I'm looking at this Stirling engine, which I believe is a variation of an alpha type. It was developed by Nasa back in the 1980's. The thing is, I can't figure out how the hydrogen cycles through the pistons. Could someone help me? This is another link that might help you understand what it looks like if you scroll down about 3 quarters. There are several pictures on this page. I've tried making sense of it but I don't understand how the heated hydrogen cycles.