The Story of NAL's Wind Tunnels
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History The Story of NAL's Wind Tunnels |
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The Visionary | The Genesis | The Campaign
NAL's Wind Tunnel Centre was set up because of the vision, commitment and untiring efforts of NAL's first Director, Dr P Nilakantan (1910-1964). Nilakantan was impulsive, volatile, brilliant and erudite; he was also a great patriot. "My life's work should be the establishment of a first rate facility or institution for my country", he used to say. Nilakantan eventually got the opportunity to fulfil this dream when he was invited by the Council of Scientific and Industrial Research (CSIR) to start the National Aeronautical Laboratory in 1959 with the "setting up of a transonic/supersonic wind tunnel at Bangalore as its first objective". It was a mandate which would have severely tested the finest engineer of the time. Starting with a clean slate, Nilakantan was being asked to deliver one of the best wind tunnels in the world! Nilakantan all but achieved this miracle in his five years at NAL. Sadly he did not live to see the fruits of his labour; following a heart attack, he died at the Coimbatore Government Hospital a day before he would have turned 54 years old. How did Nilakantan do it? Essentially by working with the passion of a man possessed. He was always the first to arrive at the Lab., and the last to leave. One of the secrets of Nilakantan's success was his well-honed engineering sense. NAL's tradition of deep involvement in design and development was established by Nilakantan; and to this day this is what makes NAL unique. As a practising engineer, Nilakantan also laid great emphasis on experiments. He was very severe on colleagues who wore terylene shirts and did not get their hands soiled. Nilakantan was also a great motivator and team builder. His erstwhile juniors (now very successful aerospace scientists and engineers themselves) say that it was an unforgettable experience to work for Nilakantan: "He could be occasionally harsh and demanding, but it was a pleasure to work for him, and earn the rare compliment from him". Nilakantan worked extremely hard on documentation; before freezing the technical specifications for the NAL wind tunnels, he prepared nearly 50 drafts, and must have personally scrutinized and reviewed many thousands of pages. Finally, Nilakantan was extremely impatient; as he perhaps had to be. When work on the wind tunnel began at Belur, one of the first tasks was to level the ground. "How long will it take?", Nilakantan asked a colleague. "About 10 months", was the reply. "I can't wait for more than a week", Nilakantan said even as he picked up the telephone to call the Army Garrison Engineer. The Army bulldozers levelled the ground in exactly three days! The Genesis Nilakantan's report received a very favourable response from CSIR and triggered off a long sequence of events during 1956-58 leading eventually to the creation of NAL in 1959 with the mandate to build, on high priority, a transonic/supersonic wind tunnel. Although it took nearly three years for NAL and its wind tunnel project to formally take off, the intervening time period was useful to carry out a large number of exploratory studies, and to freeze critical engineering specifications. Some of the major decisions taken during the period were: Opt for a 'blowdown type' wind tunnel; even though the original proposal envisaged a continuous flow closed circuit tunnel. Following this decision, preliminary design studies and pilot scale experiments were started in a big way in 1958 itself at the small blowdown tunnel of the Indian Institute of Science under Prof S Dhawan.Design the air supply and storage facility as a unitary complex which can serve a large number of blowdown wind tunnels and test rigs with a high degree of flexibility. Build a 4 ft x 4 ft trisonic wind tunnel with a Mach number range of 0.5-4.0 and a storage pressure of 150 psig. The choice of a 4 ft test section (the design teams briefly toyed with the idea of a 5 ft test section) and the Mach number range was probably dictated by the likely testing demands, energy requirements and available funding -- and the fact that almost all big tunnels at that time had the same size and range. The 150 psig pressure level was chosen because the storage system could be manufactured in India itself, and a significant foreign exchange outflow could be avoided. Looking back, one marvels at the engineering judgement and vision which marked each of these decisions. For example, one wonders if there was even a murmur of a national space programme around 1960 which might have prompted Nilakantan and his colleagues to choose a supersonic range up to Mach 4.0. But, by serendipity or otherwise, they got it absolutely right! The 4 ft tunnel went on to become an invaluable design tool for India's launch vehicle programmes. Finally, why was Belur chosen as the location? The availability of an adequate supply of water from the adjoining Bellandur Lake was one major reason. But Nilakantan also pointed out that the access to the HAL runway on one side would help future flight activity programmes, while the access to the lake on the other side offered the prospect of amphibious flight research. The foundation stone for the Belur wind tunnel complex was formally laid by Prof M S Thacker, DG-CSIR on 2 July 1961. NAL's wind tunnel campaign had begun. The project to build a 4 ft trisonic wind tunnel on an ab initio basis would be considered a mammoth and unusually complex R&D task even today. Forty years ago, it must have seemed like an impossible engineering dream The real greatness of Nilakantan lies in the fact that he converted this dream into an operational and high-performance engineering facility. The campaign involved the selection and acquisition of land; creation of workshop and laboratory facilities; civil construction to house the facilities; pilot studies to establish design criteria; setting up of associated mechanical and electrical plants; locating, selecting and developing engineering subcontractors; recruiting the best available scientists and giving them high quality training. But, more than anything else, the campaign required the highest skills in project management. What was Nilakantan's formula for success? As a manager, Nilakantan worked with great energy and devotion (he once chaired 21 meetings on one day). He was also a hard taskmaster who believed in loading his staff to 300% of their capacity. As an engineer, Nilakantan was an ardent advocate of the virtues of first principles. When approached with a design idea, he would first say make a drawing; when he was shown the drawing, he would say: now build a scaled down engineering model. Indeed, Nilakantan's core strategy for the wind tunnel project was based on this abiding faith in the laws of similitude. The project therefore began by designing and assembling a 2 inch x 2 inch intermittent blowdown wind tunnel with the associated compressor system. This tunnel, ready by 1961-62, was used extensively for several preliminary and basic investigations in wind tunnel design. Next came the 1 ft x 1 ft tunnel which too proved to be a very valuable platform for aerodynamic and structural studies, and in the development of control and instrumentation systems for larger tunnels. So when work on the larger 4 ft tunnel began, NAL the team, led by Dr D M Rao, was fully prepared to face the big challenge.The 4 ft tunnel project started gaining real momentum only in 1963. Detailed specifications, based on available literature and the first-hand international experience of NAL scientists, were drawn up. Performance characteristics (sizing of various components, run times, Reynolds number capability, control requirements to maintain steady test pressure, automatic sequencing of tunnel operations, safety interlocks, emergency shutdown etc.) were worked out to the last detail. An international enquiry was then sent for the supply, erection and commissioning of the 4 ft trisonic tunnel meeting these stipulations.
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The response from Canadian Vickers to the enquiry was finally accepted; a decision in some measure influenced by the fact that an attractive Canadian loan offer accompanied the package. Nilakantan had a few initial reservations about Canadian Vickers, but he need not have worried. The arrangement worked very well, except for a minor project delay of about a year. After three exhilarating years of engineering, the 4 ft trisonic tunnel was ready. When the roar of its first blowdown reverberated across the Belur campus and Bellundur Lake on 29 May 1967, it was a very special moment. Sadly, Nilakantan was no more; he would have been overjoyed that NAL had fulfilled its promise to the nation.
An objective assessment of the performance of the NAL wind tunnels would point to three major achievements: Very significant support to all national aerospace programmes (aircraft, missiles and launch vehicles) Development of novel test techniques for blowdown tunnels Design and fabrication of sophisticated models and balances One of the most remarkable features of NAL's 1.2m trisonic tunnel is that it has been continually busy for the last three decades! Better still, its productivity has kept increasing during these years. For example, in the early 1970's, NAL tunnels could generate 7000 to 10,000 data points every year. Twenty years later, this figure rose to 120,000 data points per year. The tunnel that Nilakantan set out to build has therefore come a long way. Early aerospace vehicle built in the country has graduated out of NAL's 1.2m trisonic tunnel. It is truly a wondrous legacy that Nilakantan has left behind for Indian aerospace. 1 June 1959: National Aeronautical Research Laboratory (NARL) set up under CSIR with temporary offices in New Delhi. Dr P Nilakantan is appointed NARL's first Director. December 1959: CSIR approaches UNSF for financial assistance for NARL's wind tunnel project. 1 March 1960: NARL moves to Bangalore with offices at Palace Road and Jayamahal Road. NARL soon becomes NAL. Dr Nilakantan invites Dr D M Rao to lead the4 ft tunnel project. 18 July - 7 August 1960: Visit of Mr L P Coombes to NAL to evaluate wind tunnel proposal; recommends funding for a 1 ft x 1 ft tunnel over a five-year period commencing 1961-62. December 1960: UNSF approves wind tunnel aid package of $1,439,700 ($1,240,000 for equipment; $100,000 for experts; $50,000 for fellowships and $49,700 for miscellaneous expenses). 1960-61: NAL acquires 243 acres of land (88 acres in Belur, 128 acres in Kodihalli and 27 acres for approach road linking the two sites). 2 July 1961: Prof M S Thacker, DG-CSIR, lays the foundation stone for the wind tunnel complex. 1962: 2" x 2" intermittent blowdown wind tunnel with associated compressed air supply system is designed and assembled. 28 March 1963: First meeting of the NAL Executive Council under the chairmanship of Mr J R D Tata. 8 April 1964: NAL/CSIR signs contract agreement with Canadian Vickers for setting up of the 4 ft trisonic tunnel at an estimated cost of Rs 22 million with foreign exchange content of Rs 18.7 million ($4.2 million). The cost to be met from a credit offered by Export Credit Insurance Corporation, Canada. 18 April 1964: Dr Nilakantan passes away. 15 May 1964: Mr K G Krishnamurthi assumes charge of NAL as Officer on Special Duty till the selection and appointment of a new Director. 11 July 1964: Mr M C Chagla, Union Minister of Education, turns the first sod for the foundation of the 4 ft tunnel. 23 November 1965: Dr S R Valluri takes over as NAL's second Director at the age of 41. 1966: The 1 ft tunnel is commissioned. 29 May 1967: First blowdown of the 4 ft trisonic tunnel; the tunnel with all auxiliary facilities such as compressor system, electrical sub-station, design office and model fabrication shop is formally set up and commissioned. 1976: Development of semi-captive trajectory simulation technique. September 1976: 10,000th blowdown of 1 ft tunnel. June 1983: 10,000th blowdown of 1.2 m tunnel 19 October 1984: Prof R Narasimha is NAL's third Director 1985: Determination of multi-booster separation trajectories of launch vehicles 1986: Development of forced-oscillation rig for dynamic derivative measurements. June 1988: Development of computer-based tunnel-control and data acquisition systems April 1989: Acquisition of diesel engine compressor system; system assures 300 cu m/minute of free air at 12.5 atmospheres 15 May 1989: NAL's 0.6 m transonic wind tunnel is commissioned. Total project cost is about Rs 20 million. 1990: Installation of fully captive trajectory system 1992: National Trisonic Aerodynamic Facilities (NTAF) completes 25 years 1 April 1993: National Aeronautical Laboratory becomes National Aerospace Laboratories 1 August 1993: Dr K N Raju, a Nilakantan protégé, assumes office as NAL's fourth Director 1993-94: Number of blowdowns in 1.2 m tunnel doubles to a record high of 1600/year. 1 May 1996: Dr T S Prahlad is NAL's fifth Director 1 July 1997: Over 23,000 blowdowns completed in 1.2 m tunnel. |
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Early days. Dr P Nilakantan (right) walking briskly with Prof M S Thacker.
