The threats involved in re-entering the atmosphere

[Edyoungscience]

Sorry if I seem naïve but what sort of threat does a piece of technology carrying radioactive/nuclear substances cause on its re-entry into the earths atmosphere if there is any? (Explosions or malfunctions for example)

If there are any severe threats, what are the implications of them?

Thank you, Edward Eyre

(This is my first thread, if I have done this in the wrong place or this is a re-post of another topic please direct me to the appropriate place)

[yevaud]

Thank you for asking. I will move this to our forum "Ask the Astronomer," which is more suited for questions and answers.

Welcome to SDC.

[doc_bugsy]

Sorry if I seem naïve but what sort of threat does a piece of technology carrying radioactive/nuclear substances cause on its re-entry into the earths atmosphere if there is any? (Explosions or malfunctions for example)

If there are any severe threats, what are the implications of them?

Any threat might be based on mass, location, materials and manufacturing.

1. Is the mass of the object great enough to pose a physical hazard if it survives re-entry.
2. Is anyone or anything located at the point of impact, or will investigate the impact.
3. Does any hazardous material remain in large enough quantities in an exposed state that could be dangerous.
4. How is the object shielded/protected/manufactured? Can it survived re-entry without releasing any material?

Also, considering that the surface of the Earth is so vast compared to the size of any object that would re-enter the atmosphere, the odds of a particular person being affected are extremely low even in the worse case scenario.

[Shpaget]

Are you referring to nuclear weapons, nuclear reactors or just nuclear fuel?
The risk of it going critical is insignificant. For a nuclear weapon to go kabloei, you need very complicated series of events and the complex architecture of the bomb.
Just heating it up will not cause it to go nuclear.

However, there is significant danger if it is just thrown uncontrolled. Even though it will not cause the nuclear blast, some other components (leftover fuel from thrusters of primary charges for the nuclear bomb) might explode and cause dispersal of radioactive dust over large area.

If nothing explodes, and the container hit the surface, it could cause serious, but localized damage. For example, if a house or even a small building was struck by something like that, it could certainly be destroyed beyond repair, killing anybody inside.
However urban area covers just a tiny fraction of the Earth's surface so the debris, if it reaches surface, would probably hit the ocean or empty land (forests), where it could start a fire.

All of this applies only to uncontrolled reentry, which is foolish if something highly radioactive is being reentered. Controlled reentries are much safer.

[bdewoody]

I think maybe he is referring to the nuclear power supplies on many of our spy satellites and a few research satellites. From what I have read those packages are about as bullet proof as anything man made can get. About the only danger they would pose during an uncontrolled re-entry would the impact of crashing into something on the ground. Even then the device would not start a nuclear explosion. There's a lot of other stuff higher on the list of things to worry about.

[matthewota]

On January 24, 1978 a portion of the Soviet Cosmos 954 spacecraft reentered the Earth's atmosphere over Canada and scattered radioactive debris over a wide area. Canadian and American military forces were involved in a massive recovery effort as the radioactive material had high radiation levels.

http://en.wikipedia.org/wiki/Cosmos_954
http://www.hackcanada.com/canadian/other/cosmos954.html
http://www.pwnhc.ca/timeline/index_winIFix.asp?forward=http%3A//www.pwnhc.ca/timeline/1975/1978_Cosmos.htm#Scene_1