ok, so in which dimensions is the jump happening? when you say ‘wherever they are facing’ what do you mean? Where does the character face? Up/down, left/right? both?
That’s what I meant earlier, still a bit too little information.
But it’s ok, I think I get it. Why can you not use the forward vector? It is a unity vector and determines direction a character is facing. That’s exactly what you need. Multiply it by the new velocity vector you are trying to apply just before for the launch.