I completely missed this awesome answer to my NASA question from my favorite science blogger jtotheizzoe, but here it is!

NASA has been continuously recruiting astronauts since 1959, even before we flew into space. There’s no signs of this slowing, although the missions and skills are continuously changing.

Every few years, NASA picks a dozen or so “astronaut candidates” from thousands of applications submitted. Here’s 2009’s class. They are pilots, teachers, scientists, doctors, and engineers. Only 330 people have ever been selected as astronaut candidates since 1959. You have to hold a bachelor’s degree in a STEM discipline (and really an advanced degree with significant experience if you’re not a military pilot). You also have to pass a pretty rigorous physical examination (better get Lasik for those glasses, Jen), and be between 5’2” and 6’3” (I’m right at the top end, which is unfortunate for my future application). You also have to be a U.S. citizen (or dual citizen).

Then there’s about a bazillion interviews. If you get selected, you have to do survival training, SCUBA certification, and about 2-3 years of intense space systems and engineering training, you have to learn Russian, you learn to do robotics work while wearing a spacesuit. Then you can actually be selected as an astronaut.

But why? We don’t have space shuttles anymore. Well, the International Space Station mission will continue for the foreseeable future, using partner countries like Russia to launch our astronauts into space. NASA is still developing future manned vehicles for missions to an asteroid and later Mars, namely the Orion project. 

Because the astronaut training program is so long and intense, NASA must continuously be recruiting and training future space explorers. The cost of keeping a stable of ready-to-fly astronauts is paltry compared to building and maintaining the spacecraft and missions. Private companies are also getting into the space biz, but for the time being that looks to be the realm of pilots and adrenaline junkies. There’s future plans for private companies to dock with the ISS and do contract work for the government, but it doesn’t change one key fact: NASA trains the best astronauts in the world. And they are going to continue to do so.

Why? Because we have to get back up there. Start working on those applications!

Great info! Thanks!