Awesome congrats! Although I'd highly reconsider going in with no specified MOS. From what I've gathered, those who do that typically get the crap jobs that they need to fill. How'd you like to go into the military for 4 years, hoping to get some good free schooling, and then they assign you to be a Cook, or a Bus Driver?
The free schooling is awesome, and take advantage of it. Sign up for a job that you think you'd like to do, and get some good schooling out of it. I went into the Marines and was signed up for Avionics Repair/Technician. Got some real good school, and some real good On The Job experience, which really helped me get out and find decent paying jobs.
So if you want something to do with propulsion/space, well get signed up for it. If you leave it open, and they decide you're job is going to be cleaning rifles at the armory, that just seems like a waste to me.
Good luck though. The military is a great experience, you'll love it. Plus the AF has the hottest chicks usually too
