NASA Hybrid Electric Hyper Efficiency Aircraft Concept

Very high efficiency concept that utilizes a boundary layer ingestion propulsor on the fuselage, as well as wingtip propellers. A single speed combustion engine drives the rear fuselage fan at very high efficiency, due to the Goldschmied fuselage propulsor. The wingtip propellers are driven by batteries to provide extra thrust for takeoff and climb, and act as wingtip vortex turbines at cruise to extract energy to recharge the batteries. The combination provides a variable disc loading propulsion system that can attempt to achieve optimal cruise efficiency (~200 passenger mpg, or 50 mpg with 4 people at speeds of 125 mph).

Category:

Science & Technology

Tags:

• hybrid
• electric
• aircraft
• advanced
• concept
• NASA

[andymckee53]

Can you explain why the propulsor system is not efficient at low speeds please? Is take it there no known 'work around' to make it more efficient?

[NASAPAV]

Actually, the problem is not efficiency but simply how much thrust you can get out of the small nozzle. The BLI fuselage propulsor is optimally sized for cruise to achieve maximum efficiency, and therefore does not have nearly the thrust required for takeoff and climb. If you just try to throw more power, than the disk area is so small, that you would have to throw a LOT of power at it - and you would end up with a terrible solution.

[andymckee53]

@NASAPAV OK - understood. Can the nozzle be made to have a variable opening - such as the nozzles on fighter jets are? Also wondering if you have thought about the asymmetric problems that propellors on the extreme edge of the airframe cause if one were to fail? Have you got enough yaw control to overcome this? I don't suppose there is a possibility of locating a propellor after then end of the propulsor nozzle? I would be good to see cut away drawings that show how it all works.

[NASAPAV]

A variable diameter nozzle would still require enough power to get enough thrust and defeats the entire strategy of the concept to be efficient and low cost. I would not entertain doing wingtip propellers except for the fact that they are driven by electric motors (2 on each side with an overrun clutch). So they are as reliable as anything could be - so yes, I have thought a lot about the potential for asymmetric thrust and would never attempt this with conventional IC engines.

[NASAPAV]

Actually, I supplied all those papers to the CAFE website :)

The rear fuselage BLI propulsor is optimized for cruise flight, and has poor static and low speed thrust (insufficient for a 2000 ft field length and reasonable climb rate. The wingtip props/turbines provide supplemental thrust at takeoff and climb. I am doing detailed conceptual design on this study now, with wind tunnel testing of the BLI propulsor. I'd love to see this built - perhaps as a coop with a small company

[yrmyahdaleth]

@NASAPAV Thanks for the reply. Unfortunately I am not a member of the AIAA and cannot retrieve that paper. However I am also wondering, about the boundary layer control thruster, I have read Goldschmied's papers (thanks to CAFE), is it mostly ineffective at low speed? Or are the wingtip recovery turbines/propellers meant to act as propellers on take-off merely to further reduce take-off roll distance? Also, I have seen this concept on CAFE's and NASA's website, is it likely to be built? Thanks.

[Allexxx96Reloaded]

@NASAPAV This plane could have control of the pitch axis by shifting the center of gravity forward or backward

[EVAUnit4A]

I am not a pilot, but I can only imagine that you have to have some mad skills to take-off/land with the wings soooo low to the ground; it looks like the slightest crosswind or pilot error could roll it over easily-!

Still, cute-looking plane.

[NASAPAV]

could achieve a balanced design with high L/D, while achieving a reasonable CLmax, and CG excursion (key problems of tailless designs). SWIFT stands for Swept Wing with Inboard Flap for Trim; because the inboard flap is the pitch trim surface. Read these papers to understand further, or talk to glider pilots who have had the pleasure to fly the Swift - it is an outstanding design. So I'm leveraging this prior work to achieve high L/D in powered flight, with an ultralight, low cost structure.