You're right to think about the risks porn could pose to your career before doing it. And if you want to keep your military options open, you should absolutely look into what the code of conduct says about it.
But it's also worth putting the stories you hear about porn ruining people's careers in perspective. You never hear about the people whose porn careers didn't
bite them in the ass, because they're getting on with their lives. So that skews your view of the aggregate of people's experiences.
I escorted from 2001 to 2004 and did a little porn -- one studio production and some amateur Internet video. I was on the DVD cover with Michael Brandon, a huge porn star (though we weren't in a scene together other than B-roll footage), and the video was nominated for a Gay VN Award, and I do know of at least one person who stumbled across it on the Internet.
Before coming out about my colorful past in November and resuming escorting a few weeks later, I was "retired" for seven-and-a-half years and worked my way into a career that required me to be a semi-public figure who got photographed at lots of high-profile events in my city (Houston). (I was the art critic and a society reporter at the Houston Chronicle, the last daily newspaper standing in the city.)
I was always waiting for the other shoe to drop, but it never did, even though I knew for a fact there were pictures and video "out there," including at least one muscle worship video on YouTube that a client shot in the pre-YouTube era.
Now, I came out as part of an ongoing performance artwork that's kind of complicated and doesn't really apply to your situation -- for starters, I deliberately gave the paper ample grounds to fire me, which it did, and went on a 10,000-mile road trip -- but here's what might:
After I got back to Houston, the publisher of a new arts magazine hired me as visual arts editor after being overwhelmed with calls and emails telling him he should hire me. This support came both from prominent people in the art community who either didn't give a shit or thought it was cool and -- crucially -- from people who weren't really comfortable with it but whose respect I had earned sufficiently that they were eager to have me back covering the art scene.
Now, obviously, the military and the art world are two very different places. But even discounting for that, I think it suggests that, in my city at least, sex workers may be more or less where gays were not so long ago, when sodomy was illegal but people were starting to say, "I don't agree with it, but it's his business and he does a good job, so let him be."
I can't know how things would play out with you -- whether you'd be outed in the first place; whether hiding your past would start to wear on you, as it did on me; whether you'd be in a place where you'd sufficiently proven yourself to the people who mattered to give you a shot.
But if you do porn or any other form of sex work, always keep at the forefront of your mind how you're going to transition out of it. Use it to subsidize the skills that will help you make that transition and possibly win you the crucial allies you need. (You'll also be better off, and a better person, during your sex-work career. The most fucked-up sex workers I've met were the ones who didn't have anything else going on.)
You might want to see if there are companies that will let you do scenes masked -- though I wonder if it's less money -- a-la the Muscle Mafia (http://www.themusclemafia.com/
). Also, when I was first considering whether to do porn I got the studio that was interested in me to let me work on the crew of a shoot to see what it was like and get a sense of what the experience might be like. You might want to consider doing that before taking the plunge. Good luck whatever you decide.