When should we leave for the stars? Or on the exponential speed of travel speed increase

The speed of travel is increasing over time. While we might argue about the rate at which speed is increasing, this long term observation is consistent with improving transportation technology. Suppose we model technological progress so that the speed of travel is increasing with a compound interest model V_t = V_{t-1}*\alpha Where \alpha > 1. (E.g. if speed were increasing at 1 percent...