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How Do Satellites Stay in Orbit?

April 11, 2018


This article was first posted to Bang It Out on Science - the funny side of science! Check out my other content there. In the meantime, this is how artificial satellites get up into space and stay there - at least for a while.



There are roughly 1,100 working artificial satellites orbiting Earth as we speak, helping us navigate and forecast weather, making observations to space, and beaming down TV shows about dragon thrones and demogorgons. But how do these artificial satellites get up there, and more importantly, how do they stay up there? Well, before we talk about rockets, let's talk about cannons.


Imagine you fire a cannon horizontally off a mountaintop; the cannonball would fly parallel to the Earth until gravity pulled it back down to the ground. Now, imagine adding more and more gunpowder. The cannonball would fly farther and farther, and with enough gunpowder, it would eventually circle the Earth.


Does this sound mind-boggling?


The fact is: this little thought experiment first conceived by sir Isaac Newton. He was the first domino toward figuring out how to get satellites into orbit.


We send each one up on a rocket called a launch vehicle that travels straight up for only a short time, before it starts to tilt into a curved trajectory that brings it nearly parallel to Earth's surface.


The tricky part once it's up there is finding the balance between gravity and velocity, because Earth's gravitation is pulling the satellite back down. while at the same time, it's speeding forward in order to stay at its right altitude. It’s all about orbital velocity - the proper speed that creates a stable orbit, based on its altitude.


It’s a delicate balancing act - too fast, and the satellite will escape Earth's gravity and fly off into space; too slow, and it'll be pulled back in, and probably burn up on re-entry.


If a satellite is closer to Earth, it must travel faster to maintain its orbit. Most artificial satellites fly in low-earth orbit (LEO), which is between about 150 and 2,000 kilometers (~90 - 1,250 miles) in altitude. So, satellites in low LEO say have to book it at super fast speeds, whereas those in high LEO move at a more relaxed pace.


And of course, it's never easy.


Satellites have to watch out for orbital decay - the process that leads to a gradual decrease in their altitude. This is mostly due to atmospheric drag, caused by collisions with gas molecules in the atmosphere.


All artificial satellites orbiting the Earth are close enough to feel the effects of drag to some degree. Even the International Space Station, for example, orbits close to Earth, but it loses altitude every day. It counteracts this by periodically firing two of its onboard engines, and every time a resupply vessel stops by, it gives it a little extra boost into a higher altitude, therefore extending its orbital life a little longer.


Eventually, every satellite is going to face this fate. Sometimes, a satellite near the end of its career will be deorbited, or basically forced into a controlled reentry. More often, though, it's more fuel-efficient just to boost it up into what's known as a disposal orbit. In this case, the decommissioned satellite is moved out about 300 kilometers (~175 miles) from its original flight path, out of the way of working satellites and into its final, long, slow orbit.


Hundreds of satellites now are circling around in this orbiting graveyard, but since they're all experiencing the effect of Earth's atmosphere, they're going to come down at some point, and it's just a matter of time.



Don't forget to check out the rest of my articles over at Bang It Out on Science! Also, follow my Instagram (@astrolia), and subscribe to SkyFeed so you always get the latest news in space exploration, delivered straight to your inbox.


Sources: This story was originally published on SciShow Space. I am republishing a lightly edited version on SkyFeed in light of interest in the subject. Reimers, Reid. "How Do Satellites Get and Stay in Orbit?" SciShow, YouTube. 9 July 2014. Web video.

Citation: Rovira, Lia N. "How Do Satellites Stay in Orbit?" SkyFeed. 11 April 2018. Web article.

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