Numerical Simulations on Laser-Ablative Micropropulsion with Short and Ultrashort Laser Pulses

Scharring, Stefan; Lorbeer, Raoul-Amadeus; Eckel, Hans‐Albert

doi:10.2322/tastj.14.pb_69

Cited by 12 publications

(12 citation statements)

References 17 publications

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“…A detailed study related to our work on the field of laser-ablative micropropulsion is given in Ref. 17, covering a wide range of pulse lengths from 100 fs to 10 ns with fluences from 0.1 to 24 J∕cm 2 . While the code was originally developed for laser-matter interaction with ultrashort pulses, we have confirmed good agreement with experimental results in the nanosecond range as well.…”

Section: Simulations On Momentum Couplingmentioning

confidence: 99%

Laser-based removal of irregularly shaped space debris

2016

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, "Laser-based removal of irregularly shaped space debris," Opt. Eng. 56(1), 011007 (2016), doi: 10.1117/1.OE.56.1.011007. Abstract. While the feasibility of laser space debris removal by high energy lasers has been shown in concept studies and laboratory proofs of principle, we address the question of the effectiveness and responsibility associated with this technique. The large variety of debris shapes poses a challenge for predicting amount and direction of the impulse imparted to the target. We present a numerical code that considers variation of fluence throughout the target surface with respect to the resulting local momentum coupling. Simple targets as well as an example for realistic space debris are investigated with respect to momentum generation. The predictability of the imparted momentum is analyzed in a Monte Carlo study. It was found that slight variations of the initial debris position and orientation may yield large differences of the modified trajectories. We identify highly cooperative targets, e.g., spheres, as well as targets that are strongly sensitive to orientation, e.g., plates, and exhibit a poor performance in laser debris removal. Despite limited predictability for the motion of a particular debris object, the laser-based approach appears to be suitable for space debris removal, albeit not with a deterministic but rather with a probabilistic treatment of the resulting trajectory modifications.

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Section: Simulations On Momentum Couplingmentioning

confidence: 99%

Laser-based removal of irregularly shaped space debris

2016

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“…The high data for c in the picosecond range, however, are somewhat misleading here since in the absence of plasma shielding for ultrashort pulses c m is limited by the maximum tensile strength of the material. 19 Overall, the plasma exponent c is considerably higher than the theoretical value of 1/4 derived from Phipps, cf. Eq.…”

Section: Momentum Couplingmentioning

confidence: 79%

“…As it can be expected from Eq. 1, Φ 0 increases with τ, furthermore, for ultrashort pulses, i.e., below τ ¼ 50 ps in the case of aluminum, 19 Φ 0 stays more or less constantly on a rather low value.…”

Section: Momentum Couplingmentioning

confidence: 92%

“…Although in the short-pulse regime ablation is mainly governed by surface vaporization of the heated material, fast heating with an ultrashort laser pulse raises a strong shock wave followed by a large rarefaction wave, which exceeds the maximum tensile strength of the material. 19 It can be seen from the discontinuities in Fig. 2(b) that material spallation occurs several times at the surface before the rarefaction wave sufficiently relaxes.…”

Section: Residual Heat In Laser Ablationmentioning

confidence: 95%

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Momentum predictability and heat accumulation in laser-based space debris removal

et al. 2018

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Small space debris objects of even a few centimeters can cause severe damage to satellites. Powerful lasers are often proposed for pushing small debris by laser-ablative recoil toward an orbit where atmospheric burn-up yields their remediation. We analyze whether laser-ablative momentum generation is safe and reliable concerning predictability of momentum and accumulation of heat at the target. With hydrodynamic simulations on laser ablation of aluminum as the prevalent debris material, we study laser parameter dependencies of thermomechanical coupling. The results serve as configuration for raytracing-based Monte Carlo simulations on imparted momentum and heat of randomly shaped fragments within a Gaussian laser spot. Orbit modification and heating are analyzed exemplarily under repetitive laser irradiation. Short wavelengths are advantageous, yielding momentum coupling up to ∼40 mNs∕kJ, and thermal coupling can be minimized to 7% of the pulse energy using short-laser pulses. Random target orientation yields a momentum uncertainty of 86% and the thrust angle exhibits 40% scatter around 45 deg. Moreover, laser pointing errors at least redouble the uncertainty in momentum prediction. Due to heat accumulation of a few Kelvin per pulse, their number is restricted to allow for intermediate cooldown. Momentum scatter requires a sound collision analysis for conceivable trajectory modifications. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…However, the mentioned problems in IMD with higher fluences limit its practical use in this field of application since the anticipated working point for the future microthruster is in the range of at least 3 to 6 times of the ablation threshold [18].…”

Section: Discussionmentioning

confidence: 99%

Dynamic Material Parameters in Molecular Dynamics and Hydrodynamic Simulations on Ultrashort-Pulse Laser Ablation of Aluminum

Scharring

Patrizio

Eckel

et al. 2018

High Performance Computing in Science and Engineering ' 17

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Molecular dynamics reveals a detailed insight into the material processes. Among various available codes, IMD features an implementation of the twotemperature model for laser-matter interaction. Reliable simulations, however, are restricted to the femtosecond regime, since a constant absorptivity is assumed. For picosecond pulses, changes of the dielectric permittivity and the electron thermal conductivity Ä e due to temperature, density and mean charge have to be considered. Therefore, IMD algorithms were modified for the dynamic recalculation of and Ä e for every timestep following the corresponding implementation in the hydrodynamic code Polly-2T. The usage of dynamic permittivity yields an enhanced absorptivity during the pulse leading to greater material heating. In contrast, increasing conductivity induces material cooling which in turn decreases absorptivity and heating resulting in a higher ablation threshold. This underlines the importance of a dynamic model for and Ä e with longer pulses which is commonly often neglected. Summarizing all simulations with respect to absorbed laser fluence, ablation depths in Polly-2T are two times higher than in IMD. This can be ascribed to the higher spallation strength in IMD stemming from the materialspecific potential deviating from the equations of state used in Polly-2T.

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Numerical Simulations on Laser-Ablative Micropropulsion with Short and Ultrashort Laser Pulses

Cited by 12 publications

References 17 publications

Laser-based removal of irregularly shaped space debris

Laser-based removal of irregularly shaped space debris

Momentum predictability and heat accumulation in laser-based space debris removal

Dynamic Material Parameters in Molecular Dynamics and Hydrodynamic Simulations on Ultrashort-Pulse Laser Ablation of Aluminum

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