Part 2 of 6 Parts (Please read Part 1 first)
Samuel Cohen’s goal is an ultra-compact reactor that will use a fuel mix containing helium-3 which is an isotope that yields a particularly clear form of fusion with a minimum risk of generating radioactivity. One problem is the fact that helium-3 is a very rare material. Cohen explicitly says, “So we’re not trying to make power for everybody.” His goal is to develop a fusion reactor for a specific niche use such as a spacecraft engine. The reactor would fire a very thin plasma from one end so it can function as a rocket.
Such a direct fusion drive for spacecraft would only produce a tiny acceleration. In space, that minimal push would meet no resistance. In a year of two, a spacecraft with the DFD could get a ten-ton spacecraft half-way to Pluto traveling at over thirty miles per second.
Cohen says, “Then you’d turn around and decelerate. And when you got to Pluto, you’d go into orbit.” At that point, the reactor could turn off the ion rocket and convert itself into a one-megawatt electrical power source. “Some of that power you can use to send high-definition video back. And some of it you can beam down to a lander that you've placed on the surface, so it could drive around and drill holes in the ice.” The same type of DFD rockets could also be used to explore the moons of Jupiter and Saturn, or the icy bodies of the Kuiper Belt beyond Pluto, or anywhere else in outer solar system.
There is a major roadblock on the way to a DFD and that is the fact that before a DFD can be developed, a fusion plasma must be created and controlled. Dean says, “If you want to make a fusion exhaust system, you still have to be able to make the fusion plasma.” Researches have been working on harnessing fusion power since the 1920s when it was discovered that fusion processes are taking place in the hearts of stars. However, neither Cohen or anyone else has achieved break even fusion in spite of the century of research.
Experienced researchers such as Cohen know the pitfalls of fusion research. Until the late 1990s, Cohen’s professional life was centered on the ITER project which is seen as the ultimate expression of the oldest and most promising approach to fusion energy which is magnetic confinement. The theory says that it is only a matter of ionizing an appropriate mix of light isotopes, confining the mixture in a magnetic field and then heating it to millions of degrees while compressing it to densities only found in the heart of stars. The isotope mixture will then start fusing light elements to heavier nuclei and producing huge amounts of energy.
It turns out that as simple as the theory sounds, the practical development and implementation of hardware which can reproduce the conditions in the interior of starts that drive stellar fusion has proven to be out of reach so far.
Please read Part 3 next