I would like to share with you a crewed interstellar spacecraft which I have designed and called Solar One.
It employs a combination of 3 propulsion methods: nuclear fusion, beam-powered propulsion , and photon propulsion.
Basically, several compact fusion reactors power a laser system that propels a huge light sail.
Physicist Robert Forward already proposed in 1983 to use a 26-TW laser system to propel a 100-km light sail, a fresnel lens to focus the beam of the laser, and decelerate the spacecraft with a secondary light sail.
I propose something a bit different, which is to use to use for example a 60 TW-laser to propel a 5-km light sail that would deploy from the spacecraft after the acceleration stage, use parabolic mirrors that gradually change their orientation in order to focus the laser beam, and finally use a photon rocket to decelerate the spacecraft.
In theory, it could be possible to achieve 25% the speed of light, reaching the closest potentially habitable exoplanet in less than 20 years.
There are of course many challenges, like building high-energy continuous-wave lasers, reducing the weight of the nuclear fusion reactors (and of course achieving effective nuclear fusion first), and minimizing the effects of zero gravity during such a long trip.
What do you guys suggest to overcome these challenges?
This is my paper and a short video that summarizes all: