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At least 91 records · Page 5
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NASA NTRS2019

Over-the-Rotor Liner Investigation via the NASA Langley Normal Incidence Tube

NASA Langley and Glenn Research Centers have collaborated on the usage of acoustic liners mounted very near or directly over the rotor of turbofan aircraft engines. This collaboration began over a decade ago with the investigation of a metallic foam liner. Similar to conventional acoustic liner applications, this liner was designed to absorb sound generated by the rotor-alone and rotor-stator interaction sources within the fan duct. Given its proximity to the rotor tips, the expectation was that the liner would also serve as a pressure release and thereby inhibit the amount of noise generated. Initial acoustic results were promising, but there was concern regarding potential aerodynamic penalties. Nevertheless, there were sufficient positive results to warrant further investigation. To that end, the current report presents results obtained in the NASA Langley Normal Incidence Tube for 20 acoustic liner candidates for the OTR application. The majority contain grooves at their surface, designed to minimize aerodynamic penalties caused by placing the liner in close proximity to the fan rotor tips. The intent is to assess the acoustic properties of each liner configuration, and in particular to assess the effects of including the grooves on the overall acoustic performance. An additional intent of this paper is to provide documentation regarding recent enhancements to the NASA Langley Normal Incidence Tube.

Jones, Michael G↗
NASA NTRS2020

Investigation of a Tandem Tilt-wing VTOL Aircraft in the NASA Langley 12-Foot Low-Speed Tunnel

The emerging Urban Air Mobility market imposes new design requirements on aircraft, including the ability to have vertical take-off and landing (VTOL) capabilities with the ability to transition into fast and efficient forward flight. Industry has proposed many different vehicle configurations, which have many different challenges. A primary challenge facing many of these concepts is flight through the transition corridor from vertical to horizontal flight and back. In an effort to better understand and help improve vehicle safety in the complex transition corridors, NASA Langley Research Center has proposed to characterize the transition corridor with wind tunnel and flight tests for a variety of unmanned aircraft system sized VTOL configurations. The first vehicle of this series is the Langley Aerodrome 8 (LA-8). LA-8 is a high-risk/high-reward tandem tilt-wing vehicle with distributed electric propulsion and a partially deflected slipstream aircraft. The LA-8 vehicle has gone through a preliminary wind tunnel test in NASA Langley's 12-Foot Low-Speed Wind Tunnel. The results of the aerodynamic data collected, including the longitudinal, lateral, and directional force and moment aerodynamic coefficients, from these tests during different phases of flight are presented.

VTOL↗
NASA NTRSDate not supplied

Model Evaluation and Intercomparison Using Data Collected by the Langley Mobile Ozone Lidar in Hampton, Virginia

Throughout the year 2022, the Langley Mobile Ozone Lidar (LMOL) has been frequently collecting ozone and aerosol measurements in the lower troposphere. The lidar is located in the parking lot behind the Atmospheric Sciences building at NASA Langley in Hampton, Virginia, approximately 37.095 N, -76.389 W. The data was collected during a range of several distinct atmospheric conditions, including stratospheric intrusions, surface frontal passages, and long-range transported wildfire smoke plumes. We use this data to evaluate and intercompare the forecast accuracy of two atmospheric chemistry models: the GEOS Composition Forecasting model (GEOS-CF) and the Weather Research and Forecasting model with Chemistry (WRF-Chem). Both models make daily three-dimensional forecasts of many trace gases and species for the contiguous United States. Over a range of ten distinct collection events, each spanning 36 hours to nearly seven days, the forecast models predict tropospheric ozone at NASA Langley with reasonable accuracy. The models best predict the timing and shape of the observed stratospheric intrusions in the middle troposphere but often vary in the magnitude of the ozone mixing ratios. For other atmospheric conditions, there is more variability in the model accuracy. Here, we summarize the accuracy of the models for all events and investigate reasons for differences between the models and the lidar.

Daniel B. Phoenix↗
NASA NTRS2023

Safety Case for Small Uncrewed Aircraft Systems (sUAS) Beyond Visual Line of Sight (BVLOS) Operations at NASA Langley Research Center

This Technical Memorandum (TM) is written to provide for dissemination of the methods and safety considerations for operations of small Uncrewed Aerial Systems (sUAS) Beyond Visual Line-of-Sight (BVLOS)at NASA Langley Research Center. It includes the Safety Case used to acquire a BVLOS Certificate of Authorization (COA) from the FAA and is being published to enable others to benefit from this work. The intended operations, subject to approval from the Federal Aviation Administration (FAA) and the National Aeronautics and Space Administration (NASA), will include a combination of Within Visual Line of Sight (WVLOS) and Beyond Visual Line of Sight (BVLOS) flights, comprising of at most five sUAS operating concurrently, with no more than three operating BVLOS. Flights will occur in a subset of the Langley Air Force Base (LAFB) Class D airspace (KLFI) at a maximum altitude of 400 ft AGL. Most operations within this subset will take place in the City Environment Range Testing for Autonomous Integrated Navigation (CERTAIN) Range. The CERTAIN Range includes airspace inside the borders of NASA Langley Research Center (LaRC). Additional airspace over the northern section of CERTAIN will be requested as part of the Certificate of Authorization (COA). NASA LaRC BVLOS operations on the CERTAIN Range can be broken down into five critical components needed to meet the 14 CFR § 91.113 see and avoid requirement: 1) procedural deconfliction with LAFB for UAS operations at or below 400 ft and manned aircraft at or above 900’ AGL; 2) ground equipment for detection of intruder aircraft and to support communications between crewmembers ; 3) sUAS vehicles with advanced onboard automation capable of autonomously maintaining safe separation; 4) BVLOS standardized operating procedures (SOPs); 5) and personnel to execute the flight operations in accordance with the SOPs and respond to airborne contingencies. The introduction of new ground equipment includes the use of the Remote Operations for Autonomous Missions (ROAM) UAS Operations Center, development and use of an Integrated Airspace Display (IAD), use of the L-STAR and GA-9120 radars, and the incorporation of standardized Vertiports. The ROAM Operations Center will be the central point for all BVLOS sUAS operations. All command and control (C2), voice communications and airspace awareness displays will reside inside ROAM. The IAD will provide raw data from ADS-B, FLARM, radar tracks and telemetered GPS vehicle positions for interpretation by an Airspace Monitor. The radars will search the class D airspace around the CERTAIN Range and serve as a backup to procedural deconfliction procedures coordinated with LAFB. In the event of a procedural deconfliction breakdown, radar detections of non-participating aircraft will be available so that the 91.113 see and avoid requirement can still be safely met. Finally, the incorporation of Vertiports will have video and network connectivity that enables large numbers of sUAS launches and recoveries from a single location. This is a continuation of the remote command and control of unpiloted aircraft component focused on evaluating unpiloted aircraft flight crew roles and responsibilities, control interfaces and the associated data links needed to operate a fleet of aircraft within a UAM Ecosystem. This work supports the development of future aviation operational concepts based on an Urban Air Mobility Maturity Level (UML) 4 environment (Patterson, 2020). It is assumed that future airspace will include hundreds of simultaneous aircraft operations within the airspace, therefore scalable operations are essential for enabling this future airspace to become a reality. Follow on work includes envisioned flights that expand operations beyond the CERTAIN range and lead to an effective Maritime Surveillance capability.

Matthew W Coldsnow↗
NASA NTRSDate not supplied

Density-Based Optical Diagnostic Techniques at Nasa Langley Research Center

Several density-based optical diagnostic techniques under development for both ground test facilities and flight vehicles at NASA Langley Research Center will be presented. I will first discuss recent development work on focused laser differential interferometry (FLDI) for Langley’s hypersonic test facilities, including multi-point FLDI and co-linear FLDI/schlieren imaging. I will then discuss our work on tomographic background-oriented schlieren (Tomo BOS) and the challenges associated with its implementation in Langley’s ground test facilities. Finally, I will present results obtained with a new self-aligned focusing schlieren technique my team has developed and discuss how this technique is a significant improvement over traditional focusing schlieren systems.

Brett Bathel↗
NASA NTRS2023

Guidelines for Schlieren Systems at Langley Research Center

The original Langley Working Paper (LWP 448) published on July 27th, 1967, provided guidance to NASA Langley Research Center personnel on how to set up conventional path-integrated schlieren flow visualization systems and what pitfalls could be expected with such setups. The guidance and information contained in the document continues to be used for schlieren setups at NASA Langley Research Center to this day.

Schlieren↗
NASA NTRSDate not supplied

Atmospheric Composition Forecast Model Evaluation Using Ozone Measurements Collected by the Langley Mobile Ozone Lidar

The Langley Mobile Ozone Lidar (LMOL) is a mobile ground based lidar system based at NASA Langley in Hampton, Virginia. Between 2022 and 2024, LMOL collected over 2500 hours of ozone measurements for a range of different atmospheric conditions, including calm days, stratospheric intrusions, surface frontal passages, and long-range transported wildfire smoke plumes. Here, the data is used to evaluate the forecast accuracy of NASA’s Global GEOS Composition Forecasting (GEOS-CF) model. GEOS-CF makes daily three-dimensional forecasts of trace gases and aerosol species. Overall, for calm periods, the forecast model predicts lower tropospheric ozone at NASA Langley with reasonable accuracy (within 20%). The model best predicts the timing and extent of stratospheric intrusions but often vary in the magnitude of the ozone mixing ratio. Among the other types of atmospheric conditions, there is more variability in the model forecasts. Based on this analysis, model forecasts are utilized to determine future data acquisition opportunities with the goal of providing feedback to the modeling teams, thereby enabling them to better understand the model biases and improve the model forecasts of ozone during these different atmospheric conditions.

Daniel B Phoenix↗
NASA NTRS1972

Employee Communication at the NASA Langley Research Center

The means of employee communication at the NASA Langley Research Center are reported, and their effectiveness evaluated. The history, purpose, and structure of the organization as well as the employee educational background and salary status are discussed. Some of the approaches used by Langley Research Center management in communicating with their men are addressed and compared with recommendations of experts in employee communication. The results of personal interviews involving both employee and management assessment of management-employee communication are presented and evaluated. Employees need a great deal more recommunication from management providing rationale behind the cancellation of existing projects or the disapproval of proposed research projects. Also NASA management needs to establish a policy and guidelines for the rapid and simultaneous dissemination of all non-restricted information to employees during organizational activities having potential adverse effects on large numbers of personnel. Finally some improvements should be made in employee orientation procedures.

Bendura, R. J.↗
NASA NTRS1973

Stability and control characteristics of a Langley concept space shuttle orbiter (LO-100) at low subsonic speeds

An experimental aerodynamic investigation was conducted on a 0.01 scale model of a Langley concept space shuttle orbiter (LO-100) in the Langley Low Turbulence Pressure Tunnel at a Mach number of 0.25 and at a Reynolds number of 5.4 million per foot. The angle of attack was varied from about -2 deg to 24 deg at 0 deg and 5 deg sideslip. The configuration was tested at elevon settings of 0 deg, -5 deg, -10 deg, and -15 deg for a body base flap setting of 0 deg and at 0 deg, -10 deg, and -15 deg for a body base flap setting of -18 deg. The effect of rudder flare angle was obtained using 0 deg, 20 deg, and 40 deg, flare settings.

Spencer, B., Jr.↗
NASA NTRS1974

The NASA Langley building solar project and the supporting Lewis solar technology program

The use of solar energy to heat and cool a new office building that is now under construction is reported. Planned for completion in December 1975, the 53,000 square foot, single story building will utilize 15,000 square feet of various types of solar collectors in a test bed to provide nearly all of the heating demand and over half of the air conditioning demand. Drawing on its space-program-developed skills and resources in heat transfer, materials, and systems studies, NASA-Lewis will provide technology support for the Langley building project. A solar energy technology program underway at Lewis includes solar collector testing in an indoor solar simulator facility and in an outdoor test facility, property measurements of solar panel coatings, and operation of a laboratory-scale solar model system test facility. Based on results obtained in this program, NASA-Lewis will select and procure the solar collectors for the Langley test bed.

Ragsdale, R. G.↗
NASA NTRS1975

Inlet performance of the integrated Langley scramjet module

The inlet concept for the Langley Scramjet Module has been developed and proven in Langley wind tunnels over a Mach number range from 2.3 to 6.0 (flight simulation of Mach 2.6 to 7.6). This modular engine concept is designed to integrate with the airframe, which results in precompression of the engine airflow by the vehicle bow shock and additional expansion of the nozzle exhaust gas by the afterbody of the vehicle. With these integration advantages, the inlet can be designed with modest contraction ratios and fixed geometry. Also, the module nozzle exit area can be equal to the capture area, which permits the cowl to be alined with the local flow producing minimum external drag. The inlet leading edges and planar compression surfaces are swept at 48 deg, which provides spillage at low Mach numbers for starting and which reduces the pressure gradient on the top surface to permit ingestion of the vehicle forebody boundary layer into the inlet without separating. Three fuel injection struts provide for the use of a short combustor having low internal cooling requirements. Schedules for mass capture ratio, contraction ratio, and total pressure recovery are well within the acceptable range for a good scramjet propulsion device. The fixed geometry, minimum external drag design has proven to be a practical, high-performance inlet concept.

Trexler, C. A.↗
NASA NTRS1977

Recertification of the air and methane storage vessels at the Langley 8-foot high-temperature structures tunnel

This center operates a number of sophisticated wind tunnels in order to fulfill the needs of its researchers. Compressed air, which is kept in steel storage vessels, is used to power many of these tunnels. Some of these vessels have been in use for many years, and Langley is currently recertifying these vessels to insure their continued structural integrity. One of the first facilities to be recertified under this program was the Langley 8-foot high-temperature structures tunnel. This recertification involved (1) modification, hydrotesting, and inspection of the vessels; (2) repair of all relevant defects; (3) comparison of the original design of the vessel with the current design criteria of Section 8, Division 2, of the 1974 ASME Boiler and Pressure Vessel Code; (4) fracture-mechanics, thermal, and wind-induced vibration analyses of the vessels; and (5) development of operating envelopes and a future inspection plan for the vessels. Following these modifications, analyses, and tests, the vessels were recertified for operation at full design pressure (41.4 MPa (6000 psi)) within the operating envelope developed.

Hudson, C. M.↗
NASA NTRS1977

Operational experience in the Langley expansion tube with various test gases

A resume' of operating experiences with the Langley Expansion Tube is presented. The driver gas was unheated helium at a nominal pressure of 5000 psi and the majority of the data presented are for air and carbon dioxide test gases. The primary purpose of these data is to illustrate the effects of various parameters on quasi-steady test flow duration, as well as free stream and post-normal shock flow conditions. The discussion shows that the Langley Expansion Tube is an operational facility capable of producing good quality, highly repeatable, quasi-steady flow for test times sufficient to establish flow about blunt axisymmetric and two-dimensional models.

Miller, C. G.↗
NASA NTRS1980

Microprocessor user support at Langley Research Center

The use of microprocessors pose significant problems including: (1) a long learning process for proficient use of microprocessors; (2) the requirement for extensive support in both hardware and software; and (3) the need for coordination and sharing of the creative effort to avoid unnecessary duplication. To address these problems, Langley Research Center has established a microprocessor users committee to provide an advisory interface for management and users, and is training microprocessor users. A newsletter is published to disseminate information among microprocessor users. Both cross software on the central computer complex and microprocessor development systems are used to support the design of microprocessor based systems. Each of these activities is reviewed with special emphasis given to the microprocessor support available from the central computer complex. The effectiveness of the approach being taken at Langley is assessed and specific hardware and software development efforts that are targeted toward enhancing the existing microprocessing support are discussed.

Tucker, J. H.↗
NASA NTRS1982

Blockage and flow studies of a generalized test apparatus including various wing configurations in the Langley 7-inch Mach 7 Pilot Tunnel

A 1/12th scale model of the Curved Surface Test Apparatus (CSTA), which will be used to study aerothermal loads and evaluate Thermal Protection Systems (TPS) on a fuselage-type configuration in the Langley 8-Foot High Temperature Structures Tunnel (8 ft HTST), was tested in the Langley 7-Inch Mach 7 Pilot Tunnel. The purpose of the tests was to study the overall flow characteristics and define an envelope for testing the CSTA in the 8 ft HTST. Wings were tested on the scaled CSTA model to select a wing configuration with the most favorable characteristics for conducting TPS evaluations for curved and intersecting surfaces. The results indicate that the CSTA and selected wing configuration can be tested at angles of attack up to 15.5 and 10.5 degrees, respectively. The base pressure for both models was at the expected low level for most test conditions. Results generally indicate that the CSTA and wing configuration will provide a useful test bed for aerothermal pads and thermal structural concept evaluation over a broad range of flow conditions in the 8 ft HTST.

Albertson, C. W.↗
NASA NTRS1982

Historical perspectives on thermostructural research at the NACA Langley Aeronautical Laboratory from 1948 to 1958

Some of the early research on structural problems produced by aerodynamic heating, conducted at the Langley Aeronautical Laboratory of the National Advisory Committee for Aeronautics from 1948 to 1958 is described. That was the last decade of the NACA; in 1958 NACA became the nucleus of NASA. The NACA initially contracted for research but was aware that a well-equipped and suitably staffed laboratory was required to fulfill its obligations. Langley was established in 1920; the other listed were added during the NACA expansion in the World War II years. Some specific research activities are described, starting with calculation of the temperature of the structure.

Heldenfels, R. R.↗
NASA NTRS1982

Flow field studies using holographic interferometry at Langley

Some of the uses of holographic interferometry at Langley Research Center both for flow visualization and for density field determinations are described and tests in cryogenic flows at the Langley 0.3-Meter Transonic Cryogenic Tunnel are discussed. Experimental and theoretical fringe shift data are compared.

Burner, A. W.↗
NASA NTRS1984

Status of advanced airfoil tests in the Langley 0.3-meter transonic cryogenic tunnel

A joint NASA/U.S. industry program to test advanced technology airfoils in the Langley 0.3-meter Transonic Tunnel (TCT) was formulated under the Langley ACEE Project Office. The objectives include providing U.S. industry an opportunity to compare their most advanced airfoils to the latest NASA designs by means of high Reynolds number tests in the same facility. At the same time, industry would again experience in the design and construction of cryogenic test techniques. The status and details of the test program are presented. Typical aerodynamic results obtained, to date, are presented at chord Reynolds number up to 45 x 10(6) and are compared to results from other facilities and theory. Details of a joint agreement between NASA and the Deutsche Forschungs- und Versuchsantalt fur Luft- and Raumfahrt e.V. (DFVLR) for tests of two airfoils are also included. Results of these tests will be made available as soon as practical.

Ladson, C. L.↗