Server Sky Radar Fence

Most orbiting space debris objects that threaten the launch loop cross the equator twice per orbit, at launch loop altitude. The orbits are likely circular, because drag increases in the denser atmosphere of low perigee, which reduces perigee velocity, which lowers apogee.

The orbital periods are unlikely to be an exact submultiple of the sidereal day, as the loop rotates under a particular right ascension (celestial longitude). Hence, computing the threat of incoming debris, and mitigating it, means observing a ring encompassing the latitude of the launch loop all the way around the earth.

Given the geometrical reciprocity of antennas versus antenna patterns (vertical arrays and antennas emit horizontally), server sky arrays devoted to radar protection of launch loops may be arranged as ellipsoids flattened in the orbital direction, producing antenna patterns that extend east-west and are flattened north south.

Every threatening object, down to millimeter size, will be identified and precisely characterized to centimeter location and millimeter-per-hour velocity. Doppler velocity estimates will not be nearly so precise, but can help differentiate objects, whose orbits will be precisely timed and Kepler-modelled to estimate velocities and loop crossing times.

Small objects (sub-gram) will be deflected with vehicle motor coils acting as meteor bumpers. Medium objects (up to a kilogram) will be blocked with movable shields attached to magnet sleds, "launched" during payload time slots (and displacing payloads). Larger objects will be deorbited by (expensive) destructive interceptors.

Perhaps ablation lasers will find a role, but the ablated material is pushed into higher orbits, and the laser beams pose a risk to every other orbiting object.

Launch Loop Positioning

The radar fence serves a dual role; it will also interferometrically measure the precise location of every element of the launch loop, to submillimeter precision, feeding receivers and controllers on the loop itself. Although much loop communication will be by fiber optic, in an emergency a broken fiber link can be bypassed through the radar fence satellites, temporarily while the fiber is repaired or the loop safely un-deployed.


ServerSkyRadarFence (last edited 2020-07-13 18:43:50 by KeithLofstrom)