Hi!
Thanks again for your engaging and challenging emails. If you recall, a few days ago I had sent you a partial response to your second email. As I said in that letter I would work on a more complete response, and I have, and here it is. I have excerpted your letter to answer various parts; your entire previous second email to me appears [here, with the rest of our previous correspondence].
I must start by stating "for the record": I'm not an engineer, nor a doctor, nor a reporter, nor of course a rocket scientist. I am just a concerned citizen.
Still, I think NASA "owes me" explanations that make sense. I have spent my working life talking to brilliant people and writing educational tutorials based on what these people say and write. NASA is not behaving like those hundreds of helpful people I've met in my career. Others who have watched this particular conflict between NASA and I have noticed this. NASA could have sent me a box of data with numerous charts and graphs and details. That's what I get from countless industry and other government agencies when I inquire about something technical for whatever reason. NASA could even invite me to a wind-tunnel test if they dared, couldn't they? Or send me a video of one. They know exactly what proof I need to see.
Instead I get a half-page letter sending me to a web site that is totally basic. I don't think an engineer at NASA even saw my documentation or my inquiries. Instead it appears that it was passed directly to someone in the PR department. Usually, my inquiries go the other way! I am quickly passed from the PR person to the engineer. I challenge NASA to show me the proof about the RTGs. Instead you ask me to start from scratch. Sir, I do not think that is fair.
You ask me to "crack open [my] thermodynamics textbook and do the math" but I don't think NASA has provided the data I would need, so it would do no good.
For example, you say that since ICBM's 'survive' re-entry, shouldn't the RTGs?
You wrote:
The plutonium is in the form of a ceramic, with a melting
point of 4,442F, encased in a cladding of pure iridium metal
with a melting point of 4,861F, encased in graphitic material
as is used in ICBM nosecones, with a considerably higher
melting point than either of the other two.
Unless you memorize four digit numbers, I can see you got out some books. But I think before getting out the books would do any good, I have to ask several things:
First:
Those ICBM's are pretty secret stuff. How do I know that the way they survive re-entry is not by melting off the outer few hundred pounds of whatever kind of special super-secret metal they are made of? If so, that would actually indicate that the RTG's could melt away too. But that's not as important as this point:
Second:
My understanding is that the temperatures an ICBM survives on re-entry are in the neighborhood of 14,000F, well above the 4442F and 4861F temperatures you talk about. The plutonium cores in the GPHS modules are at 1100C. The outermost part, the "outer shell of the RTG" is at 270C when heated by the plutonium dioxide within. When additionally heated and burned off by the heat of re-entry, the 1100C cores will soon be exposed, I fear. See page 3-5 of the Nuclear Safety Analyses for Cassini Mission Environmental Impact Statement Process (April 1997) and your email below for the source of the above numbers. For the "14,000F" number, I have a book published and compiled by the Editors of Air Force Magazine called Space Weapons. Copyright 1959. Old news, but I doubt the potential temperatures of ICBM's on re-entry has changed much. But that's not as important as the next item:
Third:
The ICBM you mention re-enters Earth's atmosphere at about 1/3rd the speed of Cassini during the flyby. Temperatures will be very significantly hotter for Cassini.
Fourth:
The exact properties of the RTGs are impossible to determine from the available drawings, although I find it hard to believe that you are actually asking me to compare the aerodynamic nose cone of an ICBM to the vaned contraptions that surround the RTGs.
When the outside's hotter than the inside (as will be the case if a re-entry occurs) the vanes will do basically the opposite of what they do when the temperature gradient's the other way around, won't they? Won't they permit heat to enter, having been designed to permit heat to escape when the temperature gradient's is the other way around? Not to mention, I expect them to be ripped and burned and melted off, leaving gaping holes for heat to enter--to enter to a core that's already at 1100C. As vanes they will channel and eddy the heat so that again, gaping holes can form. Not like a nose cone at all which is designed specifically to spread the heat out evenly along the surface.
Fifth:
Even with all that knowledge, the actual calculations would require hundreds of thousands or even millions of dollars and hundreds of hours (or more) on super-computers. It would produce real data. Data NASA in theory already has but HAS NOT PRODUCED. Why am I being asked to duplicate this effort?
So far, NASA has merely summarized it as having passed their tests... Actually, they didn't even do that. My reading of page 2-19 of the "FINAL EIS ON THE CASSINI MISSION" (June, 1995) is that it failed explosion testing, fire testing, and fragmentation testing. Conditions in all three areas can easily exceed the tested points of failure.
Sixth:
I'm a computer programmer by trade. I write educational tutorials. I have dabbled in many fields and feel I can understand reasonably complex things that are presented to me. But here are five other reasons not to bother opening a thermodynamics book just yet. If each of them were answerable, then perhaps it would be time to open the books. I don't believe those RTGs will survive a re-entry, and in any event, there is no way NASA (or you) should be asking me to do the study. NASA has already done the study, has computer-generated videos, etc. All they have given us is a summary claim of what the data showed them, in their minds. Have you asked for NASA for this information so that you can explain it to me? I would not mind. I will apologize when and if (and where) I am shown to be wrong.
Your other main point was of course concerning the damaging effects of low levels of radiation.
Let me first state how absurd I find this, to be arguing that the RTG's are designed to fail, with people who claim that they are not, who also are the same people who claim that such failure would be the safest way to design the things, the most humane, the best way in the interests of the United States' financial balance book for sure -- do you deny any of these things?
If you had it to do, would you design the RTGs to incinerate or would you not?
Because if they partially incinerate on the way back to earth, then truly, that can have the horrendous IMMEDIATE AND OBVIOUS health effects many would call a "WORST CASE SCENARIO". A streaming, partial incineration will leave a plume no one can like. And by the way, NASA officially predicts just such a partial incineration if a re-entry occurs, usually anywhere from 1% to 30% of the RTGs, but virtually never 0% or 100%. A partial incineration is particularly scary from the point of view of financial liability and immediate effect.
If as NASA contends, low level radiation is really such a minor problem, then a complete upper atmosphere incineration on the other hand would mean virtually no one gets hurt. And certainly the financial burdens of a failure will disappear if the Pu 238 incinerates in the upper atmosphere. So why not build them that way on purpose?
Because it's wrong. Humanity STOPPED atmospheric testing of nuclear weapons precisely because it was unhealthy. A Cassini re-entry incineration would be a catastrophe. So comparing 72 pounds of Pu 238 dioxide, which is 280 times more radioactive when inhaled, to the "11,000 pounds" of mostly far lower grade plutonium, I see as absurd. Just because mankind has poisoned the planet terribly does not mean that mankind should continue to do so. Besides, this one accident, if it's a complete incineration, would put the "radioactive equivalent" of 20,000 pounds of a less radioactive grade of plutonium into the atmosphere at once! Nearly double the effect of your "11,000 pounds" from atmospheric testing. How many millions died and will die from the atmospheric testing?
You wrote:
...11,000 pounds of plutonium, plus heaven knows how many
tons of a wide spectrum of other radioactive elements from
neutron-activiated bomb parts, dirt, water-borne minerals,
and the like, weren't enough to kill everyone on Earth
11,000 times over, as is obviously the case...
You, of course, do not see the white flags on the graves that say "This person died from atmospheric testing, circa 1950" or "that person died from NASA's SNAP-9A, 1964". But I contend, and others -- real scientists -- contend that they are there. By the millions. And I must add that our horrific failure to see far less subtle trends makes it quite reasonable that we might miss the effects of something like this.
For example, look how long it took to even figure out the cigarettes were dangerous! A few tobacco executives still do not believe it, but even they are coming around... You ask me to prove a far more subtle killer. Scientists have shown time and again, a multitude of mechanisms by which the killing and other destruction can work. (It's not just about killing. It's also about breast cancer, infant and fetal illnesses and deformities, and genetic damage, not just to humans but to other living things as well.)
But the scientist's theorems and explanations of the mechanisms are not enough for you, you want some kind of statistical proof. Does NASA want such proof as well? Then they should go and get it: Read Dr. Sternglass's books, and Dr. Gofman's, and Dr. Gould's and Dr. Caldicott's and Dr. Morgan's and on and on and on. As far as I can see, there is scientific literature and scientists to back up my point of view. There have been countless concerted conscious efforts (and now, with information recently declassified, conspicuous efforts at that) over the years to thwart such research, starting with the Army keeping double books about real and reported soldier exposures during bomb testing. No. Before that. Starting with estimates of acute radiation damage PRIOR to Hiroshima and Nagasaki. ("NONE." The official estimate prior to dropping the bombs was that everyone who might otherwise die of acute radiation sickness would be dead by being hit with a brick or something first.)
On another issue, that of comparing Cassini to coal-fired plants, you use the classic pro-nuke argument that I have heard so many times and that to me makes no sense at all.
You wrote:
What about the tons upon tons of radioactive uranium and
thorium that's released by coal-burning power plants?
Surely that poses a far more serious, immediate health
threat than a spacecraft that would have to fail six ways
from Sunday to crash into Earth.
I disagree, of course, with the "six ways from Sunday" portion, but that I have gone into repeatedly at the web site. I personally do not trust NASA's estimate of the unlikelihood of an accident being anywhere near one in one million.
However, your point about comparing Cassini's 'threat' to the daily damage of coal-burning power plants to me just shows you have a very limited argument at best, or even one which dooms you and your side to philosophical failure. The very act of trying to use coal as the comparison is a poor choice, I think. It's the pot calling the kettle black.
Nuclear advocates have always used coal-fired power plants as their whipping boy. Always, a properly operating nuclear plant is shown to be clean compared to a properly operating coal plant. But one has to recognize that a major accident at a coal plant is a rather minor event in the scheme of things, while a Chernobyl-type accident is not. And, the as-yet-unexperienced process of decommissioning the plant and then storing the waste for a quarter million years has also not been included in the comparison.
I do not find value in arguing such a comparison. I do not believe one anti-nuker, or one environmentalist, supports coal OR nuclear power. Compare it to something more benign, and ask me to choose. You have chosen perhaps the worst environmental calamity in the universe -- the burning of millions of tons of coal -- and used it to seek permission for NASA to do something else just because it may be somewhat less damaging than all the coal that's being burned. Actually, I think the return-on-investment from those coal firing plants has been significantly higher than the scientific returns expected from a 100% successful Cassini mission. People have heat. People have light. People have electricity to run other more benign scientific experiments with.
Energy drives the world, it always will, and there are good reasons to risk damage to the environment to produce energy to supply the needs of an existing or anticipated populace. Not that coal OR nuclear can justify themselves, they cannot, but they can more so I think than Cassini can. As a species, we must choose our energy sources wisely and we have not done that. Coal pollutes too much. Nuclear pollutes too much. And oil? Oil has far too many uses to simply burn it! Renewables are the only reasonable choice. Don't compare to coal.
A pound of science can be cut from many sacred cows. We do not know enough about deep blue seas. We do not know enough about renewable energy. We certainly hardly know a thing about how our own brains work, or how they will function when 95% of the world is on the Internet, instead of the other way around. Etc. etc.. I do not believe, despite your fine and challenging letter, that we need to risk the use of nuclear payloads in space, on this or on other missions. The potential science benefit does not justify the health risk.
Other comments you made and some answers:
You wrote:
...the activity is in the form of alpha radiation, which can
be stopped by a sheet of paper. All radioactivity is not
created equal, and your comparing alpha radiation from plutonium
ceramic, in the off chance that Cassini fails in just such
a way that it might be released, with the veritable menagerie
of radioactive isotopes from Chernobyl, just smacks of
emotional fear-mongering.
As you say all radioactivity is not created equal, and this particular plutonium's alpha radiation is most dangerous when a fine particle is inhaled, although it can also damage the alimentary system if ingested, causing colon cancers and other alimentary ailments. Fine particles of plutonium dioxide usually pass through the system after some period of time when ingested. Many cultures burn dung and even human feces for energy, allowing previously ingested particles to become inhaled particles their next time around. When inhaled, they usually lodge permanently in the lung. Until the person dies for whatever reason. Then, perhaps they are cremated. And so that one little plutonium particle goes 'round and 'round again... The average plutonium dioxide molecule will last for more than 87 years... After 500 years, out of 72 pounds of Pu 238, there will still be more than a pound of "the deadliest substance known to man" on Earth. Even after a thousand years, there will be enough to kill off whole countries, "when properly distributed". Randomly throughout the environment and the food chain is one "proper" method of distribution.
My understanding is that if Chernobyl released 72 pounds of Pu-238 into the atmosphere (which it could not actually do, but just for arguments's sake--) it would have been a significant portion of the overall health hazard. Emotional fear-mongering? Absolutely. I'm scared.
You wrote:
I suggest, then, that you and your cohorts fighting the
Cassini mission stop using the specious assertion that
one pound of plutonium is enough to kill everyone on Earth.
If you are actually interested in generating light, instead
of heat, I expect that this would make sense to you.
You are right that that argument is shrouded in misinformation. I have, in fact, argued quite extensively with friends on the exact wording of various versions of this statement, lest it's underlying premise be misrepresented by a single word change somewhere.
The exact nature of the underlying statement is that if you were to divide a pound of plutonium into some 5.8 billion particles, and then placed one of those particles on a person's lung tissue, that person will surely develop lung cancer, without question. It's that deadly. So the only thing "saving us" from such a death is the fact that many of the particles will NOT be inhaled if a flyby re-entry accident occurs.
That the 10s or 100s of billions of particles from 72 pounds of plutonium will instead nearly all make it to earth and NOT be ingested by other animals and then transferred into our bodies, will NOT land on the ocean and then be readmitted to the atmosphere (as has been shown to happen) through evaporation... Will NOT become part of the food chain (it looks like iron to most biological systems, which they need, but it isn't)... There are 5.8 billion people on this earth. That is far too many to risk giving them each a chance at ingesting or inhaling a plutonium particle.
Furthermore, for every living human there are 100,000 or even a million other living animals (or thereabouts). Plutonium is undoubtedly a hazard to them too. And sometime next century there will be a different 5 or 10 billion people on the planet, and they will still have this plutonium in the environment. Even NASA admits it can take decades for this stuff to fall to Earth -- the first time.
Thank you, again, for your email. Although I cannot entirely say I have enjoyed the exercise of responding, I can say that I believe it has done me good and I appreciate your efforts and your challenges, and, after my #1 hope that I have actually swayed you, my #2 hope is that at least you do not feel I have wasted your time. I will be interested to read any response, either of which of us might of course freely publish. I will presumably include any additional response you offer in anything I might publish...
If you would like to include your affiliation or a brief c.v. of some sort, I would be curious and I'm sure others would appreciate it as well.
Sincerely,
Russell D. Hoffman
rhoffman@animatedsoftware.com