If you’re working on a novel design for a new power generation idea, it’s best not to post the blueprints online for other companies to steal, that is your intellectual property and the fruits of your labor.
However, it’s not in your best interest to never discuss the work with anyone until it’s completely done. The thought that someone is going to steal all of your work and start their own competition is a long shot. More likely though, is that you will find someone who can add to your work. It’s possible your true skill lies in engineering, while another person you are talking to has skills in sales and would love to sell your product. Or you end up sharing with an investor who wants to put in capital to help your idea grow. Or you meet another engineer who gives you a different direction to go on a couple subsystems and it revolutionizes your whole idea.
The point is the upside to sharing is more likely, and the downside is a long shot. A quote I heard was, “Competition begins at $100,000,000.” Until your company is highly capitalized or earning significant amounts of money, no one cares what you are working on, you are just one of the millions of other people trying to make something from nothing, there is no proof your idea is worth more than any other. However, once $100,000,000 is on the table, others will be taking notice anyway, and once you’re on the market competition will always show up.
Protect the details, but don’t hide the ideas, otherwise you’ll never find the help you need to be spectacular.