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  • Other Sources  (207)
  • AIRCRAFT DESIGN, TESTING AND PERFORMANCE
  • AIRCRAFT PROPULSION AND POWER
  • Cell & Developmental Biology
  • Polymer and Materials Science
  • Propellants and Fuels
  • 2005-2009  (19)
  • 1990-1994  (184)
  • 1950-1954  (4)
  • 1915-1919
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  • 1
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    Effect of aeroelastic-propulsive interactions on flight dynamics of a hypersonic vehicle (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The desire to achieve orbit-on-demand access to space with rapid turn-around capability and aircraft-like processing operations has given rise to numerous hypersonic aerospace plane design concepts which would take off horizontally from a conventional runway and employ air-breathing scramjet propulsion systems for acceleration to orbital speeds. Most of these air-breathing hypersonic vehicle concepts incorporate an elongated fuselage forebody to act as the aerodynamic compression surface for a scramjet combustor module. This type of airframe-integrated scramjet propulsion system tends to be highly sensitive to inlet conditions and angle-of-attack perturbations. Furthermore, the basic configuration of the fuselage, with its elongated and tapered forebody, produces relatively low frequency elastic modes which will cause perturbations in the combustor inlet conditions due to the oscillation of the forebody compression surface. The flexibility of the forebody compression surface, together with sensitivity of scramjet propulsion systems to inlet conditions, creates the potential for an unprecedented form of aeroelastic-propulsive interaction in which deflections of the vehicle fuselage give rise to propulsion transients, producing force and moment variations that may adversely impact the longitudinal flight dynamics and/or excite the elastic modes. These propulsive force and moment variations may have an appreciable impact on the performance, guidance, and control of a hypersonic aerospace plane. The objectives of this research are to quantify the magnitudes of propulsive force and moment perturbations resulting from elastic deformation of a representative hypersonic vehicle, and to assess the potential impact of these perturbations on the vehicle's longitudinal flight dynamics.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA LaRC Workshop on Guidance, Navigation, Controls, and Dynamics for Atmospheric Flight, 1993; p 459-472
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Microgravity Smoldering Combustion on the USML-1 Space Shuttle Mission (1994)
    In:  CASI
    Details
    Publication Date: 2018-06-12
    Description: Preliminary results from an experimental study of the smolder characteristics of a porous combustible material (flexible polyurethane foam) in normal and microgravity are presented. The experiments, limited in fuel sample size and power available for ignition, show that the smolder process was primarily controlled by heat losses from the reaction to the surrounding environment. In microgravity, the reduced heat losses due to the absence of natural convection result in only slightly higher temperatures in the quiescent microgravity test than in normal gravity but a dramatically larger production of combustion products in all microgravity tests. Particularly significant is the proportionately larger amount of carbon monoxide and light organic compounds produced in microgravity, despite comparable temperatures and similar char patterns. This excessive production of fuel-rich combustion products may be a generic characteristic of smoldering polyurethane in microgravity, with an associated increase in the toxic hazard of smolder in spacecraft.
    Keywords: Propellants and Fuels
    Type: Joint Launch + One Year Science Review of USML-1 and USMP-1 with the Microgravity Measurement Group, Volume 2; 609-629; NASA-CP-3272-Vol-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Dynamic Control of Aerodynamic Instabilities in Gas Turbine Engines (1992)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: This lecture discusses the use of closed loop control at the component level to enhance the performance of gas turbine engines. The general theme is the suppression of flow instabilities (rotating stall and surge) through use of feedback, either actively or by means of the aeromechanical coupling provided by tailored structures. The basic concepts that underlie active control of turbomachinery instability, and their experimental demonstration, are first described for a centrifugal compressor. It is shown that the mechanism for stabilization is associated with damping of unsteady perturbations in the compression system, and the steady-state performance can thus remain virtually unaltered. Control of instability using a tailored structure is then discussed, along with experimental results illustrating the flow range extension achievable using this technique. A considerably more complex problem is presented by active control or rotating stall where the multi-dimensional features mean that distributed sensing and actuation are required. In addition, there are basic questions concerning unsteady fluid mechanics; these imply the need to resolve issues connected with identification of suitable signals as well as with definition of appropriate wave launchers for implementing the feedback. These issues are discussed and the results of initial successful demonstrations of active control of rotating stall in a single-stage and a three-stage axial compressor are presented. The lecture concludes with suggestions for future research on dynamic control of gas turbine engines.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AGARD, Steady and Transient Performance Prediction of Gas Turbine Engines; 20 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    NASA advanced aeronautics design solar powered remotely piloted vehicle (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Environmental problems such as the depletion of the ozone layer and air pollution demand a change in traditional means of propulsion that is sensitive to the ecology. Solar powered propulsion is a favorable alternative that is both ecologically harmless as well as cost effective. Integration of solar energy into designs ranging from futuristic vehicles to heating is beneficial to society. The design and construction of a Multi-Purpose Remotely Piloted Vehicle (MPRPV) seeks to verify the feasibility of utilizing solar propulsion as a primary fuel source. This task has been a year long effort by a group of ten students, divided into five teams, each dealing with different aspects of the design. The aircraft was designed to take-off, climb to the design altitude, fly in a sustained figure-eight flight path, and cruise for approximately one hour. This mission requires flight at Reynolds numbers between 150,000 and 200,000 and demands special considerations in the aerodynamic design in order to achieve flight in this regime. Optimal performance requires a light weight configuration with both structural integrity and maximum power availability. The structure design and choice of solar cells for the propulsion was governed by the weight, efficiency, and cost considerations. The final design is a MPRPV weighting 35 N which cruises 7 m/s at the design altitude of 50 m. The configuration includes a wing composed of balsa and foam NACA 6409 airfoil sections and carbon fiber spars, a tail of similar construction, and a truss structure fuselage. The propulsion system consists of 98 10 percent efficient solar cells donated by Mobil Solar, a NiCad battery for energy storage, and a folding propeller regulated by a lightweight and efficient control system. The airfoils and propeller chosen for the design were research and tested during the design process.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-190007 , NAS 1.26:190007
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Behavior of composite/metal aircraft structural elements and components under crash type loads - What are they telling us? (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Failure behavior results are presented from crash dynamics research using concepts of aircraft elements and substructure not necessarily designed or optimized for energy absorption or crash loading considerations. To achieve desired new designs which incorporate improved energy absorption capabilities often requires an understanding of how more conventional designs behave under crash loadings. Experimental and analytical data are presented which indicate some general trends in the failure behavior of a class of composite structures which include individual fuselage frames, skeleton subfloors with stringers and floor beams but without skin covering, and subfloors with skin added to the frame-stringer arrangement. Although the behavior is complex, a strong similarity in the static and dynamic failure behavior among these structures is illustrated through photographs of the experimental results and through analytical data of generic composite structural models. It is believed that the similarity in behavior is giving the designer and dynamists much information about what to expect in the crash behavior of these structures and can guide designs for improving the energy absorption and crash behavior of such structures.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: ICAS Congress; Sept. 9-14, 1990; Stockholm; Sweden
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Aerodynamic performance optimization of a rotor blade using a neural network as the analysis (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: This paper describes the use of neural networks as a replacement for rotor analyses in a conventional aerodynamic performance optimization procedure. The optimization procedure minimizes an objective function, a linear combination of horsepower required for hover, forward flight, and maneuver. The design variables are pretwist, taper initiation, taper ratio, and blade root chord. Constraints consist of limits on horsepower required (for hover, forward flight, and maneuver), stall, trim, and minimum tip chord. Neural network analyses agree with conventional analyses.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 92-4837 , AIAA, USAF, NASA, and OAI, Symposium on Multidisciplinary Analysis and Optimization; Sept. 21-23, 1992; Cleveland, OH; United States|; 16 p.
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Ordering design tasks based on coupling strengths (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The design process associated with large engineering systems requires an initial decomposition of the complex system into modules of design tasks which are coupled through the transference of output data. In analyzing or optimizing such a coupled system, it is essential to be able to determine which interactions figure prominently enough to significantly affect the accuracy of the system solution. Many decomposition approaches assume the capability is available to determine what design tasks and interactions exist and what order of execution will be imposed during the analysis process. Unfortunately, this is often a complex problem and beyond the capabilities of a human design manager. A new feature for DeMAID (Design Manager's Aid for Intelligent Decomposition) will allow the design manager to use coupling strength information to find a proper sequence for ordering the design tasks. In addition, these coupling strengths aid in deciding if certain tasks or couplings could be removed (or temporarily suspended) from consideration to achieve computational savings without a significant loss of system accuracy. New rules are presented and two small test cases are used to show the effects of using coupling strengths in this manner.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-109137 , NAS 1.15:109137 , MDO-AIAA/NASA/USAF/ISSMO Conference; Sep 07, 1994 - Sep 09, 1994; Panama City, FL; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    An Experimental Study of n-Heptane and JP-7 Extinction Limits in an Opposed Jet Burner (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Propulsion engine combustor design and analysis requires experimentally verified data on the chemical kinetics of fuel. Among the important data is the combustion extinction limit as measured by observed maximum flame strain rate. The extinction limit relates to the ability to maintain a flame in a combustor during operation. Extinction limit data can be obtained for a given fuel by means of a laminar flame experiment using an opposed jet burner (OJB). Laminar extinction limit data can be applied to the turbulent application of a combustor via laminar flamelet modeling. The OJB consists of two axi-symmetric tubes (one for fuel and one for oxidizer), which produce a flat, disk-like counter-flow diffusion flame. This paper presents results of experiments to measure extinction limits for n-heptane and the military specification fuel JP-7, obtained from an OJB. JP-7 is an Air Force-developed fuel that continues to be important in the area of hypersonics. Because of its distinct properties it is currently the hydrocarbon fuel of choice for use in Scramjet engines. This study provides much-desired data for JP-7, for which very little information previously existed. The interest in n-heptane is twofold. First, there has been a significant amount of previous extinction limit study and resulting data with this fuel. Second, n-heptane (C7H16) is a pure substance, and therefore does not vary in composition as does JP-7, which is a mixture of several different hydrocarbons. These two facts allow for a baseline to be established by comparing the new OJB results to those previously taken. Additionally, the data set for n-heptane, which previously existed for mixtures up to 26 mole percent in nitrogen, is completed up to 100% n-heptane. The extinction limit data for the two fuels are compared, and complete experimental results are included.
    Keywords: Propellants and Fuels
    Type: 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit; Jul 10, 2005 - Jul 13, 2005; Tucson, AZ; United States
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  • 9
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    Experimental investigation of spherical-convergent-flap thrust-vectoring two-dimensional plug nozzles (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An experimental investigation of multiaxis thrust vectoring nozzles with spherical convergent flaps (SCF) and a convertible (in-flight deployable) centerline plug were tested in the NASA-Langley 16-Foot Transonic Tunnel Static Test Facility. Parameters tested during the static test included plug length, external shroud length, shroud internal angle, and yaw vector angle. Results indicated that the SCF convertible-plug nozzle flow is highly three dimensional and characterized by internal flow separation and shock effects. The resultant thrust and discharge coefficient levels were lower than previous wedge nozzle results. In addition, increasing shroud internal angle increased resultant thrust ratio but decreased discharge coefficient. Increasing shroud length increased resultant thrust ratio performance for NPR's greater than 6.0 but for NPR's less than 6.0, resultant thrust ratio decreased as shroud length increased. Increasing plug length caused an increase in resultant thrust ratio and an increase in discharge coefficient. Increasing geometric yaw vector angle had no effect on resultant thrust ratio and little effect on discharge coefficient.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 93-2431 , AIAA, SAE, ASME, and ASEE, Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States|; 18 p.
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    NASA TECHNICAL REPORTS
  • 10
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    Optimizing tuning masses for helicopter rotor blade vibration reduction including computed airloads and comparison with test data (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An optimization procedure is developed for locating tuning masses on a rotor blade so that vibratory loads are minimized and hub-shear harmonics are reduced without adding a large mass penalty. The airloads are computed by means of a helicopter analysis for the cases of three vs six tuning masses, with attention given to the prediction of changes in airloads. Frequencies, airloads, and hub loads are computed with the CAMRAD/JA helicopter analysis code and the Conmin general-purpose optimization program. The hub shear is found to be significantly reduced in both cases with the added mass, and the reduction of hub shear is demonstrated under three flight conditions. Comparisons with wind-tunnel data demonstrate that the correlation of mass location is good and the relationship between mass location and flight speed is predicted well by the model.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 92-2376 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 13, 1992 - Apr 15, 1992; Dallas, TX; United States
    Format: text
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