The initial technical goal is "more mass to orbit". Due to the rocket equation, the amount of fuel needed is ~20x the amount of payload to low earth orbit. Any

The initial technical goal is "more mass to orbit". Due to the rocket equation, the amount of fuel needed is ~20x the amount of payload to low earth orbit. Any fuel needed to get from low earth orbit to higher orbits needs to get to low orbit first, and so counts as mass. So the more mass and the greater a distance one wants to fly, the larger the required rocket. This rocket is very large. People and the necessary life support for people are quite massive compared to robots. Once one can get lots of mass to orbit, one can think about things like sending people past low earth orbit (around the moon, to the moon, or to Mars). So far, NASA has committed to sending people to the Moon, but no farther. Elon Musk says that the goal is Mars, but any craft which could be used to start a Mars colony also has the ability to start a much larger moon colony, or perhaps to land on the moon and take off again without leaving (expensive) parts of the rocket behind. There is some applied science research, such as around methods for reentry, but the final goal is establishing human colonies.