Next-gen journeys and deep-space robotic missions out of the solar system will require next-gen engines, but vague and unproven concepts like the perpetual motion machine, zero-point energy and cold fusion engines won't get us very far. Cue solar electric rockets, the most efficient and cost-effective form of propulsion discovered so far. Nasa's Solar Electric Propulsion (SEP) project uses just a tenth of the chemical propellants traditionally used by spacecraft. It has two versions of radiation-proof fold-out or 'flexible blanket' solar panels, and wants them tested in a low-Earth orbit by 2020.
Not enough? You wanted a WARP drive capable of light speed? Tough – Nasa calls it 'simply imaginary', although there is currently some chat about the physics-defying EM Drive, which uses a cavity filled with resonating microwaves to create propulsion without emissions. If it can get us to our neighbouring Alpha Centauri star system 4.3 lights years distant – some suggest it could – who cares it breaks the basic law of conservation of momentum?