one of spacex's goals is to make us a multiplanetary species, with the knowledge and technology we have now that means propulsive is the only way to do it mus

one of spacex's goals is to make us a multiplanetary species, 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 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 https://www.youtube.com/watch?v=SOpmaLY9XdI#t=30m22s