A fascinating article at New Scientist on a new nuclear powered ion drive called VASIMR that could transport astronauts to Mars in as little as 39 days:
VASIMR works something like a steam engine, with the first stage performing a duty analogous to boiling water to create steam. The radio frequency generator heats a gas of argon atoms until electrons “boil” off, creating plasma. This stage was tested for the first time on 2 July at Ad Astra’s headquarters in Webster, Texas
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Thanks to the radio frequency generator, VASIMR can reach power levels a hundred times as high as other engines, which simply accelerate their plasma by sending it through a series of metal grids with different voltages. In that setup, ions colliding with the grid tend to erode it, limiting the power and lifetime of the rocket. VASIMR’s radio frequency generator gets around that problem by never coming into contact with the ions.
Hitherto most plans to get to Mars involve lengthy journey times, during which exposure to cosmic rays and extended periods of weightlessness (ameliorated somewhat by centrifugal artificial gravity) could have a debilitating effect on the adventurers.
The creation of these powerful ion drives is an exciting and interesting development. Certainly I hope to see someone get to Mars within my lifetime. I wonder what technique will be used?