A 39-day Trip to Mars!

The current six month travel time to Mars is a problem that the Ad Astra Rocket Company is working to solve. Standard chemical rockets provide a very large initial propulsion, but exhaust their fuel during the initial thrust from the earth's surface. The rocket then travels through space reliant on the initial thrust provided by the chemical thrusters.

VASIMR Ion Rocket (http://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html?full=true#.VS8kLJMbDmY)

The new VASIMR (Variable Specific Impulse Magnetoplasma Rocket) is taking an entirely new approach. Rather than using a large initial thrust, this engine will provide continuous thrust for the duration of the journey. In lieu of using chemical fuel, the Ion engine accelerates ions through an electric field to propel the rocket through space. Although this push is considerably less than the chemical engine's thrust, it can be sustained for a much much longer time. After only a short period of continuous thrust, the rocket will meet and exceed the speeds generated by previous single thrust engines.

http://www.huffingtonpost.com/2015/04/06/vasimr-rocket-mars_n_7009118.html

One of the greatest challenges with these plasma rockets is generating enough power to use them over a sustained period of time on a trip. To address this, engineers are working to build on-board nuclear reactors that can provide the sustained energy needed. Currently, in testing that has been done with non-nuclear power supplies, the engine can only be sustained for approximately one minute. NASA, however, has partnered with Ad Astra Rocket Company to aid in funding and research to develop a prototype that lasts a minimum of 100 hours, over the next three years.