How does someone actually become an astronaut?

NASA’s page details some basic requirements, but says nothing about the selection process. Are there astronaut headhunters that try to recruit elite test pilots? Do you submit wannabe-astronaut resumes to NASA?

Say a kid REALLY wanted to become an astronaut from the time they were 12 or so. What could they do to have the best chances, short of paying the Russians for a private flight? Enlist in military flight positions? Become a scientist? Or is there some sort of more specialized astronaut career path?

For that information, the aspiring astronaut has to leave the young readers’ “for students” NASA webpages and boldly go where no casual googler has gone before—no, actually, where any casual googler could easily go if they were paying a little more attention.

Namely, by following the link at the bottom of the page you cited to arrive at actual specific information on how to become an astronaut.

There’s lots more info, but you can read all about it for yourself. Application procedures are discussed here, and you can also read the FAQ. Apparently, though, NASA is not currently accepting civilian applications for astronaut positions.

The way I heard it explained, in the early years NASA took top military pilots and tried to train them to do science. After a while, they found it worked better if they took top scientists and trained them to be pilots. That’s a somewhat humorous exaggeration, but there does seem to be a mix of background (science or aviation) among astronauts over the past couple of decades, moreso than in the Mercury/Apollo days.

A friend of mine wanted very much to be an astronaut. He holds a PhD in mechanical engineering (but is not a pilot), and he went through the process as far as he could. He made it through a few cuts until he was in the top 6% of his group, and then he got cut. They don’t tell you why they cut you (unless it’s for a serious health condition that needs medical attention), but in his case, all of the applicants who made the cut were substantially older than him (he was in his early 30’s at the time); it seemed likely that NASA just wanted their astronauts a little older, a little wiser, with more life experience under their belt. My friend talked about reapplying later, but I don’t know that he ever did.

If you want to be a payload specialist, then the key is to become a specialist in some payload or another, and then get that payload chosen to fly. One of my professors was an astronaut, and got in this way: He was a scientist at Lockheed at the time, and was one of the guys who had built some solar instrument or another. Their instrument was flying on the Shuttle. His boss came to his team and said that the bad news was, that meant they needed to send someone up to operate it. He had a different evaluation than his boss of the quality of this news, and volunteered.

They only accept applications every few years. I believe the last time they accepted astronaut applications was in 2011. There is a very long process for screening the applicants. The final selection for this Astronaut Group 21 was announced in June 2013.

Wow - 6372 applied; 8 made the cut. I don’t like those odds.

That’s even worse odds than winning the Green Beret!

What color Beret do they win?

I have a neighbor who’s son is an astronaut.

The process took a number of years and two attempts. The 1st one was a non accept, but they told him why and he filled those gaps in a couple years then applied the 2nd time and was accepted.

One of the most internally driven people I have had the opportunity to meet.

Never tell me the odds!

There are 3 kinds of astronauts:

  1. Astronaut-pilot. You’d have to be a pilot of course. You’d probably want to have at least a BS in some field of Engineering and a lot of hours in “high performance” aircraft (which is a long winded way to say supersonic which is another way to say military fighters) and you’d probably want to have been a test pilot. So, we’re talking Mercury and Gemini astronaut criteria. Okay, Armstrong was a civilian, but before that he was a Naval Aviator and test pilot. By some of the further selections, they relaxed the test pilot requirement and the Astronaut-scientists were what are now either mission specialists or project specialists.

B. Astronaut-mission specialist. You don’t have to be a pilot, but you probably need at least one MS in some field of Engineering. Maybe several. A D.Sc could help.

These two types would probably be employed by NASA for some time.

III. Astronaut-project specialist. You’d have to be an expert on some piece of equipment or project that’s taking place on a specific mission. Like Wolowitz on TBBT was. You’d be more of a hired gun for that one flight/mission and after you landed, debriefed, and wrote up your report, you’d go back to your day job. Maybe NASA would keep your name on a list.

He didn’t have to go through any application process - he just had to win a game of sabacc!

You forgot the fourth way: get elected to Congress and then hold the kind of juicy chairmanships or critical districts to “get invited” to fly on the Shuttle, as three Congresspeople did in the heady days before the Challenger disaster. Given the relatively few seats that will be available on the SLS I don’t expect that this will be offered in the foreseeable future, but if you can throw some more hundred million dollar no-interest loans or NASA/EELV development funds at SpaceX, Elon Musk will probably offer you a free seat in a crewed Dragon capsule if and when it starts flying.

Stranger

How are Cosmonauts selected? Or "háng tiān yuán for that matter.

Stranger, are you including John Glenn in that count? Because I think his case is a bit different, seeing as how his method of getting elected was to first be an astronaut.

I recall Jake Garn going up in 1985. John Glenn went up in 1998, but that was well after Challenger.

So who were the other two?

I assume Stranger was referring to Glenn, Garn, and then-Congressman Bill Nelson: Bill Nelson - Wikipedia