Chapter 2: Why Fusion Requires Extreme Temperatures

Fusion sounds simple in theory. Scientists take lightweight atoms, such as isotopes of hydrogen, and force them to combine. When this happens, a small amount of mass is converted directly into energy according to Einstein’s famous equation, E = mc².

In reality, achieving fusion is incredibly difficult.

Atomic nuclei naturally repel one another because they carry positive electrical charges. To overcome this repulsion, researchers must heat fuel to temperatures so extreme that matter enters a fourth state known as plasma.

At 100 million degrees Celsius, electrons separate from atomic nuclei, creating a highly energized mixture that behaves differently from solids, liquids, or gases.

Containing such material presents a major engineering challenge. No physical container can survive direct contact with plasma this hot. Instead, powerful magnetic fields act like invisible walls, suspending the plasma away from reactor surfaces.

The longer scientists can maintain stable plasma conditions, the closer they move toward practical fusion power. Stability has historically been one of the largest obstacles because plasma tends to become turbulent and difficult to control.

KSTAR’s recent achievement demonstrates significant progress in solving this problem.