Someone is selling a McDonnell-Douglas painting (the original actual painting, it seems) of an SST concept:

The aircraft uses a “parasol” wing, which was a concept that enjoyed a bit of popularity in the 1970’s. The idea: at supersonic speeds shock waves shed from the nose of the craft would impinge on the underside of the wing, adding lift and reducing  fuel requirements. As memory serves, an added bonus would be that the benefit of area ruling would be in place, but without the need to actually “wasp-waist” the fuselage. Being able to produce a bland cylindrical fuselage would greatly reduce cost and stress on the large pressurized structure.

Such “favorable interference” designs would produced for fighters, SSTs and bombers, from USAF design labs to Boeing to McD to Lockheed and probably others. In time, the idea faded away; the gains in supercruise performance were apparently outweighed by cost and weight.

Note that the positioning of the engines, unusual for an SST, would also serve the favorable interference purpose: shock waves from the inlets would impinge on the wings above.

The Boeing 473-12, from July 1948. An early concept for a passenger jetliner, this would have been powered by two Rolls Royce “Nene” engines and could carry a crew of three and 27 passengers a range of 550 miles. This was an early step on the path to the 707, the worlds first successful jetliner.

A three-view of the early jetliner design, showing the clean lines and basic geometry that would become virtually standard for the next seventy years or more.

From an ebay auction, a 1966 Boeing cutaway drawing of the early swing-wing version of the 2707 SST. While the wing would have made low speed flight, in particular takeoffs and landings, more efficient and comfortable, the technology of the time would have made the wing pivot and associated systems simply too heavy and complex for a commercial system such as this. Thus the final 2707-300 SST did away with the variable geometry wing.

But damn if it wasn’t sexy.

Photo of display models (from this auction)