This calculation is not mine, but Derpaholic's, as always.
v0 = rg/sin20
Range = 2,300,000 Meters
Gravity = 9.8 M/S^2
Angle = 13.4 Degrees .
sqrt ( (Distance * Gravity) / sin (2*angle)) = sqrt ( (2300000*9.8) / sin (2*13.4)) = 7070.45975424530957 m/s Or mach 20.7777477
I guess that makes everyone pre Piccolo/Goku mach 20+ .