Imagine a world without rockets. No satellites beaming down GPS signals, no astronauts exploring the cosmos, no spellbinding images of distant galaxies. But for most of human history, the idea of escaping Earth’s gravity was just a distant dream.
From gunpowder to rocket fuel
Image from “Gunpowder: Origins in the East” from Brown University
That dream began to take shape in ancient China, with a discovery that would change the course of history: explosive powders that would eventually lead to gunpowder. The exact timeline is debated, with some sources dating the discovery as early as 220 BC, while others place it in the first millennium AD. What’s clear is that by the 9th century AD, Chinese alchemists had developed black powder, a precursor to modern gunpowder, by mixing potassium nitrate, charcoal, and sulfur. This explosive mixture, initially used for fireworks and later for military applications, would become the foundation for the first solid-fuel rockets.
By 1264, a simple type of rocket-like device known as “ground rat” or “earth rat” (ti lao shu) was described in a text from 1264. This device was essentially a tube, likely made of gunpowder-filled bamboo. When lit, it would shoot around on the ground in various directions during firework displays
The forerunner of modern missiles and rockets
Early gunpowder rockets would eventually spread throughout China and eventually to other parts of the world. By the 13th century, such rockets were being used in warfare by the Mongols and later adopted by European armies.
Over the centuries, gradual improvements were made to rocket design and propellants. In the late 19th and early 20th centuries, several notable figures contributed to the theoretical and practical foundations of modern rocketry:
- Konstantin Tsiolkovsky in Russia developed the mathematical theory of rocket propulsion in 1903
- Robert Goddard in the United States conducted practical experiments and made a string of innovations in rocket design from the 1920s through the 1940s.
- Hermann Oberth in Germany published influential works on spaceflight theory in 1923 (Die Rakete zu den Planetenräumen” (The Rocket into Interplanetary Space).
Robert Goddard standing beside his liquid-fueled rocket. [Image: NASA]
In line with liquid rocket advances, solid propellant technology continued to progress. A notable period of development in solid rocket propulsion took place in the 1930s and 1940s at the California Institute of Technology (Caltech). According to a Springer publication on the history of solid rocket propulsion, researchers at Caltech made significant improvements to solid propellants during this time, enhancing their power and reliability.
Among the innovators of this period was Jack Parsons, the American rocket engineer, chemist and occultist who invented the first rocket engine to use a castable, composite rocket propellant. Parsons would go on to found the Jet Propulsion Laboratory (JPL) and the Aerojet Engineering Corporation.
In 1942, Parsons came up with the novel idea of using liquid asphalt as a binding agent with potassium perchlorate as an oxidizer for solid rocket fuel. This fuel, known as GALCIT-53, was more stable and powerful than previous formulation, GALCIT-27, which used ammonium nitrate as the oxidizer
According to George Pendle, a biographer of Jack Parsons, Parsons was part of a new generation of self-taught rocket scientists who were pushing the boundaries of rocketry in the early 20th century. Pendle, in his book “Strange Angel: The Otherworldly Life of Rocket Scientist John Whiteside Parsons,” describes how Parsons and his colleagues were operating at the fringes of established science, driven by a combination of technical knowledge and visionary zeal. The saga would eventually provide fodder for the television version of Strange Angel.
Los Angeles Times photo of Jack Parsons holding a car bomb replica. The public domain image was featured on the cover of “John Carter’s Sex and Rockets: The Occult World of Jack Parsons.”The success of GALCIT-53 led to its adoption by the U.S. military for various applications, including jet-assisted takeoff (JATO) units for aircraft and propulsion systems for missiles. This development paved the way for more advances in solid rocket propellant technology.
Solid rockets offer several advantages, including simplicity, reliability, and the ability to provide strong, consistent thrust. These characteristics make them well suited for applications requiring significant initial acceleration, such as launch vehicles. Yet they come with a notable limitation: once ignited, solid rocket motors cannot be throttled or shut down until all the fuel is expended. This “all-or-nothing” nature requires careful planning and design considerations for missions using solid propellants.
Why the Space Shuttle used a hybrid approach
Perhaps the most iconic example of a hybrid rocket propulsion system is the Space Shuttle, which featured two towering white boosters strapped to the side of the orbiter — Solid Rocket Boosters (SRBs). These sizable solid rocket motors provided the initial brute force needed to break free of Earth’s grip. Each SRB stood 149 feet tall and 12 feet in diameter, weighing 1.3 million pounds at launch. These boosters generated 3.3 million pounds of thrust each, yielding more than 70% of the Shuttle’s total liftoff power. For approximately two minutes, they burned through their propellant mixture of ammonium perchlorate, aluminum, and other compounds. Eventually, the Shuttle would jettison the boosters, reducing the vehicle’s mass and improving efficiency for the remainder of the ascent.
The Shuttle also relied on its three liquid-fueled main engines for additional power and precise control. These engines, drawing propellant from the orange external tank, provided the remaining thrust and continued to fire long after the SRBs had done their job. Using liquid hydrogen as fuel and liquid oxygen as the oxidizer, these engines offered several advantages, including longer burn times, the ability to throttle for more precise maneuvering, and the option to shut down if necessary, enhancing safety. This combination of solid and liquid propulsion systems allowed the Space Shuttle to achieve its mission profile, which demanded a powerful liftoff and versatile orbital operations.
From its first launch in the early 1980s to the final landing in 2011, NASA’s space shuttle flew 135 missions. [Image: NASA]
SpaceX and the Falcon 9
SpaceX Falcon 9 rocket launches Crew Dragon spacecraft on NASA’s Demo-2 mission to the International Space Station, carrying astronauts Robert Behnken and Douglas Hurley. Launch from Kennedy Space Center, Florida, May 30, 2020, marking the return of American astronauts launching from American soil since 2011. [NASA/Joel Kowsky]
One of the most significant advances in rocketry post-Space Shuttle era is the development of reusable rockets. Here, private companies such as SpaceX have led the charge. The company’s Falcon 9 rocket, first launched in 2010, featured a reusable design. In December 2015, SpaceX made history by landing a Falcon 9’s first stage after it delivered satellites to orbit, proving that reusing rockets could save money. The Falcon 9 stands at 229.6 feet tall and has a mass of 1.2 million pounds, capable of carrying payloads up to 50,300 pounds to low-Earth orbit. Its first stage is powered by nine Merlin engines, generating 1.7 million pounds of thrust at sea level. The reusability of the Falcon 9 allows SpaceX to reuse the most expensive parts of the rocket. As of August 2020, refurbishment and reuse of a booster cost less than 10% of the price of a new booster, with SpaceX breaking even on the second flight and saving money from the third flight onward.
Since then, SpaceX has repeatedly landed and re-flown Falcon 9. While it initially proved reliable, the system experienced an anomaly on July 11, 2024 during a Starlink satellite launch, leading to the loss of its payload. This was the first in-flight failure for the rocket since June 2015, following a streak of more than 300 successful orbital liftoffs.
Blue Origin and New Shepard
Jeff Bezos’ company, Blue Origin, is another big name in reusable rockets. They made headlines in November 2015 when their New Shepard rocket, designed for short trips to the edge of space, successfully landed upright after its flight. This proved that even rockets built for tourism and brief research flights could be designed for multiple uses.
But Blue Origin isn’t stopping there. Its New Glenn rocket, a much larger vehicle built for reaching orbit, is also designed with reusability in mind. Like the Falcon 9, the first stage of New Glenn will aim to land back on Earth after launch, making those trips to orbit more affordable and lessening the environmental impact of space travel.
A new era of global space collaboration
Outside of SpaceX and Blue Origin, there is ample evidence that the end of the Space Shuttle program didn’t mean the end of space exploration – in fact, it paved the way for a new era of global collaboration and ambition in space.
China has emerged as a major force in space exploration, developing advanced technology and undertaking ambitious missions. The China National Space Administration (CNSA) has made significant progress with its Chang’e lunar exploration program, successfully landing rovers on the Moon’s surface and returning lunar samples to Earth. Significant achievements include the Chang’e-4 mission, which landed on the far side of the moon in 2019, and the Chang’e-5 mission in 2020, which brought back 1.731 kg of lunar samples. China has also expanded its space activities to include a modular space station, Mars exploration with the Tianwen-1 mission and Zhurong rover, and the development of the BeiDou satellite navigation system.
But China isn’t limiting its ambitions to the Moon. In 2021, the CNSA achieved a milestone with the Tianwen-1 mission, successfully landing a rover on Mars on its first try – a feat previously only the U.S. had achieve. These achievements are possible in part thanks to China’s development of the Long March rocket family, with the Long March 5 serving as a workhorse for launching these complex missions.
India making its mark in space
The Indian Space Research Organisation (ISRO) has cemented itself as a significant player in space exploration, known for its ingenuity and cost-effective approach. In a remarkable display of technical prowess, ISRO’s Mars Orbiter Mission (Mangalyaan) successfully reached Mars in 2014 on its very first try.
PSLV-C35 [Wikipedia]
ISRO continues to push the boundaries of space exploration, launching a variety of satellites for communication, Earth observation, and scientific discovery. Two rockets have been central to India’s success, including the Polar Satellite Launch Vehicle (PSLV), ISRO’s workhorse (pictured). The PSLV specializes in placing satellites into polar and sun-synchronous orbits — suitable for observing Earth from pole to pole or keeping a spacecraft consistently illuminated by the sun.
The Geosynchronous Satellite Launch Vehicle (GSLV) is ISRO’s heavy lifter, designed to carry heavier payloads into geosynchronous transfer orbits. This is useful for placing communication satellites, which need to stay above a fixed point on Earth. Over the years, ISRO has significantly improved the GSLV, making it capable of launching even larger satellites — a testament to their commitment to continuous advancement.
European Space Agency (ESA)
The European Space Agency (ESA) also has a significant focus on space exploration. ESA’s Ariane rocket family, known for its reliability and power, continues to be a cornerstone of space travel, launching a an array of satellites and spacecraft. In 2021, the Ariane 5 rocket played a role in sending the James Webb Space Telescope into space.
ESA actively collaborates with other spacefaring nations, including NASA, on missions like the ExoMars program, which seeks to search for signs of past or present life on Mars. ESA also is involved in conducting research in the International Space Station.
The future of spacecraft
The future of space exploration isn’t some distant fantasy. The next chapter of rocketry is already being developed. Engineers are working on developing a new generation of heavy-lift rockets, like Europe’s Ariane 6 and Blue Origin’s New Glenn, capable of lofting heavier payloads and humans toward the Moon, Mars, and beyond. Additionally, SpaceX’s Starship, a fully reusable spacecraft, could further reshape the economics of space travel.
Outside of the likes of SpaceX, private companies are playing a larger role, with spacecraft like Boeing’s Starliner and Sierra Nevada’s Dream Chaser offering novelways to transport astronauts and cargo to the International Space Station. NASA’s Artemis program aims to establish a sustained presence on the Moon, and missions like Europa Clipper and Hera will enable research on of Jupiter’s icy moon and the aftermath of asteroid deflection tests.
Further ahead, the Red Planet beckons. While challenges remain in terms of long-duration life support, radiation shielding, and the sheer distance involved, the dream of setting foot on Mars could be within reach relatively soon. NASA’s long-term vision for Mars exploration, combined with SpaceX’s Starship plans and the ongoing development of advanced propulsion technologies, could pave the way to sci-fi-esque explorations of the Red Planet.
To that end, NASA’s Mars Exploration Program is aiming to send lower-cost, high-science-value missions to Mars at a higher frequency. This plan includes: A series of missions launched at every two-year launch window, each costing up to $300 million. Ongoing robotic exploration, including the Perseverance rover, which is caching rock samples for a future sample return mission. The Mars Sample Return mission, a joint effort with ESA to bring the first samples of Mars material back to Earth for detailed study
From the first spark of black powder to the roar of a Falcon 9 launch, humanity’s fascination with rockets has ignited a fire that will continue to fuel our exploration of the cosmos. As rockets continue to evolve, our journey to the stars is just beginning.
