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Micro Propulsion Technologies: Powering the Next Generation of Smallsat Autonomy
Explore how innovative micro propulsion systems are enabling small satellites to revolutionize space exploration with agility, autonomy, and sustainability
The exploration of space is undergoing a dramatic transformation, thanks in large part to the rise of microsatellites and nanosatellites—collectively known as smallsats. These compact spacecraft are revolutionizing how we approach space missions by making them more agile, cost-effective, and autonomous. At the heart of this shift lies a critical enabler: the evolution of micro propulsion technologies. As miniaturized spacecraft grow in complexity and capability, so too does the need for compact, high-efficiency propulsion systems capable of meeting the unique demands of these missions. From electric ion thrusters to experimental solar sails, the latest advancements are enabling unprecedented maneuverability, autonomy, and mission flexibility. This article explores the most innovative propulsion technologies powering the next generation of small satellites and examines how they’re reshaping the future of space exploration.
Rise of Micro and Nano Satellites
From Cost Barriers to Democratized Access
The satellite industry has undergone a dramatic shift in recent years. Historically, space missions were dominated by massive, multimillion-dollar spacecraft requiring dedicated rocket launches. Today, thanks to miniaturized electronics and standardized platforms like CubeSats, even universities and startups can deploy functional satellites at a fraction of traditional costs.
Large, multifunctional satellites have long dominated space, but their prohibitive cost—often exceeding $100 million—and the requirement for powerful launch systems made them inaccessible to many. The emergence of commercial off-the-shelf (COTS) components and miniaturized electronics has changed the game. It led to the creation of smallsats, typically under 500 kg, with subsets like minisats (100–500 kg), microsats (10–100 kg), nanosats (1–10 kg), picosats (0.1–1 kg), and even femtosats (<0.1 kg). Among these, CubeSats—modular satellites built in 10x10x10 cm units—have become particularly popular for academic, commercial, and military missions.
Launch flexibility represents another significant advantage. Small satellites can hitch rides as secondary payloads, with a single Falcon 9 launch capable of deploying hundreds of microsatellites simultaneously. This shared launch approach dramatically reduces costs compared to dedicated launches. The mission diversity enabled by these small platforms is equally impressive, with applications ranging from Earth observation and IoT connectivity to interplanetary exploration.
Requirements and Challenges in Micro Propulsion
Unlike traditional satellites that relied on bulky, high-thrust systems, today’s small satellites demand compact, efficient, and scalable propulsion solutions. A spacecraft’s propulsion system is essential for adjusting its trajectory, maintaining orbit, and evading collisions. Traditional propulsion systems are too bulky for smallsats, prompting innovation in micro propulsion systems tailored to these platforms. These systems must operate within strict constraints of mass, volume, and power, yet deliver precise thrust and longevity.
Despite these advantages, small satellites face a critical limitation: orbital decay. In Low Earth Orbit (LEO), atmospheric drag can pull satellites down within months if they lack propulsion capabilities. This limitation becomes particularly problematic for missions requiring precise orbital positioning or long-duration operations. This underscores the critical need for compact and efficient propulsion systems to maintain position, extend operational life, and ensure mission success.
To enable extended missions, constellation phasing, and deep-space travel, advanced micro-propulsion systems have become essential. These systems must overcome unique challenges, including strict size, weight, and power constraints while still delivering reliable performance in the harsh space environment. The development of effective propulsion solutions for small satellites represents one of the most active areas of innovation in the space industry today.
Efforts like the ThermaSat and Aurora Resistojet Modules exemplify how propulsion technology is evolving to meet these needs. With SpaceX alone planning to deploy 42,000 Starlink satellites, efficient propulsion becomes not only a technical necessity but also an economic imperative. From constellation maintenance to end-of-life deorbiting, advanced micro propulsion systems are vital for managing growing satellite fleets.
Industry leaders like Phase Four emphasize the importance of scalable and cost-effective propulsion systems. As constellations grow and deep-space missions expand, these requirements are only becoming more demanding. From orbit raising to end-of-life disposal, the ability to maneuver and respond autonomously is essential.like water is heated and expelled to produce thrust. The AQUARIUS system from the University of Tokyo and the Steam TunaCan Thruster from Steamjet Systems are notable examples. These systems use resistive heaters to superheat water vapor, generating controlled thrust.
Key specifications and performance criteria of Propulsion system technologies
Key specifications and performance criteria play a crucial role in the selection and evaluation of propulsion system technologies for space missions. These systems can be broadly categorized into electric and non-electric systems based on their dependency on onboard power.
The chemical propulsion systems, which include solid and liquid propellant rocket engines, feature very high thrust-to-weight ratio reaching 200, with the highest exhaust velocity of about 5000 m × s−1 for the best available chemical fuels (e.g., liquid hydrogen and liquid oxygen). Electric propulsion systems demonstrate much higher exhaust velocities reaching 104 m × s−1 , but at significantly lower thrust levels and thrust-to-weight ratios not exceeding 0.01; hence, these systems are not capable of launching the vehicle from the Earth’s surface.
Electric propulsion encompasses a variety of systems such as resistojet, electrospray, ion, Hall, and pulsed plasma systems, which actively require onboard power for operation. In contrast, non-electric propulsion systems include cold gas, liquid, and solid rocket systems, which only require onboard power for regulating the propulsion process.
Specific impulse is a vital performance factor for any propulsion system, representing the impulse generated per unit weight of propellant. This metric depends on factors like thrust generated and mass flow rate of the propellant, varying based on the mission and intended applications. Other key considerations include thruster delta-V capability, size, weight, and volume constraints, operating power, integration requirements, and flight heritage. Understanding these factors helps in selecting the most suitable propulsion system for a given mission, considering launch stresses, testing processes, regulatory compliance, and obsolescence procedures.
Breakthrough Propulsion Technologies for Small Satellites
Micro propulsion systems must be lightweight, power-efficient, and capable of executing complex maneuvers. They come in many forms—cold gas thrusters, chemical systems, electric propulsion, and even innovative solutions using water or novel green propellants. These technologies must work autonomously, withstand harsh space conditions, and integrate seamlessly with the host satellite’s limited power and space budgets.
Cold gas propulsion remains a fundamental solution for small satellites, offering simplicity and reliability by ejecting compressed gases like nitrogen or xenon for precise attitude control. While its low specific impulse limits its use to short-duration missions or fine orbital adjustments, its mechanical simplicity makes it a dependable choice for basic maneuvering. In contrast, chemical propulsion—whether monopropellant or bipropellant—delivers higher thrust, making it ideal for orbital transfers or rapid repositioning.
The emergence of green propellants, such as CU Aerospace’s CMP-X (an ethanol-hydrogen peroxide blend), is revolutionizing this sector by combining environmental safety with enhanced performance. Meanwhile, solar sail propulsion presents a fuel-free alternative, harnessing photon momentum for continuous thrust. Though its acceleration is minimal, missions like Gama Alpha’s successful deployment highlight its potential for long-duration exploration and sustainable deorbiting.
For constellations in low Earth orbit, aerodynamic drag modulation offers an innovative, propulsion-free alternative—Millennium Space Systems has demonstrated how adjustable solar arrays can manipulate atmospheric drag to control satellite spacing efficiently. Together, these technologies underscore the diverse and evolving approaches to small satellite mobility, balancing efficiency, cost, and mission requirements
1. Electric Propulsion: Efficiency Over Raw Power
Electric propulsion systems, including ion, Hall-effect, electrospray, and pulsed plasma thrusters, are gaining traction for their high specific impulse and long operational life. While electric systems are energy-intensive, they offer precision and efficiency unmatched by chemical alternatives. Their future depends on advances in onboard power generation, thermal management, and miniaturization.
Electric propulsion systems, including ion thrusters and Hall-effect thrusters, represent some of the most promising solutions for small satellites. These systems use electromagnetic fields to accelerate ions, achieving extremely high efficiency compared to traditional chemical propulsion.
The key advantage of electric propulsion lies in its exceptional specific impulse, typically ranging from 2,000 to 10,000 seconds. This high efficiency makes it ideal for long-duration missions where fuel conservation is critical. While electric thrusters produce relatively low thrust, their ability to operate continuously for extended periods makes them perfect for station-keeping, orbit raising, and deep-space missions.
These systems are ideal for CubeSats requiring low but continuous thrust. For example, the Aurora Resistojet Module (ARM-A) provides 3-axis control using water vapor, offering a safe and effective method for in-orbit adjustments
Innovations in RF Ion and Plasma Thrusters for Small Satellites
Radio-Frequency Ion Thrusters (RITs) represent a significant advancement in electric propulsion for small satellites. These systems use RF electromagnetic fields to ionize propellant and generate thrust efficiently, benefiting from decades of plasma research and miniaturized RF components developed for telecommunications. As a type of gridded ion thruster, RITs ionize propellant in a discharge chamber before accelerating the plasma through electrostatic grids. While offering exceptional efficiency (60-80%) and specific impulse (2,000-10,000+ seconds), traditional ion thrusters have faced challenges with cathode degradation – a limitation that new designs are overcoming.
Phase Four’s Maxwell thruster exemplifies these innovations as the first turnkey RF plasma propulsion system for small satellites. Its electrode-free design eliminates traditional wear components while maintaining high performance, offering plug-and-play integration that simplifies constellation deployment. Similarly, T4i’s REGULUS system employs helicon wave technology to create a compact, throttleable thruster without electrodes or neutralizers. Both solutions demonstrate how modern RF thrusters are overcoming historical barriers to provide reliable, cost-effective propulsion for small spacecraft.
The plasma thruster market has seen parallel innovation with Orbion Space Technology’s Aurora system, the first miniaturized Hall-effect thruster designed specifically for small satellites. While Hall thrusters have existed since the 1960s, Orbion’s achievement lies in scaling the technology down while implementing automated, high-volume production techniques. This addresses a critical gap in the smallsat supply chain where propulsion systems have remained a specialized, low-volume commodity.
These advancements collectively mark a turning point for small satellite capabilities. By combining the high efficiency of electric propulsion with simplified, scalable designs, new systems like Maxwell, REGULUS and Aurora are enabling missions that previously required larger spacecraft. From precise constellation maintenance to deep-space exploration, these thrusters are removing the traditional trade-offs between performance, cost and reliability that have constrained small satellite missions. As production scales and flight heritage accumulates, RF and plasma thrusters are poised to become the propulsion standard for next-generation small satellite constellations and exploration missions alike
2. Electrospray and Nanotech Thrusters
Electrospray thrusters, such as ESA’s ATHENA system, utilize nano-engineered emitters to eject ionized liquid propellant. This technology offers ultra-precise thrust control in an exceptionally compact package.
The scalability of electrospray systems makes them particularly attractive for nanosatellites. ATHENA’s design, which fits multiple thruster systems in a 10 square centimeter area on a CubeSat, demonstrates how this technology can provide propulsion without significantly impacting the satellite’s mass budget. Another significant advantage is the use of non-toxic ionic liquid propellants, which simplify handling and storage compared to traditional hazardous fuels.
Recent testing has validated the technology’s potential, with ATHENA completing over 400 hours of continuous operation. The system’s successful prototype launch aboard the Firefly Alpha 2 mission marks an important step toward operational deployment, currently planned for 2024.
3. Green Chemical Propulsion: Safer Alternatives to Hydrazine
The space industry is actively developing safer alternatives to traditional hydrazine-based propulsion systems. These “green” propellants offer comparable performance while eliminating many of the handling hazards and regulatory challenges associated with hydrazine.
AF-M315E has emerged as one of the most promising high-performance green monopropellants. It offers improved safety characteristics while delivering specific impulse values comparable to hydrazine. Dawn Aerospace has taken a different approach with its nitrous oxide/propene system, which avoids International Traffic in Arms Regulations (ITAR) restrictions while maintaining competitive performance metrics.
These developments reflect a broader industry trend toward more sustainable and user-friendly propulsion solutions. As regulatory pressures increase and launch providers impose stricter safety requirements, green propulsion systems are becoming increasingly attractive for small satellite operators.
4. Solar Sails and Laser Propulsion
Solar sail technology represents one of the most innovative approaches to spacecraft propulsion. By harnessing photon pressure from sunlight, these systems provide completely fuel-free propulsion—an ideal solution for long-duration, deep-space missions.
The Gama Alpha mission, supported by CNES and private entities, recently demonstrated solar sail deployment and control in orbit. This technology offers infinite specific impulse in theory, though practical limitations include very low thrust levels and the need for large, lightweight sail structures.
Meanwhile, a constellation of small satellites developed by Millennium Space Systems, a Boeing subsidiary, demonstrated the capability to maneuver in space without propulsion systems. Utilizing aerodynamic drag generated by adjusting solar arrays, these satellites could control their positions relative to one another. Despite lacking traditional propulsion, the satellites effectively manipulated their spacing for tasks like data transfer through ground-based automation systems. This innovative approach highlights the potential of leveraging atmospheric drag for orbital control, offering a cost-effective alternative for small satellite missions.
Laser propulsion represents an even more futuristic concept, where ground-based lasers would provide momentum to spacecraft without requiring onboard propellant. While still in experimental stages, this technology could eventually enable entirely new mission architectures for small satellites.
5. Water and Steam-Based Systems
Researchers are exploring various water-based propulsion systems that offer safety and cost advantages. Samara University has developed an electrothermal thruster using a water-alcohol mixture as propellant, providing a simple, low-cost solution for small satellite maneuvering.
Howe Industries has proposed an innovative “steampunk” concept that leverages phase-change materials to create thrust. These water-based systems are particularly interesting for potential in-situ resource utilization on lunar or Mars missions, where water ice may be available as a local propellant source.
Resistojet Propulsion:
Among the most promising solutions is resistojet propulsion, where a propellant rust for orbital maneuvers.
Resistojets operate on the principle of superheating a propellant—such as ammonia or methanol—by passing it through a heated chamber before expelling it through a nozzle to generate thrust. This process is especially advantageous for CubeSats and other small satellites, offering a balanced trade-off between simplicity, efficiency, and controllability. Heating the propellant enhances the specific impulse (Isp), proportional to the square root of the exhaust temperature, which makes resistojets highly attractive for low-thrust, high-precision applications like attitude control and small orbit adjustments. Recent tests have shown exit temperatures as high as 1175°C for ammonia, validating the thermal endurance and performance scalability of these systems.
These systems, while not suited for high-velocity orbit transfers, shine in fine-tuning maneuvers, formation flying, and controlled de-orbiting procedures. Their relative simplicity and reliability make them ideal for CubeSats operating in constellation formations or in scientific missions that require extended station-keeping over months or years.
Military and Civilian Applications
Civilian Use Cases
Small satellite propulsion systems enable numerous civilian applications. Earth observation missions benefit from agile repositioning capabilities that allow satellites to respond quickly to natural disasters or other time-sensitive events. The growing mega-constellations like Starlink rely on propulsion for station-keeping and collision avoidance, ensuring reliable global internet coverage.
Perhaps most exciting are the deep-space exploration missions now possible with propelled CubeSats. NASA’s Lunar Flashlight and Mars Cube One (MarCO) missions have demonstrated that small satellites can contribute meaningfully to planetary science. These missions open new possibilities for distributed science observations and technology demonstrations beyond Earth orbit.
Military and Defense Applications
Military applications of small satellite propulsion are equally transformative. The ability to rapidly reposition satellites enables responsive reconnaissance capabilities that can adapt to changing operational needs. Distributed constellations with autonomous maneuvering capabilities offer enhanced resilience against anti-satellite threats, ensuring continuity of critical space-based services.
Perhaps most revolutionary is the concept of autonomous satellite swarms—groups of small satellites that can coordinate their movements using artificial intelligence. These systems could enable sophisticated tactical operations while presenting adversaries with a challenging, constantly evolving target set.
Charting the Future of Micro Propulsion
The field of micro propulsion is evolving rapidly, with innovations ranging from highly efficient electric propulsion systems like Hall-effect thrusters and ion engines, to novel concepts such as solar sails and field-emission electric propulsion. The development of plug-and-play solutions like Phase Four’s Maxwell and T4i’s REGULUS opens new avenues for integrating high-performance propulsion into even the smallest of space platforms.
At the frontier of propulsion innovation, electrospray and pulse plasma thrusters are showcasing how miniaturized systems can provide not only agility but also sustainability and safety—using low-toxicity, easily handled propellants like ionic liquids or even water. Meanwhile, groundbreaking concepts such as ATHENA and the Miniature Tether Electrodynamics Experiment (MiTEE) are exploring radical ideas to make propulsion self-sustaining, using Earth’s magnetic field or nanotechnology-based emitter arrays.
Empowering a New Era of Autonomous Space Missions
The implications of these propulsion advancements extend far beyond the lab or testing grounds. They enable real-world deployment of small satellite constellations for climate monitoring, Earth imaging, secure communications, disaster relief, and planetary science. In the defense sector, micro propulsion enhances satellite survivability, operational secrecy, and responsiveness in a contested space environment.
The fusion of micro propulsion with intelligent autonomous control systems promises fully self-operating swarms of nanosatellites—capable of dynamic task allocation, agile formation changes, and intelligent fault recovery. This synergy marks the beginning of a new chapter in space mission design: one that emphasizes distributed intelligence, resilience, and adaptability.
Conclusion: Fueling Tomorrow’s Space Dreams
Micro propulsion technologies are not just enablers—they are revolutionizers. By offering precision thrust and autonomy within minimal size, weight, and power constraints, they equip microsatellites and nanosatellites to venture farther, react faster, and adapt smarter than ever before. Whether enabling deep-space exploration, optimizing communication networks, or advancing Earth observation, micro propulsion is unlocking the full potential of small satellites
In the coming decade, these tiny spacecraft will become the backbone of space-based infrastructure—from global broadband constellations to interplanetary exploration missions. As we venture deeper into space and increase the complexity of satellite constellations, propulsion will determine which missions succeed and which fail. The continued development and deployment of advanced propulsion systems will be critical to unlocking their full potential.
With every CubeSat launched and every thruster fired in orbit, we edge closer to democratizing access to space. The era of compact, capable, and intelligent space exploration is here—and propulsion is the engine driving that future
References and Resources include
https://aip.scitation.org/doi/full/10.1063/1.5007734
