How about this instead.
You get a message. The message says "take the ISS by any means necessary." You assume that the other side got the same message. We can go a step further and assume that when they read their message they will also conclude what our orders are. Given these facts the American space scientists do...nothing? It doesn't make any sense. You would either act on your orders or you would reveal the contents. Keeping your cards close to your chest tells the other side you're going to try and take the station. Guess I'll go on a dangerous space mission and leave my fellow astronauts outnumbered and at a major testosterone deficit? This is all behind a backdrop of thermonuclear war where we the Earth is just on fire.
Undo that. Start from "war looks to be imminent." Both sides receive messages. Through the two halves we learn that the space station could be a critical asset in coordinating a first strike or impairing a counterattack. Both sides share this information with each other and because they're enlightened scientists everyone agrees the ISS will stay neutral. We then have a scene where one of the dudes takes out a little locked box. It's got a series of little envelopes in it. He takes out a little plastic stick, breaks it, extracts a decoder, reads it, selects an envelope, opens it, uses the decoder again and gets the message "take the space station all other directives rescinded." Now we only have a single character on one side that has special knowledge and we can try and build tension from there with the stakes being maybe your side wins the war and saves their country from annihilation. Now we have moral dilemmas. Maybe you want your country to win for national pride or maybe you're afraid that war will happen anyway and everyone will die. It has to be better if only one side gets incinerated, right? Why shouldn't that be the side my kids are on? Maybe one of the characters has old wounds from the Cold War. While these themes are being explored we're occasionally checking in on the one dude clearly preparing. When is he going to strike? Swerve, double swerve, double double swerve, downer ending everyone dies. By the end of the film there's one bloody astronaut, terminally wounded, looking out the view port waiting for Jesus to take them up to heaven on a white horse when the missiles just begin to fly.
