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Directed energy for planetary defense is now a viable option and is superior in many ways to other proposed technologies, being able to defend the Earth against all known threats. This paper presents basic ideas behind a directed energy planetary defense system that utilizes laser ablation of an asteroid to impart a deflecting force on the target. A conceptual philosophy called DE-STAR, which stands for Directed Energy System for Targeting of Asteroids and exploration, is an orbiting stand-off system, which has been described in other papers. This paper describes a smaller, stand-on system known as DE-STARLITE as a reduced-scale version of DE-STAR. Both share the same basic heritage of a directed energy array that heats the surface of the target to the point of high surface vapor pressure that causes significant mass ejection thus forming an ejection plume of material from the target that acts as a rocket to deflect the object. This is generally classified as laser ablation. DE-STARLITE uses conventional propellant for launch to LEO and then ion engines to propel the spacecraft from LEO to the near-Earth asteroid (NEA). During laser ablation, the asteroid itself provides the propellant source material; thus a very modest spacecraft can deflect an asteroid much larger than would be possible with a system of similar mission mass using ion beam deflection (IBD) or a gravity tractor. DE-STARLITE is capable of deflecting an Apophis-class (325 m diameter) asteroid with a 1- to 15-year targeting time (laser on time) depending on the system design. The mission fits within the rough mission parameters of the Asteroid Redirect Mission (ARM) program in terms of mass and size. DE-STARLITE also has much greater capability for planetary defense than current proposals and is readily scalable to match the threat. It can deflect all known threats with sufficient warning. [ABSTRACT FROM AUTHOR]

Directed energy laser ablation at the surface of an asteroid or comet produces an ejection plume that will impart a thrust on the asteroid. This thrust can mitigate a threatened collision with the Earth. This technique uses the asteroid itself as the deflection propellant. The DE-STAR laser system is designed to produce a sufficiently intense spot on the surface of an asteroid to accomplish this in one of two operational modes. One is a complete “stand-off” mode where a large space based phased-array laser directed energy system can interdict asteroids at large distances allowing sufficient time to mitigate nearly all known threats. A much smaller version of the same system, called DE-STARLITE, can be used in a “stand-on” mode by taking a much smaller laser to the asteroid and slowly deflecting it over a sufficiently long period of time. Here we present orbital simulations for a range of near-Earth asteroid impact scenarios for both the stand-off and stand-on systems. Simulated orbital parameters include asteroid radius and composition, initial engagement time, total laser-on time and total energy delivered to target. The orbital simulations indicate that, for exposures that are less than an orbital time, the thrust required to divert an asteroid is generally inversely proportional to laser-on time, proportional to target mass and proportional to the desired miss distance. We present a detailed stand-on scenario, consistent with current dedicated mission capabilities, to show the potential for laser ablation to allow significant deflection of targets with small systems. As one example we analyze a DE-STARLITE mission scenario that is in the same mass and launch envelope as the proposed Asteroid Redirect Mission (ARM) but using a multi kilowatt class laser array capable of deflecting a 325 m diameter asteroid with 2N of thrust for 15 years in a small fraction of even the smallest SLS block 1 launch vehicle configuration. [ABSTRACT FROM AUTHOR]

• Rheological-mechanical behavior of asphalt binders and BBDr mixes are evaluated. • Two SBS molecular chains generates 60/85 E and HiMA bituminous matrixes. • DSR analyses describe the rheological spectra of the binders in the complex plane. • BBDr asphalt mixes were mechanically evaluated by the French standardized criteria. • HiMA matrix provides superior rheological and mechanical behavior than 60/85 E. This manuscript reports on two Styrene-Butadiene-Styrene (SBS) polymeric molecular chains so-called 1101AT and D0243, used to modify a 50/70 pen grade neat asphalt binder sample, generating the matrixes 60/85 E and Highly Modified Asphalt (HiMA), respectively. Some research gaps still exist and need to be investigated further, principally on why and how these distinct molecular chains influence the rheological-mechanical behavior of the asphalt binders and asphalt mixes, even pertaining to the same polymeric group. Dynamic Shear Rheometric (DSR) analyses describe the rheological spectra of the binder samples, considering the dynamic stiffness modulus in the complex plane |G*|. Porous asphalt mixes were evaluated considering the French formulation methodology and the following aspects: compaction ability, deleterious action of water, seepage speed and resistance to rutting. The results obtained indicate that HiMA matrix presented superior long-term rheological and mechanical behavior compared to 60/85 E, due to the more elaborate polymeric chain being associated to a bituminous matrix with rheological spectra providing less thermal and kinetic susceptibility, although its highest dynamic viscosity implies little reduction in the air void content and, consequently, lower seepage speeds to the porous asphalt mixes, but greater rutting resistance. [ABSTRACT FROM AUTHOR]

• Design and numerical damage analyses of an airfield runway pavement are carried out. • Materials, mechanical behavior models and aircraft are defined to pavement design. • Linear elastic and viscoelastic numerical analyses are the main evaluation scopes. • Viscoelastic analyses provide more discriminating assessment of damage phenomena. • Landing gear geometric configuration plays decisive role on damage propagation. Design parameters and evaluation of associated mechanical behavior of an airfield runway asphalt concrete pavement structure is reported. French aeronautical design methodology was taken as reference. Field and laboratory procedures were employed to determine constituent materials of the designed structure. Stationary linear elastic and dynamic viscoelastic numerical damage analyses were developed and compared, using computerized tools based on 3D Finite Element Methods. Results indicate that viscoelastic analyses provide more discriminating assessment of damage phenomena along the depth of pavement layers, and that landing gear geometric characteristics are more diagnostic than aircraft gross weight for cumulative damage propagation. [ABSTRACT FROM AUTHOR]