AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

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spacecraft. This creates coherent RF or optical apertures that are essentially unlimited
in size, which could offer unprecedented high-resolution radiometry, hyperspectral
imaging, radar, and RF interception (for mapping, surveying, MASINT, SIGNIT), etc.
Launching laser-propelled Lightcraft nano-/pico-satellites to LEO requires megawatt­
class lasers. TEXTRON Systems Corporation's proposed 10 MW electron gun-driven
CO2/gas mixture laser is a multi-megawatt-class system that can be implemented now
because this technology requires little or no additional R&D. This system offers realistic
near-term, low-cost Lightcraft launch capability. However, this system is large,
requires a large amount of gas propellant to fuel the laser, and the system
infrastructure will cost over $200 million.
The newly emergent bulk slab solid-state, high-power fiber, and free-electron laser
technologies being explored by the various DoD directed energy weapons programs
offer higher electrical-to-optical efficiencies and overall laser performance, compact and
portable system size, less complexity and smaller weight, all at much lower system and
infrastructure cost. These lasers are scalable to megawatt-class beam power, and so
we roughly estimate that the overall system and infrastructure cost to deploy such laser
systems to launch a Lightcraft to LEO will be from several factors to an order of
magnitude (or more) lower than for the electron gun-driven CO2/gas mixture laser
system.
Removing the waste heat produced by high-power laser systems is an important factor
driving the physical limitations of scaling up the beam output power. An innovative
matched-refractive-index liquid is used to rapidly remove the heat produced by a 150
kW bulk slab solid-state laser weapon while the very high surface area-to-volume ratio
of high-power fiber lasers allows for the rapid removal of heat from the gain medium
without the need for external cooling. Phase-change materials are being explored and
devices using such materials have recently demonstrated the ability to store very large
quantities of the waste heat produced by high-power solid-state lasers, which is a
different way of rapidly removing large amounts of heat from the solid-state gain
medium. Unlike solid-state laser systems, free-electron lasers are not affected by heat
problems while their gain medium (a vacuum) cannot be damaged.
Launching a laser-propelled Lightcraft nanosat/picosat from the ground, sea, or air into
LEO requires controlling and steering the high-energy laser beam, while at the same
time making real-time adjustments to account for platform motion, optical train and
atmospheric effects on beam propagation, so that the beam maintains high quality,
low-loss, precision contact with the Lightcraft during the entire flight. Recent technical
innovations in optical train design and other system architecture have evolved beam
control devices for high-energy laser weapons toward new implementations. New beam
control devices and high-power optical train combinations have a resulting beam line
that is considerably simpler, smaller and lighter than current architectures. Almost
every component in the beam line performs multiple functions, thereby dramatically
reducing the high-power optical component count. This approach also packages all
beam control sensors, processors and drivers into a single turret assembly.
In 2005, the AFRL/PRSP (Edwards AFB, CA) concluded their laser Lightcraft propulsion
R&DTE program before launching a Lightcraft test vehicle into LEO was demonstrated
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