Your challenge is to set your story in the past and feature a plot complication that would be trivial to solve in the present. Maybe your characters need to cut Grampa's rotten tooth out without killing him. Perhaps your female lead needs to talk to a strange man without the consent of her husband. Or, maybe your marooned crew wonders what to do when their portable force fields start acting up on a strange planet and they have to make due with pressure suits. Have fun!
On January 14th, it'll be gmork7's turn.