A spherical capsule filled
with hydrogen fuel is bombarded with energy, compressing
and heating a small region in the center of the fuel.
fusion reactions from this central “hot spot” deposit enough energy
in the rest of the fuel that fusion occurs there too–this process
is referred to as ignition.
Note that during the very short period of
ignition (a few nanoseconds, or a billionth of a second) the fuel is pushed
inward, so its own inertia acts
to impede its disassembly; hence the term inertial