AFRL Cryogenic Technology Development Programs

This is an overview of the cryogenic refrigerator and cryogenic integration programs in development and characterization under the Cryogenic Technologies Group, Space Vehicles Directorate of the Air Force Research Laboratory (AFRL). The vision statement for the Air Force Research Laboratory Cryogenic Technologies Group is to support the space community as the center of excellence for developing and transitioning space cryogenic thermal management technologies. The primary customers for the AFRL cryogenic technology development programs are Ballistic Missile Defense Organization (BMDO), the USAF SBIRS (space based infrared) Low program office, and DoD space surveillance programs. This describes a variety of Stirling, pulse tube, Reverse Brayton, Joule-Thomson, and Sorption cycle cryocoolers currently under development to meet current and future Air Force and DoD requirements. The AFRL customer single stage cooling requirements at 10 K, 35 K, 60 K, 150 K, and multi-stage cooling requirements at 35/60 K are addressed. In order to meet these various requirements, the AFRL Cryogenic Technologies Group is pursuing various strategic cryocooler and cryogenic integration options. The Air Force Research Laboratory is also developing several advanced cryogenic integration technologies that will result in the reduction in current cryogenic system integration penalties and design time. These technologies include the continued development of the cryogenic systems integration model (CSIM), 60 K, and 100 K thermal storage units and heat pipes, cryogenic straps, thermal switches, and development of an integrated lightweight cryogenic bus (CRYOBUS).     

Future trends in space photovoltaics

The Air Force, NASA, NRL and the commercial sector are all using small spacecraft to a greater extent in order to provide more cost-effective access to space. This paper discusses the generic photovoltaic technologies which are being studied and/or developed to support these smaller spacecraft, and identifies several specific examples. The unique requirements of these mission types include lower power arrays, arrays with lower mass and stowed volume which will be more compatible with small launch vehicles, and power systems with lower fabrication costs     

A maintenance-free lead acid battery for inertial navigationsystems aircraft

Historically, aircraft inertial navigation system (INS) batteries have utilized vented nickel-cadmium batteries for emergency DC power. The United States Navy and Air Force developed separate systems during their respective INS developments. The Navy contracted with Litton industries to produce the LTN-72 and Air Force contracted with Delco to produce the Carousel IV INS for the large cargo and specialty aircraft applications, over the years, a total of eight different battery national stock numbers (NSNs) have entered the stock system along with 75 battery spare part NSNs. The standard hardware acquisition and reliability program is working with the Aircraft Battery Group at Naval Surface Warfare Center Crane Division, Naval Air Systems Command (AIR 536), Wright Laboratory, Battelle Memorial Institute, and Concorde Battery Corporation to produce a standard INS battery. This paper discusses the approach taken to determine whether the battery should be replaced and to select the replacement chemistry. The paper also discusses the battery requirements, aircraft that the battery is compatible with, and status of Navy flight evaluation. Projected savings in avoided maintenance in Navy and Air Force INS systems is projected to be $14.7 million per year with a manpower reduction of 153 maintenance personnel. The new INS battery is compatible with commercially sold INS systems which represents 66% of the systems sold     

High energy density regenerative fuel cell systems for terrestrialapplications

Regenerative Fuel Cell System (RFCS) technology for energy storage has been a NASA power system concept for many years. Compared to battery-based energy storage systems, RFCS has received relatively little attention or resources for development because the energy density and electrical efficiency were not sufficiently attractive relative to advanced battery systems. Even today, RFCS remains at a very low technology readiness level (TRL of about 2 indicating feasibility has been demonstrated). Commercial development of the Proton Exchange Membrane (PEM) fuel cells for automobiles and other terrestrial applications and improvements in lightweight pressure vessel design to reduce weight and improve performance make possible a high energy density RFCS energy storage system. The results from this study of a lightweight RFCS energy storage system for a remotely piloted, solar-powered, high altitude aircraft indicate an energy density up to 790 wh/kg with electrical efficiency of 53.4% is attainable. Such an energy storage system would allow a solar-powered aircraft to carry hundreds of kilograms of payload and remain in flight indefinitely for use in atmospheric research, Earth observation, resource mapping, and telecommunications. Future developments in the areas of hydrogen and oxygen storage, pressure vessel design, higher temperature and higher pressure fuel cell operation, unitized regenerative fuel cells, and commercial development of fuel cell technology will improve both the energy density and electrical efficiency of the RFCS     

Future trends in space power technology

The status of the US Air Force Space Power Research and Development Program is summarized. Generic issues and requirements affecting the strategic planning of space power advances for the 1990s and beyond are described. The major thrusts of the Air Fore part of the Strategic Defense Initiative Office Space Power Program are highlighted, with emphasis on the ongoing advanced component technology development program. The status of these component technologies in the areas of power sources, energy storage, power management and distribution, and thermal management is described. Technology projections for the full range of envisioned technology options for the foregoing are used as the basis for a series of point designs for deriving the subsystem- and system-level benefits of the technologies. The primary focus is on baseload (CW) power systems operating in the range from 100 W for small satellites to 50 kW for potential large surveillance satellites. The secondary focus is on large, multimegawatt pulsed power systems and related components for potential applications such as directed energy. Potential `trump card' technologies related to energy conversion, storage, power electronics, and thermal management are identified     

航空兵部队飞行安全评估系统研究与实践

根据航空兵部队飞行安全的特点,基于“人、机、环境“系统工程理论,并结合航空兵部队的实际,开发了一套航空兵部队飞行安全评估系统.该系统具有客观评估安全形势、发现薄弱环节和引导航空兵部队安全行为的功能.最后,给出了对航空兵部队进行飞行安全评估的应用实例.     

Open System Avionics Architectures

Over the last three years, Open System Avionics Architecture concepts have been addressed by the avionics community as a method for increasing affordability. The Naval Air Systems Command (Nav Air) led Advanced Avionics Architecture and Technology Review team of 1992, followed by the multiservice Avionics Engineering SubBoard (AESB) implementation phase team are two examples. The Perry memo and formation of the Open Systems Joint Task Force (OS-JTF) are further evidence of the importance placed on open systems at the DoD level. This paper summarizes these activities and their importance. Examples of the savings that can be expected by application of open systems are presented. Finally, significant on-going work along with critical technologies and concepts that need to be matured to make open systems successful are discussed     

高推重比发动机全权限数字电子控制系统研究和半物理仿真试验验证

以第4代战斗机的动力装置--高推重比发动机为控制对象,攻克了多项全权限数控系统的术,完成了高推重比发动机数控系统总体方案设计和多变量控制技术的工程化研究,适合多变量控制、轻质量、小体积的电子控制器和轻质量、小体积的机械液压装置的研制,以及高推重比发动机全权限数控系统的半物理仿真试验.     

Power Conditioning Systems for High-Power, Airborne, Pulsed Applications

The power conditioning portion of the high-power study that was performed for the Air Force Aeropropulsion Laboratory by the State University of New York at Buffalo is summarized. This effort defines the power conditioning system and critical component developments which will be required to interface the airborne 10-MW to 50-MW sources defined under separate study efforts with certain loads. Power conditioning systems are considered for use with magnetohydrodynamic generators and turbine driven alternators, both conventional and superconducting. The critical components required for each of the power conditioning systems are identified and then analyzed. The component analyses include estimations of development efforts necessary and of specific weights and volumes for components. The primary components considered are transformers (for alternator as well as for inverter use), switches, capacitors, and inductors. Weight algorithms are developed for each of the components. Following the component analyses, subsystems such as inverters and rectifier and filter packages are considered. The data for the various components and subsystems are then utilized for a comparison of the power conditioning techniques to be used with the various power sources. The weights and volumes of power conditioning systems for 8-point designs (8 variations of power, voltage, duty cycle, and total run time) are derived.     

Multi-computer VXIbus system set up and use

VXI has matured into a flexible bus architecture with which to develop various types of instrumentation systems. This paper details the multi-computer approach used in the VXI-based system that CACI developed for the Air Force. The system, the Engine Test/Trim Automated System II (ETTAS II) is designed to test: all Air Force jet engines. The paper discusses how to integrate multiple computers in a VXI-based system, including discussions on: setting up the computers; selecting register-based versus message-based computers; setting up and using shared-memory; defining and separating tasks for each computer. The shared memory discussion talks about different ways to structure the shared memory, including setting up a system-level “Current-Value Table” (CVT) for all instruments, as well as how other devices, including another computer can access the shared memory space. The paper shows how Commercial-Off-the-Shelf (COTS) software products NI-VXI, LabVIEW, and NI-VISA (National Instruments) can be used to satisfy all these requirements. The paper shows how the multi-computer approach can be cost-effective in many cases     

Electromechanical Actuation Technology for the All-Electric Aircraft

Electromechanical actuation is a critical element that must be developed and verified to make the all-electric aircraft a viable concept. For several years the Flight Control Division of the Air Force Wright Aeronautical Laboratories has sponsored activities to demonstrate the credibility of electromechanical actuation systems (EMAS) for primary flight control actuation functions. The foundation for these EMAS activities and several electromechanical actuation development programs are described here. One involves the design, fabrication, and laboratory test of a rotary, hingeline electromechanical actuator. Another involves the development and flight test demonstration of a linear electromechanical actuator for controlling an aileron of a C-141 aircraft. A third involves the design and development of a linear electromechanical actuator for missiles having severe performance, temperature, and volumetric requirements. In addition, a brief summary of the results from two aircraft actuation trade studies compare the baseline (conventional) hydraulic flight control system with an all-electric airplane concept including quantitative comparisons of weight, reliability and maintainability, and life cycle costs.     

Status of the Air Force nickel hydrogen low earth orbit life test

The US Air Force NiH₂ LEO (low earth orbit) life test consists of 200 cells undergoing real-time LEO cycling, pulse discharge testing, and storage testing. To date, three of the program's four objectives have been met: NiH₂ performance in LEO applications has been demonstrated. A significant number of cells have completed more than 20,000 cycles at 40% DOD. A database for cells of both 3.5 in. and 4.5 in. diameter has been generated. There have been no indications of any performance problems related to scaling up in terms of cell size. Initial data on the pulse discharge performance of a small number of cells has been demonstrated. Concerning the goal of achieving 20,000 cycles at 60% DOD, the data are mixed. Overall, it appears highly unlikely that cell designs such as those currently in the US Air Force test can achieve 20,000 cycles at 60%     

Potential defense applications of expert systems

The authors provide an overview of expert systems and how they may effect the development of future defense applications. Military uses of computers are outlined, and expert-systems fundamentals are described. Artificial research and development efforts by the military are examined, and potential military applications are discussed. Expert systems efforts at NASA, by the US Air Force, and for the Strategic Defence Initiative are considered     

US Air Force EarthRadar for detection and discrimination of buriedunexploded ordnance

The US Air Force EarthRadar system is a multi-purpose sensor designed and constructed using "radar" principles. This technology was originally developed for the US Air Force to detect buried unexploded ordnance (UXO). Bakhtar Associates developed the US Air Force EarthRadar technology under the DoD SBIR program. The system is capable of detecting buried metallic and non-metallic objects, including glass vials. In addition, the manner in which system hardware, signal processing, and the integrated high resolution global positioning system (GPS) are configured makes it ideal for applications such as mapping subsurface geological features, locating cavities and collapse features, and identifying contaminated ground     

试论教练装备空海军联合发展

阐述了美国空军和海军教练机装备发展现状,分析了美国空军和海军教练机装备联合发展的过程、原因以及优势,并结合我国空军和海军教练机的发展情况,得出我国空/海军教练机装备联合发展的几点启示。     

Causes of aircraft electrical failures

The results of a survey of data on failures of aircraft electronic and electrical components that was conducted to identify problematic components are reported. The motivation for the work was to determine priorities for future work on the development of accident investigation techniques for aircraft electrical components. The primary source of data was the Airforce Mishap Database, which is maintained by the Directorate of Aerospace Safety at Norton Air Force Base. Published data from the Air Force Avionics Integrity Program (AVIP) and Hughes Aircraft were also reviewed. Statistical data from these three sources are presented. Two major conclusions are that problems with interconnections are major contributors to aircraft electrical equipment failures, and that environmental factors, especially corrosion, are significant contributors to connector problems     

ATE enabling technologies: present and future

A discussion of the current and emerging core technologies and philosophies that will enable Air Force personnel to quickly, accurately and intuitively diagnose faults in increasingly complex systems     

ATE enabling technologies

A discussion of the current and emerging core technologies and philosophies that will enable Air Force personnel to quickly, accurately and intuitively diagnose faults in increasingly complex systems     

History of Time-Frequency Technology

Present-day collision avoidance systems (CAS) of the time-frequency variety employ modes of operation similar to those of airborne equipment which has been operating in military aircraft since 1959. A fleet operational evaluation of these systems began in 1961 in aircraft of U. S. Navy Helicopter Squadron HS-4, based on the aircraft carrier U.S.S. Yorktown. This equipment utilized a local clock in each aircraft, a separate time slot for each aircraft's interrogation signal, air-to-air coarse synchronization of all stations, and sufficient free-drift stability for time slot keeping. Operational use of one-way ranging with elimination of propagation delay offsets, higher clock stability for open-loop time keeping in the SNS-64 ... AN/APN-169 family of systems began in 1964 in U. S. Air Force C-130E turboprop aircraft. In 1965, use of the EROS I collision avoidance system began during flight testing of F-4 Phantom supersonic aircraft.