I was interested in this too as someone who's worked in web apps the last 8-10 years and was super inspired by the SpaceX Falcon Heavy landing (science fiction

I was interested in this too as someone who's worked in web apps the last 8-10 years and was super inspired by the SpaceX Falcon Heavy landing (science fiction is now science fact!) I looked into graduate programs, especially those online, and found the JHU Space Systems Engineering program. The prerequisites for THAT program are a year of college Calculus and a year of college Physics. I'm currently taking that, "year", which is really just Physics I and II and Calculus I and II at Thomas Edison State University. They've been doing distance learning for decades. The courses aren't super cheap, they're around $2,000 each, but having classmates, a mentor, deadlines, and a legit program to structure my learning around has been so helpful. Not to mention that my grades are legit for pre-reqs if I do want to go the full grad school route. I'm almost done with the I level courses and started the II level courses 2/3 of the way through the I. I think a lot of people on here might say my approach is kind of basic (I see people recommending working differential equations or something to start), but I've found it really enlightening to start from the very beginning and things are starting to get challenging as I get into the second level, especially with Calculus. Maybe if you just looked up Physics I and II and Calc I and II curriculums, and got the textbooks (Conceptual Physics by Paul G Hewitt and Calculus: Early Transcendentals by Robert Smith) you could do a lot of the same exercises. Hope that's helpful!