Visual effects of Nukes in Space

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Discussion Overview

The discussion centers on the visual effects produced by nuclear detonations in space, exploring the nature of light and radiation emitted during such events. Participants consider various scenarios, including the perception of these effects from a distance and the implications of camera frame rates in capturing the event.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that a nuclear explosion in space would produce a visible flash due to ionized atoms recombining and emitting photons, as well as thermal energy causing excited atoms to decay and emit light.
  • Others argue that the rapid expansion of vaporized material would occur so quickly that it might not be perceptible within the limited frame rate of a camera, suggesting that the flash could be too brief for human perception.
  • A participant questions the speed of the blast front, suggesting it could range from 1 km/s to 10 km/s, which would affect how quickly the effects reach an observer.
  • Some participants discuss the high temperatures at the hypocenter of the explosion, estimating it could exceed a million degrees Kelvin, which would influence the explosive velocity and the nature of the emitted radiation.
  • One participant notes that both the human eye and CCD cameras act as integrating detectors, implying that they would capture the total light emitted over a brief timeframe, regardless of how quickly it occurs.
  • Another participant mentions that the flash would be a bright point of light that grows quickly as the high-temperature gas expands, with most fission occurring in less than one second.
  • A participant references an external piece from NPR discussing nuclear explosions in space, suggesting that there are visual representations of such events available for further context.

Areas of Agreement / Disagreement

Participants express differing views on the visibility and perception of the flash from a nuclear explosion in space, with no consensus reached on the specifics of how the effects would be observed or captured.

Contextual Notes

The discussion involves assumptions about the behavior of light and radiation in space, the limitations of human perception and camera technology, and the physics of nuclear detonations, which remain unresolved and open to interpretation.

ph4tman
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Hello all,

I hope I'm posting in the right sub-forum here, because I'm quite new and don't really know my way around yet. Not to mention that the topic encompasses quite a few different areas.

The subject is nukes in space.

Or more specifically, the visual effects they should produce while in space. Now, on the forums I hang out, it's quite normal to assume a nuke in space will look like a single giant blinding flash. And if you see such a nuke detonation in, say, a movie, it should look exactly like that. I very intense pulse of light. But is that really so?

I mean, the EM-radiation will of course travel at the speed of light, and the bomb detonation should take a measly amount of time (wikipedia states that the Tsar Bomba expelled all it's energy in 39 nano-seconds, for instance, but it's wiki, so take it with a grain of salt). So, why should there be a visible flash? The eye shouldn't have time to even register the light before it's all been emitted. Glowing material from the bomb? I don't think so, it should've been vaporized and thrown across the four corners of space long before your eye has a chance to catch it (never mind a videocamera with a very low frame-rate).

Can anyone explain this to me?

For your convenience, I'll give you a more specific scenario, answer what you think the effects will look like.

You're in deep space, far outside our own solar system. You have a camera with you that has a frame-rate of 35 frames per second. 10km in front of you there is a nuke that's about to be detonated (fission, fission/fusion, it does not matter). You yourself and the camera will remain unharmed for some odd reason, your eyes will not be burned out by the flash and they'll not exhibit lingering effects on it due to biological/mechanical limitations. They'll see what's there, unedit and real.)

Boom.

What did the camera see? What did you, with your eyes, see?
 
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So, why should there be a visible flash?
Because the ionized atoms recombine and emit photons, and atoms excited by collisions, a consequence of the thermal energy, will also decay and emit visible light.

There will also be bursts in the gamma and X-ray range. The gammas coming from fission products, brehmssrahlung and neutron absorption reactions, and the X-rays coming from electrons dropping back into the K and L shells.

The vaporized mass will rapidly expand in space.
 
Astronuc said:
The vaporized mass will rapidly expand in space.

Indeed, and this is key, I think. Take the specific range I gave - 10km - that's not a whole lot in space. The vaporized material should have expanded so fast that it has passed you before a single frame on the camera takes a picture. So, if there's no more mass directly in front of you, how could there be radiation eminating from something there? Even at longer ranges, the density of the vaporized mass should drop so quickly that it'd look like a spread out cloud in no time flat.

Don't get me wrong, I know the EM-radiation flash will be there, the flash will just be so brief that your brain wouldn't have time to percieve it and the camera with the limited frame-rate wouldn't have time to catch it.

Or am I missing something?
 
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How fast does on think the blast front will move. 1 km/s? At that rate, the blast front would take 10 sec to reach the camera or person at 10 km. Or is the blast front velocity 10 km/s, in which case one will have only 1 sec.

Also remember that the mass toward the outer surface will move fastest, and the mass further in, more slowly since it has to push the outer mass away. Well inside the nuclear detonation, the material would expand slower because is has the inertia of the outer mass holding it back.

One would have to look at the equations of state for the various materials and geometries involved. One can approximate the velocity of the nuclear detonation by using a resonable approximation of the temperatures.
 
Astronuc said:
One would have to look at the equations of state for the various materials and geometries involved. One can approximate the velocity of the nuclear detonation by using a resonable approximation of the temperatures.

Well, the results are varied, but we seem to be talking about over a million degrees kelvin at the hypocenter, at least. http://hypertextbook.com/facts/1999/SimonFung.shtml" .

But generally, the explosive velocity of even normal explosives are quite high, TNT has an explosive velocity of 6.9 km/s, for instance.
 
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I think that what you are missing, is that the eye (and a ccd camera) is an integrating detector. So it looks at the total integrated flux during a "timeframe" that arrives. If that's spread over milliseconds, or in just one nanosecond doesn't matter: it is the integral.
 
vanesch said:
I think that what you are missing, is that the eye (and a ccd camera) is an integrating detector. So it looks at the total integrated flux during a "timeframe" that arrives. If that's spread over milliseconds, or in just one nanosecond doesn't matter: it is the integral.

Plus the fact that the photons are moving at the speed of light (obviously) so the gamma, X-ray, visible light, infrared will happen instantaneously with detonation. The flash will be a bright point of light in microseconds and grow quickly as the ball of high temperature gas expands rapidly. Most of the fissioning will be done in less than one second.
 
NPR just did a piece on Nukes In Space, July 4, 2010

http://io9.com/5578016/heres-what-it-looks-like-when-you-blow-up-nukes-in-space
 

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