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  Apollo 13: Radioisotope Thermoelectric Generator

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Author Topic:   Apollo 13: Radioisotope Thermoelectric Generator
Lunar rock nut
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From: Oklahoma city, Oklahoma U.S.A.
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posted 07-03-2007 11:05 PM     Click Here to See the Profile for Lunar rock nut   Click Here to Email Lunar rock nut     Edit/Delete Message   Reply w/Quote
While surfing aerospaceweb.org and reading about broken arrow incidents I was surprised to see this.
17 April 1970: As Apollo XIII returned to Earth following its aborted mission to the Moon, the crew jettisoned a radioisotope thermoelectric generator (RTG) that would have been left on the lunar surface had the landing been successful. The RTG, containing plutonium, survived re-entry and came to rest in the Tonga Trench at the bottom of the Pacific Ocean where it still remains.
Was the RTG part of an experiment? I personally have never heard anything about this and would like to know more.

Ben
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From: Daytona Beach, FL
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posted 07-03-2007 11:06 PM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
The RTG powered the ALSEP package. You can see it in some photos on the surface.

I think the paragraph you read refers to the jettison of the LM itself in which the RTG was contained.

Robert Pearlman
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From: Houston, TX
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posted 07-03-2007 11:33 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The SNAP-27 Apollo Radioisotope Thermoelectric Generator (RTG) that Terry's excerpt and to which Ben refers is described by the Smithsonian:
The SNAP-27 radioisotope thermoelectric generator is one of several atomic-powered electric generators developed jointly by the National Aeronautics and Space Administration and the Atomic Energy Commission. (SNAP stands for Systems Nuclear Auxiliary Power.) It is fueled by plutonium-238. The fuel capsule, containing 3.8 kilograms (8.36 pounds) of fuel, was carried to the Moon in a separate Fuel Cask attached to the side of the Lunar Module. The fuel cask provided thermal insulation and added structural support to the fuel capsule. On the Moon, the Lunar Module pilot removed the fuel capsule from the cask and inserted it in the RTG.

The SNAP-27 Radioisotope Thermoelectric Generator (RTG) converted the heat energy from radioactive decay to electrical energy. Five such RTGs provided electric power for the Apollo Lunar Surface Experiment Packages (ALSEP) left on the Moon by Apollos 12, 14, 15, 16 and 17. These stations transmitted information about moonquakes and meteor impacts, lunar magnetic and gravitational fields, the Moon's internal temperature, and the Moon's atmosphere for several years after the missions. After ten years, a SNAP-27 still produces more than 90% of its initial output of 70 Watts.

The Smithsonian also has a picture of the RTG and its fuel cask.

There is also a section of the Apollo 13 press kit dedicated to the Snap 27. And more images on Karl Dodenhoff's myspacemuseum.com.

Lunar rock nut
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From: Oklahoma city, Oklahoma U.S.A.
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posted 07-03-2007 11:41 PM     Click Here to See the Profile for Lunar rock nut   Click Here to Email Lunar rock nut     Edit/Delete Message   Reply w/Quote
After reading Ben's and Robert's replies I found a great deal of information on Wikipedia. Thank you Gentlemen!

Blackarrow
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From: Belfast, United Kingdom
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posted 07-04-2007 07:59 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
This is an important Apollo 13 problem that is rarely discussed. It was no coincidence that the plutonium package designed to power Apollo 13's ALSEP ended up in a deep ocean trench. As Lovell, Haise and Swigert headed home, the NASA controllers had two goals to accomplish: they had to make sure "Odyssey" hit the re-entry corridor at a safe angle; and they had to aim "Aquarius", containing the plutonium cask, somewhere relatively safe, i.e. deep ocean, far from people. In "Thirteen: The Flight that Failed", Henry S.F. Cooper states (p.127):
(Chuck) Deiterich had assured a representative of the Atomic Energy Commission...that the controllers would see to it that the cask landed in deep water a couple of hundred miles off the coast of New Zealand.
This is discussed at length at pages 180 - 182. For instance:
Under the best of circumstances nothing upsets a RETRO or a FIDO more than an attitude error, but this time there was the added problem of aiming the cask of radioactive fuel that Deiterich had promised the A.E.C. he would set down off New Zealand... Deiterich was still worrying about the fuel cask, possibly because he felt the gaze of the A.E.C. man on the back of his neck. He rapidly figured out where the cask would come down under the new circumstances [i.e. attitude errors] and he was able to assure the A.E.C. representative that it would still come down in deep water.
I don't want to give the impression, by selected quotes, that the mission controllers weren't focused 100% on getting the crew home safely, but it's important to be aware that they also had a duty not to land 8.36 pounds of plutonium 238 in someone's backyard.

Sy Liebergot
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From: Pearland, Texas USA
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posted 07-05-2007 01:39 PM     Click Here to See the Profile for Sy Liebergot   Click Here to Email Sy Liebergot     Edit/Delete Message   Reply w/Quote
I was unaware of this, but I'm not surprised based upon my own experience in the shuttle program office when the AEC spooks showed up asking us what our recovery plan was for Galileo in the event of a TAL abort. It had two RTG's onboard.

Here's what RETRO Chuck Deiterich told me:

Pretty much it is true. AEC actually took photos of the cask coming in. The cask originally attached to the side of the LM survived reentry. We had gotten cask aerodynamics shortly before the mission for tumbling and trimmed conditions. I have a letter of thanks from the AEC.

Blackarrow
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From: Belfast, United Kingdom
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posted 07-05-2007 05:36 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
Thanks, Sy. That's very interesting. This issue further reinforces my admiration for all of the NASA mission controllers. I can imagine what Chuck Deitrich might have wanted to say to the AEC man at such a critical time in the Apollo 13 mission. Instead, everyone involved just "worked the problems" and got the job done.

Lunar rock nut
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From: Oklahoma city, Oklahoma U.S.A.
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posted 07-05-2007 09:07 PM     Click Here to See the Profile for Lunar rock nut   Click Here to Email Lunar rock nut     Edit/Delete Message   Reply w/Quote
Special thanks to all that responded here. Easily understood why this was such a breath holder. Eight pounds of plutonium with a half life of eighty seven years. At least the casing performed as expected through reentering the atmosphere. I hope the casing lasts the eight hundred and seventy years as predicted.

While reading the associated material,I now wonder about the two RTGs the Russians lost in Chile. There must be some glow in the dark llamas running around down there.

Sy Liebergot
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From: Pearland, Texas USA
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posted 07-06-2007 08:43 AM     Click Here to See the Profile for Sy Liebergot   Click Here to Email Sy Liebergot     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Blackarrow:
I can imagine what Chuck Deitrich might have wanted to say to the AEC man at such a critical time in the Apollo 13 mission.
By the way, Chuck added later: "Each mission we were able to get more contingencies covered. The cask procedure was worked out a few weeks before A13."

Blackarrow
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From: Belfast, United Kingdom
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posted 08-26-2013 08:18 AM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
I wanted to revive this old thread because I have just caught the end of "Apollo 13" on TV and it reminded me of the discussion about the fate of the plutonium RTG power-pack.

I'm wondering what improvements to the contingency plans for disposal of Apollo RTGs were made after Apollo 13. Worst case scenario was the explosive destruction of a Saturn V and loss of the RTG in the ocean (or possibly Africa?) but the RTG was supposed to be able to survive this.

If the Saturn V made it into orbit, but the SIV B could not relight, the CSM would perform an Earth orbit mission and according to the Apollo 14 and Apollo 17 Final Flight Plans, the LM would be de-orbited into the ocean. I assume great care would have been taken to select an ocean trench.

But what if a significant SPS engine failure had occurred in lunar orbit (a situation similar to Apollo 16, but let's assume the SPS back-up was found to be unusable). Am I right in assuming the SPS primary system would have been used to perform the TEI burn with the LM still attached to the CSM, so that the LM descent engine would be available as back-up if the SPS failed? Assuming that to be correct, the crew would have two options for disposal of the LM with its RTG: aim for Earth and put the LM into an ocean trench (as with Apollo 13) or aim for deep space, jettison the LM into solar orbit, then correct the trajectory to allow a safe return to Earth. Each option has its drawbacks. My question is: did anyone ever prepare a plan to cover this scenario and these options? Even the Apollo 17 Final Flight Plan (which has a detailed list of "alternate mission" plans) doesn't cover this.

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