# What does HE stand for in "explosive force of the HE"? **URL:** \ **Category:** Factual Questions\ **Created:** [March 6, 2017, 8:51am UTC](https://boards.straightdope.com/t/what-does-he-stand-for-in-explosive-force-of-the-he/781529 "2017-03-06T08:51:29Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [March 10, 2017, 5:29pm UTC](https://boards.straightdope.com/t/what-does-he-stand-for-in-explosive-force-of-the-he/781529/21 "2017-03-10T17:29:19Z")
> [@Tranquilis](#): > > Sure. And they actually said that. But then, they also had you hand-machining weapons-grade fissile material. Which is _incredibly_ dangerous from a heavy metals perspective, not to mention a powerful Alpha-emmitter. Chances of NOT getting some of that crap in your lungs and eyes, absent quite extreme protective\* measures? Nil. _Buh-bye._ > > \*Especially so, considering the state of PPE at the time. You know those suits they use at the CDC, where a positive pressure fan keeps them inflated? There must be something like that available on the commercial market for working on asbestos or other toxic chemicals. The plastic suit itself would protect someone from any alpha particles, and since the air would come from a hose that goes to a filtered inlet somewhere away from the radioactive machining, the terrorist would be fine. I mean, not that it matters. I would guess it would take several years to develop lung cancer or at least weeks for heavy metal poisoning, from inhaling a bunch of plutonium or uranium dust. Once that device goes off, I would expect the would be bomber’s lifespan would be measured in days. ---
**Author:** ![Tranquilis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tranquilis/32/3639_2.png) [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)\ **Post date:** [March 10, 2017, 5:34pm UTC](https://boards.straightdope.com/t/what-does-he-stand-for-in-explosive-force-of-the-he/781529/22 "2017-03-10T17:34:58Z")
> [@SamuelA](#): > > You know those suits they use at the CDC, where a positive pressure fan keeps them inflated? There must be something like that available on the commercial market for working on asbestos or other toxic chemicals. The plastic suit itself would protect someone from any alpha particles, and since the air would come from a hose that goes to a filtered inlet somewhere away from the radioactive machining, the terrorist would be fine. > . Now? Absolutely. They’re heavily used in the commercial hazmat cleanup industry. Back then, when the article was published? Nope, and double-nope. Plutonium is a hard-core poison. Uranium is acutely nephrotoxic. Cancer will be the least of your worries. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [March 10, 2017, 6:54pm UTC](https://boards.straightdope.com/t/what-does-he-stand-for-in-explosive-force-of-the-he/781529/23 "2017-03-10T18:54:01Z")
> [@Machine\_Elf](#): > > Apart from that, I was under the impression that there were restrictions on the technology used to make bombs, e.g. even if you know you need [high-speed switches,](https://en.wikipedia.org/wiki/Krytron#Export_restrictions_in_USA) you may have a hard time obtaining them. There are [several ways](https://en.wikipedia.org/wiki/Critical_mass#Changing_the_point_of_criticality) to convert a sub-critical mass to a critical one. The high-speed switches are used in the compression method–surround a sub-critical sphere of fissile material with a shell of explosives, set them off to compress the sphere into a critical mass. The timing needs to be very precise to make the implosion perfectly symmetrical, or else you’ll end up just blowing all the fissile material material apart. But a “gun” type bomb would be dead simple to make by comparison, assuming that you somehow had access to the pre-shaped pieces of uranium.\* (I’ve contemplated how “simple” it might be possible to make a uranium gun bomb if you had the materials–for instance, could you substitute an automobile air bag for the explosives used to bring the two sub-critical masses together?) \*Uranium was what was used for the Hiroshima gun-type bomb, but I don’t know why you couldn’t in theory use other suitable fissile materials if you somehow had them handy, such as plutonium 239, neptunium 236, or curium 245. Californium 252 would allow for an especially small critical mass, but the 2.6 year half-life would make it somewhat tricky to work with. (You can see various isotopes and critical masses for a sphere of the material [here](https://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of_a_bare_sphere). Not all radioactive isotopes listed. For instance, I wonder how big a ball of pure carbon 14 you would need, if you could magic one up.) ---
**Author:** ![commasense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/commasense/32/3017_2.png) [@commasense](https://boards.straightdope.com/u/commasense)\ **Post date:** [March 10, 2017, 7:33pm UTC](https://boards.straightdope.com/t/what-does-he-stand-for-in-explosive-force-of-the-he/781529/24 "2017-03-10T19:33:04Z")
> [@davidmich](#): > > Thanks commasense. It’s surprising to me that Mullen’s book isn’t better known. It’s self-published by a person who, although knowledgeable about the details, clearly didn’t know much about creating a book. He would have done well to hire an editor. (This may sound self-serving once you know that I’m a copy editor by profession, but when you see the book, you’ll understand what I mean.) It’s more of a scrapbook than a real book. The primary text is less than 90 pages, followed by 300 pages of appendices that include declassified documents, original drawings and photographs, and 40 pages of endnotes that contain some of the most interesting material. So you really have to dig through it to get at the best stuff. AFAIK, he was the first researcher to publicly disclose that point I made above: that the projectile in Little Boy was not a “male” bullet being fired into a “female” target, as virtually every other source claimed or implied, but exactly the other way around. But IIRC, this revelation only appears in one of the endnotes, and you have to refer to a drawing a few hundred pages earlier to see exactly what he is talking about. Talk about burying the lede! I daresay many people who have bought the book have either assumed it was an amateurish collection of arcana, or have been put off by its relatively poor organization, and haven’t spent the time needed to mine the gems it contains. In the 1980s I worked on a Smithsonian video history project that interviewed many of the Manhattan Project scientists, and visited many of the sites. So my bookshelf on the Manhattan Project is fairly substantial. But I only heard about Coster-Mullen’s book by chance a year or two ago, nearly a decade after he first published it. ---
**Author:** ![commasense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/commasense/32/3017_2.png) [@commasense](https://boards.straightdope.com/u/commasense)\ **Post date:** [March 10, 2017, 7:56pm UTC](https://boards.straightdope.com/t/what-does-he-stand-for-in-explosive-force-of-the-he/781529/25 "2017-03-10T19:56:05Z")
> [@Darren\_Garrison](#): > > \*Uranium was what was used for the Hiroshima gun-type bomb, but I don’t know why you couldn’t in theory use other suitable fissile materials if you somehow had them handy, such as plutonium 239, neptunium 236, or curium 245. Californium 252 would allow for an especially small critical mass, but the 2.6 year half-life would make it somewhat tricky to work with. (You can see various isotopes and critical masses for a sphere of the material [here](https://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of_a_bare_sphere). Not all radioactive isotopes listed. For instance, I wonder how big a ball of pure carbon 14 you would need, if you could magic one up.) I don’t know about the other elements, but the Manhattan Project scientists determined fairly early on that Pu239 wouldn’t work in a gun device. As you say, the gun method is dead simple, and plutonium was much easier to obtain in large quantities than U235 (relatively speaking), so plutonium in a gun device would have been ideal. But IIRC, a gun can’t bring subcritical masses of Pu239 together fast enough. The reaction starts well before they are in contact and blows the device apart in a comparative fizzle. That’s why they had to develop the implosion method used in Fat Man, where a hollow subcritical sphere of plutonium is compressed on all sides by shaped charges of HE. Fun fact: one thing the 1986 movie got right was the arrangement of the shaped charges. In the film, the lead character is trying to figure this out, and glances at his soccer ball. Eureka! He uses that pattern of hexagons and pentagons for his explosive charges. The real Trinity device and Fat Man weapons also used that pattern. However, that’s not the “secret” of the shaped charges: it was the combination of different HEs within those molds that created the symmetrical wave front that compressed the fissile material. That was mostly figured out by chemist [George Kistiakowski](https://en.wikipedia.org/wiki/George_Kistiakowsky), who was looked down on by many of the MP physicists for being a “mere” chemist. But without Kistiakowski’s contribution, there might not have been an implosion weapon. And implosion has been the main method for virtually all nuclear weapons since. The gun method was rarely if ever used in weapon design again. [Previous page](https://boards.straightdope.com/t/what-does-he-stand-for-in-explosive-force-of-the-he/781529.md?page=1)