Leaving Earth cover

In 2019 I obtained from my former publisher the last 30 copies of the now out-of-print hardback of Leaving Earth. I sold about half of these, and with only a handful left in stock I have raised the price. To get your own autographed copy of this rare collector's item please send a $75 check (includes $5 shipping) payable to Robert Zimmerman to

Behind The Black, c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

I will likely raise the price again when only ten books are left, so buy them now at this price while you still can!

Also available as an inexpensive ebook!

Leaving Earth: Space Stations, Rival Superpowers, and the Quest for Interplanetary Travel, can be purchased as an ebook everywhere for only $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from my ebook publisher, ebookit.


Winner of the 2003 Eugene M. Emme Award of the American Astronautical Society.

"Leaving Earth is one of the best and certainly the most comprehensive summary of our drive into space that I have ever read. It will be invaluable to future scholars because it will tell them how the next chapter of human history opened." -- Arthur C. Clarke

Images of North Korea’s rocket and nuclear bomb?

North Korea's nuclear bomb?

Does this make you feel safer? The North Korean state-run news agency today claimed that they can now build a nuclear bomb small enough to fit on their ballistic missiles.

The story includes pictures. In addition, John Batchelor sent me a few more, including the one posted above. It supposedly shows Kim Jong Un, the supreme dictator of North Korea, inspecting a miniaturized warhead. Whether that is a real bomb or not cannot be confirmed. I would be curious hearing what some of my engineering readers think of this image and the bomb that he is admiring.

Below shows Kim Jong Un inspecting two rockets. Once again, I wonder how real this is, or is it a Potemkin Village.

North Korea's rockets?

Pioneer cover

From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.

Unfortunately, that is exactly where that journey takes him.

The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.

He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.

Available everywhere for $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from the ebook publisher, ebookit.


  • Wayne

    Holy Cow!

    Not an engineer, but the A.Q. Kahn network allegedly sold all their bomb designs to N. Korea. Does anyone know how small the Pakistani’s were able to engineer their weapons?

    Unfortunately this little troll has been able to detonate a bomb in the past, so even if this one is a bluff, it’s a damn good PR move on his part.
    (I’m sure John Kerry will have the UN issue a strongly worded letter to the little munchkin.)

    I knew this year was gong to be dangerous. Obama has succeeded in destabilizing practically the entire World.

  • Steve

    Camouflage rockets? That’s just bizarre.

  • Wayne

    Steve– If they are intended for mobile transport, it’s not necessarily bizarre. (as I understand it) This little troll is, as well, obsessed with all-things-military.

    We are living in dangerous times, eh?

  • mkent

    Why does the term “Sorcerer’s Apprentice” come to mind?

  • Frank

    Whatever they are doing, its in a very cold government cheese warehouse. Dear Leader has his best dictator jacket on and his hands in his pockets.

  • Tom Billings

    A few things indicate, unfortunately, that this is not a fake missile. At minimum, we can see that there is a set of vernier rockets to move the warhead away from the final stage, to prevent shunting, and probably give a velocity tweak to improve accuracy without depending on the main engines. If their electronics and software are up to it, they probably can do that. I have not seen any pic this close of Iranian missiles, so I don’t know if this sort of design has been sold to them.

    The lenses on the implosion sphere are a bit beyond me. Still, there seems to be a pathway open for a D/T boost injection of their primary.

  • wodun

    At least we have been united in our diligent efforts to create an effective missile defense system…

  • Dick Eagleson

    Missiles might be Scud-derived Rodong-1’s, but I see no tail fins and the nose is appreciably different so they might be some other roughly equal-size missile entirely.

    Or they could be mockups.

    The bomb looks like a small implosion lens-based plutonium device that allows, as Mr. Billings already noted, for “booster fuel” to be inserted into its center to enhance neutron production and increase the yield of what is still basically a fission weapon. The concensus seems to be that it was a device like this that North Korea most recently tested and claimed to be an H-bomb. It’s a bomb with “H” in it, but not an H-bomb.

    Or it could just be a non-functional exercise in pretty machining. It looks plausible as a missile-deliverable fission weapon – a shrunken version of the “Fat Man” bomb the U.S. dropped on Nagasaki – but who knows for sure? Not me.

  • Wayne

    Dick wrote:
    “Or it could just be a non-functional exercise in pretty machining. It looks plausible as a missile-deliverable fission weapon – a shrunken version of the “Fat Man” bomb the U.S. dropped on Nagasaki – but who knows for sure? Not me.”

    Caveat: I’m absolutely not an Engineer or a Physicist. so “not me” as well.
    Have read extensively on the concepts of implosion & gun-type weapons, in early American designs, as well as the challenges of putting together a workable “physics-package.”
    –The Pakistani’s & A.Q. Kahn were able to adequately engineer the physics-package for implosion type designs quite well. The concept is “simple,” but pulling it off requires the necessary industrial infrastructure on the back end.
    –Assuming the Korean’s have the necessary amounts of plutonium & the ability to machine & produce core’s–it’s definitely plausible.
    –I was under the impression using Tritium to boost the reaction was a more complex engineering task, but again I do not know. (The low-yield of their last Test could point to that, they don’t quite have it down pat, yet.)
    –They certainly have access to modern explosive’s by which to miniaturize the explosive-lens outer-shell & if they have the necessary timing/detonation procedures correctly to initiate the appropriate shock-wave, again it’s certainly plausible.

    There is a dark joke I’ve heard;
    Q: What do you call a crazy dictator of a slave-state, with a workable bomb?
    A: You call him “Sir”
    And that perhaps sums up the little Troll’s motivation in part.

    On top of all the other destabilizing things in the world today–allowing crazy dictators to build the necessary infra-structure & share the fruits among & between themselves– we are headed for even more crazy things in the short/intermediate term.
    Concurrently– Obama’s success in diminishing our reach & influence in the world does not bode well for anyone.

  • Steve Earle

    This is exactly why the Israeli model of Nuclear Deterrence was always my favorite. Bomb them to bits BEFORE they build them in numbers, learn how to hide them, and figure out how to deliver them (or sell them to terrorists with rental trucks)

    Hit them while they are still vulnerable and at worst can wage a conventional war to retaliate.

    Or, Obama’s plan (which he has apparently forced onto the Israelis…), wait until they can wage theater nuclear war, or even worse, intercontinental nuclear war….. and wind up costing millions of lives.

  • wayne

    Steve — on board with that thought fully!

  • Wayne

    Interesting current podcast from/at John Batchelor Show;

    “Nuclear Arsenals and the New Cold War,” (Elbridge Colby–Center for New American Security.)

    Disturbing discussion (in part, in brief) referencing “nuclear weapons = no regime change,” for such rogue states as N. Korea or others who can obtain even small arsenal’s.

    John Batchelor is a Gem. Very interesting & diverse Author interview’s as well, (especially on the weekend feed.) And of course… Mr. Z & others on all-things-space.

  • Steve C

    That does not look like an a-bomb, it looks like an aluminum sphere that has been decorated with a rotary sander. Here are some pictures of Fatman and Little Boy being assembled for comparison. http://www.dailymail.co.uk/news/article-2786215/Inside-America-s-atomic-bomb-programme-Never-seen-photos-reveal-preparations-attacks-Hiroshima-Nagasaki.html

  • Edward


    It may not look like the original US atomic bombs, but advancements have allowed for modern nuclear bombs to be smaller, thus they look different.

    Whether what we see in the article’s photographs is a real atomic bomb or just a shell of one is another matter. It really depends upon what technology the North Koreans gained from other countries.

    Meanwhile, the experts seem fairly certain that North Korea has an atomic bomb, they just don’t seem to be so sure, yet, whether they have one small enough that their rocket can deliver to distant continents.

  • Wayne

    Steve C wrote:
    “Here are some pictures of Fatman and Little Boy being assembled for comparison.”

    Yes, but that’s 1945 technology. We developed a workable bomb in 3+/- years, under war-time conditions. We were sure the gun-type method would work, no problem. The implosion method was more difficult to engineer & therefore had to be tested first, but it worked.

    The Troll in N. Korea however, has the benefit of whatever plans/designs the Pakistani’s sold him, plus a large amount of accumulated knowledge on the workings of nuclear bombs since 1945, largely in public-domain. Once he was able to make and/or purchase the nuclear materials, the engineering is “relatively” easy.

    Modern explosive’s and digital timing/detonation procedures allow for a vast reduction in the outer implosion shell. The physic’s-package is more complex, but again that knowledge is widely available and/or can be calculated “relatively” easily. Whether they are using solid cores, or hollow cores, we of course do not know, but it’s not beyond their capability.

    The bottleneck in bomb-making, for all intents & purposes, is the nuclear material. Once you have that, the “cat’s out of the bag.” The engineering is very do-able, even in the Hermit Kingdom.

    –The timing fuses for example, (“Krytrons,”) are very well developed technology & already miniaturized. (They have dual-use, bombs & commercial equipment, and are made in industry.)

    Granted– I am not a physicist or an engineer, but if you were to spend just a few hours researching how implosion devices work, it’s frightening “simple.” I’d wager you yourself could sketch a design, that would “work” if you only had the “necessary ingredients.”

    The Pakistani’s took, what– 10 years? And N. Korea has been working on this for far longer. They have already detonated a bomb in the past. Once they have the basic procedures & materials down pat, making them smaller is again, “relatively” easy. (Took us barely 10 years to produce the “W-19” & “W-23” artillery shell warhead(s), and those baby’s were small.
    (Discounting the N. Korean’s ability to do such things, is at our at our own peril, to be sure.)
    This is what is so scary about the whole affair & the primary reason we have historically tried to limit “proliferation” of the material’s. The Physics can’t be un-learned, all you require is access to the nuclear material. That’s basically 60-70% of the work necessary

    I have no clue if the picture is a non-working show-piece, but at this point it really doesn’t matter. Even if they only had 1 of our 1945 era design bombs, correct me if I’m mistaken, but I believe that would be missile-deliverable on it’s own.

    The Great Leader Troll fully intends to continue the development & we in the West have done little to stop him.

    It’s only a matter of time before he puts a bomb on an ICBM, and then things get very destabilized. And if they are anywhere near boosting their weapons with D/T, all bets are off.

    If I’m totally crazy on this, please correct me. (Love to hear from anyone who knows infinitely more than I.)
    Again, not a physicist/engineer, but just imagine what can-be accomplished if a whole country devotes massive amounts of resources to the task, buys designs, builds/rruns their own reactors, etc., etc. From what I have read from publicly available material (from our own DOE to boot)– it’s scary & I fear we all have been sticking our heads in the sand as far as N. Korea, and now Iran.

    Thanks for reading.

  • Wayne

    Steve C:

    Forgot to thank you for that link.!

    I had never seen those particular picture’s before, so “way-cool.”- thanks.

    Interestingly as well– there are a large number of DOE sponsored films outlining rudimentary nuclear-bomb processing steps. They were “scrubbed” of “classified material” but still very interesting.

    The shear amount of publicly available information is astounding (library’s, depositories, everything & now the internet) when you think of it, and “everyone else” you can be sure, made use of all that information. (which you & I paid for, no less)
    It served to guide other physicist/engineers in their (evil- IMO) machination’s, and cut years off their efforts.

  • Wayne

    Edward: (hey!)

    Google “Krytrons,”
    –I tend to think these are in your bailiwick & you would know infinitely more than I about how they work. (“electrical circuit stuff”) Highly controlled for export, but that just means they cost a lot on the Black Market. Nothing the Troll in N. Korea couldn’t afford.

    (I don’t understand How they work, just that they do…)
    “Krytrons and their variations are manufactured by Perkin-Elmer Components and used in a variety of industrial and military devices. They are best known for their use in igniting exploding-bridge-wire and slapper-detonators in nuclear weapons, their original application, either directly (sprytrons are usually used for this) or by triggering higher-power spark gap switches. They are also used to trigger thyratrons, large flashlamps in photocopiers, lasers and scientific apparatus, and for firing ignitors for industrial explosives.”
    If you have enough of these guys, you can tightly control triggering of explosive lens’s in an implosion device down to the millisecond(?) level.

    They allow for extremely high-voltage, simultaneous pulses of electricity, and are very small.

    It’s the one piece (well maybe a few more) of technology the Israelis could not produce on their own for their bomb-program in the 1960’s. USA would not allow export to them, but they managed to obtain enough of them to study, and given their smart’s, they undoubtedly learned to build them, ‘cuz they have 100-120 warheads. (“allegedly”) (And thank God they do!!)

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