won the race, and by the summer of 1957 it was producing bursts of neutrons on every run. Despite the researchers' reservations, their results were released with great fanfare as the first successful step on the path to commercial fusion energy. However, further study soon demonstrated that the measurements were misleading, and none of the machines were near fusion levels. Interest in pinch devices faded, although ZETA and its cousin Sceptre served for many years as experimental devices. Fusion-based propulsion A concept of Z-pinch fusion propulsion system was developed through collaboration between NASA and private companies. The energy released by the Z-pinch effect would accelerate lithium propellant to a high speed, resulting in a specific impulse value of 19400 s and thrust of 38 kN. A magnetic nozzle would be required to convert the released energy into a useful impulse. This propulsion method could potentially reduce interplanetary travel times. For example, a mission to Mars would take about 35 days one-way with a total burn time of 20 days and a burned propellant mass of 350 tonnes. Tokamak Although it remained relatively unknown for years, Soviet scientists used the pinch concept to develop the tokamak device. Unlike the stabilized pinch devices in the US and UK, the tokamak used considerably more energy in the stabilizing magnets, and much less in the plasma current. This reduced the instabilities due to the large currents in the plasma, and led to great improvements in stability. The results were so dramatic that other researchers were skeptical when they were first announced in 1968. Members of the still-operational ZETA team were called in to verify the results. The tokamak became the most studied approach to controlled fusion. Sheared-flow stabilized Sheared-flow stabilizing uses one or more high speed annular flowing plasma sheaths, surrounding a plasma filament, to stabilize the filament against kink and pinch instabilities. In 2018, a sheared-flow stabilized Z-pinch demonstrated neutron generation. It was built by a fusion company, Zap Energy, Inc., a spin-out from the University of Washington, and funded by strategic and financial investors and grants from the Advanced Research Projects Agency – Energy (ARPA–E). Flow stabilized plasma remained stable 5,000 times longer than a static plasma. A mix of 20% deuterium and 80% hydrogen by pressure, produced neutron emissions lasting approximately 5 μs with pinch currents of approximately 200 kA during an approximately 16 μs period of plasma quiescence. Average neutron