Sciencemadness Discussion Board

Nuclear blast

Levi - 27-1-2007 at 03:31

Can anyone name a good reason why the nuclear blasts in the past have not detonated the Nitrogen / Oxygen mix we call our atmosphere? It seems like a perfectly reasonable thing to expect as this is essentially a FAE although I think we can all agree this hasn't happened yet :D

quicksilver - 27-1-2007 at 06:39

The first thing that pops into my little mind is that the ratio is not optimized for that sort of thing (FAE).

garage chemist - 27-1-2007 at 06:44

Reaction of N2 and O2 is very endothermic.
The reaction occurs even in car engines, which is one of the reasons exhaust catalysts have to be used.

Levi - 27-1-2007 at 07:11

Wikipedia had this to say:

"In 1945 there was some initial speculation among the scientists developing the first nuclear weapons that there might be a possibility of igniting the Earth's atmosphere with a large enough nuclear explosion. This would concern a nuclear reaction of two nitrogen atoms forming a carbon and an oxygen atom, with release of energy. This energy would heat up the remaining nitrogen enough to keep the reaction going until all nitrogen atoms were consumed. This was, however, quickly shown to be unlikely enough to be considered impossible [1]. Nevertheless, the notion has persisted as a rumour for many years."

I guess it isn't really the same principle though since it involves transmuting nitrogen to carbon which doesn't happen with FAE.

Btw, that bit about it being "unlikely enough" doesn't exactly make me feel comfortable lol.

quicksilver - 27-1-2007 at 07:25

To the best of my understanding an FAE has to have some care in it's construction in that the proportions of ignitable materials need to maintain consistency when exposed to the source of ignition. Thus the varience of our atmosphere may play a role in "keeping the lid on" a catostophic event like the one described. I could only imagine those early experimentors concerns for their creation. If it works at all...if it works "too well"...:o

12AX7 - 27-1-2007 at 08:50

Density is too low.

YT2095 - 27-1-2007 at 10:30

Quote:
Originally posted by 12AX7
Density is too low.


exactly! :)

Waffles - 27-1-2007 at 10:51

The the idea of a self-sustaining nuclear reaction in the atmosphere is just silly, and the reason NO is used in combustion engines is not because it burns or combusts well, but because the reaction of NO with intake O2 is VERY endothermic, which increases the density of the fuel/air mixture inside the combustion chamber and hence the horsepower produced.

nitro-genes - 27-1-2007 at 12:27

N20 is used for car engines, never seen NO used...:)

The only reason why NO is produced by cars is that the exaust pipe cools down the exhaust fumes so fast that the equilibrium that formed NO inside the combustion chamber (high temp and pressure) isn't able to shift back completely to oxygen and nitrogen...

The nuclear reaction won't happen, as said, the density is too low. Nuclear power plants use the density (distance between enriched uranium cores) to control the reaction rate...

Waffles - 27-1-2007 at 13:05

Quote:
Originally posted by nitro-genes
N20 is used for car engines, never seen NO used...:)

The only reason why NO is produced by cars is that the exaust pipe cools down the exhaust fumes so fast that the equilibrium that formed NO inside the combustion chamber (high temp and pressure) isn't able to shift back completely to oxygen and nitrogen...


I spilled grapefruit juice on my keyboard, and now some keys like '2' (upper left keyboard ;)) don't actually PRESS when i press them...

Levi - 27-1-2007 at 13:10

Quote:
Originally posted by nitro-genes
The nuclear reaction won't happen, as said, the density is too low. Nuclear power plants use the density (distance between enriched uranium cores) to control the reaction rate...


Nuclear reactors never (hopefully) go supercritical, though. Since a nuclear blast is certainly expanding faster than the speed of sound in the atmosphere, the gas in front of the blast is sure to be compressed considerably... right?

a_bab - 27-1-2007 at 13:36

The reaction happens though, due to the very high temperatures/pressures. In order to "ignite" the atmosfere one has to detonate a bomb that would compress all the atmosfere to a critical point. Such a bomb would probably blow the planet apart anyway.

The red mushroom cloud left after a nuclear detonation has tons and tons of NO2, and that was seen as a problem for the enviroment. In a thermonuclear war with thousands of blasts, that would fuck up the atmosfere to a point where the radiation would be a lesser concern.

[Edited on 27-1-2007 by a_bab]

12AX7 - 27-1-2007 at 15:25

Hmm, all the x-ray and hard UV would definetly split a lot of nitrogen radicals (N with three dots?) in the vicinity of le bombe.

Tim

nitro-genes - 27-1-2007 at 17:14

Quote:
Originally posted by iamthewaffler
I spilled grapefruit juice on my keyboard, and now some keys like '2' (upper left keyboard ;)) don't actually PRESS when i press them...


Hehe, your post wasn't exactly to the point as well my friend, and only laughing at someone is about as friendly as saying that someone messing around with steel pipebombs filled with large amounts of MEKP should be considered to get the darwin award...;)

I am become death , the destroyer of worlds

franklyn - 30-1-2007 at 05:31

Quote:
Originally posted by Levi
Can anyone name a good reason why the nuclear blasts in the past have not detonated the Nitrogen / Oxygen mix we call our atmosphere?

That's a very complicated question to answer, a bit like taking one frame of a
motion picture and from that determining the plot and story line of the rest.
Without invoking exotic particles such as muons which can catalyse nuclear
fusion at room temperature , the Lawson criterion assesses the requirements
for the triple product, density, confinement time, and plasma temperature of
the given reactants. A further practical consideration is the Albedo which is the
ratio of energy which is lost by radiating away , to the amount which can be
retained to propagate and continue the reaction in a given physical circumstance.
The consequences of these considerations is that conditions of the ambient
atmosphere will not support and sustain any conceivable fusion. The principle
reason fusion does not occur as a shockwave , is that most of the emitted
energy radiates away perpendicular to the plane area of the wave comprising
the reaction zone , where it is needed to continue and sustain further fusion.
Confinement would need to occur with compression occuring in two dimensions
moving as a radial contraction in the direction of travel. Theses conditions are
engineered to occur within a hydrogen bomb in which the casing additionally
provides the needed containment of emitted radiant energy to progressively
sustain fusion along its cylindrical length.
The more practical reason is that the peak energy intensity available at the
surface of a weapon , something on the order perhaps of 10 to the power of 20
watts per square centimeter is insufficient to satisfy the Lawson criterion.
So this is a non-start.
.

[Edited on 30-1-2007 by franklyn]

White Yeti - 21-10-2011 at 17:06

Setting aside the low density of air and the endothermic nature of the formation of nitrogen oxides, the high temperatures present exactly at the time of a nuclear blast would destroy any nitrogen oxides that might form as a result. It's simply too hot for anything to form because it would get destroyed shortly afterwards. What you get during a blast is a soup of plasma, free radicals, nuclei and all sorts of unhealthy things.

Once the nuke cools down, then you can get nitrogen oxide formation, and you oftentimes do. I can't find the link to a video I watched a long time ago. It was a video of the detonation of a small nuke. The fireball was tiny, but you could clearly see a cloud of nitrogen oxides after the blast.

A nuclear blast is simply too localised for the "combustion of the atmosphere". I hate to say it, but the energy contained in a nuke is simply not enough, and not optimally distributed for something like this to happen.

AndersHoveland - 22-10-2011 at 01:00

The report is actually in the ScienceMadness library:
http://library.sciencemadness.org/lanl1_a/lib-www/la-pubs/00...

In some ways the report is worrying. A thermonuclear bomb with a radius of only 6.2 meters would generate a temperature of 1.6 MeV (measured in electron volts). At this temperature, the loss to radiation would be a factor of only 1.6 times the sustaining rate of energy production from the nuclear reaction of nitrogen atoms. Consider that, 1.6 !

The main factor to be considered for the radiation losses of this type of large explosion is infrared and vissible, since the atomsphere is so transparent. One would wonder how much the calculation would change if the surrounding atmosphere was "seeded", for example with smoke, which would significantly change the factor for radiative losses. Could it be possible in a large scale nuclear war, that the entire atmosphere would be filled with smoke, dust, and nitrogen dioxide, and that this might enable a self sustaining atmospheric reaction initiated from an additional particularly powerful bomb?

Another main factor was the low density of the air. Since the empty space has a high heat capacity. Would a self sustaining nuclear reaction be more likely on another planet with a significantly higher atomspheric pressure containing a high proportion of nitrogen? Especially if the atomsphere was ammonia, which also contains proton nuclei.

Other planets are known to contain seas of liquid ammonia (pressurised NH3). Because of the high density and ideal nuclear composition, this is leaves important questions.

[Edited on 22-10-2011 by AndersHoveland]

quicksilver - 22-10-2011 at 08:20

Several historical books about the Manhattan Project mentioned that some of the scientists debated the possibility of a catastrophic chain event (Oppenhiemer?). One of the issues was that the group could neither "down size" nor depend on a collective "notebook experiment"; they either had to take the chance or call it off. Which leads thoughts about today's software predictions of an experiment's conclusions. Several years back (I think in General Chemistry) there may have been a debate about the use of software in the determination of whether certain experiments would yield a consistently predicable synthesis. Just opinion - but with both radiological and energetic chemistry there may be too many variables for even modern software to account for.

Ozone - 22-10-2011 at 08:54

IIRC, Teller mentioned atmospheric "ignition" (e.g fusion) might happen, Oppenheimer and Bethe ruled it out and Fermi (whilst in the bunker just before Trinity) suggested a bet as to whether or not the atmosphere would ignite.

Yep: http://www.sciencemusings.com/2005/10/what-didnt-happen.html

Imagine if scientists of this caliber had computers (considering what was done with the slide-rule)!

quicksilver - 22-10-2011 at 09:03

Ahh, I stand corrected.