Scientists at US laboratory ready to create fusion energy tells that the Lawrence Livermore National Laboratory has a new potential fusion engine. Before discussing it, let's think about fusion reactions. The most common isotope of hydrogen has a single proton and one electron. Deuterium has an additional neutron and tritium has two neutrons, but both with one proton and electron. The most practical fusion reaction is combining a deuterium nucleus with a tritium nucleus. That reaction produces helium-4 (the most common isotope of helium) and a high-energy neutron. The helium nucleus gets 1/5 of the energy and the neutron gets 4/5. (By the way, there is no chemical reaction that can produce helium.)
In order to combine the deuterium and tritium nuclei, a physical force must overcome the electrostatic repulsion of the two nuclei, which both have a positive charge. That is why high temperatures, approaching 100 million degrees Centigrade is required. At high temperatures, the atoms have high speeds and they can collide despite the electrostatic repulsion. The problem in the past six decades has been keeping the atoms close enough that a chain reaction can occur.
In case you are interested, the core temperature inside the sun is only about 15 million degrees Centigrade, but its tremendous gravity helps overcome the electrostatic repulsion. The tokamak was invented by Russian physicists Tamm and Sakharov in the 1950s. Its operating principle is to contain the hot gas (plasma) in a helical magnetic field. The problem has always been to produce more energy than required to power the tokamak. With some luck, researchers might find the recipe that could bleed energy out of the plasma to power turbines.
The scientists at Livermore have a different approach. Suppose a fuel pellet was suddenly bombarded with energy from a powerful laser. Similar to the implosion that enabled the early atomic bombs, the same thing happens with the pellet. The energy from such a fusion generator would be in packet of time, not unlike an internal combustion engine. At the national laboratory, they focus 192 laser beams to fuse the hydrogen isotopes together. The National Ignition Facility explains the aggregate laser system is 60 times more powerful than any previously constructed. Two million joules of energy in one billionth of a second pulse will be focused upon the fuel pellet, about the size of a pencil eraser.
Jeepers. This system is still incredibly complex. It is difficult to look at the facility (larger than three football fields) and imagine it ever producing more power than it consumes. Yet I guess Goddard's first rocket had little in common with the Saturn V that propelled astronauts to the moon. Commercial hydrogen fusion is still a decade away, at the earliest.
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