Continuing interest of Space agencies and Militaries to exploit Zero-Point Energy for applications like propulsion and for generating electric power.

Zero-point energy is the energy that remains when all other energy is removed from a system. Zero-point energy  is the lowest energy that a given quantum mechanical system can have (i.e., the ground state of the system). In quantum field theory, it refers to the energy of the vacuum (i.e., a space devoid of matter [the energy of “nothing”]).