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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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NASA NTRS2011

Active Response Gravity Offload System

The Active Response Gravity Offload System (ARGOS) provides the ability to simulate with one system the gravity effect of planets, moons, comets, asteroids, and microgravity, where the gravity is less than Earth fs gravity. The system works by providing a constant force offload through an overhead hoist system and horizontal motion through a rail and trolley system. The facility covers a 20 by 40-ft (approximately equals 6.1 by 12.2m) horizontal area with 15 ft (approximately equals4.6 m) of lifting vertical range.

Valle, Paul↗

NASA NTRS2015

Auralization of Tonal Rotor Noise Components of a Quadcopter Flyover

The capabilities offered by small unmanned vertical lift aerial vehicles, for example, quadcopters, continue to captivate entrepreneurs across the private, public, and civil sectors. As this industry rapidly expands, the public will be exposed to these devices (and to the noise these devices generate) with increasing frequency and proximity. Accordingly, an assessment of the human response to these machines will be needed shortly by decision makers in many facets of this burgeoning industry, from hardware manufacturers all the way to government regulators. One factor of this response is that of the annoyance to the noise that is generated by these devices. This paper presents work currently being pursued by NASA toward this goal. First, physics-based (CFD) predictions are performed on a single isolated rotor typical of these devices. The result of these predictions are time records of the discrete tonal components of the rotor noise. These time records are calculated for a number of points that appear on a lattice of locations spread over the lower hemisphere of the rotor. The source noise is then generated by interpolating between these time records. The sound from four rotors are combined and simulated-propagation techniques are used to produce complete flyover auralizations.

Christian, Andrew W.↗

NASA NTRS2015

Case Studies for the Statistical Design of Experiments Applied to Powered Rotor Wind Tunnel Tests

The application of statistical Design of Experiments (DOE) to helicopter wind tunnel testing was explored during two powered rotor wind tunnel entries during the summers of 2012 and 2013. These tests were performed jointly by the U.S. Army Aviation Development Directorate Joint Research Program Office and NASA Rotary Wing Project Office, currently the Revolutionary Vertical Lift Project, at NASA Langley Research Center located in Hampton, Virginia. Both entries were conducted in the 14- by 22-Foot Subsonic Tunnel with a small portion of the overall tests devoted to developing case studies of the DOE approach as it applies to powered rotor testing. A 16-47 times reduction in the number of data points required was estimated by comparing the DOE approach to conventional testing methods. The average error for the DOE surface response model for the OH-58F test was 0.95 percent and 4.06 percent for drag and download, respectively. The DOE surface response model of the Active Flow Control test captured the drag within 4.1 percent of measured data. The operational differences between the two testing approaches are identified, but did not prevent the safe operation of the powered rotor model throughout the DOE test matrices.

Overmeyer, Austin D.↗

NASA NTRS2017

Greased Lightning (GL-10) Performance Flight Research: Flight Data Report

Modern aircraft design methods have produced acceptable designs for large conventional aircraft performance. With revolutionary electronic propulsion technologies fueled by the growth in the small UAS (Unmanned Aerial Systems) industry, these same prediction models are being applied to new smaller, and experimental design concepts requiring a VTOL (Vertical Take Off and Landing) capability for ODM (On Demand Mobility). A 50% sub-scale GL-10 flight model was built and tested to demonstrate the transition from hover to forward flight utilizing DEP (Distributed Electric Propulsion)[1][2]. In 2016 plans were put in place to conduct performance flight testing on the 50% sub-scale GL-10 flight model to support a NASA project called DELIVER (Design Environment for Novel Vertical Lift Vehicles). DELIVER was investigating the feasibility of including smaller and more experimental aircraft configurations into a NASA design tool called NDARC (NASA Design and Analysis of Rotorcraft)[3]. This report covers the performance flight data collected during flight testing of the GL-10 50% sub-scale flight model conducted at Beaver Dam Airpark, VA. Overall the flight test data provides great insight into how well our existing conceptual design tools predict the performance of small scale experimental DEP concepts. Low fidelity conceptual design tools estimated the (L/D)( sub max)of the GL-10 50% sub-scale flight model to be 16. Experimentally measured (L/D)( sub max) for the GL-10 50% scale flight model was 7.2. The aerodynamic performance predicted versus measured highlights the complexity of wing and nacelle interactions which is not currently accounted for in existing low fidelity tools.

McSwain, Robert G.↗

NASA NTRS2017

Evaluation of a Variable Thickness Hybrid Composite Bull Gear

For several years, NASA Glenn Research Center and the U.S. Army Research Laboratory have been investigating hybrid (composite/steel) gear technology for use in vertical lift drive systems. The hybrid gear concept replaces the structural portion of a gear between the shaft and the gear rim with a lightweight carbon fiber composite, in an effort to reduce the overall weight of a gear and increase the drive system power density. Past research includes both small-scale and large-scale hybrid gear concepts, all of which have a constant composite thickness throughout. The design described in this paper is of a variable thickness, such that the composite is thickest at the inner diameter and this thickness is gradually reduced toward the outer diameter. The resulting "stair stepped" design stems from dropping plies of the braided carbon fiber prepreg composite fabric gradually with increased radius. Additionally, the interlock pattern at the inner metallic adapter was adjusted slightly from previous designs to obtain a better stress distribution on the inner metallic adapter. The manufactured variable thickness web was tested both in static torsion tests and operationally in a relevant gearbox environment. The results of these experiments will be presented and compared to a baseline steel configuration.

Gears; Drive Systems; Rotorcraft Propulsion;↗

NASA NTRS2018

Two-Speed Rotorcraft Research Transmission Power-Loss Associated with the Lubrication and Hydraulic Rotating Feed-Through Design Feature

An investigation was completed into the power loss associated with a rotating feed-through (RFT) design feature used to transfer lubrication and a hydraulic control signal from the static reference frame to a rotating reference frame in the NASA GRC two-speed transmission tests conducted in the Variable-Speed Drive Test Rig. The RFT feature, not commercially available, was created specifically for this research project and is integral to all two-speed transmission configurations tested, as well as a variant concept design for a geared variable-speed transmission presented at AHS Forum 71 in 2015. The experimental set-up and results from measurements in the isolated rotating-feed-through (RFT) experiments are presented. Results were used in an overall power loss assessment for a scaled conceptual 1,000 horsepower inline concentric two-speed transmission to support a NASA Revolutionary Vertical Lift Technologies (RVLT) Technical Challenge, demonstrating 50% speed change with less than 2% power loss while maintaining current power-to-weight ratios.

Rotorcraft↗

NASA NTRS2018

Electric Motor Noise for Small Quadcopters: Part I - Acoustic Measurements

There is increased interest in using electric motors to drive propulsors across a range of small air vehicle classes. Applications include both vertical lift and conventional takeoff and landing systems for Small Unmanned Aircraft Systems. Mission profiles call for integrating these systems into urban airspaces exposing populated areas to new noise sources. In addition to the propulsor noise from rotors and propellers, electric motors are expected to contribute to the overall sound levels and possibly human annoyance. This work presents acoustic measurements of electric motors used for small quadcopters to characterize the sound and identify sources with and without a propeller. Free field microphone measurements were used to determine directivity and a phased microphone array was used to identify sound sources. A companion paper (Part II – Source Characteristics and Prediction) compares the far field results with current probe measurements of the signal driving the motor, the structural response of the motor case, and describes prediction methods of electric motor noise.

Aircraft Noise↗

NASA NTRS2018

Two-Speed Rotorcraft Research Transmission Power-Loss Associated with the Lubrication and Hydraulic Rotating Feed-Through Design Feature

Rotorcraft↗

NASA NTRS2018

Multidisciplinary Optimization of Urban-Air-Mobility Class Aircraft Trajectories with Acoustic Constraints

The design and analysis of on-demand mobility class vehicles will require thorough acoustic analysis to ensure that more numerous aircraft can operate in densely populated areas without causing excessive levels of noise. This work is a step towards a comprehensive ODM vehicle analysis capability. The authors use 6DOF equations of motion to model the electric quad-rotor concept developed by NASA's Revolutionary Vertical Lift Technologies program. As a first step towards acoustic analysis, this trajectory is coupled to an acoustic model that tracks the sound pressure level perceived by an acoustic observer on the ground. The results show that the approach is successful in finding trajectories that minimize total propulsive impulse while obeying limits imposed on the sound pressure level. Future work will involve adding acoustic analysis of increasing fidelity and tying the resulting trajectories to the performance of the electric propulsion system.

electric aircraft↗

NASA NTRS2018

Two-Speed Rotorcraft Research Transmission Power-Loss Associated with the Lubrication and Hydraulic Rotating Feed-Through Design Feature

Rotorcraft↗

NASA NTRS2018

Evaluation of a Variable Thickness Hybrid Composite Bull Gear

For several years, NASA Glenn Research Center and the U.S. Army Research Laboratory have been investigating hybrid (compositesteel) gear technology for use in vertical lift drive systems. The hybrid gear concept replaces the structural portion of a gear between the shaft and the gear rim with a lightweight carbon fiber composite, in an effort to reduce the overall weight of a gear and increase the drive system power density. An overview of the concept of the hybrid gear design is described in Ref. 1, 2, and 3. The research presented in these references includes both small-scale and large-scale hybrid gear concepts all of which have a constant composite thickness throughout. The design described in this paper is of a variable thickness, such that the composite is thickest at the inner diameter and this thickness is gradually reduced toward the outer diameter. The resulting stair stepped design stems from dropping plies of the braided carbon fiber composite fabric gradually with increased radius. Additionally, the interlock pattern at the inner metallic adapter was adjusted slightly from previous designs to obtain a better stress distribution on the inner metallic adapter. The manufactured variable thickness web was tested both in static torsion tests and operationally in a relevant gearbox environment. The results of these experiments will be presented and compared to a baseline steel configuration.

Rotorcraft Propulsion↗

NASA NTRS2018

Electric Motor Noise from Small Quadcopters: Part 1 - Acoustic Measurements

There is increased interest in using electric motors to drive propulsors across a range of small air vehicle classes. Applications include both vertical lift and conventional takeoff and landing systems for Small Unmanned Aircraft Systems. Mission profiles call for integrating these systems into urban airspaces exposing populated areas to new noise sources. In addition to the propulsor noise from rotors and propellers, electric motors are expected to contribute to the overall sound levels and possibly human annoyance. This work presents acoustic measurements of electric motors used for small quadcopters to characterize the sound and identify sources with and without a propeller. Free field microphone measurements were used to determine directivity and a phased microphone array was used to identify sound sources. A companion paper (Part II - Source Characteristics and Prediction) compares the far field results with current probe measurements of the signal driving the motor, the structural response of the motor case, and describes prediction methods of electric motor noise.

Electric Propulsion↗

NASA NTRS2018

Adventures in Low Disc Loading VTOL Design

This memoir covers the first eight years of my 37 year career in VTOL aircraft design. It starts with family and how I came to be an engineer with a passion for aviation and a desire to make a difference. At MIT I acquired a solid understanding of basic physics, learned the basics of the various engineering disciplines and gained design experience. After over a decade on the East Coast I was homesick for Northern California. I decided to take a chance on working for the government instead of industry in order to return home. I was hired by Dr. Richard M. Carlson in March 1975 and joined a wonderful Army/NASA technical environment. The Interservice Helicopter Commonality Study was an important introduction to Joint Service aircraft design. The Advanced Attack Helicopter Source Selection Evaluation Board was an opportunity to learn acquisition system fundamentals and to lead a small team in a major technical evaluation. The Advanced Scout Helicopter Concept Formulation was an opportunity to learn how an aircraft development program is created and it formed a partnership between Dr. Carlson's Labs and Charlie Crawford's Development and Qualification directorate. The Army was Executive Service for the first year (1982) of the Joint Services Advanced Vertical Lift Aircraft (JVX) program. The JVX Joint Technology Assessment concluded that there was at least one design configuration, the tilt rotor, which could satisfy all JVX mission requirements with a high degree of inter-service commonality. The Navy became Executive Service at the end of the year and promptly released a JVX RFP to industry. This RFP resulted in the V-22 Osprey tilt rotor as the third type of VTOL aircraft to enter production and service. I was very lucky to have a useful role early in this program.

VTOL Design↗

NASA NTRS2018

What is a Tiltrotor? A Fundamental Reexamination of the Tiltrotor Aircraft Design Space

The objective of this work is to fundamentally reexamine the design space of tiltrotor aircraft beyond the very successful conventional vehicle configuration with tractor-type twin proprotors that are nacelle-mounted at the wing tips. Previously proposed alternate tiltrotor configurations include the Bell quad-tiltrotor and the Augusta Westland ERICA hybrid tiltrotor/tiltwing concepts. More recently, arguably alternate tiltrotor configurations include the NASA Langley "Puffin" and the Joby Aviation S-2 concepts. This work seeks to define a broad aircraft design space for alternate tiltrotor configurations. Being doing so, it is hoped this work will not only provide design inspiration for future aircraft developers but to also help realize new applications and missions for both passenger-carrying vehicles and vertical lift UAVs (Unmanned Aerial Vehicles) might one day be successfully enabled.

Reexamination↗

NASA NTRS2017

Tiltrotor Conceptual Design

This year end progress report summarizes our engineering study of a large, VTOL civil transport that we began in August 2015. The task has been to follow up on work reported in Reference 1, which described a NASA, 2005 design study showing that a 120 passenger, tiltrotor aircraft capable of cruising at 350 knots at 30,000 feet was quite feasible. The objective of our task this year has been to investigate the feasibility of a 120 passenger, tiltrotor aircraft capable of cruising at 425 to 450 knots at altitude and having VSTOL capability at Denver (i.e., 5,000 feet) with an outside air temperature (OAT) of 95°F. A corollary to our work has been to examine the suitability of the engineering tools available to conduct the concept design study we have begun. We have relegated two key pieces of corollary work to an appendix and used the body of this report to transmit progress in our preliminary performance trend studies. By way of background, in January of 2016, Mr. Harris presented a paper titled The VSTOL Performance Gap at the AHS Technical Meeting on Aeromechanics Design for Vertical Lift. This presentation is included in this year end report as Appendix A. A key concluding chart in that presentation is repeated here as Fig. 1. The Rotorcraft Branch at NASA Ames was already studying a tiltrotor suited for the regional carrier routes, but no effort beyond the 2005 results reported in Ref. 1 was going on. Therefore, we took on the task of extending the 350 knot, 120 passenger tiltrotor studies up to speeds associated with major airline routes.

Conceptual Design↗

NASA NTRS2019

NASA Workshop on Low Ice Adhesion Materials

The first NASA Workshop on Low Ice Adhesion Materials was held on Thursday, August 10, 2017, at the Ohio Aerospace Institute in Cleveland, Ohio. This meeting allowed government, industry, and academia to meet in a collaborative environment to discuss the future of “icephobics” research for inflight icing. NASA presented its ongoing research, and organizations that currently have partnerships with NASA presented their recent findings. Presenters from academia included Iowa State University, Mississippi State University, Pennsylvania State University, and the University of Michigan. Presenters from industry included United Technologies Aerospace Systems; Nanosonic, Inc.; and NEI Corporation. Researchers from NASA Glenn Research Center, NASA Langley Research Center, and the Office of Naval Research also shared their current research. There were over 60 participants who attended the conference plus more than 10 who participated remotely. The meeting was highly successful, and although a second such conference was proposed, it is anticipated that future technical presentations on the subject(s) will take place in other venues. Presentations from this workshop that are suitable for public release are included in this document. This effort supports both the Advanced Air Transport Technology (AATT) Project and the Revolutionary Vertical Lift Technology (RVLT) Project.

Kreeger, Richard E.↗

NASA NTRS2019

Portable Laser Guided Robotic Metrology System

This paper introduces the new Portable Laser Guided Robotic antenna range (PLGR) at the National Aeronautics and Space Administration's (NASA) Glenn Research Center. Previous work used industrial robots in fixed facilities to characterize antennas and required fixtures that do not lend themselves to portable applications.NASA's PLGR system is designed for in-situ antenna measurements at a remote site. The system consists of a robot arm mounted on a vertical lift and a laser tracker, each on a portable base. The lift and laser tracker enable scanning a surface larger than the robot's reach. To accomplish this the robot first collects all points within its reach, then the system is moved and the laser tracker is used to relocate the robot before additional points are captured.The PLGR architecture will be discussed including how safety systems and path planning are combined to effectively characterize antennas. Software was written in high level languages for flexible integration of vector network analyzers and antenna controllers. Lastly, data will be shown to demonstrate the system functionality and accuracy.

Slater, Peter A.↗

NASA NTRS2019

NASA Electrified Aircraft Propulsion Efforts

NASA's broad investments in Electrified Aircraft Propulsion (EAP) are reviewed in this paper. NASA investments are guided by an assessment of potential market impacts, technical key performance parameters, and technology readiness attained through a combination of studies, enabling fundamental research, and flight research. NASA has determined that the impact of EAP varies by market and NASA is considering three markets: national/international, on-demand mobility, and short haul regional air transport. Flight research is underway to demonstrate integrated solutions and inform standards and certification processes. This paper focuses on the vehicle related activities, however there are related NASA activities in air space management and vehicle autonomy activities as well as a breakthrough technology project called the Convergent Aeronautics Solutions Project. A key finding is that sufficient technical advances in key areas have been made which indicate EAP is a viable technology for aircraft. Significant progress has been made to reduce EAP adoption barriers and further work is needed to transition the technology to a commercial product and improve the technology so it is applicable to large transonic aircraft. This paper will review the activities of the Hybrid Gas Electric Subproject of the Advanced Air Transport Technology Project, the Revolutionary Vertical Lift Technology Project, and the X-57 Flight Demonstration Project, and discuss the potential EAP benefits for commercial and military applications.

Jansen, Ralph H.↗