Deployment Orbits

The first server-sat arrays will be deployed in a "4 hour" orbit, or more precisely a 23.9344696/6 = 3.989078 hour or 14360.7 second orbit (sidereal). This means it passes over the same spot on earth 5 times per day ( = 6-1, the earth is turning underneath once per sidereal day ). A 4 hour equatorial circular orbit has a radius of 12770 kilometers, and an altitude above the equator of 6399 kilometers. This puts it in a "thinner" part of the Van Allen belt, with an estimated unshielded radiation dose of 1Mrad/year [citation needed].

At that altitude, the central orbit can be seen at 58 degrees north and south latitude, at a distance of 10500 km. The round trip ping time is 70 milliseconds. The ground ping time through optical fiber across the United States is faster in theory, but ground networks are slowed by switches and indirect routes. Ping times from fat-pipe servers in Dallas Texas to mit.edu are 42 milliseconds , and to orst.edu are 49 milliseconds, so 70msec is not way out of line. However, much of the routing will travel "around the cloud", and without local caching in the "near" links, some pings may need as much as 200 milliseconds to hop from the far side of the orbit. Still, this is better than the 250+ millisecond ping time through a geosynchronous satellite.

Server-sats will actually be deployed in very slightly inclined and elliptical orbits, which map onto a nested set of torii ("torus-es") centered on the 4 hour, zero-inclination equatorial orbit. These are 4 hour orbits as well, and the largest torii are have major radii slightly offset inwards. A plane drawn perpendicularly to the center orbit (which intercepts the orbit in two places, and also intersects the center of the earth) will have "territories" marked on it for the regions around the various orbits, and the orbits passing through each "territory" can be treated as a property. This orbital property is further subdivided into angles around the orbit. Server-sats precisely positioned in each orbit will never intersect server-sats in other properties. Arrays in orbits in the same "property" will never intersect the orbits of arrays in different properties. This allows a large region of space to be filled with server-sats, potentially trillions of them. The density is limited by shading - at some point server-sats closer to the sun will reduce the daylight falling on the ones in the "back" of the orbit, and may begin to detectably reduce the sunlight falling on the earth.

Serversats will be spaced perhaps 100 meters apart in an array - an array with 32768 server-sats will be 3.2km on a side. This puts them far enough apart that the shade area behind one 0.3 meter diameter server-sat will never completely block sunlight to the server-sat behind it. If the nested torri extend outwards to 500 km around the central orbit, that is a spatial volume of 3E10 cubic kilometers. Potentially, that is room for 30 trillion server-sats at a 100 meter spacing. This "fuzzy toroidal cloud" of server-sats will block some sunlight, both to the server-sats in the back of the toroidal cloud, and to the surface of the earth. With 30 trillion 300mm diameter server-sats, the blockage would be about 7% at noontime on the equator. However, it is hard to imagine needing that many server-sats, even if they were operating mostly as space solar power satellites, beaming about 5 watts each to the ground, as that far exceeds the projected world demand for electricity.

The orbits will not be completely filled - there will be large gaps in them to permit transit of launch vehicles. Establishing these "windows" will involve lots of negotiation, beyond the scope of this document.

• If it ever proves practical to build space elevators, there will need to be other gaps in time and "property" so that the elevators and the server-sats never interact. A failing space elevator will collide with an undetermined number of server-sats (as well as destroying all the other space elevators), so space elevators and the permanent use of these orbits (or possibly any near-earth orbit) may prove incompatible.

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