Because the spacecraft is in a state of free fall around Earth and due to the extremely low friction of the upper atmosphere, the spacecraft or a space-station and its contents are in a high-quality microgravity environment [ 2.
They experience weightlessness not because of a lack of gravity but because the ISS, and they, are orbiting Earth in constant free fall, says Valerie Neal, curator of space history at the National Air and Space Museum. They're falling toward Earth and moving forward at about the same velocity.
Inside the ISS, because people, objects, and everything are moving in the same direction and at the same speed, it's as if the earth's gravity is not at work. That's why the astronauts and other things are able to float about. This weightless environment is one of the biggest differences between the Earth and the ISS.
In space, astronauts do not walk on the floor like people on Earth do. They float around inside their spacecraft. That is because of microgravity. Microgravity is when things seem to be weightless.
However, there is another, more pertinent reason why we would not even try to have artificial gravity on the ISS. The purpose of the space station is not to let astronauts float around and play some zero-G pranks; it is a floating laboratory with the purpose of conducting experiments in low-gravity environments.
However, there are no current practical outer space applications of artificial gravity for humans due to concerns about the size and cost of a spacecraft necessary to produce a useful centripetal force comparable to the gravitational field strength on Earth (g).
Inside the ISS, there's a downward gravitational pull of about 0.89g, but the station itself is simultaneously accelerating downward at 0.89g -- because of the gravitational pull. Everyone and everything inside the station experiences the same gravity and acceleration, and the sum is close to zero.
Contrary to popular belief, there's no such thing as zero gravity. Weightlessness and zero gravity are two different things. The earth's gravity keeps the moon in orbit. And astronauts are generally much closer to earth than the moon is, which means that the earth's pull on them has to be much stronger.
Although you can jump very high on the moon, you'll be happy to know that there's no need to worry about jumping all the way off into space. In fact, you'd need to be going very fast – more than 2 kilometres per second – to escape from the moon's surface.
In space, astronauts and their spaceship still have mass and are still acted upon by Earth's gravity. In this sense, they still have weight, even though Earth's gravitational force is smaller in orbit than it is on Earth's surface (Box 1). However, they do not feel their weight because nothing is pushing back on them.
Absence of gravity is known as weightlessness. It is like floating, the feeling you get when a roller coaster suddenly goes down. Astronauts on the International Space Station are in free fall all the time.
Astronauts on the International Space Station feel weightless because they are in free fall around the Earth, experiencing no additional forces. This allows them to float and objects to appear weightless.
In contrast, the International Space Station (ISS) was designed for long-term spaceflight and has been in orbit since 1998. So how is oxygen made aboard the ISS? It's handled in one of three ways, using oxygen generators, pressurized oxygen tanks or solid fuel oxygen generators (also called oxygen candles).
The ISS's Wi-Fi is primarily for operational purposes, enabling astronauts and cosmonauts to communicate with Earth, control onboard laptops, and conduct scientific experiments. The Wi-Fi system on the ISS is part of its broader network infrastructure, which includes various communication technologies.
So where does the force come from? It comes from the gravitational pull of the Earth. In fact, when orbiting the Earth, the ISS (or any other satellite) experiences a perfect balance between the inward pull of gravity, and the centripetal acceleration it requires to keep moving in a circle.
Astronauts float around in space because there is no gravity in space. Everyone knows that the farther you get from Earth, the less the gravitational force is. Well, astronauts are so far from the Earth that gravity is so small. This is why NASA calls it microgravity.
Wherever you find matter, you'll find gravity. You could never travel to a gravity-free planet, only one with greater or lesser mass resulting in greater or lesser gravity.
Most of us can withstand up to 4-6G. Fighter pilots can manage up to about 9G for a second or two. But sustained G-forces of even 6G would be fatal. Astronauts endure around 3G on lift-off, one G of which is Earth's own pull.
How many G forces can a human take before passing out?
Loss of consciousness due to the acceleration of gravity on the body is better known as G-LOC. It occurs when increased force due to gravity is applied to the body, causing a loss of consciousness. Most people can withstand anywhere between 2 to 5 G-forces relatively unaffected.
The only known way to create artificial gravity it to supply a force on an astronaut that produces the same acceleration as on the surface of earth: 9.8 meters/sec2 or 32 feet/sec2. This can be done with bungee chords, body restraints or by spinning the spacecraft fast enough to create enough centrifugal acceleration.
The gravitational field on the ISS is approximately 89% of that on the Earth's surface. Of course, irrespective of these facts, the astronauts on board the ISS (and even the ISS itself) feel 'weightless' . It is an issue of perception within the frame of reference (or place) we are in at the time.
On the ISS the ground is falling beneath them at the same rate as they are, so they don't get a reaction force from it, so they don't feel weight. But they are not unaffected by gravity.
