The comparison was to the centripetal force … since we’re holding doubt that’s technically true for orbits …
?? Surely this is a typo and should be 42 Mm / 36 Mm. Orbital speed approximately 3 km/s.
The best example of an intermediate orbit is the constellation of GPS satellites. The combination of a need for efficient coverage of the globe and the need to have a spread of satellite positions over the sky as seen from Earth pretty much demands such an intermediate orbit.
Besides GPS there are many satellites in medium earth orbits. This is a real-time graphical depiction of all known satellites and larger debris objects in earth’s vicinity.
- Click and drag to move it
- Scroll mouse wheel to zoom in/out (or use +/- buttons at bottom right)
- Position cursor over any object to see name and orbit
- Click on object to see details
The ring abound earth is geostationary satellites at 22,500 miles.
The Hydrogen Sonata, by Iain M Banks. The city-habitat of Fzan-Juym orbits in an artificial canyon around Eshri. Bank’s last SF novel, unfortunately.
Some informative graphs: https://www.google.ca/search?q=orbital+decay+altitude&num=20&tbm=isch&source=lnms&sa=X&ved=0ahUKEwi226SYqIbWAhWESSYKHW-vDW8Q_AUIfCgB&biw=1644&bih=883#imgrc=03O60X2nJkEzRM:
As others have said, it’s nigh impossible to be 100% stable because of the atmosphere reaches far away. I think about 200km altitude (at both perigee and apogee) should give you a few days or weeks, though.
A major consideration for ISS orbit altitude is likely to be the energy cost of getting people up there and back. Without that, the ISS could be higher and require less stationkeeping.
Wow, thanks for that cool link. It’s getting crowded up there!
Yes, of course you are right on the order of magnitude error - thanks for that.
The geostationary orbital speed is 3 km/s.
The 8 km/s figure that I gave is the theoretical orbital speed at the earth’s surface.
More specifically, the sharp ring is true geostationary satellites (geosynchronous in circular orbits above the equator), while the broad ring around that is geosynchronous satellites in inclined orbits. From the inclination, it looks like most of those were Florida launches. With an orbit like that, the satellite won’t be perfectly stationary relative to the Earth, but will trace out a figure 8 relative to the surface, which is sometimes good enough (and a bit cheaper).
There are also some geosynchronous satellites in elliptical orbits, which at any given time includes most of the satellites above geostationary height. This allows you to spend most (but not all) of your time almost (but not quite) directly above a point on the Earth that isn’t above the equator, but the drawback is that while you’re over that point, you’re about twice as far away. You’d expect this, for instance, for spy satellites watching Russia. At any given moment, there will also be some of these satellites below GEO, but they’re harder to spot on that diagram since there’s a lot of other stuff there.