Science at War: Early Guided Missiles

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

Science in this war has worked through thousands of men and women who have labored selflessly and, for the most part, anonymously in the laboratories, pilot plants, and proving grounds of the Nation.  Through them, science, always pushing forward the frontiers of knowledge, forged the new weapons that shortened the war.  -- President Harry S. Truman

                                                                                                                                Thursday, September 6, 1945


In July 2018, the Air Force’s latest guided weapon, the GBU-53B “Stormbreaker” entered operational testing and is progressing ahead of schedule, so much so that it may enter the operational fleet by early 2019. This newest version of the Air Force’s Small Diameter Bomb (SDB), is a 250-pound-class weapon that now uses a millimeter wave radar to pierce all types of weather. It also has a fused-imaging, infrared seeker on the front of the bomb that helps categorize targets.[1] As Jim Merger of Raytheon’s Missile Systems business development stated, “you can tell it, I’m looking for a tracked vehicle?’ And it will classify the different targets for you…and goes, ‘That’s what you’re looking for?’”[2] In addition to its GPS-assisted guidance system, this new version may also carry a laser seeker to more precisely strike the target. It also has two antennas allowing it to communicate on the Link 16 network or an ultra-high frequency communications system. This communications breakthrough allows pilots to send new information to the Stormbreaker after the weapon has left its launch platform, be it a fighter or a bomber. Merger excitedly highlighted, “Imagine…they [an aircrew] have to defend against swarming boats. You can start sending a whole bunch of the SDB IIs out to go find the boats as you are providing information to them, data linking to them.”[3] While the Stormbreaker will provide the Air Force and Navy with an all-weather weapon that can find its own targets while receiving updates from its launch vehicle, the real question is, how did the Air Force get to this point? It began a 100 years ago, with a Bug. 

Shortly before America entered World War I, the ancestors of today’s Airmen began experimenting with remotely-controlled aerodynamic missiles. After witnessing the Navy’s failed attempt to create an aerial torpedo, Major General George Squire, Chief of the Army Signals Corps, ordered the Army to create a similar program. In January 1918, he contacted Charles Kettering, an Ohio native and founder of Delco, to request that he and the Dayton Wright Airplane Company develop and deliver 25 aerial torpedoes for the Army. 

As a result, a small team led by Kettering, with Orville Wright as an aeronautical consultant, developed a small model airplane powered by a two cycle, four-cylinder engine producing roughly 41 horse power with a gyroscope for stabilization and pneumatic controls for guidance. The aircraft initially carried about 185 pounds of explosives, but Kettering would eventually modify the craft to lift a 300 pound bomb load. The Army officially referred to the aerial torpedo as the Liberty Eagle, but most used another name, the Kettering Bug. As designed, prior to launch, technicians would determine the distance to the target and how many engine revolutions it would take to reach that point. With that information, they would set a revolution counter inside the Bug. To get the Bug into the air, Kettering devised an inexpensive launch system consisting of a four-wheeled cradle that rode on rails.[4] They used this system to catapult the Bug down the rails and once in flight and headed to the target, the revolution counter would reach the desired value, a cam would drop down to shut off the engine and retract bolts attached to the wings. The wings would fall off and the Bug would plunge to the target.[5] 

Kettering Bug Construction

 Kettering Bug construction at the Wright Airplane Company.


On 2 October 1918, Kettering launched the Bug on its maiden flight, but the tiny airplane climbed too steeply after takeoff, stalled, and crashed. A few days later, on 5 October 1918, he launched another Bug which flew for almost an hour before crashing near Xenia, Ohio. As the Deputy Director of Military Aeronautics and observer of the Bug’s successful flight, Lt Col Henry “Hap” Arnold enthusiastically requested that Kettering manufacture 100 aerial torpedoes for use in France, but the war ended before the military could test the 45 completed Bugs in combat.[6] 

Kettering Bugs ready for launch Oct 1918

Kettering Bug ready for launch, circa October 1918.


Soon after the armistice, the U.S. began its traditional breakneck demobilization and Lt Col Arnold became Major Arnold and received a new assignment. Though his interest in innovation continued, in his new assignment he could not provide the Bug the needed support to keep it alive in its current form. The following year, in August, the Air Service shipped twelve Bugs to Carlstrom Field, Florida for testing and between September and October of that year, attempted fourteen flights, with only four being successful.[7] The longest flight was sixteen miles which ended due to engine trouble. Lt Col Guy Gearhart, now in charge of the Air Torpedo Branch of the Airplane Engineering Department at McCook Field, Ohio reported that he believed the Bug needed a self-propelled launching car or a better catapult device for the launch sequence, larger gyros to provide additional stability, and a better engine.[8] During conferences concerning the progress and future of the aerial torpedo, held in March 1920, the Air Service decided it would be easier to move away from the smaller size of the Kettering Bug and install equipment in a man carrying airplane so that a pilot could take control if the experimental equipment failed to function properly. This option would also eliminate the need for a catapult. 

Though the Bug’s life had been cut short, the experiment formed a foundation for continued work and the aerial torpedo concept continued, albeit in a full-sized, man-carrying aircraft. In February 1920, the Air Service let several contracts, to support the aerial torpedo program including one to the Sperry Aircraft Company, who would develop better gyroscopes. They installed these devices in a Standard E-1 airplane and also constructed five Messenger Airplanes for testing. In May of 1921, Colonel Gearheart took the airplanes to Mitchel Field, New York and began flight testing. That summer the test team conducted several flights and though many resulted in reasonable distances with varying results in accuracy, it was impossible to place airplanes in line and expect the gyroscopic controls to work with any degree of satisfaction. Eventually, through trial and error, the test team made corrections and by November several flights traveled near thirty miles with a considerable degree of accuracy. However, between December 1921 and April 1922, the group debated the impossibility of maintaining a predetermined course without some type of course correction equipment. As a result, in June 1923, the Chief of the Engineering Division at McCook Field reported that “The development of the Aerial Torpedo has reached a point that it becomes evident that the use of a remote control by radio will play an important part in the perfections and application of this weapon.”[9] In 1924, contractors installed an automatic take-off and control apparatus in the test airplanes and the test team moved their operation to Langley Field, Virginia. While there, the team demonstrated that the airplane could take off and climb to the preset altitude without human assistance. It was reported that, “The future possibilities of the use of the Aerial Torpedo are numerous, their main one being to have much greater range than the Artillery, i.e., they could reach Depots of Ammunition and supplies far behind the enemy line.”[10] There was talk of superimposing radio control upon the automatic pilot to control the torpedoes as a group from either home station or an orbiting airplane. In November 1924, the Chief of the Air Service approved the purchase and installation of radio equipment, but the weight of the equipment would impede quick testing. As a result, the program stalled for the next few years and because of a lack of funds, in May 1932, the Army stopped all work on a bomb-carrying aerial torpedo. 

During this time, Major Arnold served as the commander of the Fairfield, Ohio, Air Depot and the Chief of the Field Service Section, Material Division and was intimately involved with this and many other cutting edge programs, but he would soon be a the center of all decisions. In early 1931, the War Department again promoted Arnold to Lt Col and reassigned him to command March Field, in California. While there he would seek out a new bombing and gunnery range, located near Muroc dry lake bed in California. This spot would become the future location of the Army’s embryonic guided weapons test program.[11] On Christmas Eve, 1936, Arnold moved once again, was promoted once again and was now the assistant Chief of the Air Corps, second only to Maj Gen Oscar Westover. At this time, the aerial torpedo program was all but dead, but in early 1938, the Army Air Corps successfully flew and landed an airplane using radio and automatic controls. With that effective demonstration, in August 1938, General Westover, re-activated the bomb-carrying aerial torpedo program.[12] The next month, Westover left Arnold in Washington D. C. and flew inspection tours of the Air Force bases and manufacturing facilities. Unfortunately, on the 21st, Westover crashed his Northrop A-17A, killing himself and his crew chief SSgt Samuel Hymes. Arnold was now the Chief of the Air Corps and would have directed influence on the future of guided weapons development.[13] Seven days later, on 29 September 1938, he issued the requirements for an aerial torpedo: range 20 miles or more, the ability to hit a pre-determined target two miles square, and a warhead weighing approximately 200 pounds.[14] The request for bids went out in December 1938, but only the Vega Airplane Company submitted preliminary engineering design data. 

Early Muroc, GM A-1 Bug

 Early Muroc, General Motors A-1 Bug.


In September of 1939, Mr. Kettering, now General Manager of the Research Laboratories Division of General Motors in Detroit Michigan, wrote to General Arnold in reference to the aerial torpedo contract. He disclosed to Arnold that since the end of WWI he and his company had continued to advance engine design and that the Instrument Department had developed certain apparatuses that would lend themselves to enhanced directional control. He believed that he could build a robot plane with a 150 horse power motor, complete with controls and a radio, which weighed between 1,200-1,500 pounds. He also thought it would cost no more than $1,500 per unit.[15] General Arnold responded a short time later reviewing the Air Service’s progress to date, but emphasizing the need for lessons learned. 

With regard to the aerial torpedo, I am convinced that we must continue the development of this weapon; however, we must harness our research efforts to definite military objectives. Our failure in the past to follow up in a logical manner the knowledge gained on the early experiments was due in part to the tendency to experiment for the sake of research, thereby losing sight of the original concept of the aerial torpedo which demanded that it be capable of being produced cheaply and quickly.[16]

General Arnold stressed that the aerial torpedo needed to travel 100 miles and strike a target in a circle one-half mile in diameter. This drastic change, compared to the original 1938 request, was more than likely linked to the evolving concepts of strategic bombing and how the Air Forces would strike deep behind enemy lines. Arnold would later officially codified this need in January 1940 letter, but at this early stage, he provided Kettering some vital insider knowledge.[17] In addition, the aircraft needed to carry 200 pound of explosives, reach an altitude of 20,000 feet, and be radio controlled from either another airplane in the air or a person on the ground. Unit cost was $300-500, less the control equipment. Kettering responded a few weeks later telling Arnold that General Motors could meet the requirements.[18] On 18 February 1941, the War Department signed a $250K contract with the General Motors Company to build 10 aerial torpedoes. The War Department dubbed the effort Project MX-53 and referred to the aerial torpedo as the GM-A1, but Kettering resurrected a name from the past, the Bug.[19] 

Prior to letting the aerial torpedo contract, Maj F. O. Carroll, who had been a project officer for and assigned to the guided airplane and weapons program since March of 1930, began working with Captain George. V. Holloman, the Director of the Instrument and Navigation Unit at Wright Field. Holloman had been central to the evolution of aircraft navigation systems and had won the Mackay Trophy in 1937 for his work on the first aircraft auto landing system.[20] Holloman believed that the aerial torpedo would function in much the same manner as a long range artillery piece, but better. First, if weather obscured the target, the Air Service could send an aerial torpedo in place of the bomber. If the enemy had overwhelming air supremacy that placed aircrews in danger, the Air Service could send an aerial torpedo in place of the bomber. And lastly, when targets of opportunity were beyond the range of artillery and no bombers were available for the mission, the Air Service could sent an aerial torpedo in place of the bomber. At this early stage it was agreed by all, that ground crews would catapult the aerial torpedo into flight, similar to the concepts developed during WWI.[21] 


 Captain Holloman working remote control target drone.


Shortly after the War Department let the contract for Kettering’s updated Bug, Maj Gen Oliver Echols, Chief, Materiel Division, initiated an Air Corps glide bomb project. Through intelligence sources, Major Holloman had learned of the British glide bomb program and requested data with hopes of building an American version.[22] In a February 1941 meeting, he learned that the British had steadily advanced their guided weapons concept and were now exploring options of adding television, infrared, or radar guidance. However, both General Echols and Lt Col Carroll, feared legal and financial complication resulting from the use of the British design and decided to proceed alone.[23] General Arnold understood this, but wanted a guided weapon quickly. By the first week of March 1941 his frustration was mounting. Major Benjamin Chidlaw, who had been the Chief of the Experimental Engineering Branch at Wright Field and central to early jet engine development was working for General Echols. He relayed to Lt Col Carroll at Wright Field that General Echols, had talked with General Arnold who had in his customary manner hammered his desk and stated “…action wasn’t happening fast enough!”[24] Arnold demanded that Wright Field bring in some grey-bearded scientists to start working the problems. A few days later an exasperated Arnold stated, “We apparently are all wet in that we are doing nothing towards producing the simple and effective bomb with a set of wings. I want that started at once. There are many young engineers who can put wings on bombs and by test and experiment get control for mass employment.” He suggested that Wright Field take its guided bomb program to Tonopah Field because of the vast desert which afforded a large space for testing experimental weapons, but this was not possible at the time because the War Department had not cleared the mining and grazing claims of local miners and cattle ranchers.[25] Eventually, the War Department contracted the Aeronca Aircraft Company from Middletown, Ohio to build hundreds of glide bombs. Of importance, in a short amount of time, scientists and engineers at Wright Field studied many options for a glide bomb design and eventually developed the final version for Aeronca to build. These bombs were essentially a controllable bomb consisting of a high wing with two booms and tail surfaces, equipped with servo control mounted to a standard 2,000 pound demolition bomb. While Aeronca began constructing the glide bombs, Lt Col Carroll and Major Holloman negotiated with 4th Air Force to build a small test base on the edge Muroc Dry Lake. Unknown to many and lost to history in many respects, the testing of guided weapons would be one of the first test operations at Muroc, arriving several months before the XP-59 experimental jet aircraft.[26]  

wind tunnel

General Motors A-1 Bug at Langley Field for wind tunnel tests.


Testing got underway in the summer of 1941[27] with General Motors first taking it its Bug to Langley Field for wind tunnel tests and then moving its operation to Muroc. On 15 November 1941, with Kettering and Holloman on hand, the test team launched from a carriage on a special track, the first GM-A1. Take off occurred at 91 miles per hour, but the weapon immediately settled and crashed before sufficient lift was established. After modifying some of their procedures, a second test took place on 5 December 1941. The bomb went into a steep climbing right turn after takeoff, the turn was stopped by radio control, but the controllable bomb made a sharp left turn and the radio operator could not respond quickly enough to keep the GM-A1 from crashing. On 8 December 1941, the test team launched the third GM-A1, and though it showed a tendency for over control, it flew for one hour and thirty-five minutes. The Bug continued to have serious control systems problems and the altitude and preset controls were sent back to Detroit for further development in late January 1942. Also on 8 and 9 December 1941, the Muroc test team launched its first glide bombs. Colonel Carroll reported to General Echols that the tests had been successful with a controlled flight of six-and-a-half miles.[28] 

In 1942, some of the weapons testing shifted to Eglin Field in Florida, but not all. By this point a committee studying the problems with the GM-A1 had decided to install television equipment in the weapon to assist in directing the bomb. The group also decided they would launch the weapon from a modified launch car rather than a sled track. The War Department contracted Cadillac to build a suitable launch car which had two engines to provide the needed speed to launch the Bug. The test team launched the fifth Bug on 10 March 1942 and it immediately crashed due to side winds. On 19 March, a successful launch took place and the Bug flew for one hour and fifty-five minutes.[29] Though progress had been made, after the seventh test in April 1942, Colonel Grandison Gardner, the Proving Ground Commander at Eglin, wrote to General Arnold and recommended against building the Bug in large quantity unless the Army could simultaneously train pilot-engineer operations in proportion. At the time, General Arnold needed as many aircrew as possible just to fill the ranks in 8th and 15th Air Forces, so he could not support diverting Airmen to an experimental program. Colonel Gardner stressed, “We should carry on uninterruptedly with the development of these weapons whether we produce them in quantity of not.”[30]

During a visit to Eglin Field in April 1942, General Arnold reviewed the controllable bomb programs and grew angry that the glide bombs had complicated radio controls. With a lack of communication from and to General Arnold, Colonel Carroll and Lt Col Holloman had applied the evolving guidance technology to all the weapons instead of leaving the glide bombs as gyro stabilized dumb bombs as Arnold had wanted. After receiving better direction from Arnold, Colonel Chidlaw, now Chief of the Experimental Engineering Section (Washington D.C.) provided clear guidance. The first priority was to build a simple glide bomb with stabilization only. The second priority was to build a glide bomb with stabilization plus control, be it radio-television, heat, light, or other means. A large scale test took place in August 1942 where ten B-17s released sixty glide bombs.[31] The test proved successful, but it revealed that the amount of drag from the bombs drastically slowed the bombers.[32] After substantial delay, in May 1944, the 41st Combat Bomb Wing took the glide bomb into combat and had marginal success. About 70% of the bombs made it to the target while the other 25% spun out of control. In an after action report written by Brig Gen R. R. Williams, he concluded that the glide bomb could be used against large scale targets, but the need to slow down in order to drop the glide bombs exposed the aircrews to flak. He recommended not using the bombs again.  The Army Air Forces terminated its contract with Aeronca in August 1944 and disposed of the wing assemblies.[33]

test bomb GB-1

GB-1 dropped from a B-17.


Throughout 1942, progress was painfully slow on the Bug, but this appeared acceptable because it had been designated as experimental. Throughout June and July of 1942, the test team conducted additional evaluations finally putting the television system through its paces. With the testing taking place in Florida, considerable moisture and humidity interfered with the radio and television controls.[34] As a result, in August 1942, Colonel Carroll moved the Bug program back to Muroc and tests immediately got underway with the Bug equipped with tricycle-like landing gear or being launched from the Cadillac.[35] Overall, the Bug project continued with moderate success throughout 1942 and into 1943, with delays caused by malfunctions or the dry lake bed being flooded, but many were beginning to question its value. Reasons varied, but it had been calculated that the test team would need to expend 100 additional units in order to build and test a control system that would accurately fly to a target. Also, it was estimated that it would cost the Army Air Forces an additional $700,000.00 and would require an additional 18 months to complete. As expected, after a conference held at Muroc, the Army Air Forces cancelled the program.[36]


 General Motors A-1 resting upon the modified Cadillac launch vehicle.


The early guided weapons programs highlight many important lessons. First, that early Airmen drove success and that relationships between the government and industry were key to pushing innovation. Next, communication was key, and without that communication, goals were misinterpreted and slowed the overall progress. Lastly, and specifically for AFMC’s heritage, facilities were center to accomplishing the mission. Without adequate test ranges, the test team shifted from Muroc, to Eglin and eventually Wendover. With all this said, the success of “Stormbreaker” benefits from the work accomplished by the early missile pioneers and the Bug.


[1] Article, Raytheon Company, “Stormbreaker Bomb: Fewer Aircraft, Greater Effectiveness,”, (accessed 1 October 2018). 

[2] Article, Oriana Pawlyk, “US Fighters May Carry Stormbreaker Foul-Weather Bomb By Next Year,” DEFENSETECH,, (accessed on 1 October 2018).

[3] Ibid.

[4] Essentially an early version of the sophisticated sled tracks now used at Holloman Air Force Base, New Mexico. 

[5] Memo, Maj H.H. Arnold, Chief of the Material Division to Chief of the Air Corps, “Aerial Torpedo,” 18 August 1930; Memorandum, Chief, Plans Division, O.C.A.C. to Chief of the Material Division, “Detail Progress Report Of Aerial Torpedo Development Arranged In Chronological Order,” 18 August 1930.

[6] Memorandum, Chief, Plans Division, O.C.A.C. to Chief of the Material Division, “Detail Progress Report Of Aerial Torpedo Development Arranged In Chronological Order,” 18 August 1930.

[7] Memorandum, Lt Col Guy L. Gearhart (Air Torpedo Branch) to Colonel Bane (Airplane Engineering Department), “Test of Air-Torpedo,” 29 August 1919. 

[8] Memorandum, Chief, Plans Division, O.C.A.C. to Chief of the Material Division, “Detail Progress Report Of Aerial Torpedo Development Arranged In Chronological Order,” 18 August 1930.

[9] Ibid

[10] Ibid.

[11] Richard G. Davis, “HAP Henry H. Arnold, Military Aviator,” Air Force Fiftieth Anniversary Commemorative Edition, (Air Force History and Museums Program, 1997), 15; H.H. Arnold, Global Mission, (New York: Harper and Brothers, 1949), 135-136.

[12] Report, “Summary of POWER DRIVEN WEAPONS developed by Special Weapons Branch Equipment Laboratory,” 20 November 1943; Letter, Maj Gen Oscar. Westover, “Aerial Torpedo Development,” 8 August 1938. 

[13] Richard G. Davis, “HAP Henry H. Arnold, Military Aviator,” Air Force Fiftieth Anniversary Commemorative Edition, (Air Force History and Museums Program, 1997), 19.

[14] Memorandum, H. H. Arnold to The Adjutant General, “Military Characteristics of Aircraft,” 29 September 1938. 

[15] Letter, C.F. Kettering to Maj Gen H. H. Arnold, “Advances in technology that would help aerial torpedo project,” 7 September 1939. 

[16] Letter, General H. H. Arnold to C. F. Kettering, “Response to 7 September 1939 letter concerning aerial torpedo,” 3 November 1939. 

[17] Memorandum, H. H. Arnold to The Adjutant General, “Military Characteristics of Aerial Torpedo,” 15 January 1940. 

[18] Letter, C.F. Kettering to Maj Gen H. H. Arnold, “Response to 3 November 1939 letter concerning aerial torpedo,” 28 November 1939. 

[19] Contract, War Department with General Motors Corporation, Research Laboratories Division,” 18 February 1941. 

[20] Website, National Aeronautics Association, “Mackay 1930-1939 Recipients,” (accessed on 28 September 2018.)

[21] Memorandum. Captain George Holloman to Assistant Chief, Materiel Division, Wright Field, “Data on the Development of Aerial Torpedoes ad Airplane Equipment,” 17 May 1940. 

[22] Report, Major George Holloman to War Department Air Corps Materiel Division, “Report of Visit of Wing Commander James D. Bruce of the British Air Commission to the Materiel Division, Regarding Dirigible Bombs,” 18 February 1941. 

[23] Report, Air Technical Service Command Historical Office, Wright Field, “Summary of the GB-1 Project,” September 1944.

[24] Record, “Long Distance Telephone Conversation between Lt Col F. O. Carroll and Major B. W. Chidlaw concerning guided weapons progress,” 7 March 1941. 

[25] Report, “Routing and Record Sheet, Summary Glide Bombs and Glide Torpedoes,” 17-18 March 1941.

[26] The XP-59 arrived at Muroc on 12 September 1942 and first flew on 2 October of that same year. 

[27] Of note, by this point, as a result of the recommendations of the joint Army-Navy conference, the nomenclature was changed from aerial torpedo to controllable bomb.

[28] Memorandum, Lt Col Carroll to Air Corps Materiel Division, “Controllable Bomb, Power Driven,” 25 January 1942; Memorandum, Lt Col Carroll to Air Corps Materiel Division, “Progress Report of Special Weapons Tests at Muroc Bombing Range,” 12 December 1941. 

[29] Report, T.A. Simms, “Controllable Bomb, Power Driven, General Motors, Type A-1,” 24 August 1943.

[30] Letter, Col Grandison Gardener to General H. H. Arnold, “Kettering Power Bombs,” 24 April 1942. 

[31] Memorandum, Col Chidlaw to Chief, Experimental Engineering Section, Wright Field (Col Carroll),” 21 April 1942. 

[32] Because the bombers at the time had been designed to carry the standard general purpose bombs without wings, engineers at Wright Field designed a make shift bomb release mechanism onto the outside of the B-17.

[33] Report, Air Technical Service Command Historical Office, Wright Field, “Summary of the GB-1 Project,” September 1944.

[34] Memorandum, Col Carroll to Army Air Forces Materiel Center, “Controllable Bomb, Power Driven,” 12 August 1942. 

[35] Report, Colonel Carroll, “Controlled Bomb, Power Driven,” 15 October 1942. 

[36] Report, T.A. Simms, “Controllable Bomb, Power Driven, General Motors, Type A-1,” 24 August 1943; Memorandum, Brig Gen Chidlaw to HQ AF, “Controllable Bomb, Power Driven, General Motors, Type A-1,” 4 December 1943.