I was fascinated to learn about dusty plasma fission fragment rockets. https://en.wikipedia.org/wiki/Fission-fragment_rocket There's talk that they might enable high delta-V exploration like a manned Jupiter mission! However, they need to be surrounded very many tons of neutron moderator material so the neutrons can cause a chain reaction. If you could save the mass of the neutron moderator, the thrust to mass ratio goes up, and the voyage times come down, as well as the cost of construction. Something said on another thread made me wonder if antimatter (positrons) could be fired at Thorium dusty plasma with similar effects? I found a report that large numbers of positrons were made by bombarding gold with electrons - https://www.llnl.gov/news/billions-particles-anti-matter-created-laboratory Could this work from a Particle Physics viewpoint?