The forces of gravity between two objects are inversely proportional to
the square of the distance between them. So reducing the distance
by 1/2 means increasing the gravitational force by 2² = 4 times.
The 1 million newtons becomes 4 million newtons.
Note that this does NOT mean the satellite's altitude above the surface.
When you're calculating gravitational forces, it's the distance between
the centers of the objects. So the question is a meaningful exercise
only if we use the distance between the satellite and the planet's center.
