This report reviews the most important episodes in the history of designing the self-propelled automatic chassis of the first mobile extraterrestrial vehicle in the world, Lunokhod-1. The review considers the issues in designing moon rovers, their essential features, and the particular construction properties of their systems, mechanisms, units, and assemblies. It presents the results of exploiting the chassis of Lunokhod-1 and Lunokhod-2. Analysis of the approaches utilized and engineering solutions reveals their value as well as the consequences of certain defects.
The aim of this article is to reconstruct the most important events in the history of the creation of a unique technical system, namely, the self-propelled automatic chassis of Lunokhod-1.
In the American and Soviet missions to the Moon in 1969 and in the 1970s, the use of moving vehicles in these expeditions was far ahead of its time and continues to be relevant in the 21st century. This relevance is evidenced by the successful operation of US Mars rovers of various classes and purposes as well as the involvement of an increasing number of countries and international organizations in surface and environment study by contact methods.
To date, only the Chinese lunar mobile device, Yutu, in which the wheel design shows the effect of the successful operation of the Lunokhod-1 chassis, managed to leave its track on the surface of the Moon in the new century. Scientists and engineers show great interest in this task. One example is the international youth competition of X-Price Company for the best results in the realization of a lunar mission.
The first serious publication about the design and results of the operation of Lunokhod-1 and Luna-17 was the book [1,2] published under the editorship of the Vice President of the Academy of Sciences of the USSR, Academician A. P. Vinogradov. It was the first precedent of the open publication of technical details on the new space technology in the USSR. The second volume of the book [3], which was edited by corresponding member V. L. Barsukova, was published in 1973. Both editions, in which all systems of Lunokhod-1 are highlighted and the results of investigations of its onboard scientific instruments and equipment are provided, are well known in countries interested in lunar exploration.
However, the authors did not disclose the creation details, the scientific and industrial cooperation, and the managers and leading specialists of the many groups involved in the implementation of one of the greatest technological achievements of the 20th century. All of the participating individuals, including the chief designer of Luna-17 and Lunokhod-1, G. N. Babakin, and the chief designer of Lunokhod-1’s self-propelled chassis, A. L. Kemurdjian, are featured in the list of authors of this book and in the reports presented in international conferences under their pseudonyms. Only the employees of the institutes of the Academy of Sciences of the USSR or employees of closed institutions conditionally assigned to the staff of these institutes could be published under their names.
The subsequent editions, in which various aspects of the design and operation of mobile lunar laboratories were revealed, were kept within the frame of scientific and technical literature. If in the first of them [4] the content was about specific objects, the authors of subsequent editions set the topic range more broadly, formulating generalizations for wheeled and then wheeled-walking planetary rovers with different characteristics and operating conditions [5–8]. In all of these editions, no information about the authors was provided even though they were already allowed to publish under their own names.
Information breakthrough occurred in the 1990s. Writers were then allowed to publish their analytical materials, including historical analyses of space research. The first publication of this kind about planetary rovers was made on the initiative and with the participation of A. L. Kemurdjian [9–11]. He understood well that public discussion of national priorities was a necessary condition for the entrance of Russian enterprises to the international market of space products and services.
Such an understanding can be seen in various types of publications devoted to the history and scientific and technical developments of the creation of a new space technology by Russian defense enterprises. Often, these publications were dedicated to anniversaries and events [12–16]. These publications were met by the international community with much interest; their responses resonated in the new century [17].
In the 21st century, publications on Lunokhod-1 became more open and widespread. They dealt with the historical details of Lunokhod-1, the interaction of defense enterprises, the role of leaders and experts in the organization of work, and the generation of technical ideas [18–33]. However, most of these works were published in English.
Unfortunately, the author is not sufficiently familiar with the detailed analytical publications of foreign authors on Lunokhod-1 [34]. This article was written specifically for publication in the Proceedings of 2015 IFToMM Workshop on History of Mechanism and Machine Science. In contrast to the abovementioned works, the current one seeks to consistently express all the important episodes of the history of the creation of the self-propelled chassis of Lunokhod-1 in VNII-100 to provide insights into scientific and technical cooperation and to call all the managers and leading specialists who influenced the technical configuration of this crucial system.
The specialists of the Special Design Bureau No. 1 (Osoboe Konstruktorskoe Byuro: OKB-1) were those who initiated the implementation of the lunar rover idea in the 1950s [18]. The enterprise, known now as Rocket and Space Corporation (Raketno-Kosmicheskaya Korporatsiya: RKK) “Energia”, was headed by S. P. Korolev since its establishment (1946) and until the day of his death (1966) [12].
The task was formulated at the national level in Resolution 715-296 of the Central Committee of the Communist Party of the USSR on 26th June, 1960 [35]. Creation of the self-propelled chassis of the lunar rover was commissioned by this resolution to the Moscow Science Motor and Tractor Institute (NATI) known nowadays as Science and Research Tractor Institute.
However, cooperation between OKB-1 and NATI proved to be unsustainable, and in May of 1963, the State Committee for Automotive and Agricultural Machine-building informed the State Committee for Defense Technology (GKOT) by letter about the request of NATI to call off this commission from the institute.
In this situation, both the chairman of GKOT, S. A. Zverev, and the curator of the defense industry on the part of the ruling party, D. F. Ustinov, requested S. P. Korolev to address the Science and Research Institute VNII-100, which was also a structural part of GKOT similar to OKB-1.
VNII-100, now called the All-Russia Research and Development Institute of Transport Machine-building (Vserossiyskyi Nauchno-Issledovatelskyi Institut Transportnogo Mashinostroeniya: VNIITransmash) , was established in 1949 by the Resolution of the Council of Ministers of the USSR in the Leningrad sub-office of the pilot plant No. 100 of the legendary Chelyabinsk Tankograd; it was established as an integrated research and development center for military track-type machines [14].
Initially, the institute was located in the territory of Kirovsky Zavod. However, in the end of 1950, it was assigned a space of more than 2000 hm2 near Gorelovo settlement, where the institute finally moved to in 1962 when its director was V. S. Starovoitov (Fig. 1 [24]). In July of 1963, he employed OKB-1 specialist V. P. Zaytsev, who presented him a proposal by S. P. Korolev to create the lunar rover.
 | Fig.1 V. S. Starovoitov (1919–2001) [24] |
V. S. Starovoitov [36] accepted the unusual proposal. Organization of work, promotion of the decisions made by the Head Department (Glavnoe Upravlenie: GU) No. 12 of the Ministry of the Defense Industry and leading experts on tank engineering, and continued support for the space subject in VNII-100 are personal achievements of the director. In September 1963, he initiated the commission of the head of the Head Department (GU) No. 12 of the State Committee for Defense Technology of the USSR to begin the creation of the lunar rover [15,19].
The director assembled a team that could solve new challenges and selected its leader. A. L. Kemurdjian was appointed as the head of the Department of New Principles of Movement (Department 25) [20] (Fig. 2). Previously, this team had conducted a study on the creation of armored hovercraft vehicles and provided expert advice.
 | Fig.2 A. L. Kemurdjian (1921–2003) [24] |
As discovered in the beginning of the new century [21,22], it was not the first proposal of the chief designer of OKB-1. According to the science secretary of the Research and Development Council (NTS) of the tank-designing department of Leningrad Kirovsky Zavod (LKZ) A. K. Dzvyago, a similar proposal was made in 1959 in a letter to Zh. Ya. Kotin, who was the head of this collective and later the first director of VNII-100.
Zh. Ya. Kotin ordered the study of the issue and took part in the discussion of the results in a special meeting of NTS, which took place in 1961. However, the chief designer of Soviet heavy tanks refused to further participate in the project.
This episode had no influence on the further development of the lunar rover, and new designers did not even know about it. However, the repeated appeals of S. P. Korolev to tank and tractor builders who were creators of transport vehicles with high cross-country ability appeared to be important. Apparently, this particular property of the future lunar rover had a high value to the chief designer of space systems. He met like-minded fellows in VNII-100 (Fig. 3) [37].
 | Fig.3 Leading specialists of space studies, 1971 [37](Left to right) top row: N. E. Bechvay, B. V. Gladkih, V. M. Tarasov, V. V. Gromov, A. I. Egorov, V. V. Grinev, V. Lashkov, V. N. Petriga and G. N. Korepanov; middle row: V. I. Komissarov, I. I. Rozentsveyg, V. K. Mishkinyuk, A. F. Kudryavtsev, B. V. Mitin, P. S. Sologub, R. L. Byhovskaya, V. I. Egorov, M. N. Pligin, B. P. Zarubin, and B. M. Lubenko; bottom row: A. P. Bravchuk, L. O. Vaysfeld, L. N. Polyakov, M. B. Shvartsburg, A. L. Kemurdzhian, A. F. Solovev, M. I. Malenkov, and A. M. Nosov |
In 1963, the director of the institute, V. S. Starovoytov, and the leader of works, A. L. Kemurdjian, considered building a space transport machine not as an individual task but as a strategic objective of creating a new field of studies.
Their approach made it possible to create a relevant experimental production base from the ground up. It required the development of the transport vehicle theory applicable to locomotion on the surface of the Moon, Mars, and its secondary planet Phobos. This resulted not only in the creation of various locomotion systems but also in the development of the Russian School of Planetary Rover Design [23,24].
A planet rover is a spacecraft designed as a transport vehicle with high cross-country capability. It is delivered to the place of its exploration by a spaceship and is intended for the transportation and operation maintenance of the scientific equipment installed on it as well as the transportation of cosmonauts on the surface of planets, secondary planets, and other celestial bodies. If a planet rover is controlled by a cosmonaut on board, it is classified as a piloted vehicle. In case of other control methods, planet rovers are classified as automatic (robotic) vehicles with different degrees of autonomy.
From the beginning, the Soviet lunar rover was designed as an automatic vehicle with remote control. The project of building a “mooncraft” (Lunnyi Korabl: LK) developed at the end of 1964 in OKB-1 within the complex No. N1-L3 did not include the lunar rover (Fig. 4 [12]). The “mooncraft” with a height of 5.2 m had to have a landing mass of 5560 kg and a takeoff mass of 3800 kg. It was designed for one cosmonaut; the second one had to wait for the first one’s return from the moon surface inside the moon orbital spaceship. The designers of the former OKB-1 returned to the objective of building a manned lunar rover only in 1974 when they developed technical proposals for the “Zvezda” moon expeditionary complex [12].
 | Fig.4 Layout of the moon craft in accordance with the N1-L3 project [12]1–Moon landing unit; 2–Rocket unit E; 3–Cosmonaut cabin; 4–Life support system units; 5–Observation device; 6–Attitude engine unit; 7–Radiators of the temperature-control system; 8–Docking unit |
The proposed definition of the automatic planet rover allows for the specification of its most significant properties and can serve as a basis for comparative analysis of engineering solutions at different stages of the design process. Thus, the main properties of the planet rover as a spacecraft are minimum mass and stowed dimensions, reliability, stability, strength, and resistance to various external factors. By the start of work on the lunar rover, a certain experience in the design and maintenance of the Spacecraft (Kosmicheskyi apparat: KA) system set properties was already gained. This included navigation, power supply, telecommunication, and thermocontrol systems.
The main properties of the planet rover as a means of transport (TS) are cross-country capability, maneuverability, steerability, load capacity, stability against overturning, road-holding ability, and cruising range [5]. Altogether, these properties reflect performance quality, i.e., the transport function of a vehicle often called mobility.
Mobility mainly depends on the locomotion system, that is, the self-propelled chassis that directly interacts with the surface of the area on the Moon and Mars selected for landing. The time spent moving from Point A to Point B within the limits of the set area with unprepared terrain can be regarded as a generalized characteristic of mobility. The more difficult the route is and the lower the set speed of locomotion is, the stronger a planet rover’s cross-country capability is. The degree of its adaptation to terrain and soil properties affects its mobility.
Cross-country capability characterizes the capability of a planet rover to move over the surface of celestial bodies at a given speed without loss of mobility and with minimal deviations from the prescribed route to bypass obstacles. In literature, a distinction is made between “relief” cross-country capability and “soil” cross-country capability. In the first case, the geometric characteristics of the terrain are utilized as criteria. These characteristics can be the maximum height of a step and separate rocks that are crossed by the planet rover without obstacle avoidance. The most universal characteristic value of “soil” cross-country capability over lunar regolith and loose soil is the slope climbing angle. Uniform locomotion on steep slopes is considered a calculation scheme for traction and dynamic calculation and selection of the electromechanical drive for motor-in-wheels.
Therefore, the main problem in the early stages of the design was the lack of a physical model of lunar soil. Various opinions on the consistency and strength of the top cover of the surface of the Moon existed. For example, it was assumed that in the absence of air and under low gravity, the surface of the Moon over millions of years of bombardment should be covered with a layer of extremely fine-grained loose material. The imaginary lunar soil could be a kind of suspension of poorly connected particles.
Aside from leading Soviet and American astronomers, prominent scientists from other branches of science, such as Nobel laureate P. L. Kapitsa, shared approximately the same view. According to P. S. Sologub, one of the leaders in the development of Lunokhod-1, this was manifested in one of the meetings attended by the prominent Soviet physicist in Moscow in 1960.
The most vital topic of discussion at that time was the means of locomotion over the surface of the Moon. The participants argued about the benefits and drawbacks of wheeled and tracked propulsion and discussed walking and other similar means of locomotion possible in case the surface was solid.
Peter Leonidovich Kapitsa began his emotional speech while on his way to the podium, as the witnesses tell, with these words: “ What they say here? What wheels!? What tracks!? On the Moon they must move this way!” He moved his hands and body vigorously, similar to the process of poling in a boat on shallow water. However, the theory that the Moon has a solid surface also had supporters. K. Feoktistov, who was one of the famous project engineers of OKB-1 and later a pilot-cosmonaut, expressed this idea very clearly when he said that it is possible to ride a regular bike across the Moon.
The members of Gorkovskiy Research and Development Radio-physical Institute (now Nizhniy Novgorod Research and Development Radio-physical Institute, NIRFI) presented the winning arguments to start the formulation of a modern perception of lunar soil density. Their studies of the Moon conducted by means of radar showed that its surface is a cohesive although reprocessed and deformable environment. These considerations were expressed in the working hypothesis of the lunar soil model that was developed in the technical meeting initiated by VNII-100 with the support of OKB-1 and the Interdepartmental Science and Technology Council (Mezhvedomstvennyi Nauchno-Tekhnicheskyi Sovet: MNTS) on space studies. The meeting was held in Kharkov Astronomical Observatory in March 1964. The meeting was participated by astronomers N. P. Barabashov (Kharkov University), V. Sharonov (Leningrad University), V. S. Troitskiy (head of radar research, NIRFI, Gorkiy), Y. P. Efremov (MNTS on KI, Moscow), V. P. Zaytsev and V. V. Molodtsov (OKB-1), and A. L. Kemurdjian and A. P. Sofian (VNII-100).
According to the hypothesis, the most likely model for the calculation of lunar soil was the statement, “ it is silicate rocks in foam-porous or fractured state, consisting of 40%–70% SiO, 10%–20% of Al2O3, the rest-iron oxides, calcium, potassium, sodium, and magnesium, which corresponds volcanic tuffs, slag or pyroclastic materials on Earth. Strongly reworked under vacuum, hard radiation, solar wind, and meteorite impacts, leading to excision of rock and soil formation of a special ‘lunita’, which has no direct analogues in the world. The top cover has strength of 0.2–1.0 kg/cm2” [18].
In 1964, a wagon of rock in the abovementioned form of “pored foam” was delivered to VNII-100 upon the contract with Armenian SSR Scientific Research Institute of Rock and Silicates for the creation of ground channels. It was pumice-stone, slaggy lava, and tuff from Armenian deposit.
Despite the efforts of VNII-100 and OKB-1 employees to grant the coordinated decision on the status of the official model of the Academy of Sciences of the USSR, they did not succeed. Academicians did not push forward. The document suggested a high level of responsibility.
S. P. Korolev took the responsibility in this key issue. On October 28 in 1964, in response to the increasingly insistent complaints from the designers of lunar landers about the absence of an approved model of the lunar surface, he wrote a short reference (Fig. 5) [12].
 | Fig.5 Autograph of S. P. Korolev (the abbreviations are given below with a detailed transcription) reference [12]The calculation of the moon craft landing should be made for quite hard soil of pumice typeVertical speed is ≈ 0 m/sec when going down at h=1 m+Lateral speed should be almost ≈ 0 m/s28th of October, 1964 S. P. Korolev |
Several researchers and journalists tend to see in this reference signs of solving technical problems by volitional methods. However, many experts, including the author, see in this episode a reflection of the talent, intuition, performance, and understanding of S. P. Korolev of his role as the chief designer.
A. L. Kemurdjian formed a small group on the base of Department 25, with the objective to determine if a self-propelled chassis can be created for the lunar rover. The group included I. I. Rozentsveig, V. I. Komissarov, A. V. Mitskevich, and V. K. Mishkinyuk. In October 1963, the first structural unit of space studies, i.e., Office 255, was created by this group. When the first contract with OKB-1 was signed, the name “Shar” appeared as a theme code. Experts from main tank departments of the institute were also involved in the work of the office. Many of them became employees of the space departments.
Consequently, several design layouts of the lunar rover and individual technical solutions regarding its units were established. This made it possible to represent the engineering concept of the lunar rover, conduct an analysis of its weight, make first calculation estimates of its traction characteristics, cross-country capability, and durability of propulsion, and analyze the materials and lubricants in relation to the machinery in a vacuum. The initial data for traction calculation were obtained, and recommendations regarding the technical design specification of the lunar rover were provided.
On May 31, 1964, the institute was secretly visited by S. P. Korolev. He was accompanied by deputies M. K. Tikhonravov, S. S. Kryukov, and K. D. Bushuev as well as engineers V. P. Zaytsev and V. V. Molodtsov. On the weekend, S. P. Korolev was accompanied by his wife Nina Ivanovna. At the end of the day and their stay in Leningrad, the couple visited the Russian Museum.
On the part of VNII-100, aside from the director and manager of works, I. I. Rozentsveig, G. N. Moskvin, P. N. Brodskiy, F. I. Abramov, V. I. Komissarov, and D. Y. Klyatskin also stayed as guests in the tank institute. The author, who began his work for VNII-100 in November 1965, attempted to reconstruct the exact details of that visit based on the accounts of the direct participants of those events.
Distinguished guests saw the production and laboratory base, armored vehicles, and large kennel that was necessary for safeguarding the area of more than 2000 hm2; it was a real pride of the director.
The model of the device for the physical and mechanical properties (FMP) of lunar soil had already been produced by that time. A so-called “top brass effect” occurred during its demonstration; the device stopped and did not fulfill a task. The designer of the device, P. N. Brodskiy, secretly (as it seemed to him) helped it with his arm, and the demonstration finished successfully. However, according to the designer and witnesses of this episode, S. P. Korolev noticed this nudging and at the end of the meeting, he said, “ it is not possible to help with a finger on the Moon”.
The main report on the possibility of creating the lunar rover was provided by A. L. Kemurdjian. He reported on the project designs of the lunar rover with different methods of locomotion and discussed expected problems, such as uncertainty of the lunar soil properties, absence of experience in vehicle operation in a high vacuum, imitation of the gravity field of the Moon during performance trials, the huge range of operational temperatures, and the absence of a laboratory and production base. He also paid attention to the impossibility of realizing several points of the technical design specification developed by the project division of OKB-1. For example, the project engineers set the locomotion speed to 20 km/h and the driving distance across the Moon at 10000 km.
According to I. I. Rozentsveig, S. P. Korolev reacted by stating that [25] “ all your proposals and asks are reasonable. Financing will be provided, special block should be built, allied experts will work. We will also assist with vacuum trials. Now a big government regulation regarding the item N-1 is being prepared, all your proposals should be included in it”.
Then, S. P. Korolev approached the poster with the picture of the future moon rover equipped with tracked propulsion and said, “ creating space objects, the main thing is reliability! We should not set records. It will be the first vehicle. No one before us was on the Moon, this is a first in the world automated device. It is unknown how to control a vehicle from Earth, how materials and lubricant will behave in space vacuum. That is why we should lower performance parameters… It is necessary that the lunar rover run across the Moon at least 10 km with not very high speed…. This became unexpectedness not only for us, developers, but also for other employees of OKB-1, who have stood up for the necessity of ‘Earth’ characteristics of the self-propelled platform for a year” [25].
The chief designer showed much respect to the designers from VNII-100 and was careful during the discussion of the key issue of selecting a method of locomotion. The reporter finished analyzing why walking, jumping, creeping, rolling over, and other exotic methods were rejected. He formulated the conclusion that for further development, wheeled and tracked propulsions had been selected. Everyone waited for the reaction of S. P. Korolev. However, he did not reveal his opinion on this issue and finished the discussion with the words, “ you are the experts in this topic, so make the choice yourself ” [18].
S. P. Korolev’s visit to VNII-100 prompted the decision on the solution to the organizational, financial, and manufacturing tasks of developing a new field of work, including the creation of a closed testing area in Gorelovo near the VNIITransmash building of the All-Russian Research and Development and Technologic Institute (VNITI). Later, A. L. Kemurdjian, remembering this visit, said many times that “ Sergey Pavlovich made the final decision to create the lunar rover and assign that work to VNII-100”.
We should note that S. P. Korolev was one of the creators of the space research in the tank institute. In the end of 1964, the document of the regular contract with OKB-1 for a sum of 4 million rubles, which was a significantly large amount of money at that time, was returned to the institute unsigned. The cover letter stated that another organization would handle the project.
The management of the institute was shocked. A. L. Kemurdjian attempted to contact the chief designer. He was in Leningrad at one of the plants. S. P. Korolev said in response to the sacramental question “ what to do? Consider that the contract is signed, return it addressed to my name, work calm”. The contract was sent back to Moscow. In the beginning of 1965, it was returned with the signature of S. P. Korolev [25].
In July of 1964, the first report on “Shar” was published as “determination of the possibility and idea of creating a self-propelled chassis for Lunokhod-1”. In the same month, a decision to create a thermal vacuum laboratory was made. V. M. Tarasov became its head. I. I. Rozentsveig played a big role in its organization, equipment, and development when he supervised this division as the deputy head of the department and when he became its head.
In October 1964, a large group of specialists from the institute who previously participated in the design of individual parts was transferred to Department 25 by the order of the director. This move made it possible to create a head laboratory of general machines and unit development (under the leadership of P. S. Sologub), Konstruktorskoe Byuro (KB) of this laboratory (V. I. Komissarov), laboratory of electrical drive (A. M. Nosov, then A. F. Solovyov who later became deputy chief designer), and laboratory of information and measurements (V. Gorevoy and L. K. Kogan).
Later, a KB of fine mechanics (P. N. Brodskiy), a laboratory of running trials in different periods of time headed by Y. P. Kitlyash, I. M. Khovanov, V. N. Petriga, and V. V. Gromov, and a small but highly skilled production unit (heads of the unit in various periods: A. A. Kokhan, S. V. Tatyblin, and V. A. Kozyrev) were created.
On February 10, 1965, the assignment to VNII-100 that concerned the creation of a self-propelled chassis for the lunar rover and was already being fulfilled; it was approved and detailed by Decision 23 of the Military-Industrial Commission (Voenno-Promyshlennaya Komissiya) of the Council of Ministers of the USSR [15]. The institute (Fig. 6) was granted a right to increase the number of employees to 150 people. Further executive decisions and decrees of the minister included measures for maintenance of VNII-100 work on the lunar rover chassis, particularly the building of a laboratory and manufacturing blocks. However, because of the lack of funding, construction of buildings began only in the middle 1970s.
 | Fig.6 Main block of VNII-100—VNIITransmash in Gorelovo (courtesy of VNIITransmash) |
Fundamental reorganization of work, involvement of new intellectual resources at full capacity, strong influence on the creative process of young managers, researchers, and designers, all of this had the most beneficial effects. Research became systematic, and design, engineering development, and calculations became more detailed and clear.
The number of engineers was approximately 35 to 40 in the beginning of 1965, and the average age of the employees did not exceed 26. The latter gave the head a reason to answer the question of how he could solve this unusual problem starting from the ground up with the joke: “ We were young and did not understand this”.
In May of 1965, the second report on “Shar” was published; it was called “development of chassis of the self-propelled automatic device for exploration of the Moon”. Its content reflected the changes in the organization of tasks. The report was based on new project developments, the results of propulsion model trials, and trials of the lunar rover test mules held in the ground channels.
In autumn of the same year, the entire complex of work on interplanetary automatic stations, including the development of the lunar rover, was transferred by S. P. Korolev to the special design bureau (OKB) named after S. A. Lavochkin. With the assistance of S. P. Korolev, the introductory period passed by quickly, and good business relations with a new customer, known now as S. A. Lavochkin Association (NPOL), were established at all levels. A significant contribution was provided by the chief designer of Luna-17 and Lunokhod-1, G. N. Babakin [13,16,26–28], A. L. Kemurdjian who was the chief designer of the self-propelled automatic chassis of the lunar rover, and their supporters. They laid the foundation for the future long-term cooperation of enterprises and teams [9,10].
The institute focused its efforts on creating a self-propelled chassis (Fig. 7) with an automatic control unit and a system of locomotion safety. It was the first time in the history of the institute when it had to deliver models and flight prototypes as well as conduct acceptance of delivery (Priemo-Sdatochnye Ispytaniay: PSI), qualification tests, and inspection-sampling tests.
 | Fig.7 Tank testing area of VNII-100 with the first models of the moon rover: (a) With wheeled running gear and (b) with tracked running gear (courtesy of VNIITransmash) |
The Central Office of Spacecrafts of the Ministry of Defense created a representative office for the customer in the institute to control the progress and quality of work. Its first head, E. A. Sekerzhitskiy, who had vast experience in the organization of such work, significantly helped the divisions of the chief designer, chief engineer, and technical control services.
However, several difficulties were encountered. Building relationships with the structures of the Ministry of the Defense Industry was not easy. The civil and science division of space research on the moon surface and other planets did not meet the main objectives of the Ministry. An opinion inside the institute was that the work related with space studies was not typical for the dedicated experts and was conducted at the price of the main tank sphere. The Party Committee of the institute even recommended shutting down the work in the field of space studies.
The main technical problems remained the right choice of the self-propelled chassis model, its design layout, structure and parameters of its units, and its mechanical, electric, and information interaction with the systems of the lunar rover. All technical solutions had to consider restrictions on mass, size, and power consumption as well as the consequences of unfavorable factors during the delivery of the lunar rover as a part of the lunar station and its operation. The set source was three Earth months, and ensuring the operation of the device without the need for servicing and repair was necessary.
The development of the concept and structure of the self-propelled chassis was implemented by the general machine laboratory. The key role was played by the Design Bureau (KB) of the laboratory, where three design and engineering groups were organized. The ideologist of the track chassis was the head of the rover group, experienced designer and tank-driver M. B. Shvartsburg. Of course, this option was more acceptable to the leaders and many other members of the institute who were not directly related to the development of the lunar rover. After all, they were the employees and patriots of the tank institute of the USSR.
The consistent position of the laboratory head, P. S. Sologub, was important for the reasoning of the wheeled chassis. He was supported by the head of the design department, V. I. Komissarov, and the head of the layout design group, V. K. Mishkinyuk. The research of V. V. Gromov was of considerable importance for the selection of the type and geometry parameters of the propulsion. A. L. Kemurdjian passed to him the task of studying the problems of interaction with lunar soil. The staff of the department of tracked vehicles of Bauman Moscow Higher Technical School headed by V. N. Naumov, were engaged in this task as well.
The head of the transmission group, G. N. Korepanov, was ready to realize any of the models. The head of the calculation sector of the chief laboratory, F. P. Shpak, maintained his neutrality, which was normal for a third party [29].
A struggle existed with regard to the opinion of the chief designer. It was probably the most difficult period in the formation of the space studies team of VNIITransmash. Having the acknowledged authority and diplomatic skills of A. L. Kemurdjian was necessary to prevent the team from splitting up. According to him, selecting the correct method of propulsion took two years.
To the credit of the team and, of course, its leaders, when the choice was made in favor of wheeled propulsion, those who previously opposed the idea managed to overcome their personal sentiments. The delicate but strong spoke wheels with a mesh rim and a mass of only 2.7 kg were created exactly as the rover group planned in cooperation with Kharkov Central Designing Bureau of Velocipede Building. They provided the good traction characteristics of Lunokhod-1 in rectilinear locomotion and turning.
In the new cooperation, the work achieved the level corresponding to the grand pioneering task. Particularly, space experiments aimed at solving the most challenging issues in designing the lunar rover (e.g., determining the physical and mechanical properties of lunar soil and estimating the working capacity of the heavily loaded friction couples in space) were conducted.
In February 1966, Luna-9, as revised by NPOL, made a soft landing for the first time. Luna-9 provided the first reliable information about the properties of lunar soil. This landing was followed by special experiments aboard the station Luna-13 for the FMP assessment of lunar soil using a mechanical ground meter penetrometer and radiation density meter.
These flights revealed that the answer to the question of the Moon surface’s hardness was somewhere in the middle of the abovementioned judgments [4]. The regolith deformed easily under pressure, but the more it was pressed, the better its load-bearing strength was.
The scheme of the ground meter and the measuring method offered by V. V. Gromov and A. L. Kemurdjian together with I. I. Cherkasov from the Moscow Institute of Basements and Foundations made it possible to estimate the lunar soil load-bearing strength under natural conditions. The idea of the experiment was discussed at a meeting in the Academy of Sciences of the USSR with the participation of its president, M. V. Keldysh.
The designers of S. A. Lavochkin OKB released engineering documentation based on this scheme; the manufacturing process was organized at the S. A. Lavochkin Plant (Fig. 8), which helped prevent blaming in the use of the test production facilities of VNII-100 by non-core workers at a price of the tank industry [11].
 | Fig.8 (a) Landing unit of Luna-13 station in deployed configuration; (b) soil measuring penetrometer with a pushed-out indenter [4] |
The device (Fig. 8(b)) consists of a plastic housing, the lower part of which forms an annular die with a maximum diameter of 120 mm and an indenter with a titanium conical part. The taper angle of the indenter cone is 130°, and the maximal diameter of the cone is 35 mm. The indenter can be pushed out of the housing down to a distance of 50 mm under the action of a small jet-engine nozzle directed upward. The engine thrust is 65 N, and the pulse duration is 0.8 s.
Luna-13 landed near the western edge of the Ocean of Storms, a typical flat seaside area. Onboard manipulators removed the die block of the ground meter and the radiation density meter and placed them on the soil (Fig. 8(a); a small part on the extreme left). After the jet engine was activated, the indenter was buried in the lunar soil to almost 45 mm depth.
Telemetric information processing made it possible to measure the FMP parameters of lunar soil and revealed that the load-bearing capacity was 44 kPa and internal cohesion was 0.5 kPa in the case of single-axis loading. The internal friction angle was 32°. With the radiation density meter, the range of possible values of the top layer of the soil was estimated to be 0.8 to 2.1 g/cm³.
In cooperation with Lavochkin Plant, VNII-100 managed to conduct tribological studies of the friction couples in open space, the possibility of which was discussed by the initiators of the experiments, A. L. Kemurdjian and S. P. Korolev.
At that time, the individuals involved in the project feared that the movement of highly mechanical gears in a vacuum would be accompanied by the sticking and solidification of the materials. A number of scientists even assumed that welding could occur because of the high voltage in contact and the possible absence of separating films. Existing experience on the operation of space mechanisms covered only lightly loaded instruments usually used for a one-time action [8].
Experimental assemblies (R-1) were designed for the purpose of research (Fig. 9). Five of such assemblies were tested in open space, on the outer surfaces of the Moon, and in the orbital KA of Luna-11, Luna-12, and Luna-14. The space experiments were conducted with different combinations of construction and lubricating materials of the friction couples. Simulteneously, three units of R-1 with different components were installed on Luna-14.
 | Fig.9 Experimental assembly of R-1: (a) Scheme; (b) photograph (courtesy of VNIITransmash)1–Supporting block of the tested gear pair; 2–Kinematic pair; 3–Magnetic coupling; 4–Electric motor; 5–Sensors of temperature; 6–Sealings; 7–Pressure-sealed connectors; 8–Torsional spring; 9–Tested gear pair |
The purposes of the assemblies were the comparative evaluation of the working capacity and efficiency of the loaded gears at work in the vacuum of space and parallel thermal vacuum testing on Earth. Each assembly served as a board test stand for gears on a closed circuit with power together with electronics designed to interface with the assemblies with onboard equipment stations. The assemblies were developed by the head of KB, V. I. Komissarov, under the short-term control of P. S. Sologub.
The selected model provided relatively high contact stress in gear (approximately 5000 kg/cm2, as per Hertz formula), with the driving motor having a small mass (only 1.5 kg) and small power (less than 3 W); the energy was used only to compensate for the losses in gears and ball bearings.
The unit fulfilled commands and the transmission of telemetric information about the temperature of the housing and drive motor current on Earth. This ability allowed scientists to determine the shaft torque and calculate the efficiency coefficient. The electronic unit was developed by engineer V. Gorev in the laboratory of electric drive and measurements. Construction of the unit was developed by the design department of fine mechanics.
Metal-ceramics on the iron base with glass inclusions, recommended by the specialists of the thermal vacuum laboratory for the production of the gears of the first flight model R-1, were created in accordance with the technical design specification of VNII-100 and produced at the Kiev Institute of Materials Technology (Institut Problem Materialovedeniya), Academy of Sciences of the Ukrainian SSR, under the leadership of I. Radomyselskiy.
This experience was the first for the institute in terms of delivering a flight model to the S. A. Lavochkin Plant for installation on board KA. This is why the creation of the R-1 model inspired a school of development and delivery of space technology items. The author was lucky to participate in offline tests and integrated verifications of all three sets of R-1 models at the control and test station of the plant and at the Baikonur Cosmodrome.
The tests were conducted successfully. Luna-11 was in orbit for approximately 34 days, and the length of operation of the R-1 unit was 5 hours. The following experiments were longer, and the operation of the R-1 unit took dozens of hours. All friction couples with self-lubricating materials, grease, and powder lubricants worked stably.
Although the frictional characteristics were different, sticking and solidification did not occur. These results strengthened the designers’ confidence in the correctness of the selected materials and methods of simulating mechanisms in space within laboratory conditions.
Successful experiments conducted in space and in laboratories encouraged the development of the chassis. The advantages of the wheel became increasingly obvious; the center of a wheel was a good place to install a traction electromechanical drive with planetary reduction gear. Almost all subsystems, units, and complex and critical parts and assemblies were tested on a competitive basis. These parts had 2 to 3 design variants, which became a subject of in-depth and detailed discussions many times in the KB of the general machines laboratory. Aside from engineers, experts in electric drive and automation, material and thermal experts, and test and technology engineers of the test production often participated.
Keen discussions with the participation of the chief designers first occurred at the drawing boards of the project engineers of the layout design group. Then, when the general concept of the chassis became increasingly clear, the discussions moved to the drawing boards of the engineers of the rover and transmission. Propulsion, suspension, and traction drive, which determine the technical and design appearance of a new vehicle in the best manner, were drawn in detail. Changing the discussion environment was simple because all the KB staff were housed in the same room.
The chassis concept is defined by its structure, type of components, and characteristics of the interfaces. The chassis consists of supporting structure, chassis (including the propulsion and the mechanisms of its suspension), individual wheel traction electromechanical drives, chassis automation control unit (Blok Avtomatiki Shassi: BASh), a set of built-in sensors and a subsystem of locomotion safety (including drive built-in sensors and release mechanisms and a trim and list sensor (Datchik krena I differenta: DKD) built into the housing of BASh), and an individual on-board maneuverability assessment device (Pribor Otzenki Prokhodimosti: PrOP) with an odometer (ninth free-rolling wheel) [1,8].
The release mechanisms provide an opportunity for the controlled disconnection of the kinematic chain “traction drive-propulsion”. Blacking of the gear was the main issue that could require the disconnection of this chain.
The type and configuration of the load-bearing structure of the chassis were defined during the process of mutual work with Lavochkin Plant. The chassis consists of four carriers attached to a bearing bottom plate of the lunar rover sealed container (Figs. 10, 11, and 12 [1]). To separate the construction of the chassis and container, which were developed by different organizations, the support and guide mechanisms of suspension had to be placed exactly in the carriers. Such a solution eliminated the need for the frame, which was developed as a tool required only during verifications and model trials. The carriers had so many functions that their construction and technology were improved by dozens of specialists. The most prominent specialist was N. E. Bechvai.
 | Fig.10 Scheme of the self-propelled chassis in conjunction with the Lunokhod-1 container (courtesy of VNIITransmash)1–Left wheel unit; 2–Right wheel unit; 3–Right carrier; 4–Pallet of the container;5–Left carrier; 6–Container; 7–Cross-country ability assessment device; 8–Chassis automation control unit |
 | Fig.11 Scheme of the integration of the self-propelled chassis with the sealed container (plan view) (courtesy of VNIITransmash)1–Left block of wheels; 2–Right block of wheels; 3–Right carriers; 4–Sensor of roll and trim; 5–Left carriers; 6–Cables; 7–Device for cross-country ability estimation equipped with 9th wheel; 8–Automatic unit of chassis; V–Direction of forward locomotion; v–Direction of extreme wheels sliding during turning to the right; B–Track; L–Wheel base |
 | Fig.12 Motor-in-wheel module of Lunokhod-1 self-propelled chassis (drawing by V. V. Grinev) [1]1–Middle hoop; 2–Lug; 3–Outermost hoop; 4–Net; 5–Jet propulsion; 6–Carrier; 7–Fasciculate torsional bar; 8–Balance of the suspension; 9–Reaction arm; 10–Electric traction drive; 11–Spoke; 12–Wheel hub |
An eight-wheel model was considered for wheeled propulsion. It fit well into the dimensions of the landing unit of the moon station and met the requirements of high cross-country capability and stability in fulfilling the main transportation function of the chassis. Particularly, the eight-wheel model provided motion in case of the emergency release of two or even three wheels. The requirement of approximate equality (in terms of cross-country capability) of the forward and reverse motions of the vehicle was fulfilled.
The construction provided the possibility of connecting the structure of the chassis to all embedded individual drives of each wheel and the sensors of the information system to four aggregates similar in terms of construction or just modules of the motor-in-wheel. This setup minimized the terms and number of tests and increased the reliability of the chassis.
“Tracked trace” was selected as an 8×8 wheel formula. Calculations and trials of the eight-wheel models demonstrated confident maneuvering of the chassis on different types of soil with tank or board rotation. Steering mechanisms were not required in this method; they only increased unsprung masses and decreased the reliability of the transportation function.
Board rotation of the lunar rover was accomplished by controlling the rotational speed of the wheels on the opposite sides. Reverse of boards allowed the rover to turn with a radius of zero (so-called “turn on the spot”). To reduce the sliding resistance of the wheels, lugs were used at an angle to the generatrix of the wheel rim (Fig. 11).
This setup led to the right and left blocks of motor-in-wheels having different lug patterns, stops, and arrangements of the cables connecting the blocks to the container. The idea of “tracked trace” was also an eight-diagram concept; if necessary, it could relatively and easily be transformed into two-track propulsion.
No significant arguments existed about the type of suspension. The locomotion of the multi-wheeled lunar rover with a mass of 700 to 800 kg and speed of 1 to 2 km/h on difficult terrain required the use of elastic suspension wheels capable of large movements that could be obtained by using oscillating rockers.
Suspension was intended to solve two problems: To improve floatation and cross-country capability and to provide the amplitude-frequency oscillation characteristics of the sprung part suitable for the on-board equipment. Therefore, the choice of suspension parameters, as a rule, was the result of a compromise among project engineers, designers, and calculators of traction and performance characteristics, smoothness of movement, and stability against overturning.
The front suspension had a stiffness of approximately 8800 N/m and static deflection of 21 mm. The middle wheel suspension was softer at 3500 N/m, and its static deflection was 60 mm. The dynamic deflection of all the wheel suspensions was 100 mm. The swing angles of the beams within a specified course were limited by stops. These characteristics provided the contact of all wheels with the soil in overcoming a height of up to 400 mm by the middle wheels and running down by the side wheels of the offset height up to 400 mm without breakdown of the suspension.
The suspensions were made according to the scheme of a longitudinal arm swing, with transverse positioning of elastic elements. Damping vibration energy when moving the lunar rover was due to losses in the suspension joints and wheels and contact with the soil.
To construct the wheels, designers adopted the maximum possible wheel diameter with lugs of 510 mm. Various suggestions were provided for the wheels’ properties when in contact with the lunar regolith and in areas with lunar surface rock outcrops.
The concept of the self-propelled chassis also considered the properties of the remote control of the moon craft and ground control in the Deep-Space Communications Center near Simferopol. When the recording of the multi-terrain camera was reviewed, an operator saw on the screen a picture shot a few seconds back. In addition, commands reached the lunar rover with a certain delay. As a result, from command to command, the lunar rover could drive from 2.3 to 8.3 m depending on the operating mode according to V. G. Dovgan, one of the drivers [30].
To prevent accidents that could lead to loss of stability against overturning, overheating, and failure of the traction motors, the security subsystem provided an automatic “stop” command at the maximum possible angle of inclination of the device and overcurrent limit. Periodic measurements of the mechanical properties of lunar soil samples by means of PrOP during the device stops provided an insight into the strength of the soil in this part of the track and allowed for the adjustment of the route in a timely manner.
Prior to the drawing of the wheel assembly with incoming parts appearing at the drawing board, its fragments were born on a plumbing workbench. A. P. Bravchuk, a locksmith-tinsmith, produced dozens of models of rigid and flexible experimental wheels with his hands, uncomplicated tools, and devices that he invented himself. The task was provided to him by designers.
Rigid wheels (Fig. 13) included structures in which the following condition is satisfied: The radial deformation of the rim when compared with the deformation of the supporting base in the range of workloads is negligible. In the theory of wheeled vehicles, a rigid wheel contact surface is called a rim, and an elastic wheel is a tire. The scan of the rim or the tire on the support plane is called the treadmill, and the imprint of the wheels on the support surface is called the spot or area of contact.
 | Fig.13 (a) Block of the motor-in-wheels of the moon rover’s self-propelled chassis; (b) a fragment of a rigid wheel spindle layout after running trials (photo of an exhibit at the museum of VNIITransmash, courtesy of VNIITransmash) |
The concept of the chassis with board rotation left no chance for elastic wheels because of the significant axial deformation of the tire. A tractive force of the rigid wheel with a solid rim limited the coefficient of friction of metal on soil. In tractor and tank propulsions, the traction is increased by installing lugs, which are closely related to the process of creating traction reserves for weakly cohesive soil, internal cohesion, and friction particles.
However, making the rim sections between the lugs work more effectively posed a problem. During the tests, the problem was solved by organizing the treadmill as a uniform but not a solid structure. Designer A. I. Egorov conducted tests with continuous, smooth, and cellular 150 mm×170 mm stamps at a normal load of 500 N on physical models of lunar soil. He found that the shear strength reflecting the traction properties of a pair of wheel-soil in a cellular stamp formed in a grid on the die was 20% to 40% higher than that of a plate on dry quartz sand. As a result, an inelastic steel seamless mesh with a 3.5 mm×3.5 mm cell and a wire with a diameter of 0.5 mm was selected for the wheel of Lunokhod-1 as the treadmill. When the size of the cell was increased further, the depth of immersion of the stamp into the soil increased substantially with equal normal loads; such an increase was irrational. The effect of grid work could be seen when the rover drove on fresh soil without slipping.
This event was followed by wheel model tests in the ground channel. These tests allowed the designers to specify the step, height, shape, and final design of the lug and wheel as a whole. The wheel had three profile-welded titanium wraps topped with a grid, which is pressed by means of rivets to the mean and extreme hoops with two rows of oblique titanium lugs. The edges of the mesh were sewn on the outer hoops. Installation of the lugs in the ranks was the same but was shifted to a corner of a half step. Therefore, a step in an outer hoop was two times bigger than that in an average hoop.
The diameter of a middle hoop was slightly larger than the diameter of the outer hoops. Hence, a radial sectional profile of the rim was close to a large arc diameter. When driving on a solid surface, such as rock outcrops, the wheel achieves discrete point contact. Owing to the overlapping of lugs on the middle rim, the smoothness of rolling was improved. On soft soil, a lug does not have discrete dynamic aspects because of the deformation of soil.
Each hoop was connected to the wheel hub with 16 conventional bicycle spokes, creating an extremely tough and durable spatial relationship between the hub and the rim. No extra elements nor extra metal existed in a wheel. Even the lugs had holes; tests have shown that a decrease in the contact area with the ground, subject to certain proportions, does not reduce traction.
The wheel, a fragment of which is shown in Fig. 13, underwent various running trials for several years. The plastic deformation of individual lugs and local distortion of the grid pattern were clearly visible. However, the wheel did not lose its shape even when simulating an impact weighing more than 700 kg at a maximum speed of 2 km/h in an insurmountable obstacle when the dynamic force reached 5000 N.
The main suspension design objective was a combination of requirements: A large torsion bar spin angle with small length limited by the dimensions of the carrier. The solution was found in the process of mutual work of designers, materials specialists, and technologists in the form of a three-rod torsion bar beam from alloy VT22 (Fig. 14). Among many others, this decision increased reliability. In case one of the beam rods fails, connected at the ends by two clutches, the chassis retains mobility. Tuning of torsion as well as coordination of the entire process had become the life’s work of B. V. Gladkikh.
A structure of a wheel suspension guide mechanism was tested in the process of running trials; the structure was originally a rocker. However, in this case, wheel reaction torque circuited to the frame through the torsion bar. This resulted first in vertical movements of the housing and second in the tightening of torsion work modes.
The identified problem was quickly resolved by executing guide mechanism suspension by a parallelogram scheme. In this case, wheel reaction torque circuited to the frame by a pair of forces acting on the rocker joints and jet thrust. Suspension torsion bars worked only when activated by the action of forces normal to the support surface.
The traction drive has a simple kinematic diagram (Fig. 15 [4]) but a tight integration and highly complicated conjugations of mechanical, electrical, pyrotechnic joints and components (Fig. 16 [1]). According to the chassis chief designer’s words, “ creation of electromechanical transmission for the lunar rover is an undoubted success of designers from the nodal design bureau, and first of all, a talented designer, a head of the development G. N. Korepanov” [15]. The group of transmission under his leadership included V. V. Grinev, E. N. Druyan, G. I. Rykov, M. I. Malenkov, V. I. Koynash, and A. F. Konstantinova.
 | Fig.15 Traction drive kinematic diagram [4]1−Wheel center; 2−Gearbox housing (epicycle); 4−Rocker; 5−Reaction arm; 6−Brake; 7−Second row of the three-row planetary gearbox; 8−Lock release mechanism; 9−Terminal flexible seal |
 | Fig.16 Motor-in-wheel of Lunokhod-1 (drawing by V. V. Grinev) [1]1−Hoop; 2−Net; 3−Hub of wheel; 4−Sensor of rotations; 5−Bearings of the hub of the wheel; 6−Balance of suspension; 7−Labyrinth packing; 8−Bearings of the balance; 9−Reaction arm; 10−Pressure-sealed connector; 11−Electric motor; 13−Brake; 14−Epicycle; 15−Three-lane planetary reduction gear; 16−Releasing mechanism; 17−Hollow output shaft with plane of weakness; 18−End seal |
The simplicity of the scheme was due to the application of a three-row planetary gearbox with “floating” (not supported by bearings) rows. Geometrically, including diametral pitch, number of teeth, and the original contour of involute gear-tooth form system, the first two rows are completely similar, and the third row has an increased width of the teeth.
The gear ratio of each row is equal to 6; the total is 216. During testing at the load bank at different temperatures with different materials and lubricant gears, the efficiency coefficient at rated load was not less than 0.85.
The pyrotechnic release mechanism was created in the Leningrad research institute “Poisk”; the head of development from VNII-100 was A. V. Mitskevich. Figure 16 shows the hollow output shaft. The entire testing of dangerous mechanisms, including verification of activation efficiency during beehive-shape charge blow up, occurred at the plant. Tests showed that all pieces of metal were discharged from the drive internal volume because of the hollow shaft, which did not prevent the rotation of the wheel.
At VNII-100, only the detonator circuits were checked using a standard procedure. However, the reliability of the mechanism was verified as well. A shaft was perfectly cut during night tests of the engine gearbox in a thermal vacuum chamber when an operator failed to monitor it and fell asleep. The developers at “Poisk” were satisfied; the actual temperature in the chamber was higher than 200 °C, which was identified as the limiting operating temperature in their datasheet. The explosion had no other consequences.
A system consisting of a radial labyrinth and a bellows mechanical seal proved to be an efficient system. It eliminated the penetration of dust and sand when tested at natural landfills of the Kara-Kum desert and truly provided a microclimate in the inner cavity of motor-in-wheels when tested in vacuum chambers.
The choice of electric motor type by the electric motor laboratory was influenced by the manner of board rotation. To rotate in motion, the chassis needed at least two different speeds of the wheels on opposite sides during rotation.
Thus, Engineer I. I. Glushkov proposed to develop for this purpose a special two-commutator motor with two windings. In the series connection of windings, the motor-provided motor shaft rotation rate was 1800(1±10%) r/min, with rated torque of 20 N·cm; in parallel, respectively, 4500(1±5%) r/min and 10 N·cm.
This decision was fully consistent with the general plan to increase reliability by duplicating the most critical components. In case of failure of one of the two windings or one of the two commutators, the ability of the chassis to maneuver would be reduced, but it would not lose its mobility.
Commercially available direct-current motors with graphite commutators were incapable of providing the required operating range; this fact was proven by the developers during the initial thermal vacuum tests. Commutator brushes wore out completely in just 40 min of work in a vacuum. Therefore, the decision was made to develop and manufacture a special two-speed motor with independent excitation from permanent magnets according to the technical brief of VNII-100 at the “Mashinoapparat” Moscow Plant. The new design utilized the latest materials and technologies that were known to experts of both establishments and their subcontractors.
The D-126 motor has a long service life in a vacuum, sufficiently high efficiency coefficient, and stringent mechanical characteristics, which all helped to avoid the synchronization of engine speed even on difficult terrain. During traction drive tests with a “dry” (without a plastic lubricant) reducer, such as the theoretical expedition Lunokhod-3, the engine worked 300 hours in a vacuum and did not wear out.
Tests on the first experimental samples of traction drive, as part of test mules, required changes in the concept of the chassis, specifically in the brake subsystem. These changes must be elaborated further because of their impact on the first lunar day of Lunokhod-1 operation on the Moon.
Initially, the stop braking functions were assumed to be performed by the direct-current motor when it switched to the generator mode of operation. The required braking torque of the parking brake could have created friction moments at rest in the commutator and reducer, normalized to the wheel. However, the high quality of these components excluded this possibility.
The first running trials revealed the following: Downward movement of the model continued after the command “stop” and activation of dynamic braking. A frictional disk brake that normally closed with electromagnetic control in the kinematic drive circuit was urgently needed. However, “Mashinoapparat” refused to change the design of the motor front panel D-126 because of a large production reserve. This refusal caused many difficulties in calculating and designing the magnetic core and coils of electromagnets, which were performed by D. Y. Klyatskin.
Designing electromagnets were necessary to provide confident closure of the magnetic circuit and, therefore, release of the frictional brake at the initial air gap of 0.4 mm and the action of a compression spring with a force of approximately 20 N. Neither the diameter nor the axial size of the specified electromagnets could be changed.
Given the lack of space, a sequential execution was implemented. A magnetic circuit closing function that took less than 0.1 s was executed, and the disc brake that was movable in the axial direction was held with friction lining in the closed state, the duration of which was determined by the time of continuous movement. The duration could be up to tens of minutes.
To execute the process, electromagnet coils with two types of windings were used. The first type was forced winding, with a current consumption of 2.00 A. The second type was hold-in winding, with a current of 0.05 A. Both windings were duplicated to improve reliability.
Thus, the total number of windings of the eight motor-in-wheels reached 32. BASh efficiently managed such an abundance, maintaining only the condition that the operation time of the electromagnet in the forced mode should not exceed 0.5 s. In the hold-in mode, the heat balance should be kept indefinitely.
As for the brake design, the choice of materials for rubbing pairs and the determination of their friction characteristics in air and in a vacuum at high temperatures considered the possible presence of plastic lubricants. In the summer of 1967, finishing thermal vacuum tests were conducted. This part of brake development was fulfilled by M. I. Malenkov.
The cryogenic vacuum equipment of VNII-100 was installed and tested. Tests were conducted in Kharkov with the equipment of the Physico-Technical Institute of Low Temperature of the Ukrainian Academy of Sciences. Owing to the use of liquid nitrogen and helium vacuum, one billionth of mercury was obtained. This vacuum was sterile and free of oil vapors, such as that from diffusion pump working fluid.
Successful tests were conducted in a chamber for both friction couple of the disc brake and traction motor D-126. Tests of the motor were conducted under the leadership of A. F. Solovyev. The other participants were S. V. Gurkalo, L. O. Vaysfeld, and “Mashinoapparat” specialist A. Mamlin.
The information control subsystem of the chassis was implemented in the design of BASh (Fig. 17). Trim and list indicator are shown at the top left of Fig. 17. The telecommunications system, which was utilized to connect the lunar rover to Earth, is not shown.
 | Fig.17 Chassis automation control unit of Lunokhod-1 (courtesy of VNIITransmash) |
BASh was originally developed in the laboratory of information and measurements under the direction of L. H. Kogan (general structure, information processing from sensors and telemetry) with the participation of R. L. Bykhovskaya and A. F. Solovyev (reception and execution of locomotion commands). Afterward, the entire leadership in the development of the chassis automation control unit was assigned to A. F. Solovyev.
BASh aimed to achieve the following: Convert remote control commands and issue commands to the actuators, generate commands for the board subsystem of safety operations, convert the signals from measuring sensors, program the device for assessment of maneuverability, and process measurement results to be transmitted to Earth [1].
In accordance with the functions performed, BASh consisted of the following groups: Movement management, generation of commands for the board subsystem of safety operations, measurement and control, and management of PrOP (Fig. 18 [1]). Each group consisted of several functional blocks. The movement management group contained the blocks of movement, braking, and stopping. The movement block consisted of a logical device whose input receives locomotion commands in the form of voltage pulses and the actuating commutator of the traction motors. This block ensures the performance of the following maneuvers: First speed, including forward and backward (first speed), and second speed, including turn to the left, turn to the right on a spot, and turn to the right while in motion.
When launched, the braking block ensures the activation of the electromagnet windings simultaneously with the activation of the motors in accordance with the algorithm described above, which activates forced and hold-in windings. When the chassis is stopped, this block turns off the power from electric motors, which switch to dynamic braking mode; this block deactivates the electromagnets as well.
The stopping block is made on the electromagnetic relay. This block sends a signal to the block of movement to stop the chassis when the stop command is received from Earth through the on-board locomotion safety equipment.
The locomotion safety group ensures the generation of commands for automatic stop of the chassis in accordance with the concept discussed above. In this case, Earth receives telemetry information required to analyze the causes of emergency stop.
The automatic control circuit also includes blocks of start and stop modes and the dosing rotation block, which imposes several restrictions on possible emotional actions of the driver. Restrictions can be released when a relevant decision of the crew commander is made. The start-stop mode block provides a dosage of continuous movement time. The dosing rotation unit produces a stop signal when a predetermined rotation angle of the chassis is reached.
Safety movement automation does not allow the activation of the second speed from rest and movement with released current protection. Thus, the system turns on spot and executes a reverse motion with a measuring wheel lowered to the ground. As for increased emergency slipping, the operators can assess the danger of this phenomenon when deciphering the telemetry information on travel and wheel rotation rate.
The control and measurement group consists of blocks that measure wheel rotations, trim and list, currents, and traction motor temperatures.
The speed sensors of the third and sixth wheel rotation measured the rotation rate; the sensors of the other wheels provided information about rotation. All these sensors were of an induction type according to their structure. Temperature was measured in the motor stator housing. DKD was an aviation gyroscope with three degrees of freedom and pendulum correction.
All information was transmitted to Earth by telemetric channels and used to not only diagnose the condition and control of chassis subsystem operation and lunar rover drive tasks, but also for scientific purposes. Thus, the information from DKD allowed the construction of a contour map along the route of movement.
Manufacturing and delivery of the flight model of BASh in Lavochkin Plant as well as delivery of electromechanical units and appliances became a notable testimony to the growth of the technological culture of the enterprise and the improvement of its infrastructure with modern equipment. This was a significant achievement [6] of chief engineers M. P. Atamanov and A. Y. Belyakov; production supervisor K. B. Chernov; his deputy F. M. Nevelev; heads of technological services V. P. Eremeev, E. B. Bumagin, and G. V. Lobanov; heads of the workshops Y. M. Kroner and V. F. Kompaneyets; and site supervisors E. N. Kukushkin and V. A. Kozyrev.
Work devoted to the space topics attracted highly qualified electrical and radio engineers and workers of various professions. Among them were B. P. Sharov, V. G. Pogorely, A. L. Belyshev, L. M. Erenpreis, S. N. Lebedev, S. Y. Kushnarenko, and M. A. Lobastov.
PrOP (Fig. 19), a part of the chassis, is one of the locomotion safety subsystem components [2,4]. It is a scientific tool for studying the mechanical properties of lunar soil in situ.
 | Fig.19 Cross-country ability assessment device in transport position (courtesy of VNIITransmash)1−Upper head; 2−Measuring wheel movement mechanism; 3−Measuring (free rolling) wheel; 4−Lower head; 5−Cone and blade die; 6−Upper wheel movement mechanism |
The upper head accommodates electromechanical actuators for independent vertical movement of the lower head and the measuring wheel as well as the die movement sensor. The lower head includes a mechanism to rotate the die, sump force sensors, and torque sensors. Both heads are installed with additional devices that provide the capability of a program work: End position sensors and limiters of axial and tangential loads.
The mechanism of lowering the measuring wheel provides free vertical movement when driving over bumps. The sensor of this mechanism detects the position of the wheel toward the upper head.
The introduction of the die into the soil is conducted either to a limit determined by its design or until a critical introduction force. Thin die blades almost do not distort the results of bearing capacity measurements, which involve the ratio of implementation efforts to the cross-sectional area of the cone at the interface. Afterward, the movement of the lower head stops and the die rotation mechanism is activated.
According to the design, rotation is conducted either until the maximum possible angle of 90° is reached or until the maximum possible torque on the die is measured. This rotation reflects the internal friction and cohesion of soil particles. The influence of cone friction in soil on these measurements is negligible because of stability that is not dependent on the angle of the die rotation.
Measurement of the mechanical properties of soil is conducted with the measuring wheel lowered to the ground; this allows the determination of the distance to the ground level as well as the start and depth of die penetration. For more accurate decoding of the measurement results by laboratory calibration, temperature control is performed; the motor devices supply voltage.
The main technical characteristics of PrOP are as follows: The maximum force of die introduction is 230 N, the die penetration depth is up to 100 mm, the torque on the die is up to 5 N·m, the diameter of the die cone base is 50 mm, the cone height is 44 mm, blade diameter is 70 mm, and the period of one measurement cycle is 1 min.
Manufacturing of PrOP, developed in the design bureau of precision mechanics led by P. N. Brodsky, proved to be a challenge for the pilot production of the tank institute. Some parts and assemblies of the device were more appropriate for a watch factory. The flagship of that period, the Leningrad Optical Mechanics Association, was involved in the manufacturing. However, the fitters-assemblers of the manufacturing site, namely, B. P. Zarubin, V. P. Kryukovets, and N. M. Dmitriev, were the original co-authors of the design. The modern supply of the device would have been impossible without their participation.
According to preliminary estimates, grounds with a bearing capacity of less than 5 kPa could be critical to lunar rovers, the depth gauges of which could be up to 300 mm. According to the measurement results of PrOP, such soils were absent on the movement tracks of the Soviet lunar rovers. This result is consistent with the overall results of the operation of vehicles on the Moon; both lunar rovers did not lose mobility because of the lack of cross-country capability.
The scientific side of the PrOP operation proved to be efficient and has not lost its relevance up to the present time. For example, analyzing the results of measurements on different sections of Lunokhod-1 movement routes, V. V. Gromov obtained an informative picture of the inhomogeneous upper layer of lunar soil (Fig. 20 [4]). Future builders of lunar bases will still cite these data.
 | Fig.20 Dependence of the introduction efforts of the depth and type of a surface cover [4] p−Force/N; H−Immersion depth/cm; 1−Stone destruction; 2−Yield of solid rocks; 3−Soil with increased porosity; 4−Homogeneous soil layer; 5−Layer of loose soil on a solid foundation; 6−Homogeneoues extremely loose soil |
In late 1967 to early 1968, the personnel of the space department completed delivery in Lavochkin Plant of the first flight model (LO) with a self-propelled chassis. The head representative of the client, E. A. Sekerzhitsky, warned that he would not allow the delivery, even if the results of tests and checks are more than positive, without a calculation report and a theoretical analysis of compliance with the requirements of the technical brief and justification of all components of the chassis as a whole.
The calculation and theoretical sector of P. S . Sologub’s general machine laboratory dealt with traction, dynamic characteristics, and selection of a traction drive (A. F. Kudryavtsev), fluctuations of a sprung portion and run smoothness (F. P. Shpak), stability against overturning (E. V. Avotin), thermal modes and thermal protection (O. V. Minin, V. N. Plokhikh), as well as the study of terrain and reliability calculations (I. S. Bolhovitinov). The results of the calculations comprised the first volume of the report.
The second volume was devoted to the calculation and theoretical justification of the chassis and its component operation modes, selection of suspension, strength, and other calculations of the supporting structure, suspension, drive, and brake, as well as calculation confirmation of the other technical brief requirements. The first volume described a wheelbase, track, and unsprung and sprung masses of the lunar rover; the second volume dealt with the gear-tooth calculations and calculations of critical parts and fasteners.
The report was called “Calculation and theoretical justification of the ‘C’ device working capacity in lunar operation conditions” and included the calculation and explanatory note for the project with the number 67252-RPG-1. The head of the design bureau, heads of design, and engineering teams and designers took part in its preparation. The head of RTS, F. P. Shpak, was a brilliant coordinator of this significant work, summing up the result of three to four years of creative research for the entire team. The following is an initial fragment of the annotation to the report.
This report presents the results of calculations for the chassis and its components for compliance with the requirements of their functioning and the requirements of the Technical Specification given by S. A. Lavochkin Plant dated of March 24, 1967, Technical Specification approval protocol dated of July 21, 1961 and Technical Conditions for the chassis products E-8.
The abovementioned calculations were conducted analytically both by sliding rules and by using first Soviet computers. In cases where one or the other calculation mode of the chassis operation was simulated on Earth, the calculation results were compared with those of tests to evaluate the accuracy of the calculation methods.
The report was released in 1968 and approved by the director, V. S. Starovoitov. He is better known as the father of the human rights activist Galina Vasilyevna Starovoitova who was assassinated in 1998.
Relatively simple preliminary testing of individual mechanical, electromechanical, and electronic components in air, under normal climatic conditions, in idle mode, and under load were conducted in the areas where these units were created. Direct developers prepared tools for testing, wrote techniques, and frequently performed the tests. However, special stands and laboratories were required for complex testing of the complex assemblies and assemblies for resistance to such influences as vibration, shock, and transport congestion. Vacuum and temperature create a weak gravitational field. Another KB of stand equipment was created for the design of stand and test equipment.
One development (A. A. Golubtsov, I. E. Kiselev) was a PSI stand for acceptance testing of the chassis on which, under normal climatic conditions and the Earth’s gravity, one could verify the performance of all teams to create all situations on the road and obtain all the full-time telemetry information (Fig. 21).
 | Fig.21 Self-propelled chassis of the rover on PSI stand (courtesy of VNIITransmash) |
In 1965, the institute developed a laboratory that was involved in organizing and manufacturing mechanical testing units of motor-in-wheels and BASh. The first laboratory chiefs R. D. Tetelbaum and G. S. Zhartovskiy were essential to this process.
In the thermal vacuum laboratory, stands were continuously equipped. These stands were designed by V. V. Grinev, S. V. Gurkalo, and V. O. Tokarev. Laboratory head and leading experts V. M. Tarasov, L. O. Vaysfeld, V. G. Sobolev, S. A. Shepel, and V. I. Egorov were convinced and thereafter persuaded the representatives of the customer that if the vacuum created in the chamber was “pure”, it need not match the space on the degree of discharge. In terms of influence on the processes of friction, achieving 0.001 mm of mercury is sufficient.
Understanding of the laboratory staff’s problems and ways to obtain a “pure” vacuum as well as collaboration with leading experts in the field of Kharkov Physico-Technical Institute of Low Temperature (G. N. Gamulya), Moscow Institute of Engineering (Institut Mashinovedeniya: IMASH, A. Silin, E. N. Duhovskoy, Yu. N. Drozdov), Leningrad Polytechnic Institute (LPI, L. N. Rozanov), significantly simplified the test procedure. A few new ideas in terms of obtaining such a “pure” vacuum by applying vacuum sorption traps with a short cycle of regeneration were offered by the graduate of the Department “Automatics” of LPI (A. Kuzenits) [31].
The abovementioned facility construction to test the performance and life of all the many pairs of friction block motor-in-wheels in a vacuum (Fig. 22 [4]) was highly successful. The entire installation and the test object and loader were mounted on the flange chamber, easily accessible for installation and inspection. The functions of the loader were performed by the elements of the test object, i.e., torsion bar suspension and traction drive wheels. In Fig. 22, we can see a half-wheel motor unit fixed to the inner side of the flange using a simulator chamber regular bracket. In the hub, the wheel is instead a disc, which interacts with the same fixed flange abutment; this disc is fixed eccentrically relative to the axis of rotation. A PTFE lining is fixed on the interacting surface of a stop in a form of an arc segment.
 | Fig.22 Installation of the test object and loader on the inside part of the TEC-250 chamber flange [4] |
The stationary torsion bar suspension presses the stop disk, thereby loading the hub bearings and balance. The bearings cup torsion is inserted into the simulator bracket. During commands for locomotion to the wheel hub, torque is further applied by friction force at the point of contact with the disc loading plate. Because of the eccentricity, the forces acting on the bearing suspension and the torque acting on all gearing and motor drive vary sinusoidally.
VNII-100 staff V. N. Plohih and D. Ya. Klyatskin completed the final stage of complex thermal vacuum tests as part of the chassis of the thermal equivalent of the entire spacecraft. The tests took place in the suburbs of Moscow, where a large chamber allowed the simultaneous simulation of all the factors of space in Earth’s gravity.
In the laboratory of running trials, specialists searched for simple unloading systems available not only for closed underground channels but also for natural polygons. Tests with a single wheel were conducted in the ground channel set in a flying laboratory, with lunar gravity showing some influence of this factor on the nature of the propulsion interaction with soil. However, this effect was not determinative.
From the standpoint of the theory of similarity, the problem of simulating the gravitational field of the Moon was considered by V. V. Gromov and V. N. Petriga [8]. They concluded that in practice, combining different types of running simulation models using large-scale dynamically and statically similar models is advisable. However, large-scale models are, as a rule, only for checking kinematics. For experimental testing of a self-propelled chassis and its components, a real chassis and drives should be utilized.
Consequently, the geometry of full-sized models needs to be discussed. To comply with static scaling, the weight of the ground test mule must roughly correspond to the actual weight of the lunar rover on the Moon. In addition, coordinates of the center of mass should exactly match those of the test mule and the real lunar rover. Such models with a small error, which should be directed toward tightening the real mode, are able to solve the overwhelming majority of tasks of running tests on any natural ranges; thus, unloading is not required.
Minor dynamic processes occurring in automatic rovers, such as acceleration, braking, and a shot in an insurmountable obstacle, can be investigated in the laboratory on dynamically similar test mules. Unloading in the laboratory and at short distances, which may well be arranged on a flat surface, is not a huge problem. In addition, the dynamic processes can be reliably explored in a mathematical mode [5].
The resource way of the test mule of the lunar rover was practiced on an unpaved annular channel closed polygon. Some dynamic situations were simulated using a partially dynamically similar test mule that imitated only a real moment of inertia about the transverse axis of the rover (Fig. 23 [3]).
 | Fig.23 Fragment of the annular channel of soil with rail track for truck maintenance and full-size partially dynamically similar test mule of the lunar rover [3] |
To conduct the most important tests to determine the maximum angle of lifting and towing, which were coupling characteristics of the chassis as a function of the coefficient of slipping wheels, the stand “variable bias” was used and tested on a horizontal platform with adjustable traction on the hook (Fig. 24) [8].
 | Fig.24 Ways to simulate the center of gravity of such static full-size mock-ups: Additional mass 1 at the top of the mast, increasing the height of the point of application of thrust on the hook [8] |
Real revolution began with the organization based on economic agreements with the Institute of Volcanology. Field trials were conducted in areas of recent volcanic eruptions in Kamchatka near Kliuchi then in Kozirevsk settlements. The diversity of landforms and mechanical properties of the soil, even in a relatively small area near the field point, opened unprecedented opportunities of full running trials on a close analogue of lunar soil.
Here, in 1969 to 1971 during running trials in the area of Shiveluch and Tolbachik, the high-traction coupling characteristics of the self-propelled chassis of the Soviet lunar rover were confirmed (Fig. 25 [37]).
The special remote control of moon rovers was one part of the multi-faceted objective to develop the self-propelled chassis. Formation of the technical requirements for all equipment involved in implementing the function of the movement apparatus on the lunar surface was one of the main tasks of the general machines laboratory. Its KB included B. M. Lubenko, A. V. Mitskevich, L. N. Polyakov, and I. F. Kazhukalo.
This position was mainly shared by chief designer of rovers G. N. Babakin and leading experts at Lavochkin Plant. Thus, a group of soldiers selected for training to drive the lunar rover on the Moon was sent to the institute on the initiative of Lavochkin Plant. The purpose of their visit was to familiarize themselves with the design and proposed methods of traffic control of the self-propelled chassis.
On the part of VNII-100, the development of the driving method and driver training was led by Yu. P. Kitlyash, who became close with L. N. Polyakov [18]. Kitlyash painted a console configuration of the driver and the overall layout of the crew in the control room, which was then placed in the Deep Space Communication Center (Tzentr Dalneyi Kosmicheskoi Svyazi: TsDKS) near Simferopol , Crimea (Fig. 26). With the light hand of Lev Nikolaevich, this figure became the basis of the industrial production of the panels (Fig. 27); the illustration is now stored in museums in Khimki, Moscow, and St. Petersburg.
 | Fig.26 Remote control drawing of L. N. Polyakov (courtesy of VNIITransmash) |
 | Fig.27 Driver V. G. Dovgan controlling remotely at TsDKC (courtesy of V. G. Dovgan) |
Then, a group of experts from the Institute led by P. S. Sologub participated in the development of methods and practical skills in the process of driving in a remote test site near Simferopol [32]. This process was a preparation for the main events for Luna-17 and Lunokhod-1: Landing and beginning of movement on the lunar surface.
In July 1968, the institute delivered the first flight model of the self-propelled chassis for the first lunar rover. The months, weeks, and days prior to delivery were a hectic period not only for the team of space studies, the pilot production institute, and department chief technologist but also for various scientific-technical departments and support services of the institute.
Three shifts in key scientific and industrial units were organized. Several particularly in-demand employees had to work round the clock. Rollaway beds could be seen in the working areas. The next time an intense situation occurred in the Institute was in the summer of 1986 before sending tracked and wheeled robotic systems to Chernobyl for clearing and decontamination of the territory and roofs of the Chernobyl Nuclear Power Plant. These complexes could not play a decisive role in the elimination of the consequences of the largest man-made disaster, but their use reduced the number of people working in hazardous areas by hundreds of thousands.
After the delivery of the chassis center of gravity, work on the assembly and inspection of the rover was moved to Khimki. With the participation of experts from VNII-100, assembly of the lunar rover was completed, and the necessary checks were conducted. Even now, photos of the rover, which was introduced to the world in 1970, continues to attract designers. Designer D. V. Sidorov, a Polytechnical University graduate, developed models of Lunokhod-1 based on the photos (Fig. 28) [38,39].
 | Fig.28 Lunokhod-1, 3D model. (a) Front view; (b) rear view (design by D. V. Sidorov)1−Radiator of a cold contour; 2−Gain antenna (ONA); 3−ONA drives; 4−Corner reflector; 5−Camera slow-scan TV; 6−Device for determining the chemical composition of the soil (RIFMA); 7−Propelled chassis, starboard; 8−Container; 9−Gauge of the lunar vertical; 10−Panoramic camera of vertical scanning; 11−Solar panel; 12−Wide-beam antenna; 13−A cover of the pressurized compartment; 14−Lifting drive pressurized compartment cover; 15−Whip antenna (4 pieces); 16−Radioisotope heater unit; 17−Screen block heater; 18−The ninth freely rolling (dimensional) wheel; 19−Mechanical penetrometer (device for cross-country ability evaluation); 20−A bearing pallet of the container; 21−Self-propelled chassis, left side; 22−Panoramic camera of horizontal scanning |
At VNII-100, work continued on the production of LO-2, the second flight model. It would be needed soon. February 19, 1969 marked the launch of the first lunar rover, which ended in an accident of rocket “Proton-K” in the first minute of the flight. A. L. Kemurdjian and V. S. Starovoitov were present at the launch site and saw how the rocket was automatically blown-up after the launch failure [18].
The wreckage of the station and lunar rover were gathered in the desert near the Baikonur Cosmodrome. The motor blocks, i.e., the wheels and a block of automatic self-propelled chassis rover, were found undamaged. The pyrotechnic components of the release mechanism also withstood the severe test. Mechanisms were dismantled, and the preserved blocks were utilized in the construction of navigation models for different purposes.
After this incident, the leaders of the Soviet moon program, in anticipation of the expected expedition of Apollo 11, prioritized the delivery of lunar soil to Earth [13,17]. Unified-platform automatic lunar stations (ALS) were in the emergency order to accommodate the modified soil sampling device (Grunto-Zabornoe Ustroistvo: GZU) and return to the rocket to save the device.
The soft landing of previous Soviet moon stations Luna-9 and Luna-13 did not require the precise alignment of devices on the descent trajectory and was protected by the cushioning properties of quickly inflatable balloons. By contrast, the new ALS was created based on a unified landing platform equipped with a braking unit with a soft landing system. Instrumentation provides guidance in all areas of the station flight control and management of the parameters of the trajectory and speed of descent and landing. Thus, the adaptation of the station under the new payload was not an easy task.
The rate of work can be judged by the following fact. On June 14, 1969, just four months after the accident at the Baikonur Cosmodrome, the launch of the first modified ALS with return onboard the rocket was held. However, the start was again unsuccessful. The fourth stage of the rocket, which was to bring the head part to a geocentric orbit, did not receive the appropriate commands to run [17].
Meanwhile, the month before, in May 1969, the Apollo 10 spacecraft successfully placed the flight orbiter Apollo 8 in lunar orbit.
In addition to the above achievements, in that same month of May, all necessary maneuvers to rebuild compartments for the autonomous flight of the lunar module with two astronauts on board and subsequent docking with the orbital unit for return to Earth were fulfilled in a selenocentric orbit. Experts from different countries held their breath; it was clear that the next step would be the landing of a man on the Moon and return of its soil to Earth.
By this time, the Soviet Union already realized that the Americans would be the first to land a man to the Moon. Nevertheless, the first return of lunar soil could still be achieved with the help of Soviet machines. Perhaps no other event could highlight the intense moon race between the USSR and the United States than the key events that occurred at the launch sites of the Earth and the Moon in July 1969.
At first, Baikonur was ahead. On July 13, 1969, the second launch with the ALS modified landing platform called Luna-15 was executed. In February 1969, the weight of the station in geocentric orbit was 5700 kg; it was able to secure the return of lunar soil to Earth. This launch was a success; the station went on the first flight trajectory to the Moon and then to lunar orbit.
Three days later, on July 16, 1969, the start of the expedition of Apollo 11 was made from the John F. Kennedy Space Center at Cape Canaveral. The American spacecraft was flying to the Moon, and the Soviet craft was already maneuvering in the orbit of its artificial satellite. Two corrections of the Luna-15 orbit parameters were made [17]. We can assume that this was done to ensure favorable conditions for soft landing on the Moon.
The delay in the landing of Luna-15 led to a change in the development of events. On July 20, the lunar module expedition Apollo 11 made the first successful landing on the Moon. On July 21, the astronaut Neil Armstrong became the first human to step on lunar soil .
On the same day, July 21, ALS Luna-15 landed. Automatic stations need much less time for taking soil than astronauts do. After all, only a few grams of ethereal substance are required in a flight back to Earth. The Apollo 11 expedition planned to spend over 20 hours on the Moon. Therefore, the hope that Luna-15 would be the first to return lunar soil to Earth was still reasonable. However, the landing of ALS Luna-15 occurred in emergency mode.
This emergency occurred after the station had already begun to climb to orbit and, according to on-board instrumentation, was located at an altitude of 2.5 km. At this altitude, the main engine switched off; the estimated time needed for it to work was 267.3 s. However, at 237 s, the signal suddenly disappeared although the parameters of all systems were normal up to this point [13]. This alignment led operators to assume a collision with a lunar mountain station. This could occur if the error trajectory measurements were up to 45 km in the direction of flight and 15 km away from the calculated orbital plane. After realizing the accident of station Luna-15, intrigue vanished. On July 24, 1969, the Americans finished alone, bringing with them 24.9 kg of lunar soil to Earth.
Afterward, the Soviet Union had three other unsuccessful attempts to deliver lunar soil with the help of three identical stations. In all these cases, the accidents occurred in the early stages of flight, no later than launching into geocentric orbit. Only on September 12, 1970 did the start of ALS Luna-16 lead to the successful and automatic delivery of lunar soil to Earth. This was achieved after Lavochkin Plant and related business teams analyzed and addressed the causes of the previous accidents.
Two months later, on November 17, 1970 just after the Luna-16 success, Luna-17 also made a soft landing near Mare Imbrium at coordinates 34º47ʹ west longitude and 38º24ʹ north latitude. The USSR once again advanced in the field of lunar robots [13,17].
At 9 h 27 min 7 s, the first command to move forward was sent from Earth [32]. Lunokhod-1 alighted the ramp and was the first rover on the lunar surface (Fig. 29 [1]).
 | Fig.29 Fragment of the panorama (horizontal scan) of the Moon near the landing station Luna-17 (bright spot on the horizon at the end of the track) and the first tracks on the Moon [1] |
The reaction of the domestic and foreign public to this event was unusually strong, benevolent, and sometimes simply ecstatic. This reaction intensified when the space robot survived the first moon night and continued research on the second lunar day. The long hard work of huge collectives, including a relatively small group of employees of VNII-100, was globally recognized as a success.
To participate in the Operational Control of Lunokhod-1, the staff of the institute were sent to Simferopol headed by P. S. Sologub. A crew of five soldiers conducted direct driving. Extensive information about the history and work of the crew is available in Ref. [32].
The following scientific instruments and equipment were installed onboard Lunokhod-1 (Fig. 28): X-ray spectrometer “RIFMA” to study the chemical composition of the soil; angled laser reflector to support the lunar laser ranging from ground-based radiation sources; four board telephotometer vertical and horizontal scans (two per side); patency assessment instrument-mechanical penetrometer to study the physical and mechanical properties of the soil; radiometric equipment (dosimeter) to study cosmic rays of low energy; and collimating X-ray telescope to study the cosmic X-ray radiation. These devices are not shown in Fig. 28.
To study the topography and thermal state of the soil along the route, the official data from the onboard slow-scan television cameras and the sensors of trim and list as well as the set of lunar rover temperature sensors were used for analysis.
Almost throughout the operation of Lunokhod-1 on the Moon, the operation of the self-propelled chassis and scientific instruments occurred as planned. However, unexpected problems were still encountered. On the first lunar day, during the 4 h session with the command “Turn 20”, the flight engineer reported an increase in current consumption. The cause was identified quickly. It was the breaking of electric circuit windings in all eight electromagnets, which made disabling the brakes while driving impossible. BASh did not comply with the restrictions on working hours under high current.
Despite this serious failure, the chassis retained its mobility because the brake timing was minimal, and all engines had a good reserve of power. When driving at a low-speed current, the feed wheels could exceed the nominal values only on slopes over 15°. However, at high-speed current traction, the motors could exceed the limits even on relatively flat ground. Therefore, this mode and turns of Lunokhod-1 in movement were not used.
Lunokhod-1 moved and provided research for 11 lunar days, keeping operation after each of the 10 lunar nights. The record of its active existence on the Moon is still unbeaten (Table 1).
 | Tab.1 Main design and performance characteristics |
On January 16, 1973, station Luna-21 landed on the bottom of Lemonnier, an ancient crater 60 km in diameter located on the edge of the Sea of Serenity at coordinates 26°03ʹ W and 30°22ʹ E. On the same day, Lunokhod-2 began its operations, equipped with an additional, third chamber slow-scan television mounted on a special bracket at a height of 1.5 m. This camera improved the survey area for the crew. A magnetometer to study variations in the weak magnetic field of the Moon on the route and an astrophotometer to study the lunar sky luminosity were additionally installed onboard Lunokhod-2.
The defect of the BASh scheme was eliminated, and reliable operation of the electromagnet friction of brakes was provided. Therefore, both the second speed and turns in motion were used for Lunokhod-2.
The creation and successful operation of Lunokhod-1, which provided a huge amount of scientific information gathered throughout its movements, gave rise to a new direction in space technology. Mobile automatic and remote-controlled lunar and Martian laboratories, also known as planet rovers, became an integral part of new research programs for celestial bodies. The word “rover” entered the international lexicon without translation, similar to the word “sputnik”. The first lunar rover will be remembered as much as the first car, train, ship, and airplane.
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