scjurgen:
I don't think he got an impact time.
The first signal that triggers is then defined as t=0. The others are delta values (so called TDOA) to the first dtn=tn - t etc. So, when you put up your equation of the circles, your radii of 3 circles will have an unknown delta in common for which you have also to resolve (resolve for x,y, and r). BTW, this problem is actually called multilateration Trilateration - Wikipedia.
That is correct, i do not have the impact time, i only have the first trigger on sensor 0, which is already
and x distance from the impact point..
Also as to my initial line of thought, i do not have the incoming signal angle, which would help to solve the problem
with triangle formulas.. so the next option 
Thank you for the link, i will do some reading and see if i understand the principals of the multilateration