Codraroll

I don't really get the fascination with scaling down by fractions. In practice, very few situations actually call for it. How often do you need to start with an even meter or a kilogram and split it equally into three? Whether it's cooking, science, or construction, the measurement you start with is rarely exactly one unit.

Back in my university days, there was a "greatest nerd contest" featuring participants from the various study programs. One of the questions was who had memorized the most digits of pi. The contestants from physics and mathematics rattled off dozens of digits, while the one from civil engineering stopped after six. When asked about what he thought about falling so far behind the others, he answered: "If you ever need to build a circular structure to a greater precision than one millimeter per kilometer, you are allowed to look it up". That answer awarded him full marks on the question.

That's just language. The half-liter is as ingrained in the language over here as the pint is in the UK. And I doubt it would cause that much critical confusion if the word "pint" became established short-hand for half a liter. Few people would complain about getting 3 cl more beer than they asked for.

Are you suggesting that various Russian sources may at times contradict each other, and may not all be in agreement about what they regard as truth? Never have I ever ...

How hot can it get before other subsystems start taking unacceptable damage? And how hot can it realistically become in there?

It may be timely to ask why it takes 20 years as costs $150/MWh to run a nuclear plant. It's not necessarily because building a reactor is really, difficult and takes a long time. Some navy shipyards build them as a matter of routine. The USS Montana, a Virginia-class nuclear submarine, was laid down on May 16, 2018, and entered service on June 25, 2022. Granted, it was ordered back in 2014, but that still means a fully operational nuclear reactor went from "we should buy this" to "running nominally, captain" in barely over eight years. I doubt it's any less expensive to build a reactor to fit inside a combat submarine than in a peaceful and spacious building on land. Nuclear power plants become so expensive because of the volumes of red tape that have to be involved. Each plant has to be designed from the bottom up. All the parts have to be custom made and individually certified, then inspected thrice over, and the volume of documentation required probably outweighs the building itself, were it all printed on paper. The safety regimen is extremely rigorous to minimize the risk of nuclear disaster, but it's also a huge cost driver. And I highly suspect that many of these safety regulations were imposed after lengthy lobbying campaigns by "nuclear safety interest groups" whose pockets were full of coal money. Combined, they make nuclear power way too expensive and time-consuming to be worth considering, while coal and gas stand out as the cheap and easily available options, without much consideration for the dangers of that industry. I can't recall the source off the top of my head, but a while back somebody found out that more deaths could be attributed to coal mining accidents since 1940 than the entire nuclear sector - including not only the events at Chernobyl and Fukushima, but also Hiroshima and Nagasaki. That's not to say that all safety regulations should be abolished so every Joe's Nucular Family Shop can weld a hat rack in an old boiler to a turbine and create a reactor in their own back yard, but it might be an idea to review the regulations and see whether the accepted level of risk can be heightened a little bit if it means a tenfold reduction in cost.

The problem with creating a grid based entirely on renewables is that it's quite smooth sailing up to, say, 80%, and from there the difficulty of replacing the remaining non-renewables increases exponentially. The demand for electricity goes up and down all the time, and with renewables, so does the supply. Preventing a gap from forming in the wrong direction is the hard part (managing a surplus is tricky too, but easier). You need some sort of storage that works long-term, to give you juice when everyone needs more electricity than the turbines and PV panels don't quite produce enough. This remains an unsolved challenge on a grid-wide scale. Or rather, the "storage solutions" we do have (fossil/radioactive fuels) are not renewable. There's batteries, of course, but those are massively expensive and can't store power indefinitely. They are good for evening out variations from hour to hour, maybe day to day, but on a longer-term basis they are inadequate. Hydroelectric reservoirs are wonderful for energy storage as they can store oodles of energy for a long, long time. However, they require the right quirks of geography, their capacity is difficult to scale beyond a certain point, and long-term forecasting is difficult. The amount of water in the reservoirs is limited by the local rainfall or snowmelt, and it's a bit of an art to determine when to run the powerplants and when to hold back. On the one hand, you want to have remaining water in the reservoirs for when you need it later. On the other hand, you also want to have enough idle capacity to absorb the next rainfall, so you don't have to send water to the sea when the reservoir goes full. Other kinetic solutions, of the "big block of concrete in a mineshaft" variety, are completely off the table. Just try to do the math on how much energy you can store in a one-ton block suspended by a 100 m cable. To put it like that, it's far from enough to justify the maintenance cost of the pulley arrangement. Then there's the solutions that involve some kind of chemistry. Typically hydrogen electrolysis, or methane production. They work, but they are hellishly inefficient. If memory serves correctly, you put 6 kWh in for every 1 kWh you get back, and I'm not sure if that includes the generator efficiency. And then there's the maintenance of the electrolysis plant. So unless a revolution of sorts happens in batteries or fuel synthesis, some base load production will be required to bridge the gap between what renewables can produce on a bad day and the demand for electricity on that same bad day. Some plant that can be fired up to create energy when the other methods don't give enough. That's where nuclear power plants - and to be realistic, probably gas-fired power plants, at least for a long while - will retain their niche for many years to come.

I know of one method that's being explored, although it sounds a little insane. And by that, I mean that the name alone should send shivers down the spine of anyone who dabbled in physics at a high school level or above: Magnetohydrodynamics. The science of the electromagnetic properties of electrically conducting fluids. The concept is fairly simple. Take a magnetic fluid, and move it. This induces a current in wires, like moving a solid magnet in an ordinary dynamo. The plasma generated in a fusion reactor is a suitable medium. This essentially turns the reactor output directly into a generator, which means you'll skip all the inefficient middle steps between heat and electricity. The generator efficiency can be very high, up to 60-70% or so. The science, however, is a bit complex. Take all the problems associated with calculating the movement of fluids, like the Navier-Stokes equations, and sprinkle in all the intuitiveness of Maxwell's equations on electromagnetism. They influence each other. Have fun. And the practicalities are nuts. After all, you're working with plasma, which tends to be rather hot. It's also moving fast, which creates all sorts of funny abrasion problems. And of course, this being nuclear fusion, there's intense radiation everywhere too. You might get slag deposits here and there too, which interrupt the flow, and then Navier-Stokes rears its ugly twin heads once again. But the potential is awesome. If you can build it without something melting and warping.

Paradoxically, fossil fuel companies are also over the moon with these news. It gives them ammo for their own lobbyism campaign. "Mr. Senator, the great state of Befuddlement needs more electricity, and we understand that you want to subsidize wind power to make that happen. In the last couple of decades, solar and wind power has grown in scope to rival the coal industry. But why throw money into the winds when you can have the future? Look here, new technology is on the way: clean fusion, unlimited power from water, so those turbines will be obsolete in a few years! It will only take a few years before fusion power plants are available, we promise. After all, it's 2022, how long can it take to develop fusion power? Instead of spending money to transit into an outmoded form of energy production, stay your hand, wait until fusion is available, and let the Coal'n'Gas'n'Oil'n'Stuff Corporation handle the state's power generation needs in the meantime, like we do today. Letting the status quo continue for a few more decades is definitely the right thing to do, for the sake of our walle-, uh, for the sake of us all." This is because the exact same process used to work in reverse: "Herr Chancellor, the great state of Unnamed European Country needs more electricity, and we understand that you want to build more nuclear power plants. In the last couple of decades, nuclear power has grown in scope to rival the coal industry. But why bother with that scary radiation stuff, when you can have the future? Look here, new technology is on the way: clean wind and solar power, unlimited power from the weather, so those nuclear plants will be obsolete in a few years. It will only take a few years to install enough solar and wind power to make the entire grid green, we promise. After all, it's 1986, how long can it take to make renewables feasible on a countrywide scale? Instead of spending money to transit into an outmoded form of energy production, stay your hand, focus on expanding solar and wind power, and let the Coal'n'Gas'n'Oil'n'Stuff Corporation handle the country's power generation needs in the meantime, like we do today. Letting the status quo continue for a few more decades is definitely the right thing to do, for the sake of our walle-, uh, for the sake of us all." Or the TL;DR: "No, don't do the thing that threatens our market position today! Do the thing that might threaten our market position in four decades, at the earliest, and let us remain top dogs in the present while your eyes are on the future!"

Or for that matter need it. If the warhead can re-enter independently, one might as well make it capable of performing the plane changes to maneuver on its own, instead of relying on a spaceplane to do it before the warhead is let loose. Come to think of it, a missile on an orbital spaceplane would be a very counter-intuitive thing for those who don't know orbital mechanics. Imagine the Hollywood movie: A space-shuttle-like craft in orbit, approaching its target. Some maps and words on a computer screen in the control room shows the target on the ground up ahead. The order is given to fire the missile. The craft's bomb bay doors open, clamps around the missile disengage, and a little piston pushes it soundlessly out into space as it engine spins up. So far, all the standard fare. But then the engine engages, and the missile fires backwards relative to the spaceplane. The engine burns for a few seconds before fizzling out. The first stage is then decoupled, dropping away to reveal ... not a second-stage engine, but the warhead nose cone. And then little streamers of air begin to appear around the warhead, in the opposite direction of the exhaust of the engine that was just discarded. The spaceplane, at this point, is flying sedately over its target or even way beyond, looking backwards at the missile as it plunges through the atmosphere. I think the movie would need a three-minute scene of the nerd character explaining the orbital mechanics, with diagrams, before the director would allow the missile strike to be shown that way.

A net energy gain, but within which system boundaries? The National Ignition Facility has achieved net energy gain in fusion before, by producing more energy in the reaction than the laser delivered to the fuel. However, this was less than the total power of the laser, which again is less than the power required to run the laser, which again again is less than the power required to support the whole experiment. To quote Wikipedia: "The experiment used ~477 MJ of electrical energy to get ~1.8 MJ of energy into the target to create ~1.3 MJ of fusion energy." I guess this time, they created >1.8 MJ of fusion energy, by delivering ~1.8 MJ of energy to the fuel. There's a long way up to 477 MJ still, and they have to go yet beyond that to get an equivalent amount of electricity back. However, it's a way that has to be walked in steps, and it's good news that yet another step has been taken.

I take it the balloons are inflated for celebrating the return? They don't seem to be needed for buoyancy. (okay, I guess they would be if the craft somehow ended upside down and had to right itself, but as-is, they look a bit goofy).

It's a platform that can expose its payload to space, sit in orbit for a while, close up the payload bay, then return to Earth. The wings and such allows perfect steering to land softly on the closely guarded runways at specific military bases, instead of splashdowns somewhere in a vast expanse of the ocean/desert. All the other alternatives you list either lack return capability (like ordinary satellites), or cannot return any cargo outside the pressurized compartment (Dragon, Starliner). They can get payload to space all right, but not expose it to space conditions and take it back afterwards. Their design is centered on preserving their cargo inside the capsule (which has an environment distinctly different from that on the outside), and ditching the non-pressurized parts before reentry. This latter limitation also allows sample tests that cannot easily be conducted on the ISS. Samples for space exposure could be delivered to the station in an unpressurized compartment and mounted on the outside, sure, but returning them to Earth would be trickier. They would have to be stowed inside the Dragon/Starliner capsule to survive reentry. That would necessarily involve maneuvering them through various airlocks, then clamping them down inside the capsule somehow, and that's a hassle and a half for large samples. Launching the same payload on a satellite might be cheaper and easier on the surface of it, but then they would have to develop a whole new reentry system for the payload, capable of soft precision landings. Why bother with that, when the X-37 is readily available? It may have been built initially as a technology demonstrator of aerodynamic orbital maneuvering, but turned out to have the exact right capabilities for orbital sample returns and so was adopted for the purpose. A re-entering spaceplane is not any less visible than an SLBM launch. The relevant agencies of the adversary would probably notice and react if one of the more mysterious American space objects (one they'd be certain to keep a close eye on at all times) suddenly initiated re-entry on a course towards their early-warning radars. What with the blazing fireworks display of re-entry and all, it wouldn't be very hard to spot. Unlike the stealth bombers specifically built for the purpose of sneaking in and dropping their payload before the enemy even notices their presence. It's easier to go under the radar than rushing at it from above. Just ask Mathias Rust.

Yes there is, as you have repeatedly been told. Why don't these simple facts sink in?

Besides, what would be the need? The US already has weapon systems that can sneak into enemy territory and deliver nuclear packages on short notice: the B-2. It was designed to fly into Siberia unseen to hunt mobile missile launchers or drop bunker busters on storage sites. No need for a fancy space weapon lighting up like a Christmas tree on radar with the blazing heat of reentry. As evidenced by how Ukraine managed to strike a strategic air force base using modified drones from the 1970's, flying across the direction of a war zone for some 600 km without being intercepted, it's reasonable to assume the B-2 would have been able to snoop around for quite a while without being detected. Possibly while all the relevant intelligence assets had their eyes glued to the fancy little distraction in orbit.

Eh, it's better that it's hanging on when it shouldn't, instead of coming off when it should be hanging on.

Starship has flown higher than N1 ever did. Well, maybe parts of the N1 went higher.

The terminology here has all sorts of fun technicalities. The farthest distance traveled by any craft designed for humans might be a certain Tesla Roadster, although it wasn't designed for humans in the regime of space. But in either case, I guess Snoopy, the Lunar Landing Module tested during Apollo 10 and subsequently ejected into a heliocentric orbit, comfortably beats Orion on every relevant metric.

Orel predates all of these, however, and remains in an earlier stage of development. SLS began development in 2011, flew the other day. Orion was announced in 2011, also flew the other day. Starliner was unveiled in 2010, flew its first test flight in 2019, and again this year. Orel was made public in January 2009 and remains on the mock-up stage today with the first flight years away. Orion as first conceived (the Crew Exploration Vehicle) dates back to 2006, but this predecessor also went through a flight test in 2014. By 2025, Orel will be older than the CEV is today. Setbacks and delays are common, but not to this degree. The craft you mentioned are infamous for their multiple delays, but at last had their pre-development concluded with test hardware in flight. That milestone is still years away for Orel, and the odds of further delays are quite substantial, with the way things are going.

The first launch of the Orel manned spacecraft of the Russian Federation has been postponed from 2023 to a later date https://www-interfax-ru.translate.goog/russia/872946?_x_tr_sl=ru&_x_tr_tl=en&_x_tr_hl=no&_x_tr_pto=wapp

How typical. I had my alarm clock set for 7:30 this morning. Had I got up in time, I would have caught the launch as it was happening, while eating breakfast. Unfortunately, I woke up tired as a deflated balloon, drenched in cold sweat, and with a slight fever, so I decided to give it an extra hour (yo-ho, yo-ho, a PhD student's life for me). While eating breakfast, I discovered that the launch had already happened, less than an hour earlier. Note to self: try not to get sick around predicted rocket launch dates.

Landing without leaving the vehicle? Granted, that'd be like doing a cross-country drive to Disneyland, only to do a U-turn in the parking lot and driving home again.

Probably the launch of cruise missiles from one country, and interceptors from the target country. I.e. in Ukraine at the moment.

They made one for US cities as well:

Skylab was fifty years ago, and measures have since been taken to prevent anything like it from happening again. "We should be allowed to repeat the mistakes others learned to fix decades ago" doesn't strike me as a very good argument. If a rocket's lift capacity is 24.5 tons with a proper deorbiting system and 25 tons without it, its design lift capacity should be 24.5 tons, no excuses. Disposing the empty stage by letting it fall wherever is like saving money on garbage disposal by not paying the garbage collection fee, but just dumping it in the river behind the house instead.