While it's touched down in alpha form, you can read our Kerbal Space Program review to see if it's worth your buck.
The makers of Kerbal Space Program (easily the best build-your-own-rocket simulator available) drew criticism from their fans when they announced that post-launch expansions would not be released freely to alpha customers.
Early backers of the game were told that buying now would mean they wouldn’t “have to pay for further updates". So when lead designer Felipe Falanghe mentioned an idea for a post-release expansion that players would need to pay for, well, it angered more than a few folk.
He’s now clarified the company’s position.
In a blog post, Falanghe said “I had a growing concern that development was starting to turn away from the course we had planned for it [...] In our efforts to make the best we can on every area of the game, we were starting to get stuck on very advanced areas of the game, while other areas were (and still are) vastly underdeveloped. Specifically, I saw that we were putting a huge amount of time and effort into resources processing in flight and such, and neglecting the mostly unstarted Career mode section of the game.
“It was with these things in mind that I mentioned in Monday's dev live stream that I thought it could be cool if those very advanced features we were getting ourselves into were available on an expansion to KSP, so that the stock game would fit it's intended scope, and these advanced features would still be available to advanced players. That, however, struck a wrong chord across our audience, and several heated discussions started to spread like wildfire.”
Falanghe goes on to clarify that when he spoke of this during the live stream they were his own “personal ideas, and those were meant in no way as any sort of official announcement on behalf of Squad. It was just me basically thinking out loud. There are no official plans for any sort of post-release project for KSP at this time.“
So, the company has no firm plans for releasing an expansion pack with features they’re working on for the current game. Though the idea of a pre-release version of Kerbal and a post-release version of Kerbal does seem to be in mind. What this will mean for alpha players isn’t clear but it seems to be that updates will continue pass 1.0 as free tweaks to the game. Though, after release the makers may begin building big content release which will be sold as add-ons.