Why Today, July 1, Might Be Termed Independence Day

Recently I had occasion to read about the discovery of the remains of the USS Independence, an American veteran aircraft carrier that fought in WWII. As I had never heard of its fate, I was interested and began to delve. 

I've long had a special fascination with the Independence-class light carriers. When I was wargaming in miniatures 35 years ago and just beginning accumulating a 1/2400 fleet (1" = 200 ft), I built myself a USS Independence from balsa and cardstock.


The Independence wore hull number CVL-22, and it was the lead ship of a class of nine "light" carriers in WWII. They were all constructed from repurposed cruiser hulls, which meant they didn't have the internal volume to match "fleet" carriers, and they carried a reduced air component of 30-33 planes. The great virtue of the class was that the ships could be completed quickly from hulls already in production for the CL Cleveland class of light cruisers. This was in a period when Essex-class fleet carriers were not yet coming off the lines.

These light carriers served with distinction during WWII. The USS Princeton was scuttled after incurring severe battle damage, but the others survived the war.

In 1946, Operation Crossroads was conceived as a test of the effects of an atomic bomb against naval vessels.  The authorities shuttled all the inhabitants of Bikini Atoll hundreds of miles away, to Rongerik Atoll, telling them their homes were needed by Uncle Sam for crucial experiments. (This was a pretty shameful incident - as no one told them that the experiments would prevent them from ever returning to Bikini in their lifetimes, due to radioactivity.)

On July 1, 70 years ago today, the first of a planned series of test explosions was triggered; this was called the Able shot. It was a plutonium bomb pretty much identical to the one we had dropped on Nagasaki, and it had a yield of 23 kilotons of TNT.  (It was one of only seven atomic bombs in the world at that time.) This bomb was aimed at the middle of a fleet of 78 ships moored in Bikini Atoll's lagoon. Many of these were surplus naval vessels; others were captured from our opponents (including Germany's Prinz Eugen, which accompanied the battleship Bismarck on its last voyage).

Able was dropped from a B-29 flown by a carefully trained crew.  We still don't know, however, how it managed to miss its aimpoint by such a very large margin - almost half a mile! As it turned out, only 5 ships were sunk, the largest of which was the ex-Japanese cruiser Sakawa. The explosion occurred at 520 feet of altitude and 560 yards away from the Independence, on her quarter. The blast wave maimed her... but she was still there.  


  Note the two crewmen posing, about halfway up.

 Because the explosion was sufficiently high, there was no local fallout - all the radioactive isotopes from the bomb were sucked into the stratosphere and dispersed. Sailors boarded the ships the next day. Some thousands of assorted animals had been tied or caged in normal crew duty stations aboard 22 of the ships. Only 10% died due to blast and 15% died due to the single pulse of neutron radiation. 


  The Independence was again moored in the lagoon for the second test, Baker shot, 24 days later. Baker was not dropped, but was suspended 90 feet underwater. This time Independence was over 1200 yards away and escaped further damage... but - she was heavily contaminated with radioactive seawater and coral and other debris from the underwater shot. She was selected for a concerted program of testing decontamination techniques over the next four years - which failed. Nothing ever tried was successful in removing the contamination beyond what the original hose-down managed, except for sand-blasting down to bare metal. The radioactivity among the anchored fleet was so pernicious that the remaining planned underwater test was cancelled. The Baker test remains a black eye on America's nuclear testing program for its unanticipated results. Only nine of the 78-ship fleet were lightly-enough contaminated to be sold for scrap. The rest sank from the explosions or were scuttled when decontamination attempts failed.

Accordingly, authorities decided to deep-six the Independence. Many drums of radioactive wastes were loaded aboard her, then she was towed to the Farallon Islands about 30 miles west of California, in Monterey Bay, and scuttled in 1951. There she rested for over six decades in quiet and darkness.

In 2015 an effort by NOAA and Boeing Corporation imaged the remains of the Independence in 2,600 feet of water. They were able to conduct high-definition multi-beam sonar scans, which reveal that the ship settled upright. 

'After 64 years on the seafloor, Independence sits on the bottom as if ready to launch its planes,' said Mr Delgado, chief scientist on the Independence mission and maritime heritage director for NOAA's Office of National Marine Sanctuaries.
'This ship fought a long, hard war in the Pacific and after the war was subjected to two atomic blasts that ripped through the ship. It is a reminder of the industrial might and skill of the 'greatest generation' that sent not only this ship, but their loved ones to war.'

July 1, 1946 didn't belong only to the USS Independence, but she survived the first of two atomic bombs at close range on that date. And now, thanks to advancing technology, we've located her again, where from her watery grave she still projects an amazing sense of readiness.

Happy (USS) Independence Day!


Minor Miracle

This year there was a lot of activity among my Facebook friends on Veterans' Day, to remember fathers', sons', and even their own days in uniform for their country. That put me in mind of the uniform I hung in my closet in 1988 when I mustered out of the US Army Reserve, and I wondered: Why do I still have it? I probably can't even fit into it.

Well, I'm proud to report that, with a little "sucking it in," I can indeed still don my uniform! (I also can do my age in push-ups, which means I can beat my best boot camp performance by five!) So I felt compelled to brag here, because I don't know at what age I'll go to seed and lose what fitness I've retained.

That's my excuse, and I'm sticking to it.


A Very Scary Halloween

On Halloween (continental U.S. time), 1952, American scientists exploded the world's first hydrogen bomb. Called Ivy Mike ("Mike" being the phonetic for "M", and Mike being the first bomb design planned to reach megaton yield), this was lit off on the island of Elugelab. Elugelab was one of the 40 islands comprising the outer edge of the Enewetak Atoll, and it was vaporized.

  Enewetak Lagoon, from Google Earth imaging

Mike was impractical as a weapon. It used a liquid deuterium fusion fuel (deuterium is a heavy isotope of hydrogen) and consequently the whole apparatus had to be cryogenically cooled to not far above absolute zero. A whole gas liquefaction industry had to be founded in order to make this possible.

The U.S.A. had felt itself to be in a race with the USSR for a fusion weapon - not for reasons of national prestige, as in our Moon program, but as a deterrent against attack.  The military had felt pretty good about its nuclear inventory, until in September, 1949, American "sniffer" planes picked up radioisotopes over the northern Pacific which had their origin (as measured by their proportions and their known half-lives) on the same day - meaning they were formed in the heart of a nuclear explosion. In fact, the American commercial company that developed the analytical techniques and had been working with routine samples for months was able to specify nearly the exact time of the explosion; they were only off by 1 hour, though the explosion had been a couple weeks before.

  "Joe-1", first Russian test, an exact copy of our own "Fat Man" from stolen plans

Suddenly, we no longer had a nuclear monopoly.  And no one trusted Joe Stalin not to use, or at least, threaten to use, his new capability.  American scientists decided we needed a hurry-up program to move up to a fusion bomb, which had been proven theoretically possible years before.  They had been sitting on a proposed design, called "Alarm Clock" but it was still just a theoretical mathematical construct.

The big deal about hydrogen bombs, as opposed to atomic bombs, is that their yield is essentially unlimited; you just add more fuel to the design. (Fission, or atomic bombs, have inherent limits on yield to a few hundred kilotons.) Hydrogen bombs, however, require an atomic bomb to set them off. They must attain pressures and temperatures comparable to the interior of the sun in order to ignite the fusion reaction. (The sun, of course, is fusing hydrogen into helium all the time.)

The work was slowed but improved by the invention of the Ulam-Teller design (named after the physicists who came up with it). Instead of explosive compression of the deuterium, they would use the shock wave of the fierce radiation from the fission bomb to compress the fuel faster and better, leading to better ignition and yield.

The Ivy Mike shot was fired without a hitch. To help analyze the physical processes as they happened, engineers constructed "light pipes" into the side of the device and then led that light down a 9,000-foot plywood tunnel containing helium-filled polyethylene balloons  to a fortified bunker on another island, where instruments would measure the light and neutron fluxes before the fireball vaporized the whole thing.

Ivy Mike yielded 10.4 megatons, meaning the explosion was equivalent to 10.4 million tons of TNT going off at once.  It was 1,000 times the power of the bomb that destroyed Hiroshima.

  Ivy Mike

The explosion left a crater 200 feet deep, erasing the island of Elugelab.  Here is a Google Earth image of the site (which is the northernmost part of Enewetak in the first picture.) I've drawn a diameter which shows it to be almost a mile across.  The crater to its right is from H-bomb test Castle Nectar a little over 6 months later (1.7 Mts).  

  Ivy Mike & Castle Nectar craters

The small fish-shaped island just to the east of that is Bogon, home to a small atomic weapon blast: Seminole (13.7 kilotons). You can see the difference in size of craters.