Design, fabrication, and calibration of a micro-load cell for micro-resistojet development.

In this paper, a micro-load cell utilized for the thrust measurement of a micro-resistojet is described. To improve the degree of completion of the micro-resistojet during the development process, a concept of a micro-load cell, which enables sufficient performance evaluation under space environmental conditions, was proposed through minimization and simplification of a thrust measurement stand. The piezoresistive sensing method was applied to this load cell, which was composed of a membrane, strain gauges, and a built-in Wheatstone bridge. The membrane size was designed using large-deflection theory so that the load cell could exhibit linear characteristics within the measurement range. A polysilicon strain gauge with a high gauge factor was used for the piezoresistor. The strain gauge also had very low sensitivity to temperature, allowing accurate measurement of the membrane deflection caused by thrust without requiring an additional compensation circuit. Four strain gauges were placed to form a full-bridge circuit at the edge of the membrane. The load cell was then realized by a microelectromechanical system fabrication process. The fabricated load cell was calibrated using a three-axis precision moving stage and a commercial load cell. As a result, the load cell output signal was linear in the measurement range of 1-7 mN and the measured sensitivity of the sensor was 1.566 31 × 10-4 V/mN. The calculated nonlinearity was within 1% in the measurement range.

Fabrication of Nano-Structured V-Shaped Grooves on B-Si Wafer for On-Board Spaceborne Blackbody System.

Nano-structured V-shaped grooves on the black-silicon (B-Si) was fabricated to improve the optical emissivity for on-board spaceborne blackbody system. The deep reactive ion etching (DRIE) process was used to fabricate the V-shaped grooves on the B-Si wafer according to the etching conditions. The scanning electron microscopy (SEM) and infrared (IR) spectroscopy were used to evaluate the morphology, aspect ratio, and reflectance of the fabricated B-Si specimen. The surface of the B-Si was successfully structured with the nano-scale V-shaped grooves of which the height and diameter were approximately 670 nm and 200 nm, respectively. The reflectance of the B-Si was close to zero in a wavelength less than 1 µm. As a result, the fabricated B-Si with the nano-structured V-shaped grooves was suitable to the blackbody target for on-board spaceborne blackbody system.