodynamic as a pusher-plate vessel, and also would be far from sufficient for the types of speeds you would need for them to be useful. Just use disposable solid boosters to get it to orbit and never let it land. (Once the pusher plate is used, you never want it near people again, so landing would be a war-crime even if you use a parachute instead of nukes to slow down)

/s^2 is ' per second per second' This is a unit used in acceleration. Then Multiplying it by s^2 turns it into a static(not time dependent) unit.

The color indicates the temperature of the heated material not the total amount of energy. A huge starship would not be a higher color temperature than a smaller capsule unless it was also compressing the air more rapidly. The amount of heating each atom of air receives from compression heating is limited by how compressed the air gets and how quickly it can radiate that heat away. If you can determine how hot the plasma is, you can just get the color by checking the black-body radiation for that color. "An approximate rule-of-thumb used by heat shield designers for estimating peak shock layer temperature is to assume the air temperature in Kelvin to be equal to the entry speed in meters per second. For example, a spacecraft entering the atmosphere at 7.8 km/s would experience a peak shock layer temperature of 7800 K." A cool-white would be above 6500k, so to get a cool-white plasma would likely require a speed of > 6.5km/s or ~ mach 19. a light blue looks closer to 10,000k so ~ 10km/s or ~ mach 29 > mach 20 sounds very bad for anything near-by, so I would not expect superman to use this sort of velocity near anything delicate(like cities)

They said they wanted to have two consecutive good landing simulations over water before attempting it with the tower, and that seems pretty reasonable to me. How many consecutive 'good' landings would you demand before trying it for real?

Not all companies do or are even allowed to make money. SpaceX is a private company and could readily spend every dollar they earn on the owners pet projects if they so choose. As far as I can tell, the entire purpose of SpaceX is to make a mars colony a reality, and if they go bankrupt the day after the colony reaches self-sufficiency, then that will be considered a win. Funding that colony is the reason starlink exists, and if needed, other space-based companies may be founded to help. They are even getting government funding for some of the development costs by bidding on side-projects that NASA wants done which are within the capabilities of the planned interplanetary craft. I expect there to be major financial issues, but the richest man in the world seems intent on using both his fortune and his business accumen for this purpose and I am not going to complain about that.

Sociopathy requires no malicious intent, just a disregard for the right and wrong, and ignoring the rights and feelings of others. I have yet to meet a 1 week old with regard for anything beyond their own discomfort, and perhaps bright colors. (It looks like they do not even start showing attachments to caretakers until 6 weeks)

A quick search on 'child developmental psychology' mentions Piaget's 4 stages of cognitive development. According to that, it is in the 3rd stage(7-11 years old) that "children also become less egocentric and begin to think about how other people might think and feel." I fail to see how you can be empathetic if you never even consider how others might think or feel. (I would suspect that many people never actually achieve that level of interpersonal awareness, but that is the theory at least)

It always amuses me when people forget that all humans are born as self-centered sociopaths, and only through socializing do we learn to reciprocate, cooperate, and all of the other 'virtues' of humanity. Learning to read does not help one come to the realization that all of those 'humanoid interaction devices' are actually just as self-aware as oneself, each with their own views and understanding of the world that suffers from ones own, and just as valid(I can think of many so called adults that do not get this, sadly. Many of them using such ivory tower thinking that humans start as an effective blank slate that can be shaped as they like) And being raised by robots would not improve this situation.

I did not cite any examples or tropes, what are you talking about? I was attempting to illustrate that rocket burn times per flight are so radically different from jet burn times per flight, that attempting to compare them is like comparing how you serve blueberries and watermelon. Sure they are both firm berries that get soft when they go bad, but they are wholly different from each other in many practical ways. I cannot imagine someone being satisfied with a slice or two of blueberry, nor would I expect to meet someone who frequently eats dozens of watermelons at a sitting. Much like I would not expect rocket engines to have maintenance times < burn times like jet engines can manage. Rocket burn times are just not on the same scale as turbofan engine run-times. I also strongly suspect that chemical rocket engines tend to burn much hotter and higher pressure than turboprop engines, if only because ~80% of the turboprop working fluid is inert gasses. Rocket engines clearly have a much higher fuel through-put than turboprop engines: "A Boeing 747 or 777 typically consumes approximately 5,000 gallons of fuel per hour while in flight." "Raptor consumes 140kg of methane per second" Conversion: Jet A1 Fuel Conversion Chart Lbs Litres U.S. Gallons 1000 568 150 5000 gal -> 33,333 lbs -> 15,119 kg 15,119 kg/hr / 3600 s/hr = 4.2kg/s So 4.2kg/s(all 4 jet engines on 747) vs 140kg/s (per engine). This suggests each raptor burns ~ 133 times as much fuel per second as a 747 engine. So yes, that seems very different, even if the outside environment does not change much.

Wikipedia says the burn-time of f-9 first-stage using FT engines is 162 seconds. Even just a quick visual inspection of the engines of a Falcon 9 would mean maintenance time > run time. So if each first stage took less than 1 hour of inspections/repairs per launch, it would still be getting maintenance > 2x the total burn time of the engines, something that would likely put most airlines out of business. (9*162 / 60 = 24.3 minutes of total burn time per launch. May not include <1m for landing burn)) If SH takes 2 hours from landing to launch, it could still average > 10x maintenance time per flight-hour. (F9 takes just less than 10 minutes from launch to landing for RTLS) I do not see much value in taking SH maintenance down to even a 1:1 ratio of flight time to maintenance time, as the falcon 9 needs >30 minutes to load fuel, and I would not expect SH to be faster than that. (As refueling is often counted as maintenance, taking SH down below 10:1 maintenance time:flight time might well be impossible even if the only maintenance is refueling)

Mechanical power from water is easy and is more than 5000 years old, so that will clearly be a thing very quickly. Mechanical wind power is almost 3000 years old, both less concentrated and less reliable, but still pretty useful and should be back fairly quickly. Turning either of those into electric power mostly requires magnets and wire, so intermittent local power(like a flour-mill that doubles as a battery charger) should be reasonably common, but if it gets set up by someone with limited understanding of electric theory(such as myself) such a charger is likely to damage the batteries with every charge. Fortunately, batteries are more than 200 years old, so if you have copper and zinc, you can turn those into electrical power as well. Unfortunately, oil is of limited use without refineries, and refineries would be a primary target(tanks run poorly without fuel after all), so only chemists would be able to run vehicles until new refineries were produces(I think fractional distillation can provide something functional, but I would expect it to be hard on any engine that uses it) Straight crude could be burned as fuel, but would generally be inferior to coal, as liquids are harder to store and handle than solids. Wood would likely be superior to both where it is available, as it is much less likely to produce hazardous fumes when burned. So long as fuel reserves held out, food production would be in good shape, but would go down dramatically once farmers run out of diesel. Food processing would likely have issue before that however. Fortunately, it looks like almost all of the population is is major cities(86% in cities of 50k+ in 2020 for the US), so a drop in food production is probably not as critical as it would otherwise be. There would probably be at least a decade of 'everyone is a farmer' with the related loss of population to starvation before we stabilized and started growing again. Assuming no one was in a position where they could take advantage of our weakened state to invade.

Mars can be as little as 34 million miles or as much as 250 million miles. When on the other side of the sun, mars is more than 7x the distance from Earth as when it is close, and when it is close, there is no need to detour around the sun, making it even further. No matter what sort of transfer you make, multiplying the distance by more than 7 has a major impact on if the transfer is even possible, not to mention the time increase.(There are many parts of the orbit where waiting to launch will make you arrive earlier)

If you can ignore gravity and have a vacuum -only drive, why not just throw on a propeller? Either the prop is enough to accelerate you or you can use your vacuum drive. It can even be an electric prop so you only need fuel for the vacc drive.(You could throw it inside a shell for protection, but just making it retractable would likely be better)

I was thinking that mars and the moon would primarily start as retirement communities, with support personnel, etc. The lower gravity should reduce strain on the body and allow for more autonomy for people too weak to get out of bed on earth. Might even allow for better longevity as it would reduce the minimal functional strength of bones joints and muscles(including the heart). Sure such individuals would need to be in a liquid bath for launch and possibly landing, but they would have the funds and low concern about long-term viability needed for such an endeavor. The colony would be the laborers and heath workers supporting the retirees.

Looks like the plan is for Starship V3 to have a capacity of 200t to orbit. Why would NASA be worried about an early prototype not being as capable as the expected delivered rocket? Especially when the delivery plan provides greater performance than was initially expected? Did you also expect NASA to complain when grasshopper never made orbit?

You need incredibly good precision to manage replaceable parts. One person would likely spend their entire life just working through the steps to get to a precision where things like interchangeable parts could actually work, and that assumes access to materials that the romans never made use of(and thus may not have had access to). There are many things that took one or more life-times of refinement to get things to a point where other things could be done. Measuring precision(length, weight and volume, each taking a great deal of effort), materials purity(each material needing lots of effort, and often other highly pure materials needed as reagents) I would expect that an immortal with unlimited modern knowledge and authority that went to the 1st century Roman empire could manage to double or triple the rate of advancement, even cutting out a few hundred years of non-progress during the dark ages if they had unlimited food/no need to eat as well. I'm not sure if preventing or encouraging wars would be more beneficial to that advancement, but the wrong choice would obviously cause set-backs. Unlimited authority and immortality would both be needed or else someone would kill or imprison you in the first few months because you were trying to do something that would annoy someone ruthless/powerful.

I believe you need to use an engineer to 'perform maintenance' to transfer fuel from a nuclear fuel container into a reactor and transfer depleted fuel from a reactor to a nuclear waste container. Automatic maintenance can also perform this function(but I think the engineer is still needed)

Considering the speed of bureaucracy, this might well be a prompt response to IFT-1