Yes, you could go to a military prison, if you say yes and the answer is no, and you get into the military. After your entry if the answer is found to be false, you could be sent to a military prison. The truth is that you would most likely be discharged under less than honorable conditions and sent back home. So, the answer is maybe. Yes, the MEPS folks will say you could be sent to a military prison and be totally truthful, but it isn't likely. The US military doesn't have the $$ to keep you in prison (clothing, food, shelter, and manning to guard you), vs. sending you home.