dated November 1961

Chapter 5
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Ord. Mono. 1961, BRLESC, starting page 080



The capabilities of any given computer or computing system are never sufficient to solve all classes of problems efficiently and economically. There will always be a demand for faster arithmetic speed as well as for larger and faster memory. In fact, by 1955 the scientific computing facilities at the Ballistic Research Laboratories, APG, became unable to adequately support Ordnance requirements in the area of ballistic computations. The improved versions of EDVAC and ORDVAC were laboring on a round-the-clock basis. The computer improvement programs which expanded the capability of these computers turned out to be only stop-gap measures. The existing machines were unable to adequately support the more than 100 active problems then being solved in the pursuit of ballistics research and the computation of firing tables and ballistic data for conventional artillery, rockets, and guided missiles. ENIAC was not able to keep up with EDVAC or ORDVAC and was no longer used after 2 October 1955. This placed the entire computation load on EDVAC and ORDVAC each of which operated 168 hours per week, with but a short time off each day for trouble shooting, repair and improvements. Troubles over problem priority began to occur. Day-time computer runs were limited to twenty-minute program checks. Scramble time was a brief period of a few minutes for squeezing in a few high priority problems out of scheduled order. It was obvious that additional computer capacity was badly needed and this in the form of a computing machine that would be far superior to the existing machines.
Ord. Mono. 1961, BRLESC, starting page 081

The state of the art had advanced by 1957 to the point where superior machines were being developed by IBM, Sperry Rand, the Universities of Illinois and California, the Massachusetts Institute of Technology, and the National Bureau of Standards. Other companies and universities were also making rapid progress in the development and production of computing and data processing systems.

The decision was made to support the work of the National Bureau of Standards in exchange for the results of their development program and (in 1957) $50,000 of Ordnance R&D funds were transferred to the National Bureau of Standards to assist in the development of universal logical packages which could be used in the construction of a new, fast, reliable, scientific computing machine. At that time the National Bureau of Standards was committed to the design of their new PILOT Multi-Computer System. The Ordnance funds assisted the Bureau of Standards in arriving at a tentative design of arithmetic, logical and control units. The design and samples of the logical packages were provided to the Ballistic Research Laboratories at Aberdeen Proving Ground. Tests conducted at BRL showed that improvements in the design of the package were necessary. These modifications were approved by the Bureau of Standards and the sum of $175,000 was transferred in February 1958, to the National Bureau of Standards to cover the cost of 6,000 of the packages to be ordered along with the Bureau's requirement for its PILOT Multi-Computer System. At the same time the programming staff of the Computing Laboratory at BRL prepared a description of the instructions to be automatically executed by the new computing machine. Due to the different types of application, the desire for easy programming and for reasons of economy, the Ballistic Research Laboratories at APG and the National Bureau of Standards parted
Ord. Mono. 1961, BRLESC, starting page 082
ways in development. All that remained in common were the logical package and certain aspects of the high-speed arithmetic unit, which used the high-speed carry logic as proposed by the Bureau. The instruction code, physical construction, internal arrangement, control logic, peripheral equipment, and many other aspects differed. The logical design, physical design, and layout of the system was done independently by Computing Laboratory personnel at BRL.

The construction of plug-in units and racks was done under contract by the Technitrol Engineering Company of Philadelphia, Pennsylvania. The development of the high-speed storage element was performed by Ampex Computer Products, Incorporated, of Culver City, California (formerly Telemeter Magnetics, Inc.). The contract, approved by the Chief of Ordnance, called for the delivery of a 4,096-word storage unit with a cycle time of less than two microseconds. The operational unit, after some delays due to technical difficulties, was delivered to BRL on 15 May 1961 under Ordnance Contract No. DA-04-495-ORD-1500 at a total cost of $680,000. Certain other components were also obtained under contract from various companies.

The assembly and logical wiring of the system was performed by Computing Laboratory personnel at BRL. This staff of computer engineers and programmers also conducted the checkout and testing of the system.

The new computing machine was named BRLESC, Ballistic Research Laboratories' Electronic Scientific Computer. It was designed by Ordnance personnel, for Ordnance Corps use, although in every respect it is a
Ord. Mono. 1961, BRLESC, starting page 083
general purpose, high-speed, automatic computer. Its approximate ultimate cost is estimated at two million dollars. BRLESC was scheduled to be in operation by the end of 1961.

The BRLESC is a general purpose, electronic, digital computer with parallel arithmetic mode and synchronous timing. it was designed primarily for the solution of scientific problems in which high computational speed and high precision are required. As the descriptive phrase 'general purpose' implies, the machine may be programmed to perform any task which. is amenable to numerical methods of solution. The applications of BRLESC are as follows:

  1. Exterior ballistics problems such as high altitude, solar and lunar trajectories, computation for the preparation of firing tables and guidance control data for Ordnance weapons, including free flight and guided missiles.

  2. Interior ballistic problems, including projectile, propellant and launcher behavior, c.g. physical characteristics of solid propellants, equilibrium composition and thermodynamic properties of rocket propellants, computation of detonation waves for reflected shock waves, vibration of gun barrels and the flow of fluids in porous media.

  3. Terminal ballistic problems, including nuclear, fragmentation and penetration effects in such areas as explosion kinetics, shaped charge behavior, ignition, and heat transfer.

  4. Ballistic measurement problems, including photogrammetric, ionspheric: and damping of satellite spin calculations, reduction of
    Ord. Mono. 1961, BRLESC, starting page 084
    satellite doppler tracking data, and computation of satellite orbital elements.

  5. Weapon systems evaluation problems, including antiaircraft and antimissile evaluation, war game problems, linear programming for solution of Army logistical problems, probabilities of mine detonations, and lethal area and kill probabilities of mine detonations, and lethal area and kill probability studies of missiles.

The binary number system is used exclusively in the arithmetic unit of the machine. The input-output routines (programs) automatically convert decimal input information into binary form and, conversely, convert binary numbers into decimal form for output. The arithmetic unit is constructed of standard vacuum tube logical packages, with tube driven, crystal diode logical gating. It contains 1,727 vacuum tubes of 4 types, 853 transistors of 3 types, 46,500 diodes of 2 types, and 1,600 pulse transformers of 1 type. Logical events are controlled by a five-phase mega-cycle clock, permitting decisions at the rate of five million per second.

The storage system of the machine consists of a high-speed magnetic core memory of 4,096 words. Each word is 72 bits long, which is equivalent computationally to approximately 19 decimal digits, since 4 parity bits and 4 sign bits are not included in the operands. The complete read-write cycle time of this memory is 1.5 microseconds. Additional high-speed storage will be added to the machine when funds become available. Also, magnetic drum storage units will be installed as back-up memory. The capacity of these drums is to be about 35,000 words.
Ord. Mono. 1961, BRLESC, starting page 085

The input-output devices of the machine are capable of reading cards, punching cards, reading magnetic tape, and recording on magnetic tape. A maximum of 16 magnetic tape handlers may be installed on line. that is, they are directly accessible to the programmer. Any two magnetic tape handlers, one drum, the card reader, and the card punch may be operated simultaneously under separate automatic controls. Arithmetic processing may occur concurrently with input-output operations. This means that information is processed automatically as it becomes available from an input device and automatic interlocks are built into the machine to insure that the proper information is available.

Information may be transferred to or from the machine by means of punched cards or magnetic tape. All information must be coded in a binary manner since the machine (as most modern computers) can only handle 0's and 1's, that 1s, hole or no hole, or magnetization in one direction or the other. The binary number system is used because of the binary nature of most of the devices used in the construction of the machine. The internal workings of the machine are simpler if only pure binary numbers and instructions are used. However, programmed routines can be designed to process any kind of information. The actual information may be a pure binary number, a binary coded decimal number, a binary coded alphabetic character, or literally any type of information the programmer desires. An output routine will arrange this information in the proper format for punched card output if desired, or for magnetic tape output. The punched cards may be tabulated on conventional punched card equipment and the
Ord. Mono. 1961, BRLESC, starting page 086
magnetic tapes may be ready by special converter equipment which operates into a high-speed printer at rates up to 1,500 lines per minute, with 160 characters per line.

BRLESC was designed so that a maximum of concurrent operations can take place whenever possible. A "look-ahead of instructions, words, and indices" feature is incorporated to allow the machine to operate most effectively with a memory which cycles in one microsecond. Also,many special instructions may be executed while the arithmetic unit is working on an arithmetic instruction. In addition, all five input-output trunks may be operating simultaneously.

The control of BRLESC consists of many units, each controlling their associated process, but all regulated by a master control center, which has a pre-determined time priority system and which prohibits the initiation of new events in any of the various concurrent trunks should there be some conflict in the use of information or units. For example, if two tape trunks are to use the same tape handler for different purposes at the same time, the trunk which receives the first request gets priority to use the handler and the other trunk must wait until the first has finished using the handler. Also, should a program want to use information that has not arrived yet from one of five input-output trunks, the master control center recognizes the problem and causes the program to wait until the information is delivered. The master control also recognizes manual commands from a console and then relays the commands to the respective sub-unit.

Magnetic tape speeds operate at an effective rate of 120,000 six-bit
Ord. Mono. 1961, BRLESC, starting page 087
characters per second. Search through magnetic tape in the forward or backward direction by large blocks of information is an incorporated feature. New programs can be located rapidly through the use of file markers. Drum transfer rates are 130,000 seventy-two-bit words per second.

BRLESC is provided with a parity system to check word transfers as they pass through the memory and to or from tapes and drums. The master control unit is altered in the event a non-parity condition occurs.

The computer is designed to operate on an internally stored program of detailed instructions. This feature is the single, most important reason for the tremendous growth of the computer industry, because it makes computers truly flexible and easy to use. Since instructions are in numerical form, arithmetic operations may be performed on them, that 1s they may be manipulated in the arithmetic unit. In this way the program can modify its own instructions during the course of the computation in response to conditions that develop. This allows the programmer to exercise his ingenuity and gives him latitude to do many things without writing a great many detailed instructions.

Another very valuable feature is that the machine can change address in instructions by fixed amounts automatically. This feature is called indexing and permits the programmer to use the same set of instructions to process as much data as he desires simply by changing the index value instead of modifying the basic instructions.

Code checking features will include stopping on any selected address,
Ord. Mono. 1961, BRLESC, starting page 088
the display of the contents of any memory cell, the display of normal or abnormal conditions, the ability to manually store in any selected memory cell, and the ability to transfer control to any part of the system. Parity checking is performed in each of the four 17-bit groups in each word.

It is believed that BRLESC will be a significant contribution to the Ordnance Corps and to the scientific community, because it will permit the solution of problems never before possible due to the excessive amount of time required; and it will solve these problems at a precision which was possible on earlier machines only by complicated, time-consuming methods. {See Appendix IV for technical data of BRLESC.
Ord. Mono. 1961, GUNNERY, starting page 089



The ever present need of the field artillery is a means to solve the gunnery problem with greater accuracy and speed. Tactical requirements are changing constantly at a mounting tempo, with increasing demands being placed upon field artillery in its support of the field army. This is a continuous challenge in the area of fire control where new techniques are being devised, the newest advances in science are being adapted and applied, qualified personnel are being trained for new jobs, and where field artillery is finding the means for meeting the demands for its increased support.

The development and standardization of the Field Artillery Fire Control System M35 was a significant step in the right direction. This system utilized an electromechanical computer and opened a new era in gunnery techniques. The Fire Control System M35 was an improvement over graphical means in both speed and accuracy, but experience with it also pointed to needs for improvement in the over- all fire control problem. The analog system used by this device had several disadvantages. Its accuracy was adequate for the shorter range weapons such as the 105mm and 155mm howitzers, but was not adequate for guns and free rockets. It was clear that, a system of computing was needed which would be more flexible than was possible with an analog system. Ordnance and CONARC agencies cooperated to establish the actual requirements and definitions of problems, and from these Ordnance was able to specify and develop the needed equipment.
Ord. Mono. 1961, GUNNERY, starting page 090

Frankford Arsenal studied the basic ballistic problem for about two years and then the Univac Division of Remington Rand studied the problem along with its associated mathematics. The most desirable approach appeared to be simulation of the flight of the projectile from the tube (launcher) to impact, which is referred to as solving the differential equations of motion of the projectile. After reaching an acceptable mathematical solution, the next major problem was the incorporation of this solution into a device compatible with the size, weight, power maintenance requirements, and operation training imposed by the field artillery.

In November 1956 a conference was held at Frankford Arsenal to present the solution and concept of mechanization. This concept was called the Field Artillery Digital Automatic Computer (FADAC). Military Characteristics were drafted and approved. The-design criteria for a machine were submitted to industry and a contract placed with Autonetics, a division of North American Aviation, Inc., on 20 June 195$ for the design, development and manufacture of FADAC. Target schedules called for acceptance tests by Frankford Arsenal in September 159 of the first prototype FADAC.

The basic considerations and order of priority in arriving at the design of the hardware for FADAC were established as:

  1. Accuracy of solution and reliability of operation.

  2. Ruggedness (ability to withstand adverse climate and field conditions).

  3. Minimal operation (computing time).
    Ord. Mono. 1961, GUNNERY, starting page 091

  4. Ease of operation and operator training.

  5. Ease of maintenance and maintenance personnel training.

  6. Minimum physical size, weight and power consumption (not to exceed 200 lb. in weight and 500 w in power).

  7. Cost.

The FADAC is a solid-state electronic digital computer. It is compact, portable, and rugged. It is approximately 24 x 14 x 34 inches in size and weighs about 200 pounds. It is designed to operate under severe field conditions and storage, and under extreme temperatures of heat and cold. For use by the fire direction center, FADAC requires only the addition of 3-phase 400-cycle power to the fire direction center facilities.

Transistors are used throughout FADAC circuits. Crystal diodes are used for logical gating. The machine is a stored-program, solid-state (no vacuum tubes), electronic digital computer to be used primarily for automatic computing and visual displaying of firing data (gun orders) for Field Artillery weapons, from inputs defining target and weapon locations together with nonstandard conditions of materiel and weather.

It will provide firing data for a battery of weapons. On a one-battery-at-a-time basis, it can provide firing data for mortars, howitzers, guns, and free rockets, firing any ammunition these weapons will use. In emergencies, it can provide data for five similar type batteries, one at a time. By using the memory loading unit, authorized field personnel can make program changes to permit solution of gunnery problems for other weapons in a few minutes time.
Ord. Mono. 1961, GUNNERY, starting page 092

Parts, sub-assemblies, and support equipment are interchangeable with any other FADAC, regardless of weapon or the application to which each may be assigned.

The flexibility of FADAC is demonstrated in the interchangeable control sections, each designed for a particular use. The use of FADAC with different weapons and for different applications is facilitated by changing control sections. For example, a gunnery problem could be solved by FADAC using the control section designed for gunnery, and then the control section could be changed for a counter- battery problem. A removable plug in the control section simplifies such changes. This design is not only a flexible operating feature, but also one that minimizes operator training.

FADAC was designed for high operational dependability and for maintenance to be required only at infrequent intervals. It should be capable of operating under field conditions, without major overhaul, for at least 2,500 hours. The solid-state components are expected to operate for at least 10,000 hours. Errors due to internal malfunctions during a computation will be minimized by internal automatic monitors which aid in detecting such errors.

FADAC was designed to be compatible for transmission purposes with the fieldata family of equipment under development by the Signal Corps as part of the Automatic Data Processing System (AD PS) program. The basic difference between the fieldata code and the teletype system is that the former requires more pulses to transmit a greater amount of in
Ord. Mono. 1961, GUNNERY, starting page 093
formation, i. e., an 8-level instead of a 5-level system. Of the 8 levels, 6 are used for information or intelligence, 1 for parity or to check the transmission of the data, and 1 bit for a control-type function. The FADAC can transmit and receive this 8-level fieldata code.

Input consists of a manual keyboard and various arrangements of paper tape or another FADAC. When all the data, such as target location, powder temperature, gun location, and meteorological data, are entered, depression of a button initiates computation. Gun orders, comprising deflection, quadrant elevation, fuze time, and charge are displayed in decimal form.

Output consists of visual display (called Nixie), another FADAC, battery display, printer, magnetic tape, fieldata equipment, and teletype equipment.

The programming and numerical system of FADAC is straight binary for internal operations, with automatic conversions to other codes for input-output.

In the arithmetic unit the execution time for each instruction is 7.8 microseconds. Its arithmetic mode is parallel by function and serial by bit. Timing is synchronous.

The storage consists of a main magnetic disc of 4,096 word capacity and a high-speed magnetic disc of 32 word capacity. There are 32 channels of 128 words each, of which 24 channels are designated as permanent storage and 8 channels as working storage.
Ord. Mono. 1961, GUNNERY, starting page 094

The extremely high-speed operation of this machine is made possible by a combination of new techniques incorporated in the logic design. While FADAC is basically a serial computer, it performs some functions in parallel, that is, several operations simultaneously. Instruction search, instruction interpretation, number search, and number read are performed at the same time. This overlapping feature, together with minimum access coding, rapid access loops, and multiplication using two bits at a time, results in a machine capable of performing 12,800 additions or subtractions per second, approximately 750 multiplications per second, and 375 divisions per second, including access time for both instructions and numbers.

There are several additional applications of FADAC. One of these is as an ideal replacement for JUKEBOX as a computer for the Redstone Missile System. Frankford Arsenal had developed JUKEBOX before the development of FADAC had started, but, while an excellent computer, it was designed for vehicle mounting and operation where size, weight and power were not of prime importance. FADAC can meet all of the requirements and have the advantage of smaller size and weight.

Other missile systems could also use FADAC. These are: Pershing, Sergeant, Lacrosse, and NIKE-Hercules. In addition to the missile systems FADAC can also be employed in fire planning, survey computations, counter-battery computation, reduction of metro data, and as universal automatic check-out equipment.
Ord. Mono. 1961, GUNNERY, starting page 095

A universal computer for solving all gunnery problems has always seemed to lie in the future. However, continuous study at Frankford Arsenal on increasing the utility and application of FADAC has yielded results which make this computer a candidate for the title "Universal Field Artillery Computer."
The material for this chapter was extracted from Frankford Arsenal Technical Memorandum Report M59-5-1, "FADAC Status Report", by R. Brochman, dated 29 December 1958.

Ord. Mono. 1961, TREE, starting page 096



[click on image to get larger (readable) image - 137 K bytes]

The computer tree shows the evolution of electronic digital computers. The automatic computing and data processing industry is a direct outgrowth of research, sponsored by the U. S. Army Ordnance Corps, which produced the ENIAC, the world's first electronic digital computer. This industry has grown to a multi-billion dollar activity that has penetrated every profession and trade in government, business, industry, and education.

In the accompanying graphical representation of the computer tree the trunk rests on the ENIAC. The serial computers, represented by EDVAC, and the parallel computers, represented by the ORDVAC, are shown as separate limbs. This separation tends to distinguish the business computers on the left limb from the scientific computers on the right limb. The computers which were developed specifically to meet military needs are shown on the center limb. Manufacturers have entered the electronic computer field at different times, shown as various branches. Only university and government sponsored computers are shown along the limbs. The radial distance from the ENIAC is an approximate indication of the year each computer was developed, constructed, or placed in operation.

The impact of computers is tremendous. Our lives are certainly influenced by these automatons, and our very production of consumer and defense goods is indirectly controlled by them. Our national defense is entrusted to them. Our inventories and stock keeping are controlled,
Ord. Mono. 1961, TREE, starting page 097
our records are kept, our bookkeeping is performed by them. Our routine, tedious, and painfully repetitive mental effort is ameliorated by them. We are relieved of arduous mental tasks by them much the same as we were relieved of arduous manual tasks by powered machinery. We are on the threshold of a new era and computing machines are here to stay and play an ever greater part in this era.

The computing machines described in this monograph are merely the beginners. They are the counterparts of the devices of the Howes, the Wrights, the Marconis, the Bells, and the Edisons, although they appear super-modern to us at this time. Nevertheless they are the machines which opened a new frontier in human endeavor with seemingly unlimited capabilities and applications.
For example, research is being conducted at Frankford Arsenal on automatic checkout systems for combat vehicles, missile checkout systems, and automatic diagnostic equipment of a very sophisticated type.

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