SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 13 - JULY 1, 2005
05 AIRCRAFT DESIGN, TESTING AND PERFORMANCE, PART I
Includes all stages of design of aircraft and aircraft structures and systems.
Also includes aircraft testing, performance, and evaluation, and aircraft and flight simulation technology.
For related information see also 18 Spacecraft Design, Testing and Performance; and 39 Structural Mechanics.
For land transportation vehicles see 85 Technology Utilization and Surface Transportation.
20050177320 Mercury Computer Systems, Inc., Chelmsford, MA USA
Processing Challenges in Shrinking HPEC Systems into Small UAVs
Pearce, Stephen; Jaenicke, Richard; Sep. 2004; 24 pp.; In English; Original contains color illustrations Report No.(s): AD-A433160; No Copyright; Avail: Defense Technical Information Center (DTIC)
The best-known unmanned aerial vehicles (UAVs), Predator and Global Hawk, are large, multi-million dollar aircraft managed as theater/national assets. With synthetic aperture radar (SAR), electro-optic/infrared (EO/IR), and signals intelligence (SIGINT) payloads, these UAVs have proven their worth in battlefields from Bosnia to Afghanistan and Iraq. This success has led to a surge in proposed UAV missions and designs using a layered approach with multiple classes of UAVs to provide persistent narrow and wide ISR (intelligence, surveillance, reconnaissance) coverage. Programs such as the Future Combat System (FCS) include a large role for tactical UAVs, small UAVs, and unmanned ground vehicles (UGVs). The smaller, cheaper unmanned vehicles can be deployed at the brigade or company level to see over the next hill. With many vehicles and many sensors, network bandwidth becomes an issue. So future UAVs will include aided/automatic target recognition (AiTR/ATR) capabilities to reduce both communication bandwidth and latency. Large UAVs such as Global Hawk and Predator have been successful using today’s HPEC solutions. Global Hawk currently uses a 9U VME system with PowerPC processors for SAR and EO/IR processing, while the Predator is a bit smaller, using a 6U VME system for TESAR processing. The challenge is to provide similar processing power for much smaller UAVs, many of which have less than 1/2 the payload weight and 1/4 the volume of the Predator. This presentation will provide a detailed set of trade-offs in computational capabilities, I/O capabilities, and memory capacities distributed between FPGAs and Power PCs for sample applications of SAR image formation and SIGINT channelized receiver throughout. DTIC
Computer Programming; Drone Vehicles; Miniaturization; Pilotless Aircraft
20050177341 Air Force Inst. of Tech., Wright-Patterson AFB, OH USA
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Feasibility of Requalifying Yokota C-130s as Airland Only
Bauer, Michael J.; Jun. 2000; 86 pp.; In English; Original contains color illustrationsReport No.(s): AD-A433205; AFIT/GMO/ENS/00E-01; No Copyright; Avail: Defense Technical Information Center (DTIC)
In 1997, the Air Mobility Command Commander convened a Tiger Team to develop a road map for C-130s. The command was concerned the C-130 was spending too much time training for its airdrop mission and not enough time flying revenue generating Transportation Working Capital Fund (TWCF) missions. Despite this concern, one of the primary recommendations in the Tiger Team report was to keep all C-130 aircrews 100% formation airdrop and airland qualified. The purpose of this paper is to examine the feasibility and impact of eliminating the airdrop qualification of C-130 aircrews at Yokota AB Japan. The paper investigates three questions in exploring this research problem. The first investigative question examines the feasibility of combat delivery C-130s meeting wartime requirements if Yokota is requalified as airland only. The second investigative question examines if requalifying Yokota C-130s risks the Pacific TWCF and Joint Airborne/Air Transportability Training (JA/ATT) peacetime requirements. The final investigative question examines the impact requalifying Yokota has on training requirements and whether or not Yokota needs to fence training aircraft. In the end, the paper concludes that it is feasible to requalifying Yokota as airland only. The theater Commander in Chief (CINC) still has an effective force to meet all wartime requirements and an increased capability to meet peacetime requirements. At the same time, the requirements are met more efficiently, as savings are realized through reduced training and deployment costs. DTIC
Air Drop Operations; Jet Aircraft; Military Operations; Short Takeoff Aircraft; Training Aircraft; Transport Aircraft
20050177346 Air Force History Support Office, Bolling AFB, Washington, DC USA
Acquisition Management in the USA Air Force and its Predecessors
Benson, Lawrence R.; Jan. 1997; 64 pp.; In English Report No.(s): AD-A433213; No Copyright; Avail: CASI; A04, Hardcopy
Summarizes how the Air Force and its predecessors organized the process of acquiring the aircraft and other systems to help fight the nation’s armed conflicts and ultimately prevail in the Cold War. DTIC
Acquisition; Industries; Management Planning; United States
20050177359 RAND Corp., Santa Monica, CA USA
The Air Force Chief of Staff Logistics Review. Improving Wing-Level Logistics
Lynch, Kristin F.; Drew, John G.; George, David; Tripp, Robert S.; Roll, C. R., Jr.; Leftwich, James; Jan. 2005; 200 pp.; In English Contract(s)/Grant(s): F49642-01-C-0003 Report No.(s): AD-A433235; No Copyright; Avail: CASI; A09, Hardcopy
In response to indicators of declining readiness, heightened operations tempo, and evolving force employment concepts, the Chief of Staff of the Air Force (CSAF) initiated a review of Air Force wing-level logistics processes. This review, called the Chiefs Logistics Re- view (CLR), was designed to target process and process-enabler short falls that limited the logistics community’s ability to meet increasing readiness demands. This report presents background information and describes the analytic approach (including the RAND corporation’s role in its development) and results of CLR (Phase 1), and it describes how solution options designed to improve wing-level logistics processes were tested and evaluated (Phase 2). This effort was unlike a typical RAND study in that it was a joint effort, with RAND acting as an analytic advisor to the Air Force. RAND was chosen to develop the analytic approach for this review because of its previous research and the confidence of senior Air Force leaders. RAND’s involvement was meant to ensure that the CSAF received all potential options and a costs/benefits analysis for each option. The primary catalyst for CLR was a briefing sponsored by Gen John P. Jumper, then Commander, USA Air Forces Europe (USAFE/CC), in September 1999. Entitled ‘Posturing Aircraft Maintenance for Combat Readiness’ and stemming in part from experiences during Operation Allied Force/Operation Noble Anvil, the briefing illustrated declining readiness trends, degraded warfighting skills, and impaired Air and Space Expeditionary Force (AEF) implementation. DTIC
Combat; Logistics; Maintainability; Maintenance; Wings
20050177364 Washington Univ., Saint Louis, MO USA
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Mathematical and Computational Framework for Virtual Fabrication Environment for Aircraft Components
Szabo, Barna; Nervi, Sebastian; Muntges, Daniel; Jan. 2001; 45 pp.; In English Contract(s)/Grant(s): F49620-01-1-0074 Report No.(s): AD-A433240; AFRL-SR-AR-TR-05-0155; WUCCM-05-01; No Copyright; Avail: CASI; A03, Hardcopy
The general objective of this project was to investigate the question of how working models should be formulated so that they can serve as reliable and accurate representations of physical reality in the sense that they will provide predictions of events or states of systems that can be confirmed consistently by physical observations. The construction of such mathematical models involves feedback processes, the main elements of which are calibration, prediction, evaluation and modification. The specific objective was the development of the mathematical and computational aspects of a knowledge base needed for the creation of a virtual fabrication environment for aircraft components manufactured from 705O-T7451 aluminum plate stock so that the incidence of re-working and scrapping of partially or fully manufactured parts is substantially reduced The main conclusions are that verified mathematical models can be used successfully for the determination of residual stress states in 7050-T7451 aluminum plates and this information can be used for the prediction of distortion in thin-walled structural components with a high degree of reliability. The use of virtual and physical experiments in engineering decision-making processes is discussed and illustrated by examples. DTIC
Aircraft Equipment; Fabrication; Mathematical Models
20050177457 Massachusetts Inst. of Tech., Lexington, MA USA
Deployment of SAR and GMTI Signal Processing on a Boeing 707 Aircraft Using pMatlab and a Bladed Linux Cluster
Kepner, Jeremy; Currie, Tim; Kim, Hahn; McCabe, Andrew; Mathew, Bipin; Moore, Michael; Rabinkin, Dan; Reuther, Albert; Rhoades, Andrew; Travinin, Nadya; Tella, Lou; Sep. 2004; 30 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): F19628-00-C-0002 Report No.(s): AD-A433396; No Copyright; Avail: Defense Technical Information Center (DTIC)
The Lincoln Multifunction Intelligence, Surveillance and Reconnaissance Testbed (LiMIT) is an airborne research laboratory for development, testing, and evaluation of sensors and processing algorithms. During flight tests it is desirable to process the sensor data to validate the sensors and to provide targets and images for use in other on-board applications. Matlab is used for this processing because of the rapidly changing nature of the algorithms, but requires hours to process the required data on a single workstation. The pMatlab and MatlabMPI libraries allow these algorithms to be parallelized quickly without porting the code to a new language. The availability of inexpensive bladed Linux clusters provides the necessary parallel hardware in a reasonable form factor.We have integrated pMatlab and a 28 processor IBM Blade system to implement Ground Moving Target Indicator (GMTI) processing and Synthetic Aperture Radar (SAR) processing on board the LiMIT Boeing 707 aircraft. GMTI processing uses a simple round robin approach and is able to achieve a speedup of 18x. SAR processing uses a more complex data parallel approach, which involves multiple ‘corner turns’ and is able to achieve a speedup of 12x. In each case, the required detections and images are produced in under five minutes (as opposed to one hour), which is sufficient for in-flight action to be taken. DTIC
Airborne Equipment; Boeing 707 Aircraft; Deployment; Moving Target Indicators; Parallel Processing (Computers); Signal Processing; Synthetic Aperture Radar; Test Stands; Unix (Operating System)
20050177527 Defence Science and Technology Organisation, Victoria, Australia
Modelling of Stable Tearing in Aircraft Structures
Liu, Q.; Hamel, P.; Hu, W.; Sharp, P. K.; Lahousse, A.; Clark, G.; Mar. 2005; 94 pp.; In English; Original contains color illustrations Report No.(s): AD-A433497; DSTO-TR-1657; DODA-AR-013-350; No Copyright; Avail: Defense Technical Information Center (DTIC)
This report summarises the cooperative research program on stable tearing between DSTO and CEAT. The main objective was to study the conditions under which aircraft materials fracture by stable tearing and to develop a predictive capability for the process under operational conditions. The experiments on both CCT and CT specimens were to assist in validation of numerical modelling. Tear bands were successfully reproduced on CCT specimens with different specimen thickness by experiments at CEAT. The results were used to assess empirical models - Schijve’s and Forsyth’s models, and R-curve methods as well. Stable tearing feature was successfully simulated by a commercial finite element package ZENCRACK. Due to lack of local failure criteria, ZENCRACK cannot be used to predict whether stable tearing would occur or arrest under cyclic loading. But it appears to be useful for modeling such phenomena for indicative purpose only. A new 3D numerical model was proposed using a cohesive zone approach. This model can predict features similar to stable tearing and agrees well with the published experimental data. However, more research work needs to be done. DTIC
Airframes; Crack Propagation; Tearing
20050177555 California Univ., Davis, CA USA
Neural Network Control of a Parallel Hybrid-Electric Propulsion System for a Small Unmanned Aerial Vehicle
Harmon, Frederick G.; Jan. 2005; 283 pp.; In English; Report No.(s): AD-A433531; CI04-1076; No Copyright; Avail: CASI; A13, Hardcopy
Parallel hybrid-electric propulsion systems would be beneficial for small unmanned vehicles (UAVs) used for military, homeland security, and disaster-monitoring missions. The benefits, due to the hybrid and electric-only modes, include increased time-on-station and greater range as compared to electric-powered UAVs and stealth modes not available with gasoline-powered UAVs. This dissertation contributes to the research fields of small unmanned aerial vehicles, hybrid-electric propulsion system control, and intelligent control. A conceptual design of a small UAV with a parallel hybrid-electric propulsion system is provided. The UAV is intended for intelligence, surveillance, and reconnaissance (ISR) missions. A conceptual design reveals the trade-offs that must be considered to take advantage of the hybrid-electric propulsion system. The resulting hybrid-electric propulsion system is a two-point design that includes an engine primarily sized for cruise speed and an electric motor and battery pack that are primarily sized for a slower endurance speed. The electric motor provides additional power for take-off, climbing, and acceleration and also serves as a generator during charge-sustaining operation or regeneration. The intelligent control of the hybrid-electric propulsion system is based on an instantaneous optimization algorithm that generates a hyper-plane from the nonlinear efficiency maps for the internal combustion engine, electric motor, and lithium-ion battery pack. The hyper-plane incorporates charge-depletion and charge-sustaining strategies. The optimization algorithm is flexible and allows the operator/user to assign relative importance between the use of gasoline, electricity, and recharging depending on the intended mission. AMATLAB/Simulink model was developed to test the control algorithms. DTIC
Adaptive Control; Drone Vehicles; Electric Propulsion; Hybrid Propulsion; Network Control; Neural Nets; Pilotless Aircraft
20050177879 NASA Lewis Research Center, Cleveland, OH, USA
Forebody/Inlet of the Joint Strike Fighter Tested at Low Speeds
Johns, Albert L.; Research and Technology 1997; April 1998; 2 pp.; In English; No Copyright; Avail: CASI; A01, Hardcopy
As part of a national cooperative effort to develop a multinational fighter aircraft, a model of a Joint Strike Fighter concept was tested in several NASA Lewis Research Center wind tunnels at low speeds over a range of headwind velocities and model attitudes. This Joint Strike Fighter concept, which is scheduled to go into production in 2005, will greatly improve the range, capability, maneuverability, and survivability of fighter aircraft, and the production program could ultimately be worth $100 billion. The test program was a team effort between Lewis and Lockheed Martin Tactical Aircraft Systems. Testing was completed in September 1997, several weeks ahead of schedule, allowing Lockheed additional time to review the results and analysis data before the next test and resulting in significant cost savings for Lockheed. Several major milestones related to dynamic and steady-state data acquisition and overall model performance were reached during this model test. Results from this program will contribute to both the concept demonstration phase and the production aircraft. Derived from text
Data Acquisition; Fighter Aircraft; Forebodies; Maneuverability; Surveillance
20050177880 NASA Lewis Research Center, Cleveland, OH, USA
New Nozzle Test Rig Developed
Wolter, John D.; Castner, Raymond S.; Research and Technology 1997; April 1998; 2 pp.; In English; No Copyright; Avail: CASI; A01, Hardcopy
Renewed interest in reducing aircraft noise has spurred the development of a new testing facility. One of the major sources of jet aircraft noise is the engine nozzle exhaust, so wind tunnel and freejet testing have been used to evaluate nozzle concepts for thrust and noise reduction. In the past, the NASA Lewis Research Center used its Jet Exit Rig to supply hot, high-pressure air to the nozzle to simulate engine exhaust, but the flow capacity of this rig was not large enough to supply larger nozzles, which are needed for more accurate noise assessment. Therefore, Lewis developed a new testing tool for this effort, the High-Flow Jet Exit Rig. Derived from text
Noise Reduction; Jet Aircraft Noise; Test Facilities; Nozzle Design
20050177899 NASA Lewis Research Center, Cleveland, OH, USA
Transient Finite Element Analyses Developed to Model Fan Containment Impact Events
Pereira, J. Michael; Research and Technology 1996; March 1997; 2 pp.; In English; No Copyright; Avail: CASI; A01, Hardcopy
Research is underway to establish an increased level of confidence in existing numerical techniques for predicting transient behavior when the fan of a jet engine is released and impacts the fan containment system. To evaluate the predictive accuracy that can currently be obtained, researchers at the NASA Lewis Research Center used the DYNA 3D computer code to simulate large-scale subcomponent impact tests that were conducted at the University of Dayton Research Institute (UDRI) Impact Physics Lab. In these tests, 20- by 40-in. flat metal panels, contoured to the shape of a typical fan case, were impacted by the root section of a fan blade. The panels were oriented at an angle to the path of the projectile that would simulate the conditions in an actual blade-out event. The metal panels were modeled in DYNA 3D using a kinematic hardening model with the strain rate dependence of the yield stress governed by the Cowper-Simons rule. Failure was governed by the effective plastic strain criterion. The model of the fan blade and case just after impact is shown. By varying the maximum effective plastic strain, we obtained good qualitative agreement between the model and the experiments. Both the velocity required to penetrate the case and the deflection during impact compared well. This indicates that the failure criterion and constitutive model may be appropriate, but for DYNA 3D to be useful as a predictive tool, methods to determine accurate model parameters must be established. Simple methods for measuring model parameters are currently being developed. In addition, alternative constitutive models and failure criteria are being investigated. Author
Containment; Fan Blades; Finite Element Method; Impact Tests; Three Dimensional Models
20050177903 NASA Lewis Research Center, Cleveland, OH, USA
Ultraviolet Molecular Rayleigh Scattering Used to Measure Velocity in High-Speed Flow
Seasholtz, Richard G.; Research and Technology 1996; March 1997; 2 pp.; In English; No Copyright; Avail: CASI; A01, Hardcopy
Molecular Rayleigh scattering offers a means to measure gas flow parameters including density, temperature, and velocity. No seeding of the flow is necessary. The Rayleigh scattered power is proportional to the gas density, the spectral width is related to the gas temperature, and the shift in the frequency of the spectral peak is proportional to one component of the fluid velocity.
Velocity measurements based on Rayleigh scattering are more suitable for high-speed flow, where the bulk fluid velocity is on the order of, or larger than, the molecular thermal velocities. Use of ultraviolet wavelengths for Rayleigh scattering diagnostics is attractive for two reasons. First, the Rayleigh scattering cross section is proportional to the inverse 4th power of the wavelength. And second, the reflectivity of metallic surfaces is generally less than it is at longer wavelengths. This is of particular interest in confined flow situations, such as in small wind tunnels and aircraft engine components, where the stray laser light scattered from the windows and internal surfaces in the test facility limits the application of Rayleigh scattering diagnostics.
In this work at the NASA Lewis Research Center, molecular Rayleigh scattering of the 266-nm fourth harmonic of a pulsed, injection seeded Nd:YAG (neodymium:yttriumaluminum- garnet) laser was used to measure velocity in a supersonic free air jet with a 9.3- mm exit diameter. The frequency of the Rayleigh scattered light was analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode, with the images recorded on a cooled, high-quantum-efficiency charge-coupled discharge (CCD) camera. In addition, some unshifted light from the same laser pulse was imaged through the interferometer to generate a reference. Data were obtained with single laser pulses at velocities up to Mach 1.3. The measured velocities were in good agreement with velocities calculated from isentropic flow relations. Our conclusion from this study was that ultraviolet Rayleigh scattering is preferable in confined flow situations because of the increase in the ratio of Rayleigh scattering signal to stray laser light. On the other hand, in open flows, such as free jets and larger wind tunnels where stray laser light can be controlled, visible Rayleigh scattering is preferable. Author
Rayleigh Scattering; Gas Flow; Velocity Measurement; Ultraviolet Radiation; Supersonic Jet Flow; Metal Surfaces; Gas Density
Source: NASA.
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