
Plutonium: The element that saved the crew of Apollo 13 - roc123
http://www.bbc.com/news/magazine-29274491
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Wingman4l7
Not only is the article title misleading linkbait -- it's mostly about the
discovery of the actinide elements -- it doesn't make any sense.

The LEM _(Lunar Excursion Module)_ did carry an RTG _(Radioisotope
Thermoelectric Generator)_ \-- but this was for the ALSEP _(Apollo Lunar
Surface Experiment Package)_ , which is what the training photograph shows
Lovell carrying. The instruments were stored in an equipment bay and weren't
even accessible from inside the LEM, and weren't relevant to navigation or
communications anyway. The heat output of the RTG was not intended for life
support, nor for keeping any LEM systems within safe operating temperatures. I
am at a loss as to how plutonium was relevant to the astronaut's survival.

What _is_ an interesting story is the fact that the Apollo 13 RTG is now
resting at the bottom of the Tonga Trench in the Pacific Ocean, since the LEM
re-entered the Earth's atmosphere after it was jettisoned prior to reentry:
[http://www.spacesafetymagazine.com/aerospace-
engineering/nuc...](http://www.spacesafetymagazine.com/aerospace-
engineering/nuclear-propulsion/will-anyone-recover-apollo-13s-plutonium/)

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pja
I _think_ the idea is that the heat output of the battery (about 1.5kW) may
have made the difference between the astronauts surviving and not since they
had no other heat source available - the LEM heaters were all shut down to
conserve power after the explosion.

Clearly the plutonium heat output was never intended to heat the LEM during
ordinary operation, since not all missions carried such experimental apparatus
- presumably had the mission gone to plan the normal LEM heaters would have
run on a lower duty cycle to compensate for the extra heat input from the
plutonium cargo.

I agree that it's a badly written article that doesn't actually follow through
on the title, so the above is purely guesswork.

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Richardc10
The fuel core for the SNAP-27 generator was stored on the _outside_ of the LM
descent stage. It was installed into the generator by the astronauts on the
lunar surface. I have chopped an image and some text from the Apollo 13 press
kit.

[https://www.dropbox.com/s/02px58fhbz0gigt/apollo13.pdf?dl=0](https://www.dropbox.com/s/02px58fhbz0gigt/apollo13.pdf?dl=0)

I doubt there would have been much thermal path from the fuel element back
into the LM itself - indeed the mount would probably have been designed to
minimise that flow since the problem is normally how to reject heat from a
spacecraft, rather than absorb it. The story just seems a tag to discuss
plutonium.

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tunnuz
Thanks for the insight.

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tdicola
One bad thing is that the LEM was never designed to return to earth, so when
Apollo 13 came back with the LEM it also brought the RTG back and could have
dispersed the 8.5 lbs of plutonium in the atmosphere. In the grand scheme of
things this was probably nothing compared to all the atmospheric nuclear
weapon tests that were done in the preceeding years (like the 50 megaton Tsar
Bomba blast).

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AnonymousJohn
Now corrected to "Plutonium: The scary element that helps probe space's
secrets". Apollo 13 still mentioned, but with no mention of the fact that the
only thing that distinguishes its RTG is that it's at the bottom of the
Pacific. Neither does it mention that only the less dangerous isotope is used
in space.

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someperson
Great article on the history and discovery of the actinide elements.

The astronauts lives were apparently saved by the warm Plutonium battery
powering the Lunar Module's scientific equipment (not exactly sure how
though).

EDIT: I know what Radioisotope Thermoelectric Generators are, but not why the
warm battery saved Apollo 13.

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gh02t
Not sure how it generates power? Pu238 is a very strong alpha emitter. Alpha
particles (helium nuclei) are really big and charged, so they don't travel
very far and deposit all their energy near where the decay occurs (as opposed
to decay with e.g. neutrinos that essentially never interact and thus deposit
no energy). The alpha decay carries a lot of energy so a chunk of Pu238 gets
pretty hot. Couple it with a thermoelectric generator and you have an ideal
power source for space applications.

Also, alpha particles have almost no penetrative power in human tissue so
they're harmless as long as the source isn't inside of you. Pu238 is almost
exclusively an alpha emitter, so it's completely safe to handle for extended
periods, at least radiologically. It puts off a ton of heat and is chemically
really toxic though. I've dealt with it in the lab before, it's relatively
harmless as far as nuclear sources go. It's not suited for weapons either, so
it isn't directly a proliferation concern, though producing it is because it
is related to weapons grade production. You don't see it used very often
mostly because it can only be made in a specially configured reactor, so it's
not exactly common.

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tunnuz
Thanks for the power generation explanation.

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gourneau
Pu238 is also in very short supply these days
[http://www.wired.com/2013/09/plutonium-238-problem/all/](http://www.wired.com/2013/09/plutonium-238-problem/all/)

