Any advice for writing hard scifi without knowing anything about scifi?

Im actually curious about this. I want to at least write a scifi book and incorporate some fantasy stuff like what if elves and other fantasy races who discover space travel and build ships that can travel into space to discover galaxies? Since I do not know anything about aerodynamics or anything that would help write a hard sci-fi novel. Can it be possible to write a sci-fi novel and just try to write something i dont know and somehow it can work?