[Storage of nuclear waste]

1 hour ago, Nuke said:

i think the issue is calling it waste, because most of the isotopes are still useful. part of the process is letting it sit in a pool for a few years to burn off the nasties. once its in dry storage its pretty safe. im always questioning the need for centralized storage. what you do is dedicate a nuclear site to nuclear stuff. when you tear down an old reactor you build a new one in its place. and it might be of a design able to burn up some of the fuel formally known as waste. once we get past that then all you have is medium and low level waste, which is a lot less problematic.

proliferation issues are moot when we get to the point were we can do nuclear weapons without the isotopes. we aren't far from a point where we can do that.

Yeah its a resource, not a waste.  After a few centuries most of the radioactive fission products are gone.  You have a few hot rare earth elements including plutonium remaining.

If we reprocess after cooling in a pool for a few years we have some nasty cesium and strontium that needs to be disposed of or stored safely for centuries, not millennium.  If we reprocess in a few centuries all the radioactive stuff is high value stuff.  The main reasons for not doing it are economic and weapons related.  It's the plutonium that lasts millennium.  

[For Questions That Don't Merit Their Own Thread]

The problem with steel rebar is that once oxygen or moisture gets in, it's game over.  Rust expands and damages the rest.

Ferrocement boats use the best cement available.  But these boats don't last forever.

[Storage of nuclear waste]

 

[Storage of nuclear waste]

It's not that bad.  After 300-500 years it may be a valuable commodity that people want to recover.

[For Questions That Don't Merit Their Own Thread]

1 hour ago, darthgently said:

They should look into farming Black Locust trees for sleepers then.  That wood will last over a century buried in wet ground with no additives and has about the same strength properties as oak (iirc)

I've got lots of Black Locust on my property.  I love it.  It is undoubtedly the best untreated wood for this purpose in North America.  That said it does get crummy with age.  I'm not sure it lasts longer than creosote soaked wood.

However I  doubt is steel reinforced concrete sleepers will last 100 years either.  They tear up and rebuild automobile roads much more frequently than that.  Fiberglass reinforcement might be better than steel from a longevity perspective.

 

[Storage of nuclear waste]

From what I've seen lately there is no need to do nuclear fuel reprocessing right away.  Because new Uranium is cheap.  And reprocessing has inherent weapons grade implications.  But, a few centuries from now the case may be very different.  Or maybe not if fusion makes fission basically obsolete.  In any case the reprocessing gets easier over time as the main fission products like cesium and strontium have half lives of about 30 years.

It might make a lot of sense to plan for eventual recovery of our spent nuclear fuel.  So how would we design spent fuel storage so that somebody in 500 years can easily recover it, but its just as secure as other proposed solutions.

[For Questions That Don't Merit Their Own Thread]

Wooden sleepers are being replaced with concrete here too.  Adding fresh ballast sometimes makes sense.  About half the network of railroads in the US is abandoned.  A few major lines are profitable for long distance bulk transport.  

We have excellent and very cheap passenger service between St Louis and Chicago (100 mph in several sections).  But, I'm told it is not profitable.  Only the service between Washington DC and Boston turns a profit.

[ISS Discussion Thread]

If ISS were crashed into the Moon, would all the debris land back on the lunar surface?

[What Uber Spaceship Laser Cannons Would Actually Probably Look Like...]

I thought they used corundum

[For Questions That Don't Merit Their Own Thread]

I'm wondering whether it is possible to build a scaled down recycling plant.  Recycling forgoes those other ingredients.  There are economies of scale, but also inefficiencies of large scale.  Not knowing the industry, I'm not sure where the sweet spots are.  It depends on how big the equipment is, and how many of each piece of equipment you need.  The other big efficiency would be to turn down the system to just simmer at night and start up easily in the morning.  This could be done by just by holding a full crucible at high temperature all night.    

[For Questions That Don't Merit Their Own Thread]

Double check my math:  900 MW of power from 300W/m2 solar panels is about 3 square kilometers. 

[For Questions That Don't Merit Their Own Thread]

1 hour ago, StrandedonEarth said:

 

Aluminum smelting is an electrolytic process, requiring only electricity. Lots of electricity, hence the nickname “frozen electricity”.  To run a smelter on solar/wind, simply overbuild the renewables and store the excess with pumped hydro for nighttime. 

I like that idea of "frozen electricity".  How much power does a typical commercial aluminum plant use?

[AI. What could go wrong?]

Embracing new fortune cookies might be an improvement over thinking all the answers you need come from a single book.

The timing of the exodus story is not entirely clear.  I find it conspicuous by its absence in the Bible, the fact that Egypt ruled the levant for over a thousand years.  And for part of that the monotheism of the Sun: Amon Ra was the dominant cult.  The cult of Amon Ra was supposedly stronger in the levant than near the Nile.  I think the figure of Moses was cobbled together by a later movement of religious courts.  It had the effect of uniting diverse tribes of people into a single nation.  Perhaps most of which were not descended from people who lived along the Nile, although a few undoubtedly were.   

 

[For Questions That Don't Merit Their Own Thread]

OK, then how much different would it be to recycle aluminum on solar power.   Solar has more capacity than hydro, but you have the issue of nighttime.  How easy is it to speed up or slow down aluminum production?  How big a battery would it take to keep an aluminum plant going over night?

 

Part of the difference compared to steel production is that steel furnaces are mostly heated by fossil fuels directly without requiring electricity.  Do aluminum furnaces burn fossil fuels as well?

[For Questions That Don't Merit Their Own Thread]

  Aluminum is about 5 times the price of steel.  Why is aluminum so much more expensive than steel?

[ISS Discussion Thread]

Too bad the solar panels cannot be recycled.  

Even in lunar orbit there is some air resistance, it would decay and crash over several decades.

[Getting into Lunar Equatorial Orbit]

Inclination changes cost much less fuel if you are at apogee and have a highly elliptical orbit.  It might be possible to set your perigee as low as possible for the intercept.  Take the most elliptical orbit you can.  And do your inclination changes where your speed is minimum.

[How would Kardashev type 3 civilizations try to communicate intergalactic space?]

54 minutes ago, HebaruSan said:

Gauss (1820s AD), not Euclid (300 BC). Only off by two millennia or so.

Lol.  I meant to type Euler and accidentally typed Euclid.  I'll take the correction

[AI. What could go wrong?]

corny 

[How would Kardashev type 3 civilizations try to communicate intergalactic space?]

Well a Kardeshev 3 civilization has multiple Dyson Spheres and laser highways between certain stars.  Would we be able to detect that?  A small sample of Dyson Spheres could easily be mistaken for more distant galaxies behind the object galaxy.  If the average of the galaxy was redder, we would just assume it is farther away.  Right?

 

I think it was Euclid who wanted to send signals to Mars by shaping Siberian forests into Pythagorean triplet triangles (3-4-5, etc).  But if you arranged stars in triangles it would only be an appropriate signal in two directions polar to the galaxy.  

 

[Could We Still Have Enough Food In America If We Stopped Using Pesticides?]

Yes we could easily feed the population without pesticide, but you wouldn't have all the same fruits available all the time at your local grocery store.

[Geologists? Help me with Appalachian Mountains and the Coal Fields]

Still the Appalachians were high altitude unlike the shallow seas at the Illinois and Wyoming basins.  The Appalachian coal is in thinner seams of anthracite coal, whereas the latter two basins are bituminous and much thicker.

[Does Physics Allow For The Creation Of Hyper-Diamagnetic Materials? Or Materials That Can Be Hypermagnetized?]

If you could safely and repeatable quench a superconducting solenoid, you could drive a current of protons at high energy.  Perhaps for propulsion, or proton boron fusion.

[How would Kardashev type 3 civilizations try to communicate intergalactic space?]

It's entirely possible for a Kardeshev type 3 civilization that controls basically one whole galaxy would prioritize a super SETI program.  It could be humans and our robots occupying most of the Milky Way.  Maybe we still have loads of underutilized resources and go into decline anyway.  The idea of colonizing other galaxies seems not just impractical, but unnecessary.  But it would be nice to know if we are alone in the universe or not.

It would take an insane array of lasers to send messages to another galaxy.  Even then the signals take hundreds of millions of years to arrive.  And we're more interested in receiving signals, than in sending them.  There is no reason to assume that a Kardeshev 3 civilization would be visible at intergalactic distances.  But it's possible they want to be.  If so, what messages could they possibly send?

[Side boosters]

Arianne6, falcon heavy, the space shuttle, etc have two side boosters.  The Soyuz had four and was the workhorse of global spaceflight for quite a while.  KSP easily lets me have 6 or 8 side boosters using the same tech as I would need to do 2 or 4.  So why don't we see more side boosters in real life?   What are the best decoupling mechanisms?