The CL-278: Lockheed's first high-altitude spyplane design

The Lockheed U-2 spyplane that made headlines when one was shot down over the USSR in May 1960 and also ignited the October 1962 missile crisis by photographing Soviet ballistic missile sites in Cuba is easy recognizable by sailplane-like wings married to a slender, cigar-shaped fuselage (as a matter of fact, the initial CL-282 design that gave rise to the final U-2 design was a cross between the F-104 Starfighter and a sailplane). However, the U-2 was not first subsonic spyplane design that Lockheed conceived during the Cold War. Even before Clarence "Kelly" Johnson envisaged the initial CL-282 design, his company was already tinkering with the idea of a subsonic sailplane-like reconnaissance aircraft, envisaging not one, but two designs for such an aircraft with an airframe different from that of the CL-282.

A three-view drawing of the CL-278-1-1 (aka L-278-1-1) and a close-up of the aircraft's nose section for the spy cameras from project documents.   

In early 1954, after being informed about the Air Material Command's MX-2147 program (codename Bald Eagle) for a high-altitude reconnaissance plane for the US Air Force (which was won by the Bell X-16 and Martin RB-57D), Kelly Johnson decided to initiate design studies for a subsonic high-altitude spyplane under the company label L-278 (later CL-278) without input from the Air Force. In particular, he railed against government bureaucracy for obstructing any progress faced by his company's cutting-edge aircraft projects in reaching full-scale development, so he felt it convenient to go it alone working out the design of the CL-278 with the slightest hope that the US Air Force would approve this project for eventual prototyping. The first CL-278 design, the CL-278-1-1 (aka L-278-1-1), was very much a jet-powered sailplane like the U-2 but was far bigger than the first-generation U-2s, with a length of 76 feet (23.16 meters) and a wingspan of 98 feet 8 inches (30.07 meters) compared to the 50 foot length and 80 foot wingspan of first-generation U-2 variants, and its wing area of 650 square feet (60.38 square meters) and wing aspect ratio were bigger than that of the U-2A and U-2C. The wings would be braced with external struts on the underside to keep them structurally stable, and the pilot sat in a huge bubble-shaped cockpit canopy to aid him in navigating the CL-278-1-1 through hostile airspace. Power was provided by one General Electric J79 turbojet situated below the fuselage and extending to the base of the tail empennage, and air was fed into the J79 through two intakes on the sides of the fuselage. The CL-278-1-1 utilized a tricycle landing fear for takeoff and landing like the designs submitted for the MX-2147 competition. Four spy cameras were housed in the nose section to allow ground personnel to disconnect the nose in order to remove the cameras and install newer ones in the nose.

A three-view drawing of the CL-278-1-2 (aka L-278-1-2) tailless spyplane from the project documents

The second CL-278 concept worked out by Lockheed, the CL-278-1-2 (aka L-278-1-2), had a rather different layout than than the CL-278-1-1, taking the form of a tailless aircraft with the J79 situated inside the fuselage nacelle aft of the pilot's seat and backswept wings with rounded wingtips. As with the CL-278-1-1, the CL-278-1-2 carried its spy cameras inside the nose, which was rounded like that of the P-80/F-80 Shooting Star, and two triangular vertical stabilizers were located near the wingtips with control surfaces situated along the wing's trailing edge (similar to that proposed for the Junkers EF 128 jet fighter project of early 1945). The lack of a tail empennage as well as the slender backswept wings gave the CL-278-1-2 a length of 42 feet (12.8 meters) and wingspan of 100 feet (30.48 meters), the latter slightly shorter than that of second-generation U-2s, although the CL-278-1-2's wing area was the same at that of the CL-278-1-1. Although data for the performance and weight of the CL-278 designs is lacking in project documents for the CL-278, it is reasonable to assume that either CL-278 proposal would have flown at same altitude of the U-2, X-16, or RB-57D with a top speed comparable to or approaching that of the U-2 and RB-57D, high enough to escape interception by Soviet jet fighters and interceptors.

Although the CL-278-1-1 would have exhibited outstanding flight characteristics like the U-2 and the CL-278-1-2's tailless layout might have afforded it greatly reduced aerodynamic drag compared to the CL-278-1-1, Johnson eventually discarded the CL-278 project and instead saw the CL-282 as the most promising design for full-scale development by virtue of using the fuselage of an existing aircraft and dispensing with landing wheels to save weight when reaching its design altitude. The initial CL-282 proposal may have been frowned upon by LeMay as well as John Seaberg and William Lamar of the AMC's New Developments Office as too aerodynamically frail when submitted for consideration, but an undaunted Johnson chose to revise the CL-282 design to include the CL-278's rounded nose and incorporate low-mounted horizontal stabilizers, and with these changes, he managed to win the backing of the CIA for the CL-282, which eventually became the U-2.

References:

Rose, B., 2010. Secret Projects: Flying Wings & Tailless Aircraft. Hinckley, UK: Midland Publishing.