Low-Noise Thrust Generation by Laser-Ablative Micropropulsion

Abstract

Aiming for the generation of high-precision thrust in the μN range, laserinduced ablation of propellant material is employed in order to reduce thrust noise by avoiding moving parts inside the thruster. Focused high-intensity laser pulses are used for thrust generation by the recoil of the jet of the ablated material. Whereas a single laser pulse yields an extremely low impulse bit down to 1 nNs in a 40 μm focal spot on aluminum, a broad thrust range can be accessed by the variation of the laser pulse repetition rate up to several hundreds of kilohertz. Thrust measurements with a highly sensitive torsional balance, calibrated by photon pressure, yield coupling coefficients up to 15 μN per Watt average laser power and beyond. The concept of 3D electro-optical beamsteering is discussed which is essential to ablate every part of the propellant. A detailed study for the determination of the optimum laser parameters is carried out.