Humanity only ventured into space in the last few centuries, and Helios 2 is the best current effort, not a fundamental limit. Also, the real obstacles are not

Humanity only ventured into space in the last few centuries, and Helios 2 is the best current effort, not a fundamental limit. Also, the real obstacles are not physical speed limits, but the huge cost of getting materials into space. If we ever got enough material into space to provide a true, self-sustaining industry (i.e. non-terrestrial power and materials) then we'd see a space-building boom that could rapidly improve on space exploration. The earth is relatively close to the sun, better use of solar wind: both the light and the plasma might help accelerate without the high energy/fuel costs, see: https://en.wikipedia.org/wiki/Magnetic_sail https://en.wikipedia.org/wiki/Magnetic_sail