From 1946 to 1963, the San Diego branch of General Dynamics' Convair division built a fair spree of short-, medium-, and long-range airliners, including the CV-240 and CV-340 feederliners as well as the 880 and 990 jet airliners. Although production of the Convair 880 and 990 ended in the early 1960s and production of future supersonic aircraft by General Dynamics would be exclusively undertaken in Fort Worth for the rest of the Cold War, GD's Convair San Diego division seized the chance in the 1960s to look at designs for commercial aircraft designed for speeds of Mach 3 or more.
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| Drawing of Convair's Mach 3 supersonic airliner proposal of 1961 from the project documents |
In 1961,Convair San Diego pitched a design study to the Federal Aviation Administration (FAA) for a supersonic airliner with a top speed of Mach 3, two years before the FAA itself initiated the National Supersonic Transport (NST) competition. This proposal, which bore no company designation, was a delta wing aircraft similar to the North American XB-70 Valkyrie in having canards near the nose, a pair of vertical stabilizers, and wingtips which could fold downwards to generate compression lift at high speed. It would have a wingspan of 114 feet 11 in (35 meters) with the wingtips in horizontal, a range of 4,028 miles (6,482 km), and a seating capacity for 130 passengers, and power was provided by four Pratt & Whitney STF 102 H turbofans situated between the vertical stabilizers in a nacelle below the wing center section. Convair anticipated a market for 150 examples of its Mach 3 SST proposal in the 1970-1975 timeframe, and the cost of each unit was estimated at $14.1 million. Convair, however, seems to have passed on an opportunity to submit its proposal for the NST competition for a Mach 3 supersonic airliner when that requirement was initiated by the FAA in 1963.
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| Top: Drawings of Convair San Diego baseline designs for turboramjet-powered hypersonic airliners. The delta wing designs were selected for technical study by Convair. Bottom: Three-view drawing of Convair San Diego baseline design for a scramjet-powered hypersonic airliner. |
In September 1965, NASA awarded GD Convair San Diego a contract to undertake design studies for a hypersonic airliner fueled by liquid hydrogen to be operational in the 1985-2000 interval. Throughout the course of late 1965, for Phase I of the study contract, Convair devised five baseline configurations for a hypersonic airliner with seating capacity for 200 passengers and a range of 5,000 miles (8,047 km). Four configurations were powered by four turboramjets and were designed to travel at Mach 6. One was a delta wing design with a conventional tail empennage that measured 345 feet (105 meters) long with a wingspan of 102 feet (31 meters) and gross takeoff weight 537,040 lb (243,597 kg), and the swing-wing design with the conventional tail empennage had the same length as the conventional delta wing baseline design but had a wingspan of 200 feet (61 meters) (120 feet [36 meters] when the wings were backswept at 70 degrees) and a takeoff weight of 602,483 lb (273,282 kg). The blended body/delta wing iteration had a double delta wing and single vertical stabilizer, and it was 300 feet (91 meters) long with a wingspan of 130 feet (39.6 meters) and a takeoff weight of 543,797 lb (246,662 kg), and the blended body/swing-wing configuration had a sharply swept delta wing planform, a single vertical stabilizer, and variable-geometry wings that were situated ahead of the wing flaps when swept and which would be unswept during low-speed flight. The scramjet-powered baseline design was powered by four scramjet engines and had a top speed of Mach 8, and while similar in overall appearance to the turboramjet-powered blended body/double delta wing baseline iteration, it differed in being 79 feet (24 meters) in height (compared to 76 feet [23 meters] for the turboramjet-powered blended body/double delta) and having a higher gross takeoff weight of 846,927 lb (384,159 kg).
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| Drawings of the final configurations of the Convair hypersonic airliner designs selected for Phase II technical studies. |
After comparing the performance advantages and drawbacks of its baseline hypersonic airliner designs, in 1966 Convair chose the turboramjet-powered conventional delta wing and blended body/double delta wing configurations for its Phase II technical studies because of their lower operating cost, sonic boom intensity, and gross takeoff weight, while the conventional swing-wing layout was retained for limited Phase II studies on abort and subsonic hold. Convair found out that turboramjet engines arranged in a podded layout had a lower engine cooling/thrust fuel flow than when housed in a buried installation, The final design of the blended body/double delta wing iteration was 317 feet (97 meters) long with a wingspan of 124 feet (37.8 meters) and it had a takeoff weight of either 636,851 lb (288,870 kg) with engines in podded layout or 512,300 lb (232,375 kg) with the engines housed in a buried installation below the rear fuselage. On the other hand, the final design of the conventional delta wing iteration was 386 feet (117 meters) long with a takeoff weight of either 1,022,621 lb (463,853 kg) with the engines podded or 750,837 lb (340,574 kg) with the engines housed in a buried configuration.
In December 1966, just months after Convair finished its design studies for a hypersonic airliner, the FAA declared the Boeing 2707 the winner of the NST competition for a Mach 3 airliner. Convair, like Lockheed, North American and McDonnell Douglas, knew firsthand that making hypersonic engine technologies mature enough for a hypersonic airliner to become feasible required engine tests, and so the Convair hypersonic airliner project was destined to never leave the design phase, like the company's Mach 3 SST proposal of 1961.
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