This report summarizes the Truss Braced Wing (TBW) work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team, consisting of Boeing Research and Technology, Boeing Commercial Airplanes, General Electric, Georgia Tech, Virginia Tech, NextGen Aeronautics, and Microcraft. A multi-disciplinary optimization (MDO) environment defined the geometry that was further refined for the updated SUGAR High TBW configuration. Airfoil shapes were tested in the NASA TCT facility, and an aeroelastic model was tested in the NASA TDT facility. Flutter suppression was successfully demonstrated using control laws derived from test system ID data and analysis models. Aeroelastic impacts for the TBW design are manageable and smaller than assumed in Phase I. Flutter analysis of TBW designs need to include pre-load and large displacement non-linear effects to obtain a reasonable match to test data. With the updated performance and sizing, fuel burn and energy use is reduced by 54% compared to the SUGAR Free current technology Baseline (Goal 60%). Use of the unducted fan version of the engine reduces fuel burn and energy by 56% compared to the Baseline. Technology development roadmaps were updated, and an airport compatibility analysis established feasibility of a folding wing aircraft at existing airports.

https://ntrs.nasa.gov/api/citations/20110011321/downloads/20110011321.pdf

Subsonic Ultra Green Aircraft Research

This final report documents the work of the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team on Task 1 of the Phase II effort. The team consisted of Boeing Research and Technology, Boeing Commercial Airplanes, General Electric, and Georgia Tech. Using a quantitative workshop process, the following technologies, appropriate to aircraft operational in the N+4 2040 timeframe, were identified: Liquefied Natural Gas (LNG), Hydrogen, fuel cell hybrids, battery electric hybrids, Low Energy Nuclear (LENR), boundary layer ingestion propulsion (BLI), unducted fans and advanced propellers, and combinations. Technology development plans were developed.

/pdf/subsonic-ultra-green-aircraft-research-phase-ii-n-4-advanced-4v7xjfkme5.pdf

Subsonic Ultra Green Aircraft Research Phase II: N+4 Advanced Concept Development

The use of hybrid-electric propulsion (HEP) entails several potential benefits such as the distribution of power along the airframe, which enables synergistic configurations with improved aerodynamic and propulsive efficiency. This paper presents a comprehensive preliminary sizing method suitable for the conceptual design process of hybridelectric aircraft, taking into account the powertrain architecture and associated propulsion–airframe integration effects. To this end, the flight-performance equations are modified to account for aeropropulsive interaction. A series of component-oriented constraint diagrams are used to provide a visual representation of the design space. A HEPcompatible mission analysis and weight estimation are then carried out to compute the wing area, powerplant size, and takeoff weight. The resulting method is applicable to a wide range of electric and hybrid-electric aircraft configurations and can be used to estimate the optimal power-control profiles. For demonstration purposes, the method is applied to a regional HEP aircraft featuring leading-edge distributed propulsion (DP). Three powertrain architectures are compared, showing how the aeropropulsive effects are included in the model. Results indicate that DP significantly increases wing loading and improves the cruise lift-to-drag ratio by 6%, although the growth in aircraft weight leads to an energy consumption increase of 3% for the considered mission.

/pdf/preliminary-sizing-method-for-hybrid-electric-distributed-5306xfvago.pdf

Preliminary Sizing Method for Hybrid-Electric Distributed-Propulsion Aircraft

NASA's Environmentally Responsible Aviation (ERA) project has matured technologies to enable simultaneous reductions in fuel burn, noise, and nitrogen oxide (NOx) emissions for future subsonic commercial transport aircraft. The fuel burn reduction target was a 50% reduction in block fuel burn (relative to a 2005 best-in-class baseline aircraft), utilizing technologies with an estimated Technology Readiness Level (TRL) of 4-6 by 2020. Progress towards this fuel burn reduction target was measured through the conceptual design and analysis of advanced subsonic commercial transport concepts spanning vehicle size classes from regional jet (98 passengers) to very large twin aisle size (400 passengers). Both conventional tube-and-wing (T+W) concepts and unconventional (over-wing-nacelle (OWN), hybrid wing body (HWB), mid-fuselage nacelle (MFN)) concepts were developed. A set of propulsion and airframe technologies were defined and integrated onto these advanced concepts which were then sized to meet the baseline mission requirements. Block fuel burn performance was then estimated, resulting in reductions relative to the 2005 best-in-class baseline performance ranging from 39% to 49%. The advanced single-aisle and large twin aisle T+W concepts had reductions of 43% and 41%, respectively, relative to the 737-800 and 777-200LR aircraft. The single-aisle OWN concept and the large twin aisle class HWB concept had reductions of 45% and 47%, respectively. In addition to their estimated fuel burn reduction performance, these unconventional concepts have the potential to provide significant noise reductions due, in part, to engine shielding provided by the airframe. Finally, all of the advanced concepts also have the potential for significant NOx emissions reductions due to the use of advanced combustor technology. Noise and NOx emissions reduction estimates were also generated for these concepts as part of the ERA project.

/pdf/assessment-of-the-performance-potential-of-advanced-subsonic-1w0y75l1vc.pdf

Assessment of the Performance Potential of Advanced Subsonic Transport Concepts for NASA's Environmentally Responsible Aviation Project

This Final Report summarizes the hybrid electric concept design, analysis, technology, and modeling work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team. The time period of the work was February 2012 through June 2014. This includes work that was part of Task 2.2 (Hybrid Electric Concept Studies and Exploration) and Task 3.3 (Hybrid Electric Modeling Environment). The team consisted of Boeing Research and Technology, Boeing Commercial Airplanes, General Electric, and Georgia Tech. A variety of performance and sizing tasks were conducted including looking at hybrid electric versions of a conventional tube-and-wing aircraft and a hybrid wing body. Trends and results were similar to the high wing Truss Braced Wing (TBW) SUGAR Volt aircraft. The SUGAR Volt was updated based on results from the TBW work in Task 2.1 (documented in a separate report) and new engine performance models from team member GE. Energy cost and acoustic analyses were conducted and technology roadmaps were updated for hybrid electric and battery technology. NOx emissions were provided by GE for landing and takeoff (LTO) and cruise. Georgia Tech developed detailed NPSS models for hybrid electric components and tested the modeling environment with an integrated analysis of superconducting and nonsuperconducting hybrid electric engines. The hybrid electric SUGAR Volt was shown to produce significant additional emissions and fuel burn reductions beyond those levels achieved by the conventionally powered SUGAR High. The SUGAR Volt was able to meet the NASA goals for fuel burn. Total energy utilization was not decreased but reduced energy cost can be achieved for some cost scenarios. The team was not able to identify a technology development path to meet the noise goals established by NASA.

Subsonic Ultra Green Aircraft Research: Phase 2. Volume 2; Hybrid Electric Design Exploration

NASA has set demanding goals for technology developments to meet national needs to improve fuel efficiency concurrent with improving the environment to enable air transportation growth. A figure shows NASA's subsonic transport system metrics. The results of Boeing ERA N+2 Advanced Vehicle Concept Study show that the Blended Wing Body (BWB) vehicle, with ultra high bypass propulsion systems have the potential to meet the combined NASA ERA N+2 goals. This study had 3 main activities. 1) The development of an advanced vehicle concepts that can meet the NASA system level metrics. 2) Identification of key enabling technologies and the development of technology roadmaps and maturation plans. 3) The development of a subscale test vehicle that can demonstrate and mature the key enabling technologies needed to meet the NASA system level metrics. Technology maturation plans are presented and include key performance parameters and technical performance measures. The plans describe the risks that will be reduced with technology development and the expected progression of technical maturity.

Environmentally Responsible Aviation (ERA) Project - N+2 Advanced Vehicle Concepts Study and Conceptual Design of Subscale Test Vehicle (STV) Final Report

An advanced design study examined the capabilities of a large Blended-Wing-Body (BWB) freighter. Reductions in the cost of transporting freight were sought from cutting the time to transfer between air and ground transport modes through use of intermodal containers, capturing efficiencies of scale by configuring an aircraft to carry a maximum number of containers, and capitalizing on natural efficiencies of BWB configurations. The large size of intermodal containers, set by efficiency considerations for the truck transport mode, presented some challenges in determining the most efficient way to carry large numbers of containers in the BWB. Several BWB freighter configurations with different arrangements for carrying containers were analyzed and optimized with the Wing Multidisciplinary Optimization Design (WingMOD) code. Airport pavement loading and 80- meter box constraints ultimately limited the size of the BWB freighter. Measuring efficiency as the weight of freight carried divided by aircraft takeoff weight, a large, dedicated BWB freighter was shown to offer significant improvements in efficiency that could be used to develop new opportunities for the air cargo business.

Derrell L. Brown

Papers

Environmentally Responsible Aviation (ERA) Project - N+2 Advanced Vehicle Concepts Study and Conceptual Design of Subscale Test Vehicle (STV) Final Report

Design trades for a large blended-wing-body freighter