The Death of Cassini

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There’s a beautiful article by Paul Greenberg on the death of Cassini, the Saturn explorer–I can’t add much to it, other than these few thoughts on AI (artificial intelligence).   Despite the intelligent and benevolent (sometimes) robots and androids of science fiction (Asimov’s, HAL 9000, etc.), no artificial intelligence could have written that self-obituary.   It is man who celebrates Psalm 19A, “The Heavens declare the glory of God” and only man.


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  1. As a 40+ year nuclear energy professional, I will add that Pu-238 is a wonderful thing. Without an RTG, Casini could not have done half of what it did or lasted nearly as long. Sadly I am too old to see the day when we will use these for trips to Saturn and beyond:

    A few years after Nixon killed this program I qualified as a submarine reactor operator. I hoped in vain the program might be restarted under Reagan (Carter was and remains a lost cause).

  2. Lucius, we’re going to need fusion before we start doing anything serious with manned missions to other parts of the solar system. That’s a problem for the next century.

  3. Howard, I am not a fan of fusion, and I have many times explained the following here at TAC, so I may sound like a broken record.

    Since I was a little boy in the 1960s I have been told that fusion is 20 years way. It is now 2017 and still 20 years away. The International Thermonuclear Reactor (ITER) project in France is a boondoggle that may not even acheive breakeven output. It takes more energy to force postively charged nuclei like deuterium and tritium together against their mutual repulsion (like charges repel) to cause fusion than can be obtained from the process. Fusion works great in the sun because gravity forces the light element nuclei together. Fusion works explosively in thermonuclear nuclear weapons because a fission explosion of heavy metal atoms like Pu-239 or U-235 compress the light nuclei together. But controlled fusion (e.g., using magnetic confinement / compression or laser / particle beam implosion) is very difficult and requires more energy in than obtained in energy out.

    But fission of heavy metal atoms like Pu-239 and U-235 and U-233 is easy. A neutrally charged thermal neutron isn’t repulsed by the positively charged nucleus of the heavy metal atom (because it’s neutral!), and when it hits a nucleus it easily causes fission, generating 2 to 3 extra neutrons per fission to continue the process in a self-sustaining way in other heavy metal atoms.

    So fusion is absurdly difficult and fission is ridiculously easy. Furthermore, with thermal nuclear rockets like NERVA we could easily travel the solar system, and we have plenty of thorium-232 in Earth’s crust that we can breed into fissionable U-233 as fuel. We have no lack of resources to do this.

    But we lack political willingness. Fear – nuclear, radiation, we’re all a’gonna die – prevents this. Stupid, unreasoning, irrational fear. I have worked in nuclear energy for 40+ years. I have been within yards of an operating reactor in a sealed nuclear submarine hundreds of feet below the ocean’s surface. I have stood above the spent fuel pool at both pressurized and boiling water reactors. I still live, breathe, eat, drink, pee and poop.

    Nuclear fission is the way to go. Read more here about why fusion is difficult and fission easy.

    PS, the old canard – spent fuel is toxic for millions of years – is easily dealt with, and we need no stinkin’ Yucca Mountain spent fuel repository. Simply reprocess used fuel for use in fast neutron burner reactors like GE-Hitachi’s PRISM. All that’s left over is ash that decays away in mere hundreds of years (unlike coal ash toxins which never ever decay away, and whose release into the environment exceeds by orders of magnitude anything released from a nuke). And if we don’t want to use a sodium cooled reactor like PRISM, then build heavy water CANDUs from Canada – they can take our spent fuel in the US and with minimal reprocessing consume it in the fuel channel tubes of their calandria.

    We could easily go to Mars and beyond with existing technology. The reason we don’t is FEAR by ignorant people and GREED by fossil fuel.

  4. A small footnote. Before Cassini was launched NASA planned to attach a CD-ROM to the spacecraft with the digitized signatures of schoolchildren. So I scanned my elementary school aged daughter’s signature and emailed it off to NASA (What good is this internet? My wife asked at the time).

    Last month I broke the news to my daughter, now the mother of an elementary school aged daughter herself, that her signature was not going to survive as long as we had thought. I made sure to do this while we were looking at Saturn in the evening sky. She really laughed, mainly because she had forgotten about it over the cares of the intervening years.

    I recall being that age and my amazement that Ranger 9 could hit the Moon.

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