with the knowledge and technology we have now that means propulsive is the only way to do it
musk says of the moon, "there's are no runways and no atmosphere"
https://www.youtube.com/watch?v=SOpmaLY9XdI#t=11m30s
why colonise other planets? musk says, "planetary redundancy, backing up the biosphere..there are some risks that are just extremely difficult to mitigate and some risks which we ultimately not be able to mitigate"
https://www.youtube.com/watch?v=SOpmaLY9XdI#t=30m22s