Hannu2

Ammonia is seriosuly investigated as ship fuel. It can be made from air and water with renewable energy and it does not produce any carbon dioxide because NH3 does not contain carbon. Ship Diesel engines can use ammonia with relatively minor modifications. Negative things which need more development are toxicity, lower energy density than methane or diesel fuel and tendency to produce nitrogen oxides. https://spectrum.ieee.org/why-the-shipping-industry-is-betting-big-on-ammonia

It is very different, unfortunately. This kind of attitude that we should try things, take risks and accept losses, both money and lives, lacks completely in whole civilized world at these times. Now politicians calculate prestige and companies profits and porce of failura is set to ridiculous. Everyone knows that space industry would not be tecnomagic at all and it would increase production of everything by orders of magnitudes but investments are negligible. Couple of states build political pork systems and on eccentric billionaire try something. Most other companies just want to get their share of states' pork money. I think humans do not achieve any significant steps in space operations or industrial utilization before we get pioneering attitude of exploration era back. We should build ships and send heroic expeditions to almost hopeless missions until some come back with all the presitige for funders and data needed to make next operation more safely and productively. It do not work as business. It must be ideologically driven process. There will be huge business later but timescale and risks are so high that it is not good investment in modern quarter year economy.

Entropy is practically mathematical formulation for fact that probable things happen more often than improbable. Breaking it breaks all known natural laws and whole idea of causality. Yous have to define more conditions to think what could happen and I think almost anything. In my opinion knowledge and tech is not good or bad. Humans can be and they can use things to good or bad (intentionally or as unexpected side effect). So far humans have used everything preferably to generally bad things but after long suffering and learning process they have managed to do some partially good things too. Future inventions will work similarly. Ability to break all known natural laws, for example generating suddenly energy of couple of supernovas from nowhere, would maybe cause extinction before learning.

I do not think it is true. Basic nature of humans do not change during centuries. New tech is laways used first for war, if it is possible (and nuclear technology certainly is). Then for enslave others and make profit without caring environment or health issues. We can think such tinghs and make reasonable regulation after severe problems and even after that there are people who want to abuse things criminally to bad purposes. If researchers invented fission now or 2300 research would be immediately prohibited for companies and civilian universities and investigated only in large state's military research departments and their contracted companies. There would be period of nuclear tests and heavy bomb building, severe accidents and probable small nuclear war before proper regulation and civil use as energy source.

I do not believe that those hypersonic planes would be important in foreseeable future. They may get some very special application for example in military use but not massive commercial success. New rockets (Starship, New Glenn, Vulcan) will be next step and make new things possible but I would not say it revolutionary to send million cheap satellites for entertainment use. I do not believe any large scale manned operations in my lifetime (about 30-40 years). There are not real will and attitude needed for pioneering exploration anywhere in the world today. There will not be manned Mars trips or large operations on Moon before states and funders learn to handle failures, losses and deaths. There may be some short propaganda Moon operations from USA and China but not more.

How sad that those who always know how things really are and what would be best to do never have power and money to build perfect world.

I would not like to see that flap melting through a ship window as a passenger. But it seems whatever was left after re-entry worked well enough.

There is another problem. The energy density of lithium batteries is about 1 MJ/kg. Energy density of carbohydrates is about 16 MJ/kg and fats over 30 MJ/kg. It would be much easier to bring food on desert than electricity. It is difficult to invent credible explanation why any natural lifeform on any planet conditions would develop such an ability. But maybe electric metabolism would fit to some superadvanced civilization who lives mainly in space stations and have practically unlimited energy supply but want to save material resources of their solar system for example for Dyson sphere.

https://en.wikipedia.org/wiki/Nuclear_binding_energy#Semiempirical_formula_for_nuclear_binding_energy If you look the graph of estimated nuclear binding energy per nucleon around Z 120-130 (where island of stability is expected to be) (about 6 MeV), it is not much smaller than binding energy of typical fissile elements of uranium or plutonium (about 7 MeV). Energy released in fission is from difference of binding energy of fissile nucleus and tighter bound daughter nucleii. Released energy per mass unit of superheavy elements would not be significantly larger than typical uranium or plutonium isotopes. I have read that estimated densities of those elements in metallic state is about 40000 kg/m^3. That would give somewhat smaller nuclear bomb cores but probably not anything like pocket size nukes.

If such material was so radioactive or othervise dangerous and expensive, probably nothing generally significant would happen. As far as I know there are not applications in which low energy to mass ratio of normal fissile materials is bottleneck. It is easy to load enough uranium to reactor to run large ship few decades. Suitable cooling and safety systems and systems to convert heat to usable energy would be as large as now and there would not be nuclear planes, spacecrafts, cars etc. in near future. Mass of nuclear weapons are mostly chemical explosives to implode fissile material and safety systems so there would not be pocket sized atomic bombs. It is also hard to see than any army would be willing to take risks compared to modern suitcase atomic bombs.

Aerobic metabolism is one option to get energy to join phosphate to ADP to return it ATP. ATP then gives energy to biological processes when it break to ADP and phosphate. There is also many anaerobic ways to get that energy but aerobic oxidation is by far the most effective known way and makes actively moving lifeforms possible. If that referenced study is true there seems to be a way to run that reaction cycle with electricity. Of course there is no known biological mechanism to do that and it is impossible to say can there be a working cell. Even then lifeform would need material (and special chemicals like vitamins) to grow and reproduce damaged things but eating for just energy would not be needed and food consumption of adult (or otherwise non growing or reproducing) individuals would be very small compared to humans.

As far as I know low utilization is practical thing. 4 % enriched uranium is cheap and there is no economic reason to use it effectively . It would be technically possible to build reactor to use higher enriched uranium and use larger part of it or even breed non fissile isotopes to fissile but such a tech is internationally and politically very problematic because it would give rapid way to build nuclear weapons. Used fuel is recycled and reprocessed to usable nuclear fuel (MOX fuel) in some countries. I do not know is it purely business thing or has it some military or political reasons.

Antimatter is on same order of magnitude. Any element, including speculated supermassives, can not be even near.

I live in UTC+3 so I am in bed. But I wish good luck to Starliner and watch the video on next day. I have used that all interesting tech things happens in night time and all interesting astronomical phenomena are behind clouds or happen in summertime when is no dark here. SpaceX seems to break unwritten rule every now because I saw the first falcon Heavy and several Starship tests in live stream. I do not know if SpaceX prefer early morning launches (when they can set launch time by themselves, for example in test missions) for some technical or practical reason and many other operators prefer evening launches.

If you assume that target and projectile moves at constant velocities problem is relatively simple. You can make calculations in robot's frame of reference and take current time as t=0 moment. At first you can formulate a pair of equations for target. For example if target's position at t=0 is (ax,ay) and velocity (ux,uy) it is simple tx(t) = ax + ux*t and ty(t) = ay+uy*t. For projectile you get px(t) = vx*t and py(t) = vy*t. Now we have 2 equations for 3 variables, vx, vy and t at hit. Fortunately we know the speed of the projectile v and can write vx^2 + vy^2 = v^2. Now we have 3 equations. ax + ux*t = vx*t ay + uy*t = vy*t vx^2+vy^2 = v^2 Non linear equation systems are generally very nasty to solve but this is not. We can square 2 first equations and add them together. After little algebraic manipulation we get nice second degree equation for time. Generally you have 2 solutions and you can take one which is smaller positive (it means trajectories meet at future) and calculate vx and vy and aiming direction. If you do not have any positive t it means that projectile can not hit target (it happens if target's speed is larger than projectile's and geometry do not allow hit from front). Generalization to 3 dimensions is very straightforward. If yoy want to take target's acceleration or projectile's drag into account, things go very complicated very soon. If velocities are constant it is. With more realistic model it depends on many things. Usually one bullet is easy to avoid but that's why they use machine guns for aerial defense. Shoot few tens of bullets per second and give small deviation for individual bullets and target's day will be long and hard. I made decades ago a small game in which I flew simple craft in 2D world and tired to avoid and shoot enemy's machine gun turrets. They assumed that I have constant velocity and even I could dodge bullets I had to nerf their guns many times before it was playable.