Space is nearly a perfect vacuum; beyond Earth’s atmosphere there is no air to produce lift or drag. Gravity is the main force to be dealt with in space, and thrust is the force that allows a spacecraft to get into space and maneuver.
A spacecraft in orbit is not beyond the reach of Earth’s gravity. In fact, gravity is what holds it in orbit—without gravity, the spacecraft would fly off in a straight path. As the spacecraft orbits, it is actually falling, though it never reaches the ground.
The faster an object travels, the more horizontal distance it covers as it falls, and the gentler the curve of its path. An orbiting spacecraft travels so fast that the curve of its path matches the curve of the Earth. So, the distance between the spacecraft and the Earth stays constant.
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An object in orbit is constantly falling, and falling is what causes “weightlessness.” Gravity acts on you even while you are in orbit, and therefore you still have weight. But what is missing is the familiar sensation of weight. Without air resistance, all objects fall at the same rate. Because you and your spacecraft are falling at the same rate, there is no force between you and it to provide a sensation of weight. You feel “weightless.”
