For Questions That Don't Merit Their Own Thread

[DDE]

2 hours ago, razark said:

Interesting question that I have not seen any info on.  I know a number of wooden-hulled ships were used in WWII, so an investigation into patrol reports from the era might provide some insight.  If anything later has been declassified, seek it out.

I don't think WWII is representative because submarines used active sonar sparingly, if at all.

[magnemoe]

On 12/23/2019 at 11:32 PM, DDE said:

Citation needed. It is my understanding that there are no "standard" shells for it to use.

 

True, note that modern naval guns uses an cartridge like small cannons and handguns does. 155 mm uses separate shell and  powder canisters as an cartridge would be to heavy to man-handle effectively and require an much larger turret. than is practical on an self propelled gun. 
However making changes to the shell so it work in an cartridge way easier compared to converting an 155 mm or 5" to 4" for naval guns, minor changes to the body of the shell and figure out the new ballistic. 

I belive the real reason is doctrine , the same reason why many self propelled artillery guns does not have an sight for direct fire even if can be useful, even life saving if you are attacked. 
Its tempting to use an self propelled gun as an tank or assault gun if you have it and self propelled guns are not armored like an tank, its only protected against splinter and hand weapons. 

If you have standard shells on an Zumwalt destroyer it will be tempting to take it in close and use the guns in an target rich environment, however Zumwalt is not an battleship it depend on stealth and long range to keep itself safe. 
So it be much like direct fire sight on self propelled artillery. 
More so in that its multiple projects around for extended range for artillery. 

[razark]

5 hours ago, DDE said:

I don't think WWII is representative because submarines used active sonar sparingly, if at all.

True, but it's a situation where your set of available data is likely to be low.

[Guest]

Question, how does exploring space (mostly the solar system) manage to be economically viable to space agencies, since there's not really any profit from it? Is it done for the sake of it, or to create more jobs?

I can see that doing research to then make a product based on it can be lucrative, but I've yet to understand how research such as the what's the soil composition on Mars, or what's Jupiter's magnetic field's strength have a financial return.

Another field I'm curious about (same question) is astronomy, I haven't figured out how observatories and such manage to make income (I'm guessing they're paid by researchers by demand, but then again, how does that research achieve economic viability?)

note to staff: this is not a political post and is in no way meant to start discussions about what governments should or shouldn't invest in (just in case)

Edited December 26, 2019 by Guest

[razark]

17 minutes ago, Aperture Science said:

Is it done for the sake of it, or to create more jobs?

Yes.

Gaining more knowledge about the universe we live in and how it all works together can be a goal in itself. 

It also does provide jobs.  And in some cases, the jobs provided keep your rocket scientists from becoming your enemy's missile designers.

[magnemoe]

31 minutes ago, razark said:

Yes.

Gaining more knowledge about the universe we live in and how it all works together can be a goal in itself. 

It also does provide jobs.  And in some cases, the jobs provided keep your rocket scientists from becoming your enemy's missile designers.

This, now keeping jobs for foreign rocket scientists was an issue back in the 1990's but it gave the US the shuttle-Mir program who was very successful. 

Note that stuff like solar weather is important for satellite operations once we started to depend on them. 
Studying the atmosphere on Mars, Venus and Titan is probably useful as its give more data points for atmospheric models. 
Finding asteroids on an collision trajectory is an work job until its an emergency, or more likely prospecting. 

Its also national prestige or why we landed on the moon. Current time you want to be in the G7 club so you farm achievement points.
 

[kerbiloid]

The fundamental science is a long-term investition, with no quick payback.

It's for growing your own applied science, which forms your own engineering culture, which grows your own engineers.

Other its payback is negligible.

[DDE]

How would I be to prove the "2" in H2O if questioned?

A silly idea, but I realize I don't know/remember how to.

[kerbiloid]

4 minutes ago, DDE said:

How would I be to prove the "2" in H2O if questioned?

The water consists of oxygen and hydrogen, too /tu:/.This "2" means that "too", 4YI.

Edited December 27, 2019 by kerbiloid

[Guest]

12 hours ago, DDE said:

How would I be to prove the "2" in H2O if questioned?

A silly idea, but I realize I don't know/remember how to.

Hydrogen needs 2 electrons to be stable, and oxygen needs 8 (in its valence shell - octet law). Hydrogen starts out with only one, and oxygen has six - two hydrogen atoms make covalent bonds to a singular oxygen atom (i.e. share electrons, +1 electron for both atoms per bond), resulting in H-O-H, which is water.

 

Either that or you can just say it's because the number of atoms comes in front of the element's symbol, since it's a convention; if it was the opposite it would just be 2HO

Edited December 27, 2019 by Guest

[wumpus]

17 hours ago, DDE said:

How would I be to prove the "2" in H2O if questioned?

A silly idea, but I realize I don't know/remember how to.

Mostly by determining atomic weights and then showing that it takes twice as many moles of Hydrogen per mole of oxygen.  Showing that hydrogen has an atomic mass of "1" is pretty tricky, as molecular hydrogen almost always wants to combine with just about anything (including itself).  Oxygen is also tricky, but I suspect easier than hydrogen (and once you figure out that trick, it will probably work with oxygen).

- A chemistry teacher once mentioned that monotomic hydrogen would be roughly as effective as a nuclear rocket (I'm assuming a ~3 digit Isp, we were freshmen students, not rocket scientists so there wasn't any more explanation).

[kerbiloid]

Put a piece of lime into water and compare the mass.

You'll see that CaO + H2O → Ca(OH)2

 

Edited December 28, 2019 by kerbiloid

[ARS]

Is it possible to build a nuclear reactor cooled without any pumps and rely solely on natural convection of it's cooling water (hot water rise to be cooled on radiators before fall back into the reactor when it's cooled). Is it practical from functionality perspective?

[kerbiloid]

It's possible to build a nuclear reactor without any cooling at all, just its power matters.

Spoiler

P.S.
The ladder is by design, it's for maintenance.

Edited December 28, 2019 by kerbiloid

[DDE]

1 hour ago, ARS said:

Is it possible to build a nuclear reactor cooled without any pumps and rely solely on natural convection of it's cooling water (hot water rise to be cooled on radiators before fall back into the reactor when it's cooled). Is it practical from functionality perspective?

AFAIK every cooling medium option has had a convection-cooled design variant built for it. Helps with both safety and, on submarines, noise reduction.

[Spacescifi]

. What rocket nozzle is best for SSTO applications that is NOT an aerospike?

I say this since aerospikes have too many problems and are needlessly complex.

 

Assume the rocket engine is one of these in descending order:

Generation I: Nuclear Thermal rocket utilizing an air propelled ramjet once it is up to speed. Uses liquid methane as propellant

Generation IV: Antimatter enhanced thermal rocket. Uses liquid methane propellant and an air propelled scramjet once up to speed.

 

My conclusions: A simple but oblong cone would probably work best, as over expansion happens at high altitude, and at launch a wide nozzle would have under expansion which lowers thrust as I understand it in either case. Bells are good for avoiding over expansion, but are bad for launch at low altitude. Cones are lower thrust at high altitude and vacuum, but if your engines are powerful enough is that not nearly irrelavent?

 

Correct me where needed. Thanks.

[Okhin]

Since there's a "close enough" second star in our own solar system (Jupiter, it just lacks a bit of mass to ignite fusion and become a star if I got that right), I'm wondering what a planetary system would looks like if there's a second distant star from the first one. Distant as in "I can pack planet and asteroids in between them". And what would be the respective size of those two stars if the gravitational center of those two center lies within the central one (which would then slighty oscillate, instead of spinning around its own axis).

I know there's binary or ternary stars system, with one or two star close to each other (and a lot of them are on a colliding course iirc), but I'm more thinking about a star behaving as a planet.

[magnemoe]

4 hours ago, Okhin said:

Since there's a "close enough" second star in our own solar system (Jupiter, it just lacks a bit of mass to ignite fusion and become a star if I got that right), I'm wondering what a planetary system would looks like if there's a second distant star from the first one. Distant as in "I can pack planet and asteroids in between them". And what would be the respective size of those two stars if the gravitational center of those two center lies within the central one (which would then slighty oscillate, instead of spinning around its own axis).

I know there's binary or ternary stars system, with one or two star close to each other (and a lot of them are on a colliding course iirc), but I'm more thinking about a star behaving as a planet.

It 50% of the size to be an brown dwarf but that would just be a bit too hot planet by now. for an real star you need 81 times Jupiters mass, that is more than the difference between you and an elephant. 
And the extra mass is the problem as it would change how the inner solar system formed, we would not have an asteroid belt for sure outside of the Jupiter trojans.
On the other hand Alpha Centauri is two roughly sun sized stars orbiting each other at saturn to pluto distances 

I guess Alpha Centauri could still have their own inner solar systems and might even share an Kuiper belt
The other star would work much like the moon, it give light, think full moon levels but no noticeable heat. 
Like the moon it would affect how much light you get at night but would be more longer lasting as the secondary sun moves slowly. 

[Okhin]

Thanks

But why a brown dwarf would be too small ? (I'm bad at star sizes :/), is it because it would not emit any light ? Or something like that? Also, I was really wondering what would be the size ratio (and mass) of two star in a setup where one would be a satelite of the other. Like a giant red, for instance, as the main star.

[Wjolcz]

If this is accurate:

Then we would probably not feel any heat from the red dwarf at all. The inner and outer solar system would be a total mess though. Jupiter itself tugs on the Sun in a way the gravitational center of our solar system is just above the Sun's surface. I can imagine adding 80 more Jupiters would move the CoG quite a bit.

 

Edited December 30, 2019 by Wjolcz

[magnemoe]

9 hours ago, Okhin said:

Thanks

But why a brown dwarf would be too small ? (I'm bad at star sizes :/), is it because it would not emit any light ? Or something like that? Also, I was really wondering what would be the size ratio (and mass) of two star in a setup where one would be a satelite of the other. Like a giant red, for instance, as the main star.

An brown dwarf is perfectly sized for being an brown dwarf
However I assumed you wanted planets with life around the second sun and for this you need at least an red dwarf. 

[ARS]

Is there any method to determine nuclear bomb's yield based on the depth of the crater it forms at ground zero? More specifically a crater depth of 600 m (assuming that it forms a perfect hemispherical-shaped crater with a diameter of 1200 m), the blast takes place on ground level, not airburst, location of ground zero is large city, soil condition is typical soil of large cities

[DDE]

17 minutes ago, ARS said:

Is there any method to determine nuclear bomb's yield based on the depth of the crater it forms at ground zero? More specifically a crater depth of 600 m (assuming that it forms a perfect hemispherical-shaped crater with a diameter of 1200 m), the blast takes place on ground level, not airburst, location of ground zero is large city, soil condition is typical soil of large cities

The diameter is 38 times square root of blast energy in kilotons, according to one random source. Depth is 7-10 times smaller than the diameter - hemispherical craters are physically near-impossible.

Nukemap et al should have documentation for their models that might help you out with more elaborate formulae.

Edited December 30, 2019 by DDE

[kerbiloid]

Maybe not square root, but a cubic root.

As the well-known "standard" 1 Mt crater is 380 m in diameter, 90 m from the wall top to the pit bottom.

Edited December 30, 2019 by kerbiloid

[tater]

https://arstechnica.com/science/2019/12/apollo-flight-controller-101-every-console-explained/