The whole mass of iron powder does not need to be re-ground after every use. From what I've read so far, about half a percent experiences sintering and needs to be re-ground, and another half a percent breaks down into too fine of dust and needs to be filtered out of the exhaust, sintered, and then reground. The efficiency penalty of reprocessing the fuel is about 0.1% - 1 kWh of reprocessing for every 1 MWh of generation.
The existing nuclear infrastructure has its own issues, like long term waste management. My understanding is that long lived isotopes can be burned as fuel in fast breeder reactors, and the waste from those is safe in 100 years. Every nuclear power plant having enough cooling pools for 100 years worth of spent fuel is a manageable problem. But I've read that somewhere in that cycle some pretty nasty stuff gets generated & if it were stolen it could be used to make a potent radiological weapon. I think that's why building the things has been a non-starter in USA - we've been in a cold Civil War for the last 161 years, and I think MAGA would do a nuclear terrorism if we gave them the opportunity.
But yeah, iron powder is a drop in replacement for coal in stationary, utility scale electrical generation.
Iron powder is easier to transport than hydrogen. Hydrogen needs high pressure, cryogenically cooled tanks. It turns any metal it touches brittle. And it boils off over time, losing some of its energy value during transport and storage.
Iron powder is safer and cheaper to transport than ammonia, which also needs a pressurized tank and would be a major disaster if it spilled. Reprocessing rust back into iron using hydrogen is also orders of magnitude more efficient than converting hydrogen into ammonia.
All iron powder needs for transport is a shipping container full of nitrogen gas, with a rubber gasket to keep it somewhat air tight. If it spills its just a pile of rocks.
And if the source of renewable energy is co-located with the electrolysis plant, the rust recharging plant, and the thermal power plant, the cycle's excess O2 from electrolysis and nitrogen gas production can be pumped into the burner of the power plant, increasing efficiency and eliminating nitric acid pollution.
That's true for older magnetorquers, because the Earth's magnetic field is smooth enough that the difference between field strength at the top and bottom of the satellite is insignificant.
With superconductors you can scale up the magnetic field strength enough to get a usable net linear force.
Every once in a while, declare sausage. It confuses the hell out of your enemies.
--Rule of Acquisition #76
"I have never wished a man dead, but I have read some obituaries with great pleasure."
--Abraham Lincoln
The purchase price was historically low due to the libelous accusations of acetaminophen causing autism.
Investing in corruption pays off bigly when Republicans manage to ooze their way into office.
The eggs are from these flappy guys:

This is a Bash fork bomb, a malicious function definition that recursively calls itself:
:() — defines a function named : (yes, just a colon).
{ :|:& } — the function's body:
:|: — pipes the output of the function into another call of itself, creating two processes each time.
& — runs the call in the background, meaning it doesn’t wait for completion.
; — ends the function definition.
: — finally, this invokes the function once, starting the bomb.
lol, as if Harvard were liberal
they're infamously, thuggishly conservative
Ukrainian farmer: "How do I put this hunk of junk into Neutral so I can load it onto my trailer?" *starts an argument on War Thunder forums*
Delta_V
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Source for claim of 1% mass loss per cycle:
https://research.tue.nl/en/publications/combustion-of-micron-sized-iron-particles-in-a-drop-tube-reactor/
I think the deciding factor between iron and aluminum comes down to exhaust filtration.
Iron oxide in the exhaust can be collected cheaply with a combination of centrifugal and electrostatic forces and it tends to retain is grain size. Aluminum oxide is lighter, more electrically resistive, and tends to break down into too-small nanoparticles.
Yeah, you'd only need to sinter pellets to pump hydrogen through them in a static pile. A fluidized bed reactor can reduce the iron oxide powder as is, and keeping the temperature lower prevents sticky sintering at the cost of taking longer to complete.