Have you ever heard someone call space “the final frontier”? That phrase became popular because of the science fiction TV show Star Trek. A frontier is a wild place no one has explored yet. During the years astronauts like John Glenn climbed into their rockets, people thought of space like that. They thought of the golden-age astronauts as pioneers.

Just like pioneers in early America, the first travelers to outer space needed courage and determination. They had studied space. But they couldn’t know what it was really like until they launched out of Earth’s cozy atmosphere. Some of the first astronauts traveled huge distances—much farther than astronauts travel today. Think about the first trips people took to the moon. To get there, they had to travel 235,000 miles. A car trip of that distance would take almost half a year—without stops. Imagine staying in the backseat for that long! (Are we there yet?!)

But today, astronauts no longer visit places like the moon. Instead, they take rockets to the International Space Station. The International Space Station (ISS) is a floating laboratory where scientists do research. It is just 249 miles above Earth’s surface. By car, a trip of that distance would take only four hours!

Astronauts on the ISS come from the United States, Russia, Japan, Canada, and Europe. Three to six people stay on board the ISS at a time. Their missions usually last about six months. The astronauts do important work. But they aren’t like pioneers. They are more like routine travelers. During the golden age of astronauts, the whole world watched while the people in space suits answered questions like, “Can man walk on the moon? Can man orbit the Earth?” Those astronauts didn’t just do missions. They were missions.