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Flashback: The JB-2 and the Dawn of the Sled Track

  • Published
  • By Yancy Mailes
  • Air Force Materiel Command History Office

In the program of research and development, ATSC engineers do not leave a stone unturned. We may never need the robot bomb, for the AAF does not go in for indiscriminate bombing attacks. But if we do need it, we’ve got a good one.
Gen. Bennet E. Myers, Nov. 22, 1944, Deputy Director, Air Technical Service Center

The origins of today’s modern-day sled track owe its existence to the early guided missile programs of World War II, chiefly the JB-2. With that said, at the time, the military did not view the sled track as a test facility, but rather as a means to quickly accelerate a weapon to a minimum velocity so it could achieve flight and strike the enemy. That would change after the war.

Since the dawn of flight, many countries toyed with the idea of a guided weapon. During World War I, America led the way with its Kettering Bug, and during the Interwar Period, Gen. Hap Arnold again looked to Kettering to design and field an aerial torpedo, what became known as the GMA-1. Arnold wanted that torpedo to travel 100 miles, carry a 2,000-pound payload, at an altitude of 20,000 feet, with men controlling the weapons via a radio from either an airplane or a ground station. In addition to the aerial torpedo, Arnold also directed the creation of several other guided munitions including the AZON, RAZON, the GB-1, and the War Weary remotely controlled B-17s and B-24s. The GMA-1 got underway just as Germany invaded Poland while the other programs became a response to the conflict. In most cases these advanced weapons did little to turn the tide of war, but they did serve as a beginning for evolutionary innovation.1

Parallel to the American efforts, and during the Interwar period, the Germans began developing their own wonder weapons. By 1943 they introduced their first visually guided gravity bomb along with a liquid-fueled glide bomb. For years, German scientists and engineers investigated supersonic flow using several indigenously designed and built wind tunnels, so they understood propulsion and stability very well, but they struggled with advanced missile guidance. With a lack of precision for their weapons, the Germans settled on using these poorly guided munitions as terror weapons, or as some labeled them, vengeance weapons.2 

In April 1942, Germany undertook a program to develop what could arguably be the most famous munition of World War II, the Fiesler Fi 103 or as most of the world knew it, the V-1 Flying Bomb. Prior efforts to develop a pulse jet motor had taken years, and with that problem solved, a group of companies submitted a proposal to RLM for an unmanned, medium range flying bomb. The V-1 resembled a small airplane with the stove pipe (the pulse jet) mounted over its tail. The missile had no cockpit, a length just over 25 feet, a wingspan of 17 ½ feet, and carried a one-ton warhead. Its engine ran on standard 80 octane gasoline, the same gas used in trucks and Lorries. Overall, Germany could build the V-1 quickly, at little cost, but it had one major flaw, accuracy. Even so, it would become the perfect weapon to attack London.3

Flight testing, as well as the construction of the two acceleration ramps, got underway at Peenemunde-West in October 1942. Initial drops from a Focke-Wulf Fw 200 Condor proved the V-1’s glide characteristics while acceleration ramp tests demonstrated a ground launch capability. Of importance, the Germans favored the ground launch capability as it improved the V-1’s accuracy. The initial ramp operated on a solid-propellant rocket with a short combustion time. While this system properly launched the test vehicle, it produced a deafening explosion, and discussions after the fact, led engineers to seek an alternative. They later opted for a cylinder accelerator. The new accelerator ramp, metal and inclined, measured 150 feet long and 16 feet high. It had a long hollow tube with a dorsal opening slit along its length. To launch the V-1, workers slid a cylindrical piston with an attached hook into the tube. The hook connected to the V-1. They then packed a combination of hydrogen peroxide and potassium permanganate into the tube and behind the piston. When that combination began to decompose it created expanding gases which created steam and propelled the piston, and in turn, the Flying Bomb.4

Over the next several years and post United States Air Force establishment, a team led by Major Ezra Kotcher, had taken what he referred to as “junk” (captured V-1 parts), reversed engineered that material, and paved the way for the Air Force’s ability to explore guided missiles. Eleven months after the program began the team had launched hundreds of missiles and developed methods for operationally fielded the system.5 Along the way, that small, dynamic team planted the seed corn for what would blossom and become America’s missile effort, but also its sled track program. The sled track provided a test environment where testers could replicate repeatable data points. This started almost immediately as the first five tests resulted in failure, but the sled track provided a solid foundation that allowed testers to make incremental adjustments to the rocket configuration or the missile angle of attack, eventually resulting in success. Kotcher would later comment to Air Force Historian, Dick Hallion, that the JB-2 program had directly influenced the X-1 program. There was “…no paralysis thru analysis because of the immediacy of action necessitated by war before D-Day and immediately following.”6 He noted that four actions proved extremely valuable: building the launching tracks at Muroc, producing the rockets at Monsanto, claiming beach land for the test and camp site and construction in two months, and finally, experience of his first isolated command. He was able to watch others make “big decisions,” but more importantly, he was allowed to “own really big decisions without repercussions or resistance or hesitation.”7 The JB-2 program officially ended in 1948, but it, and the sled track, would go on to influence a host of programs developed during the Cold War.8

Read the full story at Flashback:  The JB-2 and Dawn of the Sled Track


1. Case History, AMC History Office, “Historical Study No. 71, Controlled Missiles – Glide Bombs,” 28 Nov 49, SD 6001; Report, HQ Air Force Materiel Command, “Guidance and Homing of Missiles and Pilotless Aircraft, A Report Prepared for the AAF Scientific Advisory Group,” May 46, SD 6002.

2. Report, Guided Missile Department Antiaircraft & Guided Missile Brach, The Artillery School Fort Bliss, Texas, “Guided Missile Background and First Quarterly Report,” pp 33, 30 Sept 48, SD 6005; Report, HQ Air Force Materiel Command, “Guidance and Homing of Missiles and Pilotless Aircraft, A Report Prepared for the AAF Scientific Advisory Group,” pp 3-5, May 46, SD 6002.

3. David Johnson, V-1 V-2 Hitler’s Vengeance on London, (New York: Stein and Day, 1981), 24-26; Report, Col D. L. Putt, Deputy Commanding General Intelligence, “German Developments in the Field of Guided Missiles,” pp 36, 27 Jun 46, SD 6004.

4. National Air and Space Museum, “Missile, Cruise, V-1 (Fi 103, FZG 76),” Smithsonian, access date 13 Jul 21,; Max Mayer, “Chapter Eight: Luftwaffe Test and Experimental Establishment Peenemunde-West/Usedom,” German Secret Flight Test Centres to 1945, (England: Midland Publishing, 2002), 210-214.

5. Technical Order, “T.O. NO. 11-75BA-3 Pilotless Aircraft Type JB-2,” 1 Jun 45, SD 6065.

6. Notebook, Ezra Kotcher, “Buzz Bomb Draft for #2, 3 Letter to Roche,” nd, retrieved from the AFIT Library, Wright Patterson AFB.

7. Notebook, Ezra Kotcher, “Buzz Bomb Draft for #2, 3 Letter to Roche,” nd, retrieved from the AFIT Library, Wright Patterson AFB.

8. Memorandum, Col George E. Price, “JB-2 Pilotless Aircraft,” 1 Mar 46, SD 6068.