What are some of the problems that needed to be overcome in order for nasa to be able to land men on the moon and return them safely?

There are a host of engineering problems that must be faced in order to safely transit astronauts to and from the moon. Key challenges include:

1. Takeoff
Generating enough force to escape Earth's gravity requires enormous energy.

2. Propulsion
Ensuring enough fuel is available to return to Earth.

3. Artificial Environment
Creating an artificial life support system for the occupants of the ship. This must supply oxygen, filter out surplus carbon dioxide, provide heating, radiation shielding and a perfect seal to protect the occupants from the cold vacuum of space.

4. Food and water
Ensuring enough supplies are packed to keep all the occupants alive during the multi-day trip.