The scientific tourist #334 — the SM-64 Navaho Cruise Missile

Standing guard outside the entrance gate to Cape Canaveral Air Force Station in Florida, it’s a Navaho cruise missile:

SM-64 Navaho Cruise Missile

If there were an award for the most successful failed development program, I’m pretty confident that the seldom-mentioned Navaho would win it decisively.  While never being fielded, it helped pioneer technologies that had a huge range of application in subsequent years.

But let’s start at the beginning.

After the end of the Second World War, the U. S. Army Air Force saw the need for long-range missiles — but the technology was so immature that they opted to pursue three parallel (and very different) approaches in the hope that at least one would succeed.  The one felt least likely to succeed was that of intercontinental ballistic missiles, building upon the German V-2.  The most conservative approach was that of subsonic cruise missiles — essentially, improving upon the German V-1 missile with a longer-range design that eventually led to the ill-fated Snark.  The third approach was to build a supersonic cruise missile.

North American Aviation won this third contract, and began their work in 1946 by proposing an Americanized development of / improvement on Von Braun’s A4b / A9 boost-glide missile designs.  But the original surplus V-2 rocket engines proved too heavy and the A9 design was unstable at some speeds — so this idea gradually changed into what was essentially a better A9.  Subsequent requirement changes driven by the Air Force (similar to the ones that impacted the Snark‘s development) then extended its required range from 800 km to 1600 km to 4800 km to 8000 km, and its payload from 900 kg to 1360 kg to 4500 kg.

In the process, the Navaho missile morphed into a two-staged tandem affair — a liquid-propellant rocket carrying a ramjet-propelled Mach 3 cruise missile on its back.  The idea was that the pair would launch from the ground under rocket power, then at about 50,000 ft. altitude the ramjets would be ignited and the rocket booster discarded, with the jet-propelled missile taking its warhead to its target.

Development of the missile’s ground-breaking navigation system, its booster rocket engines, and ramjet cruise engines all moved forward in parallel, but with a dizzying array of problems to match their complexity.  Four unsuccessful test flights were launched from Cape Canaveral in 1956 and 1957, not to mention many failed attempts at launches that never got off the ground (earning the program the nickname “Never Go, Navaho”).  By the time the program was cancelled in July of 1957, it was obvious that ICBMs had won the “race” to provide the U.S. a long-range strategic deterrent (even after cancellation, seven more test flights were conducted using already-build Navahos, none of which were 100% successful).

But you can’t say that Navaho died without leaving descendants.  The rocket engine technology it drove would propel the missiles that replaced it (Atlas, Titan, and Thor), as well as the Jupiter and Redstone boosters used by NASA.  The Navaho navigation system would find use in bombers and submarines (and the Hound Dog), with later derivatives finding their way into commercial craft.  Materials and techniques pioneered by the Navaho development paved the way for the aerospace technologies we take for granted today.

The lonely Navaho missile on display outside the CCAFS gate is significant for more than the program’s history, and for the fact that CCAFS was home to the Navaho test launches.  This missile is the sole surviving Navaho airframe.

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