May 292015

Operation Ivy was a nuclear test series of only two tests, carried out in the Pacific in late 1952, using the most powerful bombs then available.

The Mike shot (Ivy Mike) was the first US thermonuclear test, November 1, 1952. While the yield was impressive (10.4 megatons) as are the photos of the mushroom cloud, what really tells the tale is the before-and-after aerial photo of Enewetak Atoll showing the crater the ground-level blast punched into the Earth:


The fireball reached four miles in diameter, while the mushroom cloud topped out at 136,000 feet in altitude and spread to 100 miles in diameter. The crater was more than 6,200 feet in diameter and 164 feet deep; the island was stripped bare of vegetation and structures.

The Ivy Mike test used a one-off type of thermonuclear bomb that utilized liquified (cryogenic) deuterium. This resulted in a wholly impractical device as far as deliverable weapons go, but it was adequate to test the effects of decamegaton devices, as well as the basic physics.

A good documentary about Ivy Mike:

And a one-hour contemporary film about the test (the full-length film that the first clip above was taken from):

 Posted by at 12:31 am
  • Adam

    Are there any good calculations/measurements/estimates as to what the temperature would be at the hypocenter of a ground-level detonation of this magnitude, preferably given as a range of integer values?

    • Scottlowther

      I’m not sure I’ve seen much that gives the temperature of solid targets of nukes, and even the data I’ve seen on the temperature attained within the fissioning/fusioning parts of the bombs themselves has been pretty vague. Best I’ve seen is that H-bombs can attain 150 million degrees F and C (first one, then t’other), but these temperatures would rapidly drop off with distance, with the fireballs – which is air superheated because it has absorbed the X-rays produced by the bomb – reaching temperatures in the hundreds of thousands of degrees C and up.

      Since a gas that has been heated to incandescence, such as a fireball, is largely opaque to radiation, the temperature outside the fireball is vastly less than that within the fireball. What might be a million degrees inside radiates at 10,000 degrees to the outside because the photons inside the fireball cannot escape it. Of course, if the fireball expands to *you,* you get to experience the interior temperature directly, so, lucky you.

      With an atmospheric test, you don’t get roasted by the nuke itself; you get roasted by the thermal radiation given off by the fireball. This radiation is substantially less energetic than the Xrays given off by the bomb itself… but by capturing the Xrays and converting them into lower-energy infrared and visible light, the fireball expands the *duration* of the exposure, and thus the results are pretty much the same. But for a vacuum burst, such as an Orion pulse unit going off, there’d only be an *extremely* brief blast of radiation and only a trivial fireball produced by the structure of the bomb itself. You’d get hit with the Xrays, gamma rays and neutrons more or less directly, with much less thermal radiation.

      • Adam

        What would be the response of a spacecraft structure to a 10 MT nuke going off 100 yards from it in space?

        • Scottlowther

          “Ha ha, I laugh at your pitiful little firecracker.” – Death Star

        • CaptainNed

          Ask Captain Kirk, or just watch the TOS episode “Balance of Terror”.

  • se jones

    Well Scott?

  • B-Sabre

    Big baddaboom….