If you've ever visited the Sands Space History Center in Florida, hidden behind the SpaceX Launch Control Center just outside the south gate of Cape Canaveral Space Force Station, you've seen the only Navaho missile in existence. The North American Aviation XSM-64 Navaho missile was a surface-to-surface cruise missile with a liquid fueled booster rocket. Despite the project's multitude of failures, its technological contributions to future space launch vehicles makes it one of the most important developments in American aerospace history.
XSM-64 Navaho launch from Florida (USAF)
Development on what would become the Navaho began in December 1945, shortly after the end of World War II. The U.S. Air Force received a proposal from the North American Aviation (NAA) Technical Research Laboratory to continue German missile research. First, the NAA would add wings to a modified V2 rocket. Then, the German rocket engine would be replaced by a more powerful turbojet-ramjet engine. Finally, the new missile would be paired with a liquid-fueled booster for intercontinental range. In September 1950, the Air Force confirmed the program, which would include first the testing of a turbojet vehicle, then an interim missile with a 3,600 mile (5793.66 km) range, and concluding with an operational weapon with a 5,500 mile (8851.42 km) range.
1956 Navaho missile concept art (NASA/Glenn Research Center)
The first version of the Navaho missile was the Navaho X-10 test vehicle. It was the only missile ever classified as an X-plane and the first turbojet-powered vehicle to reach Mach 2, or twice the speed of sound. NAA constructed thirteen reusable X-10's that took off from and landed on runways via remote control between 1953 and 1959. The first five vehicles flew a total of fifteen test flights at Edwards Air Force Base in California beginning on October 14, 1953, though only one survived the program. From 1955 to 1956, another five vehicles performed twelve test flights from the Skid Strip on Cape Canaveral Air Force Station, each of which were painted bright orange to assist with long-range tracking. After testing had concluded, the Air Force used three of the remaining four X-10's as Bomarc missile targets from 1958 to 1959. Although the X-10's were planned to be recovered and reused, as opposed to being shot down by the Bomarc, all three were lost during testing. The only remaining X-10 missile, the GM-19307, was the first to fly and is now on display at the National Museum of the United States Air Force in Dayton, Ohio. The X-10 was the first aircraft to fly a complete mission under inertial guidance and data from each flight met the objectives necessary to proceed to the next phase of the Navaho program, the development of the XSM-64. a
X-10 missile on the Skid Strip (USAF)
The XSM-64 Navaho was one of three strategic surface-to-surface cruise missiles developed by the United States following World War II . b Development was significantly stalled, earning it the nickname "Never-Go Navaho". The vehicle's total length (with the cylindrical booster) was 95.25 feet (29 m) while its length without the booster was 87.33 feet (26.61 m). Its wingspan was 40.25 feet (12.26 m) and its diameter was 6 feet (1.82 m). Navaho had a design range of about 3,600 miles (5,793.66 km) and a maximum altitude of 60,000 feet (18.29 km), which was comparable to a traditional piloted bomber aircraft.
Navaho was a vertical takeoff horizontal landing (VTHL) vehicle that launched at a 90 degree angle. The three engines at the aft of the booster produced 45,000 pounds (20,411.64 kg) of thrust and were fueled by liquid oxygen and kerosene (also known as RP-1). After launch and once the missile reached nearly Mach 3, the twin onboard ramjet engines fired to separate the vehicle from the booster and it continued its journey to its target. If the mission was non-lethal, it returned to a landing strip and touched down using retractable landing gear.
Eleven Navaho missiles launched from Cape Canaveral's Launch Complex 9/10 between 1956 and 1958, most of which ended in unintentional destruction. The first, which launched on November 6, 1956, ended in failure after only 26 seconds. This was followed by ten unsuccessful launch attempts until March 1957 when the second Navaho was airborne for less than 5 minutes. The third exploded seconds after liftoff in April. The fourth, launched in June, was airborne for 4 and a half minutes. After the program's cancellation in July, five additional flights called the "Fly Five" were authorized. The longest of these flights was highly successful, lasting over 42 minutes and exceeding Mach 3. The final two Navaho missiles were launched during Project RISE (Research in Supersonic Environment) and were both unsuccessful. They did not bear the now-iconic red and white stripe pattern. The last Navaho launch from the Cape took place on November 11, 1958.
The XSM-64 Navaho program was cancelled on July 13, 1957 primarily due to advances in intercontinental ballistic missile technology, which were making weapons like the Navaho obsolete. According to nuke.fas.org, cost pressures, lack of positive results, and schedule slips also contributed to the termination of the Navaho missile. c
The remnants of LC-9/10 in 2018 (Aeryn Avilla)
Despite its abundance of failures, the Navaho is an important vehicle in the history of the American space program. New materials were developed to handle the aerodynamic heating during flight while the inertial guidance system was later used on the first nuclear-powered submarines, including the USS Nautilus, the first submarine to complete a submerged voyage to the North Pole. Other missile programs implemented the Navaho's booster engines, cryogenic fuel, and inertial guidance system. The booster engine technology specifically, which was adapted from the German V2, was directly applied to the Atlas, Jupiter, Redstone, and Thor missile programs— the foundations of the launch vehicles that have been sending satellites and people into space for the past six decades. North American Aviation (later North American Rockwell and now Rockwell International, part of Boeing) built the Apollo Command and Service modules in the 1960s and the Space Shuttle Orbiter in the 1970s and '80s.
The XSM-64 Navaho versus the Space Shuttle, two reusable VTHL vehicles launched using boosters and returned using retractable landing gear (USAF / NASA)
In 1964, the Brevard County School Board donated the red and white cruise missile to the Air Force Space and Missile Museum, now the Cape Canaveral Space Force Museum. The booster was donated by the Florida Power and Light Company in 1967 and the complete vehicle was on display in the museum's rocket garden until 1996 when it was removed for restoration. It was moved to the Sands Space History Center in 1999, where it welcomed visitors for more than fifteen years. The vehicle was destroyed by Hurricane Matthew in 2016 and spent the next five years in recovery in Hangar C on the Cape. Integrated Construction Management, Inc. of Cape Canaveral oversaw restoration, which also included repairing corrosion from years of exposure to coastal Florida's salty air. The last existing Navaho missile is back on display on the road leading to the Station's south gate, continuing to teach all generations about the foundations of America's missile and space programs and paying tribute to the men and women who dedicated their lives to their country's air and space dominance.
The last remaining Navaho missile in 2023 (Aeryn Avilla)
Author's note: I have no partnership with the United States Space Force Historical Foundation, Inc. but I've loved the Cape Canaveral Space Force Museum and Sands Space History Center for many years and I want to support the Foundation as much as I can. If you're visiting the Kennedy Space Center, I highly recommend taking time to stop by Sands to learn more about military space history. If you're a collector like me, the museum also has a great online gift shop. As always, thanks for reading and be sure to like and share this post (I know it wasn't as spaceflight-related as the rest of my blog, but I've always found the Navaho interesting)!
 The others were the Matador and the Snark missiles.
Landis, Tony R. "Navaho Missile Program: Part 1." https://media.defense.gov/2020/Apr/06/2002275808/-1/-1/0/FLASHBACK_NAVAHO-PART%201.PDF
Lethbridge, Cliff. "Navaho XSM-64 Fact Sheet." Spaceline, https://www.spaceline.org/cape-canaveral-rocket-missile-program/navaho-xsm-64-fact-sheet/
"Navaho." Cape Canaveral Space Force Museum, https://ccspacemuseum.org/artifacts/navaho/
"Navaho (SM-64)." David Darling, https://www.daviddarling.info/encyclopedia/N/Navaho.html b
Scott, Heather L. "Historic Navaho Missile Welcomes Visitors Once Again to CCSFS." Space Launch Delta 45, 31 Mar. 2021. https://www.patrick.spaceforce.mil/News/Article-Display/Article/2557057/historic-navaho-missile-welcomes-visitors-once-again-to-ccsfs/
"SM-64 Navaho." WMD Resources, https://nuke.fas.org/guide/usa/icbm/sm-64.htm c
"XSM-64 Navaho Missile." https://www.boeing.com/history/products/xsm-64-navaho-missile.page --- Existed during research (07/27/23), does not as of 08/02/23 a