FYI, there are others on the forums that know more about rocket science then I do. However, why build a spacecraft that travels at Mach 1.0? You would never be able to escape Earth's surface gravity and space probes today like New Horizons traveled at 16 km/s or Mach 47 on its way out to Pluto. I calculated using standard atmosphere and temperature of 15C for Mach 1.0 velocity.