Hello! I apologize for the confusion. You are correct that we cannot directly calculate the gravitational force on the spaceship without knowing the mass of the spaceship. The equation for gravitational force is F=(GmM)/r^2, where F is the force exerted by the planet, m is the mass of the spaceship, M is the mass of the planet, G is the gravitational constant, and r is the distance between the spaceship and the planet.
In this particular question, we are given that the gravitational pull is increasing at a rate of 1N/km as the spaceship approaches the planet. However, this information alone is insufficient to determine the gravitational force at a specific distance. We need to know the mass of the spaceship in order to calculate the force.
If you have any further questions or need more clarification, please let me know!