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

In a report submitted to NASA in late February 2012, titled “N+4 Advanced Vehicle Concept Study,” the team described the performance of a methane-fueled aircraft concept and the development of several advanced fuel and energy technology options for 2040 to 2050.

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 report said 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.” However, the report found that “there are environmental issues with methane emissions from LNG production, as well as safety and infrastructure issues. For these reasons, we recommend further study.”

Bradley believes 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.” The biggest challenge, he said, is probably the cost to add LNG infrastructure, which hopefully will undergo “more detailed study” in the future.

Bradley stressed 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 said. “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 noted. “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.”

Source : Boeing