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[bloop_bleep]

same as pouring sand on a chick trapped in a pipe, the chick keeps moving to stay on top and poof it's out

I wish I had Max™'s elaborate yet seemingly efficient lady-obtaining powers.

[Max™]

You need a lot more sand and a larger pipe for that kind of chick, my lady-obtaining powers amounted to unloading my lifetime supply of smoothness in a chatroom 17 years ago this June.

It does make sense though that having the lifted material pushing against the sides/the rest of the material as it slides up the ramp should be less damaging than having the ramp spin it up forcefully because the spinning case should let the material lift itself while remaining more loosely packed.

Perhaps the comparison should be moving the broom vs moving the dustbin? A spinning screw is the moving dustbin, while spinning the case lets the rest of the material act as a broom that is only as hard as itself, and less likely to crush and grind stuff up.

[McTraveller]

It's definitely an interesting engineering exercise.  First of all, despite what the video says, it's not a completely symmetric situation: there are real differences between spinning the inner screw versus spinning the outer shaft which can be detected by a difference in the pressure distribution in the material being moved - rotating reference frames are NOT inertial so it is possible to tell if you are in a rotating frame or not.  One key difference is that in the rotating case, the bulk material exits with a notable angular velocity.  This means the transfer of energy is from different mechanisms.

NOTE: none of this means one way is "better" than the other - it's just saying there are real physical differences between the operating mechanics of both machines.

[Reelya]

It's definitely an interesting engineering exercise.  First of all, despite what the video says, it's not a completely symmetric situation: there are real differences between spinning the inner screw versus spinning the outer shaft which can be detected by a difference in the pressure distribution in the material being moved - rotating reference frames are NOT inertial so it is possible to tell if you are in a rotating frame or not.  One key difference is that in the rotating case, the bulk material exits with a notable angular velocity.  This means the transfer of energy is from different mechanisms.

NOTE: none of this means one way is "better" than the other - it's just saying there are real physical differences between the operating mechanics of both machines.

What if the entire machine is loaded onto a platform that's spinning opposite the case? Then from your point of view, it's the case that's static and the screw is spinning again?

[McTraveller]

Ooh nice: from the perspective of an inertial frame the case is stationary but the platform and screw are rotating - this is actually a third configuration.  We have now listed:

1. Traditional:  "bulk material" and platform and case in the same inertial frame, screw rotating.
2. "New": bulk material, platform, and screw in the same inertial frame, case rotating.
3. "Reelya's crazy newness":  case in an inertial frame, the bulk material and platform and screw in the same rotating frame.

I think there are these other two configurations to round it all out:
4. Case, bulk material/platform, and screw all in different rotating frames.
5. Case and screw rotating, bulk material and platform inertial.

Actually number 5 is the same behavior as the traditional.  Which is interesting.  Which leads me to believe: technically if you have a rotating case with scoops, you don't need the internal screw at all (although for solid materials it helps a lot). In fact, rotating case with inlet scoops and no screw is a just low performance turbopump.


EDIT: If the case is rotating relative to the bulk material, the scoops create a ram pressure effect due to the relative motion.  This pressure is the force that drives the material up the pipe.  In this configuration, the "pressure" of the material against the screw is a reaction, it is not the "driving" force - this can be shown by a free body diagram.

EDIT: IMAGES!!!  If you "unroll" the screw, you get a wedge.

Traditional screw pump: the wedge moves, creating its own ram pressure to raise the material:

Spoiler (click to show/hide)

"New" screw pump:  the wedge doesn't move, so something has to push the material up the wedge.

Spoiler (click to show/hide)

When the case is spinning, the "push" for this comes from the ram pressure of the scoop moving.

What these diagrams can't show is that the scoop version can only make pressure in the "wedge" direction by first making pressure in the tangential direction (into or out of the page for these drawings).  This tangential motion requires a radial pressure gradient to keep those particles moving in a circle; this pressure gradient is NOT present in the traditional screw, because the motion of the wedge is always in the "wedge" direction - it doesn't need tangential motion.

This is a fun digression   

[Bumber]

We must demand that Toady One implement "new" screw pumps alongside the existing ones.

[Max™]

Yeah, taking the idea apart into a wedge and a wall was why the claim it made less dust seemed plausible, that tangential pressure is going to get applied against the other moving materials which are less likely to crush each other than the total forces coming exclusively from the wedge.

I suspect that's the same reason stuff comes out along the rim when the screw passes it and cycles around normally while spinning the case makes it scatter from the entire rim, all the rest of the material is lifting/scattering vs the presence of the screw causing material to pile up and fall off.

[KittyTac]

Odd, I thought I'd have posted in this thread before. Anyways, as much as I dislike Trump, this is good: https://www.space.com/trump-moon-mining-space-resources-executive-order.html

The Moon and asteroids are obviously uninhabited, therefore they are OK to use environmentally-disrespectful-but-effective mining techniques on. The Moon holds vast amounts of fresh water (in form of ice) and is easier to launch rockets from, while asteroids might have metal ores.

Though it would have been better if it wasn't just America. I hope other countries will soon follow with similar projects.

[Reelya]

I don't think it's good. It's a bad idea to open space up to unilateral plunder. That will cause a huge arms race.

Also, sending up corporations into space to plunder as they see fit is pretty much the dystopian future we don't want. Say hello to a future of corporate feudalism if we allow that.

[Iduno]

I don't think it's good. It's a bad idea to open space up to unilateral plunder. That will cause a huge arms race.

Also, sending up corporations into space to plunder as they see fit is pretty much the dystopian future we don't want. Say hello to a future of corporate feudalism if we allow that.

Correct.

The Moon holds vast amounts of fresh water (in form of ice) and is easier to launch rockets from, while asteroids might have metal ores.

Moon is haunted.

[McTraveller]

I have a great sadness of thinking of looking up at the moon someday and seeing city lights*.  I think they should pass a law that human activity on the moon should be limited to the far side.

Other people, of course, think of such a thing would be awesome; a testament to human ingenuity and such.  They would think looking up at a "populated" moon would be cool.

*Yes I know you'd only be able to see them when not illuminated by the sun.  But I don't want to look up at a new moon and see human settlements. I like the dark disk, unsullied by human touch.

It's much akin to my dismay when they level forests or natural areas around here to put in a new shopping center or subdivision.  I want to see nature, others want to see "progress."

[Reelya]

Pepsi planned to project a giant Pepsi logo into the night sky, and I bet your against that too. You're against freedom.

Let's face it, every square inch of stuff your eyes look at that's not covered in advertising is wasted space.

https://futurism.com/pepsi-orbital-billboard-night-sky

A Russian company called StartRocket says it’s going to launch a cluster of cubesats into space that will act as an “orbital billboard,” projecting enormous advertisements into the night sky like artificial constellations. And its first client, it says, will be PepsiCo — which will use the system to promote a “campaign against stereotypes and unjustified prejudices against gamers” on behalf of an energy drink called Adrenaline Rush.

Yeah, the project sounds like an elaborate prank. But Russian PepsiCo spokesperson Olga Mangova confirmed to Futurism that the collaboration is real.

“We believe in StartRocket potential,” she wrote in an email. “Orbital billboards are the revolution on the market of communications. That’s why on behalf of Adrenaline Rush — PepsiCo Russia energy non-alcoholic drink, which is brand innovator, and supports everything new, and non-standard — we agreed on this partnership.”

[Naturegirl1999]

I;d rather not have our sky be used as yet another tool for companies to use to manipulate the masses

[Iduno]

I;d rather not have our sky be used as yet another tool for companies to use to manipulate the masses

Burn down the sky before Pepsi can take it from us.

[MaxTheFox]

I mostly agree with KT. Especially since I hardly see the Moon's nature as beautiful. And yes, I would think a populated Moon would be cool. Also Mars. We have no real evidence of any advanced extraterrestrial species, therefore I believe space is all ours to exploit and colonize until proven otherwise.