(Invited) High Temperature Smart Sensor Systems for Venus and Aerospace Applications

Abstract

Introduction Aerospace applications require a variety of sensing technologies to monitor conditions related to both space exploration and aerospace operations. In particular, a range of aerospace application require sensor system technology operational in high temperature, harsh environments beyond the range of standard commercial technology. This paper discusses the development of High Temperature Smart Sensor systems measuring a range of chemical species. A Smart Sensor System as described here implies the use of sensors combined with electronic processing capability and other supporting technologies. The approach has been to develop core technologies, esp. smart platforms and systems, for a range of applications [1]. Different sensing mechanisms (resistors, electrochemical cells, and Schottky diodes) are used to achieve selectivity to targeted species within a sensor array. A notable challenge is operation in high temperature, harsh environments, where both the core sensor technology and supporting hardware approach their operational limit. Two examples of high temperature chemical sensor system applications are measurements on the surface of Venus, and for aeronautic engine emissions applications. Venus Surface Measurements Exploration of the surface of Venus involves a number of formidable technical challenges. The surface temperature is 465°C with a 92 atmosphere caustic environment [2]. Nonetheless, due to recent advancements in high-temperature electronics and sensors, development has begun on a small probe system to operate on Venus surface for up to 60 days. This is in contrast with previous missions to the Venus surface, which had operated for no more than ~2 hours. This high temperature lander system, the Long-Lived In-Situ Solar System Explorer (LLISSE), includes multiple sensor technologies in order to measure the local conditions [3].In particular, planned for inclusion on the LLISSE lander is an array of high temperature chemical sensors. Leveraged from the development of a chemical sensors for applications such as emissions monitoring and fire detection, development is on-going of chemical sensor array able operate on the Venus surface for extended period of time [4]. For example, 4 chemical species sensors, carbon monoxide (CO), sulfur dioxide (SO2), carbonyl sulfide (OCS) and hydrogen fluoride (HF), have shown operation for 60 days in Venus simulated conditions. These sensors showed stable response and limited change in calibration over the test period. The SO2 sensor in particular responded multiple times to controlled boosts of SO2 into the chamber over the test period. Further, the HF sensor has been integrated with basic high temperature electronics and also shown operation in Venus simulated conditions. Planned development includes integration of a range of chemical sensors with increasingly complex electronics towards operation in lander probe system with signal conditioning electronic, power, and communications. Engine Emissions Monitoring The chemical signature detection of emissions from a propulsion system is understood to reflect the efficiency and health of the system. Development of a gas microsensor array for monitoring the emissions produced by an aircraft engine has been ongoing. This Engine Emissions Monitoring System (EEMS) is based on gas microsensor arrays to quantify composition of critical constituents in turbine engine exhaust products, e.g., oxygen, carbon monoxide, carbon dioxide, nitrogen oxide, and unburned hydrocarbons. The objective is to use this emissions information to assist in assessing the performance as well as the health state of the engine [5-6]. Each sensor element is miniaturized and fabricated using microfabrication techniques. This approach, when combined with electronics to form a Smart System is intended to for use in test stand applications or eventually for systems that can implemented on the vehicle for monitoring during flight. Demonstrations of this technology has shown, for example, the ability in a ground operational environment to detect the presence of a simulated engine oil leak and the deviation in a “Steady State” emissions profile suggestive of change in engine state during heavy volcanic ash deposition.It is suggested that small, smart rugged sensor system technologies are an enabling toward an “information age” in harsh environment applications. However, although high temperature Smart Sensor Systems can have a significant impact on a range of applications, extensive relevant demonstration testing is necessary for their long-term implementation.