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Introduction
The exploration of the Moon, Mars, and beyond has always captured the human imagination, but it has also presented daunting challenges, particularly when it comes to propulsion. Traditionally, massive rockets producing millions of pounds of thrust were the go-to option for venturing into deep space. However, a new era of space exploration is upon us, characterized by a diverse fleet of spacecraft, including nanosatellites, microsatellites, and even smaller vehicles.
The development of electric propulsion systems for small spacecraft has revolutionized our capabilities, from deep space exploration to covert spy missions. This technology offers a promising solution to the constraints of conventional propulsion systems, providing greater efficiency, extended mission lifetimes, and enhanced maneuverability. In this article, we will explore the significant impact of small spacecraft electric propulsion on both scientific and military applications.
The Rise of Nanosatellites and Microsatellites
Nanosatellites and microsatellites, weighing between 1-10 Kg and 10-100 Kg, respectively, represent the fastest-growing segments in the satellite industry. Advancements in very-large-scale integration (VLSI) electronics have allowed for their miniaturization, and their applications are diverse. They serve purposes ranging from scientific research and communication to navigation, reconnaissance, Earth observation, biological experiments, and remote sensing. Large constellations, equipped with these small satellites, are improving weather predictions, pollution monitoring, and rural-area communications, all while being privatized. It is predicted that by 2025, an astonishing 1000 smallsats will be launched annually.
Propulsion Unleashes Potential
The missions undertaken by microsatellites and nanosatellites are made possible by their propulsion systems. These systems enable these smallsats to perform tasks such as collision avoidance, orbital maneuvering, station-keeping, orbit transfers, formation flights, and even interplanetary trajectories, as exemplified by ESA’s SMART-1 mission and the Mars Cube.
Traditional smallsats in low Earth orbit (LEO) typically rely on reaction wheels and magnetorquers for attitude control but cannot undertake major maneuvers, orbit transfers, or interplanetary missions. However, interplanetary smallsat missions are gaining traction, as seen with 13 cubesats planned for launch on the Artemis 1 mission in 2021.
Tailored Propulsion Solutions
For smallsat propulsion to be effective, several factors must be considered. These include onboard power availability, volume, size, weight, electromagnetic interference, cost-effectiveness, and the specific mission goals. Interplanetary missions, in particular, demand additional considerations such as radiation tolerance and telecommunications design.
Enter Electric Propulsion
Traditional chemical propulsion systems, while powerful, have limitations in terms of fuel capacity and the ability to alter course mid-mission. Electric propulsion systems, on the other hand, utilize electricity to accelerate ions or other propellants, offering a more efficient way to generate thrust.
Space EP is defined as any system that accelerates a propellant through the conversion of electric potential energy into kinetic energy. Broadly, this energy conversion can be electrostatic, electrothermal, or electromagnetic-based. It could also be a combination of both (e.g., electrothermal coupled with electromagnetic).
Electric propulsion is heralding a power revolution in orbit, and ion thrusters are at the forefront of this transformation. These thrusters generate thrust by accelerating ions using electricity. As ionized particles are expelled from the spacecraft, they create a propulsive force in the opposite direction. While electric solar panels usually supply power to ion thrusters, nuclear power is utilized in missions that venture far from the sun.
Advantages of Small Spacecraft Electric Propulsion
Compared to traditional chemical propulsion systems like SpaceX’s Falcon Heavy or NASA’s Space Launch System (SLS), electric propulsion offers several advantages. Electric propulsion systems boast higher fuel efficiency, lower fuel and propellant storage requirements, and can operate continuously for extended periods. This efficiency translates into significant savings, reducing launch vehicle size and costs.
As Michael Patterson, senior technologist for NASA’s In-Space Propulsion Technologies Program, aptly puts it, electric propulsion can be likened to the tortoise in the “Tortoise and the Hare” fable. While traditional chemical propulsion systems provide high thrust for a short duration, electric propulsion systems offer steady thrust over an extended period, resulting in a substantial increase in velocity.
The efficiency of electric propulsion systems reduces costs and opens the door to more economical satellite programs. “To do the same amount of velocity increase on the satellite, we use a fraction of the propellant because it’s five to ten times more efficient.” But this efficiency, translates into big savings, says Ben Olivier, CEO Thales Belfast: “What difference does it make commercially? It probably takes 20% out of the cost of the program because you can use a smaller launch vehicle to put you into your injection orbit, and then do more of the work with your own propulsion sub-system.”
Electric propulsion systems have been in use for decades, but recent advancements have made them more compact, efficient, and reliable, making them ideal for small spacecraft.
- Enhanced Efficiency: Electric propulsion systems are incredibly efficient, providing a continuous low-thrust propulsion, which may operate for extended periods, making them perfect for long-duration missions. These systems offer a higher specific impulse (Isp), meaning they can achieve higher velocities while consuming less fuel.
- Extended Mission Lifetimes: Small spacecraft, powered by electric propulsion, can stay operational for several years, even decades. The extended mission lifetimes are advantageous for both deep space exploration and surveillance missions, as they allow for prolonged data collection and analysis.
- Maneuverability: Electric propulsion enables precise course corrections and orbit changes, which are essential for exploration missions and covert spy missions alike. These systems can efficiently adjust trajectories, making them valuable tools for mission success.
While small spacecraft electric propulsion has already demonstrated its effectiveness, there are still challenges to overcome, including developing even more efficient propulsion systems and minimizing power requirements. Researchers and engineers are continuously working on improving these technologies, which will have a lasting impact on space exploration and defense capabilities.
Applications in Deep Space Exploration
- Scientific Missions: Small spacecraft with electric propulsion systems are ideal for studying distant celestial bodies such as asteroids, comets, and planets. Missions like the NASA Dawn mission to the asteroid belt and the upcoming Europa Clipper mission to one of Jupiter’s moons have benefited from these systems.
- Interstellar Exploration: Electric propulsion has the potential to enable humanity’s journey to the stars. The Breakthrough Starshot initiative aims to use small spacecraft with electric propulsion to reach the closest star system, Alpha Centauri, within a human lifetime.
Applications in Spy Missions
- Covert Surveillance: The use of small spacecraft with electric propulsion is invaluable for intelligence and reconnaissance operations. These spacecraft can be deployed in low Earth orbit to monitor and gather data on potential threats and adversaries. Their long lifetimes and maneuverability make them effective tools for surveillance.
- Rapid Response: Small spacecraft equipped with electric propulsion can quickly be deployed and repositioned in response to emerging threats or crisis situations, making them essential assets for national security agencies.
Race to employ Electric propulsion in Microsatellites and Nanosatellites
NASA is actively enhancing solar electric propulsion (EP) technologies for deep space exploration. NASA’s Glenn Research Center has been at the forefront of developing high-power electric propulsion systems that harness solar energy to convert inert gases into efficient thrust. These improvements aim to reduce transit times, increase payload capacity, enhance spacecraft safety, and lower mission costs by requiring less propellant. Key projects, like the 7-kilowatt (kW) NEXT-C gridded-ion system on the Double Asteroid Redirection Test mission and the 12-kilowatt Advanced Electric Propulsion System on NASA’s Gateway lunar orbiting space station, showcase the agency’s focus on utilizing electric propulsion for exploration and science missions.
Additionally, NASA is advancing electric propulsion for deep space missions near the moon, ultimately preparing for human missions to Mars. The agency envisions the development of an integrated electric propulsion system, including thrusters, power processing units, xenon flow controllers, and electrical harnesses, to support these ambitious missions. The aim is to construct a reusable spacecraft that combines electric and chemical propulsion to facilitate crewed missions to destinations such as Mars, making use of advanced exploration technologies and the high launch capacity of the Space Launch System (SLS) rocket. Through collaborations with companies like Accion, NASA is exploring more efficient ion electrospray propulsion systems to further enhance deep space capabilities.
Over the past five years, NASA’s Small Spacecraft Electric Propulsion (SSEP) project, based at NASA Glenn, has made significant strides in advancing high-performance sub-kilowatt (<1-kW) Hall-effect thruster and power processing technologies, making deep space missions with smaller spacecraft a cost-effective reality. Collaborating with U.S. industry, SSEP has developed a lightweight thruster capable of propelling small spacecraft to destinations like the Moon and Mars, surpassing existing low-power electric propulsion systems tailored for low-Earth orbit missions. Through technological miniaturization, including optimized magnetic field topology and center-mounted cathodes, originally designed for higher-power applications, SSEP propulsion systems achieve the required performance, longevity, and fuel efficiency for planetary missions.
The newfound capability opens doors to missions ranging from lunar communication satellite clusters for data relay to deep space explorations to Venus, Mars, asteroids, and beyond, enabling multiple spacecraft to self-propel to diverse destinations after deployment from a single large rocket. These innovations also hold commercial potential for orbit adjustments, spacecraft servicing, and missions beyond low-Earth orbit, with Northrop Grumman actively developing and testing SSEP-based electric propulsion technologies for their customer satellite systems, with plans for mission launches in 2024. The SSEP project receives joint sponsorship from Northrop Grumman, NASA’s Space Operations Mission Directorate, Space Technology Mission Directorate, and the Science Mission Directorate.
The adoption of electric propulsion in the satellite industry has significantly advanced in recent years, despite having a history of use in long-duration space exploration missions and station keeping. Electric propulsion systems are particularly known for their high efficiency in deploying geostationary telecommunications satellites into orbits at around 36,000 kilometers above the Earth’s surface. One noteworthy achievement in this arena was the completion of the first UK-built electric satellite propulsion module by Thales Alenia Space in November 2018, marking the UK’s entry into the league of established manufacturers like Airbus and Boeing. This module, known as the Spacebus NEO Xenon Propulsion (XPS), was integrated into the Spacebus NEO bus for Eutelsat’s KONNECT communications satellite, showcasing the potential of electric propulsion for commercial satellite applications.
Furthermore, SSL (Space Systems Loral) demonstrated its solar electric propulsion system on two communications satellites launched into geostationary orbit in 2018. Their SPT-140 electric thruster, an enhanced version of the SPT-100, has supported numerous missions and logged an impressive 100,000 hours of firing time. SSL is actively involved in developing a 6kW dual-mode electric propulsion engine as part of NASA’s Tipping Point program, which will be used to power commercial satellites. The significance of electric propulsion in microsatellites is emphasized by India’s space tech startup, Bellatrix Aerospace. In May 2021, they successfully tested India’s first privately built Hall Thruster, a highly efficient electric propulsion system designed for micro-satellites. This innovation holds promise for scaling up propulsion technology to cater to heavier satellites and satellite constellations.
Blue Canyon Technologies, a Colorado-based small satellite supplier, is actively pursuing missions that involve the use of electric propulsion to transport spacecraft from low Earth orbit (LEO) to geostationary orbit (GEO) and even to the Moon. George Stafford, Blue Canyon’s CEO and president, has revealed that these missions are scheduled to take flight within the next few years. Leveraging electric propulsion, satellites can make the journey from LEO to GEO in approximately four months and reach the Moon in about six months, according to Daniel Hegel, Blue Canyon’s advanced development director. This marks a significant shift from the traditional reliance on powerful rockets to achieve such orbital transitions.
In parallel, a small company based in Colorado, Roccor, specializes in deployable space structures and has introduced an innovative product: a compactly stowed full solar wing that can be deployed in orbit. After a rocket delivers the spacecraft to LEO, Roccor’s solar arrays generate several kilowatts of power to facilitate the satellite’s journey to GEO. The impetus behind these advancements is the recognition that launching satellites to geostationary orbits can be cost-prohibitive. This has led to a reluctance among geostationary satellite operators to invest in new spacecraft. The introduction of more efficient electric propulsion systems offers a solution to bridge this gap, providing a more cost-effective means to transport satellites to their desired orbits.
Nanosatellites equipped with ion thrusters are seen as the future of deep space exploration, with the potential to revolutionize space research. Despite their promise, CubeSats, which are often launched as secondary payloads, face limitations due to their lack of self-propulsion once in space. However, researchers like Paulo Lozano and his team at the Massachusetts Institute of Technology have developed mini thrusters that create an electric field, generating a spray of charged ions. While the force produced by these ion thrusters is relatively small, the vacuum of outer space allows for fast movement, enabling CubeSats to maneuver efficiently. This technology, resembling computer microchips with a grid of 500 tiny nozzles, holds promise for interplanetary travel and deep space missions.
Electric propulsion systems like the XPS propulsion module manufactured in Belfast are driving advancements in space exploration. These modules, while not small, offer substantial thrust and fuel efficiency for larger missions. The Spacebus NEO satellite, powered by an all-electric system, is paving the way for future deep space endeavors. With multiple follow-on orders for similar XPS modules, the use of electric propulsion is expected to become increasingly prevalent in space exploration, offering a more efficient and cost-effective means of propulsion for a wide range of missions.
In parallel, India’s ISRO is nearing completion of a 300mN high-thrust electric propulsion system for satellites. This development is poised to eliminate the use of chemical fuels in satellites, leading to lighter spacecraft and reduced fuel weight. Israel is also taking substantial strides in electric propulsion, with the Israel Space Agency (ISA) preparing to demonstrate its 100 percent electric propulsion system on an ISRO-operated small satellite within the next three years. The success of this demonstration will underscore the technology’s capability to maintain satellites in orbit and perform maneuvers relying solely on electric propulsion. Additionally, Israel Aerospace Industries (IAI) is working on upgrading the optical and radar payloads of spy satellites, with plans to develop a new generation of satellites employing nanosatellite production and electric propulsion concepts. These advancements collectively highlight the pivotal role of electric propulsion in satellite development and space exploration.
The Commercial Revolution
Electric propulsion has not only revolutionized space exploration but has also transformed the commercial satellite market. Companies like Thales Alenia Space, Airbus, and Boeing are actively manufacturing all-electric propulsion technology for commercial satellites. These advancements have made it more feasible to launch satellites into geostationary orbit, significantly reducing costs.
Moreover, startups like Bellatrix Aerospace in India are pushing the boundaries by developing highly efficient electric propulsion systems suitable for microsatellites. Their Hall Thruster, powered by saltwater, offers a high thrust-to-power ratio, ideal for powering the satellite constellations expected to launch in the coming decade.
Market growth
The electric propulsion satellite market is poised to grow by USD 10.18 billion during 2020-2024, progressing at a CAGR of about 14%. The market is driven by the growing preference for hosted payload. In addition, the introduction of lightweight amplifiers is anticipated to boost the growth of the electric propulsion satellite market.
The Electric Propulsion Satellite Market is expected to witness remarkable growth, with a forecasted increase of USD 8,534.23 million during the period 2022-2027. The market’s growth is projected to accelerate at a CAGR of 8.56% over the forecast period.
Driving Factors and Market Segmentation
Several key factors are propelling the growth of the electric propulsion satellite market. These include a growing preference for hosted payloads, cost-effective commercial launch vehicles, and increased utilization of electric propulsion satellites in military and defense applications.
Many government agencies prefer hosted payload approach as it helps them achieve cost-effectiveness and eliminates the need for building a dedicated satellite. This approach also reduces the risk of inadequate funding, launch delays, and operational failures. Over recent years various government and defense organizations have adopted the hosted payload approach. Companies such as Boeing are offering all-electric satellites specifically designed to facilitate hosted payloads for defense applications. During the forecast period, many such commercial satellites are expected to accommodate hosted payloads for defense and government applications. These factors are expected to fuel the growth of the global electric propulsion satellite market.
Sustainable Satellite Operations and Demand for Small Satellites
One of the prime drivers of the electric propulsion satellite market is the increasing emphasis on sustainable and green satellite operations. As the industry continues to adopt environmentally friendly practices, the demand for electric propulsion satellites is expected to surge. Additionally, the market is benefiting from the growing demand for small satellites and the focus on long-duration missions and deep space exploration.
China and India are the key markets for electric propulsion satellites in APAC. Market growth in this region will be faster than the growth of the market in other regions.
Aerojet Rocketdyne Holdings Inc., Airbus SE, Ball Corp., Boeing, Lockheed Martin Corp., Mitsubishi Electric Corp., Northrop Grumman Corp., Lockheed Martin, Mitsubishi Electric, OHB SE, Safran SA, Thales Group, and The Boeing Co. are some of the major market participants.
Major Five Electric Propulsion Satellite Companies:
Key electric propulsion satellite market vendors include Accion Systems Inc., Ad Astra Rocket Co., Aerojet Rocketdyne Holdings Inc., Airbus SE, Bellatrix Aerospace Pvt. Ltd, Busek Co. Inc., INVAP S.E., Lockheed Martin Corp., MIT AeroAstro, Northrop Grumman Corp., OHB System AG, Safran SA, Sitael S.p.A., Thales Group, The Boeing Co., and ThrustMe.
Aerojet Rocketdyne Holdings Inc.
Aerojet Rocketdyne Holdings Inc. operates its business through segments such as Aerospace and Defense and Real Estate. The company offers Electric Propulsion systems that uses electricity to accelerate a propellant to produce thrust.
Airbus SE
Airbus SE operates its business through segments such as Airbus, Helicopter, and Defence and Space. The company offers numerous products including SES12, SES14, and Eutelsat 172B.
Ball Corp.
Ball Corp. operates its business through segments such as Beverage Packaging, North and Central America, Beverage Packaging, South America, Beverage Packaging, Europe, and Aerospace. The company offers solar electric power-based propulsion technologies, capabilities, and infrastructure required for sustainable, affordable human presence in space.
Lockheed Martin Corp.
Lockheed Martin Corp. operates its business through segments such as Aeronautics, Missiles and Fire Control, Rotary and Mission Systems, and Space. The company offers High Power Hall Current Thruster (HPHCT) electric propulsion system.
Mitsubishi Electric Corp.
Mitsubishi Electric Corp. operates its business through segments such as Energy and Electric Systems, Industrial Automation Systems, Information and Communication Systems, Home Appliances, and Other. The company offers hybrid and electric propulsion systems.
The Future Beckons
With the propulsion technology revolution still in its infancy, exciting prospects await. As we scale down electric propulsion technologies to fit smallsats, a host of opportunities emerge for ambitious deep space missions. The ability to launch clusters of smallsats into space, each propelled to different destinations of interest, opens a new frontier in exploration.
In summary, small spacecraft electric propulsion is a game-changer for space exploration, bringing the Moon, Mars, and beyond within reach. Its cost-effectiveness, extended mission lifetimes, and versatility in maneuverability make it a crucial component in the future of space exploration. As we continue to innovate and push the boundaries of what’s possible, the smallsats powered by electric propulsion systems are bound to lead the way in our journey to the stars.
