Non-mushroom-cloud hydrodynamics

Click For Summary

Discussion Overview

The discussion revolves around the hydrodynamics of a nuclear explosion when detonated from a ballistic trajectory, particularly focusing on the expected smoke and plasma profiles. Participants explore the implications of such a scenario for hard science fiction, while also touching on related topics like crater formation and the nature of scientific inquiry in speculative contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Meta-discussion

Main Points Raised

  • One participant questions the expected profile of smoke and plasma from a nuclear detonation, suggesting it might resemble a "reverse waterfall" due to lower pressure along the projectile's trajectory.
  • Another participant relates the question to crater formation on the Moon, proposing that the symmetry of craters is due to the energy released by explosions overshadowing the momentum of the impacting object.
  • Some participants express skepticism about the relevance of the sci-fi context, arguing that it detracts from the scientific nature of the inquiry.
  • Concerns are raised about the appropriateness of discussing sci-fi scenarios in a physics forum, with some participants suggesting that such discussions often deviate from established physics.
  • A participant expresses frustration over being perceived as unknowledgeable while seeking to create accurate representations of explosions for artistic purposes.
  • Another participant emphasizes the importance of understanding the physics behind hard sci-fi, suggesting that a lack of knowledge undermines the authenticity of the genre.
  • There is a call for moderation regarding the tone of responses, with some participants feeling that the discussion has turned unhelpful or dismissive.

Areas of Agreement / Disagreement

Participants do not reach consensus on the appropriateness of the sci-fi context for the discussion, with some arguing it is relevant while others believe it detracts from the scientific focus. The discussion remains unresolved regarding the expected hydrodynamic behavior of a nuclear explosion in the proposed scenario.

Contextual Notes

Participants express varying levels of knowledge about hydrodynamics and nuclear physics, with some acknowledging their ignorance while seeking qualitative insights. The discussion also highlights the challenges of maintaining scientific rigor in speculative contexts.

itssilva
Messages
54
Reaction score
0
Probably a silly question, but I'm curious because I want to draw some hard sci-fi based on it: if I shoot a nuke "ballistically" (viz., think of firing a cannon at a mountainside), upon detonation, what would be the smoke's/plasma's (?) profile? I guess it wouldn't be the famous mushroom profile, but rather a kinda "reverse waterfall" starting from the projectile's trajectory due to the lower pressure there. Can anyone confirm/rebutt this? X)
 
Physics news on Phys.org
itssilva said:
Probably a silly question, but I'm curious because I want to draw some hard sci-fi based on it: if I shoot a nuke "ballistically" (viz., think of firing a cannon at a mountainside), upon detonation, what would be the smoke's/plasma's (?) profile? I guess it wouldn't be the famous mushroom profile, but rather a kinda "reverse waterfall" starting from the projectile's trajectory due to the lower pressure there. Can anyone confirm/rebutt this? X)
An interesting question. Some while ago I queried why the craters on the Moon all appear circular. The resulting conversation concluded that it involves the same thing you have introduced. The momentum of the missile or the incident meteorite is so much less than momentum changes due to energy released by the explosion that the resulting 'disturbances' will always be symmetrical about the point of impact.
 
  • Like
Likes   Reactions: itssilva
Physicists are prolific children when it comes to playing with their computers, so I wouldn't be surprised at all if someone actually simulated crater formation or fallout hydrodynamics by now; but outta curiosity, on the former, have you ever seen some instance of non-circular crater in some celestial body? There are pretty out-there things tike toroidal planets, as well as miraculously symmetrical things like generic BH formation from dead stars, I suppose
 
Bah, why did this get moved? I only mentioned "I want to use it in sci-fi", not "this is established sci-fi", as the rules require; if I want, I can talk about Special Relativity in my stories, even though SR is real physics, right? And I think this is also real - I believe nukes have been built since the past century, and if we wanted we could blast mountains with them, or not? (sigh don't know where one complains, so nevermind me - but feel like examined by a bot XP)
 
itssilva said:
Bah, why did this get moved? I only mentioned "I want to use it in sci-fi", not "this is established sci-fi", as the rules require; if I want, I can talk about Special Relativity in my stories, even though SR is real physics, right? And I think this is also real - I believe nukes have been built since the past century, and if we wanted we could blast mountains with them, or not? (sigh don't know where one complains, so nevermind me - but feel like examined by a bot XP)
The problem that PF has with 'SciFi' based discussions is that the authors tend to move the goal posts in order to fit the facts to their stories. So the threads easily depart from the Physics that PF is all about. You will get no joy from complaining because PF's purpose is not to polish up SciFi scenarios to make them slightly more technically acceptable. SciFi questions should be on the SciFi forum so that people like me don't have to deal with them. SciFi is fun but even Arthur C Clarke needed to bend the rules for the purpose of the plot. And he was a pretty well informed kind of guy.
 
itssilva said:
projectile's trajectory due to the lower pressure
An absolute lower limit of pressure on the trajectory is vacuum. Try to compare that to the pressure of the blast and give us your estimate about the percentage...

Something like 'effect of a flea to the temperature of Hell' comes to my mind...
 
'SciFi' based discussions
This discussion is not 'SciFi" based, the sci-fi aspect was only circumstantial motivation; if I ask a scientific question about the Periodic Table and mention in passing "oh, maybe I'll write a song about it", does it get bumped into the Folk Ballads subsection too?
PF's purpose is not to polish up SciFi scenarios to make them slightly more technically acceptable
I'm not asking you people to do any kind of work for me, like setting up a computer simulation yourselves - I'm ignorant about the state-of-art of fallout hydrodynamics, so I posted a question here because maybe this is common knowledge to some expert, who can answer it in two lines, simulation or not; but if you don't know, then I guess we're in the same boat.

Alas, to answer a query, no, I'm not a published writer (though I have a yen to do so sometime in the future), but I fail to see the connection of that with my want of making a few accurate drawings of an explosion; if it makes you feel better, no, I have no declaration of interests there. My biggest problem here, however, is that you're not being consistent with your own rules: https://www.physicsforums.com/threads/science-fiction-and-fantasy-reviews-forum-rules.680313/

Bottomline: I asked a question about existing, not speculative physics; whatever I will do with that knowledge, supposing it objective, is my own damn business. I don't mean to be offensive, though; I mean this as constructive criticism.
Try to compare that to the pressure of the blast and give us your estimate about the percentage...
Unfortunately, I'm too ignorant of hydrodynamics and nuclear physics to even get started :frown:; but anyway, I'm more interested in the qualitative behavior, so there's that
 
Last edited by a moderator:
itssilva said:
Unfortunately, I'm too ignorant of hydrodynamics and nuclear physics to even get started
Please give up about writing any hard sci-fi.
 
Rive said:
Please give up about writing any hard sci-fi.
Did you read my previous post? I just would like to make some drawings! But also, your comment is rather misguided: yeah, I suppose every hard sci-fi writer ever made extensive calculations regarding rocket engineering before their pens ever touched the manuscript; that certainly makes for an interesting read.
What is wrong with you people? Do you feel somehow compelled to be this unhelpful or straight-out jerks? I'm sorry I asked about something I didn't know...
 
Last edited by a moderator:
  • #10
itssilva said:
I suppose every hard sci-fi writer ever made extensive calculations regarding rocket engineering before their pens ever touched the manuscript
Yes. And later on, when they caught on some mistakes, they are expected to reflect on it. That's what the 'hard' part is about.
Way back, Larry Niven was welcomed with some chanting that "The Ringworld is unstable!" by some MIT students. So he had to write a sequel and add some steering engines to the thing which he previously designed with meticulous care.

It is not a problem that you asked about something you don't know. That's actually way better attitude than most has. The problem is, that you admittedly do not want to know your stuff, and yet, aim for 'hard' sci-fi?...
 
  • #11
I need to close this thread for Moderation...
 
Last edited:
  • #12
itssilva said:
What is wrong with you people? Do you feel somehow compelled to be this unhelpful or straight-out jerks?
Not usually. Usually we are extremely helpful, and try to help newbies learn and grow.

Thread will stay closed.
 
Last edited: