Michael Nordine author “Indie sci-fi thriller” aren’t words we get to say often enough, even if the reason why is obvious: Making aliens, rocket ships, and the cold vacuum of space look real is expensive. Tribeca Film Festival offering “I.S.S.” avoids that issue by taking place entirely aboard the International Space Station, which becomes the staging ground for a proxy war when a nuclear conflict breaks out between America and Russia. That premise wouldn’t have been out of place in a collection of short stories by Ray Bradbury, and “Our Friend” director Gabriela Cowperthwaite, working from a Black List script by Nick Shafir, comes close to maximizing its potential with help from a stellar ensemble led by Ariana DeBose and Chris Messina.