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As usual the public press is clueless of how propulsion actually works.
"virtually unlimited fuel" says the L.A. times...lo.
No...Nuclear Thermal Rockets would have an exhaust velocity of up to 2.5 times that of a chemical system; not unlimited...but still very good. The Times also also say 'much higher thrust'. The thrust/weight ratio would actually be lower (slightly)...but for transfers from Leo to Mars and back this doesn't matter.
Also the L.A. Times fails to realize that speed isn't the only advantage...there is the advantage of cost. A nuclear transfer vehicle could be much smaller than a chemical based system, and would thus cost considerably less to develop and launch.
In addition to lightcraft, there are Microwave Electrothermal Thrusters (MET's). By heating the exhaust gases away from the thruster walls without the use of electrodes, they can achieve ISPs much greater than NERVA, with thrust densities much higher than ion grid or hall thrusters. An MET thruster that uses a large external microwave source beamed to the craft /might/ have sufficient thrust-to-weight for ground launch.
Here is a link to a detailed paper describing various types of electric propulsion:
http://www.aip.org/tip/INPHFA/vol-6/iss-5/p16.pdf
The above paper does not describe MET's much however; they are pretty new, technology-wise.
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