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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
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NASA NTRS2011

Experimental and Analytical Evaluation of a Composite Honeycomb Deployable Energy Absorber

In 2006, the NASA Subsonic Rotary Wing Aeronautics Program sponsored the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, which is designated the Deployable Energy Absorber (DEA), utilizes an expandable Kevlar honeycomb structure to dissipate kinetic energy through crushing. The DEA incorporates a unique flexible hinge design that allows the honeycomb to be packaged and stowed flat until needed for deployment. A variety of deployment options such as linear, radial, and/or hybrid methods can be used. Experimental evaluation of the DEA utilized a building block approach that included material characterization testing of its constituent, Kevlar -129 fabric/epoxy, and flexural testing of single hexagonal cells. In addition, the energy attenuation capabilities of the DEA were demonstrated through multi-cell component dynamic crush tests, and vertical drop tests of a composite fuselage section, retrofitted with DEA blocks, onto concrete, water, and soft soil. During each stage of the DEA evaluation process, finite element models of the test articles were developed and simulations were performed using the explicit, nonlinear transient dynamic finite element code, LS-DYNA. This report documents the results of the experimental evaluation that was conducted to assess the energy absorption capabilities of the DEA.

Jackson, Karen E.↗
NASA NTRS2012

Evaluation of Two Crew Module Boilerplate Tests Using Newly Developed Calibration Metrics

The paper discusses a application of multi-dimensional calibration metrics to evaluate pressure data from water drop tests of the Max Launch Abort System (MLAS) crew module boilerplate. Specifically, three metrics are discussed: 1) a metric to assess the probability of enveloping the measured data with the model, 2) a multi-dimensional orthogonality metric to assess model adequacy between test and analysis, and 3) a prediction error metric to conduct sensor placement to minimize pressure prediction errors. Data from similar (nearly repeated) capsule drop tests shows significant variability in the measured pressure responses. When compared to expected variability using model predictions, it is demonstrated that the measured variability cannot be explained by the model under the current uncertainty assumptions.

Horta, Lucas G.↗
NASA NTRS1989

Droplet combustion experiment drop tower tests using models of the space flight apparatus

The Droplet Combustion Experiment (DCE) is an experiment that is being developed to ultimately operate in the shuttle environment (middeck or Spacelab). The current experiment implementation is for use in the 2.2 or 5 sec drop towers at NASA Lewis Research Center. Initial results were reported in the 1986 symposium of this meeting. Since then significant progress was made in drop tower instrumentation. The 2.2 sec drop tower apparatus, a conceptual level model, was improved to give more reproducible performance as well as operate over a wider range of test conditions. Some very low velocity deployments of ignited droplets were observed. An engineering model was built at TRW. This model will be used in the 5 sec drop tower operation to obtain science data. In addition, it was built using the flight design except for changes to accommodate the drop tower requirements. The mechanical and electrical assemblies have the same level of complexity as they will have in flight. The model was tested for functional operation and then delivered to NASA Lewis. The model was then integrated into the 5 sec drop tower. The model is currently undergoing initial operational tests prior to starting the science tests.

Haggard, J. B.↗
NASA NTRS2012

Simulating the Impact Response of Full-Scale Composite Airframe Structures

NASA Langley Research Center obtained a composite helicopter cabin structure in 2010 from the US Army's Survivable Affordable Repairable Airframe Program (SARAP) that was fabricated by Sikorsky Aircraft Corporation. The cabin had been subjected to a vertical drop test in 2008 to evaluate a tilting roof concept to limit the intrusion of overhead masses into the fuselage cabin. Damage to the cabin test article was limited primarily to the roof. Consequently, the roof area was removed and the remaining structure was cut into test specimens including a large subfloor section and a forward framed fuselage section. In 2011, NASA and Sikorsky entered into a cooperative research agreement to study the impact responses of composite airframe structures and to evaluate the capabilities of the explicit transient dynamic finite element code, LS-DYNA®, to simulate these responses including damage initiation and progressive failure. Most of the test articles were manufactured of graphite unidirectional tape composite with a thermoplastic resin system. However, the framed fuselage section was constructed primarily of a plain weave graphite fabric material with a thermoset resin system. Test data were collected from accelerometers and full-field photogrammetry. The focus of this paper will be to document impact testing and simulation results for the longitudinal impact of the subfloor section and the vertical drop test of the forward framed fuselage section.

Fasanella, Edwin L.↗
NASA NTRS1966

Spiral spring/strain gage combination accurately measures shock induced deflection

Spiral springs equipped with strain gages which are hard-wired to readout instrumentation, measure deflection between two relatively inaccessible surfaces in a drop test that causes them to close to near flatness. This technique has been successfully used on Apollo drop tests to measure deflection between aft bulkhead and heatshield.

Berven, B. R.↗
NASA NTRS2004

Development of an LS-DYNA Model of an ATR42-300 Aircraft for Crash Simulation

This paper describes the development of an LS-DYNA simulation of a vertical drop test of an ATR42-300 twin-turboprop high-wing commuter-class airplane. A 30-ft/s drop test of this aircraft was performed onto a concrete impact surface at the FAA Technical Center on July 30, 2003. The purpose of the test was to evaluate the structural response of a commuter-class aircraft when subjected to a severe, but survivable, impact. The aircraft was configured with crew and passenger seats, anthropomorphic test dummies, forward and aft luggage, instrumentation, and onboard data acquisition systems. The wings were filled with approximately 8,700 lb. of water to represent the fuel and the aircraft weighed a total of 33,200 lb. The model, which consisted of 57,643 nodes and 62,979 elements, was developed from direct measurements of the airframe geometry, over a period of approximately 8 months. The seats, dummies, luggage, fuel, and other ballast were represented using concentrated masses. Comparisons were made of the structural deformation and failure behavior of the airframe, as well as selected acceleration time history responses.

Jackson, Karen E.↗
NASA NTRS2019

Modal Analysis of a Two-Parachute System

The Orion capsule is designed to land under a nominal configuration of three main parachutes; however, the system is required to be fault tolerant and land successfully if one of the main parachutes fails to open. The Capsule Parachute Assembly System (CPAS) Team performed a series of drop tests in order to characterize the performance of the system with two main parachutes. During the series of drop tests, several distinct dynamical modes were observed. The most consequential of these is the pendulum mode. Three other modes are benign: flyout (scissors), maypole, and breathing. The actual multi-body system is nonlinear, flexible, and possesses significant cross-coupling. Rather than perform analysis of this highly complex system directly, we conduct analysis of each dynamical mode observed during flight, based on first principles. This approach is analogous to traditional aircraft flight dynamics analysis in which the full nonlinear behavior of the airframe is decomposed into longitudinal dynamics (phugoid and short-period modes) and lateral dynamics (spiral, roll-subsidence, and dutch-roll modes). This analysis is intended to supplement multi-body nonlinear simulations in order to provide further insight into the system.

Pei, Jing↗
NASA NTRS1973

Implementation and extension of the impulse transfer function method for future application to the space shuttle project. Volume 1: Analysis and correlation studies

Computer programming, data processing, and a correlation study that employed data collected in the first phase test were used to demonstrate that standard test procedures and equipment could be used to collect a significant number of transfer functions from tests of the Lunar Module test article LTA-11. The testing consisted of suspending the vehicle from the apex fittings of the outrigger trusses through a set of air springs to simulate the free-free state. Impulsive loadings were delivered, one at a time, at each of the landing gear's attachment points, in three mutually perpendicular directions; thus a total of 36 impulses were applied to the vehicle. Time histories of each pulse were recorded on magnetic tape along with 40 channels of strain gage response and 28 channels of accelerometer response. Since an automated data processing system was not available, oscillograph playbacks were made of all 2400 time histories as a check on the validity of the data taken. In addition, one channel of instrumentation was processed to determine its response to a set of forcing functions from a prior LTA-11 drop test. This prediction was compared with drop test results as a first measure of accuracy.

Mantus, M.↗
NASA NTRS1981

Determination of crash test pulses and their application to aircraft seat analysis

Deceleration time histories (crash pulses) from a series of twelve light aircraft crash tests conducted at NASA Langley Research Center (LaRC) were analyzed to provide data for seat and airframe design for crashworthiness. Two vertical drop tests at 12.8 m/s (42 ft/s) and 36 G peak deceleration (simulating one of the vertical light aircraft crash pulses) were made using an energy absorbing light aircraft seat prototype. Vertical pelvis acceleration measured in a 50 percentile dummy in the energy absorbing seat were found to be 45% lower than those obtained from the same dummy in a typical light aircraft seat. A hybrid mathematical seat-occupant model was developed using the DYCAST nonlinear finite element computer code and was used to analyze a vertical drop test of the energy absorbing seat. Seat and occupant accelerations predicted by the DYCAST model compared quite favorably with experimental values.

Alfaro-Bou, E.↗
NASA NTRS1977

Experimental and analytical determination of characteristics affecting light aircraft landing-gear dynamics

An experimental and analytical investigation was conducted to determine which characteristics of a light aircraft landing gear influence gear dynamic behavior significantly. The investigation focused particularly on possible modification for load control. Pseudostatic tests were conducted to determine the gear fore-and-aft spring constant, axial friction as a function of drag load, brake pressure-torque characteristics, and tire force-deflection characteristics. To study dynamic tire response, vertical drops were conducted at impact velocities of 1.2, 1.5, and 1.8 m/s onto a level surface; to determine axial-friction effects, a second series of vertical drops were made at 1.5 m/s onto surfaces inclined 5 deg and 10 deg to the horizontal. An average dynamic axial-friction coefficient of 0.15 was obtained by comparing analytical data with inclined surface drop test data. Dynamic strut bending and associated axial friction were found to be severe for the drop tests on the 10 deg surface.

Fasanella, E. L.↗
NASA NTRS1953

Analysis of Landing-Gear Behavior

This report presents a theoretical study of the behavior of the conventional type of oleo-pneumatic landing gear during the process of landing impact. The basic analysis is presented in a general form and treats the motions of the landing gear prior to and subsequent to the beginning of shock-strut deflection. The applicability of the analysis to actual landing gears has been investigated for the particular case of a vertical landing gear in the absence of drag loads by comparing calculated results with experimental drop-test data for impacts with and without tire bottoming. The calculated behavior of the landing gear was found to be in good agreement with the drop-test data.

Milwitzky, Benjamin↗
NASA NTRS2019

Orion Capsule Parachute Assembly System (CPAS) Overload Testing Approach and Results

The qualification of the Orion Capsule Parachute Assembly System (CPAS) system includes exposure to loads and dynamic pressures above the required values as validation of the parachutes' structural integrity. As outlined in the certification plan, each of the four parachutes of the system are to be subjected to 110% of their respective maximum dynamic pressure requirements. The Main and Drogue parachutes have satisfied this overload condition in drop testing and due to cost and schedule constraints, the Forward Bay Cover Parachute (FBCP) and Pilot parachute were subjected to the overload condition in the ground testing described in this document. The test objectives and pass/fail criteria were established and require the parachutes to achieve and maintain a target riser load (associated with a minimum of 110% dynamic pressure overload) for a minimum of three seconds while sustaining no failures of any structural members (vent hoop, radials, suspension line) or any damage which propagates into catastrophic failure of the canopy. Considering the assumptions and limitations associated with the ground testing (primarily non-uniform flow field of the ground test system and variations in parachute manufacturing), a method of establishing the desired overload condition was determined by the technical community and covers the 2-sigma bounds of the drag area distribution derived from drop testing. On June 27, 2017 the testing was executed at the High Velocity Airflow System (HiVAS) facility located at the Weapon Survivability Laboratory (WSL) at the Naval Air Warfare Center, Weapons Division (NAWCWD) China Lake. Engineering Development Unit (EDU) parachutes were used as pathfinders to gain experience with achieving the test conditions. Additional runs were executed to measure the airflow at the same location as the canopy skirt, although this data is not required to satisfy the test objectives and parachute pass/fail criteria. The qualification parachutes were successfully exposed to the target conditions and sustained only minor damage.

Daum, Jared S.↗
NASA NTRS2001

The Analysis and Modeling of the Deployment of NASA's X-38 Parafoil

NASA is currently working on developing the X-38 Crew Return Vehicle for the Internati6nal Space Station (ISS). The aerodynamics of the X-38 and its enormous 7500 square ft parafoil are extremeJy complicated and must be understood and modeled accurately before the vehicle is actually used for human space flight. A large amount of analysis has been performed on the steady state regions of the flight profile when the parafoil is already open. However, the deployment region of the flight profile has not been analyzed in much depth and is a particularly complicated dynamic flight period. During deployment, the X-38 system has its parafoil open up to its full area in five stages over a period of 20-30 seconds. The vehicle transitions from angles of attack around 90 deg to 0 deg in about two seconds and is extremely dynamic. This paper will detail the analysis work done to generate accurate flight profile characteristics of the deployment from flight data from vehicle test drops. Additionally, a computer simulation tool for steady state flight was modified to analyze and model the parafoil deployment. Eventually, a computer model was produced that generated accurate representations of the parafoil deployment dynamics for the vehicle test drops to date.

Ranier, Chris↗
NASA NTRS1972

Wind-tunnel simulation of store jettison with the aid of magnetic artificial gravity

A method employed in the simulation of jettison of stores from aircraft involving small scale wind-tunnel drop tests from a model of the parent aircraft is described. Proper scaling of such experiments generally dictates that the gravitational acceleration should ideally be a test variable. A method of introducing a controllable artificial component of gravity by magnetic means has been proposed. The use of a magnetic artificial gravity facility based upon this idea, in conjunction with small scale wind-tunnel drop tests, would improve the accuracy of simulation. A review of the scaling laws as they apply to the design of such a facility is presented. The design constraints involved in the integration of such a facility with a wind tunnel are defined. A detailed performance analysis procedure applicable to such a facility is developed. A practical magnet configuration is defined which is capable of controlling the strength and orientation of the magnetic artificial gravity field in the vertical plane, thereby allowing simulation of store jettison from a diving or climbing aircraft. The factors involved in the choice between continuous or intermittent operation of the facility, and the use of normal or superconducting magnets, are defined.

Stephens, T.↗
NASA NTRS2010

Parachute Drag Model

DTV-SIM is a computer program that implements a mathematical model of the flight dynamics of a missile-shaped drop test vehicle (DTV) equipped with a multistage parachute system that includes two simultaneously deployed drogue parachutes and three main parachutes deployed subsequently and simultaneously by use of pilot parachutes. DTV-SIM was written to support air-drop tests of the DTV/parachute system, which serves a simplified prototype of a proposed crew capsule/parachute landing system.

Cuthbert, Peter↗
NASA NTRS2003

Comparisons of the Impact Responses of a 1/5-Scale Model and a Full-Scale Crashworthy Composite Fuselage Section

A 25-fps vertical drop test of a 1/5-scale model composite fuselage section was conducted to replicate a previous test of a full-scale fuselage section. The purpose of the test was to obtain experimental data characterizing the impact response of the 1/5-scale model fuselage section for comparison with the corresponding full-scale data. This comparison is performed to assess the scaling procedures and to determine if scaling effects are present. For the drop test, the 1/5-scale model fuselage section was configured in a similar manner as the full-scale section, with lead masses attached to the floor through simulated seat rails. Scaled acceleration and velocity responses are compared and a general assessment of structural damage is made. To further quantify the data correlation, comparisons of the average acceleration data are made as a function of floor location and longitudinal position. Also, the percentage differences in the velocity change (area under the acceleration curve) and the velocity change squared (proportional to kinetic energy) are compared as a function of floor location. Finally, correlation coefficients are calculated for corresponding 1/5- and full-scale data channels and these values are plotted versus floor location. From a scaling perspective, the differences between the 1/5- and full-scale tests are relatively small, indicating that appropriate scaling procedures were used in fabricating the test specimens and in conducting the experiments. The small differences in the scaled test data are attributed to minor scaling anomalies in mass, potential energy, and impact attitude.

Jackson, Karen E.↗
NASA NTRS1984

Transonic wind-tunnel investigation of the Galileo Probe parachute configuration

Wind-tunnel tests have been made of 1/4-scale and 1/2-scale models of the Galileo Probe conical ribbon-parachute at flight conditions. For the Galileo mission, the parachute is deployed behind a blunt shape at transonic speed. The investigation was initiated to verify the solutions to the delayed main-parachute opening with squidding that was observed in the 1982 Galileo Probe system balloon drop test. In addition to varying model scale, the forebody shape, angle of attack, dynamic pressure, Mach number, and canopy trailing distance behind the forebody were varied to determine their effect on parachute performance. Both steady-state and deployment tests were conducted. Parachute drag was measured and was seen to degrade severely at canopy trailing distances of 5.5 and 7 forebody diameters. Performance was shown to be good at the trailing distances of 9 and 11 diameters. A second balloon drop test demonstrated the desired parachute performance at the system level.

Corridan, R. E.↗