What is Patreon? Patreon is "steady trickle" style of crowdfunding. Patrons pledge a certain amount per piece of content, or per month, and the creator creates them. It gives you a chance to help fund the game developers and writers you appreciate. The contributions are collected at the end of the month, and are typically in the $5 to $30 range.
In the case of Ad Astra, Patreon allows Ken to spend less time on business writing and freelance marketing copy, and more time on creating spaceships for Squadron Strike and Attack Vector.
Even more to the point, content put up on Patreon stays there - the longer the Patreon runs, the more stuff there is to play with. Ad Astra uses Patreon as a way to distribute play test drafts of products and ships, and the initial use of Patreon was to pay Ken for all the work he puts in on maintaining the Squadron Strike ship design spreadsheet.