An answer to a JPL document regarding CASSINI's nuclear payload

By Russell D. Hoffman

Copyright (c) 1997

I was directed to the document discussed and shown below by a letter I received from Earle K. Huckins III, whose title at NASA is Deputy Associate Administrator for Space Science. It was an answer to my letter to The White House dated February 24th, 1997. I received the response April 28th, 1997, a little more than two months after sending the original documents to Clinton. The response says at the very bottom "cc: The White House". It also says to "Reply to Attn of: S". I wonder who S is? A most peculiar name... Well, it's signed by Earle K. Huckins III so I'll respond directly to him and bypass the elusive "S". I'll "cc" "S" and The White House. (Here is a GIF image of Mr. Huckins' letter.)

Mr. Huckins' letter states:
" Thank you for your letter of February 24, 1997 to President Clinton concerning the Cassini mission to Saturn. Your letter was forwarded to me for a response.

The NASA Administrator has stated repeatedly that safety is the Agency's number one priority, and I must emphasize that NASA places the highest priority on assuring the safe use of radioactive materials in space. You can be assured that the Cassini program has complied and will continue to comply with the Agency's priority by keeping the risks of the mission small.

Additionally, all NASA planetary missions, including Cassini, are scientific and civilian, and the goal is to share the benefits and knowledge with the world. You can find updated information relating to Radioisotope Thermeolectric (sic) Generators (RTG's) safety for the Cassini mission by visiting the Jet Propulsion Laboratory web site at:

Mr. Huckins' letter concludes with a phone number, which I will thank him for, and which I just might try using some day, but generally I prefer letters. (I mention this just for the record. I prefer letters, among other reasons, for the record they leave.) (Actually, I would prefer encrypted, author-authenticated and message-verified email, but no one ever offers me that option, so the postal service will have to suffice.)

I visited the JPL web site listed in the letter. It has very little information actually, just a few paragraphs. It did, however, link to one article of any significance, which it claims is "a response to some of the more widely-distributed inaccurate reports."

And what is their response?

Actually, it's not a response to any of my allegations, and although Mr. Huckins III had said the information was "updated", the date given in the actual JPL document is November, 1996. In November, 1996 I didn't even know what RTG stood for, let alone how to spell Radioisotope Thermoelectric Generator. This NASA/JPL document does not respond directly to my allegations of February, 1997, let alone my more recent allegations about the RTGs.

What follows is the entire text of the NASA/JPL document, in italics, interspersed with my commentary. In some cases we feel we have already responded to the points made in the JPL article; in those cases a link to the appropriate article has been included.

There are 6 points which the JPL document attempts to respond to. Here are answers for each of the 6 points, plus a response to their introductory paragraph:

There are people who are making incorrect statements about NASA's Cassini mission to Saturn. Some of the statements are either misinterpretations or misrepresentations of NASA and European Space Agency (ESA) documents. The purpose of this fact sheet is to address some of the technically incorrect descriptions of potential launch and reentry accidents, and unsubstantiated health impact predictions.

This introductory statement needs a comment. It represents bad government policy in general. I do not like NASA/JPL claiming that "There are people who are making incorrect statements". NASA should be willing to name those people and quote them accurately. Each of NASA's 6 "false" statements which follow are in fact, either over-simplifications or crude mis-interpretations of opposition beliefs and fears.

I would like NASA to link to my opposition articles. At the very least, NASA should build a web page of opposition sites so that we are legitimately represented and so that NASA p.r. isn't the public's only source for the 'full' story.

It would benefit NASA to do this, really, because it would show the public that they are open about the issues.

The issues involved are generally gray-scale issues. It is not a question, as NASA wants to boil it down to, of simply asking NASA to tell us if the mission is safe. For NASA to claim, as Mr. Huckins does in his letter, that safety is "the Agency's number one priority" is a hollow claim and they know it.


Because total safety would be to not fly the mission. This extreme alternative is always balanced with all the other factors, including cost, alternative technologies, and it can even be influenced by public opposition and public support. And of course, it is balanced against scientific benefit. Risk versus benefit. That's the name of the game. So the #1 priority (safety) gets overruled all the time, every day, in every situation. When you cross the street, you overrule it on a personal level. It is safer not to cross the street at all, but you want to get around. Even Chicken Little would cross the road once in a while!

NASA presents us with the Space Agency equivalent of the number 42, which in this case represents the entire analysis of the mission. (42=SAFE TO FLY. The number 42 was chosen here simply for it's deep philosophical significance. Any number would do.) It's not a yes-no question, nor a false-true question, nor can it be boiled down to such a simplistic scenario. What NASA should be doing is presenting the facts and letting us draw our own conclusions. Instead they present their conclusions as if those conclusions were the facts. The facts are deeper, and there are many statistical graphics packages which NASA should be using to present those facts to the public.

NASA hides the real facts and the real math inside complex verbal descriptions, tables of exponential numbers, and inappropriate calculations. This is NASA's biggest problem: Bad science is being used to bolster the few weak real arguments NASA has to justify pursuing the nuclear option. In fact, the nuclear option is a dead end.

We should not ask "Is the mission safe?" but rather: "Is the mission too dangerous?" "Are the risks too great?" There is no way that the mission can be made entirely risk-free. So the American public needs the full story. (The world deserves it too, since the environmental impact can certainly be global or even be entirely on foreign soil.) What we DON'T need is an analyzed, condensed, summary execution of the data. Present the data, NASA. Let the public draw their own conclusions. I think NASA is (rightfully) afraid of what the results will be if all the facts are presented to the American public.

Here are the six points in the NASA/JPL document together with my commentary about them:


The Cassini mission could use solar power instead of RTGs.



NASA is talking out of both sides of its mouth here. NASA used RTGs 'safely' even on space missions to explore the sun's own polar regions! (Ulysses.) NASA could have completely embraced the solar option and not dropped hundreds of millions of dollars over the decades on the awful nuclear option, but NASA chose not to. Why?

Not only has it been a waste of money, but NASA's "three decades of safety" are in fact nonexistent. RTGs have been present in a number of very serious accidents. Although RTG's themselves probably do indeed reliably produce electricity (so would solar), their mere presence makes them a danger.

One accident, Apollo 13, NASA actually uses to indicate the safety of the RTGs. In fact the results of jettisoning the lunar lander and it's RTG is completely unknown. A significant portion could have been incinerated and we would never know. NASA makes unsubstantiated claims and then uses those claims as though they were facts.

The thing about Saturn that fascinates everybody, and has for centuries I might add, is the rings. And the only way to properly study those rings is to do a time-lapse analysis of their behavior over a long period of time.

Therefore, the proper mission to Saturn is one that will photograph and analyze the rings up close, year after year, for perhaps 100 years or more, and send the images and data back to us. Saturn has rings. Ask anyone. That's usually just about all they know about Saturn. What the public wants to know, then, is where did they come from, and how are they evolving? Since NASA and other space 'buccaneers' have created billions of pieces of space debris around Earth in little more than three decades (debris which NASA is continuously studying) we have yet another reason to be very interested in the evolution of the natural space debris -- the rings -- around Saturn.

Cassini will not answer these questions. Instead it will be there only a short while, make a rushed analysis, take some quick pictures and be done with it. The solar option NASA ignores could have provided continuous power until the sun burns out -- or at least long enough for a much more careful analysis of the neatest part of Saturn.

By not using the dangerous nuclear option, NASA could have taken other risks that might have allowed them to actually fly a larger mission. For example NASA says that they set the height of the flyby above Earth (310 miles) as a safety feature considering the consequences of a flyby re-entry. Had they not used plutonium, perhaps they then could have risked doing the Earth flyby at 250 miles instead. That extra 60 miles (still outside of at least 99.999% of Earth's atmosphere) would give them additional gravity assist, which could in turn have allowed a greater payload to be sent to Saturn. Also, they would not need to have used the bias operation for safety, so the fuel brought on board specifically for that part of the mission could have been left behind and additional solar panels brought instead. Furthermore all the solar panels NASA suggests as substitutes are poorly designed as if to bolster NASA objections. (See picture.)

Five percent here, five percent there, and pretty soon NASA's got its whole mission back, and more. If they play it reasonably safe (and honest), we'll give them all the money in the world (or at least a good chunk of change).

Using the solar option could have benefitted NASA in many ways. It would take the 'solar' wind out of my sails, that's for sure!

Karl Grossman worked very hard to get the NASA documents that indicate quite clearly that the solar option would have allowed NASA to complete most, if not all (but probably all) of the current mission objectives. He got them.


The Titan IV rocket that Cassini will be launched on has been involved in many accidents.



As anyone can see, 18 out of 19 is more than a 5% failure rate. That is real data, not estimates. NASA has been in existence for over 30 years. NASA has had failures in virtually every type of mission. Often, NASA failure rates are in the double-digits. It is time to stop believing NASA estimates and start going on actual NASA performance data.

The point NASA makes here shows the simplistic thinking behind NASA's decisions. Because they feel they have fixed the problem (what were they expected to do -- leave it alone?) NASA now feels that this failure should be completely discounted from your mind -- the one failure becomes none, for a (virtually) infinite success rate. But with the Titan IV rocket launcher, as with most, if not all, of NASA endeavors, actual demonstrated abilities fall short of NASA predictions. After more than three decades, NASA should be required to consider it's own past performance when indicating future rates of success. The Titan IV is not a reliable launch vehicle, and the Centaur booster is even less reliable.

NASA should understand that we expect mistakes and we can forgive them. Admitting that NASA can fail doesn't mean we would want to shut NASA down. It just means we want to make them behave in a way that would mitigate the risks when failures occur, which they inevitably will do. NASA should stop trying to convince the public that NASA can do super-human things just because "they're rocket scientists".

I would like NASA to present to the public a list of the 50 most catastrophic failures they have had. Starting with Challenger's malfunction, then the Apollo training fire, then the Apollo 13 moon shot failure, etc.. Match each failure with NASA's own estimates of the likelihood of that failure prior to the accident. Then let the public decide how much faith it should have in NASA's numbers. I know the numbers for the #1 accident. The chance of a catastrophic accident involving a space shuttle was pegged at 1 in 100,000 before Challenger blew up. For ten years after it was placed at about 1 in 78. Now it's gone up a little to a nice even 1 in 500. Jumpy little things, those NASA numbers...

NASA has done what any well-funded (and they have been well-funded!) group of scientists would do -- they have explored their field. The money which has gone into NASA's idea of space exploration, had it gone into exploring new energy efficient architectural structures for example, or deep-sea trench exploration for another example, would have also brought out fascinating and wondrous new technologies and products. Not all smart scientists work for NASA. A non-nuclear Cassini mission would also have brought out wondrous new technology, but at considerably less risk.

Note that even a 100% success rate with the 19 Titan IV's launched so far would not prove NASA's reliability. For the reliability needed to risk launching 72 pounds of Pu-238 into space, NASA would have had to have successfully launched many 100's of non-nuclear missions first, with a 100% success rate. NASA's true record, across 100's of launches of dozens of types and sub-types is, in a word, dismal.

Finally, even NASA's own Cassini people are scared of these Titan rockets. The Cassini launch will be only the second launch for the Titan IV's new Solid Rocket Motor Upgrade. Here is a quote from NASA's own manager of instrumentation and payload for the project, as quoted in Design News, April 7th, 1997 (page 22): "Second is fine... We absolutely do not want to be first".

One launch of these new SRM upgrades is enough to satisfy this official. He is willing to send 72 pounds of the world's most deadly substance into deadly orbit upon a once-tested new SRM design, but he absolutely does not want to be first.

This is not a man we should be willing to follow into harm's way.


When RTGs are exposed to environments similar to the Challenger accident they could fall to ground and release all of their plutonium dioxide which would then be taken up into the air and then "rain down" on people in populated areas.



NASA is confusing what people are really afraid of. In an accident similar to a "Challenger accident" I don't think many people are worried that the pieces will fall to the ground, then somehow evaporate, and then be blown around the environment. Certainly pieces that are not recovered will (by definition) be released to the environment where they will be able to do some amount of damage. Some will almost certainly be incinerated and we are talking about a substance that is so deadly, a millionth of a gram is considered a carcinogenic dose. So it won't take much to make a major mess in Florida, Africa, or Madagascar, and that's just in the first few minutes of flight.

What we really fear during the launch phase is that the RTG's, when exposed to an explosion of great magnitude should the Titan and/or Centaur booster rockets blow up, will actually incinerate at least somewhat as the accident occurs, at great height above the earth. NOT that the RTGs will fall to Earth, and THEN vaporize on impact. (I suppose that could happen a little, but probably not to any great extent.) We also fear a forced-impact where the rocket drives itself into the ground due to a navigational malfunction combined with an engine shut-down malfunction or a rocket self-destruct malfunction. In such a scenario, yes, a lot of RTG plutonium dioxide could be vaporized close to the ground, where it could (and would) be carried into the ecosystem.

The RTGs are normally at about 2500 degrees F. and they melt below 4500 degrees F. Temperatures of this magnitude and greater would definitely be expected in an explosion, and NASA real-world data showing the RTGs are safe in a launch explosion consists of exactly one explosion (the above-mentioned Titan IV explosion). I for one am not comforted by NASA assertions based on this one event. It was not a forced-impact event. It was not a high-speed (relatively) upper-atmosphere explosion. And it was not over a populated area. NASA got lucky. The explosion occurred over the Pacific ocean and they were able to retrieve the RTG. NASA won't be lucky every time.

I must note that NASA's statement: "The potential hazard would arise from inhaling very fine particles of the plutonium dioxide" is good to see. At least here, they have admitted this fact. Now, let's see them apply this truth to the mathematics of a Cassini flyby accident.


Many people would die if there were a plutonium release from Cassini RTGs involved in a launch accident.



First: NASA continues to try to keep focus on the launch and tries to pretend that the actual consequences of a flyby accident need not be discussed, because from NASA's point of view, it is so unlikely to happen as to not require proper analysis. NASA cannot back up this view with substantial evidence, just a couple of previous flybys. A couple of previous flybys does not make a reliable track record.

I'm sure it is true that the launch is the most likely part to fail. But the severity of an accidental flyby re-entry is much, much greater. So take your pick: More severe problems with less likelihood of occurrence (the flyby) or less (but still severe) problems with a greater likelihood of occurrence (the launch phase). It's a gray-scale matter. The original statement, "Many people would die if there were a plutonium release from Cassini RTGs involved in a launch accident" is probably false. Change "would" to "could" and the statement is entirely correct.

Second: The very first part of the launch (in Florida) is much safer, from the point of view of what the RTG's might do, than the portion of the launch which occurs over Africa a few minutes later and then over Madagascar. So one blanket statement covers just way too much ground.

Third: Despite NASA denials, scientists have repeatedly shown that low levels of radiation are dangerous. Adding more radiation to existing levels of (now manmade and background) radiation is not good. The mathematics of NASA's analysis of the effects of an accident are absolutely totally improperly done as we have pointed out extensively in our (36-point draft-) Answer to NASA's Draft Supplemental Environmental Impact Statement.


A single spacecraft failure or small misfire of the Cassini engines would result in an Earth reentry accident.


The probability of an inadvertent earth reentry is extremely unlikely -- less than one in 1 million -- even in the event of a spacecraft failure or misfire of Cassini's engines.


The peculiar design of the RTGs (explored in another article) makes this writer wonder just how safe we really are and how much NASA really trusts its own predictions.

While the space probe is flying towards Earth at approximately 43,000 MPH (it will be the fastest manmade object ever to 'buzz' the Earth) the RTGs will be sitting near the back of the probe, at 120 degree angles to each other, behind the liquid fuel and liquid oxygen tanks (behind, relative to Earth and relative to the direction of travel, which is just a fraction of a degree away from being directly towards Earth.)

An accident which causes an explosion of the liquid (nonradioactive) propellent (a natural micrometeoroid or a piece of man-made space debris could do this) would blast the three RTGs backwards, slowing them down perhaps by as much as a few thousand miles per hour. This would make them more likely to be captured by Earth's gravity.

Also, because of the bias of the trajectory which NASA claims is a safety feature, an accidental extended firing of the Cassini propulsion system can have catastrophic results. The bias trajectory means that NASA must, in a series of serious maneuvers, repeatedly re-aim the probe closer and closer to Earth. The first time NASA does this the probe will be 10,000,000 miles from Earth and the so-called 'bias' will be mere fractions of a degree. Each time NASA does a bias-correction maneuver, even a slight extended firing can have disastrous results. Severe failures happen. The Titanic and Challenger both experienced severe failures. Everyone thought the Titanic was virtually unsinkable, and a shuttle accident was, in NASA's mind, virtually unthinkable. In the case of Cassini, it would not be any big deal if NASA had not chosen the nuclear option. We would just lose one probe. Not potentially a whole city, any city.

The most dangerous single part of the flyby is the part where the probe is closest to earth (within about 25,000 miles of Earth) but it has still not yet reached us. At that point, it will be at the mercy of our own man-made space debris. Space debris encircles Earth because of past haphazard activities of previous space explorers. Everything from old lens caps and gloves to used rocket motors to frozen urine discarded during previous space leaks circles the Earth at speeds averaging 22,000 MPH. Because of the tremendous speed these objects travel at (most are not tracked and are on unknown trajectories) even a small object the size of a pea could burst Cassini's liquid fuel tanks, causing an explosion. That's one event, NASA, that can ruin your day and number many of ours.

If a collision occurred which causes an explosion of the liquid fuel during that Near Earth portion of the flyby, at least one of the three RTGs will almost surely be flung towards Earth. And that is the most likely time for an collision. Furthermore, there would be at most only about half an hour of warning of an accident, and probably only minutes or seconds. And even the general point of impact with Earth would be nearly impossible to predict.


Dr. Ernest Sternglass claims that NASA and DOE have underestimated the potential number of cancer fatalities from a hypothetical Cassini swingby accident.



In April, 1997 I interviewed Dr. Sternglass because someone had shown me the last paragraph of this NASA document.

Dr. Sternglass and others have provided numerous scientific studies showing what the effects of upper-atmosphere incineration of radioactive particles can be. NASA chooses to ignore these studies.

Dr. Sternglass should be no more required to prove once again what the radiological consequences would be for a particular mission (in this case Cassini) than Einstein should be required to come back and prove how each nuclear bomb would function, or than Newton should be asked to prove again why the apple falls from the tree (but not far from the tree). (Actually, come to think of it, maybe NASA could use a lesson in... oh, skip it...)

The data is in, the surveys are done, and NASA consistently ignores them. Dr. Sternglass does not need to explore Cassini in particular to know that NASA has not used his scientifically valid findings. Nor does Dr. Gofman. Nor does Dr. Gould. Nor does Dr. Caldicott. Nor does Dr. Morgan. NASA science is science based on false assumptions, dangerous assumptions, and deadly deceptions.

For more information on the Cassini mission and its nuclear safety, contact Cassini Program Public Information Representative Mary Beth Murrill (818) 354-6478. Internet:
Last Updated : November 1996


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