DS is OS AS300 at Purdue and in Aero/Astro Engineering. Didn't decide on AFROTC until sophomore year, but eventually got a 3 yr scholarship. As previous posters eluded to, Purdue engineering can be hard to get into and harder to get out of... particularly with the specific discipline you want (Aero/Astro, Civil, Electrical, Industrial, etc.). Once accepted, you are in the First Year Engineering (FYE) program with every other engineering candidate. Check out the basics here: https://engineering.purdue.edu/ENE/Academics/FirstYear
. Depending on how well you do after completing FYE plan of study, you apply for and are accepted into the specific discipline program... each with different minimum GPA and other requirements (a minimum 3.2 GPA gives you top priority for selection if there's capacity available in your program). Check out the transition requirements here: https://engineering.purdue.edu/ENE/Academics/FirstYear/T2M
For some, the secret to success is to not take all FYE courses in the first two semesters so they can better navigate the so-called "weed out" courses. Presumably, many AFROTC cadets in Aero/Astro Engineering are on the 5-year "super senior" pace for this reason. Good luck. Good school choice.