Galileio Burnup on Jupiter

[JebKeb]

I found a rather interesting page that said something along the lines of the plutonium pellets fell through jupiter, reached crush depth and ignited, causing the splotch that appeared 1 month after the burnup of Galileio. 

Now this guy seems a bit conspiracy-theorist in other articles on his website, but this page, apart from the end, seems balanced and mostly true.

Anyone got an opinion on this?

[_Augustus_]

https://space.stackexchange.com/questions/868/did-the-galileo-spacecraft-cause-a-blotch-on-jupiter-after-it-crashed

[Exploro]

Furthermore the blotch in question formed in the wrong hemisphere where Galileo ultimately went down.

According to the wiki article on Galileo, the craft entered the Jovian atmopshere just south of planet's equator.

This is a photo of the blotch on a page by Robert R. Britt. The image is inverted but we can see the GRS in the upper hemisphere of the image. This corresponds to the Jovian Southern Hemisphere. The blotch in question appears in the lower hemisphere (withing the dark and thin color band); which corresponds to Jupiter's Northern Hemisphere.

[kerbiloid]

Quote

so much the plutonium went supercritical

²³⁸Pu went supercritical?

[magnemoe]

2 hours ago, kerbiloid said:

²³⁸Pu went supercritical?

No, the idea is wrong in so many ways. 
Yes you could theoretical get an plutonium mass to go critical then it becomes degenerated matter deep inside an gas giant. This would result in lots of radiation who would heat the mass so it boiled away until it was below critical, guess it would look a bit like then it burned up in the atmosphere. Think that the RTG would rater break up on reentry in the first place, entering Jupiter would be far more stressful than on Earth.
RTG also uses plutonium oxide who is safer to handle but the added oxygen would increase the size / density to go critical a lot. 

To get an actual nuclear bomb you need to compress the plutonium fast and have the compression continue for some time after you go critical so its time for many reactions. This is hard, fizzles or defect nuclear bombs was common then they learned how it worked. Not something who can happen by accident. 
Even if you set of an nuclear bomb very deep down inside Jupiter it would be impossible to see on Earth, we can detect atmospheric nuclear blasts from the blast itself if you miss the bast by an minute you would not spot it. from orbit. 

[Human Person]

3 hours ago, kerbiloid said:

²³⁸Pu went supercritical?

Funny. Supercritical is just a gas-state, it has nothing to do with The Critical Mass. 

It's the point where the gas phase reaches the same density as the liquid phase and they become indistinguishable.

Eg. CO2 goes supercritical at 31 degrees Celsius and 74 bars of pressure.

Edited September 18, 2017 by Physics Student

[kerbiloid]

11 minutes ago, Physics Student said:

Supercritical is just a gas-state, it has nothing to do with The Critical Mass. 

That's from the article.

23 minutes ago, magnemoe said:

To get an actual nuclear bomb you need to compress the plutonium

Usually ²³⁹Pu.
I mean could ²³⁸Pu  ever achieve enough great (neutron cross section * density) to support a chain fission? At any density.
Afaik, critical mass is ~sqrt(density). So, wouldn't be so, that to run fission its cores have to get enough close to make fusion. Or just to eat neutrons withouit multiple output.
238 has even number of nucleons. Such isotopes usually dislike chain fission.

Edited September 18, 2017 by kerbiloid

[tomf]

Supercritical can also be used to describe a mass of fissile material that has significantly above the mass/density required in order for it to be a critical mass. In a supercritical state it is able to sustain a number of generations of fission before the heating from the reaction expands it to below criticality.

[p1t1o]

Funnily enough, atomic bombs are a bit more complex than simply putting fissiles under pressure.

If the Pu did go supercritical for some miraculous reason, it would fizzle - just get very hot and disperse itself.

So yeah, it is entirely BS.

 

[danielboro]

and(im gussing) the somaker-levi comet had more energy in it wen it collided whit Jupiter then the Pu pellet has
the pellets dont have inaf energy to make a splotch even if it went kaboom

[Bill Phil]

3 hours ago, Physics Student said:

Funny. Supercritical is just a gas-state, it has nothing to do with The Critical Mass. 

It's the point where the gas phase reaches the same density as the liquid phase and they become indistinguishable.

Eg. CO2 goes supercritical at 31 degrees Celsius and 74 bars of pressure.

Supercritical is a description of nuclear chain reactions, along with "critical" and "sub-critical," essentially describing how the reaction sustains itself. It either doesn't, it barely does, or it increases its energy output massively in a short amount of time.

[sevenperforce]

So you can get your terms right (which, let's face it, pop media is NEVER going to manage):

• Radioactivity. The process by which certain atomic isotopes eject particles to stabilize an unstable nucleus.
• Radionuclide. An atomic isotope with an unstable nucleus that has a nonzero probability of exhibiting radioactivity.
• Alpha/nucleon/cluster decay. The case of radioactivity in which certain radionuclides eject neutrons, protons, or clusters of nucleons from their nucleus.
• Fission. The breakup of an atomic nucleus.
• Fissionable radionuclide. A radionuclide which can be induced to immediately undergo fission by bombardment with the products of radioactive decay or of other fissions.
• Prompt neutron. Fission products released immediately, rather than being released with a delay due to decay of other fission products.
• Fissile radionuclide. A fissionable radionuclide in which any fission event produces an excess of prompt neutrons immediately capable of inducing subsequent fission.
• Criticality. The state at which the products of each fission event induce exactly one subsequent fission.
• Subcriticality. The state at which too many of the products of each fission event escape before they can induce at least one subsequent fission.
• Supercriticality. The state at which the products of each fission event induce more than one subsequent fission, causing a chain reaction.
• Prompt critical. The point at which a fissile radionuclide reaches criticality or supercriticality with prompt neutrons alone (e.g., a runaway chain reaction has started and there is no way of delaying it, poisoning it, or moderating it).

A fissionable radionuclide can undergo criticality, but it cannot undergo prompt criticality. Nuclear reactors can run on fissile radionuclides, fissionable radionuclides, or both. Nuclear fission weapons require fissile radionuclides. Nuclear reactors want controlled supercriticality; they do not want prompt criticality. Nuclear weapons need the fissile material to be prompt-critical. A meltdown happens when supercriticality in a nuclear reactor runs out of control, causing the structural integrity of the fissile mass or its containment to fail. A fizzle happens when prompt-criticality in a nuclear weapon happens too early, blowing the fissile mass apart before any significant portion of it can undergo fission. 

Edited September 18, 2017 by sevenperforce

[kerbiloid]

So, ²³⁸Pu was always considered as a fissionable radionuclide, not a fissile one, rather than ²³⁹Pu.

Edited September 18, 2017 by kerbiloid

[peadar1987]

One major pet peeve is when supposedly smart/qualified people in fiction say a nuclear reactor "went critical", meaning it exploded or melted down. "Going critical" means withdrawing the control rods enough for the reactor to actually work.

[sevenperforce]

It's important to distinguish between radioactive decay and fission (something I just clarified in my post above). Decay is when a tiny piece of a nucleus is ejected via quantum tunneling. Fission is when the nucleus splits apart. Decay particles can induce fission.

²³⁹Pu does not decay as rapidly as ²³⁸Pu, but ²³⁹Pu fission produces an average of 2.9 prompt neutrons per event, whereas ²³⁸Pu fission produces less than 1 prompt neutron per event.

[DerekL1963]

7 hours ago, sevenperforce said:

A fizzle happens when prompt-criticality in a nuclear weapon happens too early, blowing the fissile mass apart before any significant portion of it can undergo fission. 

In terms of nuclear weapons fizzle means nothing more than failing to reach the designed yield, regardless of the cause (and there are numerous possible causes).  With a yield of 110kt, Castle Koon is still considered a fizzle because it was expected to have a 1 megaton yield.  (The primary fired at full strength, but due to a design flaw the secondary failed to properly ignite.)  

The Castle test series was something of a mess, with not only the largest fizzle ever - but multiple devices that exceeded their planned yields (including the infamous Castle Bravo).

Edited September 18, 2017 by DerekL1963