We have fabricated microthruster chip pairs-one chip with microthruster structures such as injection capillaries, combustion chamber and converging/diverging nozzle machined using the deep reactive ion etching process, the other chip with sputtered platinum (Pt) thin film devices such as resistance temperature detectors (RTDs) and a heater. To our knowledge, this is the first microelectromechanical systems-based microthruster with fully integrated temperature sensors. The effects of anneal up to 1,050°C on the surface morphology of Pt thin films with varied geometry as well as with/without PECVD-SiO 2 coating were investigated in air and N 2 and results will also be presented. It was observed that by reducing the lateral scale of thin films the morphology change can be suppressed and their adhesion on the substrate can be enhanced. Chemical analysis with X-ray photoelectron spectroscopy showed that no diffusion took place between neighboring layers during annealing up to 1 h at 1,050°C in air. Electrical characterization of sensors was carried out between room temperature and 1,000°C with a ramp of ±5 Kmin -1 in air and N 2 . In N 2 , the temperature-resistance characteristics of sensors had stabilized to a large extent after the first heating. After stabilization the sensors underwent up to eight further temperature cycles. The maximum drift of the sensor signal was observed for temperatures above 950°C and was less than 8.5 K in N 2 . To reduce the loss of combustion heat, chip material around microthruster structures was partially removed with laser ablation. The effects of thermal insulation were investigated with microthruster chip pairs which were clamped together mechanically. The heater was operated with up to 20 W and the temperature distribution in the chip pairs with/without thermal insulation was monitored with seven integrated RTDs. The experiments showed that a thermal insulation allows the maximum temperature as well as the temperature gradient within the microthruster chip pairs to be increased.

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PRECISE focuses on the research and development of a MEMS-based monopropellant micro Chemical Propulsion System (µCPS) for highly accurate attitude control of satellites.The availability of µCPS forms the basis for defining new mission concepts such as formation flying, advanced robotic missions and rendezvous maneuvers. These concepts require propulsion systems for precise attitude and orbit control maneuverability. Basic research will be conducted aiming at improving crucial MEMS technologies required for the propulsion system. Research and development will also focus on the efficiency and reliability of critical system components. System analysis tools will be enhanced to complement the development stages. In addition, application-oriented aspects will be addressed by two endusers who are planning a formation flying mission for which the propulsion system is crucial. Finally, the μCPS will be tested in a simulated space vacuum environment. These experiments will deliver data for the validation of the numerical models. Nomenclatureρ = density I sp = specific impulse µCPS = Micro Chemical Propulsion Systems CFD = Computational Fluid Dynamics

For aircraft and rocket engines there is a strong need to measure the pressure in the propulsion system at high temperature (HT) with a high local resolution. Miniaturized sensor elements commercially available show decisive disadvantages. With piezoelectric-based sensors working clearly above 500°C static pressures can not be measured. Optical sensors are very expensive and require complex electronics. SiC sensor prototypes are operated up to 650°C, but require high technological efforts. The present approach is based on resistors placed on top of a 2 mm diameter sapphire membrane (8 mm chip diameter). The strain gauges are made either of antimony doped tin oxide (SnO2:Sb) or platinum (Pt). This material combination allows for matching the thermal coefficients of expansion (TCE) of the materials involved. The morphology of the SnO2:Sb layer can be optimized to reduce surface roughness on the nanometer scale and hence, gas sensitivity. Antimony doping increases conductivity, but decreases the gauge factor. With this nanotechnological knowledge it is possible to adjust the material properties to the needs of our aerospace applications. Tin oxide was shown to be very stable at HT. We also measured a 2.5% change in electrical resistivity at room temperature at maximum membrane deflection. The maximum temperature coefficient of resistivity (TCR) is less than 3.5·10−4 K−1 in the temperature range between 25°C and 640°C. In addition to the device related research work, a novel reusable packaging concept is developed as housing is the main cost driver. After the chip is destroyed the functional device can simply be replaced — housing and contacts can be reused. The MEMS device is electrically contacted with a miniaturized spring mechanism. It is loaded from the harsh environment side into the HT stable metal housing. A cap is screwed into the housing and compresses the inserted seal ring against the chip. The part for electrical contacting on the opposite housing side is not disassembled. The MEMS device is not in direct contact with the housing material, but embedded between two adaptive layers of the same material as the device (sapphire) to decrease thermally induced mechanical stress. Overall weight is 46 g. This packaging concept has been successfully optimized so that the whole assembly can withstand 800°C and simultaneously provides sealing up to 250 bar! After testing in such harsh environment, the small packaging can still be unscrewed to exchange the MEMS device. Due to the reutilization, the packaging can be used far beyond the lifetime of HT MEMS devices.

We have fabricated microthruster chip pairs -one chip with microthruster structures such as injection capillaries, combustion chamber and nozzle, the other chip with platinum thin film devices such as resistance temperature detectors (RTDs) and a heater. The platinum thin film was sputtered on thermally oxidized silicon wafers WITHOUT adhesion layer. The effects of anneal up to 1050°C on the surface morphology of platinum thin films with varied geometry as well as with / without PECVD-SiO 2 coating were investigated in air and N 2 and results will also be presented. Electrical characterization of sensors was carried out in a furnace tube in which the sensors' temperature was varied between room temperature and 1000°C with a ramp of ±5Kmin -1 in air and N 2 . The experiments showed that the temperature-resistance characteristics of sensors had stabilized after the first heating up to 1000°C in N 2 . After stabilization the sensors underwent further 8 temperature cycles which correspond to over 28h of operation time between 800 -1000°C. To reduce the loss of combustion heat, chip material around the microthruster structures was partially removed. The effects of thermal insulation were investigated with microthruster chip pairs which were clamped together mechanically. The heater power was varied up to 20W and the temperature distribution in the chip pairs with / without thermal insulation was monitored with 7 integrated thin film sensors.