At first the problems of getting this energy on earth seemed insuperable, because of the millions of degrees of temperature required to get hydrogen atoms to combine. In the 1950s it was discovered how to do this in hydrogen bombs by using ordinary nuclear fission bombs to set off the fusion of the hydrogen isotopes of deuterium and tritium. Projects were promptly started for doing this under less violent conditions. After 40 years, fusion reactors may be close to getting more fusion energy out of the reaction that has to be put in. None of the projects is close to designing a plant.
Fusion power has the following possible advantages if it can be made to work.
The fuel supply is potentially larger. However, the uranium supply seems to be large enough. Fission products are not produced, although there will be induced radioactivity in the structures of the plants. No material useful for bombs is produced. There are many arguments, some related specifically to nuclear energy and others stemming from more general ideas about society.