More of 'what might have been'

BY ERIK SIMONSEN

In our October 2004 issue, Boeing Frontiers looked at highly innovative aircraft and spacecraft designs made in response to requests for proposals or submitted as unsolicited proposals. Despite the ingenuity of these designs, the ideas never moved into production.

Here, as part of an occasional series, Boeing Frontiers takes another look at "what might have been" with ideas that were passed over.

MCDONNELL XP-67: THE BAT

In September 1939, James McDonnell established McDonnell Aircraft Corp. in St. Louis. His goal was to enter the fighter aircraft market and capture new military contracts. The following year the U.S. Army Air Corps, fostering innovation, issued a Request for Proposal for a large aircraft to carry out missions as a fighter, bomber destroyer and bomber escort. It looked as though McDonnell's first project, assisted by fewer than 20 engineers, would be unique and exciting.

McDonnell ordered maximum NACA (National Advisory Committee for Aeronautics, now NASA) wind tunnel hours on the final design. After several design iterations the Model IIa was ultimately selected. Designated XP-67 (XP for "experimental pursuit") the airplane became a reality and was quickly dubbed by workers as "the Bat."

From a head-on view, the XP-67 was similar to Kelly Johnson's SR-71 design that followed 18 years later. The fuselage and shaped engine nacelles were blended into a laminar flow wing. Manufacturing processes were considered extremely important; any advantage of the laminar flow wing would be lost if the finished surfaces were not precise and extremely smooth. McDonnell had promised a top speed of 472 mph (760 kilometers per hour) for the 20,000-pound (9,070-kilogram) airplane.

A ducted opening at the rear of the engine nacelles took advantage of exhaust gases to increase thrust. The Bat's design also featured an interchangeable capability, allowing the use of conventional engines for long-range flights and future jet engines for combat operations. Incorporating this feature early may have helped the project, since the Continental engines only developed 1,060 horsepower each, contributing to the aircraft's lack of performance.

The XP-67's first flight took place on Jan. 6, 1944, with chief test pilot E. E. "Ed" Elliot at the controls. Although initial aerodynamic problems were eventually fixed, power plant deficiencies were never solved. Further test-flight delays were caused by several bouts of engine overheating and fires.

By early 1944, the need for a new bomber escort came into question as North American P-51D Mustangs, with the addition of a unique internal fuel tank, were already providing bomber escort in the European theater.

Flight testing on the XP-67 continued. With only 40 hours on the airframe, the final blow came on Sept. 6, 1944, during a mission out of Lambert Field in St. Louis. Shortly after takeoff, the right engine caught fire. Elliot quickly returned to base and skillfully approached for a crosswind landing, keeping the flames away from the fuselage. However, as the aircraft was coming to a full stop, a brake failure caused the aircraft to turn the burning engine upwind. Elliot escaped uninjured as the No. 1 prototype was fully engulfed in flames. The program was halted, and the No. 2 prototype, only 15 percent complete, was never finished.

As the jet age loomed, the propeller-powered XP-67 could be considered a victim of bad timing-and bad luck. On the plus side, however, several flight parameters showed promise. For example, the XP-67 was to be heavily armed with six 37mm cannons. The latter would have been well-suited for Korean War night fighter missions that were flown in the early 1950s. A jet-powered XP-67 also would have addressed a primary criticism from F-86 Sabre Jet pilots during that conflict-the lack of punch delivered by the plane's six machine guns. The Sabre Jet was outgunned by the MiG-15, which was armed with one 37mm and two 23mm cannons.

McDonnell and his team had learned a lot from the XP-67 experience. And as history recorded, they quickly moved on to bigger and better things. March 7, 1945, saw an order for 100 jet-powered FD-1 Phantoms for the U.S. Navy. The seed was planted for the future, which would witness an amazing aeronautical evolution with the Phantom I, Banshee, Phantom II and the incomparable F-15 Eagle jet fighters.

MANNED ORBITING LABORATORY

In August 1965, in the midst of NASA's Gemini space activities and Apollo project, President Lyndon Johnson said the U.S. Air Force Manned Orbiting Laboratory program would proceed. This kept a promise to the Air Force, made following cancellation of the X-20 Dyna-Soar space plane program in 1963.

The decision represented a second chance for the United States to stay on course with a balanced approach to manned spaceflight: MOL would provide a backup for NASA's civilian space program and be a viable alternative to expensive unmanned spy satellites that were slow in maturing.

Under the MOL contract, McDonnell Aircraft would modify its Gemini spacecraft design, to be designated Gemini-B. Douglas Aircraft was tasked with building a 42-foot-long, 10-foot-diameter (12.8 meters long, 3 meters in diameter) cylindrical laboratory module which would be attached to the manned Gemini. As envisioned, MOL would be capable of supporting a minimum of four astronauts and their equipment and experiment-laden laboratory.

General Electric held contracts for classified MOL experiments, and Martin Marietta would be responsible for the Titan IIIC expendable rocket used to launch it.

After achieving orbit, the crew would enter the laboratory through a hatch built into the Gemini heat shield. To prove the unique hatch concept, the project's only test flight was conducted on Nov. 3, 1966. A Titan IIIC lifted an unmanned Gemini-B and a mock MOL configuration into low Earth orbit. During a commanded reentry, the searing heat permanently sealed the hatch leading to the lab.

With the new hatch deemed safe for reentry, the MOL program continued on track. By 1967, it was the Air Force's largest space program.

Meanwhile, military astronaut candidates, chosen from an elite cadre of fighter pilots, were in training for their classified space mission. When launched from Vandenberg Air Force Base, Calif., into 150-mile-high (241 kilometers) polar orbits, the MOL orbits would provide excellent coverage of the Earth below. MOL was to be equipped with the advanced 6-foot-aperture (1.8 meters) KH-10 camera, and could inspect other orbiting assets.

On June 10, 1969, without prior notice, Deputy Defense Secretary David Packard announced the cancellation of the MOL program, which affected 12,000 jobs at contractors. The White House had decided on major defense budget cuts and with the Apollo program on track for a moon landing sometime later that year, a secondary manned military space program could be sacrificed.

One strategic flaw was not noted-MOL would have operated in polar orbit for military reconnaissance purposes. NASA did not operate manned polar-orbit flights.

Had the MOL program continued successfully, much would have been gained by the U.S. military and military astronauts, perhaps accelerating the Air Force's push into space.

erik.simonsen@boeing.com