For Questions That Don't Merit Their Own Thread

[TheSaint]

7 minutes ago, Shpaget said:

Aren't we out of Pu238? As in, down to low double digit kg worldwide? Wasn't already New Howizon project struggling to procure enough of it?

If my memory serves me, and this is correct, we just can't send more probes because Pu shortage sets a hard limit on all project that would need it, and everything gouing to deep space needs it

Apparently we started production again a few years back.

https://www.energy.gov/ne/articles/oak-ridge-national-laboratory-automates-key-process-plutonium-238-production

 

[mikegarrison]

The MMRTG for Perseverance used almost 5 kg of Pu-238, so it must not be impossible to source.

[DDE]

14 hours ago, JoeSchmuckatelli said:

Given that the real risk to mission is the launch (boom), followed by a lower chance of failure to wake up

Unfortunately, of we're thinking about Soviet electronics, the latter seems to predominate.

8 hours ago, mikegarrison said:

and also potentially used in military applications (bombs)

That's Pu-239, not Pu-238.

8 hours ago, mikegarrison said:

The MMRTG for Perseverance used almost 5 kg of Pu-238, so it must not be impossible to source.

Ostensibly it used a large chunk of the available stockpile.

[AHHans]

9 hours ago, mikegarrison said:

It's quite toxic and also potentially used in military applications (bombs), so maybe that's an issue.

Pu-238 is not used to build nuclear bombs, that's Pu-239. But both isotopes are produced in the same kind of facilities, and in the US case used to be produced in literally the same facility (the  Savannah River Site). So when the US military closed down their Pu-239 production facility NASA had to pony up for their own Pu-238 production site.

[Shpaget]

9 hours ago, mikegarrison said:

It's an artificially created element, so surely we could make more.

It's quite toxic and also potentially used in military applications (bombs), so maybe that's an issue.

It's not a matter of can we make more, it's about cost of reactivating facilities, and politics around the whole thing, since funding anything nuclear sooner or later becomes political.

As DDE said, Pu-238 is not suitable for bombs. There are military applications, of course, but pretty much exclusively for RTGs.

9 hours ago, TheSaint said:

Apparently we started production again a few years back.

https://www.energy.gov/ne/articles/oak-ridge-national-laboratory-automates-key-process-plutonium-238-production

 

That's good to hear, although 400 g per year is not a whole lot.

So I did a little more reading, and apparently most of the available US stockpile is not meeting NASA specs for RTGs, but could still be used if enriched with some high quality newly produced stuff (couldn't find numbers on ratio of new to old needed).

I found this PDF by Idaho National Laboratory. Mind you it's from 2005, so a bit outdated.

https://web.archive.org/web/20110928034832/http://nuclear.inl.gov/spacenuclear/docs/final72005faqs.pdf

Page 3 has a table of available stockpile, as of that time, and it was only 39.51 kg of Pu-238. Since then, about 8 kg was used for New Horizons, 5 kg for Perseverance, meaning available amount is down to 27. Of that remaining 27 kg, about 3 kg was lost to decay.

So US has only enough for a handful RTG, plus some for ground testing/calibration.

Not so bad news is that there's 300 kg of Neptunium-237, which is used to make Pu-238, but that is still not a whole lot.

[Admiral Fluffy]

Kind of off topic, but in KSP is it moons or muns?

Because we call them the moons of Jupiter, would the kerbals call them the muns of Jool?

[kerbiloid]

For Kerbals - muns, for humans - moons.

[JoeSchmuckatelli]

OK - but do they have an analogous term from some of their ancient, warlike ancestors to 'lunar'? 

 

(Munar is cheating) 

[Shpaget]

Loonar?

[Admiral Fluffy]

2 hours ago, JoeSchmuckatelli said:

OK - but do they have an analogous term from some of their ancient, warlike ancestors to 'lunar'? 

 

(Munar is cheating) 

Possibly. I like what @Shpagetsaid in the above post.

[kerbiloid]

And how do they call LEM.

[Admiral Fluffy]

10 hours ago, kerbiloid said:

And how do they call LEM.

M.E.M.

Munar Excursion Module

[K^2]

11 hours ago, Admiral Fluffy said:

M.E.M.

Munar Excursion Module

Certainly puts a new twist on doing things for the MEMes.

[JoeSchmuckatelli]

We need a 'groan' button, apparently 

[AHHans]

No puns please! Because in space no one can hear you groan!

[Lisias]

9 hours ago, AHHans said:

No puns please! Because in space no one can hear you groan!

On the other hand, you can save some EVA fuel on the stunt...  

Spoiler

"I am Iron Man!"

 

Edited June 17, 2021 by Lisias
better video

[kerbiloid]

Why are the most "physically realistic" movies (like the Martian, the Interstellar) are... in so complicated relations with fizzix?

Edited June 18, 2021 by kerbiloid

[wumpus]

13 hours ago, kerbiloid said:

Why are the most "physically realistic" movies (like the Martian, the Interstellar) are... in so complicated relations with fizzix?

I'm guessing that you are dealing with "fractal accuracy".  You get the main points accurate, but now have a lot of minor points that will only be accurate if great care is taken to get them right.  If great care is taken, then there are even more more minor points to get right.  And so on and so on.  Not only  that, but after getting the main points right, there's no particular reason for the secondary points to be part of the same narrow discipline as the first.  Meaning that very few people will have the background knowledge to get them right, even if "great care is taken", you'd have to find consultants (and even then you have to have a gut feel for the right fields that could have problems with your plot points).

There's a reason the golden age of science fiction is 10-14.  By the time you get to college, expect to know more about at least one field [which field may depend as much on the author as your education] than any author you might read (a favorite author of mine had the misfortune to write a book heavy in orbital mechanics right after the release of KSP.  I'm sure I'm not the only fan of both...).  You *will* see errors, if not in the physics, at least in other basic sciences.

And that's sci-fi genre fiction, which traditionally cares about getting the science right (at least up until the 1970s, but there are a few carrying the old school traditions).  Movies never really cared, and after Star Wars' runaway success is likely to be even hostile to accuracy.  There was a "script explanation" going around mentioning that all the Star Trek science consultants do is put the right words in the technobabble.  The script says

"shouldn't we just tech the tech?" 

"no, you have to tech the tech first, then you can do that".

"ok, lets do it.

And when the script comes back, the "tech the tech" has been replaced with reasonably appropriate science/technological words.

[magnemoe]

1 hour ago, wumpus said:

I'm guessing that you are dealing with "fractal accuracy".  You get the main points accurate, but now have a lot of minor points that will only be accurate if great care is taken to get them right.  If great care is taken, then there are even more more minor points to get right.  And so on and so on.  Not only  that, but after getting the main points right, there's no particular reason for the secondary points to be part of the same narrow discipline as the first.  Meaning that very few people will have the background knowledge to get them right, even if "great care is taken", you'd have to find consultants (and even then you have to have a gut feel for the right fields that could have problems with your plot points).

There's a reason the golden age of science fiction is 10-14.  By the time you get to college, expect to know more about at least one field [which field may depend as much on the author as your education] than any author you might read (a favorite author of mine had the misfortune to write a book heavy in orbital mechanics right after the release of KSP.  I'm sure I'm not the only fan of both...).  You *will* see errors, if not in the physics, at least in other basic sciences.

And that's sci-fi genre fiction, which traditionally cares about getting the science right (at least up until the 1970s, but there are a few carrying the old school traditions).  Movies never really cared, and after Star Wars' runaway success is likely to be even hostile to accuracy.  There was a "script explanation" going around mentioning that all the Star Trek science consultants do is put the right words in the technobabble.  The script says

"shouldn't we just tech the tech?" 

"no, you have to tech the tech first, then you can do that".

"ok, lets do it.

And when the script comes back, the "tech the tech" has been replaced with reasonably appropriate science/technological words.

Agree, now the Martian was very hard,  no an storm on Mars would not knock over an rocket and the soil is poisons but ignore that, I did not like the ending much however. 

For fantasy and I lump both Star Wars and Trek here you only need fantasy level plausibility. 1) Why has none tried this before as in hyperspace ramming. 
2) is check and balance, the enemy will always counter your tactic. Two exceptions, one is spears against machine guns, second is overwhelming force as in 1944-45. Battleship Texas engaging snipers at Normandy is one marker second is that most of the world battleships was doing shore bombardment there 

[southernplain]

3 hours ago, wumpus said:

I'm guessing that you are dealing with "fractal accuracy".  You get the main points accurate, but now have a lot of minor points that will only be accurate if great care is taken to get them right.  If great care is taken, then there are even more more minor points to get right.  And so on and so on.  Not only  that, but after getting the main points right, there's no particular reason for the secondary points to be part of the same narrow discipline as the first.  Meaning that very few people will have the background knowledge to get them right, even if "great care is taken", you'd have to find consultants (and even then you have to have a gut feel for the right fields that could have problems with your plot points).

Also cost. Filming something close to accurate might cost X. Getting it more accurate costs X+Y (especially with science fiction).

Unless it is hyper important to the plot, it generally isn't worth the extra expense. Good enough will fit in the budget, great might not.

Case in point, they didn't try to simulate a 1/3g environment in the Martian. The differences are small and the cost and complexity are very high for no real benefit to the plot.

[SOXBLOX]

IDK if anyone's posted this yet, but... This is hilariously specific.

[DDE]

7 minutes ago, SOXBLOX said:

IDK if anyone's posted this yet, but... This is hilariously specific.

It answers another question I had when seeing snippets gained from the report: why was I hearing about tactical hypersonics when the report was about GBSD:

Quote

The complete assessment is wide-ranging, detailing the environmental and ecological impacts of tests related to the Ground Based Strategic Deterrent (GBSD) program, which is set to eventually replace the aging Minuteman III ICBM. The environmental impact report also references other environmental assessments conducted in conjunction with the National Marine Fisheries Service (NMFS), including those that were conducted ahead of the ARRW testing. 

 

[magnemoe]

On 6/15/2021 at 9:36 AM, AHHans said:

Pu-238 is not used to build nuclear bombs, that's Pu-239. But both isotopes are produced in the same kind of facilities, and in the US case used to be produced in literally the same facility (the  Savannah River Site). So when the US military closed down their Pu-239 production facility NASA had to pony up for their own Pu-238 production site.

This, note that US has more plutonium 239 than they know that to do with, amount as increased as many nuclear bombs has been deactivated. 
US bought some Pu-238 from Russia earlier. 

[Flying dutchman]

how do they keep the water for the water delluge system for a rocket launch liquid at freezing temperatures?

[DDE]

2 hours ago, Flying dutchman said:

how do they keep the water for the water delluge system for a rocket launch liquid at freezing temperatures?

Electric heaters or central steam heating, I imagine. After all, they keep the rest of the launch facility at above freezing temperatures in Moscow, Voronezh or Baikonur.