Note that we will use in a large extent, passages from the papers, para-phrasing and summarizing at will, with apologies to the authors. It seems they were extremely lucid in their text and we don't presume we could do a better job. This is not plagiarism, we simply acknowledge they said it best. It will be clear where our language is used and where we have taken theirs.
Directed Light (Incoherent) Weapons
Basically using sunlight focused by optics on orbit and then directed downward onto the planet's surface of "low altitude" (relative to on-orbit) targets, or even at targets in orbit. Film buffs will recognize this from a James Bond movie featuring Pierce Brosnan and Halle Barre ("Die Another Day"). As usual art is only slightly ahead of fact.
"Unfiltered by the atmosphere, the sun provides an enormous flux of normal (incoherent) light in near-earth orbit...Currently, this vast power source is tapped with solar arrays to power satellites. It is conceivable that large focusing mirrors equipped with pointing and tracking and maneuvering systems could be placed in orbit to intercept and redirect solar energy onto the battlefield. Single, very large mirrors (on the order of kilometers in diameter) or large arrays of smaller mirrors working in concert would be needed to make this concept useful. Even in LEO orbit, these mirrors would need very high pointing and tracking accuracies to qualify as precision aimed weapons.
Optical systems (primarily collecting apertures) currently under study have been limited artificially to a size of four meters for potential launch on the space shuttle. The optical substrates are made from ultralow-expansion, right glasses as as Zerodur that are made lightweight with acid-etching techniques. Larger, still lightweight structures could potentially be made from advanced aerogel materials, advanced ceramics (such as SiC), engineered composites, structurally supported optically coated plastics, suspended or spun reflective liquids (a liquid mirror), or inflatable mirrors (reflective films on inflatable substrate). All these approaches have been demonstrated at the earth's surface with structures measured in feet or at most a few meters.
The most likely incoherent light weapon would consist of an orbiting array of mirrors in the 10-to 100-meter class. With the proper constellation, the orbiting mirrors could intercept and redirect sunlight onto the earth's surface. The simplest use of the system would be to provide battlefield illumination on demand. Depending on the area illuminated, useful illumination could be provided by one to a 100 mirrors operating in concert. By focusing the light from many mirrors onto a single spot or series of spots, battlefield temperature could be raised (a potential form of weather modification) and optical sensors (including human eyes) could be temporarily blinded. Emergency electrical power could be "beamed" to lightweight solar panels erected to intercept the redirect sunlight. To achieve more permanent effects, such as melting, as many as 100 mirrors might need to point and track on a signal hardened target for a period ranging from several tens to hundreds of seconds. Spotlight beams from a few mirrors could also be used to aid search and rescue or special operations mission at at night. Incoherent light weapon systems are limited in the rate at which they cause permanent damage by the fact that incoherent light, unlike coherent light (laser) light, cannot be focused onto extremely small spots." 2
The system envisioned has huge technology risks and costs, most of which involve the large structure's lift, assembly and maintenance in space. Like Hubbell, the system must carefully protect the optics from attack or simply space debris, and of course there are the usual in-orbit stabilization and aiming problems the Strategic Defense Initiative folks ran into. In fact, this idea is an idea that may have had its genesis during the early years of SDI. In any case, the author believes that if the structural and stabilization problems can be overcome, this technology is viable for 2025.
DEW -- Coherent Light (Lasers)
High power lasers are the most promising high-tech weapons for the future. The Air Force BMDO program's boost phase intercept program has glommed onto the idea of hoisting a huge chemical laser in a 757 and placing it near an aggressor's ballistic missile launch point, and then simply "plinking" the launched missile before it exits the atmosphere...there is also speculation that this could be used against battlefield missiles that remain in atmosphere however that cannot be confirmed at present. The program also known as ABL in its research form is supposed to be implementable in 2006, and the chemical laser is ideal for a space-borne, ground maintained and replenished attack system. If the U.S. had a means to bear such a weapon into space in a timely fashion for the battlefield (a big IF), then the coherent light weapon would make a wonderful overhead attacker. Obviously, this might also be mountable in a rather large and armored vehicle as well for ground to ground assault, or the ABL device might be trained on ground equipment for air-to-ground assault.
The 2025 weapon also includes a ground-based system that uses a high power laser fired from a ground station, up to a satellite equipped with an steerable mirror, and reflected to another such mirror (or series) and then back down the earth. This is also known as earth-space-earth geometry (acronym happy Dod-ers might call this ESEG, but that is pure speculation. The power of the ground unit has to be higher than the space-borne unit, as it must include enough power to overcome losses in the longer paths and mirror losses, however a ground station doesn't have to worry about power so much as it does about stabilization of the mirrors in space.
A side note to this technology is that the same mirrors can be used as recon platforms by training an grounded astronomical telescope and peek at the reflection on the mirror. By aiming the mirror at an enemy's position, you now have a wonderful overhead surveillance system.
"Lasers can be built as either continuous wave (CW) or pulsed devices. "CW laser effects are generally described in terms of power density on target; pulsed laser effects are described in terms of energy density on target. Although significant advances in this technology by both Ballistic Missile Defense Office (SDIO/BMDO) and the USAF Phillips Laboratory Airborne Laser (ABL) organizations, laser technology still needs further development. To date [circa 1997 - MILNET], ground-based chemical lasers have been built in the megawatt class (the ALPHA laser). Phillips Laboratory is also developing a hundred kilowatt-class short wave CW chemical laser (SWCL) based on the oxygen-iodine chemical system. Weapons-class pulsed lasers have also been built, but primarily for effects and materials research.
CW Lasers
"For the space-earth geometry, multimegawatt power is required for a CW weapons laser, and hundreds of thousands of joules of energy per pulses is required for a pulsed weapons laser (depends on pulse length and pulse repetition frequency). Total power or energy requirements are correspondingly higher for the earth-space-earth geometry; Constellations employing only a few space platofrms (e.g., laser station for the space-earth geometry, laser mirrors for the earth-space-earth geometry) would have to compensate for the long slant ranges and correspondingly higher-atmospheric distortion by using even more powerful beams. Lasers are not all-weather systems. The laser wevelength, and therefore the laser gain medium and optics train, must be carefully chosen to permit good atmospheric propagation. Clouds absorb and scatter laser light, removing power from the beam and distorting the beam's "footprint".
