An Encyclopedia of the History of Technology part 67 pps

PART THREE: TRANSPORT 642 617) in his paper of 1809. Versions of this toy powered by clock springs were made by the Swiss Jakob Degen in 1816, and by several later inventors. In 1842 an English engineer, W.H.Phillips, flew a model which was driven by jets of steam (generated by the heat from a form of chemical firework) from the rotor-tips, and in 1863 the Vicomte Ponton d’Amecourt built a model helicopter powered by a conventional reciprocating steam engine which was probably too heavy to fly. The Italian engineer Enrico Forlanini succeeded in flying a similar model for 20 seconds in 1877 by the expedient of pre-heating the boiler before attaching it to the model. The first serious attempts to build a full-size piloted helicopter were made in France in 1907, by Louis Breguet and Paul Cornu, who were both aiming for a 50,000-franc prize offered for the first one-kilometre flight. Breguet’s machine had four biplane rotors, driven by a 18kW (24hp) Antoinette engine. In September 1907 it hovered for a minute, but was stablized by four assistants holding the machine’s four corners. Cornu’s machine also had an Antoinette engine, driving two sets of two-bladed rotors; when tested in November it successfully hovered just above the ground for several minutes. Two months later the prize was won by Farman’s flight on a fixed-wing Voisin (see p. 624), and Breguet and Cornu both abandoned their efforts; Breguet turned his attention to fixed-wing machines. For the next thirty years, a considerable number of inventors attempted to make a practical helicopter, with no significant success. As an alternative to the power-driven rotor, the Spaniard Juan de la Cierva produced an aircraft which he called the autogiro. This was a machine on which lift was produced from a rotor which was rotated after the manner of a windmill as the aircraft was pulled through the air by a conventional engine and propeller. In 1923, Cierva built a machine with hinged rotors, free to flap up and down as they rotated, which provided a simple solution to the unbalanced lifting force generated when the rotor was in forward flight. (On one side of the rotor disc, the blade is moving forward relative to the aircraft; on the other side it moves backwards. Adding the forward motion of the aircraft, one blade is moving much faster than the opposite one, and therefore generates more lift unless the incidence is reduced on the advancing blade.) Cierva was subsequently funded by the British Air Ministry to produce a number of designs which were built in some numbers in Britain, France, Germany and the USA, and the Cierva C.30 model was used for civil and military purposes on a fairly small scale from 1935. Later models of autogiro have been made, mainly as single-seat sports machines, but this type of aircraft has never found a realistic practical use. One of those who took a licence to build Cierva machines was the German Focke-Wulf company, whose founder, Heinrich Focke, produced the first practical helicopter in 1936, using the hinged rotor system. To counter the torque effect of a power-driven rotor, Focke employed two counter-rotating AERONAUTICS 643 rotors on outriggers from a basically conventional fuselage. The engine in the nose drove a conventional propeller for forward flight, and also drove the two rotors through bevel gears and inclined shafts. The practicality of Focke’s Fw61 helicopter was demonstrated by a 110km (68 mile) cross-country flight in 1938, and by public demonstrations inside the Berlin Sporthalle. Focke produced a larger development of the Fw61 in 1940, and another German engineer, Anton Flettner, produced a practical helicopter which was built in small numbers for the German Navy, but wartime priorities lay elsewhere and neither design found significant practical application. Parallel work in other countries produced working prototypes by 1940; by far the most significant was Igor Sikorsky’s VS-300 in the USA, which passed through a variety of configurations to its final successful form in December 1941. A single three-bladed rotor with hinged blades was used to generate lift and, by tilting the rotor disc, forward propulsion, and a small rotor with horizontal axis facing sideways served to counter the torque and acted as a rudder. Sikorsky’s configuration has continued to dominate helicopter design to the present day. Although a variety of counter-rotating twin-rotor designs have also been brought into large-scale production, probably 80–90 per cent of all the helicopters built have employed a single rotor and an anti-torque tail rotor (see Figure 12.13). Helicopters were normally powered by conventional aircraft piston engines (with modified lubrication systems and additional cooling fans) until the 1950s, Figure 12.13: A Sikorsky S-61N helicopter carrying two dozen passengers: the classic helicopter configuration with one main rotor and a small tail rotor to balance the torque. PART THREE: TRANSPORT 644 but then gas turbines were introduced, first by the French company Aérospatiale in 1955. These engines were designed to have a turbine stage driving the rotor through a gearbox—colloquially known as a turboshaft engine. The main advantage was the lower vibration level and greater reliability of the gas turbine and, as in other aircraft applications, the gas turbine has supplanted the piston engine for all but the lowest-powered helicopters. The helicopter rotor of the 1940s and 1950s was a complicated piece of machinery: the blades were hinged to allow a limited degree of motion at their roots about all three axes, and a variety of springs and friction dampers were employed to allow the blade angles to be varied appropriately. Subsequent development has replaced mechanical hinges and bearings by elastomeric hinges, employing plastic materials with tailored properties of strength and flexibility. Aérospatiale introduced their Starflex rotor hub, in which the three conventional hinges are replaced by a single ball joint of rubber and steel sandwich construction, into their AS350 Ecureil in 1977. At the same time, glass fibre and carbon-fibre composites have been introduced for construction of the rotor blades. The ability to land and take-off vertically enables the helicopter to perform a wide variety of duties, but its mechanical complexity compared to a fixed- wing aircraft leads to higher costs, so the major users have always been the military. Apart from being used as troop transports and for casualty evacuation, they are used widely for observation work and for ground attack against infantry and armour. Civilian uses include passenger carrying into confined spaces (oil-rig platforms, city-centre roof-top terminals, hospitals, and the like), pipe-line patrols, and specialized crane-type operations. Typically, the Boeing-Vertol 234 carries up to 44 passengers for up to 800km at 250kph (500 miles at 155mph), and the largest production helicopter in the world is the Russian Mil Mi 26 with 20,000kg (44,000lb) payload. CONVERTIBLE AND HYBRID AIRCRAFT The helicopter rotor is speed-limited in the same way as the aircraft propeller by the onset of shock waves as the speed increases, and in practice it is difficult to design an efficient helicopter for a speed of more than about 280kph (175mph), which clearly limits its productivity. There has therefore always been a potential requirement for an aircraft using helicopter rotors for vertical takeoff, which is capable of conversion in flight to a configuration where the lift is provided by fixed wings. A variety of solutions has been advanced, ranging from conventional helicopters with auxiliary wings and propulsion engines, such as the 40-passenger Fairey Rotodyne of 1957, which set a world helicopter speed record of 307kph (190.7mph) in 1959, to a variety of designs with tilting engines, with or without tilting wings. Typical of the tilt-wing designs was the Canadian CL-84 of 1965: this demonstrated a speed range from hover to over AERONAUTICS 645 500kph (310mph). Although many different experimental ‘hybrid’ aircraft have been built and flown, no design has reached full production status. RECREATIONAL AIRCRAFT AND GLIDERS While the greater part of the world’s aircraft production has been devoted to vehicles with a military or commercial utility, there has always been a significant interest in purely recreational aircraft. For the most part, these have been technically similar to the more functional machines, but from time to time there have been interesting technical novelties in this field. Unpowered gliders were used by pioneers like the Wrights as a stepping-stone towards powered flight, but they have also been used as sports aircraft since the 1920s. The origins of the movement lie in the restrictions placed on Germany by the Treaty of Versailles, which effectively forbade any development of powered aircraft in that country. Flying enthusiasts therefore turned to the construction of aircraft without power, which were initially launched from the tops of hills. It was soon discovered that it was possible to maintain height in the up-currents along the windward face of the hill, and then that there were often thermals, rising air currents caused by solar heating of the ground, which could be exploited by skilled pilots in suitable machines. This provided the incentive to produce aircraft with high lift/drag ratios, which developed into a distinctive family of aircraft with very smooth streamlined shapes, wings of long span, and light weight. From the 1930s onwards, such aircraft were produced mainly of wood, and then from the 1950s of glass-fibre and other plastics. In the 1980s a typical high-performance glider (the German-built Schempp-Hirth Nimbus 3) using both carbon-fibre and glass-fibre in its construction, had a wing of 23m (75ft) span, empty weight of 392kg (864lb) and achieved an optimum glide ratio of 55:1: that is, in still air it travels 55m horizontally for a height loss of 1m. Gliders used for sporting competitions are single-seaters, and two-seaters are used for training. During the period 1940–50 large transport gliders were developed (mainly in Germany, Great Britain and the USA) for troop-carrying purposes, more clearly related to conventional transport aeroplanes than to sports gliders. The largest types were the Messerschmitt Me 321 with steel tubular construction covered in wood and fabric, carrying up to 20 tonnes, and the all-wooden British Hamilcar designed to carry a light tank or similar load up to 8 tonnes. Such gliders were rendered obsolete by the post-war development of transport helicopters. There have been repeated attempts to produce very simple and very cheap aeroplanes for recreational flying since the earliest period, Santos-Dumont’s Demoiselle of 1909 perhaps qualifying as the first such. For the most part, these aircraft have been simply scaled-down versions of conventional aeroplanes, with limited weight and engine power, but occasionally some technical novelty has appeared in this field. PART THREE: TRANSPORT 646 One such was Henri Mignet’s Pou-de-Ciel (‘Flying Flea’) of 1933. Mignet was a self-taught aircraft designer with unorthodox ideas, who had already built several single-seat light aircraft. His Pou was a wooden tandem monoplane with no control in roll, stabilized by having considerable dihedral angle on both wings, and steered by a large rudder. The rear wing was, in effect, a fixed stabilizing tailplane and control in pitch was effected by altering the angle of incidence of the front wing. In spite of its unusual control system, the Pou-deCiel was a reasonably successful flying machine; but it suffered a number of fatal crashes which led to official bans in France and Britain. Later the prohibitions were relaxed and the aircraft re-designed to make it safe, but the wave of popular enthusiasm for the model had been killed. A more significant novelty appeared in 1948 when the American engineer Francis Melvin Rogallo obtained a patent for his flexible-winged glider. In its simplest form, this comprised a triangular wing, with solid booms along the centre line and the leading edges. A single sheet of fabric (of nylon, Terylene or similar artificial fibre) stretched between the booms was free to billow into two half-cones under aerodynamic pressure in flight, very much like the sail of a yacht. Rogallo’s initial invention was tested by the US services in 1963 as a potential lightweight transport vehicle with a 155kW (ziohp) engine, but found its real application as a sports vehicle. Initially used as a hang-glider and controlled by the pilot shifting his weight beneath it, it first became popular in 1969 as an adjunct to water-skiing. Further development of the basic idea in various countries added increased wing-span, double-surfaced wings, and a large variety of different control systems including conventional ailerons, wing warping, dragflaps; and power units which ranged from 4.5kW (6hp) chain- saw motors to specially-developed engines of around 37kW (50hp). MAN-POWERED FLIGHT Since the earliest times, mankind has dreamed of flying by human power alone. These ambitions were discouraged by Giovanni Borelli whose posthumous work DC motu animalium of 1680 showed how inadequate man’s muscular powers were compared to those of birds, but by no means all would- be flyers were deterred. Eventually, with increasing aerodynamic knowledge the prospects for ornithopters were seen to be poor, and attention turned to conventional aeroplane shapes with pedal-driven propellers. In 1935 two German engineers, Helmut Haessler and Franz Villinger, built a light-weight machine with a single propeller, belt-driven from bicycle pedals operated by the pilot; this machine was flown for about two years, and straightline flights of up to 700m (2300ft) were obtained. The Haessler-Villinger aircraft had an empty weight of 34kg (75lb) and a span of 13.5m (44.3ft); the Italian Bossi- Bonomi Pedialante of 1936 weighed about 100kg (220lb) and had a span of 17.7m AERONAUTICS 647 (58ft), with a pair of propellers driven by shafts from the pilot’s pedals. Broadly similar performance was claimed, with flights up to one kilometre. A revival of interest in the 1960s was largely due to prizes offered by Henry Kremer and administered by the Royal Aeronautical Society. Initial attempts by various groups produced performances little better than the pre-war German and Italian designs, but eventually the first Kremer prize, for a flight round a prescribed course of about 2km (1 mile), was won by the American Bryan Allen in 1977, flying an unorthodox aircraft of tail-first configuration designed by Paul McCready. In a very similar machine, Gossamer Albatross, the same pilot won a second Kremer prize on 12 June 1979 with a flight across the English Channel— 35.8km (22.25 miles) in 2 hours 49 minutes. To produce this performance, the average power generated by the pilot was 0.34hp (250 watts). Gossamer Albatross had a wing span of 28.5m (94ft) and empty weight of only 32kg (70lb), made possible largely by the use of modern materials including carbon- fibre tubes for the main structure and Mylar film for the covering. FURTHER READING Bilstein, R.E. Flight in America 1900–1983 (Johns Hopkins University Press, Baltimore, 1984) Cavallo, T. The history and practice of aerostation (1785) Chant, C. Aviation: an illustrated history (Orbis, London, 1978) Cierva, J. de la Wings of to-morrow; the story of the autogiro (New York, 1931) Clement, P L. Montgolfières (1982) Gablehouse, C. Helicopters and autogiros: a chronicle of rotating-wing aircraft (Muller, London, 1968) Gibbs-Smith, C.H. Sir George Cayley’s aeronautics, 1796–1855 (HMSO, London, 1962) —— Aviation: an historical survey from its origins to the end of World War II (HMSO, London, 1986) Gregory, H.F. The helicopter (London, 1948) Jablonski, E. Seawings, an illustrated history of flying boats (Hale, London, 1974) Jane, F.T. All the world’s aircraft ed. by C.G.Grey and later by others (Jane’s, London, 1916–20 , 1922 to date) Kármán, T. von Aerodynamics: selected topics in the light of their historical development (Cornell University Press, New York, 1954) Nayler, J.L. and Ower, E. Aviation: its technical development (P.Owen, London, 1965) Reay, D.A. The history of man-powered flight (Pergamon Press, Oxford, 1977) Robinson, D.H. Giants in the sky: a history of the rigid airship (G.T.Foulis, London, 1973) Rolt, L.T.C. The aeronauts: a history of ballooning, 1783–1903 (Longman, London, 1966) Tissandier, G. Histoire des ballons (1887) Valentine, E.S. and Tomlinson, F.L. Travels in space: a history of aerial navigation (1902) Whittle, Sir F. Jet (London, 1953) Wise, J. A system of aeronautics (1850) Wright, W. and O. The papers of Wilbur and Orville Wright ed. by M.W.McFarland, 2 vols. (New York, 1953) 648 13 SPACEFLIGHT JOHN GRIFFITHS BLACK POWDER ROCKETS The origin of the rocket is shrouded in mystery, but it was probably developed in the East. The Sung dynasty Chinese (AD 960–1279) had the technology to make rockets, but there is no definite evidence that they did so. By 1300 black powder and rockets were known in Europe and Arabia, and it seems likely that their secrets reached Europe along trade routes from the Orient. The earliest European recipe for black powder was given by the Franciscan friar Roger Bacon around the year 1265. He evidently considered it dangerous knowledge; the recipe was in code. The first European picture of a rocket is in Konrad Kyeser’s Bellifortis of c.1400, and seems to have been copied from an Arabic manuscript. Although occasionally used as a weapon it was as a peaceful firework that the rocket became best known to Europeans, but in sixteenth-century India it was not uncommon for armies to carry thousands of rockets into battle. Some two hundred years later British and French troops striving to dominate India experienced the Indian rocket weapons at first hand. Some captured in 1799 wyere taken to Woolwich Arsenal, near London, and they may be seen in the Rotunda Museum at Woolwich. The Indian rockets may have inspired the British inventor Sir William Congreve, who turned the black powder rocket into a modern ‘weapons system’ during the Napoleonic Wars. Congreve realized that rockets could have the firepower of heavy artillery but, unlike guns, were easy to move around. He developed a wide range of rockets and launchers, together with the tactics to use them in warfare. First used against Napoleon’s invasion fleet at Boulogne in 1806, Congreve’s rockets were later copied by many European armies. However, his rockets had one major failing as a weapon: they were not very accurate. Also, like earlier rockets, they had cumbersome stabilizing stocks. Other inventors such as William Hale developed stickless rockets, but the problem of accuracy SPACEFLIGHT 649 was never solved. By the 1870s improved artillery had made the rocket a weapon fit only for colonial wars, and by the First World War it was virtually obsolete. If the rocket had failed as a war weapon, it had found civilian uses. Successful life- saving rockets were developed in the 1850s to carry lines to ships, and Congreve rockets were also used for harpooning whales. SPACEFLIGHT PIONEERS Meanwhile, nineteenth-century authors such as Jules Verne and H.G.Wells were writing what came to be known as science fiction stories. For centuries there had been tales about travel to other planets. Victorian authors added technology and ‘invented’ the spaceship, relying on whirlpools, rising dew or flying birds to carry their heroes into space. Early science fiction directly inspired three visionaries to consider the practical problems of spaceflight. Independently, they all realized that the rocket was the key to spaceflight, and that a new, more powerful type of rocket burning liquid fuels would be needed. Their work eventually led to the conquest of space by such rockets. Konstantin Tsiolkovsky, a Russian schoolteacher, made the earliest theoretical studies of spaceflight in, although his work did not become well known until the 1920s. Robert H.Goddard, an American physicist, launched the first successful liquid-fuel rocket on 16 March 1926 (see Figure 13.1). Although he was secretive about his work, it is clear that his rockets were the first to use many features now vital to modern space technology. Hermann Oberth, a Romanian schoolteacher, published Die Rakete zu den Planetenraumen (The rocket into planetary space), which overnight became a popular success. Unlike Tsiolkovsky and Goddard, Oberth was a publicist of spaceflight, and during the 1920s his work led to growing interest in the possibility and the founding of space-travel societies in different countries. VENGEANCE WEAPON TWO The growing interest in rocketry attracted the attention of the German army to the possibility of a secret weapon which had the added advantage of not being banned by the Treaty of Versailles. In about 1930 a Captain Dornberger was ordered to develop ‘a liquid fuel rocket…the range of which should surpass that of any existing gun’. At that time virtually nothing was known about liquid fuel rockets. Goddard’s work was a well-kept secret; the only other experts were amateur experimenters, such as members of the German Verein für Raumschiffahrt (Society for Spacetravel). Dornberger gradually built up a team of rocket engineers. One of his first recruits was an enthusiastic and knowledgeable member of the VfR, Werner von Braun. PART THREE: TRANSPORT 650 After Hitler’s rise to power in 1933, the formation of the Luftwaffe in 1935 gave added impetus to Dornberger’s work. The liquid fuel rocket was seen as a power unit for aircraft, and in 1936 the army and the Luftwaffe began work on a large rocket research establishment at Peenemunde on the Baltic coast. In the same year, Dornberger and von Braun’s team began design work on ‘Aggregate 4’, their fourth rocket design. A-4 was to carry a 1 tonne warhead to a target over 250km (155 miles) away. Its size was determined by the largest size of load that could be easily transported by road or through any railway tunnel, and A-4 was to be 14m (46ft) long and 3.5m (11.5ft) across its fins. Figure 13.1: Robert Goddard standing next to his liquid fuel rocket a few days prior to its successful launch on 16 March 1926. SPACEFLIGHT 651 It took six years’ work to get such an advanced rocket off the drawing board, and even then it was by no means ready as a weapon. After the first successful launch on 3 October 1942, it was nearly three years before it became better known as ‘Vengeance Weapon 2’, successor of the V-1 ‘flying bomb’ (see Figure 13.2 and p. 1005). The V-2 offensive lasted from September 1944 to March 1945; about 1100 missiles landed in England, and 1750 hit targets on the Continent. Its value as a weapon has been hotly discussed; over some seven months, V-2 missiles delivered about as much explosive as the Allied air forces dropped on Germany during a single day. After the war, Dornberger wrote, ‘The use of the V-2 may be aptly summed up in the two words “Too Late”’. As well as the V-2, Germany developed a wide range of smaller guided missiles, few of which entered sevice, and the ME 163 rocket-powered fighter. POST-WAR RESEARCH German rocket technology was one of the great prizes of the Second World War and the USA profited from it most of all. Von Braun’s team of rocket scientists chose to surrender to the Americans, who also gained the priceless Peenemunde technical archives and much V-2 hardware. The Soviet forces Figure 13.2: The launch of a captured German V-2 rocket during the British Operation Backfire programme in 1946. . countries. VENGEANCE WEAPON TWO The growing interest in rocketry attracted the attention of the German army to the possibility of a secret weapon which had the added advantage of not being banned by the. launched from the tops of hills. It was soon discovered that it was possible to maintain height in the up-currents along the windward face of the hill, and then that there were often thermals, rising. turboshaft engine. The main advantage was the lower vibration level and greater reliability of the gas turbine and, as in other aircraft applications, the gas turbine has supplanted the piston engine