The Human Factor in Space Exploration: Soviet and American Approaches
by Valentina Ponomareva
Translated from the Russian by Slava Gerovitch
The initial premises of conceptual approaches toward defining the role and functions of a cosmonaut in the orbit and toward the development of guidance systems of the first manned spacecraft, Vostok and Mercury, were the same for both sides:
1) there was no information about the human capacity to function in spaceflight;
2) there was some positive experience in the development and operation of automatic guidance systems on unmanned spacecraft;
3) the key problem of ensuring the safety of a pilot was closely intertwined with the problem of control.
Therefore, the philosophy of guidance system design in both the Soviet and the American projects was based on the conception of priority of automatic guidance, according to which all regular control procedures were automated, whereas a manual [control] system was reserved for emergency situations. Initially it was desirable to exclude the human being from the control process altogether.
The technical possibilities for the implementation of this conception in the Soviet Union and in the United States were different: the weight of the manned spacecraft Vostok in the orbit was 4.5 tons, while the weight of Mercury was only 1.3-1.8 tons. This factor had a major impact on the parameters of on-board systems and determined the designers' attitude toward the role of humans on board a spacecraft.
Flight safety is traditionally ensured by increasing the reliability of on-board systems and devices. One of the methods of increasing the reliability of manned spacecraft was providing structural and functional redundancy for various systems.
The significant weight of Vostok allowed to back up practically all vitally important systems, except for the braking engine unit (TDU). As a rule, duplicate devices were installed on board, which made it possible to build a sufficiently reliable, fully automated spacecraft. A cosmonaut's function was to monitor on-board systems.
In contrast to Vostok, the small weight of Mercury placed limitations on on-board system redundancy. In many systems, only individual circuits or parts were backed up; as a result, this spacecraft had low reliability. The only way to increase the flight safety was to back up on-board systems with manual controls. Therefore, astronauts were given broad control functions: they could control all on-board systems and change the flight program, even in such potentially risky situations as reaching the orbit and descending from the orbit. In many cases, they had to make control decisions based not on instructions from the Earth, but on current information about rocket parameters and the flight trajectory received on board. During the first flights, because of the significant number of guidance system failures, astronauts were already forced to perform not just experimental, but real control functions. Therefore, the concepts implemented in the guidance systems of the first manned spacecraft in fact turned out to be diametrically opposed.
Besides the technical possibilities determined by the weight delivered by rockets to the orbit, other factors also played a role here, including specific traditions in the field of technology that served as a basis for the first manned spacecraft. In the United States, spacecraft technology developed on the basis of aviation, and the respect for and trust in the pilot, characteristic of aviation, naturally transferred to spacecraft technology. In the Soviet Union, spacecraft technology was based on artillery and rocketry. Rocket scientists never dealt with "a human on board"; for them, the concept of automatic control was much easier to comprehend.
Lessons drawn derived from the Vostok and the Mercury flights shaped further developments in the Soviet and the American manned space programs. The Gemini guidance system gave priority to manual control at various stages, including active phases, rendezvous, and docking. This made it possible to provide reliable functioning of a system with unreliable parts: the insufficient reliability of technology was compensated for by the pilot's skill and competence.
Initially the priority given to automatic control on Vostok was justified. However, the unreserved orientation toward automation and the lack of trust in the cosmonaut persisted through the design phase of the Soyuz, despite the fact that by that time experience with both unmanned spacecraft and manned flights had already demonstrated that this approach was irrational (for example, a failure of the guidance system of Vostok-2, the first test flights of the Soyuz, and especially the orbital flight of V.M. Komarov). This situation can be explained by several factors.
First, the Soyuz was initially designed as part of a lunar space rocket complex
to be assembled on the orbit. Five dockings were required to assemble this complex, and four of them
were to be performed by unmanned spacecraft. The design of an automatic control system for
rendezvous and docking was therefore one of the most important tasks in the development of this complex.
The most important factor that determined the orientation toward automatic control, however, was the general technological trend of the 1960s -- the broad spread of automation of control processes in technological systems of various kinds and purposes. The need for automatic control in rocket and space technology was objective: it was dictated by the technical characteristics of systems and the conditions of their use. In the automation of control processes, including those on board a spacecraft, however, a machine-centered approach prevailed. Many believed that the reliability and efficiency of manned spacecraft were determined entirely by the reliability of technical systems, and conceptualized the automation of control as a complete replacement of human activity with the functioning of technical devices. They also overlooked that the system "human-aircraft" (all the more "human-spacecraft") was not an autonomous one: technical equipment and personnel on the ground also took part in flight control, but their reliability was not being taken into account.
Further experience with the first Soviet test dockings proved that this approach was not justified: automatic systems often failed; rendezvous and docking were not successfully completed in any of the tests. It is precisely in Soviet designers' stubborn efforts to create an automatic control system for approach and docking and to exclude the cosmonaut from the control loop that one must look for the reason of our lagging behind the Americans in the latter half of the 1960s. This is obvious from the comparison between the Soyuz and the Gemini, which were developed practically simultaneously.
This experience has demonstrated that it is impossible to create an absolutely reliable automatic system, and sooner or later people face the necessity to act after equipment fails. The cosmonaut must be constantly prepared to take up the functions of the failed system. But if his functions are limited to monitoring and observation only, then he is effectively excluded from the control process. To be able to join in the control process, he must have strong manual control skills based not only on his experience with ground tests, but also on his performance of control functions in real flight conditions. If the cosmonaut loses such skills because of his passive role, the probability of his choosing and carrying out the right procedure in an emergency would be small. This contradiction is inherent in automatic control systems.
The striving for an absolutely reliable automatic system leads to the creation of (possibly multiple) redundant control loops, but despite the growing complexity, dimensions, and weight of control systems, their area of applicability remains limited. Here another contradiction arises: the one between the current level of reliability and the cost and weight characteristics of a system.
These contradictions, largely characteristic of the initial period in the development of the Soviet manned spacecraft technology, underscored the inefficiency of and the lack of foundation for the machine-centered approach toward the design of manned spacecraft. Eventually designers recognized the leading role of the human being in providing the efficiency and safety of space flights. This gave impulse to the development of semi-automatic control systems.
There is no doubt that, despite a large number of extraordinary and emergency situations, the Gemini and the Apollo programs were completed successfully because in the United States from the very beginning manned spacecraft were designed with orientation toward semi-automatic control systems in which the leading and decisive role was given to astronauts. The Gemini guidance system was already semi-automatic, and the Apollo guidance system was designed in such a way that one astronaut could perform all the operations necessary for the return from any point of the lunar orbit independently from information received from the Earth.
The opposites eventually met: semi-automatic systems constituted the "golden mean" that Soviet and American cosmonautics approached from two opposite directions: the Soviets coming from the automatic systems, and the Americans, one might say, from the manual ones.
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site last updated 27 February 2003 by Slava Gerovitch