6,522 karma · joined March 21, 2012
No, that doesn't happen. Currents can be induced in the wires to the motors, but not in the motors themselves. For one thing, the outside surface of the motors is the aluminum rotor which is an extremely effective faraday cage. For another, coils don't act like antennas. Loops of wire in an electric field have the exact same voltage difference as a straight wire.
> Shielding helps of course, adds expense and adds weight, the two things that cut into how many you can make for $X and how far they can fly.
Shielding adds virtually zero weight; carrying a spool of fiber optic cable adds a lot of weight. All the drones in Ukraine right now are fiber optic but most of them are unshielded... the reason why is not that shielding is heavy, it's just that there are lots of jammers but very few truck-sized weapons intended to totally disable drones.
That's also assuming it would even work on a drone without an antenna. If these weapons are not relatively broad-spectrum then they will be very sensitive to the particulars of the circuitry, and they won't always work.
1 millisecond pulses and 70 kW continuous usage[1] which is roughly equivalent to the AN/TPQ-53[2]. 2 km range.
> Regardless I think the primary challenge with these systems will be energy on site and a surge of it during waves of attacks. Charged up capacitors can only handle so many waves.
That is not how this kind of thing works. Capacitors are a terrible energy source. Their voltage drops off exponentially as they discharge and almost all electronic are very particular about the voltage they require. A railgun wants current and does not care about voltage. Radio transmitters care a lot about voltage.
Regardless, a 70 kW generator fits on a small trailer. Smaller than the weapon itself. It will run for days on a good sized tank of diesel.
[1] https://www.twz.com/land/army-puts-50m-bet-on-next-gen-leoni...
[2] https://en.wikipedia.org/wiki/AN/TPQ-53_Quick_Reaction_Capab...
The difference is the size. Even a large magnet only hits that 20g force over an inch or two. An MRI pulls at that force over a full foot or more; equivalent to dropping the object from 20'+. Worse, the MRI starts pulling at 5 or 10 feet away. Objects can experience a tremendous amount of uncontrolled acceleration in fractions of a second.
It's not like a black hole- unless you are trapped under something very large, the crushing force is substantial but not incredible. In fact inside the tube the gradient is actually smaller than the entrance of the tube- you are pulled in strongly, but once inside the tube you are pressed against the wall somewhat less forcefully. Instead it's like an invisible waterfall, and any metal will be swept away in it, fast enough to put holes in you.
IMO that looks like a spot that would be pretty difficult to hit accidentally even if the ward failed. You'd have to push them down and the throttles are in the way.
Doesn't mean the switch couldn't have failed in some other way- eg the switch got stuck on the ward but was still able to activate with a half-throw, and spring pressure pushed it back into off during a bump. But switches generally only activate when fully thrown, and failing suddenly at the exact same time is not really what you would expect.
[1]: https://www.reddit.com/r/indianaviation/comments/1lxra3g/b78...
But many countries have large amounts of nuclear- many enough to supply most nighttime power. And in almost all countries, solar is by far the best and cheapest immediate option, and those countries should be building as much solar as possible until the marginal return of nuclear or storage or infrastructure for imports are cheaper than just building more and more solar.
> I am not aware of any large scale operating exports of solar energy from equatorial regions to Northern Europe, or similar distance.
No country is even close to a solar oversupply, much less a 2x or 5x. If there is no margin, why would those projects exist?
Resource reserves are unextracted and not replenished. They are not the same as storage.
That's besides the point! The window of highest demand completely covers the window of solar. You can build a LOT of solar before storage starts becoming cheaper than just building more solar. You only need storage if it's ALL solar- you can have a majority of your power supplied by solar with hardly any storage! There this idea that if you overbuild solar that power will have nowhere to go, or something- you can just turn it off. You use backup power for the non-shining hours and you're totally fine.
> And this is so easy and foolproof to do, just check out the Iberian power outage.
In fact I did[1]. Page 117: "In fact, in most of the network nodes analyzed, there is no correlation between voltage stability and the amount of solar generation or the amount of coupled synchronous generation"
They had 2.3 seconds of inertia, more than the regulated 2 seconds. Power sloshing through interconnects caused plant ramp rates to be overwhelmed one-by-one, causing the cascading failure, because they had no buffering. If they were all solar or wind plants, the failure would not have happened!
[1]: https://media.licdn.com/dms/document/media/v2/D4D1FAQGcyyYYr...
At the global scale this would ideally balance out- more equatorial solar is cheaper in the winter since they don't need air conditioning, so you just send it up north. That's the only really feasible solution to seasonal variation in individual countries- it's totally unreasonable to store 3 months worth of power. Its also important to note that even with 2x or 3x oversupply, solar is cheaper than nuclear currently is.
[1]: https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP [2]: https://www.pse.pl/web/pse-eng/data/polish-power-system-oper...
It's a little complicated to weigh stratospheric emissions- the CO2 has a larger impact, and while the water droplets and contrails left by planes somewhat counteracts it (by reflecting incoming infrared) it's harder to compare intangibles like mercury emissions from coal. If you just say its all a wash, that plant is equivalent to 120 747s running full speed.
Private jets consume more like .9-1.5 tonnes per hour, so that's equivalent to ~900 billionaires. That's a bit less than half of them which is probably a lot more than were at the wedding. They also probably parked them instead of leaving them circling in the air.
If there were 90 billionaires who flew 12 hours each way in their private jets, then they probably released around 2.5 hours worth of Monroe Power Plant time over those 90 days- 8458 tonnes. Fun fact, the pilots and flight attendants probably used ~1000 tonnes of CO2 worth of energy etc and exhaled ~25 tonnes of CO2 in that time. 25 tonnes is small compared to the planes (>.3%), but in those 90 days the planes released just .11% as much as the coal plant.
Coal really truly sucks and it's unfair that I can't eat tuna without getting mad hatter disease.
This is false. Power usage everywhere is highest when the sun is shining. There are also very very few places where solar power ever causes the market to bottom out with any regularity. Note that there is no technical problem with this- you can always just disconnect renewables from the grid.
The phenomenon you are thinking of -the duck curve- refers to the power demand after subtracting solar. The daily peak consumption of power in many places is wider than solar generation, so if there is enough solar you end up getting new smaller peaks just after dawn and around sunset. This is minorly inconvenient for non-renewable sources, which prefer to have more predictable demands.
> Usually most analysis ignore costs of having a buffer in the system
Correctly! Non-renewable plants are the ones that need buffer. Solar, wind, hydro etc can all be connected to a grid with zero instability- you just unplug them if nobody wants the power. Non-renewable plants have slow ramp speeds- they need the buffer in order to follow a changing load.
> Not to mention less land required, which is another of ignored costs.
This is incorrect; I don't know of any analyses which don't include land and interconnection costs which are obviously substantial. If you mean more intangibly... that's very silly. The US Interstate system is 3.9 million miles of road, with 60' medians, 16' of shoulder, and 48' of lanes. 237,250 square kilometers. The "blue square"[1] is 10,000 square km. The amount of land we spend on parking lots absolutely dwarfs it.
> Because nuclear is superior by every metric
Nuclear has not gotten cheaper- why would it? It's a big clockwork. We are not better at building pipes than we were 80 years ago. Solar has and will continue to: plants get more productive, panels get thinner, efficiencies go up. There is no grounding principle that indicates nuclear can be cheaper, and it certainly is not in practice. Solar is far cheaper than coal by capacity much less kWh, and nuclear plants are more complex than coal. What indicates that a 500 MW nuclear plant should be cheaper than a 500 MW coal plant, not counting running costs?
> Are they?
Demonstrably yes, absent weird conspiracy theories. Renewable installations keep opening at much lower costs than traditional plants.
[1]: https://blogs.ucl.ac.uk/energy/2015/05/21/fact-checking-elon...
The S6W reactor in the seawolf submarines run at ~300 C and produce 177 MW waste heat for 43 MWe. If the radiators are 12 kg/m^2 and reject 16x as much heat (call it 3600 W/m^2) then you can produce 875 watts of electricity per m^2 and 290 watts at the same weight as the solar panels. Water coolant at 300 C also needs to be pressurized to 2000+ PSI, which would require a much heavier radiator, and the weight of the reactor, shielding, turbines and coolant makes it very hard to believe it could ever be better than solar panels, but it isn't infeasible.
Plus, liquid metal reactors can run at ~600 C and reject 5x as much heat per unit area. They have their own problems: it would be extremely difficult to re-liquify a lead-bismuth mix if the reactor is ever shut off. I'm also not particularly convinced that radiators running at higher temperatures wouldn't be far heavier, but for a sufficiently large station it would be an obvious choice.
I was curious about this! The Extravehicular Mobility Units on the ISS have 8 hours of life support running on 1.42 kg of LiOH. That releases ~2 kJ per gram used, so .092 watts.
The 390 Wh battery puts out an average of 50 watts.
And the human is putting out at minimum 100 watts with bursts of 200+.
Long term it's probably reasonable to need at least 200 watts of heat rejection. That's about a square meter of most radiator, but it needs to be facing away from the station. You could put zones on the front/back and swap them depending on direction, as long as you aren't inside an enclosed but evacuated area, like between the Hubble and the Shuttle. The human body has a surface area of roughly 2 m^2 so its definitely not enough to handle it- half of that area is on your arms or between your legs and will just be radiating onto itself.
It's also not very feasible to have a sail-sized radiator floating around you. You'd definitely need a more effective radiator- something that absorbs all your heat and glows red hot to dump all that energy.
That also makes nuclear totally infeasible- since turbines are inefficient you'd need 2.5x as many radiators to reject waste heat. Solar would be much lighter.
https://en.wikipedia.org/wiki/Spacecraft_thermal_control#Rad...
Iran does not have the same degree of sexist restrictions as eg Saudi Arabia. It's a very different climate from places where salafism is more common. Female education in particular is highly supported eg: https://x.com/khamenei_ir/status/1869369086142296490
Absolutely untrue. Solar and wind can always just be disconnected at any moment. Wind resources are also a huge inertia source- windmill blades are massive grid stabilizers.
Renewable tech does not have a big coal fire they need to keep at a constant temperature. How about instead of requiring batteries with solar, we require coal plants to have sufficient bypass cooling that they don't need the load of a grid connection to stay cool.
Renewables are a boogeyman. The reality is simply that they are always able to undercut any fossil plant and they don't like that. It has fuck all to do with grid stability.
https://www.presstv.ir/Detail/2024/04/08/723301/Iran-among-t...
https://www.energy.gov/science/ip/articles/harnessing-power-...
https://www.energy.gov/science/ip/articles/harnessing-power-...
https://www.presstv.ir/Detail/2024/04/08/723301/Iran-among-t...
Simulation inside the engine can find resonances, show where shockwaves propagate, and show you how to build injectors (pressure, spray etc) so they are less affected by the path of reflections. Optimizing things like that smoothly along a range of velocities and pressures without a computer is not very feasible, and you need a minimum of computing power before you start converging to accurate results. The unpredictability of turbulence means low-resolution simulations will behave very differently.
> Launch-thrust engines that throttle down low enough and preciesly enough for landing
In large part this is due to improved simulation- spaceX made their own software: https://www.youtube.com/watch?v=ozrvfRHvYHA&t=119s
Experimentation was also a large factor- pintle injectors have been around for a long time, but were not used in production rockets until SpaceX (who moved from a single pintle to an annular ring). Pintle injectors are very good for throttling.
> Better materials to handle stress for flip over manover etc without added weight
We're still using the same materials- good ol inconel and aluminum. However 3d printing has made a pretty big difference in engines.
More rockets use carbon fiber, but that isn't new exactly and the main parts are still the same variety of aluminum etc. Titanium has become more common, but is still pretty specialized- the increased availability was probably the biggest factor but improved cutting toolings (alloys and coatings) and tools (bigger, faster, less vibration) have also made a big difference.
That's a huge engineering difference, roughly like the difference between a car and a helicopter. The Falcon 9 was also 4x taller, meaning 16x more force to correct a lean. A little burp would send the rocket right back up in the air.
One major reason for this is the mixing plate at the top of the combustor. Fuel and oxygen are distributed to tiny nozzles which mix together. The better the mixing, the more stable the burn. If you get unstable burning -eg momentarily better mixing in one area- it will cause a pressure disturbance which will further alter the burning power in different areas of the combustion chamber. At low throttle, this can be enough to cause the engine to turn off entirely.
Fluid simulations have made a huge difference. It's now possible to throttle engines down to 5% because mixing is much more stable (manufacturing improvements in the nozzles have also helped) and combustion is more protected from pressure variations.
The extra stability also just makes it easier to control a rocket period. Less thrust variation to confuse with drag properties, less bouncing, better sensor data.
Have you done an accounting of how many kilometers you can fit on a 200,000+ tonne boat? Seems to me you could cost-effectively carry nearly 20x as much cable weight as current cable layers. You need 25x the volume of polyethylene, but that's only 10x the weight and it isn't even counting the weight of the conductor.
Did you miss that the prestress is the point? There also could still be an annealing step- a continuous oven just like glass fiber manufacturing. Annealing time for prestressed fibers is very short, although I am very skeptical you could actually get something like this to work in practice.
> Moreover changes in temperature mean that using aluminum is probably going to cause the glass to shatter when the temperature changes.
Does temperature change at the bottom of the ocean? I suspect the heat per meter from resistive losses will be very, very low, but it is a missing point.
> Finally that cable is going to be heavy, so unless you make it around the same densisty as salt water, it'll have so much weight it'll snap as soon as you try and dump it into the sea.
That is addressed in the post- balloons to keep the bend angle low as it descends.
> it seems logical to just use PE.
MSC Irina has a deadweight tonnage (cargo+fuel etc) of 240,000 tonnes. PE would be ~15 cm thickness and weigh ~66 tonnes per km, so you'd get somewhere in the region of 3600 km of cable per trip. Atlantic submarine cables are <7200 km, so yeah- it seems very hard to make the case that glass is worth it.
NB: I do not believe that 14 MV cables could be 30 cm in width, but it doesn't matter much. If you make 8 trips instead of 2, it's still hard to justify. Current cable-laying ships are pretty small, despite cables still being decently big- cargo ships are way bigger. Not scaling up the ships would be very silly when they already exist.