LENR emerging soon
What isn't widely known is that a new clean, very very cheap, and super abundant energy technology is emerging (Leonardo is selling a 1 megawatt LENR generator to a long wait list of customers starting this April - with a COP of about 6, the estimated cost to be about 1/10th that of fossil fuel, and a third-party verification is due to be published soon).
In other words, the electricity to fuel the fusion engine can be LENR, which has the fuel density of 5 orders of magnitude over fossil fuel. Hydrogen and nickle are common elements throughout the solar system. Here is a primer:
"A volume about the size of a #2 pencil eraser of water provides as much energy as two 48-gallon drums of gasoline. That is 355,000 times the amount of energy per volume – five orders of magnitude." ( http://oilprice.com/Energy/Energy-General/New-LENR-Machine-is-the-Best-Yet.html ).
This phenomenon (LENR) has been confirmed in hundreds of published scientific papers: http://lenr-canr.org/acrobat/RothwellJtallyofcol.pdf
"Over 2 decades with over 100 experiments worldwide indicate LENR is real, much greater than chemical..." --Dennis M. Bushnell, Chief Scientist, NASA Langley Research Center
"Total replacement of fossil fuels for everything but synthetic organic chemistry." --Dr. Joseph M. Zawodny, NASA
By the way, here is a survey of some of the companies that are bringing LENR to commercialization: http://www.cleantechblog.com/2011/08/the-new-breed-of-energy-catalyzers-ready-for-commercialization.html
For those who still aren't convinced, here is a paper I wrote that contains some pretty convincing evidence: http://coldfusionnow.org/the-evidence-for-lenr/