Antimatter-Catalyzed Fusion
A tier-6 drive.
Antimatter Torch
A tier-6 drive.
Chemical (Hydrolox)
A tier-1 drive.
Daedalus Drive
A tier-5 drive.
Fusion Torch (D-D)
A tier-4 drive.
Gridded Ion
A tier-3 drive.
Methalox (ISRU)
A tier-1 drive.
Magnetoplasmadynamic
A tier-3 drive.
Nuclear Thermal
A tier-2 drive.
VASIMR (Variable Plasma)
A tier-3 drive.