Overview of Laser Ablation Micropropulsion Research Activities at DLR Stuttgart

Abstract

Microthrust engines (μN-mN) with high specific impulse and long lifetime that allow for precision attitude and orbit control are a prerequisite for planned and future missions for geodetic purposes or astronomic science. The potential of laser-ablative microthrusters for meeting these demands is being investigated at the Institute of Technical Physics. The concept is based on removal of a thin layer of material by focusing short laser pulses on a metal surface creating plasma or vapor. The recoil of the ablated material leads to momentum transfer to the target, which results in sub-μN to mN thrust levels for high repetition rate laser sources. Additionally, by implementing electro-optic beam steering for layer-by-layer ablation of material, moving parts that can be a significant disturbing factor for precise thrusters could be avoided in this concept. To evaluate and optimize the thruster with regards to precise thrust control, thruster lifetime and contamination issues experimental facilities comprising plasma and surface diagnostics and a thrust balance have been implemented. In addition to the experimental work, analytical calculations are undertaken to assess the future laser thruster characteristics. Furthermore, the variation of laser parameters and target material is investigated using a hydrodynamic simulation tool for laser ablation, which is to be supplemented by molecular dynamics simulations as well as by Direct Simulation Monte Carlo-Particle in Cell (DSMC-PIC) calculations in cooperation with the University of Stuttgart.