Would it melt before then? Interstellar space is extremely thin, on the order of 1 atom per cubic centimeter (estimates vary). But, as we learned when Voyager finally left the solar system a few years ago, it is hot as hell. More than 54,000 degrees F according to National Geographic:
The Voyagers didn't have today's ion engines. I don't know how much that gains us, though, as the main speed gain was by leeching momentum from planets' momenta, rather than from the hydrazine thrusters it carries
https://www.nationalgeographic.com/science/article/interstel...