Project X (1987)

Matthew Broderick works as a scientist, or for scientists, or as some kind of outside reviewer checking up on scientists, and he begins to think that there's something morally problematic about what's going on with the monkeys in the scientists' monkey-torture pen. One of the monkeys smokes cigarettes (which I suppose at the time was just unambiguously adorable), so when that monkey saves the world from a major radiation disaster at the expense of his own life, it's his asking for cigarettes through a special glass window that makes everybody cry. Give him his cigarettes! He's dying, and all he wants is a cigarette! The real tragedy is that Matthew Broderick can't give the monkey a cigarette.

The end of Project X is indistinguishable from the end of The Wrath of Khan.

Were they training them to be astronauts or something?