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I appreciate that science cannot operate in isolation of the rest of the world, what with all the economic and political realities and such. However, learning

I appreciate that science cannot operate in isolation of the rest of the world, what with all the economic and political realities and such. However, learning that politics was the reason to use an inferior power source for Philae makes me sad. Can anyone shed more light on what type of political problems would using RTG create? Something about weapons grade plutonium, perhaps? Or this being an European project, and we cannot possibly source the materials from the US? Or (and I hope this is not it) green “solar good, nuclear bad” dogma?

ohyes 11y ago
It's the last thing.
cjensen 11y ago
The concern was that performing a slingshot around Earth with a RTG-equiped probe has risks. If early in the mission the probe loses the ability to guide itself, then the probe may be off course enough to hit Earth. The Cassini mission to Saturn did this with an RTG, and there was a significant outcry about the plan.[1] [1] https://en.wikipedia.org/wiki/Cassini–Huygens#Plutonium_power_source https://en.wikipedia.org/wiki/Cassini–Huygens#Plutonium_powe...
- sillysaurus3 11y ago
  "Had there been any malfunction causing the Cassini space probe to collide with the Earth, NASA's complete environmental impact study estimated that, in the worst case (with an acute angle of entry in which Cassini would gradually burn up), a significant fraction of the 33 kg of plutonium-238 inside the RTGs would have been dispersed into the Earth's atmosphere so that up to five billion people (i.e. almost the entire terrestrial population) could have been exposed, causing up to an estimated 5,000 additional cancer deaths (0.0005 per cent, i.e. a fraction 0.000005, of 1 billion cancer deaths expected anyway from other causes), but the chance of that happening were less than one in one million." Would it be true to say that your loved ones are thousands of times more likely to die in a car crash than in the worst-case scenario of this project? This is a stupid reason for having an outcry.
  - DanBC 11y ago
    but we know from all those "the pig that wants to be eaten" philosophy questions that this stupid outcry is normal and predictable. More interesting would be how to present information to reduce the outcry.
  - cjensen 11y ago
    To be clear: I'm describing the outcry, not expressing an opinion on it.
  - GFK_of_xmaspast 11y ago
    If I read that correctly that there's a one-in-a-million chance of killing 5k people, the expected number of deaths over all alternative universes is 1/200. Additionally, one has to consider the non-plutonic fallout and its consequences of NASA as an agency and space exploration in general.
  - elorant 11y ago
    There’s a huge antiscience group of people out there. Let’s just not give them yet another excuse to attack science. They could inflate numbers and make it sound like NASA is endangering the health of millions of people for generations to come. We’ve heard crap like that before.
    - CamperBob2 11y ago
      Sadly, the particular antiscience group that tried to stop the Cassini launch was more or less led by a popular, (then) well-respected physicist, Michio Kaku. [1] For that reason, his name should not be forgotten by posterity, the way it was almost forgotten by me until this thread popped up. [1] http://prop1.org/2000/cassini/9707kaku.htm http://prop1.org/2000/cassini/9707kaku.htm
  - vacri 11y ago
    > This is a stupid reason for having an outcry. What about "Let's add risk to strangers' lives so we can look at a comet slightly longer"?. Throw in that 'one in one million' is a number pulled from the air to represent an opinion, not calculated mathematically, and that launching probes happens multiple times, not as a once-off event. Let's keep things in perspective here. What happens if that burnup happens over a country like Russia or China? And if you're going to make the "well, only 5000 people would die" argument, then you've lost already. Out of the global population that live and work in buildings, the World Trade Center attacks killed fewer than 5000 people. Overzealous police shooting people in the streets? Bah, it's hardly anyone, by the numbers. Wildfire sweeps through the state, killing 50 people? Drop in the ocean compared to car deaths, why is anyone concerned? "They were going to die anyway" is a pretty callous argument that can be used against anything. I mean, if we're arguing for science here, then we should also be pointing out the flaws in the quoted paragraph - it doesn't matter how many other deaths are attributable to cancer (and doubly so because cancer isn't a single thing anyway). Mentioning that statistic in this context is purely political and poor science. I say all this because the process of cutting edge science is necessarily political. You see it in academia, you see it in industry, and you see it in government funding.
AckSyn 11y ago
> I appreciate that science cannot operate in isolation of the rest of the world I can't. It's absolutely atrocious they're limited because of the shortsightedness people have. I get it, we can't live in a moral vacuum, but I'm not talking about human experimentation but the best method of producing energy is unavailable because some people are idiots. /rant
david-given 11y ago
My understanding is that it's primarily a safety issue: these long-duration missions tend to have to get delta-V boosts by slingshotting around the Earth. (Rosetta did this three times. And a slingshot around Mars once.) While the RTG capsule is robust enough to survive a launch failure intact, it's not robust enough to survive reentry at interplanetary speeds if the slingshot goes wrong. It's not like we don't have tonnes of vapourised plutonium in the atmosphere anyway, but that's no excuse for adding more. Plus, the kind of plutonium that goes into an RTG is fabulously expensive, not just because it doesn't occur in nature and has to be made via transmutation, but because it makes handling so much more complicated. They'll have done the cost-benefit analysis and decided it simply wasn't worth it. (Also, RTGs are big and heavy. New Horizons, which is a really small spacecraft, has a 50kg RTG. Philae only massed 21kg.)
- imglorp 11y ago
  There's probably plenty of human risk transporting it to the launcher, as well, such as a road accident or having it be stolen.
  - ars 11y ago
    > such as a road accident No, not really. They are pretty safe - you can hold one in your hand without a problem (barring a burn - they get hot). A road accident would do nothing harmful at all. > having it be stolen That strikes me as pretty unlikely - they don't exactly drive on public roads.
    - saboot 11y ago
      We drive nuclear missiles on public roads, with enough security anything is doable.
      - eco 11y ago
        Yep. An example: https://www.youtube.com/watch?v=bCwlV_94kPE https://www.youtube.com/watch?v=bCwlV_94kPE
TrevorJ 11y ago
To be fair, there are real world safety considerations when putting radioactive material into orbit. It's not just a knee jerk reaction, in all likelihood. The risk for Cassini was calculated at 1:1400 (For context, humans have launched something like 8000 man made objects into orbit). That's certainly acceptable when there's no other reasonable way to provide the power that the mission profile requires, but it makes sense that they would go with a more conventional source where possible.
InclinedPlane 11y ago
ESA is multinational and some member countries are very opposed to nuclear technology in any form. Aside from the fact that Europe generally lacks the ability to manufacture Pu-238 or RTGs in general. Britain is looking at developing RTG technology on its own, possibly using Am-241, which might shake things up. It's still a hard problem with so many member countries involved.

ohyes 11y ago

It's the last thing.

cjensen 11y ago

The concern was that performing a slingshot around Earth with a RTG-equiped probe has risks. If early in the mission the probe loses the ability to guide itself, then the probe may be off course enough to hit Earth. The Cassini mission to Saturn did this with an RTG, and there was a significant outcry about the plan.[1] [1] https://en.wikipedia.org/wiki/Cassini–Huygens#Plutonium_power_source https://en.wikipedia.org/wiki/Cassini–Huygens#Plutonium_powe...

sillysaurus3 11y ago
"Had there been any malfunction causing the Cassini space probe to collide with the Earth, NASA's complete environmental impact study estimated that, in the worst case (with an acute angle of entry in which Cassini would gradually burn up), a significant fraction of the 33 kg of plutonium-238 inside the RTGs would have been dispersed into the Earth's atmosphere so that up to five billion people (i.e. almost the entire terrestrial population) could have been exposed, causing up to an estimated 5,000 additional cancer deaths (0.0005 per cent, i.e. a fraction 0.000005, of 1 billion cancer deaths expected anyway from other causes), but the chance of that happening were less than one in one million." Would it be true to say that your loved ones are thousands of times more likely to die in a car crash than in the worst-case scenario of this project? This is a stupid reason for having an outcry.
- DanBC 11y ago
  but we know from all those "the pig that wants to be eaten" philosophy questions that this stupid outcry is normal and predictable. More interesting would be how to present information to reduce the outcry.
- cjensen 11y ago
  To be clear: I'm describing the outcry, not expressing an opinion on it.
- GFK_of_xmaspast 11y ago
  If I read that correctly that there's a one-in-a-million chance of killing 5k people, the expected number of deaths over all alternative universes is 1/200. Additionally, one has to consider the non-plutonic fallout and its consequences of NASA as an agency and space exploration in general.
- elorant 11y ago
  There’s a huge antiscience group of people out there. Let’s just not give them yet another excuse to attack science. They could inflate numbers and make it sound like NASA is endangering the health of millions of people for generations to come. We’ve heard crap like that before.
  - CamperBob2 11y ago
    Sadly, the particular antiscience group that tried to stop the Cassini launch was more or less led by a popular, (then) well-respected physicist, Michio Kaku. [1] For that reason, his name should not be forgotten by posterity, the way it was almost forgotten by me until this thread popped up. [1] http://prop1.org/2000/cassini/9707kaku.htm http://prop1.org/2000/cassini/9707kaku.htm
- vacri 11y ago
  > This is a stupid reason for having an outcry. What about "Let's add risk to strangers' lives so we can look at a comet slightly longer"?. Throw in that 'one in one million' is a number pulled from the air to represent an opinion, not calculated mathematically, and that launching probes happens multiple times, not as a once-off event. Let's keep things in perspective here. What happens if that burnup happens over a country like Russia or China? And if you're going to make the "well, only 5000 people would die" argument, then you've lost already. Out of the global population that live and work in buildings, the World Trade Center attacks killed fewer than 5000 people. Overzealous police shooting people in the streets? Bah, it's hardly anyone, by the numbers. Wildfire sweeps through the state, killing 50 people? Drop in the ocean compared to car deaths, why is anyone concerned? "They were going to die anyway" is a pretty callous argument that can be used against anything. I mean, if we're arguing for science here, then we should also be pointing out the flaws in the quoted paragraph - it doesn't matter how many other deaths are attributable to cancer (and doubly so because cancer isn't a single thing anyway). Mentioning that statistic in this context is purely political and poor science. I say all this because the process of cutting edge science is necessarily political. You see it in academia, you see it in industry, and you see it in government funding.

AckSyn 11y ago

> I appreciate that science cannot operate in isolation of the rest of the world I can't. It's absolutely atrocious they're limited because of the shortsightedness people have. I get it, we can't live in a moral vacuum, but I'm not talking about human experimentation but the best method of producing energy is unavailable because some people are idiots. /rant

david-given 11y ago

My understanding is that it's primarily a safety issue: these long-duration missions tend to have to get delta-V boosts by slingshotting around the Earth. (Rosetta did this three times. And a slingshot around Mars once.) While the RTG capsule is robust enough to survive a launch failure intact, it's not robust enough to survive reentry at interplanetary speeds if the slingshot goes wrong. It's not like we don't have tonnes of vapourised plutonium in the atmosphere anyway, but that's no excuse for adding more. Plus, the kind of plutonium that goes into an RTG is fabulously expensive, not just because it doesn't occur in nature and has to be made via transmutation, but because it makes handling so much more complicated. They'll have done the cost-benefit analysis and decided it simply wasn't worth it. (Also, RTGs are big and heavy. New Horizons, which is a really small spacecraft, has a 50kg RTG. Philae only massed 21kg.)

imglorp 11y ago
There's probably plenty of human risk transporting it to the launcher, as well, such as a road accident or having it be stolen.
- ars 11y ago
  > such as a road accident No, not really. They are pretty safe - you can hold one in your hand without a problem (barring a burn - they get hot). A road accident would do nothing harmful at all. > having it be stolen That strikes me as pretty unlikely - they don't exactly drive on public roads.
  - saboot 11y ago
    We drive nuclear missiles on public roads, with enough security anything is doable.
    - eco 11y ago
      Yep. An example: https://www.youtube.com/watch?v=bCwlV_94kPE https://www.youtube.com/watch?v=bCwlV_94kPE

TrevorJ 11y ago

To be fair, there are real world safety considerations when putting radioactive material into orbit. It's not just a knee jerk reaction, in all likelihood. The risk for Cassini was calculated at 1:1400 (For context, humans have launched something like 8000 man made objects into orbit). That's certainly acceptable when there's no other reasonable way to provide the power that the mission profile requires, but it makes sense that they would go with a more conventional source where possible.

InclinedPlane 11y ago

ESA is multinational and some member countries are very opposed to nuclear technology in any form. Aside from the fact that Europe generally lacks the ability to manufacture Pu-238 or RTGs in general. Britain is looking at developing RTG technology on its own, possibly using Am-241, which might shake things up. It's still a hard problem with so many member countries involved.