Interview with Priss

Computing in the Soviet Space Program











Georgy Priss, photo by Slava Gerovitch

Interview with Georgii Priss

Moscow, May 23, 2002

In 1948 Georgii Priss graduated from the Moscow Aviation Institute and joined the Scientific Research Institute No. 885 (NII-885) of the Ministry of Communications Equipment Industry, led by the Chief Designer of control systems for Soviet rocketry Nikolai Pilyugin. In 1963 NII-885 was transformed into the Scientific Research Institute of Automatics and Instrument-Making (NII AP), and in 1965 it was subordinated to the Ministry of General Machine-Building. In 1978, the Research-and- Production Association of Automatics and Instrument-Making (NPO AP) was created on the basis of the Institute, and in 1994 it was subordinated to the Russian Space Agency. Currently this institution is called the Pilyugin Research-and-Production Center of Automatics and Instrument-Making (NPTs AP). Georgii Priss worked on gyroscopic equipment for the first Soviet rockets, and he was the principal integration engineer during the design of control systems for the R-5 and the R-7 rockets. In 1956 he became Pilyugin's deputy in charge of equipment and the test-and-launch complex. Priss was the principal developer of control systems for the N-1 and the Buran projects. Currently he is the head of Integration Department at NPTs AP.

This interview was conducted and translated from the Russian by Slava Gerovitch.

Gerovitch: When did the idea of using onboard computers in spacecraft control systems first arise? Who suggested it first? What reaction did it provoke? Was it implemented right away?

Priss: By the time this idea emerged, the use of computers had already been widespread. There already existed ground computing systems; some information about the construction of specialized computers for guidance (not just spacecraft guidance) had appeared. Generally speaking, this idea was in the air. Computers had already spread quite widely. It was abundantly clear, especially for the main designer of control systems for spacecraft Nikolai Alekseevich Pilyugin, that computers could be used for solving problems of guidance and that they had many advantages over analog systems, which had been used before. It is hard to tell, to whom the idea of using computers for these problems came first. This idea was conditioned by the achievements of engineering at that time, including the achievements in computing. At the initial stage of the development of computers, it was simply impossible to use them because of the large dimensions and huge energy consumption, by the mid-1960s technology advanced so much - both in terms of basic elements and design techniques - that computers became quite acceptable by these external parameters.

The first onboard computer was installed on a space vehicle sent on Mars. It was part of the control system for spacecraft intended for flight toward Mars in the mid-1960s. Pilyugin decided to use a computer code-named the Argon-11, which had been developed under the chief designer Krutovskikh. A Moscow organization [NIEM, later NICEVT] was designing computers, which by their external parameters were quite suitable for use as part of onboard equipment in spacecraft. And they modified their Argon computer to adapt it to the kind of problems in which Pilyugin was interested, and they code-named this new computer the Argon-11. These problems were by and large problems of guidance. This was the first example.

After that, Pilyugin acted in his specific manner, in his "technical spirit." He had been designing control systems since 1946, and he always adhered to idea of building an autonomous control system that would contain all the elements necessary to fulfill all functions of a control system. This was not an unfounded claim; this was a clear idea. If the development of all elements of a control system is concentrated in the hands of one chief designer, then the control system can truly be optimized. It makes it possible to allocate functions among various parts of the system in the most expedient way in terms of weight, dimensions, energy consumption, and functional decision-making. With this approach, all main, as well as auxiliary, parts of the control system are being developed in one organization.

The application of this approach to the introduction of computers was not the first step that Pilyugin made in the development of an autonomous control system. Shortly before that, about five years earlier, he performed a similar manipulation with a major unit included in the nucleus of a control system - with the gyroscopic unit. Until the end of the 1950s, inertial gyroscopic devices had not been developed in Pilyugin's firm. There were organizations specializing in this; in particular, the organization under the Chief Designer Kuznetsov worked on rocket engineering. He developed gyroscopic devices of various types, including gyroscopic platforms. On one of the rockets developed in second half of the 1950s, Pilyugin included in the structure of the control system a gyroscopic platform developed in Leningrad by the Chief Designer Aref'ev. Having acquired expertise, having obtained results of some tests of this platform on location, Pilyugin himself started the development of gyroscopic platforms. He used the same approach during the introduction of computers into the structure of a control system. The first experiment that I mentioned - the experiment with the Argon - resulted in Pilyugin's decision to start the development and manufacturing of his own computer systems.

For the second phase of the development of the lunar complex N1-L3, Pilyugin decided to design his own onboard computer. At the first phase, the control system included some gyroscopic devices of the Chief Designer Kuznetsov and some analog systems. At the second phase, a totally new control system was created. This new design was implemented in the fourth (last) launch in 1972. The new control system included a gyroscopic platform and a computing system, both designed by Pilyugin. This computer, called the S-530, was based on the Tropa elements. It was intended for calculating all control tasks: guidance, control of the operating logic of the control system's own equipment, and control of the engines and of all other systems in the N1 rocket. There were plans to use the same machine for the control system of the LOK (the lunar orbital ship) and the LK (the lunar ship). Unfortunately, these plans did not come to fruition. The fourth launch did not result in the operation of the LOK or the LK, and therefore there were no experimental results on them. After that, all control systems developed by Pilyugin included computing systems of his own design.

After that came the computer series we named the Bisser: the Bisser-2, the Bisser-3, the Bisser-4, and the Bisser-6. The Bisser-6 represents today's technological level. Of course, these machines developed and improved over time. In particular, the scale of circuit integration increased: first medium-scale integration, then large-scale integration, and now solid-state technology of very large scale integration. This gave us an opportunity to increase the computing resources of the machine, to enhance its memory, to raise its speed.

All these systems were based on the same design principle. Higher reliability was required for the control system in general, and for the computing system in particular. Therefore all these systems were designed with redundancy. They could withstand damage in any single component. They had radial interfaces with various exchange devices, such as gauge converters and operating component converters.

Along with the introduction of onboard computers, computer equipment was being installed at ground testing and launch facilities. Here the same approach was used. While during the development of the first rockets, for example, the N1, the ground facilities used industrial production computers, such as SM-2 (developed at Severodonetsk), later on they switched to ground models of the same onboard computers. Those ground models also had higher reliability. The use of the same type of computers made it easier to establish computer-to-computer communication between the ground and the board, and this approach is still used today. Since the structure of the control system for various space vehicles (with the changes in rocket stages and cargo weights) has evolved significantly during these forty years, a whole multi-computer system is now created, which includes a ground machine and several onboard computers.

Onboard machines may have different purposes, and sometimes this results in the development of specialized computers. For example, some onboard computers provided communication between the central computing system with various onboard systems, in particular, with radio systems or with the system of information and controls display. Such specialized computers could be of different types, they could have different cycles and interface types; nevertheless, with the help of appropriate adapters and coordination devices, integrated systems were successfully created. This principle was implemented not only in Pilyugin's projects. The long-term space station Mir also included a multi-computer control complex developed by specialized organizations, in particular, by the Zelenograd Science Center. It is the same today with the International Space Station: diverse types of computers are included in an integrated computing system.

Gerovitch: Researchers from NICEVT, who developed the Argon-11, say that this computer was installed on board the Zond spacecraft that circled the Moon.

Priss: The Zond is a name for the L-1, which is also our project, but this happened after the flight toward Mars. The Argon-11 was used in other projects too. Speaking of priority, the very first use of this computer was on the spacecraft sent to Mars. The L-1 was launched with the Proton rocket; this project preceded an expedition to the Moon. There was one successful launch of the L-1, which returned to the Earth and landed with escape velocity. If this project were to continue, this computer would have been replaced with the S-530 machine too, but this did not take place.

Gerovitch: In the initial period, when digital computers were introduced, what was seen as their advantages in comparison to analog devices? And their deficiencies? Was it obvious that a transition to this new technology was needed?

Priss: At that stage this was not obvious. First, the basic elements at that time were not sufficiently reliable. Failures were numerous, and therefore a decision to launch could be made only when redundant devices were installed, and there was hope that back-up systems would ensure operation during the flight. During preliminary tests all back-up systems, including the computing system, were being checked, and, as a result, a very large number of elements was tested, and failures occurred more often. For this reason, preparations for the fourth N-1 launch (when an onboard computer was used) proceeded with great difficulty. Various computer elements failed all the time, repairs were being made, and every time it was necessary to justify a move to the next set of tests.

Second, digital computers at that time did not have any advantageous external operational characteristics. That is, they were not much lighter or more energy-efficient than analog systems, and in this sense there were no advantages. One had to learn how to program them, how to test algorithms, how to test software. All this involved great difficulties, and we placed our hopes on future developments. At that time, it was already clear that this technology had good prospects, since the development of new basic elements was under way. It was clear that computers could solve much more problems than they did at the initial stage. Today computers solve all the problems of the logic of control, problems of control of all other systems, not to mention new, advanced guidance systems, which would have been very difficult to achieve with analog devices. Innumerable changes in the shooting angle, in the flight direction, in the trajectory, transitions from one trajectory to another - all this could be solved with analog methods, but it would have been much more difficult. Not to mention the speed of calculation, which is very important for logical tasks. It is less important for guidance tasks; in the latter case, all processes run more slowly, than, say, the processes of starting-up and adjusting the engines. Initially all these problems were solved with analog methods. As computers improved, these tasks were shifted on to them, and thus the functions of the control system were substantially expanded. The use of computers made it possible to eliminate entire types of equipment and subsystems. For example, today a computer-based gyroscopic system, incorporated into the control system, fulfills the task of the initial azimuth aiming of a rocket. All the first rockets of the 1940s, 50s, and early 60s were aimed with the help of an external geodetic system, which somehow had to agree with onboard gyroscopic devices. One had to perform a geodetic locality orientation, one had to install special geodetic devices on the ground, and then, with the help of optical communication devices, one could turn and aim a rocket. The launch installation had to provide means for turning the entire rocket. Later the whole turning operation was transferred from the rocket itself to its gyroscopic system. And when a computer complex was added to the gyroscopic system, the entire system was greatly simplified. Onboard pulse generators, which earlier had been used for temporal tasks, were eliminated; current distributors, which unfolded a "cyclogram," were also eliminated - all this is now done by a computer complex. As a matter of fact, the computer complex and the gyroscopic system are the only essential components of the control system; everything else are just various converters and capacity amplifiers, which control operating components, rocket automatics, engine automatics, and power source, and that's it. Actual control problems, which earlier had been solved by complex devices, are now solved by a computer. Today ground computers prepare the flight task and recalculate it on the fly if necessary. As a matter of fact, all serious functions of the control system are now performed by computers.

Gerovitch: You mentioned that the first computer made at Pilyugin's firm, was built on the Tropa elements, which were not very reliable. When did the transition to integrated circuits occur? Why did it happen?

Priss: The S-530 computer was developed in the late 1960s, and it was used on a spacecraft in 1972. Subsequent machines in the 1970s were based on integrated circuits of various types; the first had medium-scale integration. Here again Pilyugin chose an original approach. At that time, there existed different possibilities for development. In our branch of industry, a new, so-called "open-frame" technology was available: a designer could built the required circuits with open-frame elements - tiny diodes and triodes - and could in practice, not just on paper, implement something similar to medium-scale integration elements. This technology was being used, but not at Pilyugin's firm. He chose an alternative method: he let contracts to various specialized organizations of the Ministry of Electronic Industry. According to his specifications, large-scale integration elements were developed. Pilyugin's firm received finished, well-tested elements, and then assembled the required structures out of those elements. Such was our approach in the 1970s, and it was used not only at Pilyugin's firm. In the late 70s the same approach was used by another firm engaged in the construction of control systems, the Khar'kov Institute [Khartron]. All other design organizations that worked on various elements of a control system also introduced one technology [of integrated circuits] or another. The "scattering" technology was widely used with good results at the Research-and-Production Institute of Measuring Technology, which built telemetry systems, gauge equipment, transformer equipment, and so on. I believe they still use this technology. Our Bisser-6 is built on large-scale integration circuits developed at Minsk or Zelenograd firms.

Gerovitch: The Americans chose integrated circuits as basic elements for the Apollo Guidance Computer in the early 1960s. Was there any study of the American experience? Was it taken into account? Did it have any impact on technical decision-making?

Priss: I am not aware of that. In 1960s NICEVT was engaged in this more deeply than we were, and they possibly knew something. In the past several decades, this information has widely spread. Studies [of foreign equipment] and comparisons with basic elements and capacities of our electronic technology go on all the time. For a long time, the military system of quality testing blocked applications of these [foreign] types of systems or elements. Until the last decade, everything [in the space program] had to pass quality checks by military organizations, and one of the requirements for control systems was the use of domestically manufactured basic elements. In recent years this rule has become non-obligatory. If such [foreign] technology is used, this requires detailed knowledge and understanding of what is being done abroad, and this also requires the creation of domestic analogs to foreign models. To create an analog takes a lot of time. To repeat always means to lag behind.

Gerovitch: Was there any discussion of the American design of a control system for the Apollo?

Priss: I do not recall seeing such materials or publications; I do not think that we had detailed knowledge and understanding of hardware implementation of the Apollo control system. There was some information available about general design solutions and trajectory formation for the Apollo, but this lay outside of the realm of the control system. This information could be of interest only to the lead organization, which was selecting trajectories and strategies for space flight. Despite the substantial openness of the Americans and the availability of endless material on the Shuttle (there was less available on the Apollo), there were almost no publications that would specify hardware design. One could find some general characteristics of the equipment, for example, of a gyroscopic platform or of a computer (speed, memory, and so on), but more substantive information was absent. Perhaps, this information was available somewhere, but it did not reach us, the developers.

Gerovitch: Have there been any attempts to compare American onboard computers with Soviet ones in terms of weight, speed and so on?

Priss: I know that in the early 1980s there were attempts to compare the parameters of systems designed for the Buran and for the Shuttle. And I must say that, based on external parameters, we did not lag behind. Our machine on the Buran was the Bisser-4. In terms of computer performance per se, the parameters of our machine were close to theirs; perhaps, we even had a lead. As for the functional operation, here you have to take into account that the overall structure of our system was different. Speaking of computers, the overall picture was as follows: there were four machines on the Shuttle; they worked in the regular mode on all stages while a spacecraft was reaching an orbit, and they were supplemented with the fifth machine. This fifth machine was of the same type as the other four, but it had different software, different "mathematics." It was used as back-up mathematics in emergency. According the American plan, this back-up mathematics was to be developed by another team, not by those who did mathematics for first four regular machines. The idea was obvious. In the American case, a switch to the back-up system was to be carried out by an astronaut. He had to realize that the first system was not working satisfactorily and to switch manually to the second system. We did not adopt a similar structure for two reasons. There was no other organization that could develop the second mathematics. Even if such an organization could be found, it was still necessary to test and debug their mathematics. Our testing program included an extensive cycle of ground testing and later in-flight testing. The second mathematics would have required additional spending and cause time delays, and we could not afford this.

All these issues were widely debated by technical specialists engaged in the development of the Buran. There were many organizations involved. The lead aviation firm that built the Buran glider and was responsible for landing issues very actively demanded that this question be considered. But eventually we managed to prove the reliability of our regular system. Together with the Rocket-and-Space Corporation Energia, we managed to demonstrate that we foresaw a large number of potential emergencies, and for all these potential emergencies we developed automatic modes of coping with them and rescuing the crew.

For example, the mode of "restoration of control" has been introduced on the Buran for the first time. Let's say, for some unclear reason the control system breaks down on the orbit, all four machines break down, orientation is lost, the spacecraft begins to make strange and unpredictable maneuvers - for example, because of a fault in the power supply. If power is not restored, even the Americans with their fifth machine could do nothing. If power is restored, however, then a special mode would be switched on, which would restore orientation, tell you where you are, restore all processes, and make it possible to rescue the crew and to return them to the Earth.

Nevertheless, the idea of an additional, back-up system was discussed all time, and as a result, it was implemented - not in hardware, but mechanically (a hand controller and so forth) on the model 002 intended for horizontal flight tests. This model of the Buran was tested in the Moscow region with numerous lift-offs and landings. On this model, a manual landing control mechanism was implemented, but it was never used, since the automatics worked without failures.

Comparisons occurred all the time. Not only computer facilities were compared, but also gyroscopic systems. We had the same amount of the information about their gyroscopic devices. Only external parameters of the gyroscopic platform were known, not the internal ones. Here we did not fall behind either. And if entire systems were compared - the control system on the Buran vs. the avionics system on the Shuttle - a competent, correct comparison was impossible, because there was no information anywhere on the specific tasks carried out by the avionics system. Based on its approximate composition and on information from some marginal sources, one could conclude that their avionics system did not carry out all the tasks assigned to our control system. Certainly, the avionics carried out guidance and controlled both automatic and manual modes, but that was all. What else could it do, what equipment was included in the avionics system to carry out other tasks - all this was not at all clear.

The matter is that except for the gyroscopic platform and the computer, whose functions were completely clear, all the other equipment [in the Buran control system] was developed as a complex, that is, it not only controlled operating components, but also carried out other tasks. A computer route - stretching from the cabin, where the computing system was set up, to the exchange devices, which were installed in the tail compartments of the Buran - transmitted not only information necessary for the control of aerodynamic surfaces on landing, but also data required for the control of engines, for the control of small-thrust nozzles, and so on. Therefore, it would be incorrect to compare our route with the route in the Shuttle if it did not serve the same function.

Gerovitch: How was the problem of division of functions between human and machine resolved at different stages? How did the functions of onboard computers evolve?

Priss: If we talk about the first machines, in the case of the Mars probe, it was a fully automatic spacecraft. The N-1 carrier was also automatic system; the orbital ships were supposed to have a pilot and manual controls, but unfortunately, as I said, they did not get a chance to be tested. The only case about which I can say anything is the Buran. Everything that was done by our firm before or after the Buran are automatic systems. In some projects carried out by the Rocket-and-Space Corporation Energia, on orbital stations, some functions were assigned to the crew. I do not know the details. I am not aware whether any such functions related to guidance.

As for the Buran and the lunar ship, they had the so-called "manual guidance contour." The implementation of such contours in the presence of an onboard computer was limited to the following. On the Buran, the manual guidance system, which included a steering wheel, hand controllers, and pedals (like on the Shuttle), had two modes of operation: the landing mode (with problems similar to aircraft landing) and the orbital control mode for docking and undocking. There were different types of controls for these tasks: the aviation controls were the steering wheel and the pedals, while the orbit controls were the hand controllers in three dimensions. The information from these manual controls through converters was entered in the computer. There were no special operating components for manual control; they were the same components that were used in the automatic mode. It would have been ridiculous to put additional ailerons or vertical or horizontal rudders [for manual control].

The main question is this: what algorithms are used to process the information received from manual controls? There are two possibilities here. The first is this: no function is assigned to the computer, except for simple transmission, that is, whatever the pilot has done is transmitted to operating components one-for-one. The second variant is to limit his possibilities. Say, not to let him give a silly instruction or an untimely instruction. The latter variant is in fact chosen. There are some restrictions on the pilot's actions.

Next, the pilot should receive some information. During docking, he must see a picture, he must be able to aim correctly. Here too there are several possibilities. First, he can make observations through separate optical devices (for example, on the Buran, there was a pilot's sight and some other optics through which he could look independently from the machine). Second, he should receive information about the condition of onboard equipment, at landing you must show him the landing field, he must have arrow indicators, as in an automobile or on an aircraft. The latter task [of information display] was entrusted to the computing machine, since this information came from inertial system gauges, or from systems of air-velocity parameters, or from radio systems, and it fed into the machine. The machine needed this information for automatic control. But besides this use of information in the machine, it was also displayed for the pilot to see.

The Americans assigned a greater role to the pilot than we did, and the pilot had more opportunities to see a situation. In the Shuttle, for example, he even had some indicator panels above his head. In our case, the situation was a bit different. It was decided in the beginning that we would design a shuttle that would be able to work both in the automatic and in the manual mode. Therefore, everything had to be automated for the automatic mode. And so it was done, for example, automatic landing was implemented. Then, when this implementation was combined with manual control, naturally, an idea arose: here everything is already in place, so the pilot's role may be limited. Indeed, the machine thinks faster, it executes commands and evaluates the situation faster. The Americans faced a different situation, and for this reason they assigned wider functions to the pilot.

On a lunar complex we had manual control, because landing on the Moon was to be performed manually. There were special controls made, information display units, and so on. All this was done through the machine, in the same way.

Gerovitch: Was the control system for the lunar ship completed?

Priss: It was completed; it passed almost the entire cycle of testing on the ground. It was ready for operation.

Gerovitch: Let's come back to the Buran. If the computer determined that the pilot was making a potentially dangerous move, what happened in this case? Would it cancel this action?

Priss: No, the computer simply limited the pilot.

Gerovitch: For example, the pilot could not make a turn by more than a certain number of degrees, right?

Priss: He could not make it greater than the number that the machine accepted.

Gerovitch: That is, the computer physically limited possible changes?

Priss: Yes, it did.

Gerovitch: Was there anything the pilot could do to override it?

Priss: He could not pass the preset limits. He could operate only within the limits set by the machine, or, to be more exact, by the developer of the algorithm. He could do another thing. He could manually switch to a different control mode. All the modes were automated and had a specific algorithm (that is, a program). If he had serious reasons, he could, for example, cancel docking. Say, he is on a shuttle which is docking with a station in the active mode, and he receives information - either from the station, or from the ground - that for some reason the docking cannot be performed, while the docking has already began. He can manually cancel this mode and switch to another. He can choose a control mode. This switch could be performed automatically by criteria that the machine understands, or by command from the Earth, or by the cosmonaut.

Gerovitch: That is, he could only switch from one mode to another, but could not disconnect the computer completely?

Priss: In principle he could disconnect it, but this did not make any sense.

Gerovitch: Who was doing programming for the onboard machine on the Buran?

Priss: This is a very broad issue. If we talk about small projects, such as the Mars or the N-1 (in terms of computing and programming tasks, those automatic projects from today's perspective were not so big), then the development of mathematics was done as follows. There are three circles of programs for the machine. The first circle is a set of tools for the machine itself. The machine must have an operating system, which directs the computing process: how to address various types of memory and how to receive and send out external information; there are also channel programs, input-output programs, and so on. All this mathematics does not depend on the task carried out by the machine. It must control the execution of any task assigned to the machine. A special group of programmers is assigned to create this set of tools. They are "pure" programmers who must know the computer, its system of the instructions, and the chosen interfaces very well. One must add to this set also the algorithms of flight mission input, of flight mission control, and of dialogue with other machines (if this is multi-machine system, then some computers must be active, and some passive, and so on). This set of programs is specific for each computer. If I switch this machine to a different set of tasks, this set of programs will remain the same.

The second circle of tasks are guidance tasks. This includes the processing of information from various sources (inertial systems, optical systems, and radio systems). Then the computer solves the guidance problem, taking into account various dynamic characteristics of the object of control: inertial and weight characteristics of the spacecraft, the characteristics of various operating components, dynamics requirements, and limitations imposed by the rocket design (for example, there are limitations on turn angles and on rotation speeds). The programs that we include under the guidance rubric, as a rule, are developed by programmers from the main organization that designs the control system. If we design the control system, then these are our programmers.

Gerovitch: Are these programmers trained as engineers? Do they understand the logic of the control system well?

Priss: Certainly. They design it! They design guidance algorithms. For example, one can direct a flight along a rigid trajectory, in which case any deviation from this trajectory is detected by sensors, and then the spacecraft must return to the straight path that you have laid out beforehand. This is yesterday's technology; nobody does this today. Today science has developed the technique of terminal control: it does not matter how I fly; what is important is that I arrive in the given final destination with the given speed, angular parameters, and so on. It means that I don't have to force the product, to twist it this way and that; I save fuel and power; I don't have to make an extra durable spacecraft that would resisted the wind. If the wind sweeps it away, let it do it; you can correct for this later. This is the meaning of terminal control.

Programming is done by people who know, understand, and can do all of this. Besides, they know the computer and its operating system; they know the capacities of the machine. They try to solve problems without spending much memory or computer time, that is, they try to make an optimal use of its resources. As initial data, they use specific trajectory requirements set by the developers.

There are some exceptions to this approach. For example, V.A. Trapeznikov's institute, that is, the Institute of Automation and Remote Control [currently the Institute of Control Problems], develops for the large rocket complexes algorithms of calculation of complex dynamic processes, in particular, algorithms related to the regulation of component ratio in the fuel for rocket engines. This line of research was started by the academician B.N. Petrov. They begin the development of this type of algorithms and then transfer their development to our specialists, who link these algorithms with their own algorithms that also relate to motion. For example, if the engine is adjusted, then the velocities also change, and these algorithms must be somehow coordinated.

The third group of programmers resolves issues related to the logic of control of all other processes, other onboard systems. Such issues also have two parts. Say, a developer of the control system formulates an algorithm of engine control and requirements for separation. The stages must be separated under specific strength conditions and so forth. Here contact with the second group of programmers is needed. For example, it is necessary to turn off the engine when certain velocity is reached. Velocity is measured by specialists in dynamics, but they do not know how to turn off the engine. This is not a simple instruction but a whole cyclogram. These specialists only issue a command to turn off the engine, while the entire cyclogram - all subsequent operations with the engine, with separation, and so on - is done by "complex" programmers, who know little about motion and dynamics, but who understand the logic of operation of all system.

It was precisely at this stage that the developers of the Buran faced incredible problems caused by the very volume of the task. There were the total of 52 onboard systems that were subject to automatic control by a computing system. Some of them were controlled by the control system, and some were not. Take, for example, the telemetry system. There is a chief designer of this system, who designs this equipment and knows how it should work. The telemetry must be turned on and off, its mode may have to be changed, and so on. Only he knows the algorithm of working with this system, but it is the computer that will actually be operating it. This means that there must be a program for the telemetry system. To find a place for this program and to agree upon its interaction with other programs is a task of "complex" programmers working for us. Then a question arises: who will write this specific program? On a simpler type of spacecraft when we faced similar problems but they were not so numerous, the following method was used. The developer of this system draws the cyclogram in a usual way, without translating it into a mathematical program, and then our "complex" programmers translate it into a program. This way there always were some discrepancies, misunderstanding, and errors, and several iterations were needed to correct and debug it. It was not feasible to use the same method on the Buran; in this case, the design stage would have taken 20 more years. For this reason, high-level programming languages were created that enabled the developer of a system to write up an algorithm without knowing any characteristics of the computer, its system of instructions, or any other internal requirements of the machine. He would write an algorithm in a simple, clear language, and then a programmer on the basis of this initial material would write a program for the machine. During the design of the Buran, the translation of this algorithm into a program was done mainly by hand with the help of some semi-automatic tools. Today new systems exist that can process this information and produce a complete program as a result. After that, this program, of course, has to be tested: first on autonomous simulators, and then on complex simulators. I have included in my article a list of organizations involved in this project as part of the Buran program [G.M. Priss, "Nekotorye aspekty razrabotki sistemy upravleniia 'Burana'," Aviakosmicheskaia tekhnika i tekhnologiia, no. 3 (1999): 35-42.].

Gerovitch: Did the Institute of Applied Mathematics take part in this project?

Priss: Yes, they participated most actively. The academician A.N. Tikhonov supervised this project; M.R. Shura-Bura was among his top aides. They worked together with us, since our specialists knew the specific characteristics of the computers. They created the PROL language for programming this type of tasks - not guidance problems, but logical problems.

Gerovitch: Could you tell more about the Bisser computers?

Priss: The Bisser-1 did not develop beyond the design phase. The Bisser-2 was designed in the late 1970s-early 80s, and until recently it was installed on Zenith-2 rockets. This machine was used quite widely and was installed on many different models. The development of the Bisser-3 went in parallel with the work on the Bisser-4 for the Buran. These two machines were principally different. The Bisser-3 was also widely used. Today it is installed on the Zenith-3, on the acceleration module of the Sea Launch; it flew on the acceleration module of the of the Frigate (there have been four joint launches with the French).

The Bisser-4 stayed apart from these models; it was an original machine. It was used only on the Buran. Its main feature was that each channel was structurally autonomous, that is, each channel was a separate machine. It was possible to combine as many of them as necessary. There were four machines in one complex and four machines in the other complex, and the majorization of the output was carried out by a special logic switchboard outside of these machines.

Gerovitch: Would it have been possible to install five machines?

Priss: Yes, it would have. The only thing that would have to be changed is the logic switchboard so that it could process information from five sources. It would have been also possible to install only three machines. Our choice of this logic was influenced by the American structure: they have a fifth machine, and it works according to its own program. But since it uses a different program, it is impossible to apply the majority principle. This principle requires a comparison of similar information from all sources and suggests using those outputs that are identical. For example, out of three machines two results must be identical; if one machine deviates, I simply stop paying any attention to it and take information from the other two. Out of four machines three results must be identical. It is possible to build more complex logic: to compare pair by pair and so forth. But if the fifth machine has its own program, it cannot be part of this process. Before the final output is given, all the computers of the Bisser-4 complex exchange information among themselves. This way the reliability of such a system sharply increases.

In all current models the Bisser-3 is used. The next step is the Bisser-6 machine on integrated circuits of higher integration (newly developed by organizations in Minsk and Zelenograd). This computer has improved communication with external users, a higher speed, and a different type of memory. So far this machine has been used in ground testing complexes. It is hardware- and software-compatible with the Bisser-3 (with small corrections). When we decide that it is completely tested, it can be installed on all models where currently the Bisser-3 is used. The Bisser-6 is cheaper, its elements are smaller, it is lighter and more power-efficient. It is our next step.

Gerovitch: Does the Bisser-6 complex operate on the same principle as the Bisser-3, that is, its computers are integrated, rather than autonomous?

Priss: Yes, that's right.

Gerovitch: Let's go back to the Bisser-4. Say, one of four machines gives a result that differs from the others. Would this machine be turned off completely, or only its result during this one cycle would be discarded?

Priss: No, its result would be discarded only during this cycle. This could be a sporadic failure, and it could work normally in the future.

Gerovitch: Would this machine be included in further operation on a par with the others?

Priss: Yes, certainly.

Gerovitch: Were there any computer malfunctions during the Buran launch?

Priss: On the Buran there was not a single malfunction - not only in the computer, but in the entire control system. The entire preparation cycle was repeated twice. The first launch of the rocket carrier Energia with the Buran was scheduled for November 30, 1988. But they called it off right on the launching site. The system did not take off because the mechanism of retraction of targeting optical devices on the carrier (I already talked about it) did not work.

Today no optical systems are used during launches. Our gyroscopic platforms have a gyro-compass mode, that is, the platform itself can determine the cardinal points; there is no need for geodesic or optical devices. Wherever the platform is, it will determine its location and direction of movement. The Americans did not have that, and they had to aim precisely. The matter is that the Americans do not have a separate rocket. They have solid-fuel accelerator engines and a tank that works with the Shuttle engine. Therefore, a control system - the "brain" - is installed only on the Shuttle. They had three gyroscopic platforms, and it was necessary to aim them. For this purpose they used a ground optical system. But they were able to put their platform on the left board of the cabin and somehow managed to establish an optical connection from the Earth to aim correctly.

We have not been able to place our gyroscopic devices on the Buran in a similar way. This happened not because our platform is bigger; in fact, it is rather smaller than the American one. The matter is that the requirements for automatic operations - including such operations on the orbit as docking, determining the location, and so on - resulted in expanding the structure of the control system with a whole complex of automatic optical devices: stellar-solar gauges, navigation antennas, and so forth. It was necessary to be able to adjust their position with relation to the platform. All our gyroscopic devices were installed not in the front, but behind the cabin, in the cargo compartment. Three platforms (a triple-redundancy system) and all optical devices were put on a very powerful adjusting plate. But the cargo compartment is closed! It opens only on the orbit. And they were not able to make a slit to reach these devices. At that time, we did not have platforms with the gyro-compass mode. We needed an optical orientation to set the initial azimuth, but this could not be done. Therefore, we had to do optical orientation for the platform that stood on the rocket.

Our Energia rocket had an independent control system (which the Americans did not have), and therefore the Energia could be launched without the Buran. Its gyroscopic system had to be aimed correctly. A ground optical station aimed it with the help of special optical devices. It was necessary to transfer two beams to each platform, and there were three platforms in total. On the N-1 we solved the same problem. A top optical aiming device is set up, which is needed only on the ground. It is not needed in flight, since you have already aimed and took off. On the N-1 we simply dropped this device; it fell on the ground and shattered. It could be used only once. On the Energia we decided this was a waste, and we looked for a way to preserve these devices. On the N-1 this would not have been possible: it was too high, the service trusses moved away, and there was nothing that could pick up those devices. And now such an opportunity arose. The Energia was much lower, smaller than the N-1. There was a special truss construction made that supported those three devices. It was joined to the rocket, and at a launch it was to be separated automatically (special pyrotechnic locks were made) and moved away from the rocket.

On the first launch on November 30, 1988, this system did not work. More precisely, the separation took place, but there was a tilt, and a confirmation that it worked did not come through. The launch was aborted. But up to that moment all preparations on board passed without a single flaw. The fuel tanks were emptied, and another attempt was scheduled in two weeks, for December 15. We have repeated the entire routine. This time this thing worked and moved away, we reached the orbit, made two turn circuits, and then the process of deceleration and descent began. At this stage, there were other difficulties. We landed in the automatic mode. There was a side wind of 17 meters per second, but we landed within three meters of the center of the landing strip. Not a single flaw there was. Neither at the take-off, nor during the ascent, nor during the flight.

Gerovitch: What was Sergei Korolev's opinion on the prospects of using onboard computers? Some say that he looked for contacts with various organizations, in particular, with the design bureau of Philip Staros and Joseph Berg in Leningrad, where mini-computers were being developed in the early 1960s. Others contend that he was skeptical about this. Do you know what his opinion was? To what extent could this opinion influence Pilyugin's decisions?

Priss: Pilyugin always was on very terms with [Sergei Pavlovich] Korolev. They were friends, and therefore Pilyugin always listened to Sergei Pavlovich's opinion. They never disagreed on principal issues. They had some disagreements on specific questions. They often had quite harsh and vigorous disputes. But Korolev died in 1966. It was just the beginning. I was pretty close to the these circles, and I never heard of Sergei Pavlovich's negative attitude toward computing.

I am not aware of the contacts that you mentioned. I can only make the following assumption. At that time in Sergei Pavlovich's organization there already formed a large division under the direction of Boris Evseevich Chertok. They too were engaged in designing control systems. This happened because when they began the development of manned spacecraft (on satellites, it is a different matter, since satellites are quite passive from the point of view of control), Sergei Pavlovich offered Nikolai Alekseevich to make a control system for them. Before that, nobody was making control systems. True, in the late 1950s there already existed a firm in Khar'kov which was doing for the chief designer Mikhail Yangel the same thing as we did. In the same period, a special design bureau under the direction of Nikolai Semikhatov [currently the Research-and-Production Association Avtomatika] was set up in Sverdlovsk; they began doing the same for navy complexes. And the directors of both firms were former employees of our organization.

The time when Sergei Pavlovich offered Nikolai Alekseevich to participate in this project was a very difficult period for us in terms of work load and also personal relations. Gagarin flew in 1961. His spacecraft was a primitive device. He landed on a parachute; the spacecraft had almost nothing to do. Korolev envisioned a whole series of advanced piloted spacecraft, and later this was indeed implemented. At that very moment [the chief designer] Vladimir Chelomey began working on spacecraft, and Pilyugin was assigned some projects for him. Thus, we did work for Korolev and for Yangel, and then Chelomey' projects were added. Pilyugin realized that he could not carry out all these projects at once, and he refused Korolev's offer.

Sergei Pavlovich began working on this problem in his own organization. Boris Chertok, Boris Raushenbakh, and others were involved. Their approach had its own specificity. Apparently, they coped well, and this division still exists and solves these problems with good results, which are in no way inferior to what we could do. The difference in approach is another matter. We work by the method I described earlier - we concentrate everything under one roof - while they are engaged, as a matter of fact, in compilation. They buy a machine, they buy gyroscopic devices, they buy optical equipment, and so on. We try to do everything ourselves, except for optical devices. Apparently they realized, just as we did, that it was necessity to use computer technology. I never heard anyone, including Sergei Pavlovich, speaking against it. He was not in this sense conservative, and I can hardly believe that he could take a negative attitude.

Gerovitch: Who designed the Mars spacecraft on which the Argon-11 was installed?

Priss: Sergei Pavlovich.

Gerovitch: This means that this installation must have had his approval. The decision to install an onboard computer could not have escaped his attention, true?

Priss: Both he and Chertok understood all these problems perfectly well. Later on Korolev transferred all automatic spacecraft projects - the Moon, the Mars, and the Venus - to the chief designer Georgii Babakin. Babakin too was a very progressive designer, and for him there was no question [whether to use computer technology]. The first successes of the lunar program - landing on the Moon and everything else - were achieved with Babakin's spacecraft. Currently Babakin's Phobos project continues, but it is not very successful. Now they are planning the Mars-express project. It is difficult to imagine now that someone could have objected [to the use of computer technology].

Gerovitch: By the mid-1960s, analog technology was improved to a certain level of reliability, and new digital technology could raise doubts. I often hear that Korolev insisted that it was necessary to rely on well-tested technologies, to choose simple solutions without unnecessary complications.

Priss: This principle always holds true. Everyone supports it. In this sense the West is more conservative than Russian developers. We now often face this problem. Today negotiations are going on with Boeing, which has created the Sea Launch company, about further steps, in particular, to work not just on sea launch, but also on ground launch. We put forward various proposals, for example, to switch to the Bisser-6. They reply: "No, no need for that. The old computer has already flown, and the new one has not." We say: "It will be well tested by the deadline!" They reply: "No, no need for that." I believe, they have the rule that all new models must have no less than 70 % of old equipment. But even in the remaining 30 % one could include a computer.

Gerovitch: Could you tell me about yourself: when did you join Pilyugin's firm, what did you work on?

Priss: I joined the firm in January 1948. The firm was organized by the well-known order of May 13, 1946, signed by Stalin. It was a general order to start the development of rocket weaponry. It contained specific assignments to various ministries. For example, it would read "on the basis of such-and-such factory, create an organization that will be doing this and that." A similar assignment was given to the Ministry of Electrical Technology, in which there was a factory that produced communications equipment: telephone sets, telephone exchange switchboards, and so forth; it was located on Aviamotornaya. On the basis of that factory, our organization was created. It had two assignments: the creation of autonomous control systems and the creation of radio systems. Therefore, there were two chief designers in our organization: N.A. Pilyugin and Mikhail Sergeevich Ryazansky. Pilyugin was the chief designer of autonomous systems, and Ryazansky worked on radio systems. All of them - Pilyugin, Korolev, [Valentin] Glushko - in 1945, after the Victory, were sent to Germany, where they studied captured rocket technology. There were doubts and debates in the Soviet Union: whom to assign the production of this rocket technology? The Air Force refused; the Ministry of Ammunition also refused. In the end Nikolai Dmitrievich Ustinov understood the value of this technology - he was then the Minister of Defense Industry - and he took up this job. Then Stalin's order appeared, and all ministries received specific assignments.

The people who had worked at that factory now switched to rocket engineering. They were telephony specialists evacuated from Leningrad, from the Krasnaya Zarya factory. They were very competent in their work. They were inventors, who in the early days of telephone engineering were engaged in the construction of telephone systems - not only telephone sets, but also stations. The captured German rocket technology was based on relay circuits. Analog control devices were made with vacuum tubes. There were also some gyroscopic devices. The Germans had only five devices in total.

Pilyugin, who had studied this technology in Germany, was appointed to supervise these relay specialists. He had graduated from the Moscow Advanced Engineering School (MVTU). In 1947, when we came, he had about 70 people. Back in 1946 he had just 30. In 1947 Pilyugin was a member of the graduation examining board at the Moscow Aviation Institute. He attended graduation project defenses and listened to these projects. He used the following method: he talked to those students who came not to defend their own project but to listen to another project defense. They were about to defend their own projects, and they came just to listen. Based on their graduation projects, Pilyugin selected the first group of six students and hired them.

I was in the second group. I met Pilyugin at the end of December 1947, when he attended project defenses of the first group. We still had about six months to do our own projects. He told us: "Come to me, and do your projects with me." We indeed came. He did tell us what we would be working on - there was secrecy all over - he just said: "Here are such and such research topics. If you want, I can hire you as technicians while you do your projects." We did not know any details. We thought, why not? What's the difference where to do our projects? So we agreed. We came in January, and we defended in June-July 1948, and all stayed with him. There was also the third group, in 1950-51. Stalin's order was all-inclusive: it had a provision for the organization of special student training and student job placement in the centers of rocket industry.

Pilyugin assigned topics by intuition, as I understand, and I got integration. There were six of us, and the majority began working on specific devices, while I was assigned to the integration laboratory. I defended my project, and since then I have been working on integration.

The Soviet rocket industry had a unique organizational structure. If you take aviation industry, you won't find there a "chief designer" of the control system for a particular aircraft. There is no such position, even though there are control systems, and they also have gyroscopic devices and computing devices, and their tasks are as complex as ours, and maybe even more. In aviation industry, the chief aircraft designer - Aleksandr Yakovlev or Andrei Tupolev - used the compilation method. They always had " equipment groups." Many of our collegemates, who graduated the same year, before, or after, were placed in so-called "equipment brigades." What they were doing was to visit various aviation firms that produced autopilots, electric transformers, radio equipment, and so on, and searched for the equipment they needed. At best they could order equipment, but usually they had to take whatever they were given, and then they compiled these pieces and created a control system. By contrast, in rocket industry the chief designer of control systems [Pilyugin] was appointed at the very beginning. Next to him was the chief designer of gyroscopic devices, Viktor Ivanovich Kuznetsov. A chief designer of radio systems also was appointed. The Council of Chief Designers was created. It also included Sergei Pavlovich Korolev, the engine designer Valentin Glushko, and the ground complex designer Vladimir Barmin. That's six people in total, the entire Council. They resolved all the technical questions.

What is integration? All these individual devices must be put together to make a unified cyclogram; there must be some equipment that would integrate everything. It was necessary, for example, to integrate various parts of the power system - the accumulator battery storage and the converters into other kinds of energy (gyroscopes, for instance, require alternating current). It was necessary to operate the engines and all onboard systems, to make a cyclogram of pre-launch preparation, and so on. It is the control system that turns on the engines at lift-off.

I graduated from the Faculty of Equipment of the Moscow Aviation Institute (MAI). MAI is distinguished by its broad education. They taught us oxygen equipment, hydraulic equipment, radio equipment, and other kinds of devices. I was finishing college after the war, and at that time and during war a lot of new kinds of equipment appeared in Russia: American airplanes on lend-lease contracts, captured German equipment, and alike. We began studying all this. In the Faculty of Equipment and Instrument Construction, the department of Viktor Naumovich Mil'shtein organized a group to study new equipment during an additional, eleventh semester. I got into this group. My major in the diploma read "mechanical engineer with specialization in gyroscopic devices." For me, the idea of integration was clear; I knew where every kind of equipment went.

Since then I have been doing integration. I was the principal integration engineer on the R-7 rocket, and before that on the R-5. I worked also on the very first rockets, the R-1 and the R-2, but as an ordinary engineer, not as the principal. I was the principal developer on the N-1 and on the Buran. Since 1956, I have been Pilyugin's deputy in charge of equipment and the test-and-launch complex. Pilyugin since died; his former post is no longer call the Chief Designer, but the General Designer, and I am still the deputy. Now I am the head of Integration Department. We currently work on a joint project with Australia on the Aurora space-rocket system. We have an Integration Division, which includes several departments. Other departments work on integration in other projects. Someone is still working on a project, and someone else is finishing, and he gets another project. For other projects I work on the problems of stabilization routes, of communication with radio operators, and so forth (the entire control system is divided into separate functional routes).

There was a period in the 1960s when I was the head of the entire Integration Division. In 1963 we moved from Aviamotornaya to the Southwest district, and after 1963 I was the head of this division and was working on the UR-500, on the Proton, and on the N-1. Almost 600 people worked in that division.

Gerovitch: Did you attend any launches?

Priss: Yes, of course. I attended all the launches of the N-1 and the first, unsuccessful attempt to launch the Buran. Then I left for Moscow and did not return for the second attempt, but stayed in the Flight Control Center. I was curious to see the role played by the Center. I had already been to the launch site, and those who see the launch do not see the landing. Those who sit in the bunker during the launch cannot be at the landing complex. And in the Center you can see everything and know everything.

Gerovitch: Thank you very much for the interview.

site last updated 16 December 2002 by Slava Gerovitch