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Boeing SUGAR volt Hybrid Airplane

Boeing study of future aircraft technologies expands envelope of possibilities

May 2012

Boeing Subsonic Ultra-Green Aircraft Research (SUGAR) team is identifying commercial transport concepts for NASA that may be viable between 2030 and 2050

HUNTINGTON BEACH, Calif. – Boeing is leading a SUGAR study that is adding some extra sweetener to the mix for the National Aeronautics and Space Administration.

SUGAR, which stands for Subsonic Ultra-Green Aircraft Research, is a contract that NASA has awarded Boeing to see what’s out there in regard to technologies that might be viable for subsonic commercial aircraft to meet environmental requirements in the years 2030 to 2050.

This year, the SUGAR team, which includes Boeing Research & Technology, Boeing Commercial Airplanes, General Electric and Georgia Institute of Technology’s Aerospace Systems Design Laboratory, has told NASA that the list of possibilities is longer than anticipated when the study began four years ago.

“I think we have identified that there are a lot more options than we thought when we started,” says Dr. Marty Bradley, Boeing principal investigator for the SUGAR project. “Even though we don’t know for sure which technologies will end up being used in the future, we have greater confidence that we will be able to continue to make significant improvements in each successive generation of commercial aircraft.”

A report the team submitted to NASA in late February 2012, titled “N+4 Advanced Vehicle Concept Study,” describes the team’s work in looking at the performance of a methane-fueled aircraft concept and the technology development of several advanced fuel and energy technology options for the 2040 to 2050 time-frame.

These include hybrid battery-gas turbine propulsion, fuel cells, fuel cell-gas turbine hybrid propulsion systems, cryogenic fuels (liquefied natural gas/methane and hydrogen), cryogenically cooled engines and associated technologies, advanced batteries and open rotor/turboprop technologies.

The team has found that “liquefied natural gas (LNG), though not an obvious choice for a future aviation fuel, does offer lower fuel burn and emissions as well as potential cost and availability benefits.” The report goes on to say that “cryogenic LNG also would enable fuel-cell hybrid electric propulsion and would be a step toward clean liquid hydrogen fuel. However, there are environmental issues with methane emissions from LNG production, as well as safety and infrastructure issues. For these reasons, we recommend further study.”

The report shows that it will be possible “to design a pretty nice LNG-fueled aircraft (in 2040 to 2050) and that it could have some significant advantages in reducing emissions and potentially fuel cost,” says Bradley. “The cost to add LNG infrastructure is probably the biggest challenge. We hope this will inspire others to do more detailed studies that look at cost and infrastructure impacts.”

The SUGAR team also has looked at hydrogen as a potential fuel for commercial aircraft in 2040 to 2050 and has found great potential but also significant challenges in regard to leakage, material compatibility, density, and the need to use a lot of energy to make hydrogen fuel.

“Natural gas only needs a few steps to purify and liquefy it to make LNG for aviation use, which is simpler and cheaper,” Bradley says. “So we think that liquid natural gas can be ready sooner, while hydrogen has more difficult technical, cost and environmental challenges.”

In Phase 1 of the SUGAR study, which looked at technologies for the years 2030 to 2035, the team reported that  hybrid electric engine technology was a “game-changing technology”  and a “clear winner” because it could potentially improve performance relative to all of NASA’s environmental goals to reduce fuel burn, greenhouse gases, nitrous oxide emissions, noise and field length.

That concept is still getting a close look during Phase 2 of the SUGAR study, which will continue for another two years, Bradley says. “We continue to work on the hybrid electric propulsion concept in Phase 2 and will be looking at energy cost and potential noise reduction later this year,” he says. “We have talked to a fair number of people in the battery technology community. There is a lot of uncertainty as to how good batteries will be in 2030 to 2050. But we are quite encouraged to see battery companies starting to show real products with much higher performance.”

Bradley emphasizes that the purpose of the SUGAR study is to “start the industry thinking about and planning technologies that future vehicles will need in 2030 to 2050. While Boeing is interested in developing environmentally progressive vehicles, it would be premature to conclude that any of the concepts we study under this contract will replace any of Boeing’s commercial products.”

What Boeing is providing NASA is information “on which technologies have high potential and a technology plan roadmap that tells what steps need to be taken to get the technologies ready for applications on future aircraft,” Bradley says. “And NASA has already started this technology development process.”

And, for Boeing, “we have opened up new design space by quantifying potential payoffs of new concepts and aerodynamic structures, systems, propulsion, fuel and operations technologies,” Bradley points out. “You can look at hard challenges and say, ‘If we can get this to work, there will be a significant benefit to future aircraft.’ That helps justify and sell the idea of investing now for the future potential payoff.”

For more information please see SUGAR volt