As the new Space Age kicks off in force, propulsion technologies are becoming a booming industry. Read more about the different types of propulsion in development.

For more than half a century, spaceflight has relied on a familiar formula: powerful chemical rockets generating enough thrust to escape Earth’s gravity and propel spacecraft towards their destinations. From the Apollo Moon missions to today’s commercial launch vehicles, chemical propulsion has remained the backbone of space exploration.

Yet a quiet revolution is underway.

As the global space sector expands beyond government-led exploration into satellite mega-constellations, commercial lunar missions, space logistics, and ambitions for human journeys to Mars, traditional propulsion systems are increasingly being pushed to their limits. New mission profiles demand greater efficiency, longer operational lifetimes, enhanced manoeuvrability, and lower costs.

In response, engineers and researchers are developing a new generation of propulsion technologies that promise to transform how spacecraft travel through space. From electric thrusters and green propellants to nuclear engines and solar sails, these innovations are reshaping the future of spaceflight and redefining what is possible beyond Earth orbit.

Why propulsion matters

Every space mission is fundamentally constrained by propulsion.

A spacecraft’s engine determines how quickly it can travel, how much payload it can carry, how long it can operate, and where it can ultimately go. Propulsion also represents one of the largest contributors to spacecraft mass, with fuel often accounting for a significant proportion of a mission’s total weight.

The challenge lies in a fundamental trade-off. High-thrust engines can accelerate spacecraft rapidly but consume large amounts of propellant. More efficient systems use less fuel but typically generate far lower thrust.

For decades, mission planners have had to balance these competing requirements. However, emerging propulsion technologies are beginning to shift those constraints and open new possibilities for exploration and commercial operations.

The enduring dominance of chemical rockets

Chemical propulsion remains the only practical method for launching payloads from Earth.

Launch vehicles such as those developed by companies including SpaceX, Blue Origin and Rocket Lab rely on chemical reactions to generate enormous amounts of thrust within seconds. This capability is essential for overcoming Earth’s gravitational pull and atmospheric resistance.

Modern rocket engines have become significantly more advanced than their predecessors. Reusability, improved manufacturing techniques, and sophisticated engine designs have dramatically reduced launch costs.

However, chemical propulsion faces inherent physical limitations. Even the most advanced rocket engines convert only a fraction of their propellant mass into useful momentum. As a result, long-duration missions require substantial fuel reserves, increasing spacecraft mass and mission complexity.

For this reason, engineers are increasingly turning to alternative propulsion technologies once spacecraft reach orbit.

Electric propulsion comes of age

Among the most significant developments in modern spaceflight is the rapid adoption of electric propulsion.

Unlike chemical rockets, electric propulsion systems use electricity to accelerate charged particles, generating thrust far more efficiently. Although the resulting thrust is relatively small, these engines can operate continuously for months or even years.

Ion thrusters and Hall-effect thrusters are now becoming standard equipment on many commercial satellites. Rather than carrying large quantities of chemical fuel, spacecraft can use electric propulsion to gradually adjust their orbits, maintain positioning, and extend operational lifetimes.

The benefits are substantial.

Electric propulsion systems require significantly less propellant, reducing spacecraft mass and freeing up capacity for additional payloads. Satellite operators can launch larger payloads, extend mission durations, and lower overall operating costs.

This technology has already proven itself in deep-space exploration. NASA’s Dawn mission used ion propulsion to travel between the asteroid Vesta and the dwarf planet Ceres, demonstrating capabilities that would have been difficult to achieve using conventional propulsion alone.

Today, electric propulsion is rapidly becoming the preferred choice for commercial satellite operators and is expected to play an increasingly important role in future exploration missions.

Green propellants gain momentum

For decades, spacecraft have relied heavily on hydrazine, a highly toxic chemical propellant used for manoeuvring and attitude control.

While effective, hydrazine presents significant operational challenges. It is hazardous to handle, requires extensive safety procedures, and increases mission costs due to specialised storage and fuelling requirements.

The search for safer alternatives has accelerated in recent years.

A new generation of so-called “green propellants” aims to deliver comparable or improved performance while reducing environmental and operational risks. These propellants are generally less toxic, easier to transport, and safer for ground crews.

Beyond safety improvements, some green propellants also offer higher performance, allowing spacecraft to achieve greater manoeuvrability with less fuel.

As governments and commercial operators place increasing emphasis on sustainability and operational efficiency, green propulsion technologies are expected to become more widely adopted throughout the coming decade.

Nuclear propulsion and the journey to Mars

Few propulsion technologies generate as much interest as nuclear propulsion.

Human missions to Mars remain one of the most ambitious goals in space exploration. However, conventional chemical rockets would require journeys lasting many months, exposing astronauts to prolonged radiation exposure and the physiological effects of microgravity.

Nuclear propulsion could significantly reduce travel times.

Two primary concepts are currently under development: nuclear thermal propulsion and nuclear electric propulsion.

Nuclear thermal propulsion uses a reactor to heat propellant to extremely high temperatures before expelling it through a nozzle. This approach offers substantially greater efficiency than traditional chemical rockets while maintaining relatively high thrust.

Nuclear electric propulsion uses a reactor to generate electricity that powers electric thrusters. While producing lower thrust, it offers exceptional efficiency for long-duration missions.

Government agencies and industry partners are actively investing in both approaches. Although significant technical and regulatory challenges remain, many experts view nuclear propulsion as a key enabling technology for future crewed missions beyond the Moon.

Solar sails: travelling on sunlight

One of the most intriguing propulsion concepts requires no fuel at all.

Solar sails harness the momentum of photons emitted by the Sun. Although individual photons carry very little momentum, a large reflective sail can gradually accumulate acceleration over time.

The concept has existed for decades, but advances in lightweight materials and deployment systems are bringing solar sail technology closer to practical applications.

Unlike conventional propulsion systems, solar sails can continue accelerating indefinitely without consuming propellant. This characteristic makes them particularly attractive for long-duration scientific missions and deep-space exploration.

Recent demonstration missions have shown that solar sailing is not merely a theoretical concept. While the technology is unlikely to replace conventional propulsion for most missions, it could become an important tool for specialised applications where efficiency outweighs speed.

The rise of space tugs and orbital logistics

The rapid growth of the commercial space economy is creating demand for entirely new types of propulsion-enabled services.

Space tugs, sometimes referred to as orbital transfer vehicles, are designed to move satellites between different orbits after launch. Rather than requiring each satellite to carry large quantities of fuel, operators can deploy spacecraft using dedicated transfer vehicles.

This emerging market could reshape how satellites are launched and operated.

Space tugs may eventually support a wide range of services, including:

• Orbital repositioning
• Satellite servicing
• Refuelling operations
• Debris removal
• End-of-life disposal

These capabilities depend heavily on advances in propulsion technology. Efficient, reliable engines will be critical to enabling the in-space transportation networks that many analysts believe will underpin the next phase of commercial space development.

Air-breathing engines for very low earth orbit

Another emerging area of research focuses on a challenge much closer to Earth.

Satellites operating in very low Earth orbit experience atmospheric drag that gradually pulls them back towards the planet. Maintaining these orbits typically requires regular propulsion manoeuvres and fuel consumption.

Researchers are exploring air-breathing electric propulsion systems capable of collecting atmospheric particles and using them as propellant.

If successfully commercialised, these systems could allow satellites to operate at lower altitudes for extended periods without carrying significant fuel reserves.

Such capabilities would offer advantages for Earth observation, communications, and scientific research missions, potentially opening entirely new orbital operating regimes.

Propulsion and the commercial space economy

The importance of propulsion extends far beyond exploration.

As the space economy continues to grow, propulsion technology is becoming a major competitive differentiator. Satellite operators seek longer mission lifetimes. Launch providers want lower costs. Governments require greater strategic flexibility. Exploration agencies need systems capable of reaching more distant destinations.

Each of these objectives depends on advances in propulsion.

Investors have recognised this opportunity. Propulsion-focused startups are attracting increasing levels of funding as governments and commercial operators seek technologies capable of improving performance while reducing operational costs.

In many respects, the future winners of the space economy may not simply be those building rockets or satellites, but those developing the engines that enable them.

A multi-engine future

Despite rapid innovation, no single propulsion technology is likely to dominate every aspect of spaceflight.

Chemical rockets will remain essential for launch operations. Electric propulsion will continue expanding across satellite markets. Green propellants will improve sustainability and operational efficiency. Nuclear propulsion may enable human exploration of Mars and beyond. Solar sails and other emerging technologies will support specialised missions that would otherwise be impossible.

Rather than replacing one another, these technologies are likely to coexist, each serving different mission requirements.

This increasingly diverse propulsion ecosystem reflects the growing complexity of space operations. As humanity ventures further into the Solar System and commercial activity expands in Earth orbit, mission planners will have access to a wider range of propulsion options than ever before.

The engine of the next Space Age

Spaceflight has always been defined by propulsion. Every breakthrough in exploration, commerce, and scientific discovery has ultimately depended on advances in how spacecraft move through space.

Today, the industry is entering a new era. The combination of electric propulsion, green fuels, nuclear technologies, solar sailing, and emerging orbital mobility solutions is transforming the economics and capabilities of space missions.

The result is a propulsion revolution that extends far beyond engineering innovation. These technologies will influence where humanity can travel, how long spacecraft can operate, and what kinds of missions become possible.

The next chapter of space exploration will not be written by a single engine design. It will be powered by an expanding portfolio of propulsion technologies, each helping to push the boundaries of what can be achieved beyond Earth.