Apollo 13

[bernse]

I was just watching a show about Apollo 13. One of the concerns at the time was that the LEM was going to burn up in the Earths atmosphere. It had some plutonium decay power source and there was a concern about it "leaking." The plan was to try to dump the LEM into some deep part of the pacific and hope for the best.

Did the LEM hit its "target" - a deep trench in the Pacific? Has there ever been a check for excess radioactivity in the area? I've never heard either way but curious to know.

[Genseric]

The drama surrounding the ill fated Apollo 13 mission was an ideal subject for a series of books and movies. But the most disturbing aspect of the near disaster has mostly been neglected. Apollo 13 was a nuclear catastrophe waiting to happen, as aboard the Lunar Excursion Module (LEM) was a plutonium power cell.

Called 'Systems for Nuclear Auxiliary Power' (SNAP-27) it contained 3.8 kilograms of plutonium, which is so toxic that less than a millionth of a gram can cause cancer. Designed to be left behind on the moon, the crippled Apollo 13 was forced to carry it back to Earth. Not only were the three astronauts in danger but millions on the ground unwittingly lived under threat from the toxic space junk.

When the paralyzed Apollo 13 re-entered Earth's orbit, the astronauts transferred back to the command module, and the LEM with its nuclear payload was jettisoned. It re-entered the atmosphere somewhere over New Zealand and although the LEM burned up, SNAP-27 survived re-entry and plunged intact into the Pacific Ocean off Tonga, where according to NASA it is "isolated from man's environment." SNAP-27's radioactivity will last 2000+ years and its watery grave comprises some of the world's prime fishing grounds.

NASA successfully concealed the crisis from the world at the time, and continues to power some spacecraft with plutonium, recently launching the Cassini probe with a 33 kilo plutonium cell.

http://www.historyplace.com/specials...nt/strange.htm

[Genseric]

D'oh! Put a big QUOTE tag all the way around that sucker.

[Genseric]

Upon rereading that bilp I posted, I feel I have to point out that there is something of a slant to it, that I don't necessarily support. I feel that the scientific benefits of using RTGs in deep space probes, far outweighs the slight risk of plutonium dispersal during launch or gravity assist in near earth space. Viva Cassini!

[friedo]

Pu-238 has a half-life of about 90 years, IIRC, so the radiation threat from the Apollo 13 LEM shouldn't last more than a few hundred years.

Also, the main danger from Plutonium isn't the radiation, but inhalation of Plutonium dust, which is extremely toxic.

[douglips]

Originally posted by friedo
Pu-238 has a half-life of about 90 years, IIRC, so the radiation threat from the Apollo 13 LEM shouldn't last more than a few hundred years.

I'm not averse to radiation, but I must correct this.

The half life of ²³⁸Pu is indeed about 90 years. However, it decays by [sym]a[/sym] into ²³⁴U, or else it likely undergoes fission.

²³⁴U itself decays by [sym]a[/sym] to ²³⁰Th, or it also may fission. But, the half life here is about 25000 years. ²³⁰Th decays to Radon, etc. etc.

So, the radioactive products of this power pack will last a very long time. Now, as to whether there is any danger, that's a different issue.

[friedo]

Good point, Mr. Lips, thanks for the correction.

[Chronos]

Three things: First of all, bomb-grade plutonium has approximately the same LD-50 as caffeine (LD-50 is the dosage of a poison you'd need to have a 50% chance of dying from it). It's nasty stuff, to be sure, but not as nasty as most folks think. Second of all, the plutonium used in a radiothermal generator is not the same isotope used in bombs, and is even less deadly. Thirdly, plutonium is primarily an alpha emitter, which means that it's deadly if it gets inside of you, but you could carry it around in a paper bag and not get any dosage from it.