Northrop XP-79 Flying Ram
Begun as an extremely ambitious project for a rocket-powered gun-armed interceptor, the XP-79B emerged as a jet, intended to ram enemy bombers and survive due to its strong magnesium structure. This idea, worthy of the Nazis or the Japanese with their backs against the wall, was conceived in the US just as the tide was turning for Allied forces, and any need for such desperate measures was waning. The aircraft was not flown until the war was over, and then only once. After a near collision with a fire truck on take-off, the XP-79 flew well enough for a few minutes until it entered a spin from 8,000ft and crashed at high speed, killing test pilot Harry Crosby. Plans to continue with the rocket-powered versions of the XP-79 ended there, although Northrop's slightly less radical development vehicle, the MX-324 became the first American rocket aircraft.
The XP-79B was something of a disaster. However, it added the Northrop's experience with flying wing designs. Despite experiencing many failures, Northrop persisted with the flying-wing concept throughout the war, producing the massive XB-35 flying-wing bomber and its jet-powered derivative, the YB-49. Ultimately, Northrop's expertise in flying-wing technology would lead to the B-2 Spirit 'stealth' bomber of today, surely the ultimate vindication of Jack Northrop's dream.
Northrop XP-79 Experimental Flying Ram
In 1942, John K. Northrop proved well ahead of his fellow American
designers when he offered the USAAF a project which was revolutionary
on two counts: an all-wing aircraft powered by rocket engine which
was intended to fly at speeds approaching the speed of sound. The idea
had a certain amount of common ground with the German
Messerschmitt Me-163 Komet which was deployed against the Allies
bombers in 1944.
In January, 1943, the USAAF issued a contract for three prototypes which were given the designation XP-79, while still anxiously waiting for Northrop to ready their Rocket Wing, Model MX-324 for testing. A 2,0001b thrust Aerojet rocket engine was envisaged to power the plane, with take-off assisted by two l,000lb thrust rocket boosters. The project was eventually canceled, however, because of delays in developing the Aerojet rocket engine and a new contract was drawn up for an aircraft of much the same design but to be powered by two 1,3651b s.t. Westinghouse turbojet engines. The new prototype was designated XP-79B and called the Flying Ram, descriptive of its intended role of ramming the tails or wings of enemy bombers and slicing them off with its specially constructed wings; this was in addition to its more conventional fighter armament of four .50in machine guns in the wing leading-edge, beside the air intakes of the turbojets.
The XP-79B flying-wing was of semimonocoque structure, constructed of magnesium; the pilot had to lie prone in his unpressurized cockpit between the two turbojets, along the center of the plane. The wing design was not unlike Northrop's XP-56 (q.v.), and had air intakes at the tips for lateral control (instead of the usual rudder) and elevons and, understandably, had a reinforced wing leading-edge. Even the landing gear was unusual, with four retractable wheels. The XP-79B was transferred to Muroc Dry Lake base in June 1945 but the plane even met with problems while taxiing when tires burst on several occasions.
On September 12, 1945, however, Harry Crosby was able to give the plane its maiden flight and for 15 minutes he flew the plane over the airfield and completed several evolutions without incident but the plane suddenly went into a spin and Crosby was unable to regain control. Although he tried to jump at the last moment, he was caught in the airplane's slipstream and his parachute failed to open. The plane ended up as a flaming torch of magnesium and although the fault which cost Crosby his life could have been corrected, the USAAF decided to abandon the project.
The first reaction-powered flight of a piloted aircraft took place on June 30, 1939, when the German Heinkel He 176 rocket flew for 50 seconds. Continuing development of the powerplant led to the introduction of the rocket-propelled Messerschmitt Me 163 Komet, first flown in April 1941.
The Japanese also tested a rocketing patterned after the Komet design. In the United States, the first serious thought given to the development of a rocket-powered fighter came in late 1942 when Northrop devised a flying wing aircraft driven by a liquid-fuel rocket motor. In January 1943, three of these fighters, designated XP-79, were ordered from Northrop. Since Northrop did not have the space to assemble their new fighter, the program was subcontracted to Avion, Inc. for actual construction.
The project was handled with the greatest of secrecy; and new techniques in metal fabrication were devised, such as welding magnesium. Two months after the rocket-powered XP-79A's were ordered, it was decided to alter the third airframe to use two Westinghouse turbojets in place of the rocket motor. The jet version was designated XP- 79B. Difficulties with the Aerojet rocket motor led to the priority being placed on completion of the jet-powered XP-79B. Eventually the rocket versions were cancelled; however, a development of the program, the MX-324, was flown by rocket power on July 5, 1944.
The XP-79B was transferred to Northrop on December 1, 1944, for completion. The magnesium structure created an extremely sturdy machine, and some thought was given to using the fighter as an aerial battering ram to slice wings and tails from attacking bombers. How practical this would be remains to be seen. Other design features of interest were the prone cockpit position, enabling the pilot to withstand up to 21 g's, wingtip bellows instead of conventional rudders, and a four-point landing gear system. In June 1945, the XP-79B was delivered to the test facilities at Muroc for flight evaluation.
Taxi testing seemed to be causing the most problems, the tires constantly blowing out during high-speed dashes. Finally, on September 12, 1945, the XP-79B was taken into the air. For about 15 minutes, the fighter seemed to perform normally; then, at an altitude of some 7,000 feet, the XP-79 started into a slow roll from which it failed to recover. The pilot bailed out at 2,000 feet, but was struck by the revolving aircraft and was unable to open his parachute. The magnesium XP-79B was totally consumed by fire following its impact with the desert.
No armament had been installed, but the XP-79B was expected to carry four .50 cal. machine guns with 250 rpg. Span of this flying wing fighter was 38 feet, length was 14 feet and height was 7 feet 6 inches. The two Westinghouse J30 turbojets provided a total of 2,300 lbs. of thrust for the 9,600 pound gross fighter. Empty weight was 6,250 pounds. Since the plane was destroyed before actual performance figures could be determined, the maximum speed of 547 mph at sea level is only an estimate. Three hundred gallons of fuel could be carried.
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The Northrop MX-324 testbed for the XP-79A. |
The MX-324 testbed coming in for a successful landing. |
Specifications for the Northrop XP-79B
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Length: 14 ft Wingspan: 28 ft Height: 7 ft Wing area: 278 ft² Empty weight: 5,840 lb Loaded weight: 8,669 lb Powerplant: 2× Westinghouse 19B turbojet, 1,150 lbf each Performance Maximum speed: 547 mph Range: 993 mi Service ceiling: 40,000 ft Rate of climb: 4,000 ft/min Wing loading: 31 lb/ft² Thrust/weight: 0.27 Armament Guns: 4 × .50-cal (12.7 mm) machine guns (never fitted) |
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| A: Bellows-operated, split horizontal control surfaces were located in the outer wings. Air for the activation of the controls came via control valves in the oval-shaped wingtip ducts. | B: The intakes for the XP-79's two turbojets were situated to the sides of the glazed nose. They considerably impaired the pilot's view to left and right. | C: It was originally planned to power the XP-79 with an 1,998-lb. thrust Aerojet XCAL- 200 rocket motor, but instead two Westinghouse J30 turbojets were fitted with exhaust pipes on either side of the cockpit nacelle. |
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| A: On the XP-79 to keep frontal area to a minimum and to give the pilot greater g-tolerance, a prone piloting position was adopted. This meant that the pilot had to lie on his stomach on a specially designed 'couch'. | B: Twin vertical fins and rudders were necessary to give the XP-79 flying wing sufficient lateral stability and control when turning, and at low speed for landing. | C: A four-wheeled landing gear was fitted. The front, steerable wheels retracted Into the engine nacelles while the large main wheels retracted into the lower surface of the wing. |