Navaho Credit - © Mark Wade

Reusable, conventional airfield takeoff-and-landing aerodynamic test vehicle for Navaho missile.

In May 1950 North American began design of an aerodynamic test vehicle for the planned intercontinental version of its Navaho Mach 3 cruise missile. This would be of the same dimensions and aerodynamic shape as the cruise stage of the production missile, but powered by existing turbojets, and capable of takeoff and landing from a runway, allowing reuse. Phase 1 of the revised development program would use this drone to test the aerodynamics, structural concepts, autopilot, and inertial navigation systems in an aluminum structure that could achieve speeds of up to Mach 2. 1.

Although a test vehicle, the X-10 was designed for use as an intermediate-range supersonic cruise missile should the Air Force desire to put it into production. A forward fuel tank in the fuselage was unused in the test vehicle; and a warhead compartment was used for the PIX10 autopilot, telemetry system, cooling system, and nose landing gear. A weaponized version would have deleted the landing gear and systems, and been capable of carrying a 3150 kg nuclear warhead over a range of 2000 km.

The Navaho, with its delta wings cropped at the Mach angle, variable inlets, and forward canards to control pitch moment in the transonic region, was an incredibly futuristic design when it was first conceived in 1947. Its aluminum body was designed to maintain its strength during sustained Mach 2 cruise would heat it to 240 deg C. Systems were cooled by running hydraulic fluid around them, which in turn passed through the main fuel tank, which acted as a large heat sink.

The X-10 was in advance of anything else conceived in 1947, and anything else even flying in the 1950's. There was nothing else powered by turbojet engines that could beat it in thrust/weight, aerodynamics, speed, or altitude during its flight test period. However, since it was unmanned, and highly classified, it obtained no official records.

The most troublesome aspect of the X-10 were the 'supplemental' systems that were designed to make it recoverable and reusable. The drag chute just could not be made to work, and time and again the ground barrier systems failed. In retrospect, trying to make the vehicle reusable and recoverable may have been a big mistake. The 13 vehicles built made 30 flights, but many of those were wasted just working out the autoland system, and only one vehicle survived the test program. An expendable vehicle, or one with a jettisonable data capsule, could have achieved the test objectives, faster, using the same number of air vehicles. Perhaps for this reason, the Air Force decided to abandon recovery of many of the next-generation test Navahos.

Following 15 flights at Edwards, X-10 flight test was moved to Cape Canaveral. A further 12 developmental flights were made here. The last X-10 at the Cape was used as a target drone for Bomarc surface-to-air missile tests until it was lost. The surviving X-10, the first built, is preserved at the USAF Museum in Dayton, Ohio.

Manufacturer: North American. Launches: 30. First Launch Date: 1953-10-14. Last Launch Date: 1959-01-26. Launch data is: complete. Payload: 3,150 kg (6,940 lb). Liftoff Thrust: 97.000 kN (21,806 lbf). Total Mass: 19,183 kg (42,291 lb). Core Diameter: 1.71 m (5.61 ft). Total Length: 20.17 m (66.17 ft). Span: 8.59 m (28.18 ft). Standard warhead mass: 3,150 kg (6,940 lb). Maximum range: 1,370 km (850 mi). Number Standard Warheads: 1. Standard warhead: W13. Boost Propulsion: Turbojet. Boost engine: XJ40-WE-1. Guidance: Inertial+Stellar/Radio Command. Maximum speed: 2,350 kph (1,460 mph). Ceiling: 15,200 m (49,800 ft). Development Cost $: 679.800 million. in: 1956 average dollars. Total Number Built: 13. Flyaway Unit Cost $: 10.000 million. in: 1985 unit dollars. Cost comments: Development cost through program cancellation for all Navaho versions.

• Stage Number: 1. 1 x Stage: Navaho X-10. Gross Mass: 19,183 kg (42,291 lb). Empty Mass: 11,700 kg (25,700 lb). Thrust (vac): 96.948 kN (21,795 lbf). Isp: 1,800 sec. Burn time: 2,000 sec. Isp(sl): 1,800 sec. Diameter: 1.71 m (5.61 ft). Span: 8.59 m (28.18 ft). Length: 20.18 m (66.20 ft). Propellants: Air/Kerosene. No Engines: 2. Engine: XJ40-WE-1. Status: Out of production. Aerodynamic test vehicle for Navaho missile; Max speed Mach 2.08; range 1320 km.

1946 March 24 - Launch Vehicle: Navaho X-10, Navaho G-26, Navaho G-38, Navaho SSM-A-2.

• MX-770 strategic missile study contract awarded Nation: USA. Program: Navaho. North American received W33-038-ac-1491, a $500,000 letter contract, for study of the MX-770, an 800 km range, supersonic guided missile with a 900 kg nuclear warhead. References: 44.

• MX-770 redirection Nation: USA. Program: Navaho. The concentration on fhe 800-km range missile was to be abandoned. Prototype missiles were now to be produced in three phases. Phase I would produce a missile with a range of 280 to 800 km; Phase II, one of 800 to 2400 km; and Phase III one of 2400 to 8000 km.References: 44.

• US Army Air Corps assigned control of surface-to-surface strategic missiles Nation: USA. Program: Navaho. References: 4460.

• U.S. Army Air Corps becomes U.S. Air Force Nation: USA. Program: Navaho. The Air Force was now a separate service from the US Army. The agreement was made that the Air Force would only handle missiles with ranges over 1600 km. So the range requirement for the MX-770 (later the Navaho) was increased to 1600 km, while carrying a 1350-kg payload with an 800 m CEP, and it became an Air Force missile. The 800-km MX-771 (later Matador) became an Army missile. The MX-775 Snark already had an intercontinental range requirement, and became an Air Force missile.References: 4460.

• USAF wishes to concentrate on longer-range Navaho. Nation: USA. Program: Navaho. The Navaho was redefined by the customer in a revised three-phase program using a rocket booster and ramjet cruise. Track, air, and vertical pad launch were to be studied. The first phase would produce a missile with a range of 1600 km while carrying a 1350 kg warhead. Phase two would produce a missile that could carry a 1350 kg warhead to a 3200 to 4800 km range. Phase 3 would be the intercontinental version, carrying a 4500 kg nuclear warhead to an 8000 km range.References: 221.

• Advanced Navaho concept Nation: USA. Program: Navaho. North American began study of an advanced version of the Navaho, which would use a separate, jettisonable rocket booster. This would allow the cruise stage to be ignited at near-cruise velocity, and to be filled with only ramjet fuel, which would vastly extend the range. In this same month design of the XN-1 inertial navigator is completed.References: 221.

• North American Aerophysics Laboratory moved to Downey. Nation: USA. Program: Navaho. Together with the company's Electromechanical Division, the expanding group was moved into an ex-Consolidated Vultee bomber factory east of Los Angeles. It was here that the Navaho, and later Hound Dog missiles, the Apollo command module, and the Space Shuttle would be built.References: 221.

• Navaho reoriented Nation: USA. Program: Navaho. The XSSM-A-2 1600-km range version of the Navaho is canceled. The three airframes completed are abandoned. The USAF instructs North American to proceed instead with development of a 10,200-km range version of the missile using the same aerodynamics, engines, and navigation systems already in development. This is to deliver a 3150-kg nuclear payload, and is to be achieved by making a separable booster stage with two engines deliver a ramjet-only cruise stage to ignition velocity.References: 221.

• Preliminary design of X-10 begins Nation: USA. Program: Navaho. Although the formal redirection of the Navaho program would not come for two months, North American began design of an aerodynamic and systems testbed. References: 221.

• Navaho specification finalized. Nation: USA. Program: Navaho. The missile, now designated WS-104A by the USAF, was to deliver a 3150-kg warhead with a CEP of 450 m over a range of 10,200 km while cruising at Mach 3 at over 18 km altitude. The final missile would be developed in a three-phase program: Phase 1, using the reusable X-10 drone, would test the aerodynamics, structural concepts, autopilot, and inertial navigation system for the cruise missile using turbojet engines in an aluminum structure to achieve speeds of up to Mach 2. In Phase 2, the G-26 test vehicle would be a 2/3 scale version of the final version, testing the vertical launch booster, and a steel-structure ramjet-powered cruise vehicle that would reach Mach 2.75 and a range of 2300 km. Phase 3 would fly the G-38, the full-sized prototype for the operational system. The payload was sized to match the 20-kiloton W-4 nuclear warhead, 3150 kg in mass, 1.5 m in diameter and 2.3 m long. References: 221.

• Wind tunnel tests of X-10 model Nation: USA. Program: Navaho. North American conducted the tests at its own Santa Susanna facility, taking it up to Mach 2.87. References: 221.

• USAF inspects X-10 mockup. Nation: USA. Program: Navaho. The highly classified Mach-3 design, with cropped delta wing and canards, was far in advance of contemporary manned aircraft. References: 221.

• X-10 detailed design drawings released to the shop Nation: USA. Program: Navaho. References: 221.

• First X-10 completed. Nation: USA. Program: Navaho. GM-19309, s/n 3, was the first completed at Downey. It was placed in a static test facility for five months of tests that verified the structural integrity. References: 221.

• First X-10 delivered to Edwards AFB. Nation: USA. Program: Navaho. The crane dropped the aircraft at Edwards; but the damage could be repaired there. The autopilot and radio control systems had already been verified at Edwards in flights conducted with F-86D fighters and a QF-80 drone aircraft since December. An ET-33 flight control aircraft had been modified to control the X-10 in flight.References: 221.

• First X-10 taxi test. Nation: USA. Program: Navaho. Three taxi tests were conducted through the end of September before the vehicle was considered ready for its first flight. References: 221.

• Navaho X-10 flight 1 Nation: USA. Program: Navaho. Main landing gear doors failed to close; ground control of aircraft lost (ET-33 aircraft took over control of the X-10); main gear failed to lock on contact with runway; pilot drag chute deployed late; brake failure caused damage to two tires. But the drone was recovered.References: 17.

• Navaho X-10 flight 2 Nation: USA. Program: Navaho. Landing gear again failed to retract. It was discovered the drag from the airflow exceeded the hydraulic retraction force over 320 kph. References: 17.

• Navaho X-10 flight 3 Nation: USA. Program: Navaho. Planned transonic flight aborted when telemetry power failed. References: 17.

• Navaho navigation system change Nation: USA. Program: Navaho. The XN-1 inertial system had been replaced by the XN-2 stellar/inertial system in 1951. The XN-2 had been flight tested aboard a C-97 aircraft between April 1952 and May 1953. This is in turn was replaced by the XN-6. The XN-6 introduced paired counterrotating gyroscopes to compensate for the precession errors resulting from the single-gyro-per-axis XN-2 design; and introduced hydrodynamic bearing gyros in place of the XN-2's air bearings. N-6 flight testing began aboard a T-29 in May 1954.References: 221.

• Navaho X-10 flight 4 Nation: USA. Program: Navaho. First supersonic flight; reached Mach 1.47. References: 17.

• Navaho X-10 flight 5 Nation: USA. Program: Navaho. Extended range test of radio control and telemetry in 72.5 minute flight. Supersonic flight not planned. References: 17.

• Navaho X-10 flight 6 Nation: USA. Program: Navaho. Planned supersonic flight aborted. Left main tire blew on takeoff run. Flight achieved, but the gear could not be retracted. Ground loop on landing, the vehicle sustained repairable damage. References: 17.

• Navaho X-10 flight 7 Nation: USA. Program: Navaho. Vehicle crashed and burned after 8 minutes of flight when a fire developed aboard. References: 17.

• Navaho X-10 flight 8 Nation: USA. Program: Navaho. Structural test flight, extreme dive and then pull up at Mach 1.3. References: 17.

• Navaho X-10 flight 9 Nation: USA. Program: Navaho. Test of automatic landing system. System failed and gear would not deploy. Radio-controlled belly landing made on lake bed. Vehicle was repairable. References: 17.

• Navaho X-10 flight 10 Nation: USA. Program: Navaho. Structural test flight. Successfully made extreme maneuvers at Mach 1.84. However automated landing system attempted to make landing flare 6 m below the runway level. Vehicle impacted at high speed and was destroyed. However the flight set a speed record for a turbojet-powered aircraft.References: 17.

• Navaho inertial system tested. Nation: USA. Program: Navaho. Inertial guidance system for Navaho X-10 missile tested in first flight at Downey, California aboard North American's T-39 testbed. References: 17.

• Navaho X-10 flight 11 Nation: USA. Program: Navaho. First successful automated landing system flight. References: 17.

• Navaho X-10 flight 12 Nation: USA. Program: Navaho. Second successful automated landing system flight. References: 17.

• Navaho X-10 flight 13 Nation: USA. Program: Navaho. Supersonic flight aborted when afterburners failed. Automated landing failed. Chute deployed during radio controlled approach, causing the vehicle to auger into the desert and be destroyed. References: 17.

• Navaho X-10 flight 14 Nation: USA. Program: Navaho. First flight of refitted s/n 3, the static test article. Vehicle exploded on gear retraction - it was found that the destruct package was wired to the gear circuit instead of the engine circuit. References: 17.

• Navaho X-10 flight 15 Nation: USA. Program: Navaho. Successful test of automated landing system, certifying the X-10 for operation from the Cape Canaveral skid strip. References: 17.

• Navaho X-10 flight 16 Nation: USA. Program: Navaho. Agency: USAF. Demonstrated planned automated landing, but drag chute did not deploy after landing. The vehicle overran the skid strip, the nosewheel collapsed in the sand in the overrun, the tanks ruptured, and the vehicle burned. References: 872.

• Navaho X-10 flight 17 Nation: USA. Program: Navaho. Agency: USAF. An engine problem resulted in a mission abort. After autolanding the nose wheel developed a shimmy, the vehicle ran off the skid strip, caught fire, and was destroyed. References: 872.

• North American reorganizes Nation: USA. Program: Navaho. With the growth of its missile products beyond the Navaho program, and emerging requirements for the Navaho's navigation and rocket engine systems on ballistic missiles, North American broke up the Navaho program into two new divisions. The Missile Development Division, in Downey, would handle the Navaho missile and Hound Dog air-launched cruise missile, a derivative of the X-10 Navaho test vehicle. The Autonetics Division, would handle inertial navigation and other avionics products, and move from Downey to Anaheim. The Rocketdyne division would handle North American's increasing line of liquid rocket motors, and move to a new facility in the western San Fernando Valley in Canoga Park, close to North American's rocket test facilities in the Santa Susanna mountains. References: 221.

• Navaho X-10 flight 18 Nation: USA. Program: Navaho. Agency: USAF. The vehicle reached Mach 1.9 on a 51-minute long-range flight. It landed successfully. References: 872.

• Navaho X-10 flight 19 Nation: USA. Program: Navaho. Agency: USAF. The vehicle reached a record Mach 2.1 speed and autolanded safely on the skid strip after a 62 minute flight. References: 872.

• Navaho X-10 flight 20 Nation: USA. Program: Navaho. Agency: USAF. Test of high angle-of-attack approach and recovery system. Flawless autolanding on the skid strip with precision short landing (1080 m landing roll). References: 872.

• Navaho X-10 flight 21 Nation: USA. Program: Navaho. Agency: USAF. Ground control system failure resulted in missile crashing at sea at Mach 1.25 200 km from the Cape. References: 872.

• Navaho X-10 flight 22 Nation: USA. Program: Navaho. Agency: USAF. Inertial navigation test. Flight aborted when computer malfunction prevented INS signals from being passed to the autopilot. Successful autoland; drag brake deploy failure; successful engagement by runway landing barrier. References: 872.

• Navaho X-10 flight 23 Nation: USA. Program: Navaho. Agency: USAF. Inertial navigation system test. Flight aborted when computer system failed during takeoff. Successful recovery on skid strip. References: 872.

• Navaho X-10 flight 24 Nation: USA. Program: Navaho. Agency: USAF. Full-range test with final dive maneuver. Swan song of vehicle eight after three successful recovered missions. During takeoff the vehicle was aloft, then settled back to the runway with its brakes locked. The tires burst, the gear failed, the gear doors were in contact with the runway, carving grooves in the pavement as they retracted. Then, astonishingly, the vehicle rose from the runway, completed a successful full-range supersonic flight with terminal dive into the waters off Grand Bahamas.References: 872.

• Navaho X-10 flight 25 Nation: USA. Program: Navaho. Agency: USAF. N-6 inertial navigation test flight. Successful 79-minute flight, marred by pitot icing at one point. Successful recovery. Navigator error reached 3 miles at one point, but was one mile at the end of the mission. References: 872.

• Navaho X-10 flight 26 Nation: USA. Program: Navaho. Agency: USAF. Successful inertial navigation test flight. References: 872.

• Navaho X-10 flight 27 Nation: USA. Program: Navaho. Agency: USAF. Final X-10 flight. After cruise at Mach 1.3 at 75 km, the missile made a dive and precision impact on an island down-range. References: 872.

• Navaho - the beginning of the end. Nation: USA. Program: Navaho. With the Navaho stuck on the pad, and the Atlas ICBM nearing first flight, the Air Force began cutting back funds to the Navaho. Advertising for construction of G-38 production missile support facilities at the Cape was pulled, and the program was rescheduled to accommodate a 32% funding cutback in 1958, with construction limited to 16 G-26 missiles and the first G-38 flight delayed from June 1958 to February 1959.

• USAF cancels the Navaho program. Nation: USA. Program: Navaho. The supersonic intercontinental cruise missile had been made obsolete by the Atlas ICBM. 4,705 employees were laid off the day the termination notice was received via an announcement over the public address system to "stop what you are doing, proceed to the nearest exit, and deposit your badge in the bin indicated". By the end of the month the total laid off at North American alone amounted to 15 ,600 employees. However engineering staff was kept on to launch the five completed G-26 missiles, at a total cost of $4.9 million.

  At the time the program was cancelled full-range G-38 missiles were in fabrication with first flight test planned by the end of 1958. The engines, missile frame manufacturing techniques, inertial and stellar navigation equipment, and telemetry/guidance techniques developed for Navaho established the technical basis for many subsequent US rocket developments.References: 221.

• Navaho X-10 Drone BOMARC target mission 1 Nation: USA. Program: Navaho. Agency: USAF. The remaining X-10's were expended as targets for Bomarc and Nike antiaircraft missiles. The X-10 flew out over the ocean, then accelerated toward the Cape at supersonic speed. A Bomarc A missile came within lethal miss distance. The X-10 then autolanded on the Skid Strip, but both the drag chute and landing barrier failed. The vehicle ran off the runway and exploded.References: 872.

• Navaho X-10 Drone BOMARC target mission 2 Nation: USA. Program: Navaho. Agency: USAF. The X-10 flew out over the ocean, then accelerated toward the Cape. However the Bomarc A failed to launch. Autoland was successful, but again the drag chute and landing barrier both failed, and the vehicle burned after overrunning the runway. References: 872.

• Navaho X-10 Drone BOMARC target mission 3 Nation: USA. Program: Navaho. Agency: USAF. The X-10 was launched with only one electrical generator due to a lack of any remaining spares. As it headed out over the ocean, that generator failed. It lost all electrical power, and crashed into the ocean 105 km downrange. References: 872.

• Navaho program closed out. Nation: USA. Program: Navaho. One G-26 missile delivered to Cape Canaveral but not launched was retained there for the open-air missile park. X-10 s/n 1 was displayed in the Air Force Museum in Dayton. Harrison Storms attempted to sell the USAF on using the completed work for space launches. One proposal was to use the boosters as the first stage of a satellite launcher with Able upper stages. Another was to cluster four of them together and launch an X-15 manned rocketplane into orbit. Nothing came of these proposals. Four completed G-26 missiles and the under-construction G-38 missiles were scrapped.

• Miller, Jay,, The X-Planes, Aerofax, Arlington, Texas, 1988. ISBN: 1857801091. Tremendous account of the entire X- experimental series of US aircraft, including the rocket planes X-1, X-15, and X-20. Another outstanding Jay Miller book. More at amazon.com...

• Gibson, James N, The Navaho Missile Project, Schiffer, 1996. ISBN: 0764300482. The only book available on the fabulous Navaho project. Written by the son of one of the project workers, not nearly detailed enough, but it's all we've got.... More at amazon.com...

• Parsch, Andreas, DesignationSystems.Net, . Outstanding, unique reference for aircraft, missiles, propulsion, and avionics systems. Accessed at: http://www.designation-systems.net/.