ISDC 2013

I will present two papers:

• Server Sky Technology, Thursday at 11 - 1150
• Server Sky Applications, Saturday 10 - 1030

New ideas since 2010: Thinsat design

• 5 gram Version 4 thinsats, 5 m²/kg for light pressure stability.

  • Version 3 thinsats assumed 3 grams and 8 m²/kg Thinsat orbits are modified by light pressure, and drift over the course of a year. The drift is too high for Version 3, bringing the thinsats closer to the Lageos orbits without enough safety margin.

• More conservative non-transparent reflective electrochromic thrusters.
  • Based on inorganic amorphous nickle hydroxide and tungsten oxide with a solid state electrolyte.
  • These should be highly radiation resistant and leak-proof compared to organic/liquid thrusters.
• Aluminum substrate.
  • This provides the reflector for the thrusters, and provides an electrical ground plane.
  • Can be roll fed, and embossed with slots, through-holes, and cavities for chips.
  • Less fragile than V3 glass substrates.
• Slot antennas
  • Rather than wire antennas surrounded by insulator, slot antennas are cut into the ground plane and offer much higher drive impedance.
  • Slots can be dual-fed, providing low SWR at both 60GHz and 70GHz for intra-array and ground-link communication.
  • Most of the ground plane remains intact for solar cells, chips, and wiring. Signal strengths are small enough that there will be little RF coupling to differential signalling wires.
  • Slot antennas can have E-W or N-S orientation in different arrays.

  • This permits two different families of thinsats, "open" and "managed", allowing some countries to manage internet access for their citizens, while others allow unrestricted access to the internet.

• Geodesic arrays
  • An icosahedron (12 vertices, 20 faces, 30 edges) derived geodesic sphere, squashed in the radial direction.
  • A V=31 sphere contains 9612 thinsats, weighs 48 kg, is about 100 meters across, and produces 37 kilowatts peak.
  • Preliminary research shows 300 meter diameter half-power ground spots with uniformly dispersed scatter
  • No high power grating lobes
  • No more tinkering with a three dimensional cartesian grid
• Dish-shaped thinsats with two different curvatures, not flat
  • Alternating curvature thinsats will be stacked and squashed together for launch
  • In orbit, the stack will be released, and the squashed thinsats will deploy like a giant Belleville spring
  • Curved thinsats always have some edge-on exposure. If a thinsat somehow becomes stably aligned edge-on to both the equator and the sun (this can happen at the spring and fall equinoxes), there is enough solar exposure to provide a trickle of power and turning thrust, so the thinsat can reorient face-forwards to the sun.
  • This also stiffens the thinsat, increasing the frequency of the vibration modes and dampening faster
  • This makes reflective dishes possible, pairing thinsats as dish and focus.

New ideas since 2010: Applications

• Thinsat arrays are > 500x more weight efficient compared to space solar power feeding ground data centers

  • Developed world data centers will remain leaders in their markets
  • Developing world areas lacking infrastructure and reliable power can access arrays for low startup costs and rapid growth

  • I will cover data center applications on thursday, not enough time on saturday

• Internet via cell phones for the rural developing world
  • India can build and launch
  • India and its disconnected half billion are of particular interest
  • Western China has similar opportunities
  • Intel Hillsboro will make the high-tech chips, but both these countries can make everything else, and launch the results
• Space debris radar tracking
  • Multiple look-down arrays can focus megawatts of power on a small region of space.
  • Interference patterns create high power standing waves.
  • Space objects passing through the standing waves will create sub-kilohertz-modulated returns
  • Thinsat receivers and computers can correlate the returns for precise object location, velocity, shape, and rotation
• Space debris ballast
  • Ultralight thinsats, too light for long term stability, can be launched from earth at far lower cost
  • With precision tracking, and EDDE or VASIMR space tugs, derelict space debris can be captured and returned to M288 orbit
  • At M288, laser cutters can chop the debris into gram-weight ballast, which is attached to the ultralight thinsats
  • This reduces launch costs, while eliminating large debris objects, turning garbage into gold
  • Obsolete and damaged thinsats can also be cut up and turned into ballast
  • When the space debris is gone, material gathered on the moon can be used as ballast
  • This is a very simple first step to space manufacturing

I will not cover these at applications ISDC with only half an hour

• Space substrates
  • With more sophistication, obsolete chipsats can be refurbished with new chips from earth
    • The chips are 99% of the technological capacity and 1% of thinsat weight
  • Substrates can be formed from lunar materials, rolled, embossed, wired, and cut in orbit
    • The aluminum substrates for thinsats need not be high quality aluminum
    • However, metal refining, forming, and wire patterning are far more complicated than making ballast
• Using antenna polarization to deliver both "open" and "managed" internet service
• No chip manufacturing in space.
  • Terrestrial fabs are huge, expensive, and delicate. It will be decades before we can orbit them, along with the huge staffs and supply chains necessary to run them.
  • A fab never turns out more than a tiny fraction of its weight in silicon, so it makes sense to leave them on the ground until ground and buildings and residences are cheaper in orbit.
  • A fab uses 12 kilograms of water to make a square centimeter of silicon wafer. Making ultrapure silicon wafers, and thinning the wafer, uses even more.