Is there a way to **decelerate** significantly without an "eyeballs-out" sensation?
If you need to have an average speed of Mach 3, then cruise at a speed higher than Mach 3 and land at Mach 0.2. And decelerate at a comfortable rate.  

Or fly in a cryogenic wind tunnel to get the speed of sound down so much that Mach 3 is actual a very low speed.