Lateral and vertical acceleration

moveY = myTransform.up * Input.GetAxisRaw("Jump");
moveZ = myTransform.forward * Input.GetAxisRaw("Vertical");
m_body.AddForce((moveY + moveZ) * thrustPower);
// Use (moveY + moveZ).normalized if you want to always have the same thrust force.
// I prefer the style of having a higher thrust force when using both movement keys.