For each person, "what happens then..." is different.
I would imagine (don't know, can only speculate based upon past experiences) that you're going to be asked to answer a bunch of questions: "When, where, WHY, how often" and others.
After you've completely come clean, and answered all questions, then USAFA will sit back and decide one of two things:
a. Young "kid" experimented; this is not uncommon, peer group pressure, etc...etc...no harm done, stopped and hasn't done it again.
b. Chronic user, lying to us bigger than life, high risk type.
In my ALO career, I have seen many candidates "fess up" about MJ experimentation. I have not seen one (of mine) that was prevented from attending the academy because of prior experimentation.
I do know an ALO that had a candidate denied admission because of past "experimentation." I called him just before I typed this to get it correct:
a. MJ experimentation...tried it in JrHS..."a couple of times" then again in HS, pretty much once/twice per year.
b. Tried coke "once, didn't like it."
c. Tried X "made me sick, not cool"
d. Liked Spice but since it's illegal in the military, stopped using it.
See a problem with all that?
Come clean, be open and honest...my OPINION is that you'll be fine.
Steve
USAFA ALO
USAFA '83