To get the best result, you need to run the simulation like if you actually threw the projectile - just fast forward! And that is quite easy in any Box2D port. In AndEngine call method
step(float timeStep, int velocityIterations, int positionIterations) from class
com.badlogic.gdx.physics.box2d.World in a loop to run it as fast as you want. You can apply arbitrary forces at the beginning or between each two steps.
Note that in AndEngine the
World class is wrapped in class
PhysicsWorld that doesn't give you direct access to the instance of
World. However you can extend
PhysicsWorld to get access to
protected fields, or you can simply call
onUpdate method. This one updates all AndEngine physics connectors as well.
Just be careful with the performance, play with the parameters. Maybe create a clone of your physics world that will be simplified, containing just the objects directly needed for the simulation.