I've found SR-2 to be almost addicting to work with. I'm 67 and remember the race to the moon very well. I have designed Mercury, Gemini and Apollo spacecraft with SR-2 and have had a blast doing it. Right now, I'm working with shuttle type spacecraft. It's fun even if the thing crashes and burns. I wish I had known about this software when i was still teaching. I taught a 12th grade level Aerospace class before I retired. SR-2 would have been a great teaching tool. To the developers, I say well done, keep up the good work and thanks.