This gotta be one of the most interesting technical conversations that I have seen on HN!! Since you both seems to have a lot of knowledge about propulsion systems, I wanted to ask you about advice on how to get into the field. I am an aerospace undergrad graduating next year. I am thinking of going to grad school (undecided between masters or phd) and propulsion is one of the areas that I would like to work on.
Well, I'm not at all in the field -- armchair quarterbacking it is just an old hobby for me. But if you're in America, my advice would be: go to Space Access every April, and plan on spending your summers in Mojave. That's how most of the people I know have done it.
