Subject: Is faster than light motion impossible due to spacetime contraction?

If a massless particle were to be accelerated to a superluminal speed 
would Lorentz contraction provide for the impossibility? By this I mean 
that, according to Lorentz, the length of the particle along it's vector 
would be imaginary, and the time dilation would be it's reciprocal and 
therefore complex.  Does this come into play at all in the constancy of 
light speed?
Also if a fermion, hypothetically, were accelerated to such a velocity 
would it's relativistic mass become complex?(inv.mass/1-vsqrd/csqrd)What 
would this entail in regards to the constancy of light speed?I am asking 
due to an insatiable interest in physics, and would be happy to get a 
response that explains the use of imaginary numbers in physics and their 
relevance to the constancy of light speed.  Thanks for your time!

Re: Is faster than light motion impossible due to spacetime contraction?