With so much excitement around space right now, what with Elon landing rockets and launching astronauts to the ISS, many ask how do things stay in orbit?
On May 30th, astronauts Robert Behnken and Douglas Hurley successfully blasted off to the International Space Station on board the SpaceX Dragon capsule, but what many people don’t know is that despite looking like they’re stationary, they’re actually traveling at around 17,000 miles per hour.
We’re all aware of the complexity of rocket science and how difficult it is to get a human safely up out of the earth’s atmosphere and into space, but how do things stay in orbit once they arrive?
Stated in Newton’s first law of motion; an object in motion will stay in motion unless something pushes or pulls on it.
But why doesn’t the ISS or orbiting satellites just drift off into space or coming crash back to earth? That’s where gravity comes in. Let’s use a satellite to explain;
Without gravity, an earth-orbiting satellite would take off into space in a straight line, but with gravity it’s pulled back towards earth. The easy way to explain it is that an earth-orbiting satellite is in a constant tug-of-war with its want for traveling in a straight line and the pull of earth’s gravity.
For example, the ISS is traveling at 17,000mph and the station’s momentum, combined with earth’s gravitational pull, is what allows it to stay balanced in orbit.
If the forward momentum of a satellite is too great, it will speed past and not enter into an orbit. If momentum is too small, the satellite will be pulled down towards earth by gravity and smash into a thousands pieces.
When these forces are balanced, the object is always falling toward earth, but because it’s moving fast enough, it never hits the earth.
“Orbital velocity” is the speed needed to stay in orbit. At an altitude of 150 miles (242 kilometers) above Earth, orbital velocity is about 17,000 miles per hour. Satellites that have higher orbits have slower orbital velocities.