deltaX = horizontal distance between source & target;
deltaY = vertical distance between source & target;
vMax = maximum launch speed (scalar);
g = (positive) downward acceleration due to gravity (eg. 9.8 m/s^s);
yMax = ceiling elevation - source elevation;

b1 = vMax^2 - deltaY * g;
discriminant = b1^2 - g^2 * (deltaX^2 + deltaY^2);
T_min = sqrt((b1 - sqrt(discriminant)) * 2 / g^2);

T_max = sqrt((b1 + sqrt(discriminant)) * 2 / g^2); // limit due to weapon power
b2 = g * (2 * yMax - deltaY);
T_max = min(T_max, sqrt((b2 + sqrt(b2^2 - (g^2 * deltaY^2)) * 2 / g^2)); // limit due to ceiling

T_lowEnergy = sqrt(sqrt((deltaX^2 + deltaY^2) * 4 / g^2));

launchVelocity.x = deltaX/T;
launchVelocity.y = deltaY/T + T * g/2;

p(t) = sourcePosition + t * launchVelocity + t^2 * gravityVector/2;
(where gravityVector = (0, -g) )