17 March 2021

Looks Like Another Take on the B-70 Valkyrie

Not particularly informative, but the patent application has a bit more information

The B-70 with the wingtips lowered to contain the sonic boom

106 is the Engine, 108 is the nacelle, and 114 is the underside of the wing

Some more detail.

I just came across this brief bit about New Century Transportation & Aeronautics Research's (NCTAR) concept for a low sonic boom SST, and it seems rather similar to the compression lift concepts developed for the B-70 supersonic bomber in the late 1950s.

It had wingtips that folded down (see picture, those wing tips are each as big as a Mirage III wing) that contained the shock waves generated off of the inlet and fuselage which increased lift.

This contained the pressure under the aircraft and increased lift and so improved its lift to drag ratio. (It also moved the center of lift forward, reducing trim drag at supersonic speeds, but that's for another post)

It appears taht NCTAR is looking to do the same thing, only with an additional goal of using shock waves and bypass air from the engine to reflect the sonic boom (shock wave) back up to the wing, and hence attenuate the, "Boom."

Basically shock-waves off the engines, which are located in front of the wing keep the boom, and its pressure  contained under the wing, increasing efficiency and reducing boom.

A part of this is that the bypass air is not, as is normally the case, ejected radially, but rather from the bottom of the nacelle, further reinforcing the "wall" that contains the shockwave.

It's a nifty concept, though I wander what the trade-offs might be:

With the resurgent interest in supersonic air travel, aircraft designers are looking at different ways to work around the problem of sonic booms. Flying supersonic only over water, or at a low enough Mach number to prevent shockwaves reaching the ground or shaping the airframe to minimize boom strength are all approaches being taken with aircraft now in development.

U.S. startup New Century Transportation & Aeronautics Research (NCTAR) has patented (U.S. patent 10,618,638) a different approach: use the engines and their exhaust plumes to reflect and attenuate the shockwaves from the wing and so reduce the sonic boom reaching the ground.

In NCTAR’s concept, the engines are located ahead of a wing that is curved so that, in cruise, the downward-propagating compression waves from the leading edges are focused onto the exhaust plumes. The shockwaves reflect off the shear layer between the freestream airflow and supersonic exhaust plume and back up onto the underside of the wing. This increases pressure under the arched wing and generates additional compression lift to improve supersonic lift-to-drag ratio.
Like I said, kind of nifty, in a B-70 bomber kind of way.

That being said, I really don't see this for commercial airliners, because even with improvements, the aircraft will be less fuel efficient than their subsonic counterparts, but given the current trajectory of our society, I could see something akin to a supersonic version of a Gulfstream private jet come from this.


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