I am looking for the title of a short story about a one way delivery (courier) voyage of a young boy who will reach his destination an old man, too old to return. The small ship he navigates (solo) to the distant solar system? has huge solar sails that open out collecting energy from passing stars as its sole power source. The story only concerns itself with the beginning of the journey and the young boy's thoughts as he sets out.
It was published in Analog but I am not sure what year. I read this in the 1980s and have been thinking about it ever since.