100 years if probably too optimistic. 200 years probably isn't. Don't forget our technological progress has been exponential. We've had more progress in the pas

100 years if probably too optimistic. 200 years probably isn't. Don't forget our technological progress has been exponential. We've had more progress in the past 100 years than in the entire human history. We're also supposed to create the "singularity" this century, which will give us orders and orders of magnitude higher intelligence than what we have today. Hopefully we can use that intelligence to create those engines.