how does satellites stay up in space??

Question: how does satellites stay up in space??
- Keywords:
  satellite
Asked by ellieexo to Adam, Alexander, Aron, Jess, Neil on 17 Mar 2014.
- Alexander Finch answered on 17 Mar 2014:
  
  Oooh! One of my favourite questions! Lots of adults don’t even know this 😀
  
  Why do satellites stay in space and not fall right down to Earth? Well, actually, they are always falling. All the time they are falling almost as fast as a ball you might drop. The reason they don’t come crashing on your head is because they are also moving sideways. Very fast. So fast that, by the time they would fall to the ground, they’ve moved to far to the side that the Earth isn’t below them anymore, because it is round. It is like they fall to the ground and “miss” it! They keep doing this on and on; this is known as being in orbit. The important thing is that, in addition to being high up, your satellite also needs to be going sideways really fast – like 4.5 miles every second. That’s also the reason that rockets appear to “turn over” and fly sideways as they go up…
  
  For a better explanation, have a look at this page, under “Orbital Motion” half way down:
  http://www.kcvs.ca/martin/astro/au/unit1/45/chp4_5.html
  There’s a cool mountain cannon simulator there that explains it pretty well 🙂
- Aron Kisdi answered on 17 Mar 2014:
  
  They move fast and they are outside of the atmosphere.
  
  You experienced how the gravity of Earth pulls things towards it when you dropped something. To escape the gravity of Earth you need to move very fast. Because Earth is (roughly) spherical if you move fast enough even though the Earth is pulling you in it is also curving in so you do not get closer to the surface. You will go around and around on what is called orbit. To get to this fast speed we currently use rockets.
  
  Another problem is the atmosphere, even if you move very fast if you are in the atmosphere it will slow you down unless you keep using your rocket. In fact satellites that are on low orbit and “touch” the top of the atmosphere will eventually fall back (de-orbit). If you want to stay up for a long time, you need to be on a high orbit that is outside of the atmosphere.
  
  If you have even more speed (more rockets!) you can break away from Earth completely and go to other planets. All the planets are in the influence of the Sun, and you need even more speed to break away from the Sun completely. For example there are at least 4 spacecraft that are heading out on a path leaving the solar system completely:
  Voyager 1 and 2 and Pioneer 10 and 11
- Jessica Marshall answered on 18 Mar 2014:
  
  Ohh- look at the other answers! What us also really cool is the different types of propulsion to keep them in space, I work on an electric propulsion systems which is really cool- fires ions to push the satellite.
- Neil Bowles answered on 18 Mar 2014:
  
  One fun thing to think about is that for places without an atmosphere to slow the satellite down like the Moon, you are technically in orbit until you hit something. This is what happened to two spacecraft called GRAIL a couple of years ago. Their orbit was gradually lowered until it got so low they hit the side of a lunar mountain.

Question: how does satellites stay up in space??

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