This paper describes the application of intelligent sensors in the Integrated Systems Health Monitoring (ISHM) as applied to a rocket test stand. The development of intelligent sensors is attempted as an integrated system approach, i.e. one treats the sensors as a complete system with its own physical transducer, A/D converters, processing and storage capabilities, software drivers, self-assessment algorithms, communication protocols and evolutionary methodologies that allow them to get better with time. Under a project being undertaken at the NASA Stennis Space Center, an integrated framework is being developed for the intelligent monitoring of smart elements associated with the rocket tests stands. These smart elements can be sensors, actuators or other devices. Though the immediate application is the monitoring of the rocket test stands, the technology should be generally applicable to the ISHM vision. This paper outlines progress made in the development of intelligent sensors by describing the work done till date on Physical Intelligent sensors (PIS) and Virtual Intelligent Sensors (VIS).

The Central Arkansas Combustion Group has used a NASA EPSCoR grant to improve the instrumentation and control of its labscale hybrid rocket facility. The research group investigates fundamental aspects of combustion in hybrid rocket motors. This paper describes the new instrumentation, provides examples of measurements taken, and describes novel instrumentation which is in the process of development. A six degree-of-freedom thrust system measures the total work done during a burn to compare the efficiency of fuels and fuel additives. The new system measures the forces and moments in three spatial dimensions. An accurate measure of thrust oscillations will lead to better understanding of the cause and eventual minimization of the oscillations. Plume spectrometers are employed to determine and measure the reaction intermediates and products of combustion at the exhaust. The new control system features an oxygen mass flow controller, which allows the accurate measurement of the oxidant introduced into the motor.

The temperatures produced by the various components in the propulsion system of rockets and missiles determine the performance of the rocket. Since these temperatures occur very rapidly and under extreme conditions, standard thermocouples fail before any meaningful temperatures are measured. This paper describes the features of a special family of high performance thermocouples, which can measure these transient temperatures with millisecond response times and under the most severe conditions of erosion. Examples of igniter, propellant and rocket nozzle temperatures are included in this paper. Also included is heat flux measurements made by these sensors in rocket applications.

Structural Health Monitoring is essential in that any event that may compromise the solid rocket motor must be detected. The magnitude, position and time of any imposed event that may damage the propellant grain, bonding system or integrity of the case must be detected and identified for safe operation of the motor. The current embedded sensor technology has been developed to monitor the effect of these events on the propellant grain. Normal bond stress and temperature can be measured using DBST sensors and the output interpreted to confirm integrity. It has been shown that the presences of de-bond and cracks can be determined. Current work is in progress to establish if these embedded sensors can be used to determine position and size of such defects. The stress distribution in a typical propellant grain also has a shear component particularly near the ends and around any flaps, slots or stress relieving devices. This can be the critical stress under certain loads and in complex geometries. Therefore, a recent addition to the range is a sensor to measure shear stress in the same body as the DBST. Motors can be stored for long periods before being used so the sensor system must also be reliable and stable for at least twenty years of operation. Similar sensors stored for ten years have shown little change and tests are being undertaken to establish the confidence that the sensor system will last the life of the motor. This paper will review the recent development and testing of these embeddable sensors, and results to date will be discussed.

Many interesting structural and thermal events occur in materials that are housed within a surrounding pressure vessel. In order to measure the environment during these events and explore their causes instrumentation must be installed on or in the material. Transducers can be selected that are small enough to be embedded within the test material but these instruments must interface with an external system in order to apply excitation voltages and output the desired data. The methods for installing the instrumentation and creating an interface are complicated when the material is located in a case or housing containing high pressures and hot gases. Installation techniques for overcoming some of these difficulties were developed while testing a series of small-scale solid propellant and hybrid rocket motors at Marshall Space Flight Center. These techniques have potential applications in other test articles where data are acquired from materials that require containment due to the severe environment encountered during the test process. This severe environment could include high pressure, hot gases, or ionized atmospheres. The development of these techniques, problems encountered, and the lessons learned from the ongoing testing process are summarized.

Sierra Lobo tested its patented Cryo-Tracker(R) probe and Mass Gauging System in a large scale Expendable Launch Vehicle (ELV) liquid oxygen tank simulation for NASA. Typical Liquid Oxygen (LOX) tank operations were simulated at Lockheed Martin's Engineering Propulsion Laboratory in Denver, Colorado. The Cryo-Tracker(R) probe is 33 feet long, the longest built to date. It was mounted in the tank at only two locations, separated by 26 feet. Each test simulated typical Lockheed Martin booster pre-launch tanking operations, including filling the tank with LOX at fill rates typically used at the launch pad, and maintaining the fill level for a period representative of a typical pad hold. The Cryo-Tracker(R) Mass Gauging System was the primary instrument used for monitoring the fill and controlling the topping operations. Each test also simulated a typical flight profile, expelling the LOX at representative pressures and expulsion flow rates. During expulsion, the Cryo-Tracker(R) System served to generate an Engine Cut-Off (ECO) signal. Test objectives were as follows: Cryo-Tracker(R) data will be validated by flight-like propellant instruments currently used in launch vehicles; the probe will survive the harsh environment (which will be documented by a digital video camera) with no loss of signal or structural integrity; the system will successfully measure liquid levels and temperatures under all conditions and calculate propellant mass in real-time; the system will successfully demonstrate its feasibility as a control sensor for LOX filling and topping operations, as well as for engine cut-off. All objectives were met and the test results are presented.

Accurate and reliable multiphase flow measurements are needed for liquid propulsion systems. Existing volumetric flow meters are adequate for flow measurements with well-characterized, clean liquids and gases. However, these technologies are inadequate for multiphase environments, such as cryogenic fluids. Although, properly calibrated turbine flow meters can provide highly accurate and repeatable data, problems are still prevalent with multiphase flows. Limitations are thus placed on the applicability of intrusive turbine flow meters.

An accurate determination of fluid flow in a cryogenic propulsion environment is difficult under the best of circumstances. The extreme thermal environment increases the mechanical constraints, and variable density conditions create havoc with traditional flow measurement schemes. Presented here are secondary results of cryogenic testing of an all-optical sensor capable of a mass flow measurement by directly interrogating the fluid's density state and a determination of the fluid's velocity. The sensor's measurement basis does not rely on any inherent assumptions as to the state of the fluid flow (density or otherwise). The fluid sensing interaction model will be discussed. Current test and evaluation data and future development work will be presented.

High temperature sensors and electronics are necessary for a number of aerospace propulsion applications. The Sensors and Electronics Branch at NASA Glenn Research Center (NASA GRC) has been involved in the design, fabrication, and application of a range of sensors and electronics that have use in high temperature, harsh environment propulsion environments. The emphasis is on developing advanced capabilities for measurement and control of aeropropulsion systems as well as monitoring the safety of those systems using Micro/Nano technologies. Specific areas of work include SiC based electronic devices and sensors; thin film thermocouples, strain gauges, and heat flux gauges; chemical sensors; as well as integrated and multifunctional sensor systems. Each sensor type has its own technical challenges related to integration and reliability in a given application. These activities have a common goal of improving the awareness of the state of the propulsion system and moving towards the realization of intelligent engines. This paper will give an overview of the broad range of sensor-related development activities on-going in the NASA GRC Sensors and Electronics Branch as well as their current and potential use in propulsion systems.

The desire to explore the Moon and Mars by 2030 makes cost effective and low mass health monitoring sensors essential for spacecraft development. Parameters such as impact, temperature, and radiation fluence need to be measured in order to determine the health of a human occupied vehicle. A phosphor-based sensor offers one good approach to develop a robust health monitoring system. The authors have spent the last few years evaluating physical characteristics of zinc sulfide (ZnS) phosphors. These materials emit triboluminescence (TL) which is fluorescence produced as a result of an impact. Currently, two ZnS materials have been tested for impact response for velocities from 1 m/s to 6 km/s. These materials have also been calibrated for use as temperature sensors from room temperature to 350 °C. Finally, any sensor that is intended to function in space must be characterized for response to ionizing radiation. Research to date has included irradiating ZnS with 3 MeV protons and 20 keV electrons, which are likely components of the space radiation environment. Results have shown that that the fluorescence emission intensity decreases with radiation fluence. However, radiation induced damage can be annealed at small fluence levels. This annealing not only increased light intensity of the exposed sample from excitation but also TL excitation as well.

Hydrogen is becoming an increasingly important fuel source as fossil fuel supplies decline. The low explosive limit of hydrogen makes leak detection a priority when dealing with this fuel. In an effort to support the use of hydrogen, a chemochromic sensor has been developed which is robust, simple to use, and does not require active operation. It can be made into a thin film or tape which can be conveniently used for leak detection at unions, valves, or outlets. There are two forms of the sensor, a reversible and an irreversible, allowing a variety of applications based on individual situations. The irreversible sensor is useful during hazardous operations when personnel cannot be present, while the reversible is ideal for monitoring the status of a leak in person or via a camera. Testing the irreversible sensor against environmental effects has been completed and results indicate this material is suitable for outdoor use in the harsh beachside environment of Kennedy Space Center. The environmental testing has led to increased sensitivity of the irreversible chemochromic sensor. In an effort to advance this technology further, this chemochromic sensor will be integrated into a sensor system using an electrical or optical signal.

Surface acoustic wave (SAW) devices are attractive for sensing of the physical, gas, liquid or biological environment because the device has many parameters which can be adjusted for various applications. The temperature coefficient of delay can provide temperature sensing, coupling to liquids, gases or applied films can be controlled by choice of mode, and putting the device under stress or strain can measure pressure or vibration. In addition, there are many substrate choices to attempt to optimize a given measurand. Finally, substrate choices allow sensing from cryogenic to high temperatures (1000°C), which has the potential for use in a wide spectrum of space applications. This paper will describe a novel SAW sensor platform for sensing of various measurands which is passive and wireless, and has several levels of coding available for providing identification. The paper will describe the concept of orthogonal frequency coding used in the device identification and its advantages in communications and sensing, and the mechanism for implementation using reflectors in a SAW sensor. Results of measured SAW device performance versus the coupling of mode (COM) model predictions show excellent correlation for a 250 MHz device on a lithium niobate substrate. The approach presented uses frequency selective reflectors in a differential delay line to measure temperature; measured from cryogenic temperatures to 150°C with the same device. A discussion of substrate materials and device parameters will be presented to exemplify the versatility and practicality of these devices to a wide range of sensor applications.

A slip ring is a rotary electrical interface, collector, swivel or joint. It is a component or architecture that can perform continuous data transfer between a rotary and stationary structure. A few of the numerous approaches for transferring data include contact and non-contact methods which use wires, radio waves, optical fibers and even liquid as the transfer media. However, they all suffer inherent drawbacks in durability, reliability, stability, electromagnetic interference and speed. The system introduced in this paper alleviates many of these issues by employing a wireless through the air optical solution.

The valve monitoring system is a stand alone unit with network capabilities for integration into a higher level health management system. The system is designed for aiding in failure predictions of high-geared ball valves and linearly actuated valves. It performs data tracking and archiving for identifying degraded performance. The data collection types are: cryogenic cycles, total cycles, inlet temperature, outlet temperature, body temperature, torsional strain, linear bonnet strain, preload position, total travel, and total directional changes. Events are recorded and time stamped in accordance with the IRIG B True Time. The monitoring system is designed for use in a Class 1 Division II explosive environment. The basic configuration consists of several instrumentation sensor units and a base station. The sensor units are self contained microprocessor controlled and remotely mountable in three by three by two inches. Each unit is potted in a fire retardant substance without any cavities and limited to low operating power for maintaining safe operation in a hydrogen environment. The units are temperature monitored to safeguard against operation outside temperature limitations. Each contains 902-928 MHz band digital transmitters which meet Federal Communication Commissions requirements and are limited to a 35 foot transmission radius for preserving data security. The base-station controller correlates related data from the sensor units and generates data event logs on a compact flash memory module for database uploading. The entries are also broadcast over an Ethernet network. Nitrogen purged National Electrical Manufactures Association (NEMA) Class 4 Enclosures are used to house the base-station.

This manuscript includes information from test evaluations and development of a smart event detection system for use in monitoring composite rocket motor cases for damaging impacts. The primary purpose of the system as a sentry for case impact event logging is accomplished through; implementation of a passive network of miniaturized piezoelectric sensors, logger with pre-determined force threshold levels, and analysis software. Empirical approaches to structural characterizations and network calibrations along with implementation techniques were successfully evaluated, testing was performed on both unloaded (less propellants) as well as loaded rocket motors with the cylindrical areas being of primary focus. The logged test impact data with known physical network parameters provided for impact location as well as force determination, typically within 3 inches of actual impact location using a 4 foot network grid and force accuracy within 25%of an actual impact force. The simplistic empirical characterization approach along with the robust / flexible sensor grids and battery operated portable logger show promise of a system that can increase confidence in composite integrity for both new assets progressing through manufacturing processes as well as existing assets that may be in storage or transportation.

Current and future requirements of aerospace sensors and transducers demand the design and development of a new family of sensing devices, with emphasis on reduced weight, power consumption, and physical size. This new generation of sensors and transducers will possess a certain degree of intelligence in order to provide the end user with critical data in a more efficient manner. Communication between networks of traditional or next-generation sensors can be accomplished by a Wireless Sensor Network (WSN) developed by NASA's Instrumentation Branch and ASRC Aerospace Corporation at Kennedy Space Center (KSC), consisting of at least one central station and several remote stations and their associated software. The central station is application-dependent and can be implemented on different computer hardware, including industrial, handheld, or PC-104 single-board computers, on a variety of operating systems: embedded Windows, Linux, VxWorks, etc. The central stations and remote stations share a similar radio frequency (RF) core module hardware that is modular in design. The main components of the remote stations are an RF core module, a sensor interface module, batteries, and a power management module. These modules are stackable, and a common bus provides the flexibility to stack other modules for additional memory, increased processing, etc. WSN can automatically reconfigure to an alternate frequency if interference is encountered during operation. In addition, the base station will autonomously search for a remote station that was perceived to be lost, using relay stations and alternate frequencies. Several wireless remote-station types were developed and tested in the laboratory to support different sensing technologies, such as resistive temperature devices, silicon diodes, strain gauges, pressure transducers, and hydrogen leak detectors.

Microwave and Synthetic Aperture Radar antenna systems have been developed as instrument systems using truss structures as their primary support and deployment mechanism for over a decade. NASA Langley Research Center has been investigating fabrication, modular assembly, and deployment methods of lightweight rigidizable/inflatable linear truss structures during that time for large spacecraft systems. The primary goal of the research at Langley Research Center is to advance these existing state-of-the-art joining and deployment concepts to achieve prototype system performance in a relevant space environment. During 2005, the development, fabrication, and testing of a 6.7 meter multi-bay, deployable linear truss was conducted at Langley Research Center to demonstrate functional and precision metrics of a rigidizable/inflatable truss structure. The present paper is intended to summarize aspects of bonded joint technology developed for the 6.7 meter deployable linear truss structure while providing a brief overview of the entire truss fabrication, assembly, and deployment methodology. A description of the basic joint design, surface preparation investigations, and experimental joint testing of component joint test articles will be described. Specifically, the performance of two room temperature adhesives were investigated to obtain qualitative data related to tube folding testing and quantitative data related to tensile shear strength testing. It was determined from the testing that a polyurethane-based adhesive best met the rigidizable/inflatable truss project requirements.

Many developments in the field of multisensor array (MSA) transducers have taken place in the last few years. Advancements in fabrication technology, such as Micro-Electro-Mechanical Systems (MEMS) and nanotechnology, have made implementation of MSA devices a reality. NASA Kennedy Space Center (KSC) has been developing this type of technology because of the increases in safety, reliability, and performance and the reduction in operational and maintenance costs that can be achieved with these devices. To demonstrate the MSA technology benefits, KSC quantified the relationship between the number of sensors (N) and the associated improvement in sensor life and reliability. A software algorithm was developed to monitor and assess the health of each element and the overall MSA. Furthermore, the software algorithm implemented criteria on how these elements would contribute to the MSA-calculated output to ensure required performance. The hypothesis was that a greater number of statistically independent sensor elements would provide a measurable increase in measurement reliability. A computer simulation was created to answer this question. An array of N sensors underwent random failures in the simulation and a life extension factor (LEF equals the percentage of the life of a single sensor) was calculated by the program. When LEF was plotted as a function of N, a quasiexponential behavior was detected with marginal improvement above N = 30. The hypothesis and follow-on simulation results were then corroborated experimentally. An array composed of eight independent pressure sensors was fabricated. To accelerate sensor life cycle and failure and to simulate degradation over time, the MSA was exposed to an environmental tem-perature of 125°C. Every 24 hours, the experiment's environmental temperature was returned to ambient temperature (27°C), and the outputs of all the MSA sensor elements were measured. Once per week, the MSA calibration was verified at five different pressure points. Results from the experiment correlated with the results obtained in the computer simulation, in which the overall LEF of the MSA transducer was extended. Furthermore, it was concluded that the MSA approach was capable of extending calibration cycle times at least three times when compared to single-element transducers. These characteristics provided not only an increase in sensor reliability but also a reduction in operational and maintenance costs.

Integrated System Health Management (ISHM) capability for rocket propulsion testing is rapidly evolving and promises substantial reduction in time and cost of propulsion systems development, with substantially reduced operational costs and evolutionary improvements in launch system operational robustness. NASA Stennis Space Center (SSC), along with partners that includes NASA, contractor, and academia; is investigating and developing technologies to enable ISHM capability in SSC's rocket engine test stands (RETS). This will enable validation and experience capture over a broad range of rocket propulsion systems of varying complexity. This paper describes key components that constitute necessary ingredients to make possible implementation of credible ISHM capability in RETS, other NASA ground test and operations facilities, and ultimately spacecraft and space platforms and systems: (1) core technologies for ISHM, (2) RETS as ISHM testbeds, and (3) RETS systems models.

This paper outlines the present design approach for the Ethernet-Based Smart Networked Elements (SNE) being developed by NASA's Instrumentation Branch and the Advanced Electronics and Technology Development Laboratory of ASRC Aerospace Corporation at Kennedy Space Center (KSC). The SNEs are being developed as part of the Integrated Intelligent Health Management System (IIHMS), jointly developed by Stennis Space Center (SSC), KSC, and Marshall Space Flight Center (MSFC). SNEs are sensors/actuators with embedded intelligence, capable of networking among themselves and with higher-level systems (external processors and controllers) to provide not only instrumentation data but also associated data validity qualifiers. NASA KSC has successfully developed and preliminarily demonstrated this new generation of SNEs. SNEs that collect pressure, strain, and temperature measurements (including cryogenic temperature ranges) have been developed and tested in the laboratory and are ready for demonstration in the field.

The health of electromechanical systems (actuators) and specifically of solenoid valves is a primary concern at Kennedy Space Center (KSC). These systems control the storage and transfer of such commodities as liquid hydrogen. The potential for the failure of electromechanical systems to delay a scheduled launch or to cause personnel injury requires continual maintenance and testing of the systems to ensure their readiness. Monitoring devices need to be incorporated into these systems to verify the health and performance of the valves during real operating conditions. It is very advantageous to detect degradation and/or potential problems before they happen. This feature will not only provide safer operation but save the cost of unnecessary maintenance and inspections. Solenoid valve status indicators are often based upon microswitches that work by physically contacting a valve's poppet assembly. All of the physical contact and movement tends to be very unreliable and is subject to wear and tear of the assemblies, friction, breakage of the switch, and even leakage of the fluid (gas or liquid) in the valve. The NASA Instrumentation Branch, together with its contractor, ASRC Aerospace, has developed a solenoid valve smart current signature sensor that monitors valves in a noninvasive mode. The smart system monitors specific electrical parameters of the solenoid valves and detects and predicts the performance and health of the device. The information obtained from the electrical signatures of these valves points to not only electrical components failures in the valves but also mechanical failures and/or degradations.

To meet the demand for more reliable sensory data, longer sensor calibration cycles, and more useful information for operators at NASA's Kennedy Space Center (KSC), NASA's Instrumentation Branch and ASRC's Advanced Electronics and Technology Development Laboratory at the KSC are developing custom intelligent sensors based on the IEEE 1451 family of smart-sensor standards. The KSC intelligent sensors are known as Smart Networked Elements (SNEs), and each SNE includes transducers and their associated Transducer Electronic Data Sheets (TEDS), signal conditioning, analog-to-digital conversion, software algorithms for performing health checks on the data, and a network connection for sending data to other SNEs and higher-level systems. The development of the SNE has led to the definition of custom architectures, protocols, IEEE 1451 implementations, and TEDS, which are presented in this paper. The IEEE 1451 standards describe the architecture, message formats, software objects, and communication protocols within the smart sensor. Because of the standard's complexity, KSC has simplified the IEEE 1451 architecture and narrowed the scope of software objects to be included in the SNE to create a "light" IEEE 1451 implementation, and has used the manufacturer-defined TEDS to customize the SNE with health indicators. Furthermore, KSC has developed a protocol that allows the SNEs to communicate over an Ethernet network while reducing bandwidth requirements.

Autonomous on-board orbit control was developed, first and foremost, to improve orbital operations, principally by reducing operations costs. It accomplishes this improvement by eliminating the planning burden on the mission operations team. In addition, because the orbit phase and other orbital elements are held invariable, the position of the spacecraft is known at all future times, and a new array of mission applications is opened up, especially related to communications, mission planning, installation, maintenance, and hazard avoidance. Another significant benefit is a reduction in orbit maintenance propellant.

As the deformation in nozzle will cause thrust miss aligned and other problems which would degrade the performance of rocket severely, deformation detection will help to correct the ballistic parameters for control and guide of the rocket. Prior or real time detection is important for calculate the ballistic parameters. Rocket noise in active period during rocket launch has close relationship with core length in the exhausted jet flow. The core length depends on the nozzle structure and the combustion situation inside chamber. If the parameters inside chamber are fixed, the core length could be determined by nozzle structure. Thus the jet noise would reflect the change in nozzle structure. Experiments with cold jet flow were conducted to explore the relationship between nozzle deformation and the spectrum pattern of jet noise. Three groups of nozzles with different expansion ratio, length of expand segment, and throat structure were used in the experiment. The spectrums of jet noise for each nozzle under different chamber pressure were obtained as a reference to detect the deformation in nozzles. Then the nozzle was deformed artificially and the jet noise was analyzed by joint time-frequency analysis (JTFA) method. Several JTFA algorithms are used to process the noise data. The joint time-frequency distribution pattern reflects the change in nozzle structure.

The plume of solid rocket motor is a high velocity flow with high temperature. Temperature distribution in the plume is of great interest for analyzing the compatibility of rocket weapon system. The high temperature exhausted flow field would cause damage on certain equipment and loading vehicles. An instantaneous temperature field with sharp step is established by the exhausted flow field of rocket motor. The increasing rate of the step depends on the flow velocity at cross section of nozzle exit. To perform an accurate measurement of temperature inside the flow field, a thermocouple must be sturdy enough to endure the flow impingement. In the meantime, the thermocouple must have a short time constant to trace the temperature fluctuation in flow field and a small size to avoid disturbing the flow field severely. The dynamic performance of the thermocouples used in exhausted flow temperature measurement must be evaluated before the experiment. The thermocouple which can be used in measuring the temperature distribution in rocket plume was presented in this paper. A NAMNAC^(R) self-renew-erode thermocouples with a nominal time constant of 10 microseconds was used as a reference in a dynamic calibration test for this kind of thermocouple. The thermocouple could trace the temperature increase in the exhausted flow perfectly. This kind of thermocouples was used in several real tests of rocket motors, such as the temperature in free exhausted flow field of a stationary rocket motor test, the stagnate temperature in a shock flow field during the launching of a rocket, and the temperature in a launch tube.

This paper describes initial work to develop an optical system to detect small concentrations, less than 1 ppm, of chemical or biological agents by monitoring the fluorescence emission from a hollow optical fiber. This class of sensors would enable highly sensitive detection of chemical or biological agents by a small and lightweight sensor. The sensors would also be readily adaptable to different types of analyte by changing the fluorescent coating. Hollow core optical fibers can be filled with a sol-gel matrix that incorporates a fluorophor. Current work has established the sensitivity of an amine dye to weak concentrations of formaldehyde. Formaldehyde can be introduced into a spacecraft crew environment by out-gassing, crew activities, experimental payloads, and human and bacterial metabolism. Formaldehyde is an important trace contaminant to monitor because it is detrimental in small doses and long term exposure to low concentrations causes hypersensitivity. These issues become increasingly important in a closed-loop environment such as the crew habitat for astronauts on a long term mission.

Hydrazine is mostly used as a propellant in the control/propulsion system of missiles, spacecraft and satellites. However with its highly toxic and strong reducing nature, hydrazine is very dangerous to humans and the environment. In this research, a low cost, passive, and highly sensitive micro-sensor has been developed as an alarm device for real-time monitoring for the accidental release of hydrazine, and to insure the safety of personnel and the readiness of the system before lift-off. The micro-sensor is fabricated using standard microelectronic manufacturing techniques and is composed of interdigitated electrodes and a hydrazine-sensitive poly (3-hexylthiophene) (P3HT) thin film. When exposed to 1ppm of hydrazine gas, the compensation interaction between the reducing hydrazine gas and p-type doped P3HT leads to a five order magnitude increase in the resistance of the device. The sensor is capable of detecting hydrazine leaks from tens of ppb to tens of ppm concentration. The sensitivity of sensor increases with the increasing of hydrazine concentration and the decreasing of the polymer film thickness. A numerical simulation result based on the possible theoretical model is compared with the experimental data, which shows a good agreement.

Pressure sense lines, as employed in the measurement of rocket engine test firings, can propagate the time-domain pressure signal out of hostile regions and allow instrumentation with pressure transducers. In such applications, it is necessary to correct the data to account for attenuation and resonance due to the sense line. One technique for doing so is the application of Fourier transform theory to obtain the transfer function of the sense line. Various techniques for obtaining the transfer function are explored, including the use of Gaussian noise, single frequency sweeps, and impulse signals as input functions. The transfer function thus obtained is mathematically fit, scaled, and validated against a related system.

Laser power beaming permits radical improvements in spacecraft performance, and may be superior to nuclear power for some missions, including a lunar base. Recent developments in laser and large-optics technology make a laser power beaming infrastructure for space both more practical and easier to develop. In particular, Diode Pumped Alkali Laser (DPAL) technology appears ideally suited to power beaming at the 0.1 - 1 MW level. This paper discusses a possible architecture for such a power beaming infrastructure using ground-based lasers and geosynchronous relays.