Academician Sergey Alekseyevich KHristianovich was the founder and the first director of ITAM of the Siberian Branch, Russian Academy of Science. Though "the Siberian period" takes relatively little time in the life of Sergey Alekseyevich, the significance of his work in the field of development of Siberian science is great. S.A.KHristianovich is the one whose circle of interests is extraordinary wide and manifold. Namely it is hydro- and aerodynamics, the theory of filtration and plasticity, the rock mechanics, essentially new engine installations and many other things. Sergey Alekseyevich has come to Siberia in the age of 50 years when he had already accumulated a considerable experience in organizational issues, the big scientific potential and at the same time he had also the energy and striving for implementation of his plans.

S.A.KHristianovich's biography contains many events. Sergey Alekseyevich now qualifies as a long-liver. He was born on November 9 (on October 27 old style), 1908 in Petersburg. Sergey Alekseyevich wrote in his curriculum vitae: "parents are noblemen-landowners of the Oryol province. In 1920 parents left with Denikin's White army, which had occupied Oryol, fell ill of typhus in Rostov and died. He was homeless, then lived with his tutor, prof. D.I.Ilovaiskii in Rostov, and since 1923, at his aunt M.N.Bek in Leningrad." After he left high school in 1925, Sergey did not made at once the choice for the exact sciences. At first he entered the anthropological branch of geographical faculty of LSU and only then he transferred to phys-math. In 1930 he graduated from the university, mathematical branch.

S.A.KHristianovich has got fundamental knowledge on the selected speciality due to such tutors as V.I.Smirnov, N.M.Gyunter, N.E.Kochin, and his scientific outlook was shaped due to influence of such extraordinary "messmates" as L.V.Kantorovich, S.L.Sobolev, V.A.Ambartsumyan, S.G.Mihlin, etc. Upon graduation from LSU Sergey Alekseyevich began his scientific biography from junior scientist in the State hydrological institute. Five year work result in this institute is the monograph "Some new aspects of mechanics of the continuum" written in the co-authorship with S.G.Mihlin and B.B.Devison (the book has been published in 1938 under N.E.Kochin's edition).

In 1935 S.A.KHristianovich moved to Moscow and entered the doctoral studies in V.A.Steklov Mathematical institute of AS USSR. A year later he made an article about the distribution of tension in the plastic band around the aperture limited by an arbitrary closed loop. This work has drawn attention of experts including foreign ones and has promptly gained a broad popularity. In 1938 S.A.KHristianovich has finished doctoral studies, having defended at once two theses for a doctor's degree - in physical and mathematical science and in engineering.

In January 1939 31-year Khristianovich has been elected corresponding member of AS USSR in the Department of engineering. Together with group of experts-mechanics of Mathematical institute, S.A.KHristianovich takes the position in the Institute of mechanics of AS USSR, where in 1939-1940 he works on theoretical problems of filtration, and also the problems of slow infiltration of a fluid through the porous medium. In opinion of experts, S.A.KHristianovich's work "Movement of the subsoil waters which do not comply to Darcy law" went ahead its time substantially. Quarter of a century later this research has underlain the fundamentals of computational methods for visco-plastic oil motion. The other work of Khristianovich "About the motion of the bubbled up fluid in porous rocks" was also of great importance for practical use in the oil-extracting industry.

In the Institute of mechanics S.A.KHristianovich held a post of the deputy director. And sudden was the transfer to the Central aerohydrodynamical institute named by N.E.Zhukovsky (CAHI) to the position of the head of high-speed aerodynamics laboratory. The reason for that was the time: the presentiment of close war has forced many scientists to change peaceful research subjects to defensive ones.

In the early 40's CAHI comprised a scientific institution of developed traditions and strong collective of scientists and engineers. Oustanding scientists such as S.A.Chaplygin, M.V.Keldysh, N.E.Kochin, L.S.Leibenzon, A.I.Nekrasov, F.I.Frankl etc. worked here. One of the institute traditions was the seminars on which scientific results and new problems were discussed. It was not easy to show one's worth in such collective. Only scientists generating new ideas and finding original decisions of tasks in view could figure the recognition of colleagues. Khristianovich managed to deserve such recognition. As the proof of it there is such an example: S.A.Chaplygin was named "SACH" in CAHI, while S.A.KHristianovich has got a nickname "SAKH" (that means also the mean aerodynamic chord as Russian abbreviation of the term).

Works of Khristianovich on the eve and during the war, due to development of high-speed aircrafts, have been devoted to the problems of aerodynamics. The basic goal of theoretical and experimental research was increase of airplanes flight speed that, in its turn, was predominantly connected with the decrease of drag.

In 1940, in his work "The streamlining of bodies at the high subsonic speeds" S.A.KHristianovich has offered the effective mathematical approach in the infinite-span wing theory for the compressible stream. It has allowed studying the streamlining of air structures at the high subsonic speeds of flight, calculating the profile pressure distribution and determining the lift created by wing. In 1941, S.A.KHristianovich's article "About supersonic motions of gas" has been published in which the classification of supersonic currents and their research from the point of view of the possible existence of potential motion were given.

Yet during the war beginning the speeds of our airplanes have grown in such extent that to choose the correct aerodynamic forms it was necessary to solve the problems related with taking into account the compressibility of air, which was negligible at smaller speeds of flight. On the basis of S.A.KHristianovich's theoretical works on the airflow of bodies by the stream of high subsonic speeds there have been determined the requirements necessary to choose the wing shape for the least drag.

In the article "On the supersonic gas motions" the problem of transition of steady flow over the sound speed has been also put for the first time. As well as in a number of his other works, Khristianovich has offered such decision, which came ahead that time and seemed rather disputable to some contemporaries. But later on it was on the basis of this work that the direction exploring the reasons of destruction of potential flows and formation of shock waves in the local supersonic bands (A.A.Nikolsky, G.I.Taganov) has appeared.

During his work in CAHI Khristianovich dealt with the problems favourable in the scientific aspect and extremely necessary for the country defence. In 1943 in the co-authorship with V.Astrov, L.Levin, E.Pavlov Khristianovich writes an article "On calculation of Laval nozzles", in which the result about the termination of the critical stream by a direct transition line that is simultaneously the characteristic of the equations of gas dynamics was given for the first time. Later L.V.Ovsyannikov stringently proved this fact. Results of this work are of practical importance until now in designing the inlet segments of real nozzles. Publications of a wartime include such works as "About a wave resistance" (together with Ya.M.Serebriisky), "Compressibility effect (the Mach effect) on the inductive speeds of a wing and the airscrew" (together with L.A.Simonov), "About ejector calculation", etc.

Sergey Alekseyevich Khristianovich (1943 г.)

In 1943, in his incomplete 35 years, Sergey Alekseyevich has been elected the academician. It was recognition of his successful scientific work in CAHI. In opinion of people who know S.A.KHristianovich well, the years of work in CAHI were the time of his creative boom. Scientific achievements of Khristianovich would not be so significant without support of the nearest colleagues in the laboratory: A.A.Dorodnitsyn, M.D.Millionshchikov, G.P.Sviscev, V.V.Struminskii, L.G.Loitsyanskii, A.A.Nikolskii and many others. Khristianovich managed to unite in one group the talented theorists, experimenters and broadly-minded engineers.

Carrying out the widespread research on aerodynamics of the high speeds aimed to the prompt application to industry required to create entirely new experimental support. In 1943 the main wind tunnel Т-106 for high subsonic speeds, in which the flow with increased Reynolds's numbers was simulated, has been put into operation in CAHI laboratory of high speeds. In 1944-1945 the new design of the tunnel Т-112 for testing of wings and fuselages of airplanes has been created.

What was the scientific authority of S.A.KHristianovich in CAHI, one can figure from rather interesting document published recently in "Historical archive" magazine (N 2, 1996). It is the reference of People's Commissariat of national security of the USSR about scientific and public work of the full members of AS USSR, drawn up in July 1945. Here you see the literally exact characteristic of Khristianovich: "Khristianovich Sergey Alekseyevich, born in 1908, Russian, non-party, the academician since 1943, the winner of the Stalin premium, the scientific supervisor of department of mechanics in the Institute of mathematics of the Academy of Sciences of the USSR, the professor of the Moscow aviation institute, deputy chief of CAHI, the winner of N.E.Zhukovsky premium. An order bearer. The mechanic in aerodynamics. He is known for the fine complete works in the field of hydraulics (of rivers), aerodynamics of the high speeds, the theory of plasticity and oil mechanics. He is one of the outstanding disciples and followers of Russian experts in aerodynamics, N.E.Zhukovsky and S.A.Chaplygin. Universally recognized in the Union, expert in aerodynamics and hydrodynamics. He supervises personally the great research defensive works in CAHI. Khristianovich is at the peak of his creative power, has much organizational talent. He has a huge authority among scientists-mechanics and mathematicians. Sociable, modest in life and work. He works much and he is exacting to his subordinates. He is held in respect among workers of CAHI".

In 1953 S.A.KHristianovich was elected on a position of the academician-secretary of the Branch of engineering of AS USSR on which he remained till 1956. Sergey Alekseyevich works at the same time in the Institute of chemical physics and Institute of oil of AS USSR. Scientific issues he developed during this period have been connected with gas-dynamic problems of nuclear explosion, with the theory of hydraulic break of a petroliferous seam, with studying of sudden outbursts of coal and gas in coal seams, etc.

S.A.KHristianovich, being intensively engaged in scientific and applied research, did not stand away from organizational problems of development of science. Such problems accumulated in abundance in the national scientific and technological system up to the middle 50's. Under conditions of political "thaw" the problems that were not discussed earlier came into being at the assemblies in the Academy of Sciences of the USSR: about need in free discussions, about overcoming of monopolism in scientific research, etc. Many scientists appeared in print about the necessity of interdisciplinary research development and more active application of scientific studies to national economy.

Representatives of this group of scientists were academicians M.A.Lavryentyev, S.A.KHristianovich, S.L.Sobolev. Here is how S.L.Sobolev recalled those far away events: "In 1956 three of us, young (so-called!) people, one of which was 56, and two others were 48, met at the summer residence, of one's, or of another's, in the housing estate of Mozzhinka, which was a gift of the government to academicians in the end of 40's. While meeting, we thought of how to raise the scientific and technical potential of our Native land, what is necessary to make to convert it to mighty power, which does not fear anything, and which will grow adequately to its potentialities. The way to this prosperity we saw in that all over our immense Native land were arranged the powerful scientific centres and they were put closer to the local industry and resources".

	The general view of the building of wind tunnels and erected compressor station (1962-1963)

The combined intelligence of three mathematicians like computer has counted the optimum variant for those conditions to put into practice the plan of creation of a powerful scientific centre in Siberia. They began unusual business in its novelty and scale; they went on through breaking the stereotypes in the matter of the organization of science, having decided actually to create an Academy inside the Academy. To substantiate such a step it was necessary to find the correct algorithm, to take into account a set of factors - economic, political, intrascientific. The idea could not be brought about without support of known scientists.

S.A.KHristianovich took the most active part in this new business from the very beginning. Early in 1956, when discussion of the project of development directives for the national economy of the USSR in 1956-1960 was set up in print, he has published, together with M.A.Lavrentyev and S.A.Lebedev, an article "Urgent problems of the organization of scientific work" in which it was offered to reconsider a network of institutes and higher education institutions of the country with the purpose of allocating them more rationally. The following step of academicians was an appeal to the government offering to create in the east of the USSR a centre of science which could be compared with the centres of the European part by the scale of its activity. Drawing up the project of the new centre of science took into account the circumstance that the problem of the most rapid development of Siberia and the Far East, from Ural Mountains up to the coast of Pacific ocean had been discussed at the XX congress of the CPSU, and the appropriate tasks had been put forward for scientific community.

On May 18, 1957 the country government made the decision for creation of Siberian branch of AS USSR. Organizers-academicians had to make much efforts and eloquence in the campaign among the known scientists for getting over together with their disciples and colleagues in the new centre of science near Novosibirsk, the academgorodok. S.A.KHristianovich became the chief deputy of M.A.Lavrentyev, the Chairman of SB AS USSR. The management in organizing of the Novosibirsk scientific centre designing and construction has been placed on him, together with the future centres of science in Krasnoyarsk, Irkutsk, Ulan-Ude, Vladivostok. Sergey Alekseyevich was giving generously to Siberia all his huge experience of scientific-organizational work.

Junior scientists V.K.Bayev, J.A.Vyskubyenko, G.P.Klyemyenkov and designer L.N.Artemov discuss the results of calculation of a steam and gas generator with S.A.KHristianovich, the director of institute

S.A.KHristianovich has found the Institute of theoretical and applied mechanics in Novosibirsk and headed it for the period since 1957 to 1965. He managed to unite the harmonious collective of associates, to awake their interest and fascinate them with originality and urgency of his ideas. The powerful technical support for the aerodynamic research necessary in designing and finalizing of the newest kinds of aircrafts has been created under his management, the turboblower station and a supersonic tunnel were constructed meeting the world-top requirements in its class as per the quality of flow and the measuring-computer system.

In special release of the magazine "The Bulletin of the Academy of sciences of the USSR" (N 6, 1964) devoted to the Novosibirsk scientific centre, S.A.KHristianovich and M.F.Zhukov wrote: "Activity of ITAM develops in the following directions: high-speed aerodynamics, shock waves, magnetohydrodynamics, rock mechanics, engine installations." The scientific scope of Khristianovich was always bound to the decision of challenging issues of the mechanics, used to be of great practical value. Sergey Alekseyevich enthusiastically worked on the project of high-output, ecologically pure steam and gas engine installation (SGI). His annual reports make evidence of it: "In 1960 I worked basically on the issues of creation steam and gas turbines, a number of reports is released." "In 1961 researches on creation steam and gas installations with the turbines working on steam and gas mixture for high-output thermal power stations proceeded. Researches of combustion chambers and steam and gas generators were carried out; feasibility designs of these chambers have been developed. Work of the installation in variable modes (variation of output, temperature of outdoor air, fuel consumption, etc.) has been investigated. In 1962 the development of the project of the installation with an output of 200 thousand kW for the state district power station in Bairam-Ali is included in the state project of the major works on new technical equipment." "In 1962 the predominant work was related with creation of engine installation with steam and gas turbines of 200 thousand kW output. In 1963 the preliminary design of the installation is to be defended. The work on creation of the installation has required solving the whole system of problems. Scientific works on creation of this installation, including theoretical and experimental researches, are in progress in ITAM and in the whole series of institutes in Moscow and in other cities. All of them are included in the state project of the major works and are coordinated by ITAM. The main result of 1962 was completion of an operational analysis of the installation and its units in all modes, as well as creation and adjustment of stands in ITAM and other organizations designed for examination of some elements of the installation." "In 1963 my personal scientific work has been connected mainly with the development of steam and gas engine installation (the analysis of variable modes, start-up, the control system, the burner device, the system of intracyclic clearing of sulphurous black oils). A monograph "Steam and gas engine installations of high output (manuscript)" has been written together with the group of associates."

Yet in late 50's - early 60's the fundamentals of the pulsing typed MHD-generators theory have been created in ITAM, and Sergey Alekseyevich demanded not mere engineer developmental work on separate schemes of the MHD-converter, but fundamental research on the basis of the advanced methods of diagnostics. The further works in this direction have led to discovery of the new phenomenon - effect of the Т-layer, which was made together with scientists of Institute of applied mathematics of AS USSR.

Under S.A.KHristianovich's initiative researches of low-temperature electro arc plasma were carried out in ITAM still in the late 50's. The system of the similitude parameters reflecting electric gas-dynamic and thermalphysic features of thermal plasma has been found. The scientific method of calculation of plasma generators has been developed on the basis of it. Further theoretical and experimental research of interaction of voltaic arc with the turbulent gas flow and the channel surface and effect of pressure and geometry of the chamber, as well as success in studying of near-electrode processes formed the basis for creation the highly efficient industrial plasma generators. It was marked in S.A.KHristianovich's and M.F.Zhukov's joint article "Low-temperature plasma generators" that "Creation of plasma generators opens up broad possibilities of their application not only in specific industries, but also for studying chemical reactions in gases at high temperatures. These reactions are still rather little investigated. But the available data give evidence that the whole series of essentially new processes can be put into practice, which can lead to the basic change of some technological processes."

	S.A.KHristianovich (in the centre) discusses the problems of analogue computer facilities application in the tasks of mechanics and energetics. YU.I.Vyshenkov; is on the right M.A.Amelina is on the left

Under the direction of Khristianovich, works aimed to take into account the energy transfer by radiation in the flows of the heated gas and works on physical and mathematical modelling of turbulent transport in tasks of aerodynamics have been started. It is written down in 1961 in his report: "the theory of ejector of continuous high pressure air dispensing lengthwise the chamber has been worked out, which allows to increase ejector efficiency more than twice at high pressure." In 1962 theoretical research was carried out in the institute under S.A.KHristianovich's management on asymptotic methods in gas dynamics with reference to tasks of nonlinear reflection of low-energy shock waves and on streamlining of bodies at hypersonic speeds, as well as the theory of turbulent burning and high-pressure ejectors. These works successfully develop now both in ITAM and in other scientific institutes of the country.

In Novosibirsk, together with his disciples Sergey Alekseyevich has continued researches on the theory of plasticity, mechanics of a deformable body and disturbance distribution in various media. In 1964 together with E.I.Shemyakin he has published an article "About dynamic compressibility of durable rocks and metals", in 1963 and 1964 he made the reports at the conference on high pressures in the Institute of chemical physics and at congress on mechanics. In the same years new results had been obtained in the theory of hydraulic break of a petroliferous seam, in researches of mechanism of sudden outburst of coal and in a series of dynamic tasks in solid media and in the theory of short waves.

No doubt Siberia has given to Khristianovich an additional opportunity for realization the new ideas and new plans. Sergey Alekseyevich has got an opportunity here to create a scientific research institute to be a director, i.e. for his scientific interests. And as a whole the Siberian branch was his creation in which he has contributed much energy, forces, and enthusiasm. And yet Khristianovich left Academgorodok. He went when were already left behind the organizational difficulties connected with the construction of a scientific centre, when Academgorodok became already cosy and comfortable for living, when essential scientific results in his supervised institute had been got. The question why it happened is difficult to give the simple answer. Departure was caused by many reasons, including the growing conflicts in relations with M.A.Lavrentyev. Paradox? Yes, it's a paradox. Ideally co-operation of two academicians might be figured a little bit differently than it has developed in a real life.

In 1965 S.A.KHristianovich returned to Moscow where he continued scientific and organizational work as the scientific supervisor in the Institute of physicotechnical and radio engineering measurements and as the member of the Board of State Committee on science and technology. From 1972 till 1988 Sergey Alekseyevich headed the laboratory of mechanics of nonlinear media in the Institute of problems of mechanics of AS USSR, and in the last years he was the counsellor at this institute administration board.

During all his life S.A.KHristianovich carried out the great work on professional training. He taught in Moscow state university, Moscow institute of physics and technology, Novosibirsk state university, in which creation he took part directly.

The merits of S.A.KHristianovich in the development of a whole series of gas mechanics sections, and that of fluid and solids have got broad public recognition both in our country and abroad. He has got the top-level awards, including the rank of the Hero of the Socialist Labour, six Lenin orders, three State premiums, N.E.Zhukovsky premium.

In social contacts Sergey Alekseyevich is simple, wise, and charming person. Many well-known scientists regard him as their teacher. In Novosibirsk S.A.KHristianovich has many friends, disciples, and followers.