Navaho development Navaho development sequence Credit: © Mark Wade. 7,273 bytes. 614 x 366 pixels.

The Navaho intercontinental cruise missile project was begun just after World War II at a time when the US Air Force considered ballistic missiles to be technically impractical. But the Navaho required a huge liquid fuel booster to get its Mach 3 ramjet up to ignition speed. And as it turned out mastering the Mach 3 air vehicle guidance and materials problem was actually more difficult than solving those of ballistic missiles. In the end, the Atlas ICBM began flight test before the first full sized Navaho could be flown. However the Navaho program provided the technologies that allowed the US to develop ballistic missiles rapidly in order to catch up with the Russians. From the Navaho came the rocket engines for the Redstone, Thor, Jupiter, Atlas, Titan, and Saturn I rockets. Navaho also developed chem-milling fuel tank fabrication techniques, inertial and stellar navigation, and a host of other technologies used in later rockets. It put North American Aviation in a leading position that allowed it to capture the prime contracts for the X-15, Apollo and Space Shuttle projects, thereby dominating US manned spaceflight for the next fifty years.

The goal of the reformulated Navaho program was to produce a surface-to-surface cruise missile capable of carrying a large nuclear warhead 10,200 km at a speed of at least Mach 2.75 with a CEP (Circular Error Probability - diameter within which half of the missiles would impact) of 450 m. The North American Aviation Company was the prime contractor for the missile, with Rocketdyne producing the rocket engines for the booster and Wright Aeronautical Company the ramjet engines for the cruise missile. The program consisted of three phases:

• Phase 1: Sub-scale recoverable models of the cruise missile would be built to verify the aerodynamic design. These X-10 test vehicles used two Westinghouse 10,900-pound thrust J-40-1 turbojet engines for power. Phase 2: A slightly sub-scale version of the booster and cruise missile would be built. This was designated G-26 by North American and XSM-64 by the Air Force. The booster would use two Rocketdyne 120,000-pound thrust rocket engines. The cruise missile would use two Wright Aeronautical Company ramjet engines.
• Phase 3: The SM-64A / G-38 prototype of the full-scale full-range missile would be tested and then put into production. The booster would use three Rocketdyne 150,000 pound thrust rocket engines.

A series of fifteen X-10 flights were conducted at Edwards Air Force Base, California as part of Phase One in 1953 and 1954. North American also began operating a small field office at Patrick Air Force Base in 1953 to co-ordinate support efforts for the program, including the construction of two missile assembly buildings, a vertical launch facility for the XSM-64 and a 70 m x 3000 m landing strip (the �Skid Strip�) at Cape Canaveral for the X-10.

North American tripled its field office staff from 22 to 77 people in 1954. It also began installing equipment in the guidance laboratory, the blockhouse and the Navaho flight control building even before construction of those facilities was completed. The first X-10 was launched from the Cape on 19 August 1955, and the Navaho quickly replaced the Matador as the Range's principal user. Support facilities were completed in the last half of 1955, and seven more X-10s were launched from the Cape over the next twelve months. By the middle of 1956, North American had 605 people working on the Navaho program at Cape Canaveral and Patrick.

Five more X-10 flights were completed in the last half of 1956, but problems with an auxiliary power unit delayed the Navaho�s first launch for six months. Then the result was its explosion 26 seconds into the flight. Three more Navahos were launched over the next seven months with equally dismal results. In addition to those failures, the first in a series of 2,800 km long auto-navigator test flights was attempted ten times in the first three months of 1957 without a single launch.

More promising were successful static tests of the booster rockets and North American's isolation of problem areas revealed in the first four flights.

Then in a surprise message on 12 July 1957, Air Force Headquarters terminated the Navaho�s development. Because the auto-navigator showed promise, the Air Force authorised five auto-navigator flights and one radio command flight with no landing capability. These were somewhat more successful than the earlier series, with one missile managing to reach a range of 2000 km before its ramjets failed.

The seven remaining Navahos were to be tested in support the of the B-70 bomber and F-108 long-range interceptor programs, but after two unsuccessful launches the project was completely cancelled at the urging of the B-70 Weapons System Project Office.

As North American closed out the Navaho program, three X-10s were selected as target drones for Bomarc missile tests. Two X-10�s launched successfully on 24 September and 13 November 1958, but both burned at the end of their missions after running off the end of the Skid Strip. The last X-10 was launched on 26 January 1959, but self-destructed and crashed approximately 105 km downrange after a power failure. It was the Navaho project�s final flight.

Launch Vehicle: Navaho X-10. Aerodynamic test vehicle for Navaho missile; Max speed Mach 2.08; range 1320 km.

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Launch Vehicle: Navaho G-26. The Navaho G-26 was a test version of the operational Navaho G-38 which would have been the fullfillment of the A-9/A-10 concept. Navaho was cancelled due to the success of faster, unstoppable ballistic missiles. But the engines, missile frame manufacturing techniques, inertial and stellar navigation equipment, and telemetry/guidance techniques developed for Navaho established the technical basis for all subsequent US rocket developments. The engine developed for an earlier version of Navaho was used in the Redstone rocket; that developed for the G-26 booster was used in the Atlas A and Atlas B ballistic missiles. The Navaho program was cancelled on 13 July 1957, but the already-built G-26 test missiles were flown to the end of 1958.

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Launch Vehicle: Navaho G-38. The Navaho G-38 was the ultimate development of the A-9/A-10 concept. At the time the Navaho program was cancelled (13 July 1957) the missiles were in fabrication with first flight test planned by the end of 1958. The engines developed for the G-38 booster were used with minor modification for all of the first generation of American orbital rockets - the Jupiter, Thor, Atlas, Titan 1, and Saturn I. They continue to use to this day in the Atlas II and Delta 3.

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