The earliest rockets

WAN HU'S ROCKET CHAIR

One often-told story of early Chinese rocketry is the legend of Wan Hu, a Ming-Dynasty official who supposedly flew into space using a chair supported on 47 rockets.

HERO'S ENGINE

An early reaction motor was designed in the first century ad by Greek-Egyptian scientist Hero of Alexandria. Heat applied from below boiled water in a spherical vessel, and steam spouting from the nozzles caused the sphere to spin on its axis.

Before spaceflight, there was the rocket - at first little more than a novelty, but later a powerful weapon of war whose importance waxed and waned over the centuries, nevertheless playing a pivotal role in several military conflicts around the world.

Though it took some time for scientists to realize it, a rocket is a "reaction motor" operated by the simple principle of action and reaction - as fuel exhaust escapes from the rocket in one direction, the rocket is pushed in the other. The basic requirement for any rocket, then, is a propellant that can be stored in a relatively stable state, but which expands violently when required. And until the 20th century, only one thing fitted the bill: a black powder, also known as gunpowder - made up of charcoal, sulphur, and saltpetre (potassium nitrate) - that exploded when a flame was applied.

History does not record the invention of this early weapon of mass destruction, but it is thought to have originated in Song Dynasty China around the middle of the 11th century. The use of exploding powder as a propellant would have followed naturally, probably a result of seeing containers flung across the room by the force of its explosions. By

CONGREVE ROCKETS

The rockets designed by William Congreve (top) featured a number of important innovations, including stabilizing fins around their bases. Later Congreve designs were fired from copper launching tubes, which helped to direct their flight and reduced the risk of misfires during launch.

1232, self-propelled "flying bombs" were being used to defend the Chinese city of Kai'feng from the advancing Mongol army of Genghis Khan. These early rockets would have been almost as dangerous for the defenders as the attackers, since whenever any part of their flimsy paper or card wrapping burnt through to form another exhaust, they might shoot off in another direction, setting fires wherever they landed.

The new weapons, however, were not enough to save China from conquest, and by 1241 the Mongols were expanding their empire to the west, using rockets themselves in battles across Eastern Europe. And with them came the secret of black powder - the recipe was first written down around 1250 by English scholar Roger Bacon (though he disguised it in code, wary of its potential as a weapon). While the Mongol threat disintegrated in a series of internal disputes, the knowledge of black powder spread rapidly. In 1288, Arab forces were using rockets in an attack on the Spanish city of Valencia, and by 1405 rockets were a familiar part of the medieval war machine, depicted by German engineer Konrad Kyeser in his military manual Bellifortis.

While China now entered a more peaceful era under the Ming Dynasty, the evolution of rockets in Europe continued apace. Kyeser's rockets were already mounted on the top of long stabilizing rods, which could be placed in a gutter-like launcher to allow for basic targeting. Seventeenth-century Polish author Casimirus Siemienowicz illustrated a variety of rockets that are sometimes strikingly similar to the designs of today, with long tubular bodies, stabilizing fins, and even multiple stages (see p.23). In 1715, Russian Tsar Peter the Great's plans for a new capital at St. Petersburg included an enormous factory for

CONGREVE ROCKETS

The rockets designed by William Congreve (top) featured a number of important innovations, including stabilizing fins around their bases. Later Congreve designs were fired from copper launching tubes, which helped to direct their flight and reduced the risk of misfires during launch.

ADVANCEO ROCKETRY

This illustration shows armourers constructing a rocket to the plans of Casimirus Siemienowicz. In his time, the study of ballistics, allowing flight paths and targets to be calculated, was advancing rapidly.

TECHNOLOGY

LAWS OF MOTION AND GRAVITY

heavier cladding directed the rocket's exhaust more efficiently and would not burn through, the new rockets had a vastly increased range of more than 800m (Vi mile), despite their greater weight. By the late 18th century, as the British grip on India tightened, Ali's son Tippu Sultan put his father's invention to good use in the sieges of Seringapatam (1792 and 1798), though rockets were not enough to save him from eventual defeat. In fact, they ultimately helped his enemy, since captured rockets shipped back to Britain probably inspired William Congreve, working at the Royal Arsenal, to develop a more advanced model. Congreve gave his rockets a payload, or cargo, for the first time, mounting a separate charge of black powder in the rocket's nose, where it would explode on impact - the first warhead. He also invented an improved launching platform and came to realize that a ring of five smaller exhaust nozzles gave a rocket much more stability than a single outlet.

The 19th century saw a series of modifications to Congreve's design. In 1807, Henry Trengrouse devised a rocket that could carry a line to a ship in difficulties, which soon became an important part of

Until the late 17th century, philosophers were resigned to the idea that the Universe was driven by supernatural, or at best inscrutable, forces, with little relationship between the behaviour of objects on Earth and those above. This view began to change around 1609, when Johannes Kepler finally swept aside old notions of heavenly spheres and celestial clockwork, replacing them with laws of planetary motion that could accurately describe (though not explain) the orbits of the planets. However, it was the English scientist Isaac Newton (left) who finally showed how the movement of the planets, l and of objects on Earth, could all be explained through ;three simple laws of motion, and the effects of a force he called gravity that was produced by any object with a substantial mass.

coastguard equipment in Britain and beyond. Shortly after this came the invention of the rocket-powered harpoon and the signal flare. The most important advance, though, came in 1844 when Englishman William Hale tilted the exhaust nozzles of his designs, causing the rockets to rotate around their long axes and fly with greater stability. This meant that the clumsy stabilizing stick could at last be eliminated.

the mass production of rockets. But in truth, the rocket was on the verge of obsolescence, thanks to the increased range and accuracy of artillery.

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