There exists nothing, even theoretically that you can put on the spaceship to get you that 1G continuous acceleration.
I don't remember exactly what is the maximum achievable delta V but if I remember well it is not a high portion of the speed of light, more like 60% of speed of light. And that assuming you have crazy things like carry a small black hole with you and use it to convert mass into energy at 40% efficiency.
There exists nothing, even theoretically that you can put on the spaceship to get you that 1G continuous acceleration.
I don't remember exactly what is the maximum achievable delta V but if I remember well it is not a high portion of the speed of light, more like 60% of speed of light. And that assuming you have crazy things like carry a small black hole with you and use it to convert mass into energy at 40% efficiency.