Laser weapon activities in Germany - technology and
operational safety aspects
Hans-Albert Eckel
German Aerospace Center (DLR), Institute of Technical Physics, Pfaffenwaldring 38-40, 70569 Stuttgart,
Germany Email: hans-albert.eckel@dlr.de
Abstract: The introduction of laser weapons is not only a technical challenge but also requires a
detailed consideration of operational safety aspects. The German activities in this field are
discussed. © 2019 The Author.
OCIS codes: 140.0140, 290.0290.
1.
Introduction
With recent advances in high-energy laser sources, laser weapons can be expected in the battlefield in the near
future, of course dependent on the amount of investments. Their laser power will be tens of kilowatts within the
next five years, up to above 100 kW for a whole decade [1].
Laser weapons have several main advantages over conventional weaponry. They can be used discreetly; radiation
above and below the visible spectrum is invisible and does not generate sound. Lasers travel at light-speed and
have near infinite range limited only by beam diffraction, spread, and absorption or scattering by intervening
atmospheric contents. Laser weapons potentially eliminate many logistical problems in terms of ammunition
supply, as long as there is enough energy available. Depending on several operational factors, laser weapons may
be cheaper to operate than conventional weapons in certain scenarios.
On the other hand high energy laser systems developed for outdoor military applications present unique
challenges for laser safety and risk analyses. While the technical problems are largely solved, the question of laser
safety remains challenging and requires further experimental investigation as well as modeling and simulation.
2.
Hazard Analysis
For a complete hazard analysis, all possible contributions must be considered. For a laser weapon, these are the
direct laser beam hazard, the target reflection hazard and the hazard due to atmospheric scattering.
While the exposure to the direct laser beam can be easily deduced from the beam parameters and the atmospheric
extinction, considerations of target and atmospheric scattering effects are more complicated.
Exposure to the beam reflected by the illuminated target can pose hazards as well. Therefore, accurate models and
simulations of reflections are needed to determine the extent of hazardous conditions for laser engagements of
targets so that testing or operational use can proceed. Such simulations are based on an engagement scenario,
which consists of laser and target properties and the geometry of their interaction. Proper hazard analysis for a
material irradiated by a laser relies upon the reflecting properties of the material surface, as these properties
determine the magnitude and direction of the reflected laser energy commonly characterized by the bidirectional
reflectance distribution function BRDF. However, a high-energy laser heating and possibly melting a material can
change the reflecting properties of that material, so these changes must be included in the hazard analysis.
Traditional methods for measuring the BRDFs of materials are not practical for measurement of materials with
rapidly-changing surface properties [2, 3].
A laser beam that propagates through the atmosphere will be attenuated as it passes through space mainly by
scattering effects. The scattered radiation may pose a hazard to observers looking at or alongside the beam. There
are two contributions to the scattered radiation that have to be taken into account: Mie (or large particle) scattering
occurs where the particle size is greater than the wavelength of the optical radiation, and is normally the dominant
contributor to the overall scattered radiation. Rayleigh (or molecular) scattering occurs where particle size is much
lower than the wavelength. The scatter hazard is inversely proportional to the visibility. A clear atmosphere may,
therefore, be almost no scatter hazard. Special attention has to be given to military operations where the visibility
is occasionally limited by natural or artificial fog and all sorts of precipitation [4].