It would only take ~50 years to reach Barnard's star with a theoretical fusion engine according to a research study named Project Daedalus. Someone shoot a probe at the planet and maybe our kids can see some cool imagery!
I think fission fragment rockets might be more promising. Doable with current tech, they can have exhaust velocities of a few percent the speed of light (specific impulse in the 6 figures), comparable or better than fusion engines.
The most realistic current proposal for an interstellar science mission is to avoid onboard propulsion altogether using a fleet of tiny laser-accelerated probes. Each one would be a very thin mirror, shot from orbit to the stars by a ground-based laser array. httpss://en.m.wikipedia.org/wiki/Breakthrough_Starshot
It's a fascinating idea but I'm not clear on how you would get back data? Modulation of reflected laser light? Active antennas that powerful radio telescopes are looking at?
You could also do it with existing nuclear fission technology (Project Orion). 3% speed of light seems to be quite feasible with that. If there‘d be no other way to save humanity, a generation ship with that technology would probably be built today.
Project Orion, the one that can hypothetically do 3% light speed, is definitely fusion as well. And the very high Isp versions of it are incredibly challenging to build (as you need like a magnetic shield to deflect the nuclear plasma ball). The more modest Isp versions are more realistic, but won't get you there.
I see, but still, at least the energy source itself would be proven technology in the form of H-bombs right? As for the shielding, do you mean the pusher plate or the nuclear shape charge in the bombs themselves? Does going from fission to fission+fusion bomb make such a big difference that couldn’t be overcome just with more/stronger material and/or ablative shields?
