We all know chemical propulsion isn't viable for our first Mars missions, too slow, too inefficient, and too primitive, so what propulsion system should we use?
NERVA? https://en.wikipedia.org/wiki/NERVA
Solar electric propulsion? https://www.nasa.gov/mission_pages/tdm/sep/index.html
VASIMR? https://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket
Or the Fusion Driven Rocket (The coolest one)? https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion#MSNW_Magneto-Inertial_Fusion_Driven_Rocket