Subsonic Ultra Green Aircraft Research Considers LENR and other Energy for Planes

Boeing and NASA seriously considered LENR (“cold fusion”) for planes in case the technology pans out.

Subsonic Ultra Green Aircraft Research Phase II: N+4 Advanced Concept Development (148 pages)

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.

The team generated a series of configurations with different combinations of some of these technologies. The higher heating value of LNG reduces the weight of fuel burned, but because of heavier aircraft systems, more energy is used for a given flight. LNG fueled aircraft have the potential for significant emissions advantages and LNG enhances the integration of fuel cells into the aircraft propulsion and power system.

An unducted fan increases propulsive efficiency and reduces fuel burn. Adding a fuel cell and electric motor into the propulsion system also leads to improvements in emissions and fuel burn. An aft fuselage boundary layer propulsor also resulted in a fuel burn benefit.

The list of concepts scored included:
• N+4 Reference Airplane
• Conventional fuel/hybrid electric concept
• Hydrogen fuel concept (pure H2 burner)
• Methane-natural gas concept (pure CH4 burner)
• Fuel cell concept (H2/FC Battery Hybrid)
• SUGAR High TurboProps:
o Jet A
o Pure H2 burner
o H2/FC Battery Hybrid
o Pure battery-electric
• LENR-powered via heat turbines
• Distributed Propulsion Hybrid-Electric
• Dual Fuel H2/Jet-A

After each sub-team conducted the breakout sessions and then presented the outbriefs to the whole group, the group identified some common themes amongst the sub-team observations that evolved into general observations of the entire concept scoring activity, specifically:
• Hybrid electric scored high from each team, which confirmed the selection of the
concept for the current work scope in Phase II, Task 2.2
• General concern over the definition of control volume with block energy
• LENR high payoff, but high risk
• Methane concept identified as a low risk by all groups
• Participants identified that a struggle of the scoring of the concepts really revolved around:
o Source of power
o How it is converted
o How to use that power

As a result of the group discussion, the workshop focus shifted the expected outcome to picking a concept and then subsequently identifying what power application should be used; a summary of the result and recommendations from the group is outlined below:

1) LENR – Very high payoff/very high risk. Recommend small study to set goals and watch
tech feasibility and development
2) Positive consensus on Hybrid Electric – validation of Phase I selection. Already covered in SUGAR Tasks 2.2 and 3.3 (except see energy study)
3) Energy study – Life Cycle source to use (H2 or electricity). Estimate electricity use at typical airport. Supports both electric battery charging and H2 production.
4) Hydrogen – Significant benefits and challenges
• Because H2 aircraft have been studied extensively in the past, we recommend expanding other areas of the technology space
• H2 infrastructure and some technologies should be worked outside of this study
• Many H2 cryo aspects will be covered in recommended LNG/methane work below
• See also energy study above
5) Methane – Low cost and possible early deployment of cryo techs
• Methane GT SOFC driving a generator with variable speed pitch low noise props … or
… Methane GT SOFC Hybrid with low noise turboprop
• Methane as first step on a roadmap for a cryo fuel / superconducting
• GE to check on providing Methane GT and Methane GT SOFC cycle for N+4 task
6) Combined Approach to N+4 technology/config assessment:
• Adv. Tech Configuration with integrated synergistic technologies
• Aft fuselage BLI integration – synergy with methane GT SOFC to drive aft electric
fan (Goldschmied-like device)
• Technologies that are evaluated separately and could be combined into the Adv.
Tech Configuration (or others)
• Low noise props – investigate variable RPM and shape memory alloys, plasma

As a result of the workshop recommendations, a number of side studies were identified to help the group conclude on a possible N+4 concept to pass to the higher fidelity analysis. The group called these inspiration ideas that composed a wish list of research that could possibly be conducted within the scope of the current SOW:
• Study to set goals
• Watch tech feasibility and development
• Investigate system architecture options
• Develop baseline system design and system performance targets
2) Hybrid Electric
• Life cycle energy study
• Follow and encourage battery tech and system community
• Multiple parallel battery technology developments
3) Methane – Low cost and possible early deployment of cryo techs
• Gas turbine design issues
• Aircraft system issues & techs
• Infrastructure issues & techs
• Synergistic technologies
• Methane GT SOFC driving a generator
• Methane GT SOFC Hybrid
• Cryo fuel / superconducting
4) Hydrogen
• Leverage multiple previous studies
• Life cycle energy study
• Build on methane work (GT, system, infrastructure, cryo, FC’s)
• Gas turbine design issues & techs
• Aircraft system issues & techs
• Infrastructure issues & techs
• Synergistic technologies
• GT FC Hybrid
• Cryo fuel / superconducting
5) Other Techs
• BLI integration
• Current BLI investigation/validation
• Aft fuselage BLI – Goldschmied-like device
• CFD, wind tunnel, and flight validation
• Low noise high cruise speed (Mach 0.65-0.7) props
• Leverage existing design tools
• Investigate variable RPM, shape memory alloys, plasma actuator technologies,
techs from rotorcraft

LENR Requirements Analysis
The idea of using a Low Energy Nuclear Reactor (LENR) was discussed at the N+4 Workshop, both as a ground-based source of energy to create electricity or hydrogen, and an aircraft carried power source for primary propulsion. Given the potential of clean zero-emissions energy, further work was identified for both applications. Nuclear energy is a potential source of clean low cost energy that should be considered in a detailed energy study (see Section 4.0). In this section we will discuss the potential and requirements for a flying LENR application for aviation.

Since a LENR is essentially a source of heat, a heat engine of some kind is needed to produce useful work that can create an integrated propulsion system for an aircraft. It was decided to do a relatively simple study to determine the range of LENR and heat engine performance that would produce an aircraft competitive to a conventional fueled aircraft.

Some potential heat engine cycles with representative engine power to weight ratios are shown in Figure 3.1. Heat engine power to weight is a strong function of delta temperature from the LENR. Achievable LENR delta temperature is not known at this time and is beyond the scope of this current investigation. Nevertheless, we decided to parametrically vary the LENR and heat engine power per weight and apply a top level operating cost model. Even though we do not know the specific cost of the LENR itself, we assumed a cost of jet fuel at $4/gallon and weight based aircraft cost. We were able to calculate cost per mile for the LENR equipped aircraft compared to a conventional aircraft (Figure 3.2). Looking at the plots, one could select a point where the projected cost per mile is 33% less than a conventionally powered aircraft (Heat engine more than 1 HP/lb ad LENR more than 3.5 HP/lb). Since the power requirements are significantly different at cruise compared to takeoff and climb, we also investigated a hybrid case where batteries and an electric motor are used to supplement the heat engine + LENR at takeoff. This yielded significantly improved results (Figure 3.3) which required lower LENR and heat engine performance levels (Heat engine more than 0.4 HP/lb, LENR more than 1 HP/lb, and Batteries more than 225 Wh/kg).

These numbers are illustrative only, as other combinations could yield useful propulsion and power systems, and the results are dependent on cost and performance assumptions. However, the numbers should be useful in establishing initial system goals for LENR concepts.

Low Energy Nuclear Reactor Technologies

Goals and Objectives:
Develop technologies for Low Energy Nuclear Reaction (LENR) propulsion systems.

Performance Area and Impact:
Traditional fuel burn and emissions will be reduced or eliminated by using LENR energy.
Noise may be reduced by using LENR heat instead of combustion in the engines.

Technical Description:
LENR energy has the potential to eliminate traditional fuel burn and associated emissions. In the current concept, a LENR reactor generates heat that is distributed to heat engines that use the LENR heat instead of combustion. This concept is dependent on successful development of LENR technology, which has reportedly had some success in generating heat in a catalytic process that combines nickel (Ni) with hydrogen (H) gas(8). This process is reported to produce safe byproducts, such as copper, with no radioactive materials used and no long-lasting radioactive byproducts generated. Upon further investigation, it is thought that low level radiation may be generated during active energy cycles, but that it could be easily shielded and would stop quickly after reactor shutdown. Further development of LENR would be required to produce heat at a high enough temperature to support heat engines in a flight-weight installation. LENR physics analysis and evidence of high temperature pitting in LENR metal substrates indicate that temperatures appropriate for heat engines may have been achieved. It is thought that LENR would use very small amounts of fuel.

Initial LENR testing and theory have suggested that any radiation or radio-isotopes produced in the LENR reactions are very short lived and can be easily shielded. In addition, some prototypes(9) that may be harnessing the LENR process can be controlled safely within designed operating parameters and the reaction can be shut down in acceptable time frames. This heat generating process should reduce radiological, shielding and hazardous materials barriers to entry of aviation LENR systems.

Should LENR development prove successful, a few technology components will need to be
developed for LENR-based aircraft propulsion. Heat engines, which run a thermodynamic cycle by adding heat via heat transfer instead of combustion, need to be developed. A system for distributing heat from the LENR core to the heat engines also needs to be developed. Additional systems may need to be developed for supporting the LENR core, including systems to deliver reactants and remove byproducts. The Ni-H LENR system would use pure hydrogen and a proprietary nickel and catalyst substrate. Hydrogen usage would be small compared to systems that combust hydrogen. Initially, hydrogen storage might involve cryogenics. The cold liquid hydrogen (LH2) fluid might be used in a regenerative system whereby cooling is supplied to super-conducting generators, electric feeders, and motors while the gas would be used as a fuel in the LENR reactor. The primary LENR byproducts that would require periodic removal from
the aircraft are the catalyst and nickel that are contained within the reactor core. Through thoughtful design of the reactor core, preliminary information suggests that these can be easily removed and replaced. The reactor core might then be recycled at low cost, due to the absence of toxic products in the core.

Technology Status:
Multiple coherent theories that explain LENR exist which use the standard Quantum
Electrodynamics & Quantum Chromodynamics model. The Widom-Larson(10) theory appears to
have the best current understanding, but it is far from being fully validated and applied to current prototype testing. Limited testing is ongoing by NASA and private contractors of nickelhydrogen LENR systems. Two commercial companies (Leonardo Corp. and Defkalion) are reported to be offering commercial LENR systems. Those systems are advertised to run for 6 months with a single fueling cycle. Although data exists on all of these systems, the current data in each case is lacking in either definition or 3rd party verification. Thus, the current TRL assessment is low.

In this study the SUGAR Team has assumed, for the purposes of technology planning and
establishing system requirements that the LENR technology will work. We have not conducted an independent technology feasibility assessment. The technology plan contained in this section merely identifies the steps that would need to take place to develop a propulsion system for aviation that utilizes LENR technology

LENR technology is potentially game-changing to not just aviation, but the worldwide energy mix as well. This technology should be followed to determine feasibility and potential performance.

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