Tag: nuclear test

Water bomb

By Phil Plait | September 26, 2012 10:30 am

Via Jenny Winder, I saw this video showing footage from underwater nuclear bomb tests in 1958. It’s astonishing.

The awesome power and energy released is difficult to wrap your head around. Think on this: a cubic meter of water weighs a ton. Now imagine taking a single cubic meter of water and lifting it, say, 100 meters in the air, accelerating it to several hundred kilometers per hour.

Now look again at that plume. How many cubic meters of water were are in it? Even being conservative I’d say it was in the millions, meaning millions of tons of water blasted upward and outward by the force of the explosion. It’s terrifying. And mind you, the test shown was for a relatively small blast: about an 8 or 9 kiloton yield (the equivalent of 8-9 thousand tons of TNT), whereas big nukes are capable of 20 megatons, over a thousand times the explosive yield shown.

I’m fascinated by big bangs – from the first one, to supernovae, and all the way down to bombs we humans make in our clever and plodding attempts to kill one another. Every now and again it’s good to get a solid reminder of just what these explosions are capable of.


Related Posts:

- The 50th anniversary of Starfish Prime: the nuke that shook the world
- What the hell were we thinking?
- Starfish Prime
- Would you stand under a nuclear blast?

CATEGORIZED UNDER: Piece of mind, Science

Would you stand under a nuclear blast?

By Phil Plait | July 24, 2012 7:00 am

As a rational human, I’m aware of finding my emotions and prejudices conflicting quite often with my knowledge of science and reality. Being reasonable is relatively new to us apes, and a hundred million years of evolving reactionary emotions usually takes precedent.

So I find myself pretty conflicted about his video, which shows five men in July, 1957, standing around in the Nevada desert while a nuclear weapon is detonated above their heads.

[Note: the video says the detonation was 10,000 feet above their heads, but that is erroneous; it was more than 18,000 feet.]

This video comes from NPR via my own Discover Magazine. [Given what follows below, I'll note that the NPR article shows that these men were not adversely affected by the blast, and most lived to be old men. I strongly urge you to read that entire article, in fact. It's fascinating.]

When I watched the video, my feelings were curious. My first reaction was visceral: basically just "Aiieeeeee!"

But that was immediately followed by, "Well, the blast was low yield and about 18,000 feet up, so the odds of them getting hurt by it were pretty small."

The thing is, both thoughts are right! Here’s why.

The blast was indeed a small one. It was not a fusion bomb (usually called a thermonuclear or H-bomb), but instead was a fission bomb, an A-bomb. These release far less energy when they explode, though it’s nothing to be trifled with. This particular test was done using a 2 kiloton yield; in other words, it exploded with the energy of 2000 tons of TNT. For comparison, the only two atomic weapons used in wartime – by the US over Hiroshima and Nagasaki – had yields of about 13,000 and 21,000 tons of TNT. Hydrogen bombs have yields typically measured using megatons, or millions of tons of TNT.

So the explosion in this video was bigger than a usual conventional bomb, but not nearly as big as what we normally think of as a nuclear bomb. Right away we have to be careful how we think of this!

Second, the explosion was at a height of well over 5 kilometers (3 miles). As I pointed out in a recent BAFact, Earth’s air is quite good at absorbing various types of electromagnetic radiation (a fancy name for "light"), including X-rays and gamma rays. The men under the blast probably received no direct dose of ionizing radiation in that form. It’s possible the intense high-energy light from the bomb created secondary forms of radiation – high-speed electrons and so on – but again, the bomb yield was low, so all that air probably did a pretty good job stopping all that.

Third, what about fallout? This is radioactive material from the blast that falls from the sky. In an atomic (or an H) bomb, radioactive atoms are created and dispersed. In low altitude tests, the heat from the explosion can draw up dust from the ground, mix it with these materials, and create a radioactive cloud that can travel a long way. Raindrops can form, and the radioactive brew can literally fall out from the sky.

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The 50th anniversary of Starfish Prime: the nuke that shook the world

By Phil Plait | July 9, 2012 6:05 am

On July 9, 1962 — 50 years ago today — the United States detonated a nuclear weapon high above the Pacific Ocean. Designated Starfish Prime, it was part of a dangerous series of high-altitude nuclear bomb tests at the height of the Cold War. Its immediate effects were felt for thousands of kilometers, but it would also have a far-reaching aftermath that still touches us today.

In 1958, the Soviet Union called for a ban on atmospheric tests of nuclear weapons, and went so far as to unilaterally stop such testing. Under external political pressure, the US acquiesced. However, in late 1961 political pressures internal to the USSR forced Khrushchev to break the moratorium, and the Soviets began testing once again. So, again under pressure, the US responded with tests of their own.

It was a scary time to live in.

The US, worried that a Soviet nuclear bomb detonated in space could damage or destroy US intercontinental missiles, set up a series of high-altitude weapons tests called Project Fishbowl (itself part of the larger Operation Dominic) to find out for themselves what happens when nuclear weapons are detonated in space. High-altitude tests had been done before, but they were hastily set up and the results inconclusive. Fishbowl was created to take a more rigorous scientific approach.


Boom! Goes the dynamite

On July 9, 1962, the US launched a Thor missile from Johnston island, an atoll about 1500 kilometers (900 miles) southwest of Hawaii. The missile arced up to a height of over 1100 km (660 miles), then came back down. At the preprogrammed height of 400 km (240 miles), just seconds after 09:00 UTC, the 1.4 megaton nuclear warhead detonated.

And all hell broke loose.

1.4 megatons is the equivalent of 1.4 million tons of TNT exploding. However, nuclear weapons are fundamentally different from simple chemical explosives. TNT releases its energy in the form of heat and light. Nukes also generate heat and light, plus vast amounts of X-rays and gamma rays – high-energy forms of light – as well as subatomic particles like electrons and heavy ions.

When Starfish prime exploded, the effects were devastating. Here’s a video showing actual footage from the test, 50 years ago today:

As you can see, the explosion was roughly spherical; the shock wave expanding in all directions roughly equally since there is essentially no atmosphere at that height. Another video has many more views of the test; I’ve linked it directly to those sequences, but if you start at the beginning it’s actually an hour-long documentary on the test.


Nuke ‘em ’til they glow

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