I have grown increasingly to think that interstellar travel will be done by acceleration/decceleration superstructures; moon sized railgun loops like particle accelerators except for spacecraft. Some form of Von Neumann machinery will be required to construct and maintain these.

This kind of system is the only way to:

1. Escape the tyranny of the rocket equation and

2. Harness the power of solar energy for transportation to its fullest

I wrote a draft proposal about this if anyone is interested!