If Challenger sells well then I plan to have 2 or 3 other expansions. One will be surveyor and one will be a remake of the demo first man on Mars kinda thing. The Demo, Surveyor, Challenger, and Mars_1 were all supposed to be an incremental release but I had to concentrate on one of them. Kinda like Star Wars started on chapter 4. Challenger seemed to be the easiest attainable goal so thats what gets released first..