PLASMA ROCKET BREAKTHROUGH!

A 10- to 20-megawatt VASIMR engine could propel human missions to Mars in just 39 days, whereas conventional rockets would take six months or more. The shorter the trip, the less time astronauts would be exposed to space radiation, which is a significant hurdle for Mars missions. VASIMR could also be adapted to handle the high payloads of robotic missions, though at slower speeds than lighter human missions.

from the wiki:
The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electro-magnetic thruster for spacecraft propulsion. It uses radio waves to ionize and heat a propellant and magnetic fields to accelerate the resulting plasma to generate thrust. It is one of several types of spacecraft electric propulsion systems.

The method of heating plasma used in VASIMR was originally developed as a result of research into nuclear fusion. VASIMR is intended to bridge the gap between high-thrust, low-specific impulse propulsion systems and low-thrust, high-specific impulse systems. VASIMR is capable of functioning in either mode. Costa Rican scientist and former astronaut Franklin Chang-Diaz created the VASIMR concept and has been working on its development since 1977.[1] Tweet