https://repository.tudelft.nl/islandora/object/uuid%3Ae80d13bb-0538-4a46-9e65-ad7f3b330883/datastream/OBJ/download

A review of MEMS micropropulsion technologies for CubeSats and PocketQubes

A liquid monopropellant MEMS thruster was designed, fabricated and tested. For application on a nanosatellite for orbit control, a liquid propellant MEMS thruster delivers better performance than a solid thruster. Two issues must be addressed for a liquid monopropellant MEMS thruster: high energy content of the monopropellant to overcome the excessive heat loss associated with the small scale of the thruster, and repeatability of generated thrust force. The present study proposed blending 90 wt% hydrogen peroxide with ethanol at an oxidizer to fuel ratio of 30 to enhance the energy content of the propellant. The thruster structure was constructed using glass layers that were individually patterned by wet etching. The decomposition catalyst was separately prepared by wet impregnation of the active material, Pt, on the gamma alumina pellets and inserted into the thrust chamber before the UV bonding process of the glass layers. The firing test of the assembled MEMS thruster was conducted and thrust was measured both with ethanol blended hydrogen peroxide and pure hydrogen peroxide as a reference monopropellant. The measured thrusts were approximately 30 mN for both 1.7 ml min−1 flow rate of blended hydrogen peroxide and 2.0 ml min−1 flow rate of pure hydrogen peroxide. The measured thrust for 1.7 ml min−1 pure hydrogen peroxide was approximately 24 mN. The measured thrust was 40% less than the design thrust for both monopropellants. The uncertainty of the thrust was less with blended monopropellant than with pure hydrogen peroxide.

https://iopscience.iop.org/article/10.1088/0960-1317/24/10/104001/pdf

Design, fabrication and thrust measurement of a micro liquid monopropellant thruster

This paper reports a feasibility study of regenerative micro-cooling channels in a liquid microthruster composed of thermally fragile materials. Glass, which is among the most thermally insulating materials, has been used as microthruster fabrication material to suppress excessive heat loss in micro scale thruster. However, the frangibility of glass has remained a challenge to be solved. To thermally manage the fragile structure, the use of regenerative micro-cooling channels in a microthruster is suggested in this work, and the feasibility was tested through design, fabrication and experimental performance of a glass microthruster with microchannels. Nine photosensitive glass layers were wet etched and integrated to fabricate the microthruster. Before integration of the layers, a fabricated Pt/Al 2 O 3 catalyst was inserted into the chamber of the microthruster for propellant decomposition. Hydrogen peroxide (90 wt%) was used as a monopropellant and served as the working fluid for regenerative cooling. A liquid microthruster with micro-cooling channels was successfully fabricated with a photosensitive glass MEMS process. Experimental performance tests were conducted while measuring the microthruster chamber pressure, chamber temperature, and surface temperatures. The test results showed normal operation of the microthruster, which had an estimated thrust of approximately 48 mN and temperature efficiency of approximately 41%. The decreasing surface temperatures of the microthruster during thruster operation successfully validated the cooling effect of the micro-cooling channels and demonstrated their practicality for the regenerative cooling of liquid microthrusters.

Fabrication of a liquid monopropellant microthruster with built-in regenerative micro-cooling channels

Monopropellant ceramic microthrusters with an integrated heater, catalytic bed and two temperature sensors, but of various designs, were manufactured by milling a fluidic channel and chamber, and a nozzle, and screen printing platinum patterns on green tapes of alumina that were stacked and laminated before sintering. In order to increase the surface area of the catalytic bed, the platinum paste was mixed with a sacrificial paste that disappeared during sintering, to leave behind a porous and rough layer. As an early development level in manufacturing robust and high-temperature tolerant microthrusters, the influence of design on the temperature gradients and dry temperature tolerance of the devices was studied. On average, the small reaction chambers showed a more than 1.5 times higher dry temperature tolerance (in centigrade) compared to devices with larger chambers, independent of the heater and device size. However, for a given temperature, big devices consumed on average 2.9 times more power than the small ones. It was also found that over the same area and under the same heating conditions, devices with small chambers were subjected to approximately 40% smaller temperature differences. A pressure test done on two small devices with small chambers revealed that pressures of at least 26.3 bar could be tolerated. Above this pressure, the interfaces failed but the devices were not damaged. To investigate the cooling effect of the micropropellant, the endurance of a full thruster was also studied under wet testing where it was fed with 31 wt.% hydrogen peroxide. The thruster demonstrated complete evaporation and/or full decomposition at a power above 3.7 W for a propellant flow of 50 µl min−1. At this power, the catalytic bed locally reached a temperature of 147 °C. The component was successfully heated to an operating temperature of 307 °C, where it cracked. Under these firing conditions, and assuming complete decomposition, calculations give a thrust and specific impulse of 0.96 mN and 106 s, respectively. In the case of evaporation, the corresponding values are calculated to be 0.84 mN and 92 s.

https://iopscience.iop.org/article/10.1088/1361-6439/aa6550/pdf

Endurance and failure of an alumina-based monopropellant microthruster with integrated heater, catalytic bed and temperature sensors

Cost analysis of solar thermal propulsion systems for microsatellite applications

Feasibility of chemically synthesized MnO2 nanowire catalyst embedded silicon microelectromechanical systems (MEMS) H2O2 monopropellant microthruster has been demonstrated. Due to exothermic reaction process, sustenance of thrust generation does not require any heating of propellant thus minimizing electrical power requirement. The thruster device integrates inlet nozzle, microchannel, MnO2 nanowire embedded reaction chamber, in-plane exit nozzle and a microheater in the silicon layer. Nozzle configuration and catalyst bed was designed using simple analytical equations to achieve complete decomposition of H2 O2 and maximum thrust force by controlling the propellant flow. Simulation of hydrogen peroxide decomposition process was carried out to evaluate the thermo-chemical characteristics. The MnO2 nanowire has been obtained using a low-cost synthesis process and characterized using field emission scanning electron microscopy, Energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction studies. Thruster fabrication using micromachining process and its testing have been briefly described. The device is capable to produce 1 mN thrust and specific impulse of 180 s using 50 wt.% concentrated H2O2 of flow rate 1.25 mg/s with total ignition energy of 44 J required for preheating the catalyst bed. Detailed thrust measurement was carried out with propellant mass flow rate for different throat area of exit nozzle, and the results were interpreted with theoretical model.

A. K. Sinha

Papers

$\hbox{MnO}_{2}$ Nanowire Embedded Hydrogen Peroxide Monopropellant MEMS Thruster

Change in the gas sensing mechanism and improved sensing response on ion-irradiated palladium-graphene oxide nanocomposite