Navaho G-38 Credit - Mark Wade Media Gallery

The intercontinental-range Navaho G-38 was the ultimate development of the German A-9/A-10 concept. At the time the Navaho program was cancelled on 13 July 1957 missiles were in fabrication with first flight test planned by the end of 1958.

Development History

North American had been developing a 1600-km range, Mach 3 missile for the US Air Force since March 1946. The vehicle started out as a derivative of the German A9 boost-glide vehicle, but soon developed completely revised aerodynamics, guidance, and improved propulsion. In February 1948 this project was redefined by the customer as only the first step of a revised three-phase program for a family of vehicles using a rocket booster and ramjet cruise. Phase 3 would be the final intercontinental version, carrying a 4500 kg nuclear warhead to an 8000 km range. In order to obtain the necessary accuracy, North American began development of the XN-2 navigation platform, which coupled the XN-1 inertial system with a star tracker to ensure continued accuracy even in long-range flights. In order to achieve the longer ranges, North American began study of a version of the missile, 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 while the basic cruise missile remained nearly the same size.

By July 1948 the preferred intercontinental Navaho configuration was a delta-winged, recoverable aircraft-type booster looking very much like the B-70 bomber of the 1960's or the reusable boosters of the original space shuttle designs of the 1970's. The cruise stage used a single enormous ramjet engine with a nose intake. By May 1949 North American favored a tandem in-line configuration - a boost stage with a single-ramjet cruise stage atop it. By April 1950, the final Navaho configuration had been settled - a twin-ramjet cruise stage launched strapped to the side of a liquid-rocket booster. This arrangement minimized the length of the vehicle, making handling and erecting on the launch pad easier.

In July 1950, just as the Korean War began, the program was altered yet again. Now the Phase 3 vehicle, dubbed the G-38, would have to carry a 3150-kg 20-kiloton W-4 nuclear warhead over a 10,200 km range. The G-26 phase 2 vehicle, a 2/3 scale version of the G-38, would precede the G-38 in flight test.

Design of the G-38 was begun in 1952. But there were further changes, as the booster fuel was changed from alcohol to kerosene, and the Air Force increased the payload requirement to 4500 kg. These required the vehicle to be somewhat larger than originally planned.

By the time the G-26 pathfinders began flight test in 1956, North American management could see the ballistic missile competition gaining on them. The Thor, Jupiter, Atlas, and Titan development programs were all underway on a crash basis and would begin flight test in 1957. The first tests of the G-26 were dogged with failures - by Independence Day 1957 four launches had been made, all failures. The first in a series of 2,800 km long auto-navigator test flights had been attempted ten times in the first three months of 1957 ever getting off the ground. Wags at the Cape dubbed North America's bird the "Never-Go Navaho". The new ballistic missiles were equally unsuccessful at first, but a Jupiter made a full-range 2100-km flight on 31 May. It was clear that these ballistic missiles, each little more complex than the booster stage of Navaho alone, could deliver a nuclear warhead over the same ranges - at seven times the speed.

Air Force Headquarters terminated the Navaho development program on 12 July 1957. By the end of the month the total staff laid off at North American alone amounted to 15,600 employees. At the time the program was canceled full-range G-38 missiles were in fabrication with first flight test planned by the end of 1958.

Technical Description

The booster followed the same design and layout as that of the G-26, but at 77,140 kg liftoff mass, was 50% larger and equipped with three engines rather than two. The stage was made primarily of 20-24ST aluminum alloy, heliarc-welded and chem-milled between the weld lands. The liquid oxygen tank was forward, the fuel tank aft. Two small fixed separation fins were attached to the intertank structure to ensure the booster would fly away from the cruise stage once released. Aft of the fuel tank was the engine bay, with three gimbaled LR83-NA-1 engines. Two large fixed canted fins were attached to the engine bay, providing vehicle stability during ascent.

The cruise stage had the same fundamental layout as earlier Navahos, but differed substantially in detail. The vehicle had a higher fineness ratio for the increased cruising speed and range. A single slab vertical stabilizer provided yaw control. The trapezoidal wings were completely different from the deltas of the earlier Navahos, with the elevons replaced by independently-moving wingtip elevons for roll control. The full flying canard provided pitch control. At the higher cruise speed and flight duration the G-38 would reach temperatures of 400 deg C. This mandated use of titanium for the nose, wings, and stabilizers. The cruise stage had a mass of 54,400 kg. Its RJ47 ramjets provided 89.26 kN of thrust, allowing the vehicle to cruise at Mach 3.25, reaching an altitude of 21.6 km at the end of mission.

The weapon system would have been guided by an N6B stellar-inertial system and a PIX10 autopilot. The enormous payload bay was sized for one or more nuclear weapons, up to 4500 kg total.

The operational G-38 would have been the first weapon system fielded using all-transistorized avionics and etched circuit boards. The systems were hardened against electromagnetic pulse from nearby nuclear explosions and impervious to jamming. The booster would have produced more thrust than anything America would fly until the Saturn I space booster.

Operationally, missiles would be moved on mammoth transporter-erectors along the interstate highway system (a three-lane road was required) or between shelters on large-area military bases. Missiles on alert status would have the N6B navigation systems operating at all times. This would allow the missile and its support caravan to stop, the missile to be erected, and fired within 30 minutes of a launch order.

Manufacturer: North American. Apogee: 22 km (13 mi). Liftoff Thrust: 1,801.200 kN (404,926 lbf). Total Mass: 131,540 kg (289,990 lb). Core Diameter: 2.37 m (7.77 ft). Total Length: 65.00 m (213.00 ft). Span: 12.25 m (40.19 ft). Standard warhead mass: 4,500 kg (9,900 lb). Maximum range: 10,200 km (6,300 mi). Number Standard Warheads: 1. Standard warhead: W36. Boost Propulsion: Liquid rocket, 3 x Lox/Kerosene. Boost engine: LR-83-NA-1. Cruise Propulsion: Ramjet. Cruise engine: RJ47-W-7. Cruise Thrust: 89.260 kN (20,066 lbf). Guidance: Inertial+Stellar. Maximum speed: 3,700 kph (2,200 mph). Ceiling: 21,600 m (70,800 ft). Development Cost $: 679.800 million. in: 1956 average dollars. Flyaway Unit Cost $: 24.000 million. in: 1985 unit dollars. Cost comments: Development cost through program cancellation for all Navaho versions.

• Stage Number: 1. 1 x Stage: G-38 Navaho Booster. Gross Mass: 76,870 kg (169,460 lb). Empty Mass: 16,780 kg (36,990 lb). Thrust (vac): 2,048.158 kN (460,444 lbf). Isp: 282 sec. Burn time: 90 sec. Isp(sl): 248 sec. Diameter: 2.37 m (7.77 ft). Span: 2.37 m (7.77 ft). Length: 27.43 m (89.99 ft). Propellants: Lox/Kerosene. No Engines: 3. Engine: LR-83-NA-1. Other designations: XB-64A, XSM-64A. Status: Development ended 1958. Burns out at altitude 21,600 m, Mach 3. Empty Mass estimated.

• Stage Number: 2. 1 x Stage: G-38 Navaho Missile. Gross Mass: 54,648 kg (120,478 lb). Empty Mass: 14,512 kg (31,993 lb). Thrust (vac): 89.260 kN (20,066 lbf). Isp: 1,200 sec. Burn time: 10,300 sec. Isp(sl): 0 sec. Diameter: 1.98 m (6.49 ft). Span: 12.25 m (40.19 ft). Length: 26.61 m (87.30 ft). Propellants: Air/Kerosene. No Engines: 2. Engine: RJ47. Other designations: XB-64A, XSM-64A. Status: Development ended 1958. Separates from booster at 21,600 m, Mach 3. Mach 3.25 cruise, 10,200 km range, payload 4545 kg in 3.76 m x 1.78 m weapons bay. Empty mass estimated.

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.

• Spaatz calls for American ICBM. Nation: USA. Program: Navaho. General Spaatz (Tooey Spaatz) calls for US development of missile with 10,200 km range References: 4460.

• Intercontinental Navaho Nation: USA. Program: Navaho. North American settled on a design for the intercontinental version of the Navaho. It consisted of a tandem in-line boost stage with a single-ramjet cruise stage atop it. References: 221.

• Cold War intensifies - US missile programs given higher priority Nation: USA. Program: Navaho. Reacting to Russia's explosion of an atomic bomb, and the Communist victory in China's civil war, the US military begins increasing funding to the low-priority missile development programs begun in 1946. The Martin MX-771 tactical cruise missile is reinstated; additional funds are plowed into the Rascal and Snark programs; and the Corporal tactical missile is modified to carry a nuclear warhead. The Navaho aerodynamic design is frozen so that fabrication of the XSSM-A-2 flight articles can begin.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.

• 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.

• Navaho warhead changed Nation: USA. Program: Navaho. The missile is to carry the 100-kt W-13 device instead of the 20-kt W-4. References: 221.

• X-7 tests prototype Navaho ramjet Nation: USA. Program: Navaho. A 20-inch diameter ramjet, a subscale version of the 40-inch engine for the Navaho, first flies on the X-7 rocket. Of the seven launches, only one was completely successful, and two partially successful. References: 221.

• Preliminary design of the Navaho G-38 begins. Nation: USA. Program: Navaho. References: 221.

• First static firing of LR71 test engine Nation: USA. Program: Navaho. The 540 kN combustion chamber was the most powerful ever tested, but still used the double-walled combustion chamber design of the LR43 rather than the brazed tubular wall construction planned for the production LR71. Build of the first engine to this design would be completed in October.References: 221.

• Navaho engine reaches 445 kN thrust. Nation: USA. Program: Navaho. At Santa Susana, Calif., a complete liquid-rocket engine assembly (Navaho) having a thrust in excess of 100,000 pounds (445 kN) was fired for the first time. References: 17.

• REAP Program Nation: USA. Program: Navaho. North American's rocket group begins the Rocket Engine Advancement Program, to identify improved rocket technology. One early conclusion was that the performance and logistics could be significantly improved by shifting from alcohol to kerosene fuel, using a new specification RP-1. The decision is made to change the propellants for the Navaho G-38 production version booster. The LR71 engine, modified to burn kerosene, would be designated LR83. This in turn was the basic engine that would power the Thor, Jupiter, Atlas, Saturn I, and Delta rockets into the next century.References: 221.

• Navaho engine reaches 890 kN thrust. Nation: USA. Program: Navaho. At Santa Susana, Calif., a complete liquid-rocket engine assembly (Navaho) having a thrust in excess of 200,000 pounds was fired for the first time. References: 17, 278.

• Navaho Weapon System Optimization Study Nation: USA. Program: Navaho. Various nuclear warheads were considered for the Navaho. The G-26 would only be capable of carrying the XW-12, XW-5, or XW-13 fission warheads, or the XW-15 thermonuclear device. North American proposed that the production Navaho be enlarged to carry a 4500 kg payload in a 148 inch x 70 inch diameter envelope. This would allow a high-yield thermonuclear device to be carried.References: 221.

• 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.

• First wind tunnel tests of a full-sized Navaho ramjet engine Nation: USA. Program: Navaho. References: 221.

• Navaho G-38 modified Nation: USA. Program: Navaho. Acting on the North American recommendation of January, the Air Force drops the XW-13 warhead for the production Navaho and authorized production of a larger version to carry a 4500-kg warhead. References: 221.

• 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 G-26 booster static testing begins Nation: USA. Program: Navaho. References: 221.

• USAF inspects Navaho G-38 mockup. Nation: USA. Program: Navaho. References: 221.

• 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.

• North American proposes Navaho acceleration Nation: USA. Program: Navaho. Facing being surpassed by the fast development of the Atlas ICBM, North American proposes Project Broomstick. This would accelerate Navaho G-26 inertial-navigation-equipped dive-in flights to October 1956. This would make the vehicle expendable, removing all the likely problems in developing a recoverable vehicle that was in any case not applicable to production. Deletion of the landing gear and parachutes would also allow greater range to be demonstrated. Altogether it was believed the change would allow G-38 full-scale vehicle flights to start in June 1958 and deployment of the operational Navaho in 1960.References: 221.

• G-38 booster engine test Nation: USA. Program: Navaho. The cluster of three engines produced 1800 kN for 45.5 seconds. References: 221.

• Navaho G-38 design released to production. Nation: USA. Program: Navaho. References: 221.

• 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 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.

• 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/.