Unlike many venture capitalists, Katie Rae is a fan of startups that take on big and complicated problems. : Venture capitalist Katie Rae is trying to prove that “tough tech” is worth the tough work. The Engine, the $200 million fund she leads, invests in startups whose products require years of research and development before they’re ready. In short, they’re startups that many other venture capitalists avoid—like one firm that’s pursuing a viable form of fusion energy—because they require more time to get o the ground than the typical photo app and more time to pay off, if ever.