The whole premise of Intersteller is wacko. That we would need to leave the Solar System is faulty logic. NASA in 2005 proclaimed there is enough material in the Asteroid Belt to create habitat to equal 30,000 earths(that's 30,000 X 58 million sq mi(land mass)) and house hundreds of trillions of future humans in the Goldie Locks Zone. That ain't all! If we humans decide to use all the moons of Jupiter, Saturn and the other gas giants as well Pluto, Venus, Mercury, the Kuiper Belt, and the Oort Cloud and the gas of the gas giants, we could support millions of habitat big and small equal to 200,000 earths and more(think O'Neil Cylinder, Stanford Torus, up to McKendree Cylinders). This would support up to 1 and 1/2 quadrillion humans/cyborgs in the future. The only reason to leave the Solar System and start to branch out across the Milky Way would be fear of roving black holes, or stars. Other than roving black holes and stars we have a home in the Solar System for the next 2 billion years at the least. It is estimated that at the current rate of growth it will take 500 years to reach the first trillion humans/cyborgs. Let's say we spread to the nearest 10 solar systems. Those solar systems will not need habitable planets. We will manufacture habitat enough to house a quadrillion humans/cyborgs around each star. It will take thousands of years, but we have time.