Fusion reactor
From Halopedia, the Halo wiki
A deuterium fusion core is a species of nuclear fusion reactor used as a power source on UNSC frigates. Though not explicitly stated, it may also be used to power other kinds of spacecraft, and may be related to the oft-seen fusion core.
Based on the name, a deuterium fusion core probably combines deuterium nuclei (a light hydrogen isotope) into heavier elements, accompanied by a net gain of energy. Deuterium may be fused with itself, or with tritium, another hydrogen isotope.
Since they have not been seen on screen, it is not possible to meaningfully speculate on the technique a deuterium core uses to induce fusion. However, a UNSC frigate is a relatively small spacecraft and is powered by just two of these devices, so it could be deduced that they are not easily portable portable.
Real-world fusion reactors currently require more power than they release, so are not yet an economical means of electricity generation. Promising approaches include donut-shaped tokamaks, Polywells and laser-driven inertial confinement fusion (ICF).
