by Chi-an Chang
CHICAGO, Aug. 10 (Xinhua) -- Imagine flying across the U.S. in an aircraft that is partly powered by electricity, weighs lighter, flies quieter and releases less green house gas emissions than any commercial airplanes ever made. Well, that could soon come true in 2030.
Boeing Co., the Chicago-based aerospace giant, is working on a concept plane called the SUGAR Volt as part of NASA's N+3 program, which aims to explore what aircraft three generations beyond current ones may look like. SUGAR stands for Subsonic Ultra-Green Aircraft Research.
The SUGAR Volt, similar in appearance as a 737, is a twin- engine aircraft with hybrid propulsion technology that has the potential to change the aviation industry by reducing green house gas emissions and lowering fuel usage. The concept plane reduces fuel burn by more than 70 percent and total energy use by 55 percent when battery energy included. It can also cruise on battery or biofuel power when flying.
Like a 7373, the SUGAR Volt can carry 154 passengers and fly a maximum of 3500 miles. But the aircraft's designers say they would prefer the aircraft fly an average of 900 miles per trip.
"If you are going the long range, you are using mostly jet fuel to do it. But when you are flying a shorter range, you are using mostly battery," said Dr. Marty Bradley, Boeing Research and Technology principal investigator, SUGAR, with an exclusive interview with Xinhua. "I think whenever you can, you are going to fly as much on electric power as you can."
The SUGAR Volt could weigh 5,000 lbs less at take off compared with current planes that weigh 185,000 lbs. Today's conventional aircraft such as a 737 flies at 78 percent the speed of sound. The SUGAR Volt flies at about 77 percent speed. While the hybrid plane may fly slightly slower than current aircraft, Bradley says improving air traffic control system could erase the difference.
"With the Next Gen Air Traffic Control System, which allows airplanes to fly more direct routes, you can do continuous climb and descend," said Bradley. "By improving air traffic control system can more than make up for that small reduction in cruising speed."
What's more, depending on fuel prices, airline companies may just want to fly slower.
"If price of fuel continues to go up, then there's an incentive to slow down to save fuel, there's a cost effect in there, so you might choose to go slower to save money on a flight," he added.
As part of NASA's N+3 project, the Boeing team was challenged with conceptualizing a plane that would have a 71-decible reduction below current Federal Aviation Administration noise standards.
"We didn't achieve the NASA noise [reduction] goals so we need to continue working on that with the engine companies and with the configuration in order to meet that," Bradley said.
The Boeing team is looking at placing sound absorbing materials in the engine or using active noise suppression, such as blowing jets to cancel out the noise, to reduce the SUGAR Volt's noise level.
"Everything we are looking at [achieving] will be a lot quieter than the current airplanes we have today," he said.
There is one element, however, that is holding the concept plane back from becoming reality -- battery power.
The team worked the battery-power problem in reverse, asking how good do batteries have to be to make a hybrid plane that is competitive with a airplane that is completely powered by fuel.
"We determined that we needed 750 watt-hour per kilogram to make this system competitive with a jet fuel powered only airplane, " Bradley said. "That's about four times the most advanced battery we have today, or it could be about 15 times the performance you get out of some of the electric cars now."
Bradley said it's a very advance battery goal that his team is setting for the battery industry. University and industry researchers are all working to find solutions. Some battery technology include lithium-ion, lithium-air, which has the potential of increasing the energy density by as much as five to ten times compared to lithium ion batteries, and super capacitor, which could charge in seconds.
There are two approaches that the Boeing team is looking at: battery technology that can charge quickly and modular batteries that can be charged overnight.
"The advantage of [modular batteries] is that electric utilities charge lower rates for charging overnight and they have greater capacity in the electrical grid. [The utilities companies] may also want us to charge overnight rather than quickly charge in the day when they have peak demand," he explained.
Since aircraft typically have to be in and out of gates in under an hour, Bradley said modular batteries, which can be quickly replaced with charged up batteries, are more likely to happen first.
The SUGAR Volt, though conceptualized as a hybrid system, is not like the Prius or Chevvy Volt, "our concept does not charge while in flight," said Bradley.
Charging battery in flight could be something the Boeing team will look at if it receives a contract from NASA to design planes that are four generations ahead of current aircraft.
Titled N+4, the team hopes to perform more design and analysis of hybrid gas electric turbine propulsion architectures, the aerodynamics of strut/truss-braced wings, noise reduction technologies and the benefits of methane or hydrogen fuel.
The team has already submitted its proposal to NASA and will find out at the end of the year if they receive a research contract. When asked about the team's potential to receive the contract, Bradley laughed and replied, "I think we have a very good chance."