As others stated Character class is not set for simulating physics.
So if I understand you correctly,you want your character to be applied force whose magnitude is determined by where you stand on the terrain ?
I dont know about LaunchCharacter method but you can do the following,
Check if character is on the terrain,
check character’s height from the terrain (Character.Z - terrain.Z)
Divide by some scalar and
AddImpulse(DirectionOfYourForceVector*MagnitudeOfYourForceScalar,“”,true)
AddImpulse and AddForce methods are different.Try them in action.AddImpulse is used for momentary bursts like in explosions etc.AddForce is more likely used for things you want it over time.You have to give really big numbers in order to AddForce work because it involves gravity force too.
I’m not expert on this but AddForce(YourForceDeltaTime) works like
FinalForce = AllForcesActingOnBody + YourForceDeltaTime.