I don't think that's accurate. 42 km/s is purely a function of the Sun's mass and the distance of Earth's orbit. If we used the Earth's orbital speed (~30 km/s

I don't think that's accurate. 42 km/s is purely a function of the Sun's mass and the distance of Earth's orbit. If we used the Earth's orbital speed (~30 km/s) and launched from Earth in that continued direction we would only need ~12 km/s additional velocity.