If you want to become an astronaut, it's probably a good idea to become a scientist first. You also need to be interested in lots of things, including for instance outdoor activities. The other day NASA published video interviews with the four women and four men currently in training to become astronauts. If they didn't start their careers in the military, they did so in science, like Jessica Meir.
Striking about this group of eight is that half of them are women. If you look at the other 20 groups that NASA trained to become astronauts, you will find that men have always been a large majority. Most European astronauts are men, too. So it's interesting to note that some change is going on, at least in the USA.
In the sixties all or almost all astronauts were former military pilots. These days, considering what astronauts do in space, a scientific background is more useful than one as a pilot. Moreover, the videos show that if you get hired as a a future astronaut, they will teach you how to fly a plane. It's probably a lot easier to teach a scientist how to fly than to teach a fighter pilot to be a scientist on the side.
Watching the videos you will also find that you don't become an astronaut right after highschool. Even if you were certain as a kid that you wanted to be one. There is no Astronaut School to go to. You will have build a different career first - although you can build it in such a way that it supports your long term ambition. Physics, engineering but also medical sciences, biology and geology are good building blocks. And then when your local space agency starts hiring you can send in your application and hope for the best. Last time NASA did this was in 2012 (and they picked 8 out of more than 6000), and ESA in 2009.
Finally, space agencies aren't interested in one trick ponies. The lucky ones in the videos below are real collectors of degrees and other abilities, like diving or surviving in extreme cold. And it looks and sounds like they do all of it because they love it. If you think getting a degree or learning Russian is a price you have to pay for your ticket to space, they'll probably find you out and turn you down. You need to love it.
Herbert Blankesteijn is a technology journalist from the Netherlands who has written for many prominent Dutch newspapers. He presented and directed television and radio programmes and has 10 books to his name. Herbert is interested in nascent fields such as 3D printing, drones, robotics and the private space business.