For Questions That Don't Merit Their Own Thread

[munlander1]

I know to go down to the Antarctic base you have to get your appendix removed. To go to space, do you have to get it removed? Has there ever been surgery performed in 0g?

[kerbiloid]

(About the xkcd picture)

Probably, there is a Daedalus developer to the right. He prefers Barnard Star as the first interstellar objective.

***

Once a crew has been returned due to the prostatitis, another time with the heart problems.

Unlikely the appendicitis appends something.

Edited December 1, 2018 by kerbiloid

[magnemoe]

On 11/30/2018 at 8:59 PM, mikegarrison said:

Read this 3 times before getting it. 
And yes we live in an one star system  

[NSEP]

16 hours ago, munlander1 said:

I know to go down to the Antarctic base you have to get your appendix removed. To go to space, do you have to get it removed?

No. Apparently antibiotics are a better choice.

https://www.quora.com/Is-it-true-that-astronauts-have-to-have-their-appendix-removed-before-going-into-space

16 hours ago, munlander1 said:

Has there ever been surgery performed in 0g?

Yes!

https://www.newscientist.com/article/dn10169-doctors-remove-tumour-in-first-zero-g-surgery/

Can you use Oxygen as reaction mass for a nuclear thermal rocket? If so, what would the Isp be?

[K^2]

2 hours ago, NSEP said:

Can you use Oxygen as reaction mass for a nuclear thermal rocket? If so, what would the Isp be?

Yes, but you probably don't want to. Since oxygen is 16 times heavier than hydrogen, at the same energy per molecule, you'll have four times less impulse, so a quarter of I_SP. However, there are some smaller differences between oxygen and hydrogen, such as thermal conductivity, differences in critical velocity of the flow, and even the ratio between energies of various excited states that will play into it. So I don't expect the difference to be exactly a factor of four, but rather somewhere in that region. That said, it's not going to be much better than a quarter. You really do want the lightest propellant you can get with NTR, and the only gas that's even close to hydrogen's mass is helium, being "only" twice as heavy.

[kerbiloid]

7 hours ago, NSEP said:

Can you use Oxygen as reaction mass for a nuclear thermal rocket? If so, what would the Isp be?

Yes (though Air, not pure Oxygen), if you are orbiting in LEO and from time to time dive to scoop some air with air scoops.
Then you have the air as an oxidizer or a propellant for a nuke,

Such projects have being researched in 1950s-60s.

P.S.
Imho it's a bad idea to use that air for something with ISP*g < 7900 m/s..

Edited December 2, 2018 by kerbiloid

[Green Baron]

How is Korolev pronounced correctly, Korolev or more like Korolyev, and is the emphasis on the first or second syllable ?

Spaciba :-)

Edited December 3, 2018 by Green Baron

[Gargamel]

I usually pronounce it Korolev, like the cat. 

[K^2]

4 hours ago, Green Baron said:

How is Korolev pronounced correctly, Korolev or more like Korolyev, and is the emphasis on the first or second syllable ?

Emphasis/stress on last syllable, actually. I'd transcribe it as Korol'ov. 'R' is thrilled. I think Spanish uses the similar thrilled r's, but I'm not positive. The 'L' is soft (hence apostrophe). It's the same kind of 'L' that you'd usually find before the 'ee' sound in a lot of languages, hence the 'y' showing up in transcriptions and when some people try to pronounce it. But the actual vowel letter on the last syllable is 'ё'. It's pronounced as 'yo' by itself, but following a consonant, the 'y' portion is dropped and it softens the consonant instead. So it's an 'o' sound, despite the common transcription putting in 'e' instead. The later is due to the similarity of the symbol. Indeed, in Russian we'd often skip the dots over 'e'. (The fact that ё is terribly positioned on Russian keyboard layout only made the trend worse in the last decades.) There should not be a 'y' or 'ee' sound anywhere in pronunciation of that name. Depending on dialect, the first two 'o' sounds could be closer to 'a' instead, but that's details. Pronouncing all three syllables with an 'o' sound is certainly correct.

Edit: My explanation might be a bit lacking, and the soft 'L' might be hard either way. If you pronounce 'Korolov' with stress on the last syllable, you'll already be closer than most non-Russian speakers.

Edited December 4, 2018 by K^2

[ARS]

On polar region, where the ice sheet's thickness is sufficient for submarines to break through, is it possible for ground forces on the ice sheet to detect submarine lurking beneath the ice sheet by "listening" the ice sheet?

[K^2]

1 hour ago, ARS said:

On polar region, where the ice sheet's thickness is sufficient for submarines to break through, is it possible for ground forces on the ice sheet to detect submarine lurking beneath the ice sheet by "listening" the ice sheet?

Possible, yes. Practical, probably not. You'll be losing a lot of acoustic intensity from ice-water interface, any bubbles of air trapped bellow or in the ice, and any cracks or imperfections in ice itself. It's unlikely that you'll be sitting on top of a perfectly smooth, solid sheet of ice. Physics says if you cover large enough surface of the ice with microphones you'll be able to compensate, but unless you're trying to pick up the sub sitting directly beneath you and making distinct enough noise, the area you need to cover might become impractically large.

The other problem is localizing the source. Water and ice have very different speeds of sound in them, so if you think natural ice can be hard to see through, it's way worse with sound. Longer wavelength will certainly help, so you won't have to worry about small imperfections and bubbles, but you'll still get crazy lensing due to any surface geometry at the bottom.

To continue the light analogy, looking for a sub through ice is going to be like trying to see somebody on the other side of a stained glass window. Enough light's certainly going through, and if they stand right next to the glass, you can see them clearly enough, but for anything further away, you'll have trouble distinguishing what you're looking for from all the noise. And subs are generally built in pretty well to blend in with the noise.

Again, if you have sufficient surface covered in acoustic pickups, and you've taken the time to map the imperfections, which you can do from the surface by listening to reflected sounds, you ought to be able to compensate both for refraction and for intensity loss and reconstruct the same kind of signal you'd get from a passive sonar submerged in water. At that point, however, drilling a hole in ice and actually submerging a passive sonar, or even just getting a sub of your own into location, is going to be drastically simpler.

[kerbiloid]

(Takes popcorn to follow another submarine acoustics discussion).

Edited December 4, 2018 by kerbiloid

[p1t1o]

7 hours ago, ARS said:

On polar region, where the ice sheet's thickness is sufficient for submarines to break through, is it possible for ground forces on the ice sheet to detect submarine lurking beneath the ice sheet by "listening" the ice sheet?

IIRC, ice sheets make quite a lot of noise as they crack, grind and collide, I think you'd have  tough time.

BUT, if you drilled a hole through to the water you could lower a fully blown sonobuoy down there and get pretty good detection.

However I will eat a metaphorical hat if the sea floor under the arctic ice isnt littered with US and Russian hydrophones already.

[K^2]

9 minutes ago, p1t1o said:

However I will eat a metaphorical hat if the sea floor under the arctic ice isnt littered with US and Russian hydrophones already.

That's probably the best solution right there. If you have business getting military on the arctic ice, odds are, you are either a NATO or ODKB power, and can probably request data on sub movement from one of the above.

[Gargamel]

19 hours ago, kerbiloid said:

(Takes popcorn to follow another submarine acoustics discussion).

Hehehehehee.

Well....

Yeah, it's been said, ice is noisy, really noisy.   Drilling through it would be your best bet.   But the sub would probably hear the drill and skedaddle. 

But as to your scenario, @ARS, only Nuclear boats can travel under the ice for any length of time.   Diesel/Electrics don't have the submerged endurance to pull off such a stunt.    

Edited December 5, 2018 by Gargamel

[DerekL1963]

6 hours ago, Gargamel said:

But as to your scenario, @ARS, only Nuclear boats can travel under the ice for any length of time.   Diesel/Electrics don't have the submerged endurance to pull off such a stunt.

You're a few years out of date...  AIP for submarines has made great strides in the last couple of decades.  They certainly aren't as fast as nukes, but the better ones can currently stay submerged for over a week while doing 4-5 knots.

 

6 hours ago, Gargamel said:

Drilling through it would be your best bet.   But the sub would probably hear the drill and skedaddle. 

Probably not, since the only sensible way to drill through any thickness of ice is with a hot water drill.  Heat the water directly in an externally fired boiler, and you'll only need a fairly small generator for the pumps.

 

On 12/3/2018 at 9:34 PM, kerbiloid said:

(Takes popcorn to follow another submarine acoustics discussion).

Nah, ain't worth it.

[kerbiloid]

4 minutes ago, DerekL1963 said:

Probably not, since the only sensible way to drill through any thickness of ice is with a hot water drill.  Heat the water directly in an externally fired boiler, and you'll only need a fairly small generator for the pumps.

This is exactly what I suggest for the Martian water mining, no drills, only steam jets, only hardcore.

[DerekL1963]

1 minute ago, kerbiloid said:

This is exactly what I suggest for the Martian water mining, no drills, only steam jets, only hardcore.

Hot water drills don't use steam jets - they use hot water to heat a probe body that then melts it's way through the ice.  If Martian water is in the form of large bodies of ice, which they almost certainly aren't, then this would be useful.

[kerbiloid]

2 minutes ago, DerekL1963 said:

Hot water drills don't use steam jets - they use hot water to heat a probe body that then melts it's way through the ice.  If Martian water is in the form of large bodies of ice, which they almost certainly aren't, then this would be useful.

No, I mean to pour the hot water itself after it cools the mining reactor.

(Yes, got it about the metal body.)

Edited December 5, 2018 by kerbiloid

[Gargamel]

16 hours ago, DerekL1963 said:

You're a few years out of date... 

ARS and I have had discussions around a scenario set abouts WWII/Korea Tech levels.   For technology then, the futuristic nucs are the only way to do this. 

[mikegarrison]

[NSEP]

Is the stuff the Phoenix lander uncovered actually waterice? Could it be something else?

[tater]

 

[p1t1o]

Why do cars, at certain low throttle settings, usually in first or low gear, do that "lurching" thing?

My first assumption is that its pilot-induced-oscillation (sudden acceleration lifts my accelerator-foot minutely, causing a sudden deceleration, dropping my foot minutely, causing a sudden forwards acceleration, lifting my...etc.) but it seems to occur even if I force precise control over the accelerator pedal.

[YNM]

35 minutes ago, p1t1o said:

Why do cars, at certain low throttle settings, usually in first or low gear, do that "lurching" thing?

I'm not sure, but on a flat road you can leave the engine on idle (no throttle), press the clutch, engage the first gear (manual) and let the clutch off - it'll roll on itself.

Same applies to automatic - hold the brake, get into drive, let the brake off, and you'll roll without any throttle.

Now get to some empty street and familiarize yourself with this info, and smooth out your throttle control. This was the first familiarization I did when I learned to drive (although on the car I used you need to turn the aircon on to increase the idle rpm enough).

Edited December 12, 2018 by YNM