¶The quest for a fusion drive. As evidenced by… roughly speaking… every sci-fi series, fusion engines are the future of space propulsion. California startup Helicity Space is on a mission to develop such a drive today. Their approach is basically a deuterium-deuterium plasma thruster with a pulsed magneto-inertial fusion “afterburner” that compresses confined plasmoids in a double-helical magnetic system (a “plectoneme”… kind of like a helical z-pinch). While early versions of the Helicity Drive wouldn’t exceed the Lawson criterion (more energy out than in) and would require external (presumably solar) power, the energy added to the exhaust from fusion would increase the system’s exhaust velocity and ISP (giving somewhere in the neighborhood of 10,000 s isp, vs a maximum of ~400 for chemical rockets). The claim—which we’re somewhat skeptical of—is that this energy gain is easier to achieve than a sustained, contained, terrestrial fusion power system (recent presentation from their chief scientist). The required techniques of helical plasma jets (paper), magnetic reconnection heating (paper), and peristaltic magnetic compression (paper) have been demonstrated in the lab at varying scales. Notably, their all-star science and strategy advisory board includes Pete Worden, Air Force General and later Director of NASA's Ames Research Center, and Alan Stern, PI of the New Horizons mission to Pluto—here is Alan excitedly pitching the company and a proposed mission which would reach the interstellar medium in about 10 years. While this may not be the company that ultimately builds a fusion engine (it could be competitor Princeton Satellite Systems, a magnetic mirror approach like Realta Fusion’s, or something else), it does feel like humanity will build one eventually, and we’re glad engineers are seriously working on it today. They’ve raised about $5M based on aggressive timelines, so hopefully, we’ll know more soon. | 
