An Introduction to Rockets

Estimated Reading Time: 7 minutes

TL;DR

For today’s issue, we do a deep dive into the history and technology of rockets. Rockets were first designed in the 10th century and found an increasing role in the battlefield over the coming centuries. Rocketry really hit its stride in the 20th century, notably taking humans to the moon in Apollo 11. The science of rocketry continues to advance today with rocket technology taking on a considerable commercial component.

A Very Brief History

The first rockets may have been invented before the year 1000 by the Song dynasty and started to find their way into military campaigns by the 13th century. The illustration below, drawn from a 14th century Ming dynasty military manual is the oldest known depiction of a rocket.

The oldest known depiction of rockets is from the Huolongjing, a Ming dynasty military manual from the 14th century.

Rocket technology spread throughout Eurasia, possibly as a result of Mongol adoption of rocket technology. These early rockets had limited range, which reduced their effectiveness on the battlefield. The next major breakthrough in rocketry happened in India with the invention of the iron casing rocket in Mysore, which led to rockets that could fly over 2 km. These rockets were used to powerful effect against the British in the Anglo-Mysore wars.

A Mysorean using his rocket as a flagstaff. Note that the rocket is upside down. Mysorean rockets were the first military rockets to use iron tubes to hold propellant and were later copied by British forces. The long stick attached to the rocket was used to reduce the tendency of the rocket to veer off course (source).

After the fall of Mysore, British forces seized unexploded Mysorean rockets and used them to design Congreve rockets which were widely used in the Napoleonic wars and against American forces in the War of 1812, famously inspiring a line in the Star Spangled Banner (“And the Rockets’ red glare, the Bombs bursting in air”).

Congreve rockets were designed by British forces based on the Mysorean design and were widely deployed across multiple fronts and in multiple wars (source).

As modern physics began to flourish in the 19th and 20th centuries, rocketry achieved new heights as mathematical models of rocket operation grew more sophisticated. The German V-2 Rocket was the first long range missile and also the first manmade object to reach space.

A replica of a V2 rocket (source).

Rocketry technology continued to grow at a rapid clip after the end of World War II. The most terrifying advance of the cold war age was the development of intercontinental ballistic missiles, which could deliver nuclear payloads anywhere in the world. The rapid growth of nuclear arsenals still threatens global safety today. The other major achievement was of course the moon landing, first achieved by the Apollo 11 rocket pictured below.

The Apollo 11 rocket landed the first astronauts on the moon in 1969 (source).

Governmental support of rocketry waned (at least in the US) after the Apollo missions, but recently commercial spacecraft design has started to flourish with the invention of powerful reusable rockets.

Modern Rocket Design

Modern rocket engines can be broadly divided into the class of liquid and solid fueled. A liquid propellant uses combustion of liquid fuels to drive a rocket. Similarly, solid fuel rocket engines use solid propellants to drive a rocket. Solid fuel technology is most commonly used for missiles due to the greater storability of solid fuel rockets

A simplified diagram of a solid-fuel rocket. 1) A solid fuel-oxidizer mixture (propellant) is packed into the rocket, with a cylindrical hole in the middle. 2) An igniter combusts the surface of the propellant. 3) The cylindrical hole in the propellant acts as a combustion chamber.4) The hot exhaust is choked at the throat, which, among other things, dictates the amount of thrust produced. 5) Exhaust exits the rocket (caption and image from source).

Another important component in the rocket is the shape of its output nozzle. The geometry of the nozzle controls the amount of thrust produced by the rocket as the diagram below shows.

The shape of the rocket nozzle also determines the thrust on the rocket. A nozzle that tapers outward can gain more thrust for the rocket from the combustion reaction (source).

Modern rockets are also often staged, with different components of the rocket split off at different stages of the launch process to reduce weight as the diagram below shows.

Rockets often split off portions of themselves to reduce weight. Some stages may contain fuel while others contain storage and passenger compartments (source).

Nuclear Thermal Rockets

All rockets that have been launched thus far have been propelled by chemical reactions, but there has been considerable early stage research into nuclear fuels for rockets. The NERVA research program which ran from the late 50s until 1973 investigated the feasibility of using a nuclear reactor to propel a rocket. Tests were conducted of a nuclear thermal rocket on the ground, but such an engine has never been used on a rocket in production.

A nuclear thermal rocket engine from the NERVA program for a solid propellant design. Although ground tests have been performed, no nuclear thermal rocket has been launched into space, although nuclear thermal rockets may find renewed use in the coming decades (source).

Discussion

Rocket science has been the source of both terrifying weapons and awe-inspiring spacecraft. In today’s issue, we learned about some of the history and science that underpins modern rocketry. In future issues, we will explore some of the more recent commercial advances in rocket science that have spurred the start of a new space age.

Highlights for the Week

• https://www.usip.org/publications/2020/07/rising-china-has-pacific-islands-its-sights: The People’s Republic of China (PRC) is shifting its attention towards Pacific island states.

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Deep Into the Forest is a newsletter by Deep Forest Sciences, Inc. We’re a deep tech R&D company specializing in the use of AI for deep tech development. We do technical consulting and joint development partnerships with deep tech firms. Get in touch with us at partnerships@deepforestsci.com! We’re always welcome to new ideas!

Credits

Author: Bharath Ramsundar, Ph.D.
Editor: Sandya Subramanian