The density of silicon is 2.33 g/cm^3, or 2.33 metric tons per cubic
meter. A thrust of 8.3 metric tons per cubic meter then readily
permits building a craft capable of sustained acceleration above 1 g,
or 9.8 m/s^2. Even without doppler shifting of the zero point field,
this will result in exceeding light speed in c/g = 3x10^7 seconds,
or about 355 days, one year. However, the zero point field will
likely be blue shifted, thus increasing its energy density and thus
the thruster performance.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/