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Zero-Emissions Technologies for Aircraft


Scope Title:

Energy Conversion for Aircraft, Cryogenic Fuel Management, and Thermal Management

Scope Description:

NASA innovates for the benefit of humanity, and any new aircraft and technologies developed through this subtopic will help the United States achieve net-zero carbon emissions from aviation by 2050—one of the environmental goals articulated in the White House’s U.S. Aviation Climate Action Plan. 

NASA Aeronautics has always been about improving aviation efficiency and safety, while reducing noise, fuel use, and harmful emissions. For decades, our NASA-developed technologies have contributed to making aviation more sustainable—environmentally and economically. Now we are expanding research for sustainable aviation by developing and testing new green technologies for next-generation aircraft, new automation tools for greener and safer airspace operations, and new sustainable energy options for aircraft propulsion.

We're partnering with industry, academia, and other agencies through the Sustainable Flight National Partnership to accomplish the global aviation community's aggressive goal of net-zero carbon emissions by 2050.

During the next 10 years, we will demonstrate first-ever high-power hybrid-electric propulsion on a large transport aircraft, ultra-high efficiency long and slender aircraft wings, new large-scale manufacturing techniques of composite materials, and advanced engine technologies based on breakthrough NASA innovation.

In partnership with the Federal Aviation Administration (FAA) and airlines, we’ll also pioneer new air traffic management automation tools that safely and reliably put future aircraft on flight paths optimized for minimal environmental impact.

This subtopic targets aggressive innovations to reach zero emissions by providing research seed funds for small U.S. businesses. The technologies proposed should have both a technical and business pathway to introduction into the air fleet. They should have a path to application on transport aircraft that fall under FAA part 23 (<19 passenger) or FAA part 25 (>19 passenger) regulations.  

Many radical aircraft configurations are being explored to get to zero-emission aviation. Many of the concepts require a step-change in technology as well as businesses that can supply this technology in an innovative and cost-effective way. When considering the requirements of the aircraft, it is useful to reference either an existing aircraft or an aircraft concept that has been published in open literature. An example concept is the Subsonic Single Aft Engine (SUSAN) transport aircraft concept described in the reference section; however, there are many other concepts that could be considered.

Demonstrations conducted under the proposed SBIR subtopic can be conducted using unpiloted subscale aircraft. NASA is currently designing an unpiloted, 25%-scale version of the SUSAN transport aircraft concept. Reference information for the 25% SUSAN flight research vehicle includes a wing span of 30 ft, a maximum takeoff weight between 1,500 and 2,000 lb, a maximum altitude of 15,000 ft, a maximum speed of 150 mph, a 500-lb-thrust-class engine (however, used to primarily power 150-kW generator), power at 150 kW total, individual converters at 40 kW, 10 kW operating on 300-VDC bus, and thermal management from pumped liquid cooling loops with a worst-case hot temperature of 60 °C.

This SBIR subtopic is open to any ideas that lead to zero emission or highly reduced emission aircraft. We are open to ideas that utilize sustainable aviation fuels, jet A, aviation gas, or batteries with greatly improved emissions as they may have a more near-term market and path to introduction. We are also open to ideas using fuels like liquid natural gas, hydrogen, or other green fuel ideas that may require more significant infrastructure changes. 

Some specific areas we are focused on this year are:

  1. Turbofan technologies demonstrated on a small turbofan engine in the 500-lb thrust class. Preferred are implementations that have a significant fraction (>65%) of power electrically and the remainder as thrust, with at least 150 kW of power production and 150 lb of thrust. Emphasis is on producing a full prototype turbine that is light and efficient enough to have a net benefit on aircraft fuel burn and emissions. Suggested technologies are:
    1. Combined cycles (topping, bottoming, other).
    2. Integration concepts of combustor and turbine for improved overall and component performance.
    3. Turbines that utilize highly advanced combustors like rotating detonation combustions (RDCs) or alternative fuels that are not already widely considered. RDCs that have the ability to be short, pressure gain devices and to burn H2 with low NOx.
    4. Solid oxide/turbine fuel cell combinations.
    5. Heat exchangers with waste heat recovery performance that results in aircraft-level benefits. 
  2. Technologies to make cryogenic fuels like liquid natural gas and liquid hydrogen practical on an aircraft.
    1. Tank technologies that address weight, boiloff, aircraft loads, safety requirements, and transport and refueling requirements at airports.
    2. Cryogenic pump technologies that address the requirements for cryogenic fuel distribution on aircraft and loading/unloading of cryogenic fuels into tanks.
    3. On-ground airport cryogenic management technologies. 
  3. Thermal management for turbofan and electrical systems on large hybrid aircraft in the 1- to 20-MW power range. These technologies must be shown to be compatible with typical transport aircraft requirements like external environments between -60 and +60 °C, g loads between +4g and -2g, varying aircraft orientation, and other typical operational constraints. Proposed thermal management technologies must be shown to have an aircraft-level energy use and emissions benefit.
    1. Single-phase, two-phase, acoustic or other technologies to move heat from the heat source to the heat exchanger on the plane.
    2. Heat pump systems to reject heat from the plane at a lower energy.
    3. Liquid-to-air heat exchangers that take heat from the plane and transfer it to the surrounding airflow either through integration with the engine, electric engine, through the outer mold line of the aircraft, or through additional heat exchanger ducts.
    4. Thermal capacitance systems that allow the peak thermal loads to be balanced across the aircraft mission, while being light enough to result in a fuel burn benefit.
    5. Integrated thermal systems across the entire aircraft/engine platform.

Expected TRL or TRL Range at completion of the Project: 2 to 4

Primary Technology Taxonomy:

  • Level 1 01 Propulsion Systems
  • Level 2 01.3 Aero Propulsion

Desired Deliverables of Phase I and Phase II:

  • Research
  • Analysis
  • Prototype
  • Hardware
  • Software

Desired Deliverables Description:

Phase I work should include: (1) details how the specific technology and configuration of the technology in an aircraft concept leads to a benefit; (2) the plan to introduce the technology into a near-term market; (3) clear trade studies and analytical results to justify a Phase II investment;  and (4) if possible, prototype hardware component or key parts for high-risk areas or areas of performance risk.

Phase II work should include: (1) final designs and supporting analysis, (2) analysis showing technology benefit to aircraft energy use or emissions, (3) technology to market plan and/or plan for Phase IIe or Phase III SBIR support, (4) hardware demonstrations of technology, (5) written test reports showing performance of hardware, and (6) comparison of analytical estimated performance and actual measured performance of technology or components.

State of the Art and Critical Gaps:

Power extraction from both shafts of a turbofan is still at low TRL and has not been demonstrated for very small turbofans. Most RDEs are not designed in a multidisciplinary and coupled manner with the turbine, and the combined systems lack range and robustness. Combined-cycle gas turbine-fuel cells are still too heavy for flight application and the cost must come down. Cryogenic tanks and pumps need to be made more reliable, less expensive, and lighter weight. The thermal management systems need to be made efficient, reliable, and light weight. Most of these items require a system approach to optimization and a focus on longer more rugged application and ability to keep the cost down.

Relevance / Science Traceability:

Projects that could use this technology are Transformational Tools and Technologies (TTT), Advanced Air Transport Technology (AATT) Project, and Convergent Aeronautics Solutions (CAS).

Zero-emissions technology is an emerging focus of the NASA Aeronautics Research Mission Directorate (ARMD). This topic allows us to engage small business in the activity with a potential path to further funding of ideas developed under this topic through the ARMD projects mentioned above. 

Potential advocates Mark Turner (Senior Technologist, Aeropropulsion), Azlin Biaggi-Labiosa (TTT subproject manager), Amy Jankovsky (AATT subproject manager), Fayette Collier (Integrated Aviation Systems Program (IASP) Associate Director for Flight Strategy), Gaudy Bezos-Oconnor (Electrified Powertrain Flight Demonstration (EPFD) Project Manager), and Ralph Jansen.


NASA ARMD Strategic Implementation Plan:

NASA Aeronautics Research:

NASA Aeronautics Sustainable Aviation:

Electrified Aircraft Propulsion:

NASA Aims for Climate-Friendly Aviation:

Subsonic Single Aft Engine (SUSAN) Aircraft:

Subsonic Single Aft Engine (SUSAN) Transport Aircraft Concept and Trade Space Exploration:

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