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The commercial turbofan trend of increasing bypass ratio and decreasing fan pressure ratio has seen its latest market entry in Pratt & Whitney's PurePower™ product line, which will power regional aircraft for the Bombardier and Mitsubishi corporations, starting in 2013. The high-bypass-ratio, low-fan-pressure-ratio trend, which is aimed at diminishing noise while increasing propulsive efficiency, combines with contemporary business factors including the escalating cost of testing and limited availability of simulated altitude test sites to pose formidable challenges for engine certification and performance validation. Most fundamentally, high bypass ratio and low fan pressure ratio drive increased gross-to-net thrust ratio and decreased fan temperature rise, magnifying by a factor of two or more the sensitivity of in-flight thrust and low spool efficiency to errors of measurement and assumption, i.e., physical modeling.

As aircraft programs currently ramp up, productivity of assembly processes needs to be improved while keeping quality, reliability and manufacturing cost requirements. Efficiency of the drilling process still remains an issue particularly in the case of CFRP/metal stacks: hot and long metallic chips are difficult to remove and often damage the surface of CFRP holes. Low frequency axial vibration drilling has been proposed to solve this issue. This innovative drilling process allows breaking up the metallic chips in such a way that jamming is avoided. This paper presents a case of CFRP/Ti6Al4V drilling on a CNC machine where productivity must be increased. A comparison is made between the current regular process and the MITIS drilling process. First the analysis and comparison method is presented. The current process is analyzed and its limits are highlighted. Then the vibration process is implemented and its performances are studied.

This paper presents a set of numerical computations with different turbulence model on an air jet flowing tangentially over the curved surface. It has been realized that jet deflection angle and the corresponding thrust are important parameter to determine with great care. Through the grid independence analysis, it has been found that without resolution of the viscous sub-layer, it is not possible to determine the computationally independent angle of jet deflection and boundary layer thickness. The boundary layer analysis has been performed at different radius of curvature and at jet Reynolds number ranging from approximately about 2400-10,000. The boundary layer thickness has been determined at the verge of separation and found a relation with the radius of curvature and jet Reynolds number. The skin-friction coefficient has been also studied at the verge of separation in relation to the surface radius and jet Reynolds number.

This study investigates the self-adjusted cutting parameter technique to improve the drilling of multi-stacked material. The technique consists in changing the cutting strategy automatically, according to the material being machined. The success of this technique relies on an accurate signal analysis, whatever the process setting. Motor current or thrust force are mostly used as incoming signals. Today, analyses are based on the thresholding method. This consists in assigning lower and upper limits for each type of material. The material is then identified when the signal level is stabilized in between one of the thresholds. Good results are observed as long as signal steps are significantly distinct. This is the case when drilling TA6V-CFRP stacks. However, thrust force level remains roughly unchanged for AA7175-CFRP stacks, leading to overlapping thresholds. These boundary limits may also change with tool geometry, wear condition, cutting parameters, etc.

Radical new electrically propelled aircraft are being considered to meet strict future performance goals. One concept design proposed is a Turboelectric Distributed Propulsion (TeDP) aircraft that utilises a number of electrically driven propulsors. Such concepts place a new and significant reliance on an aircraft's electrical system for safe and efficient flight. Accordingly, in addition to providing certainty that supply reliability targets are being met, a contingency analysis, evaluating the probability of component failure within the electrical network and the impact of that failure upon the available thrust must also be undertaken for architecture designs. Solutions that meet specified thrust requirements at a minimum associated weight are desired as these will likely achieve the greatest performance against the proposed emissions targets.

A review of the research accomplished in 2009 in the System-Level Design, Analysis and Simulation Tools (SLDAST) of the NASA's Airspace Systems Program is presented. This research thrust focuses on the integrated system-level assessment of component level innovations, concepts and technologies of the Next Generation Air Traffic System (NextGen) under research in the ASP program to enable the development of revolutionary improvements and modernization of the National Airspace System. The review includes the accomplishments on baseline research and the advancements on design studies and system-level assessment, including the cluster analysis as an annualization standard of the air traffic in the U.S. National Airspace, and the ACES-Air MIDAS integration for human-in-the-loop analyzes within the NAS air traffic simulation.

This paper outlines power system architecture trades performed on the N3-X hybrid wing body aircraft concept under NASA's Research and Technology for Aerospace Propulsion (RTAPS) study effort. The purpose of the study to enumerate, characterize, and evaluate the critical dynamic and safety issues for the propulsion electric grid of a superconducting Turboelectric Distributed Propulsion (TeDP) system pursuant to NASA N+3 Goals (TRL 4-6: 2025, EIS: 2030-2035). Architecture recommendations focus on solutions which promote electrical stability, electric grid safety, and aircraft safety. Candidate architectures were developed and sized by balancing redundancy and interconnectivity to provide fail safe and reliable, flight critical thrust capability. This paper outlines a process for formal contingency analysis used to identify these off-nominal requirements. Advantageous architecture configurations enabled a reduction in the NASA's assumed sizing requirements for the propulsors.

A test program was initiated to study the effects of improved lubrication delivery on the total heat rejection of an aircraft accessory drive gearbox. The goal of this program was to reduce the overall gearbox heat rejection by minimizing the viscous drag and churning losses. The most practical heat sink available to secondary power subsystems on supersonic aircraft is the fuel supply; and due to its limited capacity, reduced heat rejection from these systems is very desirable. A model of gearbox cooling requirements will be presented and compared with the lube distribution of a baseline gearbox and subsequent modified configurations. The effects of oil-in temperature, and lube gallery pressure on heat rejection are shown, with emphasis placed on minimizing this heat rejection.

Emission spectroscopy is a powerful non-intrusive research tool for investigating combustion processes. This technology is being researched and transitioned into rocket engine ground test operations at Stennis Space Center (SSC). Much has been achieved with commercially available emission spectrometers and much more is expected from the next generation equipment, such as the Optical Plume Anomaly Detector (OPAD) emission spectrometer designed specifically for this purpose. Some basic issues are being researched at SSC to make exhaust plume diagnostics a fully operational tool for propulsion system ground test operations. Knowledge gained during the development of this technology for ground test is critical to the development of flight-rated sensors and for Vehicle Health Management System(s) (VHMS) for future vehicles, such as the New Launch System (NLS), National Aerospace Plane (NASP), and those developed for the Space Exploration Initiative (SEI).

In addition to designing fighter engines for stall-free idle to maximum power operation and stall recoverability, it is important to give proper emphasis to sub-idle operation for successful starting. This permits the pilot to confidently bring the engine on-line following an inadvertent flameout caused by either the airplane departing the flight envelope or by a fuel interrupt due to a malfunction. Thus reliable and fast airstart capability enhances flight safety especially of single engine airplanes. Flight testing, therefore, is substantially devoted to airstart evaluation. The paper first explains the influence of engine design features on airstarting, particularly the advantages of the low bypass ratio cycle F100-PW-229 (PW229) engine, which is an increased thrust derivative (IPE) of the highly successful F100-PW-220 engine. Enhancing airstarting capability of the PW229 using variable geometry features and digital control flexibility is discussed.

Use of ceramic materials in the hot section of the fuel turbopump of advanced reusable rocket engines promises increased performance and payload capability, improved component life and economics, and greater design flexibility. Severe thermal transients present during operation of the Space Shuttle Main Engine (SSME) push metallic components to the limit of their capabilities. Future engine requirements may be even more severe. In Phase I of this two Phase program, performance benefits have been quantified and continuous fiber reinforced ceramic matrix composite (FRCMC) components have demonstrated a potential to survive the hostile environment of an advanced rocket engine turbopump

This paper summarizes the development of the probabilistic load modeling for the turbomachinery of space propulsion systems at Rocketdyne. The demand for rocket engine turbomachinery with high performance and light weight has presented a unique set of problems; e.g., the high-energy density in design and analysis of the turbomachinery loads. A heuristic approach to the simulation of probabilistic loads is employed to provide a uniform framework on which the subsystem component loads are evaluated. Turbomachinery loads can be classified into three categories: (1) loads internal to the turbopumps, (2) loads that result from the turbopump operation, and (3) loads transmitted from other driving sources. The modeling techniques employed for the turbomachinery loads are the influence model method, the marginal distribution method, the scaling method, the normalized power spectral density (PSD) model, and improved scaling for vibration, etc.

Pegasus is a newly-developed small payload launch vehicle. While the Pegasus design relies heavily on proven technology, the overall concept breaks new ground in several respects. Most notably, Pegasus is launched from a large transport-class carrier aircraft at high altitude. This launch mode confers a number of significant advantages, both for operations and performance. In particular, air-launched performance benefits from the use of aerodynamic lift to reduce gravity losses. Pegasus is unique among launch vehicles in its employment of a wing to fly a lifting ascent trajectory. As a consequence, the Pegasus control system includes features common to both aircraft and conventional launch vehicles. The stage 1 flight envelope encompasses conditions ranging from a subsonic glide immediately after launch to hypersonic flight under 8 g's of acceleration near the end of the burn. All aerodynamic data used for trajectory and control system design was obtained from analysis.

The Diagnostics Tested Facility (DTF) at NASA's John C. Stennis Space Center (SSC) in Mississippi was designed to provide a testbed for development of rocket engine exhaust plume diagnostics instrumentation. A 1200-lb thrust liquid oxygen (LOX)/gaseous hydrogen (GH2) thruster is used as the plume source for experimentation and instrument development. Theoretical comparative studies have been performed with aero-thermodynamic codes to ensure that the DTF thruster (DTFT) has been optimized to produce a plume with pressure and temperature conditions as much like the plume of the Space Shuttle Main Engine (SSME) as possible. Operation of the DTFT is controlled by an icon-driven software program using a series of soft switches. Data acquisition is performed using the same software program. A number of plume diagnostics experiments have utilized the unique capabilities of the DTF.

Advanced methods of Data Acquisition and Control provide rocket test facilities with higher resolution data, faster quick look data reduction, and better engine control. This system hardware and software architecture provides higher sample rate data with 12 bit resolution, more precise engine control, faster test turnaround and setup, enhanced graphic displays, and on the spot reduced “quick look” data within a few minutes of the actual rocket engine test firing. The result is a significant savings in time and dollars.

There is a need for a space launch system that can provide ready, reliable, unencumbered access to space. The need exists for a highly reliable launch system that can operate from numerous available sites, that can provide all azimuth launch capability, that is fully reusable, and that can carry significant payloads into low earth orbit. A vehicle concept was developed to demonstrate the ability of near term aeromechanics and propulsion technology to support such a system. The vehicle was composed of two stages. The system takes off horizontally and both stages return to a horizontal landing. Turbojet, ramjet, and rocket propulsion is used. The sensitivity of the system to thrust, drag, weight, and staging Mach number was examined. The two stage system is able to accommodate a range of performance variations yet still retain significant mission potential.

Using LH2 heat sink capacity for air precooling in turbojets allows to increase specific impulse and in many cases to reduce specific mass (mass-to-sea level thrust ratio). A number of precooled turbojet schemes are considered. Classification of turbojet according to the cooled air amount and depth of cooling is proposed. ATR with extended precooling (Tout=100K) is examined in more detail. For propulsion systems including different types of engines, running simultaneously the concept of LH2 heat sink capacity concentration for turbojet air precooling is proposed.

A main objective of the STOL and Maneuver Technology Demonstrator, (S/MTD) Program was to evaluate the operability and performance of its unique engine/nozzle configuration which can deliver thrust in three different modes; conventional, vectored and through variable vanes which give the option of going from forward to reverse thrust. The two-dimensional nozzle and the modified engine were extensively tested during sea level and altitude testing to satisfy all flight clearance requirements. This paper concentrates on the flight test results of the various modes of vectoring and reversing ending with a compilation of the actual usage of the propulsive controls that could be used by designers of similar advanced propulsion systems.

Aerodynamic effects induced from vectoring an exhaust jet are investigated using a well established thin-layer Reynolds averaged Navier-Stokes code. This multiple block code has been modified to allow for the specification of jet properties at a block face. The applicability of the resulting code for thrust vectoring applications is verified by comparing numerically and experimentally determined pressure coefficient distributions for a jet-wing afterbody configuration with a thrust-vectoring 2-D nozzle. Induced effects on the body and nearby wing from thrust vectoring are graphically illustrated.

This paper presents an overview on an Air Force initiative aimed at increasing the performance and reliability of aircraft batteries. A major thrust of the initiative is the elimination of flight line battery maintenance shops. Cost savings, increased mission capability and battle readiness are the pay-offs that will be realized from this effort. Current maintenance requirements for vented nickel-cadmium (Ni-Cd) batteries used in most U.S. military aircraft are unacceptable. This paper addresses other available technology options, decisions made to date and benefits that will result from this effort to increase the performance and reliability of aircraft batteries.