Okay, let's say I grant your two extremely optimistic assumptions. Then what? You can send a bunch of tiny sentient brains hurtling through the universe. They w

Okay, let's say I grant your two extremely optimistic assumptions. Then what? You can send a bunch of tiny sentient brains hurtling through the universe. They will have a very high chance of hitting interstellar dust and turning into a blob of plasma before they reach the target solar system. They also have no way at all to slow down once they reach the target system. Interstellar travel requires not just being able to accelerate to incredible speeds, but also to carry enough energy and reaction mass to slow down again to (essentially) zero.