Author Topic: Wired article on Pu-238 production for space missions  (Read 29278 times)

Online Blackstar

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This article just appeared yesterday. It is a bit problematic. I sent an email to the reporter, which I'll post as well.

http://www.wired.com/wiredscience/2013/09/plutonium-238-problem/all/

NASA’s Plutonium Problem Could End Deep-Space Exploration

By Dave Mosher
    09.19.13
   
In 1977, the Voyager 1 spacecraft left Earth on a five-year mission to explore Jupiter and Saturn. Thirty-six years later, the car-size probe is still exploring, still sending its findings home. It has now put more than 19 billion kilometers between itself and the sun. Last week NASA announced that Voyager 1 had become the first man-made object to reach interstellar space.

[SNIP]
« Last Edit: 09/21/2013 02:14 AM by Chris Bergin »

Online Blackstar

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Re: Wired article on Pu-238 production for space missions
« Reply #1 on: 09/20/2013 03:47 PM »
Here is a slightly condensed version of the message I wrote to the reporter:

Sir, I just read your Wired article on the Pu-238 situation. I think it presents some misconceptions about the current situation. As background, I was one of the study directors on the 2009 National Research Council report that you linked to in your article. Although I'm not part of the program, I am still very aware of NASA's planetary program.

Part of my complaint with the article is the tone. I think it is more dire than it should be. The head of NASA's planetary program has described the Pu-238 situation as one of the few "bright spots" in the overall planetary program. After years of trying, they are now gearing up for production. My understanding is that the equipment (the targets for the reactor and other laboratory equipment necessary for producing and testing the materials that get irradiated in the reactor) is essentially built and there is now agreement to fund production, ramping-up to producing about 1.5 kg per year. So now they really only have to worry about sustainment funding, not initial approval. It is the overall budget situation that constrains what NASA can do with planetary science, a fact that dwarfs the issue of availability of Pu-238.

You correctly note that some missions have essentially been deferred or put off the table due to a lack of Pu-238, but I don't know what you mean when you cite eight missions "delayed or canceled." There certainly were not that many missions requiring Pu-238. Most missions that NASA has delayed or canceled are due to budget cuts, not lack of Pu-238. The article is therefore misleading on this count. In addition, I would note that the Jupiter Europa Orbiter is no longer the baseline Europa mission. That is now the Europa Clipper (which would not orbit Europa), which JPL currently has under study and includes a solar power option. Also, the article should mention that NASA considered two ASRG-powered missions (Titan Mare Explorer and Comet Hopper) in its recent Discovery competition. They were not selected, but the fact that they were finalists was testament to NASA's interest in flight testing the ASRG on an operational mission and continuing Pu-238 missions.

Finally, I suspect that your statement that "two-thirds" of the Pu-238 identified in the 2005 DoE report was designated for "national security missions" is incorrect. As I read that table, it indicates that less than 25 kg was designated for that purpose, without explicitly stating what that amount was. Therefore the amount could be one kilo or 24.9 kilos. It states that in 2005 the minimum NASA requirement did NOT include the MSL/Curiosity rover. Of course, Curiosity was built and used 11 kg (some of which came from the 16.5 kg acquired from Russia), and there is also enough to power the Mars 2020 rover, meaning an additional 11 kg, plus enough to power two ASRGs.

Put another way, in 2005 the total available Pu-238 was: 39.51 kg PLUS 16.5 kg for a total of 56.01 kg.

NASA used 8 kg (New Horizons), 11 kg (MSL/Curiosity) and has 11 kg for the Mars 2020 rover, for a total of 30 kg. (Add in--I think--another 5 kg for the two ASRG-powered missions.) That implies that national security requirements were probably substantially less than the maximum 25 kg in the chart. (Put another way: NASA uses up all the Russian Pu-238 simply with MSL/Curiosity and the two ASRG mission reserves, so the 8 kg for NH and 11 kg for Mars 2020 have to be subtracted from the 39.51 kg that was available--approximately half.)


Offline vulture4

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Re: Wired article on Pu-238 production for space missions
« Reply #2 on: 09/20/2013 04:05 PM »
Good information. Nevertheless, in the long run wouldn't there be advantages to using a small reactor instead? Launch hazards are greatly reduced since uranium is virtually nontoxic compared to plutonium, power capabilities tend to be higher and fuel consumption rate can be varied to meet mission requirements.
« Last Edit: 09/20/2013 04:06 PM by vulture4 »

Online Blackstar

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Re: Wired article on Pu-238 production for space missions
« Reply #3 on: 09/20/2013 05:01 PM »
Good information. Nevertheless, in the long run wouldn't there be advantages to using a small reactor instead? Launch hazards are greatly reduced since uranium is virtually nontoxic compared to plutonium, power capabilities tend to be higher and fuel consumption rate can be varied to meet mission requirements.

For these missions they don't need the power of a reactor. And it would be expensive to develop it.

And it's hard to emphasize this enough, but one of the primary reasons for sticking with this technology for these kinds of missions is that we know so much about it. There is a tremendous amount of analysis and engineering history behind this work.

Offline Robotbeat

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Re: Wired article on Pu-238 production for space missions
« Reply #4 on: 09/20/2013 05:09 PM »
And it works really well. For a long time. With low complexity (at least for RTG... ASRG is more complicated, but the heat source itself is simple as dirt, compared to a reactor). With very, very low radiation when operating. And feasible to make small devices with it. Nothing else really comes close to these things once you're out past the asteroid belt and/or Jupiter.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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Re: Wired article on Pu-238 production for space missions
« Reply #5 on: 09/20/2013 05:18 PM »
During the decadal survey we commissioned a study on small fission power reactors. I'm attaching it here.

In all honesty, we did this because John Casani requested it and Casani is a legend (and nice guy). But I think there was little support for it among the planetary science community. At the very least they wanted the Pu-238 production line restarted so that they could consider missions that had been proposed in the recent past. Small fission reactors would be nice to have for more ambitious planetary missions, but there are no realistic missions that could use them that anybody could foresee in the next several decades.

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Re: Wired article on Pu-238 production for space missions
« Reply #6 on: 09/20/2013 07:56 PM »
Just received an interesting reply from the reporter. He disagreed with my statement that the tone of the article was too negative and provided some information indicating that the tone was in fact accurate. Don't think I can share all that here. We'll see what happens over the next few months with the budget battles.

Offline Robotbeat

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Re: Wired article on Pu-238 production for space missions
« Reply #7 on: 09/20/2013 08:17 PM »
Just received an interesting reply from the reporter. He disagreed with my statement that the tone of the article was too negative and provided some information indicating that the tone was in fact accurate. Don't think I can share all that here. We'll see what happens over the next few months with the budget battles.
That sucks.

I really hope that Congress starts making the right decisions, here. It's shameful how messed up things are, how brinkmanship is destroying America's legacy.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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Re: Wired article on Pu-238 production for space missions
« Reply #8 on: 09/20/2013 11:53 PM »
This may not be Congress being jerks. The problem may be with OMB. I don't know.

I know that it's popular on this board--as in the rest of the country--to blame Congress for everything that's wrong with American politics today. I'd just note that there are some good people in Congress (well, at least their staffs) trying to do things right. That's particularly true when it comes to the planetary science program where the allies are in Congress (not OMB).

I'd also add that there's another possibly very positive development re the Pu-238 in the making. That's contingent upon some other things happening, but it could be a good thing. It's not totally surprising to me, but I can't provide any other details now. Maybe in six months or so we'll know.

Offline EE Scott

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Re: Wired article on Pu-238 production for space missions
« Reply #9 on: 09/21/2013 03:43 AM »
This may not be Congress being jerks. The problem may be with OMB. I don't know.

I know that it's popular on this board--as in the rest of the country--to blame Congress for everything that's wrong with American politics today. I'd just note that there are some good people in Congress (well, at least their staffs) trying to do things right. That's particularly true when it comes to the planetary science program where the allies are in Congress (not OMB).

I'd also add that there's another possibly very positive development re the Pu-238 in the making. That's contingent upon some other things happening, but it could be a good thing. It's not totally surprising to me, but I can't provide any other details now. Maybe in six months or so we'll know.


Hey, a hint of positivity.  I'll take it! Us planetary science buffs are looking for good news wherever we can get it.  When it gets this grim, it's hard not to lash out at the shortsightedness of our representatives (President included).
« Last Edit: 09/21/2013 03:44 AM by EE Scott »
Scott

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Re: Wired article on Pu-238 production for space missions
« Reply #10 on: 09/21/2013 02:43 PM »
If it comes to pass, it will be a glass half full/empty situation, meaning that NASA may still not be better off because the budget isn't there.

That's kinda the story for planetary science. There are a LOT of missions that they can do. Interesting, even relatively small missions with high science quality. But there's no funding.

Offline EE Scott

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Re: Wired article on Pu-238 production for space missions
« Reply #11 on: 09/23/2013 12:16 AM »
If it comes to pass, it will be a glass half full/empty situation, meaning that NASA may still not be better off because the budget isn't there.

That's kinda the story for planetary science. There are a LOT of missions that they can do. Interesting, even relatively small missions with high science quality. But there's no funding.

That is why I am interested in some kind of public-private partnership, where some foundation is somehow able to partner with NASA to get missions done. Even just modest missions; maybe purchase a launch from a smaller provider (less than EELV class) and sell it to NASA for $1.  However since there are currently no foundations who seem to have this type of function in their charter, I guess it's up to me to become hugely wealthy and start my own.  Until then I hope and wait for additional funding to flow back into planetary science.
« Last Edit: 09/23/2013 12:18 AM by EE Scott »
Scott

Offline vulture4

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Re: Wired article on Pu-238 production for space missions
« Reply #12 on: 09/23/2013 02:53 AM »
There are certainly foundations that fund scientific research, but for the most part those concerned with astronomical research focus on ground-based observation, since their funds are limited and ground-based observatoin is much more economical. A rare exception is a private attempt to raise funds for a spacecraft to search for near earth asteroids from a sunward orbit.

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Re: Wired article on Pu-238 production for space missions
« Reply #13 on: 09/23/2013 05:01 PM »
A rare exception is a private attempt to raise funds for a spacecraft to search for near earth asteroids from a sunward orbit.

As much as I would like to see B612 Foundation succeed, I think that they are going to not raise much funding and will shift to advocating government funding/private management of a spacecraft development. Indeed, I already see some signs of that shift in their tone.

Offline DarkenedOne

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Re: Wired article on Pu-238 production for space missions
« Reply #14 on: 09/25/2013 12:35 PM »
Good information. Nevertheless, in the long run wouldn't there be advantages to using a small reactor instead? Launch hazards are greatly reduced since uranium is virtually nontoxic compared to plutonium, power capabilities tend to be higher and fuel consumption rate can be varied to meet mission requirements.

Ultimately there are limits imposed on how small you can build a nuclear reactor that is imposed by the critical mass limit needed for the nuclear chain reaction.  Essentially RTG are ideal for missions that require less than 10 kw.

Offline DarkenedOne

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Re: Wired article on Pu-238 production for space missions
« Reply #15 on: 09/25/2013 01:16 PM »
First of all there are a number of important issues we are talking about here.

1.  Added Plutoium supply is insufficient to maintain current deep space exploration without new technology.  The Mars rover required about 4 kg.  The New Horizons missions required 11 kg.  Cassini required 32,7 kg.  A few calculations will tell you that we cannot sustain our current level of deep space exploration.  NASA hopes that new technology like the ASTG will allow for use to do more with less, but it is still a huge problem.

2.  Human exploration requires significant amounts of Pu-238 as well.  Radioisotope heater units were used in Apollo to provide heat for missions that lasted days.   While small nuclear reactors are probably what is going to be required for outposts, radio isotope heater units are ideal for smaller vehicles such as landers and rovers.  Ultimately if we are to have a real manned spaceflight program that does surface missions we will need significant amounts of this stuff.

3.  The DOD has been looking into using this stuff as well for a number of very useful applications.   We should not assume that nasa is going to get all of it by default.

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Re: Wired article on Pu-238 production for space missions
« Reply #16 on: 09/26/2013 04:34 PM »
I'm going to split these into separate replies because that's how I roll:

First of all there are a number of important issues we are talking about here.

1.  Added Plutoium supply is insufficient to maintain current deep space exploration without new technology.  The Mars rover required about 4 kg.  The New Horizons missions required 11 kg.  Cassini required 32,7 kg.  A few calculations will tell you that we cannot sustain our current level of deep space exploration.  NASA hopes that new technology like the ASTG will allow for use to do more with less, but it is still a huge problem.

I'm now confused by the numbers. The DoE document that was linked in the article says that New Horizons required 8 kg and Curiosity required 11 kg.

http://www.wired.com/images_blogs/wiredscience/2013/09/final72005faqs.pdf

But this NASA document says that the MMRTG used on Curiosity required 4.8 kg:

http://mars.nasa.gov/msl//files/mep/MMRTG_Jan2008.pdf

As for "sustain our current level of space exploration," well, we aren't. Planetary has been cut back. And there was (still is) a vicious cycle with Pu-238: Step 1 "We don't have enough Pu-238 to fly many missions, so don't propose missions that require Pu-238." Step 2 "You have not proposed many missions that require Pu-238, so obviously you don't need much of it, so we will not restart production."

Apparently that cyclic argument was still working in Congress and (sorta) OMB and the only thing that broke us out of it was that NASA was able to successfully (we hope) argue that the existing Pu-238 supply is becoming too weak to be used, and its energy density must be increased in order to make it useable.

As for new technology? We have it. The ASRGs. NASA has built two flight qualified models that are now in storage and the agency would like to fly one of them on a Discovery mission. Except that the Discovery budget is being cut, so there are not many opportunities to fly. Another Catch 22.



Online Blackstar

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Re: Wired article on Pu-238 production for space missions
« Reply #17 on: 09/26/2013 04:47 PM »
2.  Human exploration requires significant amounts of Pu-238 as well.  Radioisotope heater units were used in Apollo to provide heat for missions that lasted days.   While small nuclear reactors are probably what is going to be required for outposts, radio isotope heater units are ideal for smaller vehicles such as landers and rovers.  Ultimately if we are to have a real manned spaceflight program that does surface missions we will need significant amounts of this stuff.

We looked at this when we did our radioisotope power sources (RPS) study in 2009. The Constellation program's requirement was significantly more than the science requirement. It was something like twice as much. That was for a baseline lunar outpost, primarily to act as backup power for the main site. For example, if you had solar or a reactor as your main power source, you'd want something that was totally reliable as backup power. An MMRTG was great for this. In fact several of them would be really nice. I believe that one person I talked to even said that the radiated heat from them would be useful--you could place it near your habitat and it could radiate heat to the habitat (and the radiation risk is pretty much nonexistent). I've got the charts somewhere showing nominal human spaceflight requirements for the Pu-238.

But...

When we were doing the study, we would look at the human spaceflight requirements for the Pu-238 and it looked great. It looked like the human spaceflight program would pay for most of the costs and the science program would just skim some extra Pu-238 off the top and use it for their own missions. But we were not born yesterday. We knew that was an illusion. Some of us knew that Constellation was going to get canceled, or at least severely scaled back very soon.

And within agencies different departments will play games of budgetary chicken. The obvious question was who needed more Pu-238 first, the human spaceflight program or the science program? Well, if you assumed that both were funded for all their requirements (which was a dumb assumption), science would need it sooner than the human spaceflight program, but eventually Constellation would require a lot more. So the human spaceflight program said that they had no plans to fund Pu-238 production restart, because they weren't going to need more until the 2020s or so. That shifted the funding requirement to science. Of course, the science program (planetary) knew this, and they also knew that the human spaceflight requirement would probably disappear. So we all took the base assumption that science was going to have to shoulder the burden for Pu-238 production.

Online Blackstar

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Re: Wired article on Pu-238 production for space missions
« Reply #18 on: 09/26/2013 04:52 PM »
3.  The DOD has been looking into using this stuff as well for a number of very useful applications.   We should not assume that nasa is going to get all of it by default.

That was never the assumption. If you read the article, and this thread, you'll see that "national security requirements" have always been factored into this. There is a total amount of Pu-238 that currently exists, and a certain amount is allocated to NASA, and the remainder is allocated to "national security."

There was a baseline assumption that the NASA Pu-238 belonged to NASA and could not be taken over for national security missions. I believe (and I'm too lazy to check) that around 2001/2 there was suddenly an announcement by the Secretary of Defense that DoD could take some of the NASA Pu-238 if they needed it. There was never a clear explanation why this was, and my suspicion is that it was simply because the Secretary of Defense was a jerk and wanted to build his empire. I believe that policy decision was later reversed.

But stay tuned. As I mentioned earlier, there may be more news on this subject in the next few months.
« Last Edit: 09/26/2013 04:52 PM by Blackstar »

Offline baldusi

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Re: Wired article on Pu-238 production for space missions
« Reply #19 on: 09/28/2013 03:43 AM »
Good news, bad news, some other types?

Online Steven Pietrobon

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Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Blackstar

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Re: Wired article on Pu-238 production for space missions
« Reply #21 on: 03/22/2014 03:54 AM »
Here's an article in Space News about there being only enough Pu238 for Curiosity 2.

http://bt.e-ditionsbyfry.com/publication/?i=201481&utm_source=WhatCountsEmail&utm_medium=Digital%20Issue%200317_14&utm_campaign=Weekly%20Digital%20Issue%20v6_TextOnly&_wcsid=3F1D8990C5FCAF89B15F03172AEE39DAC523C6857676BDD52E6AE64CBF1B101C

That's not really what it says. It's not available for the next Discovery call, but that's a temporary production issue. The stockpile is significant. They have enough for Mars 2020 plus Europa. I thought I posted the inventory information here a week or two ago.
« Last Edit: 03/22/2014 03:56 AM by Blackstar »

Online Steven Pietrobon

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Re: Wired article on Pu-238 production for space missions
« Reply #22 on: 03/22/2014 05:26 AM »
Thanks for the clarification Blackstar. I came to that conclusion after reading this paragraph.

"With Stirling out of the picture, NASA says there will not be enough plutonium-238 ready at the end of the decade to fuel comparatively inefficient Multi-Mission Radioisotope Generators for both the Mars 2020 Rover and the Discovery 13 mission."
« Last Edit: 03/22/2014 05:30 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Blackstar

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Re: Wired article on Pu-238 production for space missions
« Reply #23 on: 03/22/2014 12:39 PM »
Thanks for the clarification Blackstar. I came to that conclusion after reading this paragraph.

"With Stirling out of the picture, NASA says there will not be enough plutonium-238 ready at the end of the decade to fuel comparatively inefficient Multi-Mission Radioisotope Generators for both the Mars 2020 Rover and the Discovery 13 mission."

I have the slides somewhere. I thought I posted them here. I think it works out that by 2020 they will have enough for Mars 2020, Europa, and 2 Discovery/New Frontiers missions. I forget how many MMRTGs that means for the latter. They have a chart that shows all this (it's called something like an offramp chart or something, and it's like a river, showing how much Pu-238 is in the pipeline and then how much gets subtracted for each mission and how much is added when production ramps up, etc.).

One of the questions is when production will get full going. They've found that some of the infrastructure has to be replaced and that will take time. Another issue is the particular power levels required/available for each mission. This stuff ls like a stew, with each mix being a different combination of Pu-238, some old, some slightly old, some less old (but all old), and so they have to do a lot of different balancing.

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Re: Wired article on Pu-238 production for space missions
« Reply #24 on: 03/22/2014 05:16 PM »
Somebody sent it to me and saved me the effort of looking for it. Here it is.

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Re: Wired article on Pu-238 production for space missions
« Reply #25 on: 03/22/2014 10:11 PM »
Okay, to interpret that chart for you a bit--the green stuff is NASA's existing Pu-238. It's green because that means it is essentially hot enough to fuel current MMRTGs and provide enough power. Figure that most of that was manufactured in the late 1980s.

The yellow stuff is the Pu-238 that was made newly available to NASA starting last year. That is older stuff, dating probably from the 1970s into the early 1980s. There's a lot of it, but its energy density is lower, meaning it is cooler. You have to mix that stuff in with newer material (which is hotter) to get the energy density up. (A good question is why the DoE was keeping that material in reserve. What was it for? My suspicion is that it had a nuclear weapons use--not directly, because bomb grade material is Pu-239--but as some kind of add-in material.)

The hot stuff (red) is the newly manufactured stuff.

There is a version of this chart (I have it somewhere) that takes away both the red and the yellow. You can see the effects pretty easily--enough material for Mars 2020 and maybe 4 MMRTGs. Considering that a Europa mission requires (I think) at least 3, you can see that without the newly acquired material, and the newly manufactured material, NASA could do Europa and Mars 2020 and maybe have 1 MMRTG left over. Or NASA could do Mars 2020 and a couple of Discovery or New Frontiers missions.

(Caveat: this is all variable. Even though you have a big slice there that is colored green, it is not all equal in power. Some is newer and higher energy density, and some is older and lower energy density. It all depends upon how it gets mixed together, like a stew. Simply put, although we can talk broadly about X number of MMRTGs being available, the reality is that the number is squishy, and you could get one more or one less.)
« Last Edit: 03/23/2014 02:31 PM by Blackstar »

Offline Hog

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Re: Wired article on Pu-238 production for space missions
« Reply #26 on: 03/23/2014 08:11 PM »
Okay, to interpret that chart for you a bit--the green stuff is NASA's existing Pu-238. It's green because that means it is essentially hot enough to fuel current MMRTGs and provide enough power. Figure that most of that was manufactured in the late 1980s.

The yellow stuff is the Pu-238 that was made newly available to NASA starting last year. That is older stuff, dating probably from the 1970s into the early 1980s. There's a lot of it, but its energy density is lower, meaning it is cooler. You have to mix that stuff in with newer material (which is hotter) to get the energy density up. (A good question is why the DoE was keeping that material in reserve.
What was it for? My suspicion is that it had a nuclear weapons use--not directly, because bomb grade material is Pu-239--but as some kind of add-in material.)

Nuclear PAL (Permissive Action Links) that disallow unauthorized detonation of many nuclear weapons use Pu-238 RTG's.  They are small and wouldnt need to be very hot.
« Last Edit: 03/23/2014 08:12 PM by Hog »
Paul

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Re: Wired article on Pu-238 production for space missions
« Reply #27 on: 03/23/2014 10:08 PM »

Nuclear PAL (Permissive Action Links) that disallow unauthorized detonation of many nuclear weapons use Pu-238 RTG's.  They are small and wouldnt need to be very hot.

I don't think that's it. That is a publicly acknowledged use. I think the stockpile came from reserves for some other use.

Online Steven Pietrobon

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Re: Wired article on Pu-238 production for space missions
« Reply #28 on: 03/24/2014 01:53 AM »
Someone sent me the link for where the above slide came from

http://www.lpi.usra.edu/opag/jan2014/presentations/6_Green.pdf

I've attached the document as well. We see two MMRTGs being produced in 2018 and four MMRTGs produced in 2024. Are these all for NASA missions?

Also attached is a Europa Clipper presentation. That currently has five MMRTGs, but they are looking at reducing that to four.

http://www.lpi.usra.edu/opag/jan2014/presentations/9_Clipper.pdf
« Last Edit: 03/24/2014 02:04 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

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Re: Wired article on Pu-238 production for space missions
« Reply #29 on: 03/24/2014 03:17 AM »
Someone sent me the link for where the above slide came from

http://www.lpi.usra.edu/opag/jan2014/presentations/6_Green.pdf

I've attached the document as well. We see two MMRTGs being produced in 2018 and four MMRTGs produced in 2024. Are these all for NASA missions?

Also attached is a Europa Clipper presentation. That currently has five MMRTGs, but they are looking at reducing that to four.

http://www.lpi.usra.edu/opag/jan2014/presentations/9_Clipper.pdf

They are actually producing one per year. Just finished the one for Mars 2020. What you're seeing is the ones used for missions, but they should have more sitting around, unfueled. NASA is producing them at the rate of one per year to maintain the skillset. (I suspect that the actual production rate is a bit below one per year, but that's what I was told.)

I have a few other related presentations that I'll post when I get to the office. They cover similar things. I've also got a flyer on the eMMRTG (for "enhanced") but I haven't looked at what that is or how much it increases the power level.


Offline Hog

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Re: Wired article on Pu-238 production for space missions
« Reply #30 on: 03/24/2014 01:04 PM »

Nuclear PAL (Permissive Action Links) that disallow unauthorized detonation of many nuclear weapons use Pu-238 RTG's.  They are small and wouldnt need to be very hot.

I don't think that's it. That is a publicly acknowledged use. I think the stockpile came from reserves for some other use.
Who knows, I no longer have my security clearance. Do you have any guesses? If its from a non publically acknowledged use, that's all we have are guesses, though educated guesses are exciting fodder for discussion.

BTW Thanks for that illustration, it is a neat package of info.  There might be some future "donations" of fuel, but again, who knows?
Paul

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Re: Wired article on Pu-238 production for space missions
« Reply #31 on: 03/24/2014 03:58 PM »
Who knows, I no longer have my security clearance. Do you have any guesses?

No. I have not designed nuclear weapons since grade school.


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Re: Wired article on Pu-238 production for space missions
« Reply #32 on: 03/24/2014 03:59 PM »
These two presentations have a lot of information on this subject.

Offline arachnitect

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Re: Wired article on Pu-238 production for space missions
« Reply #33 on: 03/24/2014 05:53 PM »

Nuclear PAL (Permissive Action Links) that disallow unauthorized detonation of many nuclear weapons use Pu-238 RTG's.  They are small and wouldnt need to be very hot.

I don't think that's it. That is a publicly acknowledged use. I think the stockpile came from reserves for some other use.
Who knows, I no longer have my security clearance. Do you have any guesses? If its from a non publically acknowledged use, that's all we have are guesses, though educated guesses are exciting fodder for discussion.

BTW Thanks for that illustration, it is a neat package of info.  There might be some future "donations" of fuel, but again, who knows?

US supposedly ran a pretty involved undersea surveillance program at one point (Operation Ivy Bells) that would have used RTGs on eavesdropping equipment. Perhaps that mission has become obsolete from new communications technology (and other countries figuring it out), and therefore DOE no longer needs to stockpile material for it.

That said, Ivy Bells was compromised 30 years ago, so I don't know why DOE didn't hand over the Pu before now.

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Re: Wired article on Pu-238 production for space missions
« Reply #34 on: 03/24/2014 09:07 PM »
US supposedly ran a pretty involved undersea surveillance program at one point (Operation Ivy Bells) that would have used RTGs on eavesdropping equipment. Perhaps that mission has become obsolete from new communications technology (and other countries figuring it out), and therefore DOE no longer needs to stockpile material for it.

That said, Ivy Bells was compromised 30 years ago, so I don't know why DOE didn't hand over the Pu before now.

My point is that I have a strong suspicion that this newly acquired (but older) material was from a use that has not been publicly revealed before. I don't know what that is, but I suspect it's weapons-related.

I suspect that if something like the Ivy Bells mission is still underway they have a better way of powering them, such as long-lived underwater batteries. There are many good reasons to not leave Pu-238 in places where somebody might recover it, even by accidentally picking it up in a fishing net.

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Re: Wired article on Pu-238 production for space missions
« Reply #35 on: 03/25/2014 02:06 AM »

Online Steven Pietrobon

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Re: Wired article on Pu-238 production for space missions
« Reply #36 on: 03/25/2014 06:15 AM »
Thanks Blackstar. We can deduce from page 24 of the APL presentation that 11 RTG's have been used for 9 non-NASA missions.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

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Re: Wired article on Pu-238 production for space missions
« Reply #37 on: 03/25/2014 01:22 PM »
Thanks Blackstar. We can deduce from page 24 of the APL presentation that 11 RTG's have been used for 9 non-NASA missions.

That would include the LES satellites for DoD. Also Transit.
« Last Edit: 03/25/2014 01:22 PM by Blackstar »

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Re: Wired article on Pu-238 production for space missions
« Reply #38 on: 03/26/2014 05:57 AM »
Thanks Blackstar. OK, here is my table of the missions and RTG's but they don't match up with the APL presentation. The only number that matches is the total number of missions of 27. These numbers do not seem to include any classified missions. Can anyone see any errors?

Non-NASA Missions
-----------------
 1) Transit 4A    SNAP-3B     (1)
 2) Transit 4B    SNAP-3B     (1)
 3) Transit 5BN-1 SNAP-9A     (1)
 4) Transit 5BN-2 SNAP-9A     (1)
*5) Transit 5BN-3 SNAP-9A     (1)
 6) Triad-01-1X   Transit-RTG (1)
 7) LES 8         MHW-RTG     (2)
 8) LES 9         MHW-RTG     (2)

Total Non-NASA Missions:  8 (APL  9)
Number of Non-NASA RTGs: 10 (APL 11)

NASA Missions
-------------
*1) Nimbus B      SNAP-19B    (1)
 2) Nimbus III    SNAP-19B    (1)
 3) Apollo 12     SNAP-27     (1)
 4) Apollo 13     SNAP-27     (1)
 5) Apollo 14     SNAP-27     (1)
 6) Apollo 15     SNAP-27     (1)
 7) Apollo 16     SNAP-27     (1)
 8) Apollo 17     SNAP-27     (1)
 9) Pioneer 10    SNAP-19     (4)
10) Pioneer 11    SNAP-19     (4)
11) Viking 1      SNAP-19     (2)
12) Viking 2      SNAP-19     (2)
13) Voyager 1     MHW RTG     (3)
14) Voyager 2     MHW RTG     (3)
15) Galileo       GPHS RTG    (2)
16) Ulysses       GPHS RTG    (1)
17) Cassini       GPHS RTG    (3)
18) New Horizons  GPHS RTG    (1)
19) Curiosity     MMRTG       (1)

Total NASA Missions: 19 (APL 18)
Number of NASA RTGs: 34 (APL 35)

Total Missions: 27 (APL 27)
Number of RTGs: 44 (APL 46)

* Launch failure
« Last Edit: 03/26/2014 06:05 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

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Re: Wired article on Pu-238 production for space missions
« Reply #39 on: 03/26/2014 10:42 AM »
Maybe you are missing this one http://en.wikipedia.org/wiki/SNAP-10A ?

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Re: Wired article on Pu-238 production for space missions
« Reply #40 on: 03/27/2014 05:33 AM »
Thanks cartman, but SNAP-10A is a nuclear reactor, not a radioisotope thermolelectric generator (RTG).
« Last Edit: 03/27/2014 05:47 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

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Re: Wired article on Pu-238 production for space missions
« Reply #41 on: 03/27/2014 04:35 PM »
Total Non-NASA Missions:  8 (APL  9)
Number of Non-NASA RTGs: 10 (APL 11)


I talked to Ralph. He miscounted. Your number is right.

Offline vulture4

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Re: Wired article on Pu-238 production for space missions
« Reply #42 on: 03/28/2014 01:06 PM »
During the decadal survey we commissioned a study on small fission power reactors. I'm attaching it here.

In all honesty, we did this because John Casani requested it and Casani is a legend (and nice guy). But I think there was little support for it among the planetary science community. At the very least they wanted the Pu-238 production line restarted so that they could consider missions that had been proposed in the recent past. Small fission reactors would be nice to have for more ambitious planetary missions, but there are no realistic missions that could use them that anybody could foresee in the next several decades.

Thanks, a very interesting study. Still, spacecraft reactor designs have been around for decades. If power requirements increase even moderately (i.e. for nuclear electric propulsion) isn't there a point where it makes sense to pursue reactor development? The alternative is to consider our outer planet probes permanently constrained to our ability to produce RTGs.
« Last Edit: 03/28/2014 01:08 PM by vulture4 »

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Re: Wired article on Pu-238 production for space missions
« Reply #43 on: 03/28/2014 01:31 PM »
Thanks cartman, but SNAP-10A is a nuclear reactor, not a radioisotope thermolelectric generator (RTG).
oops, yes you're right, my bad :)

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Re: Wired article on Pu-238 production for space missions
« Reply #44 on: 03/28/2014 01:33 PM »
It's a pity we don't use the Thorium fuel cycle in our commercial reactors. One of the waste byproducts of the reactor is non-weapons grade plutonium that can be used in Pu-238 applications. We'd never run out. Some redesign of the RTG's would be needed of course, but there would never be another problem with the fuel supply.
« Last Edit: 03/28/2014 01:36 PM by clongton »
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline vulture4

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Re: Wired article on Pu-238 production for space missions
« Reply #45 on: 03/28/2014 02:40 PM »
It's a pity we don't use the Thorium fuel cycle in our commercial reactors. One of the waste byproducts of the reactor is non-weapons grade plutonium that can be used in Pu-238 applications. We'd never run out. Some redesign of the RTG's would be needed of course, but there would never be another problem with the fuel supply.
India is investing rather heavily in the thorium cycle, which is a breeder cycle that requires reprocessing, which would be hard to do in the US as we have (SFAIK) no reprocessing capability. perhaps they would be interested in exporting the plutonium.

Offline DLK

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Re: Wired article on Pu-238 production for space missions
« Reply #46 on: 03/30/2014 02:46 AM »
The molten-salt thorium breeder reactor concept eliminates a great deal of the complexity associated with fuel reprocessing, as it can be done while the salt is in a liquid state. Also, there are much less issues with the generation of the long-lived transuranics that plague current light-water U-235 burners. There's a lot to like in the potential of this technology.

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Re: Wired article on Pu-238 production for space missions
« Reply #47 on: 03/30/2014 04:23 AM »
Questions.

1) The 2020 startup of fresh Pu-238 will produce approx 1kg./year.  Is the entire new Pu-238 production available to NASA, or is DOE actually producing fresh Pu-238 per year at a higher rate for "other" non-NASA uses?

2) Does this future fresh approx. 1kg/year for NASA production limit any possible human/SLS mission to Mars? A more basic wording, will a human/SLS mission to Mars require any sort of Plutonium power sources?

Background
http://en.wikipedia.org/wiki/Pu-238

Thank you.
« Last Edit: 03/30/2014 04:41 AM by Hog »
Paul

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Re: Wired article on Pu-238 production for space missions
« Reply #48 on: 03/30/2014 04:08 PM »
Questions.

1) The 2020 startup of fresh Pu-238 will produce approx 1kg./year.  Is the entire new Pu-238 production available to NASA, or is DOE actually producing fresh Pu-238 per year at a higher rate for "other" non-NASA uses?

2) Does this future fresh approx. 1kg/year for NASA production limit any possible human/SLS mission to Mars? A more basic wording, will a human/SLS mission to Mars require any sort of Plutonium power sources?

1-I thought it was more like 1.5 kg. The material is for NASA use. NASA is paying for it after all. DoE is not producing any other material. In fact, the infrastructure is really crumbling and they need to rebuild it. However, I suspect that NASA's memorandum of understanding with DoE allows DoE to claim that material for other use if necessary (for national security purposes).

2-Human missions to the Moon and Mars will probably require RTGs as backup power supplies. That would increase the need for more material and NASA will have to pay for it. Restarting production of any material at all is an important first step. But it is my understanding that increasing production from the rate that they have decided on will be a significant expense. That will require more material.

Offline Hog

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Re: Wired article on Pu-238 production for space missions
« Reply #49 on: 03/30/2014 06:29 PM »
Questions.

1) The 2020 startup of fresh Pu-238 will produce approx 1kg./year.  Is the entire new Pu-238 production available to NASA, or is DOE actually producing fresh Pu-238 per year at a higher rate for "other" non-NASA uses?

2) Does this future fresh approx. 1kg/year for NASA production limit any possible human/SLS mission to Mars? A more basic wording, will a human/SLS mission to Mars require any sort of Plutonium power sources?

1-I thought it was more like 1.5 kg. The material is for NASA use. NASA is paying for it after all. DoE is not producing any other material. In fact, the infrastructure is really crumbling and they need to rebuild it. However, I suspect that NASA's memorandum of understanding with DoE allows DoE to claim that material for other use if necessary (for national security purposes).

2-Human missions to the Moon and Mars will probably require RTGs as backup power supplies. That would increase the need for more material and NASA will have to pay for it. Restarting production of any material at all is an important first step. But it is my understanding that increasing production from the rate that they have decided on will be a significant expense. That will require more material.

1) Other souces do say approx 1.5 kg, I was going by that nice graphic that shows old, Soviet purchased, "older" then more usable material after upblending, along with the newly produced materials, that graphic stated approx 1kg.

Thanks for your input, and I agree that restarting production is an important 1st step.
Paul

Offline Star One

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Wired article on Pu-238 production for space missions
« Reply #50 on: 03/11/2015 03:21 PM »
Finally something of an update on this issue.

Quote
In 2012, after a few false starts, the Obama administration got Congress to go along with a plutonium-238 restart, under the condition that NASA pay to repair aging DOE infrastructure at the Los Alamos National Laboratory in Los Alamos, New Mexico. When the repairs are complete, the Energy Department will start producing 1.5 kilograms of plutonium-238 a year.

“The question is when that starts,” Caponiti told outer-planets scientists. She said that even if production does not immediately ramp up to 1.5 kilograms a year when the new equipment comes online, “something less than the full production rate” could still support NASA’s needs.

This is because plutonium-238 decays over time (its half-life is just under 90 years), meaning the longer the fuel is stored, the more energy it loses. Of the 35 kilograms reserved in the U.S. stockpile for civil space programs, 17 kilograms meet DOE’s minimum required energy levels. The other 18 kilograms do not, but could be refreshed by an infusion of newly refined plutonium-238.

Even if production gets off to a slow start, any new plutonium-238 helps and “is going to have an immediate effect on missions,” for the better, Caponiti said.

Also at the meeting, Ralph McNutt, a planetary scientist who led a NASA-chartered study of the agency’s future nuclear needs, briefed the group on the results.

The Nuclear Power Assessment Study examined both robotic and crewed mission concepts planned by NASA and the broader space science community over the next 20 years and concluded “nuclear power systems are certainly going to be needed during that time period,” McNutt said.

His presentation marked the first public summary of the study since its November completion. The 185-page report is the product of about six months of work and has not been released because of security concerns, McNutt said.

http://spacenews.com/u-s-plutonium-stockpile-good-for-two-more-nuclear-batteries-after-mars-2020/#sthash.iL4uWZy4.dpuf
« Last Edit: 03/11/2015 03:29 PM by Star One »

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Re: Wired article on Pu-238 production for space missions
« Reply #51 on: 07/30/2015 05:54 PM »
A further update.

Ohio Senators Call for Plutonium Power Report with New Bill
Quote
Under the Efficient Space Exploration Act, filed July 22 by U.S. Sens. Sherrod Brown (D-Ohio) and Robert Portman (R-Ohio), NASA and the White House Office of Science and Technology Policy would take the lead on a study to determine the space agency’s exact requirements for radioisotope power systems, the plutonium-238 that fuels them, and the risks to planned missions if those needs are not met.

The bill — filed at a time when the U.S. plutonium-238 supply is dwindling and budget cuts forced NASA to cancel development of a more efficient nuclear battery under development at a NASA facility in Ohio — also directs the White House to ensure the Department of Energy, which is responsible for U.S. plutonium production, does not overcharge NASA for plutonium infrastructure upgrades at DOE’s Los Alamos National Laboratory in New Mexico.

- See more at: http://spacenews.com/ohio-senators-call-for-plutonium-power-report-with-new-bill/#sthash.k9YzmC3w.dpuf

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Re: Wired article on Pu-238 production for space missions
« Reply #52 on: 07/30/2015 07:29 PM »
Read the article. It looks like some people in Ohio at the company and probably the NASA field center have been bending the ears of their senators and that's where this comes from. They're not interested in production, they're interested in restarting the ASRG program. I don't see that happening because it requires money that NASA doesn't have.

Recently NASA has talked about restarting Pu-238 production by the end of this decade or even by 2020, which is really puzzling considering that it was originally supposed to start around 15-16. Either it's costing more money of NASA's budget is being short-changed (or both). I also wonder if taking the Europa mission out of the mix reduced the pressure to actually restart production--if true, that's typical, and it has been the problem all along: everybody is always looking for another excuse to kick the can down the road.

I helped run the last big study on this issue and I'm not sure why another one is really needed. The solution is pretty straightforward, just put some money into it and get production restarted.

Offline NovaSilisko

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Re: Wired article on Pu-238 production for space missions
« Reply #53 on: 07/31/2015 04:23 AM »
[...] just put some money into it [...]

Put money into it? Unthinkable... :P
« Last Edit: 07/31/2015 05:39 PM by NovaSilisko »

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Re: Wired article on Pu-238 production for space missions
« Reply #54 on: 07/31/2015 05:56 PM »

Read the article. It looks like some people in Ohio at the company and probably the NASA field center have been bending the ears of their senators and that's where this comes from. They're not interested in production, they're interested in restarting the ASRG program. I don't see that happening because it requires money that NASA doesn't have.

Recently NASA has talked about restarting Pu-238 production by the end of this decade or even by 2020, which is really puzzling considering that it was originally supposed to start around 15-16. Either it's costing more money of NASA's budget is being short-changed (or both). I also wonder if taking the Europa mission out of the mix reduced the pressure to actually restart production--if true, that's typical, and it has been the problem all along: everybody is always looking for another excuse to kick the can down the road.

I helped run the last big study on this issue and I'm not sure why another one is really needed. The solution is pretty straightforward, just put some money into it and get production restarted.

Yes that was my reading too, it seemed more about ASRG than PU-238 production. Pretty disappointing as can I feel like saying can we not move on from ASRG and just concentrate on getting production going again.

Offline vulture4

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Re: Wired article on Pu-238 production for space missions
« Reply #55 on: 08/02/2015 10:02 PM »
I agree. Even human BEO exploration will depend on nuclear energy. If we cannot even produce Pu-238 these more ambitious projects look infeasible.

Offline DarkenedOne

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Re: Wired article on Pu-238 production for space missions
« Reply #56 on: 08/04/2015 01:53 AM »
A further update.

Ohio Senators Call for Plutonium Power Report with New Bill
Quote
Under the Efficient Space Exploration Act, filed July 22 by U.S. Sens. Sherrod Brown (D-Ohio) and Robert Portman (R-Ohio), NASA and the White House Office of Science and Technology Policy would take the lead on a study to determine the space agency’s exact requirements for radioisotope power systems, the plutonium-238 that fuels them, and the risks to planned missions if those needs are not met.

The bill — filed at a time when the U.S. plutonium-238 supply is dwindling and budget cuts forced NASA to cancel development of a more efficient nuclear battery under development at a NASA facility in Ohio — also directs the White House to ensure the Department of Energy, which is responsible for U.S. plutonium production, does not overcharge NASA for plutonium infrastructure upgrades at DOE’s Los Alamos National Laboratory in New Mexico.

- See more at: http://spacenews.com/ohio-senators-call-for-plutonium-power-report-with-new-bill/#sthash.k9YzmC3w.dpuf

The problem I have with that article is the exact requirements phrase.  The simple fact of the matter is that scientists are not going to propose missions or approve missions that rely on resources that are unavailable.  On top of that we have not even begun to really consider the requirements for manned missions, which are generally substantially greater.  The fact of the matter is that the best course of action for space exploration is to overestimate and overproduce.  I would much rather us produce more than we need and end up wasting some of it then to restrict out solar system exploration because of it.  Besides my guess is that we will have no trouble selling it for substantially more than our cost to produce if we find that we have a surplus. 

Offline Dante80

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Re: Wired article on Pu-238 production for space missions
« Reply #57 on: 08/09/2015 07:15 AM »
How about Americium-241? It can be a decent candidate, and its a lot more easily available (due to it being part of commercial reactor nuclear waste).

Also, in the first page there was a post about small nuclear reactors, and the fact that the power outputs they give would be unneeded in space exploration in the following decades. The truth is that this is not really the case. I mean, a small reactor is not easy to do but there is definitely science it enables. And that is ice/ground penetrating SAR arrays that would put MARSIS and SHARAD to shame, and reveal us a lot of things in a lot of different targets.

Also, a small reactor could enable features like a high bandwidth data transmitter, or nuclear electric propulsion..

Anyone remember JIMO?
« Last Edit: 08/09/2015 07:24 AM by Dante80 »

Offline WindnWar

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Re: Wired article on Pu-238 production for space missions
« Reply #58 on: 08/09/2015 04:39 PM »
Has there ever been an RTG built with AM-241? From what I can find it only has about 1/4 the power generating ability of Pu-238, though I was unable to find an exact watt to gram percentage. RTG efficiency goes down the lower the temp differential of the junctions are. That would tend to mean a much larger and heavier RTG, though it does have the advantage of being readily available material with almost 5 times the half life and only needs slightly more shielding.

Offline WindnWar

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Re: Wired article on Pu-238 production for space missions
« Reply #59 on: 08/09/2015 05:08 PM »
I found this study on use of it in the sterling generators for possible lunar missions. Not much on use in RTG's though ESA has been looking into it. Looks like about double the mass required for it by doubling the number GPHS modules to get the same heat output as PU-238, though the advantage is over a 10 year span there is basically no power drop due to the long half-life.

If only we had a sterling generator.

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Re: Wired article on Pu-238 production for space missions
« Reply #60 on: 08/27/2015 01:11 PM »
You have to keep pushing - even when you get your way on Capital Hill.  Good news if/when it happens.  It would be nice if all of our deep space missions had Pu238 as an option if they desired.

http://spacenews.com/doe-to-crank-out-new-plutonium-238-in-2019/

Eventually cranking out 1.5 kilos a year.

Hooray Deep Space Science.

Respectfully,
Andrew Gasser

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Re: Wired article on Pu-238 production for space missions
« Reply #61 on: 12/09/2017 03:38 PM »
A 2008 JPL briefing on Pu-238 production and requirements. You can look at this and see how far we've progressed. (I may have an original, not scanned, version of this file. If so, I'll swap them out.)

Note: this is a HUGE file.
« Last Edit: 12/09/2017 06:49 PM by Blackstar »

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Re: Wired article on Pu-238 production for space missions
« Reply #62 on: 12/10/2017 12:42 PM »
There's also some info from April 2016 here:

http://fiso.spiritastro.net/telecon/Wham_4-20-16/


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Re: Wired article on Pu-238 production for space missions
« Reply #63 on: 12/31/2017 05:57 PM »
And what of Kilopower? There was supposed the be a Q4 test, so anyone hear a result? Seems it could make Pu moot.

https://energy.gov/articles/powering-nasa-s-human-reach-red-planet

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170002010.pdf
« Last Edit: 12/31/2017 05:58 PM by docmordrid »
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Re: Wired article on Pu-238 production for space missions
« Reply #64 on: 12/31/2017 06:24 PM »
I haven't seen this article discussed yet.

https://www.space.com/36217-plutonium-238-nuclear-spacecraft-fuel-production.html

Apparently there is another effort being led by a private company to start an alternative production line to the DOE one that will utilize Canadian reactors. Their goal is to produce 5 kilos per year.
« Last Edit: 12/31/2017 06:25 PM by spacetraveler »

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