The "constant acceleration" (CS) vs. "spin the wheel" (SW) options have advantages and disadvantages. As I understand it the "wheel" for a spin gravity-substitute would have to be about a kilometer across? But would use less fuel. The CS doesn't need a big wheel but you'd need a Bussard ramjet to provide fuel? So, anything better? I'd like to limit the serious suggestions to things that can actually be done within the laws of physics. The non-serious suggestions should at least be funny.