0h26m18s03f Andy Weir - Ion Engines are Real Technology - Not Invented for The Matrian - TR2016a
Channel: Thorium Remix
Date: 2017-04-22

http://ThoriumRemix.com/ Ion engines are a real technology. They're not just invented for the book. Basically they're particle accelerators that shoot particles very, very fast. So fast, that the particles gain relativistic mass.
Oh, wow.
So with less matter you're getting more momentum change. So you need very, very little mass. All the technology in the book actually exists. However, some of it is better than our current incarnation. So we don't have ion engines anywhere as powerful as Hermes has. But there's nothing preventing us from making it. We know how to do that. We could scale it up.

And everything you do in space, because you don't have any ground or air or anything to push against, it all comes down to delta-v. To put yourself on a Mars intercept you need a delta-v of about 2.5 km/s which is about 5,000 MPH. You can't cheat the system in any way. Physics demands that you pay the price. And the amount of fuel that you have on your ship determines the total amount of delta-v you can have. Period.

And you need a lot of energy on board so you need a reactor on board, which my fictional ship has.

Interview footage from "The Talking Room" with Adam Savage. https://youtu.be/5SemyzKgaUU