Rocket Science: From the Mongols to the Moon and beyond

Rocket science is a famously difficult area, but it’s more than the physics of force and trajectories. Martin Pitt takes a chemical engineering view of its history

THE YEAR of the Dragon will be ushered in in February with all manner of firework displays. Fittingly, given their origins, rockets will feature heavily in the Chinese New Year celebrations.

Early history

Solid rockets using gunpowder called “fire arrows” were first used in 1232 by the Chinese against the Mongols in the battle of Kai-fung-fu. Soon after, the Mongols launched rockets back at the Chinese. Within a hundred years, the first attempt at powered flight was made by an official called Wan-Hu (dates unknown), sitting in a chair with 47 rockets behind and a large kite attached above. Assistants lit the rocket fuses and ran clear. There was a loud roar and a huge cloud of smoke. When it cleared, Wan-Hu and his apparatus had disappeared (too high a reaction rate is a hazard for an exothermic batch reactor!).

A better idea turned out to be a large rocket-shaped reactor transferring energy to a much smaller mass of stone or metal which went at high speed to the enemy. The rocket body, now known as a gun, was reusable while smaller, cheaper objects were the missiles.

Fire arrows became fireworks for entertainment, and in 1561 Johann Schmidlap (dates unknown) published a manual for making them, showing a diagram of a three-stage rocket to enable fireworks to go higher (pictured).

In 1633, the Ottoman engineer Lagâri Hasan Çelebi (dates unknown) was launched in a seven-winged rocket loaded with 140 lb of gunpowder from Istanbul across the Bosporus. He used some form of parachute to slow his descent into the water. Rewarded by the Sultan, he was later killed in battle fighting Cossacks in Crimea.

Rockets were again used by the Indian kingdom of Mysore, defending itself from the British East India Company in 1780 (depicted in the painting below). With an iron cylinder and carefully calculated trajectory they were so effective that the Royal Arsenal commissioned studies and soldier/inventor William Congreve (1772–1828) patented his version in 1808. They were successfully used against Napoleon, and the US when it attacked Canada in 1812. The US national anthem (1814 poem by Francis Key Scott) refers to the flag in “the Rockets’ red glare”. Congreve also organised the coronation firework display for King George IV (1762–1830) in 1821.

The patronised pioneer

While several people wrote on the theory of rockets and hypothetical spaceflight, it was American physicist and childhood tinkerer Robert Hutchings Goddard (1882–1945) who combined his advances in theory with practical engineering and published two landmark patents in 1914 – one on a solid-fuel multistage rocket and one on a liquid-fuelled rocket using gasoline and liquid nitrous oxide. Experimentally (and self-funded), he found that powder rockets were only 2% efficient in producing thrust. By using a separate combustion chamber and a convergent-divergent (de Laval) nozzle to accelerate the hot gases to supersonic speed, he increased this to 63% in a fixed test. These are now used in nearly all rocket motors and made escape velocity possible. His 1919 paper, A Method of Reaching Extreme Altitudes was ridiculed as “absurd” by The New York Times which claimed Isaac Newton’s Third Law of Motion – that every action produces an equal and opposition reaction – would be rendered obsolete in space due to “the need to have something better than a vacuum against which to react”. Failing to understand that it is the backward thrust of the exhaust and not air that acts on the rocket, pushing it forward, The New York Times published a tongue-in-cheek correction in 1969, the day after the Apollo Moon landing.

Goddard launched the first liquid-fuelled rocket on 16 March 1926, using gasoline and liquid oxygen. By 1941, he and his team had successfully launched 35 rockets and solved major problems in control of the engine and in control of the rocket in the atmosphere including gyroscopes and movable fins and nozzles. When the US entered World War Two, he was directed to work on more important problems that had nothing to do with rocketry. His death in 1945 prevented his continuation of the work, which had received little recognition in his country. His wife published 214 patents from his notes after his death.

Goddard launched the first liquid-fuelled rocket on 16 March 1926, using gasoline and liquid oxygen. By 1941 he and his team had successfully launched 35 rockets

The rocket and the man that changed the world

Though Goddard has been called “the man who ushered in the Space Age”, it was controversial German aerospace engineer Wernher von Braun (1912–1977) who gave us the Moon landings.

Goddard’s work had interested German scientists who corresponded with him until 1939. Von Braun was working on his PhD thesis Construction, Theoretical, and Experimental Solution to the Problem of the Liquid Propellant Rocket (in which two rockets were built and successfully launched) when the Nazis came to power in 1933. His work impressed the army which funded the development of a series of rockets based on Goddard’s work, getting von Braun closer to his lifelong dream of spaceflight. A fine horseman, he was a member of an SS riding group in Berlin and joined the Nazi Party in 1937 while technical director of the army rocket centre at Peenemünde. He later joined the SS, rising to the rank of major.

In 1944, with Germany on the brink of defeat in World War Two, Adolf Hitler ordered the mass production of prototype A-4 which went on to became the V-2, the world’s first long-range guided ballistic missile.

The V-2 was an amazing technological advance. During takeoff and while in the atmosphere the trajectory was maintained by moving rudders on the tail fins and graphite vanes in the combustion outlet, under the guidance of an analog computer served by gyroscopes and an accelerometer. Later, radio was used. On 24 June 1944 a V-2 reached 175 km, making it the first rocket to reach space.

The interior was pure chemical engineering.

First, the exothermic decomposition of hydrogen peroxide was initiated with sodium permanganate, producing a superheated mixture of steam and oxygen. This drove a 500 kW turbine, in turn driving fuel and oxidant pumps. Goddard had found pumps a real problem, so used gas pressure. Von Braun worked from 1935 to 1942 with a company making large firefighting pumps to develop what is now known as a turbopump. They are a key part of rocketry today but are also used in ramjets and where there is a source of steam or hot gas.

The fuel was ethanol mixed with 25% water to reduce the flame temperature and thermal stress, and add mass to the thrust. The oxidant was liquid oxygen. Both were in aluminium-magnesium alloy tanks, the oxygen being insulated with glass fibre. It took 30 tonnes of potatoes to make the alcohol for one launch.

The fuel was injected with special nozzles as a mist for efficient combustion, after passing through the shell of the thrust chamber to cool it. Some of the alcohol was run through tiny holes in the interior wall, creating a film between it and the hot gases. These cooling mechanisms prevented the steel from melting and were key features of the Space Shuttle and the Apollo rockets. In addition, some of the oxygen passed through ribs on the outside.

More than 3,000 V-2s were launched, but due to the Germans’ use of slave labour for the rocket programme, more people died in the manufacture of the V-2 than were killed by its deployment.

Von Braun surrendered, along with his team, to US troops in the Alps on 2 May 1945. The previous day his younger brother Magnus, who spoke the best English of the group, had ridden away on his bicycle to make contact with the American troops at Reutte and make the arrangements.¹

Cold War

The US military’s interest in V-2 technology smoothed von Braun’s integration into American life, with the army providing him and his associates with jobs at Fort Bliss, Texas. Here, he and his team participated in Project Hermes, a research programme focusing on the missile needs of army field forces.

The US got the V-2 team leaders, but the Soviet Union got the manufacturing facility in Nordhausen (which became part of East Germany in 1949) and many German technicians. Aeronautical engineer Sergei Pavlovich Korolev (1907–1966), who had launched the first Soviet liquid fuel rocket in 1933, was given the task of replicating the V-2 technology, and ultimately beating the Americans. Meanwhile some of the people working on the Manhattan Project were passing on atomic secrets to the USSR, so they would have something to put on the top.

The US plan to be the only ones with the superweapon having been foiled, the two countries now competed to be the one with the greatest capacity to annihilate, diverting much of the national income to this end, rather than the benefit of their people, in a time of threatening conflict known as the Cold War.

Von Braun used his new-found freedom of speech to argue that at least a little of the resources could be used for peaceful purposes such as Earth surveying and high-altitude science, since rockets were now capable of orbital velocities. Korolev had come to the same conclusion and proposed a plan in 1954. The Soviets realised the propaganda rather than scientific value, and on 4 October 1957 launched the first artificial satellite, Sputnik 1, which I saw in the sky (actually the reflection from a piece of the rocket which followed it into orbit), and amateurs could hear via its radio bleeps. The word Sputnik word means “fellow traveller” like the Latin word satelles, from which we get satellite. Less than a month later, Sputnik 2 was launched carrying the first creature to orbit Earth, a stray dog named Laika (meaning barker). The US Explorer 1 launched on 31 January 1958 (on a rocket designed by von Braun) and the Space Race had begun.

Space race

On 12 April 1961, Yuri Gagarin (1934–1968) became the first man to go into space, completing an orbit of the Earth (the first woman was Valentina Tereshkova (b 1937) in 1963). The US was second again, so on 25 May 1961 John F Kennedy (1917–1963), the US president, upped the stakes by announcing a plan to put a man on the Moon by 1970 and get him back safely. This would require vastly bigger rockets, new techniques and eye-watering amounts of US dollars. Both aims were achieved in July 1969, and viewed by millions live on TV, including me. Von Braun’s contribution was its Saturn V “super-heavy launch lift vehicle”, a 3,000 tonne three-stage rocket, fuelled by kerosene for the first stage, hydrogen for the others, and liquid oxygen for all.

The last human on the Moon was Gene Cernan (1934–2017) in 1972. In my lifetime, science fiction became old history, though there are plans for a crewed lunar landing in 2026 as part of the NASA-led Artemis program.

If von Braun gave us Moon landings from a weapon of war, Korolev may be said to have given us satellites (of which there are now more than 3,000 still active), which developed as a spin-off from the Space Race.

The UK developed two rockets which never had launch failures, Black Knight and Black Prince, and put its own satellite, Prospero One, into orbit in 1971. The same year, the UK government suspended rocket development. However, there are signs the UK is ready to rejoin the Space Race with Skyrora and Orbex Prime among British companies with plans to launch satellite-carrying rockets from Scottish soil.

And while rockets have become more varied and sophisticated, they still depend on the fundamentals developed by Goddard and the experience of von Braun, and involve chemical engineering from materials production to fluid mechanics, heat transfer and combustion kinetics.

Reference

1. https://www.thechemicalengineer.com/features/cewctw-magnus-von-braun-rocket-man/

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Martin Pitt CEng FIChemE is a regular contributor. Read other articles in his history series: https://www.thechemicalengineer.com/tags/chemicalengineering-history