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History of Communications-Electronics in the United States Navy, Captain Linwood S. Howeth, USN (Retired), 1963, pages 337-351:
Remote Radio Control
1. EARLY ENDEAVORS TO CONTROL OBJECTS BY RADIO
In 1887, Englishmen E. Wilson and C. J. Evans were successful in controlling slow-moving boats by radio on the Thames River. In 1900 they were granted U.S. Patent No. 663,400 on their method. Nikola Tesla worked upon a similar control idea and, in 1898, built a working model which he successfully demonstrated at the Auditorium in Chicago. He was granted U.S. Patent No. 613,809 on this in 1898. However, Bradley A. Fiske, a U.S. naval officer, had evolved a similar idea a little earlier and he was granted U.S. Patent Nos. 660,155 and 660,156, both underlying Tesla's.1
In 1905 the International Wireless Telegraph Construction Co. contracted with the Quintard Iron Works of Boston for the construction of four radio-controlled torpedoes designed by their chief engineer, Prof. Harry Shoemaker. They consisted of a standard naval torpedo rigidly suspended from a surface float which supported the receiving antenna. The U.S. Government did not consider them of military value, and that archsalesman of radio apparatus, John Firth, was successful in selling them to the Japanese Navy.2
Following this, unsuccessful efforts were made by various individuals in several countries to perfect a radio-controlled torpedo.
2. DEVELOPMENTS BY JOHN HAYS HAMMOND, JR.
John Hays Hammond, Jr., became interested in radio control, and his preliminary work from 1910 to 1912 led to the development of the "automatic course stabilization principle" and a satisfactory method for "security of control."3
The Coast Artillery Corps of the U.S. Army had been seeking a torpedo that could be controlled from a shore site. In late 1912 the Chief of that Corps, Brig. Gen. E. M. Weaver, USA, and his assistant, Col. R. P. Davis, USA, witnessed Hammond's successful radio control of a launch at speeds up to 33 knots. Weaver was sufficiently impressed to detail Capt. F. J. Behr as an observer to the Hammond Laboratory that had been established earlier in that year. Twelve technical sergeants were detailed to operate and maintain Coast Artillery apparatus provided to aid the developments along proper military lines.4
In 1912 the Sperry Gyroscope Co., with the aid of the Navy, developed a reliable motor-driven gyrocompass with remote repeaters. This system was thoroughly tested on the U.S.S. Utah, approved for service use, and adopted as a standard installation for naval vessels. Hammond engineered a modification of this system so that a repeater could control a steering engine. This permitted the simple application of radio control by fitting the gyroscope with solenoids to step its setting to the left or right a fixed number of degrees in response to each control signal. The direction of change was controlled by the timing pattern of a few dashes acting upon the primary control relay.5 The first sustained use of the automatic pilot, commonly called "Metal Mike," was demonstrated on 25 March 1914 when the yacht Natalia was controlled by it throughout a 60-mile run. Although the acceptance of this system as a steering aid for surface vessels and submarines was advocated by Hammond, the Navy was reluctant to utilize it. This stemmed from the fear that automatic steering might increase the chances of collision due to the possibility that too much faith might be placed on it and also that it might not be possible to disengage it and resort to normal methods when necessary. In a conference held on 9 February 1916, Hammond succeeded in allaying these fears.6
The use of the motor-driven gyroscope simplified and contributed greatly to the security of control by greatly reducing the number of required control signals, and by enhancing the difficulty of analysis. The control signals could be changed during a specific run and dummy signals could be transmitted. It was also possible to lock the gyro setting and utilize conventional stabilized course control at will, or, as an alternative, the object could be converted into a target-seeking missile if radio countermeasures were employed against it. Suitable timing patterns at varying frequencies could be employed to increase the difficulty of immediate analysis and ready duplication by an enemy.7
Actually, the Hammond system used dual-channel transmission, a type originally proposed and patented by Tesla. In the earlier Tesla system two receivers, with rectifying detectors, operated two corresponding relays that had to be closed simultaneously to actuate a third one which controlled the pattern analyzing and distributing system. In the Hammond system used on the Natalia, transmission over the dual channels was rapidly sequential from the same transmitter. To produce a control dash first, a half-dash was transmitted on one frequency followed by the second half-dash on a widely separated one. The receiver tuned to the frequency of the first transmission automatically was returned to the frequency for the second transmission, while the first half-dash was held in storage. If the second half-dash was received within a certain established time limit, the first half-dash was released from storage and actuated the controlling relay. The system restored to normal after expiration of the established time limit, or upon reception of the complete dash, and awaited further signals. This was the first use of both time and frequency diversity for security purposes. Other timing patterns controlled engine speed, searchlight shutter opening, and the laying of mines. It was the function of the analyzing and distributing system to identify and channel these signals to the proper mechanism. The target-seeking feature of the system provided directional control by searchlight beam or radio interference. Two selenium cells mounted on the foremast operated differentially until the weapon carrier was headed into a light beam. The radio countermeasures control used cross loops, both of which were tuned to the wavelength necessary for interference, Until the interfering signal was dead ahead, the signal was stronger in one of the loops, activating that portion of the circuit necessary to move the rudder to bring the weapon-carrier course into the direction of the signal.8
3. TEST OF HAMMOND REMOTE CONTROL SYSTEM
On 6 October 1914 tests of the Hammond system were made in conjunction with the U.S. Navy. The U.S.S. Dolphin, fitted with the best available radio equipment and interfering sequentially on frequencies of 1,000, 600, 400, and 300 kc., was not able to exercise control over a surface weapon carrier using frequency modulation on frequencies of 118 and 1,000 kc. until it worked within 250 feet of her. From this distance to the Dolphin it could have been operated with locked gyro or it could have been converted to target seeking. Following further demonstrations on 16 and 24 November the Government considered the project ready for development as a service weapon.9
4. LEGISLATION FOR THE PURCHASE OF THE HAMMOND SYSTEM
Plans for development of the project were submitted to Congress in 1915, too late for consideration.10 On 23 March 1916 Hammond presented a proposal to the War Department which, in turn, presented it to the 64th Congress. A subcommittee of the House Committee on Appropriations in its hearings on fortifications appropriations inquired fully into the following aspects of the system: Interference with the control system by enemy countermeasures; effect of hostile gunfire; limits of operational range; and ability to control the weapon carrier by aircraft.11
The fortifications appropriation bill for the fiscal year of 1917, approved 6 July 1916, appropriated $750,000 for the procurement and exclusive rights of John Hays Hammond, Jr., and the Radio Engineering Co.12 of New York, to their discoveries and inventions pertaining to the radio dynamic control of waterborne carriers of high explosives. Of this sum, the bill authorized the expenditure of $30,000 for conducting a demonstration of the application of the system to the control of torpedoes before a board to be appointed by the President, consisting of six officers, three each from the Army and Navy. The expenditure of the remainder was contingent upon the favorable recommendation of this board. The bill further stipulated that, in the event of the entrance by the Government into a contract with the above parties, the Commissioner of Patents would title the United States with any patents applied for by the above and granted in connection with such a system. Such patents, when titled to the United States, were to be held secure in the Patent Office secret archives. The same bill appropriated $417,000 for the procurement and installation of one radiodynamic torpedo unit. The expenditure of this sum was contingent upon the execution of the contract for the procurement of the exclusive rights in the system.
On 25 August 1916, by direction of the President, the Board was convened with the following membership:
Maj. Gen. Leonard Wood, USA,
Unfortunately, the act of 6 July did not define the type of torpedo to be controlled and this later became a matter of considerable importance to Hammond, the members of the Board, and the two services. The details of the controversies that ensued are beyond the scope of this work and will be dealt with only as they affected the development of a radio-control system.
Cap. John A. Hoogewerff, USN,
Com. David W. Todd, USN,
Lt. Col. George O. Squier, Signal Corps, USA,
Lt. Joseph V. Ogan, USN,
Capt. F. Q. C. Gardner, Coast Artillery Corps, USA.13
5. DEMONSTRATIONS OF THE HAMMOND SYSTEM
On August 1917 Hammond appeared before the Board and read a prepared statement which is appended to the minutes of the Board of that date. In this paper he stated that he proposed to demonstrate his system before the Board by having an operator in an airplane control the movements of a surface boat in such a manner as to cause it to strike moving targets. Both the airplane and the boat were to be offshore a maximum of 15 miles. He closed this statement by expressing the opinion that the satisfactory conclusion of such a demonstration should satisfy the Board and result in their submitting a favorable report.
The Board considered this statement at the same meeting but concluded that, in addition to any demonstration Hammond might desire to make, it desired the following:
(1) A demonstration of the maximum range a surface boat could be accurately controlled by a station located on shore; and,
After a year of preparation, Hammond notified the Board that he was ready to conduct the required demonstration. During that time Lt. Comdr. George B. Wright, USN, relieved Ogan, and Maj. Eugene Reybold, Coast Artillery Corps, USA, relieved Gardner as members of the Board.15
(2) A demonstration of the accurate control of a surface boat engaged in striking a rapidly moving target by exercising the control from an aircraft in flight.14
On 23 August 1918 the Board convened at Fort Monroe, Va., to witness the demonstration. The minutes of the meeting of that date state that the demonstration was conducted to indicate:
(1) the practicability of controlling an unmanned moving vessel either from a shore station or an airplane in flight by radio adjustments of the steering and motor speed functions and, additionally, the control of mine-dropping apparatus by either the shore station or aircraft; and,
Following successful demonstration of the above and lengthy discussion relative to the adaptation of the system to controlling submerged and aerial torpedoes, the Board adjourned without advising Hammond of its findings.16
(2) the ability to control totally submerged vessels by submarine sound signals.
6. ACTION OF THE JOINT TORPEDO BOARD
Several meetings of the Joint Torpedo Board were later held in Washington, and Hammond was requested to attend one held on 31 October. At this meeting he was advised that the Board could not make a favorable finding as the result of the demonstration and indicated a requirement for a demonstration of the control of a completely submerged torpedo. The minutes of the meeting further state that there was a short informal conference with Hammond, but they do not indicate the tenor of the discussion.17 Hammond later wrote that he immediately protested the findings and stated that he felt the Board was not dealing fairly with him; that he had successfully demonstrated what was thoroughly agreed upon; and that the Board was apparently attempting to extract more than had been expected. In the same statement, he wrote that notwithstanding its findings he would continue to improve the system at his expense, feeling that, in all fairness Government officials would provide him assistance in meeting their demands.18
7. AMENDED LEGISLATION FOR PURCHASE OF HAMMOND SYSTEM
From time to time thereafter, Hammond conferred with the Secretary of War and in one of these meetings he explained that he had expended over $400,000 in the demonstrations and was unable to continue further development at his own expense. The Secretary agreed to endeavor to obtain an amendment to the act of 6 July and, on 20 January 1919, addressed a letter to the chairman of the House Appropriations Committee requesting that the $417,000 appropriated for the procurement and installation of one radiodynamic torpedo unit be changed to cover the demonstration of the radiodynamic control of torpedoes and underwater carriers and for installing one torpedo unit.19
Hearings on this proposed amendment were held before the Fortification Committee and, following its favorable recommendation, section 7 of the fortifications appropriation bill for the fiscal year 1920 amended the 1917 appropriation bill as requested. Additionally, this legislation removed responsibility from the Board established by the 1916 act and placed it in the hands of the Secretary of War. The Board was continued in an advisory capacity.
8. THE COAST ARTILLERY WEAPON PROJECT ABANDONED
Hammond immediately proceeded with the work on the assumption that the War Department would bear the burden of the expenses. The size of his laboratory was increased to provide facilities for the Army personnel ordered to assist in the project. He requested funds to pay for this and other expenditures, including the salaries of his engineers, but found the War Department unwilling to utilize the appropriated funds until they were satisfied by reasonable guarantee of the successful completion of the unit required by the amended legislation.20
On 29 July 1921 the officer in charge of the project reported to the Chief of Coast Artillery that, in his opinion, the tactical value of the weapon had been almost entirely lost in view of the recent aircraft bombing tests held off the Virginia Capes.21 On the following day the Chief of the Coast Artillery recommended discontinuance of the project for the above reason, stating that his remarks should not be construed as having any bearing on the desirability of further work looking to the development of the control of completely submerged torpedoes by radiodynamic energy.22
The lengthy statement submitted by Hammond to the Secretary of War on 12 August 1921 summed up the entire project from its conception to the date of the recommendation of the Chief of the Coast Artillery, and in conclusion stated:
. . . I submit that the abandonment of the project as a whole at this time would nullify all of my efforts for the past ten years, would penalize me and my corporation for the good faith and confidence placed in the government and the intensive labors to produce something of value to and desired by the government would cause a serious financial loss of over $450,000 to me and my corporation, would tend to deprive me of the right to secure my award in accordance with the acts of Congress and the written promises of the government, would be tantamount to a breach of contract, and, in my opinion, would not subserve the best interest of the country.23
9. RESEARCH IN RADIO CONTROL OF THE STANDARD NAVY TORPEDO
In 1918 the Navy conducted experiments at New London, Conn., to determine the factors concerned with radio reception in submerged craft. In these experiments the U.S. Bureau of Standards, the Hammond Laboratory, and the Marconi Wireless Telegraph Co. of America cooperated. Tests of a submerged submarine with a 300-foot rubber-covered and sealed antenna supported at a depth of 6 feet proved that radio control of a submerged torpedo by a plane utilizing an 85-watt continuous-wave transmitter on 188-kc. frequency was entirely feasible at that depth.24 As a result of these experiments, the Board recommended that the proper naval weapon using radio control be a standard naval torpedo with an added midsection to house the radio-control equipment. A decision was made to discontinue the development of a surface- or snorkel-type torpedo and to concentrate on the development of the radio-controlled submerged naval torpedo.25
In 1918 the Navy General Board concluded that a radio-controlled underwater torpedo would have decided tactical value and would tend to increase the nervous tension of an enemy. In compliance with this guidance, the Chief of the Bureau of Ordnance directed the Naval Torpedo Station, Newport, R.I., to assist Hammond as much as was practicable in the development of a radio-controlled standard naval torpedo. The letter stipulated that the torpedo should be controlled while running at a depth of 10 feet without the antenna projecting above the water. It also required that the torpedo should be capable of being launched from an above-water tube with the antenna either contained in the torpedo or ejected or reeled out after launching.26 Based upon this directive, work was commenced at Newport with the direct costs being defrayed by the Bureau of Ordnance.
In late December 1921 the Chief of the Bureau of Ordnance advised the Assistant Secretary of the Navy that, as soon as Hammond demonstrated the radio control of a naval torpedo running throughout a distance of 9,000 yards at a depth of 12 feet, he would recommend the question of payment of Hammond be decided.27
Following the withdrawal of Army support the Navy sought a reapportionment of the remainder of the funds contained in the appropriation for fiscal year 1920, and in 1925 Congress approved such action.28
Work continued on the project and in midsummer of 1925, a successful run at an approximate depth of 6 feet was made with the controlling station about 3 miles distant.29 However, 5 years were to elapse before the final tests, meeting the requirements established in December 1921, were completed during the winter of 1930-'31. On 30 July 1932 the Navy concluded the contract provisions of the act of 6 July 1916, and acquired the rights, for radiodynamic purposes, in over 100 Hammond patents.30
10. EARLY NAVY FLYING BOMB RESEARCH, DEVELOPMENT, AND EXPERIMENTATION
In early 1915 Dr. Peter Cooper Hewitt became interested in the development of a pilotless flying bomb and consulted Mr. Elmer A. Sperry, famed for his gyro-stabilization work, as to the feasibility of such an idea. It was agreed that Hewitt would provide $3,000 and the Sperry Co. would endeavor to develop the necessary gyro-stabilization equipment. The project quickly absorbed the $3,000 plus additional funds supplied by the Sperry Co., after which an appeal was made to the military services to continue the project. The possibilities of the project were favorably considered by the Naval Consulting Board which had been established on 7 October 1915 to advise the Secretary on scientific and technical matters. Both Hewitt and Sperry were members of the Aeronautic Committee of this Board.31 The Chief of the Bureau of Ordnance, Rear Adm. Ralph Earle, USN, directed Lt. T. S. Wilkinson, USN, to proceed to the Sperry Co. field station at Amityville, Long Island, to observe and report on tests to be conducted there.
In his report, Wilkinson stated that the tests were twice delayed by engine troubles but were eventually held on 12 September. The report contains a description of the stabilization and coursekeeping devices installed in the seaplane which also carried a pilot since it was not desired that the plane and its equipment be expended. Although the weather conditions were unfavorable, the plane was taken from the water, placed under automatic control, climbed to the preset altitude and maintained this altitude until the end of the preset time, following which it dived sharply and the pilot took control and made a safe landing. Wilkinson concluded that the bomb could not be perfected to the necessary degree of accuracy required for hitting a moving target at sea and recommended that the development be sponsored by the Army as that service might find it useful against large military targets.32
Wilkinson's report notwithstanding, the Naval Consulting Board recommended that the Navy conduct experimental work on automatically controlled aircraft, carrying high explosives, capable of being initially directed and, thereafter, automatically managed.33 A board consisting of Capt. W. S. Smith, USN, senior member; Naval Constructor J. C. Hunsacker and Lts. G. De Chevalier, W. G. Childs, and T. S. Wilkinson, USN, was convened to determine further action to be taken by the Navy.34 This Board recommended that the Navy participate in the project.35 On 22 May 1917 the Secretary approved the recommendation of the Naval Consulting Board.36 He directed the Bureau of Ordnance to allocate $100,000 and the Bureaus of Construction and Repair and Steam Engineering each to allocate $50,000 in support of the project.
A contract was negotiated with the Sperry Co. for experimentation with the ultimate aim of developing a weapon. The Navy agreed to provide five N-9 seaplanes with landplane landing equipment and to purchase six sets of Sperry automatic control equipment. The Sperry Co. was to provide testing grounds, hangar, and such technical staff as the Consulting Board might direct. On 15 June Comdr. B. B. McCormick, USN, was ordered to the Sperry plant, as Naval Inspector of Ordnance, to provide naval supervision over the project. Upon his arrival active work was initiated.
The possibility of controlling the flying bomb by radio was probably discussed by the Naval Consulting Board and by the officers of the Bureau of Ordnance during conferences preceding the Secretary's decision. In one of his first periodic reports, McCormick stated that the development of the project consisted of:
(1) Converting an automatically controlled airplane into a bomb by the installation of distance equipment; and,
He indicated that while radio control was of great importance, the immediate problem was one of launching the bomb. In a letter to Wilkinson, McCormick discussed the project and added a penned comment, "Next important step will be radio control of the torpedoplane from another plane at distance of 5 miles."38 Four days later in another letter to Wilkinson he stated that Sperry advised him that radio control had been satisfactorily developed but that this work was being done by another company.39
(2) Devising a radio control system for this flying bomb which could be controlled by an observer in an accompanying aircraft to direct the bomb to its target.37
Again, in a letter to the same officer he advised caution in applying radio control because enemy aliens were employed in the radio section of the Sperry Co., and also because of the need of first developing a stable missile. He continued, stating that when some satisfactory shots had been achieved and when the enemy aliens have been removed he would be ready to turn over whatever was provided by Hooper, Head of the Radio Division, Bureau of Steam Engineering.40
Meanwhile, on 11 August, Mr. M. M. Titterington, of the Sperry Co., had written Hooper advising him that the Western Electric Co. was developing a radio-command system for the flying bomb. He solicited the Bureau's interest and sponsorship of this project.41
In later correspondence with Wilkinson, McCormick reported that he had visited the Western Electric Co. plant and had inspected their radio-control system and, in his opinion, it was satisfactory and ready for delivery when sufficient progress had been achieved to warrant its use.42 In a letter of 24 September he advised that the Sperry Co. was attempting to develop a radio-control system, but that he did not encourage this because of the work already accomplished by the Western Electric Co.43 Despite McCormick's lack of support, the Sperry Co. continued its work on the radio-control problem and on 18 December 1917 applied for its first patent in this field, issued as U.S. Patent No. 1,792,938.
The design of these early systems of radio control envisioned control of the flying bomb only after it was airborne. This necessitated getting the plane airborne by catapulting. This imposed additional requirements of providing a plane sufficiently rugged to stand the rapid acceleration required and possessing a high degree of inherent stability. Additionally, the automatic control system had to be designed to function without being adversely affected by the rapid acceleration of launching.
Several methods of catapulting were attempted during the next 6 months and,44 finally, on 6 March 1918 the first successful flight of an automatic missile was made.45 The launching was accomplished from an impulse-type catapult powered by a 5,000-pound concrete block dropping a distance of 30 feet and transferring its motion to the catapult car through a system of cables and pulleys. The automatic distance gear was set to cut the throttle of the plane, which was an experimental design of the Curtis Co., after it had traveled 1,000 yards. The plane catapulted cleanly, climbed steadily, and flew in a straight line. The distance device functioned at about 1,000 yards, after which the plane went into a spiral and struck the water without being greatly damaged.46
Another launching was attempted on 7 April. The plane was successfully catapulted, but it failed to rise, settled on the ground, and was wrecked. Despite the previous successful launching it was decided that the flight characteristics of the plane required improvement and that a better method of catapulting than that provided by the weight-powered impulse type was desirable.47 An attempt at launching from an automobile equipped with wheels fitted to a railroad track was unsuccessfully attempted on 17 May.
A month prior to this launching, McCormick had recommended the design of a flywheel-powered type of catapult. The Sperry Co. was directed to proceed with this. They procured the services of Mr. Carl L. Norden, a consulting engineer, who later achieved fame by his design of a stabilized bombsight, to perform the mathematical calculations and design. The genius of Norden was to affect the course of the entire project profoundly. His report on the preliminary work, dated 15 May 1918, recommended a wheel which, revolving at 2,175 r.p.m., would accelerate a mass of 1,950 pounds to a final speed of 100 m.p.h. over a track 150 feet in length. On 24 May he was directed to proceed with the construction of two flywheel-powered catapults.48
A successful launching was made, utilizing this new type of catapult, on 23 September 1918, but after becoming airborne the plane performed erratically and crashed. This further strengthened the opinion that a more rugged plane with better inherent stability was required.49 Another test using the last of three especially designed Curtis planes was conducted on 26 September with like result.
On 3 September McCormick recommended that one of the N-9 training planes, provided by the Navy at the commencement of the project, be fitted for catapulting and automatic control.50 This recommendation was approved and, on 17 October 1918, the plane was catapulted. After leaving the catapult it climbed steadily and flew in a straight line which deviated about 20 to the left of its preset course. The distance-controlling device, set for 14,500 yards, failed to function and the plane continued on its course and was last seen flying eastward at 4,000 feet.51
McCormick, highly impressed with Norden's ability, had asked him to recommend the course for future development of the flying bomb. Norden completed this study on 30 October 1918, recommending better designed planes capable of carrying a check pilot during tests and redesign of the automatic control system so that it could be cut in or out at the will of the check pilot.52
Carrying out Norden's recommendations, new specifications covering the design of the plane were drawn up in cooperation with the Witteman-Lewis Co. which was given a cost-plus-fixed-fee contract to provide five flying-bomb planes capable of carrying a check pilot. On 26 February 1919 the first of these planes was ready for flight tests. In the interim, Norden designed automatic control equipment which could be thrown in or out by the check pilot.53 Three sets of this equipment were constructed at the plant of the Ford Instrument Co., and the Witteman-Lewis Co. was requested to purchase them under their cost plus contract. Two complete sets of Sperry automatic control equipment remained from those previously purchased.54
Except for the provision of services, McCormick's actions had practically eliminated the Sperry Co. from the project. In late 1918 he recommended the entire project be relocated at a naval station. This was agreeable to the Sperry Co.55 By 27 May 1919 the move had been completed and work commenced at the Lower Station, Naval Proving Ground, Dahlgren, Va.,56 under the direction of Capt. T. T. Craven, USN, Inspector of Ordnance in Charge.
Upon completion of the move to Dahlgren it was discovered that the Witteman-Lewis Co. planes were tail heavy and that the ailerons and tail surfaces were too small, thus making the plane dangerous to fly.57 No further flights, except by the Witteman-Lewis Co. test pilots, were made pending completion of changes to the planes.58 Prior to this discovery the catapult had been installed and tested, and three of the new planes had been fitted with Norden equipments and satisfactorily tested under simulated flight conditions.
On 24 October 1919 Norden recommended that the projects be expanded to include the fitting of obsolete planes for use as antiaircraft targets and that automatic pilots be used in spotting planes. He further stated that radio-controlled planes would require automatic controls.59
The necessary modifications to the planes were completed during the winter of 1919-20 and further experimentation was authorized to commence on 30 April 1920, except that no piloted flights were to be launched from the catapult without the authorization of the Bureau of Ordnance.60 The first catapult launching was made on 18 August. The plane became airborne and flew straight for a distance of 150 yards, stalled, nosed over, and dived into the Potomac River. Norden deduced that this was caused by the closing of the throttle during the acceleration of the plane on the catapult and by insufficient electrical power being generated by the windmill generator. He recommended that a pilot be allowed to flight test each flying bomb to make proper adjustments to the automatic control equipment before it was catapulted without a pilot. This recommendation was approved by the Chief of the Bureau of Ordnance.61
The next trial was conducted on 18 November after the plane had been subjected to a flight test during which the automatic controls worked satisfactorily. The launching was perfect, the plane became airborne, climbed slowly, and completed one circle and then reached an altitude of 1,500 feet after traveling a distance of 5 miles. It continued circling and climbing until it reached an altitude of 7,000 feet, at which time the automatic closing of the throttle functioned, the plane went into a spin, and then into a nosedive during which the wings crumpled when about 300 feet above the water.62
A plane was launched on 25 April 1921, climbed for a short distance and then settled slowly, came in contact with the water and upset. During the flight of almost 2 minutes there were no signs of poor stability. Norden was of the opinion that he erred in making the initial horizontal stabilizer setting.63
The Bureau of Ordnance's interest in the flying bomb suddenly commenced to wane. In a letter to the Chief of Naval Operations, the Chief of that Bureau indicated his intention to discontinue further tests unless otherwise directed.64
11. NAVY RESEARCH, DEVELOPMENT, AND EXPERIMENTATION WITH RADIO CONTROLLED AIRCRAFT
On 30 December 1920 the Chief of Naval Operations appointed a board consisting of Capts. L. A. Bostwick, W. G. DuBose, A. S. Hepburn, and C. C. Block, USN, to investigate and report upon the feasibility of the remote control of aircraft by radio.65 This Board recommended that the Navy undertake the project and that it should be placed under the cognizance of the Bureau of Ordnance.66 On 20 January 1921 the Secretary of the Navy approved these recommendations.
Activation of this project was slow. In late October 1921 Lt. Comdr. O. M. Hustvedt, USN, of the Bureau of Ordnance, accompanied by Radio Aid A. Crossley, of the Bureau of Engineering, made several visits to the Naval Proving Ground, Dahlgren, Va., discussed the inactive flying bomb project, and formulated procedures for carrying out the radio-control project.67 These procedures were, for the most part, approved. The design, development, and tests of the radio equipment were made the responsibility of the Bureau of Engineering and were initially carried out at the Naval Aircraft Radio Laboratory at Anacostia, under the direction of Dr. A. Hoyt Taylor. The installation of equipments in planes and flight tests were to be accomplished at Dahlgren under the supervision of the Bureau of Ordnance.
On 17 January 1922 the Chief of the Bureau of Engineering advised the Chief of the Bureau of Ordnance that his Bureau was ready to proceed on the project. Funds were made available by Ordnance and on 28 January the Aircraft Laboratory was directed to begin the work.68
Meanwhile, Hooper, at this time on his second tour of duty as Head of the Radio Division, Bureau of Engineering, had procured the services of Mr. C. B. Mirick and had assigned him to the Laboratory as an assistant to Taylor to carry on this work.69 Mirick, an excellent radio engineer, had served with Taylor as an ensign during the war and had considerable experience with aircraft radio problems.
Before beginning design of a system, Mirick made a tour of various establishments to determine the best type of components available for the projected system. The most productive visit was the one to the Hammond Co., where he found that the components of the radio-control equipment for the standard Navy torpedo were being redesigned so that it could be assembled in small units capable of being installed and serviced through handholes in the radio-control section of the torpedo.70
By midsummer, Mirick selected the following components for the aircraft radio control system:
(1) A continuous-wave transmitter modulated to produce an audible frequency;
With the exception of satisfactory relays, these components were readily available.71 Several types of relays were developed and tested within a few months. One developed by the Naval Aircraft Radio Laboratory proved superior.72 The components were assembled and tested at the Laboratory and later in a piloted F-S-L flying boat about 15 April 1923.73
(2) A device for keying Baudot code;
(3) An amplified receiver capable of tuning a nondirectional aircraft antenna to the frequency of the transmission;
(4) A sensitive, mechanically tuned, vibrating relay capable of being adjusted to the pitch of the modulated signal;
(5) A secondary relay; and,
(6) The Morkum teletype selector operating on the Baudot impulses.
On 11 May 1922, the Bureau of Ordnance directed the Proving Ground, Dahlgren, to proceed without delay to get one of the N-9 aircraft that had been used in the flying-bomb experiments and was fitted with the Norden automatic control system ready for the installation of the radio-control system by 1 July. The radio-control equipment was not ready by that date and was not fitted into the N-9 plane until July of the following year. Norden used this year of grace to further perfect the automatic pilot and to advise the Naval Research Laboratory, which had absorbed the Naval Aircraft Radio Laboratory in April 1923, relative to the linkage requirements between the two control systems.74
Mirick completed the radio-control installation in the N-9 plane on 21 July 1923.75 The automatic pilot with its ancillary equipment weighed 130 pounds and the radio-control equipment weighed 148 pounds.76 The latter consisted of a triangular antenna running from the wing skid fins to the rudder post; a receiver with a six-stage amplifier, designed by Dr. J. M. Miller, of the Naval Research Laboratory; the relays, and the Morkum selector to actuate the proper relay according to the signal received.77 The radio equipment at the control station consisted of a 1-kw. Marconi spark transmitter modified into an alternating current tube transmitter operating on 1200 kc. and capable of providing an antenna current of about 8 amperes.78 This transmitter was keyed by a pushbutton device which transmitted Baudot code.
Prior to 3 August, the plane had been controlled in the air with a safety pilot in simple maneuvers up to distances of 5 miles. The relays were tested satisfactorily to distances of 20 miles. The rudder control was found ineffective when the plane was taxied on the water because the radio control was adjusted for flight speeds.79
Between 18 May and 14 November, 33 test flights were made, all with Lt. J. J. Ballantine, USN, as safety pilot. In the final test of 1923, held on the latter date, a successful demonstration was made before officers of the Bureau of Ordnance. During this 45-minute flight, radio control was used about 25 minutes. Two down-elevator, three up-elevator, six left and five right turns were made by radio control in addition to a number radio signal operating a dummy throttle.80 Following the conclusion of this test it was decided to discontinue operations until spring without attempting a pilotless flight.81
During the winter the radio-control components were improved by the Laboratory and two Vought seaplanes, provided by the Bureau of Aeronautics,82 were equipped with automatic pilots, and an HS flying boat was fitted as an airborne control station. Snap switches were installed in the cockpit to permit the pilot to cut out the entire radio-control system instantly. Flights to test out the improved equipment and the procedure for the use of the airborne control station were resumed on 24 July 1924.83
On 15 September two test flights were made in the N-9 plane during which the automatic stabilization and the radio-control systems functioned perfectly. It was then beached and readied for its first pilotless flight. A bag of sand was securely lashed to the pilot's seat to compensate for his weight. The HS flying boat took station in order to assume radio control if so signaled. The radio and gyro switches were turned on, the motor started, and the wings were held level for 5 minutes to insure that the gyros came up to speed and settled down on course. The rudder gyro was then unlocked, the "on throttle" signal was given by the radio-control station, and the N-9 released. The plane became airborne and was directed through a long series of maneuvers. From the takeoff to the landing, which covered a period of 40 minutes, over 50 signals were made and, except for the right-turn signal, answered promptly. This failure was discovered to be caused by excessive sparking at the transmitter keyboard control and the difficulty was eliminated by reducing power.84 For the first time in history a pilotless aircraft had been put into the air, controlled through many maneuvers, and landed.85 Credit for this achievement belongs to many, but above all to Taylor, Mirick, and Chief Radioman Elmer Luke, USN, of the Research Laboratory; to Norden, of the Bureau of Ordnance; and to Ballantine and Mr. C. C. Middlebrook, of the Naval Proving Ground.
After the flight of 15 September, the radio-control equipment was transferred to the newer Vought plane.86 This installation was completed and the plane was flight tested without automatic pilot control prior to 24 December 1924, on which date flight operations were concluded for the remainder of the winter.
Flight operations were resumed on 19 June 1925 and, by 14 September, 28 test flights had been made, none of which were completely successful. On the latter date Ballantine was relieved by Lt. V. H. Schaeffer, USN. On 28 October a successful test was made with a safety pilot in the cockpit and from that date until the test without a pilot several successful flight tests were made.87
On 11 December a pilotless flight was attempted under ideal weather conditions. The "on throttle" signal was transmitted, the engines tuned up full speed, the plane started along the takeoff course holding an apparently straight course before leaving the water. Just after being airborne the plane porpoised and struck the water four times, bouncing higher each time. After striking the last time the pontoon struts gave way, the nose of the pontoon was cut off by the propeller, the plane nosed up and sank.88
Schaeffer concluded that the failure was caused by the jerky actions caused by the Baudot transmissions and recommended no further pilotless flights until the equipment was modified to give a more graduated and smoother control.89 This condition had been noted by Mirick, and the Naval Research Laboratory had developed a "tuned relay system" which utilized normal pilot controls instead of pushbuttons and gave a much greater degree of control and an almost instantaneous response by the aircraft. Additionally, several controls could be actuated simultaneously.90
Late in 1924 the Laboratory reported it was feasible to control a plane by radio beyond the range of vision.91 However, the project was beginning to follow the pattern of that of the flying bomb. Interest waned, and no action was taken on the Laboratory's report. Proposals were made to improve the control equipment, but no action was taken on these. During the next 3 years improved radio-control apparatus was developed, but no further flights were attempted. The project was not canceled but remained almost dormant until 1936.92
The developments of that year will be covered in a later chapter.93
1 J. H. Hammond, Jr., and E. S. Purington, "A History of Some Foundations of Modern Radio-Electronic Technology," Proceedings, Institute of Radio Engineers, vol. 45, September 1957, p. 1191.
3 Ibid., p. 1192.
4 Ibid., p. 1192.
5 Ibid., p. 1192.
6 Letter, dated 26 Feb. 1958, from E. S. Purington, Vice President of Hammond Research Corp.
7 Hammond & Purington, op. cit., p. 1193.
8 Ibid., p. 1193.
9 Ibid., p. 1194.
10 Ibid., p. 1194.
11 Statement of John Hays Hammond, Jr., to the Secretary of War dated 12 Aug. 1921, pp. 5-6, files, Hammond Laboratories, Gloucester, Mass.
12 This was Hammond's firm.
13 Department Special Order No. 199, dated 25 Aug. 1916, files, Hammond Laboratories, Gloucester, Mass.
14 Minutes of the Joint Torpedo Board dated 24 Aug. 1917, files, Hammond Laboratories, Gloucester, Mass.
15 Orders of the Chief of the Bureau of Navigation (N-31/BR) dated prior Aug. 1918; War Department message dated 21 Aug. 1918.
16 Minutes of the meeting of the Joint Torpedo Board, 25 Aug. 1918, files, Hammond Laboratories, Gloucester, Mass.
17 Excerpts from the minutes of the meeting of the Joint Torpedo Board, 31 Oct. 1918:
"The Act approved July 6, 1916, providing for fortifications and other works of defense, contained in part the following provisions:
"For the procurement of the exclusive rights of John Hays Hammond, Jr., and the Radio Engineering Company of New York (Inc.) to their discoveries and inventions in the art of control by radiodynamic energy of the movement of water-bourne carriers of high explosives, etc. The Act also provided that the funds appropriated for the procurement of the rights above mentioned should not be paid "except upon the approval by the President of a report of a board of three Army and three Navy officers to be appointed by him which report shall be favorable to the acquisition of such rights, such report to be made after a demonstration of the application of the said system to the control of torpedoes.
"The first of the foregoing quotations assumes the existence of discoveries and inventions for controlling by radiodynamic energy the movement of water-bourne carriers of high explosives. The second quotation prescribes a demonstration of the application of these discoveries and inventions to the control of torpedoes. It is the opinion of the present Joint Board that a distinction should be made between the control of water-bourne carriers of high explosives and the control of torpedoes.
"There have been no demonstrations of the application of the said system to the control of torpedoes. There have been demonstrations of the control of surface craft by radiodynamic energy, which demonstrations have convinced the Board of the practicability of this method of control. There have also been demonstrations of the possibility of applying radiosonic control to a completely submerged carrier. There have also been submitted to the Board claims as to the possibility of radiodynamic control of a carrier submerged except for an air-intake pipe. The Board has grave doubts as to the practicability of successfully developing these claims. Before taking final action favorable to the acquisition of the rights to the discoveries and inventions under consideration, it is the opinion of the Board that an actual and satisfactory demonstration of the practicability of such claims should be made.
"If it is claimed that the demonstration of the application of the said system to the control of torpedoes is covered by the demonstration of the application of the system to the control of surface carriers, such claim, while contravening the views of the Board as to the demonstration, required by the Act, would, if allowed, be of no value to the inventor, since in such case the Board would feel constrained to render an unfavorable report as to the acquisition of the rights in question. This action would be based upon the limited value of such means of control. The General Board of the Navy in its letter to the Secretary of the Navy of May 3, 1918 sets forth the reasons why a surface boat controlled by either radio or compressional waves is not suitable for strictly Naval use. Certain of these objections, too, apply equally to the use of this weapon for Coast defense.
"The limited use which might, be made of such boats as indicated in paragraph 18 of the letter of the General Board is not sufficient in the opinion of this Board to warrant the acquisition of the rights at the price specified in the Act of Congress.
"The Board does not consider that it is a part of its province to specify or to suggest to Mr. Hammond the details of the demonstration which would be regarded by it as satisfactory and warrant a favorable report as to the acquisition of the rights in question. It may be stated, however, that the scope of such a demonstration must be such as to establish the validity of the claims made by Mr. Hammond as to the practicability of applications of his method.
"So far, Mr. Hammond has not demonstrated to the satisfaction of this Board that he will be able to make successful application of his methods to the effective underwater attack of Naval craft; but the Board is of the belief that it may be possible to accomplish this in the future. Such a development would have a decided tactical value" (minutes of the meeting of the Joint Board, 31 Oct. 1918).
18 Statement of John Hays Hammond, Jr., to the Secretary of War dated 12 Aug. 1921, p. 18, files, Hammond Laboratories, Gloucester, Mass.
19 Ibid., pp. 19-20.
20 Ibid., pp. 24-29.
21 Ibid., p. 29. Hammond's radio-control system had been utilized to control the bombing targets.
22 Letter, dated 30 July 1921, from Chief of Coast Artillery, USA, to the Secretary of War.
23 Statement of John Hays Hammond, Jr., to the Secretary of War, dated 12 August 1921, p. 34.
24 Hammond and Purington, op. cit., p. 1195.
25 In retrospect it is easy to criticize this decision, but the reader is reminded that, at that time, control of the air was considered one of the major requirements of successful naval operations in order to insure that the naval aviators could act as the "eyes of the fleet." Spotting the "fall of shot" was one of their primary duties and controlling a submerged torpedo did not vary too greatly from this. Not only did submarines and destroyers carry these weapons, but also some of the older battleships. The torpedo had not completely become a weapon of stealth and opportunity, but was looked upon as a means of disrupting an enemy battleline. Nevertheless, as we look back upon naval history we do not find that a single radio-directed submerged torpedo was ever used to sink a ship but that on several occasions such surface-type missiles have been successfully utilized.
26 Letter, dated 21 Nov. 1918, from Chief of the Bureau of Ordnance to the inspector of ordnance in charge, U.S. Naval Torpedo Station, Newport, R.I.
27 Letter, dated 7 Dec. 1921, from Chief of the Bureau of Ordnance to the Assistant Secretary of the Navy.
28 Hammond and Purington, op. cit., p. 1195.
29 Bulletin of Ordnance Information, August 1925, p. 20.
30 Hammond and Purington, op. cit., p. 1196.
31 Lloyd N. Scott, "Naval Consulting Board of the United States," 1920.
32 Memorandum report, dated 13 Sept. 1916, from T. S. Wilkinson to the Chief of the Bureau of Ordnance.
33 Minutes, Naval Consulting Board meeting of 14 Apr. 1917, National Archives, Washington, D.C.
34 Letter, dated 9 May 1917, from Secretary of the Navy to W. S. Smith, 9 May 1917.
35 W. S. Smith, "Chronology of Flying Bomb Work," 31 Jan. 1919, National Archives, Washington, D.C.
36 Naval Consulting Board, North Sea Barrier File, National Archives, Washington, D.C.
37 Letter, dated 10 July 1917, from B. B. McCormick to the Chief of the Bureau of Ordnance.
38 Letter, dated 2 July 1917. from B. B. McCormick to T. S. Wilkinson.
39 Letter, dated 6 July 1917, from B. B. McCormick to T. S. Wilkinson.
40 Letter, dated 21 Aug. 1917, from B. B. McCormick to T. S. Wilkinson.
41 Letter, dated 11 Aug. 1917. from M. M. Titterington to S. C. Hooper.
42 Letter, dated 19 Sept. 1917, from B. B. McCormick to T. S. Wilkinson.
43 Letter, dated 24 Sept. 1917, from B. B. McCormick to T. S. Wilkinson.
44 Letters dated 8 Dec. 1917 and 18 Jan. 1918 from B. B. McCormick to the Chief of Bureau of Ordnance.
45 One 14 Sept. 1914 the Italian Army launched a plane equipped with a gyro control system which rose to a height of 20 feet and then crashed (Edgar Buckingham, 11 Oct. 1918).
On 21 March 1917 the British Army conducted the first partially successful flight using radio control. The plane was launched by a pneumatic catapult from a lorry. The first radio signal was "up," the second "left," and the third "flatten out." These were answered, but, on a second "left" signal the plane made a partial loop, the engine failed and the plane crashed (statements of Maj. A. M. Low and Chief Wireless Officer G. W. M. Whitton, of the Royal Flying Corps).
46 Letter, dated 8 Mar. 1918, from B. B. McCormick to the Chief of the Bureau of Ordnance.
47 Memorandum, dated 8 Apr. 1918, from George Blair to T. S. Wilkinson.
48 Letter, dated 24 May 1918, from B. B. McCormick to Carl L. Norden.
49 Letter, dated 30 Sept. 1918, from A. J. Stone to the Chief of the Bureau of Ordnance.
50 Letter, dated Oct. 1918, from B. B. McCormick to the Chief of the Bureau of Ordnance.
51 Bureau of Aeronautics technical report prepared by D. S. Fahrney, N59-318, p. 111.
52 Ibid., p. 113.
53 Ibid., p. 115.
54 Letters, dated 25 Jan. and 14 Feb. 1919, from B. B. McCormick to the Chief of the Bureau of Ordnance.
55 Letter, dated 2 Jan. 1919, from Elmer Sperry to Chief of the Bureau of Ordnance.
56 Memorandum, dated 27 May 1919, from T. S. Wilkinson to the Chief of the Bureau of Ordnance.
57 Letter, dated 23 Oct. 1919, from W. B. Haviland to the Chief of Naval Operations.
58 Letter, dated 21 Oct. 1919, from the Chief of the Bureau of Ordnance to Inspector of Ordnance in Charge, U.S. Naval Proving Ground, Dahlgren, Va.
59 Letter, dated 24 Oct. 1919, from Carl L. Norden to O. M. Hustvedt.
60 Letter, dated 30 Apr. 1920, from Chief of the Bureau of Ordnance to Inspector of Ordnance in Charge, Naval Proving Ground, Dahlgren, Va.
61 Letter, dated 27 Aug. 1920, from Chief of the Bureau of Ordnance to Inspector of Ordnance in Charge, Naval Proving Ground, Dahlgren, Va.
62 Report, dated 21 Nov. 1920, from Carl L. Norden to the Chief of the Bureau of Ordnance.
63 Bureau of Aeronautics Technical Report, op. cit., p. 122.
64 Letter, dated 27 Apr. 1921, from Chief of the Bureau of Ordnance to the Chief of Naval Operations.
65 Memorandum, dated 30 Dec. 1920, from Chief of Naval Operations to L. A. Bostwick.
66 Report, dated 17 Jan. 1921, from L. A. Bostwick and other Board members to the Secretary of the Navy.
67 Memorandum, dated 21 Oct. 1921, from O. M. Hustvedt to the Chief of the Bureau of Ordnance.
68 Letter, dated 28 Jan. 1922, from Bureau of Engineering to Naval Air Station, Anacostia, D.C.
69 Letter, dated 28 Nov. 1921, from A. Crossley to the Chief of the Bureau of Engineering.
70 Report, dated 25 Apr. 1922, from C. B. Mirick to the Chief of the Bureau of Engineering.
71 Report dated 15 June 1922, from C. B. Mirick to the Chief of the Bureau of Engineering.
72 Report dated 3 Nov. 1922, from Naval Air Station, Anacostia, D.C., to Bureau of Engineering.
73 Report dated 15 Apr. 1923, from C. B. Mirick to the Chief of the Bureau of Engineering.
74 Bureau of Aeronautics technical report, op. cit., p. 158.
75 Letter, dated 10 Sept. 1923, from the Director, Naval Research Laboratory to the Chief of the Bureau of Engineering.
76 Report, dated 18 Dec. 1923. from J. J. Ballantine to the Chief of the Bureau of Ordnance.
77 Report, dated 15 Apr. 1923, from C. B. Mirick to Director, Naval Research Laboratory.
78 Report, dated 7 Feb. 1923, from C. B. Mirick to Director, Naval Research Laboratory.
79 Letter, dated 10 Sept. 1923, from Director, Naval Research Laboratory, to the Chief of the Bureau of Engineering.
80 Report, dated 18 Dec. 1923, from J. J. Ballantine to the Chief of the Bureau of Ordnance.
81 Letter, dated 8 Dec. 1923, from Chief of the Bureau of Ordnance to the Director, Naval Research Laboratory.
82 Letter, dated 27 Dec. 1923, from the Chief of the Bureau of Ordnance to the Chief of the Bureau of Aeronautics.
83 Report, dated 17 Oct. 1924, from J. J. Ballantine to Inspector of Ordnance in Charge. Naval Proving Ground, Dahlgren.
85 As mentioned in footnote 35, the Royal Air Corps had controlled a plane for a few seconds on 21 Mar. 1917 (Prof. A. M. Low, Flight, 3 Oct. 1952). Experiments in radio control of aircraft were conducted in France during 1918 and 1919. Although the plane could be put into the air, maneuvered and landed, no flights were attempted without a safety pilot (Radio News, December 1923).
86 Letter, dated 24 Sept. 1924, from C. B. Mirick to Superintendent, Radio Division, Naval Research Laboratory.
87 Memorandum, dated 15 Dec. 1925, from V. H. Schaeffer to the Inspector of Ordnance in Charge, Naval Proving Ground, Dahlgren.
88 Letter, dated 30 Dec. 1925, from V. H. Schaeffer to the Inspector of Ordnance in Charge, Naval Proving Ground, Dahlgren.
90 Letter, dated 9 Dec. 1924, from Director, Naval Research Laboratory, to the Chief of the Bureau of Engineering.
91 Letter, dated 22 Nov. 1924, from Chief of the Bureau of Engineering to the Secretary of the Navy.
92 During the next decade several attempts were made to reactivate the project. None of these were successful due to lack of funds and differences of opinions of the several material bureaus relative to its feasibility, and cognizance. When it was finally reactivated in 1936 it was for the purpose of providing the necessary target training for anti-aircraft batteries. So great was the success of the project to provide such targets that it became the progenitor of the flying-missile program (second endorsement by the Chief of Naval Operations on a Bureau of Engineering letter of 29 Mar. 1933; Letter, Bureau of Engineering to the Bureau of Ordnance dated 17 Mar. 1926; second endorsement of the Bureau of Aeronautics on a Bureau of Ordnance letter addressed to the Chief of Naval Operations, dated 27 Oct. 1932).
93 The author desires to express his appreciation to Rear Adm. D. S. Fahrney, USN, (retired) for the assistance afforded him by his research into the history of radio-controlled aircraft.
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