Computer simulations said “Yes,” Reality said “No”April 6, 2013
Energy is the lifeblood of civilization – the more the better. One of the great hopes for the last 50 years has been clean energy from fusion, and many very fine physicists have dedicated careers to this holy grail. Perhaps the greatest hope for fusion has been the National Ignition Facility at the Lawrence Livermore National Laboratory.
At the National Ignition Facility the plan is to compress a small bead containing hydrogen to the extreme temperature and pressure at which fusion will occur. This compression would be accomplished with an extraordinary array of high-powered lasers that would all converge on to a tiny 2mm bead. If all works well the enormous amount of energy to power the lasers would be more than replaced by the energy released by the fusion reaction. The hope is to repeat this process with a new hydrogen bead 16 times a second, yielding a continuous supply of useful heat to generate electricity.
Scientist at the National Ignition Facilty expected that hydrogen ignition (the point where fusion occurs and more energy is released than invested) would occur last year. But it didn’t. According to ScienceNews…
A lot of that confidence came from computer simulations… Each simulation consisted of more than a million lines of code filled with numbers and equations describing every push and pull that nuclei in the fuel capsule would encounter once the laser fired. All the data included in the simulations were based on well-tested theories and rigorous experiments, including measurements from hundreds of thermonuclear bomb explosions. The world’s fastest supercomputers required days or weeks to spit out the results.
Many of these simulations predicted that NIF’s 192-beam laser would comfortably achieve ignition. They showed that a short, powerful laser pulse coming from all directions would compress the pellet enough to create heat and pressure more intense than that in the sun’s core, forcing hydrogen nuclei together to form high-energy helium nuclei and neutrons.
No such luck.
Ignition was a failure. I am not condemning the scientists at the National Ignition facility. In this type of endeavour failure is just a stepping stone to success. In fact, I have great admiration for the folks working on this project and I hope funding and research continues.
Here’s the thing: those millions of lines of code were modeling something that is relatively simple. Hydrogen nucleosynthesis is well understood. The models had to simulate just a single compression and ignition event. There were only a few variables compared to the thousands of variables for something as complex as, say, the climate of the planet Earth.
I have a lot more faith in talents and mental horsepower of the quiet anonymous physicists modeling the relatively simple fusion of hydrogen than I have in some of the self-important bumbling climate modelers working on the vastly more complex climate of the planet.
Just consider the grand poobah of climate modelers, James Hansen. Ira Glickstein did a nice job of pulling back the curtain on Hansen’s modeling skills with this …
The folks at the National Ignition Facility run their experiments, perhaps sometimes chastened by the results, but wiser and closer to their ultimate goal.
Hansen’s experiments are run by nature and take decades, but when he is wrong he is hardly chastened. Hansen retired from his position at NASA a few days ago. The Washington Post reported that Hansen said he was retiring so he could “spend full time on science.” Does that mean he wasn’t spending his time on science at NASA? His friend, Bill McKibben was probably closer to the mark when he said Hansen “decided to step down so he could engage in lawsuits and protests full time.”
Hansen was also predictably lauded by his friend Gavin Schmidt. I guess McKibben and Schmidt haven’t seen the above graph.