The scientists who travel in spacecrafts are called astronauts (or cosmonauts in Russia). While astronauts are primarily trained in engineering, science, and piloting, they often have a background in scientific research as well. They conduct experiments and gather data during their missions, contributing directly to scientific advancement.

Here's a breakdown:

* Astronauts/Cosmonauts: These are the primary space travelers. They undergo rigorous training in various fields, including engineering, physics, medicine, and biology, to operate the spacecraft and conduct research.

* Astrophysicists: Study the universe and its celestial objects, sometimes contributing to research projects conducted on space missions.

* Geologists: Study the Earth's structure, composition, and processes. They might be involved in analyzing data collected by satellites or studying the geology of celestial bodies during space missions.

* Biologists: Study living organisms. They might conduct experiments related to the effects of space travel on biological systems or search for evidence of life on other planets.

It's important to remember that many scientists work indirectly with space missions, analyzing data and developing technologies from Earth. However, astronauts are the ones directly conducting experiments and gathering data in space.