Power Quality Analysis for a High Voltage Power System for Urban Air Mobility Application
This presentation is for the AIAA Electric Aircraft Technologies Symposium (EATS).
Nuha S. Nawash↗
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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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Revolutionary Vertical Lift Technology Project
An overview of the RVLT project and NASA direction for Urban Air Mobility
Urban Air Mobility↗
Atoms to Aircraft to Spacecraft
The next generation of aerospace systems requires materials and structures that combine high performance at high utilization in short missions with the possibility of high rate production, without excessive non-recurring cost, to allow for rate flexibility and shorter structural life cycles. The development of materials and structures that offer this flexibility in rate without negatively influencing performance and economic viability will require a matching and overlapping experimental and computational design approach. The objective is to go from Atom to Airframe to Spaceframe for thermoplastic unidirectional tape based fastener-free assemblies. Thermoplastic composites are chosen as the focus because these materials allow for reversible fusion bonding in every stage of their life cycle after synthesis. Our strategy is to combine multi-scale computational approaches with multi-scale experimental activities to develop an understanding of and capabilities to manufacture custom unidirectional thermoplastic tape. This tape will be the basis for our high-rate multiple-technology manufacturing approach validated by the production of two representative demonstrators for urban air mobility vehicle structures. The multi-disciplinary team will work in an integrated manner to effectively combine computational approaches with experimental approaches at each stage of characteristic manufacturing flows. The team aims for tools and technology to quantify the thermo-rheological aspects of unidirectional tape-based production and assembly of aerospace quality thermoplastic components as well as for validated tools for unidirectional tape-based thermoplastic preform and part design and manufacture. The work will be used to design and build two demonstration structural parts characteristic for urban air mobility vehicles.
Paul Ziehl↗
Practical Conceptual Design of Quieter Urban VTOL Aircraft
A toolchain and process for conceptual design of VTOL rotorcraft, employing low- and mid-fidelity tools is presented. The approach is capable of providing more quantitatively-credible trades between noise, size, and cost metrics than the methods commonly used for conceptual design. In addition to a general conceptual design tool, the approach employs comprehensive analysis for trim, blade motion, and airloads; these are then used by acoustic analysis software to develop source sound, propagate it, and calculate noise metrics. A key aspect of the approach is flexibility to assess varied aircraft types and different technologies and design features. Vehicles are sized using a representative Urban Air Mobility design mission. Demonstration cases are presented for a single main rotor helicopter, quadrotor, side-by-side helicopter, and lift+cruise aircraft. Noise metrics used for demonstration are the FAA/EASA certification Effective Perceived Noise Levels for takeoff, flyover, and approach. The concept aircraft in this study are shown to achieve reductions in noise relative the initial design points, with changes in mission performance and cost as a consequence. Many of the designs are predicted to be tens of EPNdB quieter in the certification metrics than existing helicopters.
Conceptual Design↗
Revolutionary Vertical Lift Technology Lift + Cruise Concept Vehicle Powertrain Dynamic Model
The Lift + Cruise (L+C) is one of several Revolutionary Vertical Lift Technology (RVLT) concept aircraft identified by NASA to investigate Urban Air Mobility (UAM) requirements. This six-passenger vehicle has a conventional tube-and-wing configuration, but with eight lift rotors (four on each wing) and a pusher rotor on the tail. This arrangement allows it to take off and land vertically as well as fly like an airplane. This report presents a novel dynamic model of the L+C powertrain built using the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) and the Electrical Modeling and Thermal Analysis Toolbox (EMTAT), both of which are NASA-developed toolboxes, and together are capable of modeling hybrid-electric powertrain architectures. This research effort models the complex behavior of the powertrain at the mechanical timescale (15 to 20 ms). The model consists of a turboshaft engine, generator, direct current bus, energy storage management system, gearboxes, and electric propulsor systems coupled together to create a dynamic model that mimics the operation of the multidomain powertrain. Two control algorithms, designed to equalize the power consumed to the power produced, are compared to assess their practicality: (1) independent proportional-integral (PI) control and (2) linear quadratic integral regulator (LQIR) control. Simulation results highlight the key features present in the model and demonstrate its operation under the two control schemes.
revolutionary vertical lift technology↗
Progress in Fire Detection and Suppression Technology for Future Space Missions
Fire intervention technology (detection and suppression) is a critical part of the strategy of spacecraft fire safety. This paper reviews the status, trends, and issues in fire intervention, particularly the technology applied to the protection of the International Space Station and future missions beyond Earth orbit. An important contribution to improvements in spacecraft fire safety is the understanding of the behavior of fires in the non-convective (microgravity) environment of Earth-orbiting and planetary-transit spacecraft. A key finding is the strong influence of ventilation flow on flame characteristics, flammability limits and flame suppression in microgravity. Knowledge of these flow effects will aid the development of effective processes for fire response and technology for fire suppression.
Friedman, Robert↗
Advanced Technologies for Artificial Intelligence in Flight Applications
On-board estimation, navigation and control technologies addressing safety problems of robotic flight operations in urban environment with atmospheric hazards and component failures contingencies are presented.
trajectory generation↗
Concept Evaluation: NASA Reference Model 2-Side by Side
Urban Air Mobility (UAM) is an up and coming topic in the world of aerosciences. A variety of companies, most notably Uber, has begun working towards making air taxis a regular part of day to day life. However, the implementation of this system into society will require a significant amount of work: making helicopters that can handle these flights and operate safely in urban environments, having landing zones, and working out new technologies to lower costs. NASA has also taken interest in this new idea and has formed a focus group of interns to tackle some of these problems. They have started by designing a few concept models for what these air taxis could look like, focusing on low noise, multiple passenger configurations, and the potential for electric or hybrid helicopters. One particular model is known as NR2, or the "Side by Side," which features two rotors spinning in opposite directions. Though these models are purely conceptual at this point, understanding the real-world aerodynamics and performance of this model is crucial to its future development. Using a program known as Rotorcraft Computational Fluid Dynamics (RotCFD), the performance characteristics of the rotors and aircraft, such as the lift, drag, thrust and power can be determined. These simulations can be run in a variety of flight configurations, with hover, forward flight, and climb being focused on in this study. The rotor collective angle can also be changed and used to get results about the lift and drag for the blades and the model body. These simulations can provide information for future model construction and wind tunnel testing.
Reference Model↗
Effectiveness of Redundant Communications Systems in Maintaining Operational Control of Small Unmanned Aircraft
NASA has been researching prototype technologies for an Unmanned Aircraft System (UAS) Traffic Management (UTM) system to facilitate enabling of safe and efficient civilian low-altitude airspace and UAS operations, in a series of Technical Capability Levels (TCL) activities that are increasingly complex. In TCL1, completed in 2015, visual line-of-sight operations such as agriculture, firefighting and infrastructure monitoring were addressed with a focus on geofencing and operations scheduling. Technologies and requirements needed for beyond visual line-of-sight (BVLOS) operations in sparsely populated areas were examined in TCL2 in 2016, and those for operations over moderately populated areas in TCL3 in 2017 and 2018. TCL4 will build on the earlier TCLs and focus on technologies and requirements for operations in higher-density urban areas for tasks such as news gathering, package delivery and for managing large-scale contingencies. This paper describes a communications test conducted in TCL3 and discusses insights gained from the test. In the test, operators were directed to equip UAS with redundant Command and Control (C2) communications systems, send a maneuver command to Unmanned Aircraft (UA) via the primary system, then verify execution of the sent command. This exercise was repeated with each redundant system. The test was designed to assess effectiveness of redundant C2 systems in maintaining operational control of UA. Several UAS were configured with varying arrangements to achieve redundancy, including two identical radio modems using the same frequency band, WiFi and Long-Term Evolution (LTE) cellular modems, etc. From the test, digital data such as time maneuver command sent, time maneuver verified, etc., were collected. Descriptions of methods to detect loss of C2 communications and contingency steps for such event were collected and assessed. The final paper will include a detailed analysis of the collected data leading to the following insights. First, effectiveness of redundant C2 systems depends on several factors, such as operational environment and communications service availability. For example, use of two identical point-to-point radio to connect operator and UA on the same frequency band can be effective in mitigating radio malfunction when operating in an environment where possibility of Radio Frequency (RF) interference is low, such as over open plains. However, the same arrangement may not be effective where high level of RF transmissions in broad spectrum ranges can be expected, such as over or near urban areas. For redundant systems that consist of external communications services, such as cellular and satellite communications network, redundancy is maintained only in the areas where more than one services are available. Therefore, UAS operators should have the means to plan for and monitor the performance of external communications services they are relying on to control UA. Second, communications performance needs, such as the minimum data transfer rate and the maximum tolerable latency, should be assessed to reflect the potential hazard that can come from loss of UA control. For example, UA operations over desolate area pose less hazard to people than operations over densely populated area and performance need for the former would be less than the latter.
Jung, Jaewoo↗
Understanding Risk in Urban Air Mobility: Moving Towards Safe Operating Standards
Urban Air Mobility (UAM), i.e. on-demand urban passenger (and cargo) transportation services, represents a new technology and potentially an emerging industry. It is not simply an extension of commercial aviation as we know it—it is a different domain. A first priority for UAM is that it be safe and secure (Booz, Allen, Hamilton, 2018; Crown, Consulting, Inc., 2018). A workshop held in Arlington, Virginia, brought together experts from the on-demand world (including UAM) to assess and prioritize the challenges and barriers to be addressed in successfully introducing On Demand Mobility (ODM) vehicles and services (ODM and Emerging Technology Workshop, 2016). Of the nine challenges assessed, the highest priority was assigned to certification, followed by affordability, and then safety. Considering the confluence of certification and safety, it is clear that risk and its assessment were judged to be of high relevance to workshop participants.
UAM↗
Flight Demonstration of Unmanned Aircraft System (UAS) Traffic Management (UTM) at Technical Capability Level 4
The NASA Unmanned Aircraft Systems (UAS) Traffic Management (UTM) Project executed the fourth and final UTM Technical Capability Level demonstration between May and August 2019. Two Federal Aviation Administration (FAA)-designated UAS test sites managed the range, partners, and operations to meet the requirements set forth by the UTM Project. All stakeholders supported the execution of the flight testing through close collaboration. Results of the demonstration indicate the viability of the UTM concept to manage large scale operations and contingencies in an urban environment. The demonstration also provided insight into key technological gaps that must be addressed before such operations are routine, safe, and efficient. Standardization efforts related to UTM and the industry participants of those efforts can leverage the results and experiences of this flight activity to accelerate and more firmly ground forthcoming standards. The FAA and other regulators will be able to leverage results to inform future rule-making and identify additional gaps that require further analysis.
Unmanned Aircraft System Traffic Management↗
Automated Management of Small Unmanned Aircraft System Communications and Navigation Contingency
The number of small Unmanned Aircraft System (sUAS) operating in the low-altitude of the National Airspace System (NAS) has been rapidly increasing in the past few years and this number is expected to grow in the future. However, aside from a few special cases, all sUAS must fly within visual line-of-sight (VLOS) of their operators and this limitation is blocking highly anticipated beyond visual line-of-sight (BVLOS) sUAS applications such as package delivery from practice. To enable routine low-altitude BVLOS operations, there needs to be a traffic management ecosystem that complements the FAA’s Air Traffic Management (ATM) system, which does not provide air traffic services under 400 feet above ground level (AGL). NASA has been pioneering research and development of this ecosystem under UAS Traffic Management (UTM) project since 2015 in a series of Technical Capability Levels (TCL) activities that are increasingly complex. In TCL1, completed in 2015, visual line-of-sight operations such as agriculture, firefighting, and infrastructure monitoring were addressed with a focus on geofencing and operations scheduling. Technologies and requirements needed for BVLOS operations in sparsely populated areas were examined in TCL2 in 2016, and those for operations over moderately populated areas in TCL3 in 2017 and 2018. TCL4 is building on the earlier TCLs and focuses on technologies and requirements for operations in higher-density urban areas for tasks such as newsgathering and package delivery and for managing large-scale contingencies. To coordinate and facilitate the incremental implementation of the UTM ecosystem in the NAS, a Research Transition Team (RTT) has been formed between the FAA, NASA, and industry. The RTT is divided into four subgroups, concept and use case development, data exchange and information architecture, sense and avoid, and communications and navigation (C&N). This paper focuses on C&N subgroup activities, in particular about the development of automated sUAS communications and navigation contingency management. The goal of this development is to prepare sUAS to display predictable behavior while handling C&N off-nominal events. It is expected that the adoption of the presented automated contingency management by the sUAS community will accommodate and inform rulemaking towards governing low-altitude BVLOS operations.
Unmanned Aviation System (UAS) Traffic Management↗
Automated Management of Small Unmanned Aircraft System (UAS) Communications and Navigation Contingency
The number of small Unmanned Aircraft System (sUAS) operating in the low-altitude of the National Airspace System (NAS) has been rapidly increasing in the past few years and this number is expected to grow in the future. However, aside from a few special cases, all sUAS must fly within visual line-of-sight (VLOS) of their operators and this limitation is blocking highly anticipated beyond visual line-of-sight (BVLOS) sUAS applications such as package delivery from practice. To enable routine low-altitude BVLOS operations, there needs to be a traffic management ecosystem that complements the FAA’s Air Traffic Management (ATM) system, which does not provide air traffic services under 400 feet above ground level (AGL). NASA has been pioneering research and development of this ecosystem under UAS Traffic Management (UTM) project since 2015 in a series of Technical Capability Levels (TCL) activities that are increasingly complex. In TCL1, completed in 2015, visual line-of-sight operations such as agriculture, firefighting, and infrastructure monitoring were addressed with a focus on geofencing and operations scheduling. Technologies and requirements needed for BVLOS operations in sparsely populated areas were examined in TCL2 in 2016, and those for operations over moderately populated areas in TCL3 in 2017 and 2018. TCL4 is building on the earlier TCLs and focuses on technologies and requirements for operations in higher-density urban areas for tasks such as newsgathering and package delivery and for managing large-scale contingencies. To coordinate and facilitate the incremental implementation of the UTM ecosystem in the NAS, a Research Transition Team (RTT) has been formed between the FAA, NASA, and industry. The RTT is divided into four subgroups, concept and use case development, data exchange and information architecture, sense and avoid, and communications and navigation (C&N). This paper focuses on C&N subgroup activities, in particular about the development of automated sUAS communications and navigation contingency management. The goal of this development is to prepare sUAS to display predictable behavior while handling C&N off-nominal events. It is expected that the adoption of the presented automated contingency management by the sUAS community will accommodate and inform rulemaking towards governing low-altitude BVLOS operations.
Unmanned Aviation Systems (UAS) Traffic Management↗
Revolutionary Vertical Lift Technology (RVLT) Side-By-Side Hybrid Concept Vehicle Powertrain Dynamic Model
The Side-by-Side (SBS) Hybrid is one of several Revolutionary Vertical Lift Technology (RVLT) concept aircraft identified by NASA to investigate Urban Air Mobility (UAM) requirements. This paper presents a dynamic model of the SBS Hybrid powertrain built using the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) and the Electrical Modeling and Thermal Analysis Toolbox (EMTAT). The model consists of the rotors, electrical power system, and turboshaft engines connected through freewheeling clutches, gearboxes, and multiple shafts. This research effort models the complex behavior of the powertrain, including the operation of the freewheeling clutches and electrical power system at the simulation time scale of the shaft dynamics. Several simulations highlight the key features present in the model and demonstrate its operation.
Powertrain↗
Revolutionary Vertical Lift Technology (RVLT) Side-By-Side Hybrid Concept Vehicle Powertrain Dynamic Model
The Side-by-Side (SBS) Hybrid is one of several Revolutionary Vertical Lift Technology (RVLT) concept aircraft identified by NASA to investigate Urban Air Mobility (UAM) requirements. This paper presents a dynamic model of the SBS Hybrid powertrain built using the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) and the Electrical Modeling and Thermal Analysis Toolbox (EMTAT). The model consists of the rotors, electrical power system, and turboshaft engines connected through freewheeling clutches, gearboxes, and multiple shafts. This research effort models the complex behavior of the powertrain, including the operation of the freewheeling clutches and electrical power system at the simulation time scale of the shaft dynamics. Several simulations highlight the key features present in the model and demonstrate its operation.
powertrain↗
Airfoil Table Generation and Validation for the VR-12 and SSC-A09 Airfoils and Quadrotor Performance Prediction
As part of NASA’s Urban Air Mobility (UAM) mission, the Revolutionary Vertical Lift Technology (RVLT) project is creating rotorcraft reference designs that can be used by the rotorcraft community to develop quiet, efficient, and safer air vehicles. At NASA, this effort is made possible by the use of the RVLT toolchain software. Airfoil tables are often a critical part of the conceptual design process as they inform both comprehensive analysis and Computational Fluid Dynamics (CFD) codes of 2D aerodynamic coefficients, such as lift, drag, and moment coefficients. These airfoil tables, typically generated during experimental testing, are often proprietary and thus not widely distributable; further, there is not always clear or available reference documentation that provides information on the test conditions. The airfoil tables from these experiments are referred to in this work as Legacy airfoil tables. The scope of this study is to generate airfoil tables with the NASA OVERset grid CFD FLOW solver (OVERFLOW) coupled with the AirFoil Table Generator (AFTGen) software and validate these airfoil tables based on performance predictions calculated in Comprehensive Hierarchical Aeromechanics Rotorcraft Model (CHARM). The overall goal is to provide CFD generated airfoil tables, validate them through comprehensive analysis, and publish the airfoil tables for public distribution. The RVLT quadrotor reference model was selected as the basis for all analyses. The quadrotor uses the VR-12 and SSC-A09 airfoils for its rotor blades. Simulations were run in OVERFLOW for the VR-12 and SSC-A09 airfoils for ±20° angles of attack, Mach numbers from 0.3 to 1.0, and a Reynolds-Mach proportionality constant of 1.023x107. The C81 format airfoil tables from AFTGen were then blended with Legacy NACA 0012 airfoil table data for ±20° to ±180° angle of attack range. CHARM was used to compute thrust coefficient, power coefficient, and figure of merit for an isolated rotor in hover using proprietary legacy airfoil tables for the VR-12 and SSC-A09, as well as with the OVERFLOW generated airfoil tables for the VR-12 and SSC-A09. Overall, the OVERFLOW and Legacy performance predictions agreed well, with the best correlation between simulated and Legacy data observed with the VR-12 airfoil tables.
Airfoil↗
A Systems Approach to AI Model Integration and Performance Evaluation for the Generic UAM Simulation Framework
This paper introduces py-guam, an open-source experimentation framework developed for the NASA Generic Urban Air Mobility simulation (GUAM) environment, facilitating the integration and evaluation of advanced artificial intelligence (AI) algorithms. We present a systems approach which enables the seamless incorporation of data-driven models, including off-nominal and failure state detection, into the GUAM’s Cognitive Architecture (CA). The framework supports customizable experimentation parameters, derives Safety Performance Indicators (SPIs) from UL 4600 safety case analyses, and employs rapid UAM simulations to assess AI impacts on flight performance across diverse scenarios. Through comprehensive testing and validation experiments, we demonstrate GUAM’s capability to enhance safety and efficiency in urban air mobility operations. Additionally, the open-source nature of py-guam fosters community collaboration, ensuring continuous improvement and adaptability to evolving technological advancements. This work establishes a robust tool for developing and testing AI-driven urban air mobility (UAM) systems, advancing the safety and reliability of autonomous urban air vehicles.
Artificial Intelligence↗
NASA Centennial Challenges Deep Space Food Challenge Competition to Incentivize Innovation in Food Systems for Long-Duration Space Exploration Missions
The Centennial Challenges (CC) program, currently part of NASA’s Space Technology Mission Directorate (STMD), is one of the vehicles NASA uses to develop and execute public prize competitions. Since opening its first challenge in 2005, the CC program has initiated more than 20 challenges in a variety of technology areas. This paper provides the background, development and execution of the Deep Space Food Challenge as one approach to fulfilling NASA’s Space Policy Directive 1 (“To the Moon, then Mars”). Specifics about the CC program’s accomplishments will also be discussed. The Deep Space Food Challenge (DSF) was developed in collaboration with the Canadian Space Agency (CSA) to create novel food production technologies with minimal inputs, and maximum safe, nutritious, palatable food outputs for long-duration space missions, which have potential to benefit people on Earth. When humans return to the lunar surface in the mid-2020s, the early missions will use prepackaged foods similar to those in use on the International Space Station (ISS) today. However, extending the duration of lunar missions requires reducing resupply dependency on Earth. Testing a sustainable system on the Moon that meets lunar crews’ needs is a fundamental step for lunar sustainability and future Mars exploration. NASA and CSA are focused on how to furnish crew members with a viable food system for long duration space missions that provides all daily nutritional needs through a variety of palatable, safe food with limited resource requirements and no dependency on resupply from Earth; and enables acceptable, safe and quick preparation methods. On Earth, technology solutions for food systems could also be used to produce nutritional sources for urban and rural environments; potentially leading to a reduced impact on our Earth’s resources. Challenges, such as the DSF, are an embodiment of NASA’s continuing commitment to technological advancement and innovation through non-traditional programs.
Centennial Challenges↗