MX-1554 designs from the Los Angeles Basin, part 1: the Lockheed L-205

In June 1950, the US Air Force initiated the MX-1554 requirement (aka 1954 Interceptor) for a long-range supersonic interceptor to defend the US from the Soviet Union's recently deployed Tupolev Tu-4 strategic bomber (a reverse-engineered copy of the B-29) and still-in-the works gas turbine-powered Tu-16, Tu-95, and M-4. One of the winning designs for the MX-1554 contest, the F-102 Delta Dagger built in San Diego, has been extensively covered in numerous publications, and some people, myself included, know that the unbuilt Republic XF-103 design powered by both a turbojet and a ramjet was also a winning entrant in the MX-1554 competition, although it never reached the hardware phase. However, what has been heavily overlooked is that Lockheed entered its own design into the MX-1554 competition and was awarded a development contract, only for it to be subsequently canceled before that design could be given a military designation, and equally forgotten are designs by North American and Northrop for the MX-1554 requirement. Therefore, this and the next post will cover designs by Lockheed, North American, and Northrop devised for MX-1554.

A desktop model of the Lockheed L-205 (Model 99) interceptor. The similarity of the dorsal air intake to that of the F-107 is apparent.

As early as 1949, Lockheed had been working on design studies for a lightweight jet interceptor, known by the company designation L-190, which covered proposals with straight, delta, and variable-geometry wings. None of the L-190 studies never materialized, but after the Request for Proposals (RFP) for the MX-1554 competition was released in June 1950, Lockheed immediately returned to the concept of a purpose-built interceptor when it conceived a design for an all-weather interceptor, designated L-205 by the company, by the beginning of January 1951. The overall L-205 design submission had straight wings with tapered leading and trailing edges like those on the F-104 Starfighter but nevertheless retained the tail empennage of the XF-90 prototype penetration fighter. It measured 63 feet 9 in (19.4 meters) long with a wingspan of 30 feet 4 in (9.2 meters), a wing area of 300 ft² (27.9 m²), and a gross weight of 32,125 lb (14,572 kg), and power was provided by one 15,000 lb (66.7 kN) thrust General Electric J53 turbojet fed by air flowing through a dorsal air intake behind the cockpit (similar to that seen on the North American F-107). Unlike those of the F-104, however, the L-205's wings were low-mounted and lacked anhedral. The L-205 would be armed with six Falcon air-to-air missiles housed in a mid-lower fuselage bay and twenty 2.75 in (7 cm) folding-fin unguided air-to-air rockets placed on the sides of the bay, and it would climb to 40,000 feet (12,192 meters) in 1.6 minutes, while the service ceiling was to be 63,000 feet (19,202 meters) and operating range would be 1,760 miles (2,834 km).

On July 2, 1951, the US Air Force declared the Convair Model 8 along with the Lockheed L-205 and Republic AP-57 (the latter one of the three Republic designs proposed for the MX-1554 requirement) the winners of the MX-1554 competition, and these designs were given the go-ahead to proceed to the full-scale mock-up phase under a Phase I development contract. After being awarded a Phase I contract, the L-205 received the Basic Model Number 99, hence it being also called Model 99. However, the US Air Force couldn't afford to fund all three interceptor designs, and the L-205/Model 99 also was heavier than the Convair design and thus would have had consequent reductions in performance, so the USAF canceled the L-205 project by late 1951, even as the Convair Model 8 and Republic AP-57 were given the designations YF-102 and XF-103 respectively.

Although the L-205 project ended up becoming a loser-turned-winning design for fiscal reasons in spite of having been selected for development along with the F-102 and XF-103, Lockheed would apply a few features of the L-205, namely the tapered straight wings, to design of its future F-104 Starfighter, the first American supersonic lightweight jet fighter to be built.

References:

Buttler, T., 2007. American Secret Projects: Fighters and Interceptors 1945 to 1978. Hinckley, UK: Midland Publishing.

Buttler, T., 2013. Early US Jet Fighters: Proposals, Projects, and Prototypes. Manchester, UK: Hikoki Publications.