Space science

Rockets, orbital mechanics, satellites, and interplanetary trajectories

What is space science?

Space science is the study and practice of spaceflight itself — how rockets work, how satellites and spacecraft stay in orbit, and how missions are designed to reach other planets and beyond. Where planetary science studies the planets themselves, space science studies the engineering and physics of actually getting there.

How rockets work

A rocket moves forward by expelling mass (hot exhaust gas) backward at high speed, and by Newton's third law (from the Mechanics article, every action has an equal and opposite reaction), this pushes the rocket forward. This is why rockets work in the vacuum of space, unlike airplanes, which need air to push against — a rocket only needs to push against its own expelled exhaust.

Staying in orbit

An object in orbit isn't defeating gravity — it's continuously falling toward Earth, but moving sideways fast enough that the curve of its fall matches the curve of Earth's surface, so it never actually gets closer. This is why astronauts aboard the International Space Station experience weightlessness: they, the station, and everything inside it are all falling together at the same rate, with nothing pushing back against that fall the way the ground does for us.

Satellites and their uses

Thousands of satellites orbit Earth today, serving a wide range of purposes: communication (relaying phone and internet signals), navigation (like the GPS system covered in the Relativity article), weather monitoring, and scientific research studying Earth and space itself.

Why space science matters

Space science has enabled satellite communication and navigation that much of modern life depends on daily, expanded our direct knowledge of the solar system through robotic missions that have visited every planet, and made human spaceflight and a continuously crewed space station a reality.