Let's hope that if we're clever enough to develop new propulsion technologies we'll also be clever enough to realize there's zero value in sending humans into space, especially for long dangerous missions that have few if any meaningful goals. Far better to save the weight, complexity, and pointlessness of human cargo and instead focus on AI/robotic missions. After all, we've learned infinitely more from the relatively small amounts we've spent on robotic exploration of our solar system than from all the hugely expensive and largely pointless missions shoving humans temporarily up and out of the Earth's gravity well. If only we could get past Sci-fi thinking, we'd learn so much more so much more rapidly.