I’ve been reading “Caging the Dragon” on the flight to London and it reminded me of a little song from Sesame Street that goes:
One of these things is not like the others
One of these things is just not the same.
What reminded me of that? These three yields:
– Fission yield
– Fusion yield
– Hydrodynamic yield
Can you spot the one that’s not like the others? (Hint: Perhaps it’s easier to try to figure out why two of these are the same.) No fair googling the answer! I didn’t have access to google on the airplane and you shouldn’t use it either.
Spoiler Alert: as I might have expected, keen wonk-readers got the answer right away, so only read the comments if you want to see what others have said.
The former two are both components of a measurement of total device yield, whereas the latter is an instance of said measurement (based on seismic measurements, iirc) — no?
I mean, a nuclear weapon isn’t a hydromagnetic device so much as it has hydromagnetic effects, right? Is there something deeper you’re going for here?
The fission/fusion yields are the actual energy output of the device.
Hydrodynamic yield is a measurement of that output based upon measuring the shockwave thru the rock.
The first two are “real”, and the last may or not be a spoofed determination.
hydrodynamic, not hydromagnetic; but you are both right that hydrodynamic yield is a measurement of the yield. Its not done seismically though. That would be seismic yield. Its done by looking at the rate and distance along a cable that is crushed by the shockwave. (In measurements that are called either slifer cable or CORRTEX, depending on the electronic circuitry.) Since that cable is crushed only in the near field (i.e. within tens or perhaps hundreds of meters of device), it cannot be spoofed.
I must admit that I was confused for quite a while as I read it since hydrodynamics plays such an important role in both the fission and the fusion yields. (Caging the Dragon is great, but it does assume a level of familiarity with their buzz words.) But you guys are smarter!
Sorry, but given the title of the blog post, I cannot resist:
http://www.youtube.com/watch?v=jWvOA7Z4yEs
Enjoy!
Tom.
Thanks Tom, thats great!
re: hydromagnetic vs hydrodynamic
Sorry Geoff, I’ve been spending time with tokamaks and plasmas recently… Weston Stacey’s “Fusion Plasma Physics” as opposed to trusty ol’ Zel’dovich and Raizer =D.
ACW definitely needs more contests.
Geoff – The “spoofing” I was referrng to was not altering the readings of the sensor. It was using decoupling tricks (such as “Diamond Dust”) to dampen and/or modify the transmitted shockwave into the medium surrounding the sensors.
During a hydrodynamic test, fissile material in a nuclear weapon is replaced with a non-fissile material such as U-238 or PU-242. When these modified weapons are detonated, the non-fissile materials are put under enough heat and pressure that they behave like liquids. When this happens, radiographs that use x-ray photographs of the explosion can be used in order to predict how a nuclear device with fissile material would act.
The radio lanthanum hydrodynamic testing method was first used by the United States based Manhattan Project during the development of the first implosion fission nuclear bomb. In this process, a radioactive sample of lanthanum was placed in the center of an implosion test device and detonated. A series of Geiger-Mueller counters were used to observe the behavior of the material as it imploded. This crude method of hydrodynamic testing helped to develop the Fat Man plutonium implosion bomb that was used on Nagasaki, Japan.
So hydrodynamic tests don’t actually have a nuclear yield.
Also, hydrodynamic and fusion tests are allowed under the CTBT and fission are not.
Zak,
Hydrodynamic TESTS, and hydrodynamic YIELD are different things.
Hydrodynamic testing is measuring and analyzing the physics within an imploding system. There is no significant nuclear yield. This testing is done by the weapon builders.
Hydrodynamic yield is done by external monitoring groups to determine the size of an underground nuclear test. This is a method to measure an actual atomic explosion.