Theronium
A nanofluid propellant of liquid hydrogen infused with antimatter-containing nanoparticles, the standard fuel for Impulse Boosters.
Theronium is what inhabitants would refer to as a nanofluid. Essentially, Theronium is liquid hydrogen with nanoparticles infused within the liquid.
These nanoparticles — known as EMTraps — contain antimatter particles suspended in an electromagnetic field. When ignited in the combustion chamber of an Impulse Booster, the hydrogen detonates and the EMTrap shielding evaporates, releasing Anti-Hydrogen for a secondary antimatter reaction that dramatically increases yield.
Even at only a few hundred grams of antimatter per tonne of fuel, Theronium provides the efficiency required for practical sub-light travel between planetary bodies.