Search Results

Modern aircraft are aerodynamically designed at the edge of flight stability and therefore require high-response-rate flight control surfaces to maintain flight safety. In addition, to minimize weight and eliminate aircraft thermal cooling requirements, the actuator systems have increased power-density and utilize high-temperature components. This coupled with the wide operating temperature regimes experienced over a mission profile may result in detrimental performance of the actuator systems. Understanding the performance capabilities and power draw requirements as a function of temperature is essential in properly sizing and optimizing an aircraft platform. Under the Air Force Research Laboratory's (AFRL's) Integrated Vehicle and Energy Technology (INVENT) Program, detailed models of high performance electromechanical actuators (HPEAS) were developed and include temperature dependent effects in the electrical and mechanical actuator components.

The paper presents the results of a CFD study for predictions of ventilation characteristics and convective heat transfer within the Shuttle Orbiter middeck cabin in the presence of seven suited crewmember simulation and Individual Cooling Units (ICU). For two ICU arrangements considered, the thermal environmental conditions directly affecting the ICU performance have been defined for landing operation. These data would allow for validation of the ICU arrangement optimization.

Since flight requirements often necessitate last-minute re-analysis, it became crucial to develop flexible and comprehensive transport phenomena analysis software that would quickly ensure all vehicle and payload requirements would be satisfied. The software would replace various mainframe-based software, such as the Thermal Radiation Analyzer System (TRASYS) and the Systems Improved Numerical Differencing Analyzer (SINDA). The software would need to have the flexibility to employ models that could be developed and modified as vehicle systems change. By use of event files which contain simple, intuitive commands, the characteristics of individual missions could be built as inputs to the model. By moving the Environmental Control & Life Support (ECLS) system model to the PC environment, each analyst would have execution, storage, and processing management control. And of course, software portability would be greatly increased.

A flex hose assembly containing aqueous coolant from the International Space Station (ISS) Internal Active Thermal Control System (IATCS) consisting of a 2 foot section of Teflon hose and quick disconnects (QDs) and a Special Performance Checkout Unit (SPCU) heat exchanger containing separate channels of IATCS coolant and iodinated water used to cool spacesuits and Extravehicular Mobility Units (EMUs) were returned for destructive analyses on Shuttle return to flight mission STS-114. The original aqueous IATCS coolant used in Node 1, the Laboratory Module, and the Airlock consisted of water, borate (pH buffer), phosphate (corrosion control), and silver sulfate (microbiological control) at a pH of 9.5 ± 0.5.

The Centrifuge Accommodation Module (CAM) is designed to be one of the modules of the International Space Station (ISS) for performing on-orbit science experiments over an extended period of time. The common cabin air assembly (CCAA) is utilized as the hardware for air temperature and humidity control (THC) for the CAM module cabin. The CCAA unit contains a variable speed fan, heat exchanger, temperature control valve, water separator, temperature sensor, and electrical interface box. A temperature and humidity simulation model was developed to perform the THC analysis for the CCAA unit inside the CAM. This model applies both fixed control volume and a quasi-steady-state approach for computing critical information for evaluating/assessing CCAA system performance and capabilities.

The ISS (International Space Station) ITCS (Internal Thermal Control System) includes two internal coolant loops that utilize an aqueous based coolant for heat transfer. A silver salt biocide had previously been utilized as an additive in the coolant formulation to control the growth and proliferation of microorganisms within the coolant loops. Ground-based and in-flight testing demonstrated that the silver salt was rapidly depleted, and did not act as an effective long-term biocide. Efforts to select an optimal alternate biocide for the ITCS coolant application have been underway and are now in the final stages. An extensive evaluation of biocides was conducted to down-select to several candidates for test trials and was reported on previously.

The International Space Station (ISS) IATCS (Internal Active Thermal Control System) includes two internal coolant loops that use an aqueous based coolant for heat transfer. A silver salt biocide was used initially as an additive in the coolant formulation to control the growth and proliferation of microorganisms in the coolant loops. Ground-based and in-flight testing has demonstrated that the silver salt is rapidly depleted and not effective as a long-term biocide. Efforts are now underway to select an alternate biocide for the IATCS coolant loop with greatly improved performance. An extensive evaluation of biocides was conducted to select several candidates for test trials.

In August 1997 NASA/Marshall Space Flight Center (MSFC) began a test with the objective of monitoring the growth of microorganisms on material simulating the surface of the International Space Station (ISS) Temperature and Humidity Control (THC) Condensing Heat Exchanger (CHX). The test addressed the concerns of potential uncontrolled microbial growth on the surface of the THC CHX subsystem. For this study, humidity condensate from a closed manned environment was used as a direct challenge to the surfaces of six cascades in a test set-up. The condensate was collected using a Shuttle-type CHX within the MSFC End-Use Equipment Testing Facility. Panels in four of the six cascades tested were coated with the ISS CHX silver impregnated hydrophilic coating. The remaining two cascade panels were coated with the hydrophilic coating without the antimicrobial component, silver. Results of the fourteen-month study are discussed in this paper.

Excessive impact pressures can develop when an evacuated system is filled with liquid. Such a process is usually highly chaotic, especially when the system geometry is complex. Available computational methods by themselves cannot provide the necessary answers. The International Space Station (ISS) heat exchanger has a complex flow system, and a synthesis of computational and experimental methods was necessary to design the system. The FLOW-NET two-phase flow program was used to determine the range of loss coefficients and the liquid-vapor interface mass and energy transfer that would fit the measured impact pressures. These loss coefficients could then be used to compute the impact pressures for a design configuration similar to the one tested at a range of operating conditions.

The temperature and humidity of the air within the habitable areas of the International Space Station are controlled by a set of hardware and software collectively referred to as the Temperature and Humidity Control (THC) subassembly. This subassembly 1) controls the temperature of the cabin air based on a crew selected temperature, 2) maintains humidity within defined limits, and 3) generates a ventilation air flow which circulates through the cabin. This paper provides descriptions of the components of the THC subassembly, their performance ranges, and the control approach of the hardware. In addition, the solutions of the design challenges of maintaining a maximum case radiated noise level of NC 45, controlling the cabin air temperature to within ±2°F of a setpoint temperature, and providing a means of controlling microbial growth on the heat exchanger surfaces are described.