Laser propulsion for precise space thrusters in space missions application
Laser propulsion is ideally suited to micro propulsion as a result of its high precision and very simple infrastructure.
The work on laser propulsion at the DLR Institute of Technical Physics covers both basic investigations on pulsed thermal laser propulsion with stationary high power laser sources and the development and qualification of laser ablation based micro rockets.
Image: Thermal laser propulsion – Laser induced detonation in the thrust chamber. Credits by DLR
Goal of this project is the development of an alternative micro drive, able to be used for the positioning of satellites in space missions. Currently the research work is focused on the propulsion concept and first experiments for evaluation.
To guarantee a lifetime over many years under harsh conditions it was considered to avoid any moving parts, having an inertial free operation and minimum rest acceleration.
The latest research objective is the development and qualification of highly precise thrusters with thrust levels in the range of 0.1 µN to 1 mN. These kinds of alternative micro propulsion concepts which are necessary for many missions with precise position and orbit control are now developed.
For micro propulsion by laser ablation the (compact) laser source is integrated in the thruster device. By directing a laser beam on a target, ablating a part of the surface of the target a thrust is generated as a result of the recoil of the ablated propellant. The direction of the laser beam will be controlled using an electro-optical scanning device.
For this project AMS Technologies introduced the KTN scanner made by our supplier NTT in Japan. This scanner is based on a KTN crystal using the very efficient electro-optical effect of this material, forming a high speed scanning device without any moving parts. These scanners are used in printing, display, telecom, metrology, sensing and imaging applications but not yet in space.
The main tasks which had to be solved in this project were to define the special requirements of this application and to adapt the scanner. First step to evaluate the possibility to use the scanner for this application was to find out the damage threshold of the used crystal and the coating at the end faces of the crystal. We discussed several versions of the device to define the quality of the test samples to get most information out of the test.
Initially it was planned to use a three-pass scanner to achieve a higher deviation angle of the beam. The angle depends on the length of the crystal passed by the beam, realized in this design by letting the beam three times pass the crystal.
The test of this version showed that the coating has a too low damage threshold, caused by the design of the three-pass scanner.
Image: High-speed, voltage-controlled laser beam scanner with novel optical phenomenon using KTN crystal. Credit by NTT-AT
After the discussion with NTT and the customer we exchanged the scanner to a one pass system, giving a lower beam deviation but higher durability.
These scanners are now under more detailed test, but generally chosen as the device which will be used in this kind of micro drives for satellites. The research work is going on; the use of the KTN scanner in real space missions in future is very likely.
The value AMS Technologies added here was a close coordination of technical discussion and all necessary changes of the product between the manufacturer NTT in Japan and the customer in Germany, based on the understanding of the project requirements. This was accompanied by the necessary logistics work.
Supporting this special project we explored together with our supplier NTT a complete new range of application for this special device.
For more information about the application we recommend to read www.dlr.de
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