The path to the Moon, Mars, and beyond will require a fleet of spacecraft in many different shapes and sizes, that would require massive rockets that produce millions of pounds of thrust to spacecraft electric propulsion.
Nanosatellite and microsatellite refer to miniaturized satellites in terms of size and weight, in the range of 1-10 Kg and 10-100 kg, respectively. These are the fastest-growing segments in the satellite industry. Advancements in very-large-scale integration (VLSI) electronics have allowed for the miniaturization of smallsats. Nanosatellites and microsatellites find applications in scientific research, communication, navigation and mapping, power, reconnaissance, and others including Earth observation, biological experiments, and remote sensing. Large constellations performing remote sensing, weather predictions, pollution monitoring, and improving communications in rural areas are being privatized. It is projected that by 2025, there will be 1000 smallsats launched per year.
Microsatellite and nanosatellite missions are enabled by their propulsion which provides smallsats with; collision avoidance, orbital maneuvering, station keeping, orbit transfers, formation flights, and interplanetary trajectories as demonstrated by ESA’s SMART-1 mission and the Mars Cube. Traditional smallsats orbit in low Earth orbit (LEO) and rely on reaction wheels and magnetorquers to provide attitude control and stability for instruments. They cannot maneuver, transfer orbits or design safe de-orbit strategies nor can they go interplanetary. Interplanetary smallsat missions are becoming more popular with 13 cubesats planned to launch on the Artemis 1 mission in 2021.
To provide effective propulsion for smallsats, the available onboard power, the volume, size and weight, electromagnetic interference, cost-effectiveness, and the mission goals should be considered. Interplanetary smallsats, require additional radiation tolerance and telecommunications design.
A new power revolution is going on in orbit – that of electrical propulsion for satellites. An ion thruster is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions with electricity. As the ionised particles escape from the aircraft, they generate a force moving in the other direction. Power supplies for ion thrusters are usually electric solar panels, but at sufficiently large distances from the sun, nuclear power is used.
Chemical propulsion systems used on SpaceX’s Falcon Heavy or NASA’s Space Launch System (SLS) have low specific impulses (Isp) thus poor fuel efficiency, very high thrust, short acceleration times, and high mass. Electric propulsion (EP) has higher fuel efficiency so less fuel and propellant storage is required, hence EP is more suitable for smallsats.
Michael Patterson, senior technologist for NASA’s In-Space Propulsion Technologies Program compared ion and chemical propulsion with “Tortoise and the Hare”. “The hare is a chemical propulsion system and a mission where you might fire the main engine for 30 minutes or an hour and then for most of the mission you coast.” “With electric propulsion, it’s like the tortoise, in that you go very slow in the initial spacecraft velocity but you continuously thrust over a very long duration — many thousands of hours — and then the spacecraft ends up picking up a very large delta to velocity.”
“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.”
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).
Race to employ Electric propulsion in Microsatellites and Nanosatellites
Electric propulsion for satellites, is of course, not new and ion engines, plasma thrusters have been used for long-duration space exploration probes, as well as station keeping and altitude control. (Indeed, ESA’s BepiColombo Mercury probe, which launched in October, uses Solar Electric Propulsion System (SEPS) ion engines from UK’s QinetiQ.) However, in recent years, it has begun to transform the commercial satellite market – thanks to its ultra-high efficiency in raising geo-telecommunication satellites into geostationary orbits of 36,000km.
In early November 2018, the first UK-built electric satellite propulsion module was completed by Thales Alenia Space from its new facility in Belfast. With this, the UK joins Airbus in Germany, and Boeing in the US as a new manufacturer of all-electric propulsion technology for commercial satellites. This engine module, the Spacebus NEO Xenon Propulsion (XPS) was delivered to Thales Alenia Space’s satellite factory in Cannes, France, for integration into the Spacebus NEO bus for Eutelsat’s KONNECT communications satellite.
SSL demonstrated its solar electric propulsion system on two communications satellites that were launched into geostationary orbit in 2018. The Maxar Technologies subsidiary said SPT-140 is an updated version of the SPT-100 electric thruster that has supported 34 missions and logged more than 100K firing hours. SPT-140 is designed to use the Power Processing Unit 140 and multiple gimbaled Hall effect thrusters to generate electric power of up to 8 kilowatts. NASA awarded SSL in August a contract to further develop a 6kW dual-mode electric propulsion engine as part of the space agency’s Tipping Point program. The company will also provide a solar electric chassis to help NASA send a probe to the metal-based asteroid Psyche and noted it will use SPT-140 to power four commercial satellites.
In a first in India, space tech startup Bellatrix Aerospace reported in May 2021 that it has successfully tested the country’s first privately built Hall Thruster, a highly efficient electric propulsion system that’s ideal for micro-satellites weighing 50-500 kg and can be scaled up for heavier satellites. Spacetech startup Bellatrix Aerospace’s Hall Thruster is a highly efficient electric propulsion system that’s ideal for microsatellites weighing 50kg to 500kg and can be scaled up for heavier satellites. Bellatrix is working towards flying this thruster on a satellite mission in the coming months. We have designed this thruster with numerous considerations that make it an ideal engine to power the major satellite constellations that will be launched during this decade. Our Microwave Plasma Thrusters offer the highest thrust-to-power ratio for heavier satellites”, says Bellatrix CEO and CTO Rohan M Ganapthy.
India is also working on electric propulsion according to Dr. Sivan ISRO Chairman K.Sivan, “For satellites we are in the final stages of developing a 300mN high-thrust electric propulsion system. This will eliminate use of chemical fuels in satellites and result in lighter satellites by saving on fuel weight” he said.
The Israel Space Agency (ISA) is set to demonstrate its 100 percent electric propulsion system by launching it on Indian Space Research Organisation’s (ISRO) small-sized satellite in the next three years. This demonstration will go on to show the use of this technology in keeping satellites in orbit and ensuring a required manoeuvre based merely on electric propulsion. Israel Aerospace Industries (IAI) is working to upgrade the optical and radar payloads of the spy satellites serving the nation’s intelligence community. The company is developing a new generation of satellites for even more complex missions, using nanosatellite production and electric propulsion concepts.
Electric propulsion to send smallsats from LEO to GEO orbit, moon
Blue Canyon Technologies, a small satellite supplier based in Boulder, Colorado, is bidding on two missions to transport spacecraft from low Earth to geostationary orbit with electric propulsion in addition to a mission to send a satellite from low Earth orbit to the moon. The missions are scheduled to fly within the next couple of years, said George Stafford, Blue Canyon chief executive and president. With electric propulsion, it will take a satellite about four months to move from low Earth to geostationary orbit and six months to reach the moon, said Daniel Hegel, Blue Canyon advanced development director.
Roccor, a small company based in Longmont, Colorado, that specializes in deployable space structures, has developed a new product it intends to market: a full solar wing that can be stowed compactly for launch and deployed in orbit, Doug Campbell, Roccor chief executivesaid. After a rocket drops the spacecraft off in low Earth orbit, Roccor solar arrays will generate “several kilowatts of power” to move it to geostationary orbit, said Campbell.
“It is expensive to launch satellites to geostationary orbit,” Campbell told SpaceNews during an interview at the Small Satellite Conference here. “We see this as a huge unmet need.” Because the satellite industry is going through a period of rapid change, some geostationary satellite operators have been reluctant to invest in new spacecraft. The cost calculation would change if spacecraft could travel from low Earth to geostationary orbit, Stafford told SpaceNews during an interview at the Small Satellite Conference.
In the past, satellites booked rides to their desired orbit because most electric propulsion systems were not powerful enough to help them move from low Earth to geostationary and the systems that would have made that possible were prohibitively expensive, Hegel said.
Nano satellites, equipped with ion thrusters for Deep space Exploration
Now, aerospace suppliers and governments across the globe see the tools as the future of deep space exploration, like Paulo Lozano, director of the Space Propulsion Lab at the Massachusetts Institute of Technology, said sending the tiny satellites to asteroids could help improve space research (or even save the planet from an asteroid attack, he said). However they have limitations of lacking self propulsion. “One of the big limitations in CubeSats is that they are launched as secondary payload. They cannot move once they are in space, they cannot move,” Lozano said.
Lozano’s team designed a set of mini thrusters that create an electric field that tugs on the charged particles in salt water until they peel off. The result is a spray made of charged molecules called ions. This ion spray doesn’t create a lot force. It’s always less than a millinewton, which is akin to the force produced when a mosquito lands on your arm. But the spray moves very fast, and even a small action creates a reaction in the frictionless vacuum of outer space. Use this to move ions in one direction, and a CubeSat will move uber fast in the other.
The thrusters, which look like computer microchips, are the size of quarters. The chips contain a grid of 500 needles — each a custom-built nozzle for spewing ions. His team tests them inside a large vacuum chamber at their lab in Boston.
Scientists are now researching mini boosters that shall enable CubeSats to stay in space. Lozano team has developed small electric thrusters using static electricity and tiny drops of salt water. “Dr. Lozano’s system is probably the frontrunner for the possibility for deep space missions,” Lemmer said. “In order to go interplanetary, you’re going to have to have an electric propulsion system because they are so much more efficient.”
Electric thrusters promise space revolution
This XPS propulsion module, manufactured in Belfast, for the Spacebus NEO is not some tiny thruster, but a 1.8tonne module fully fuelled, that stands 1.8m high and 3.6m wide and features Xenon propellant tanks with the gas compressed to 125bar. “it’s not a trivial piece of equipment” says Olivier, “You’re talking about fluidic titanium piping, pressure regulation and pressure management and systems, valves, etc. And two axis mechanisms to vector the thrust and all the flexible piping to transmit the xenon efficiently. All of that has got to work in the extreme environment of space, and survive launch.“
With the Eutelsat KONNECT being the first all-electric Spacebus NEO satellite from Thales Alenia Space, it also has three more follow-on orders in the pipeline, with the next one a XPS module for the French military Syracuse satellite, then commercial operator SES and another satellite for Eutelsat. “We expect more to be sold” says Olivier.
NASA Works to Improve Solar Electric Propulsion for Deep Space Exploration
One of the Technology Area (TA) of NASA’s Mars roadmaps is In-Space Propulsion Technologies that addresses the development of higher-power electric propulsion, nuclear thermal propulsion, and cryogenic chemical propulsion. Improvements derived from technology candidates within this TA will decrease transit times, increase payload mass, provide safer spacecraft, and decrease costs.
For decades, innovators at NASA’s Glenn Research Center have been developing large, high-power electric propulsion (EP) systems that harness the power of the Sun to energize inert gases and turn them into extremely efficient thrust. Higher fuel efficiency means less propellant is needed, lowering launch costs while allowing spacecraft designers to reduce overall spacecraft weight to carry more payload mass, like technology demonstrations or more powerful scientific instruments.
The agency’s primary EP efforts have centered on large exploration and science missions, like the 7-kilowatt (kW) NEXT-C gridded-ion system currently flying on the Double Asteroid Redirection Test mission and the 12-kW Advanced Electric Propulsion System used on the Power and Propulsion Element for NASA’s lunar orbiting space station known as Gateway.
DART is a kinetic impact mission designed to collide with a moonlet around the Didymos asteroid and slightly alter its orbit. This mission will be a critical step in demonstrating NASA’s impact threat mitigation capabilities for redirection of a potentially hazardous object such as an asteroid.
Serving as the primary propulsion source for DART, NEXT-C will establish a precedent for future use of electric propulsion to enable ambitious future science missions,” said Eileen Drake, CEO and President of Aerojet Rocketdyne. “Electric propulsion reduces overall mission cost without sacrificing reliability or mission success.” Under a cost-sharing agreement with NASA’s Science Mission Directorate through the agency’s Glenn Research Center, Aerojet Rocketdyne is developing the NEXT-C electric propulsion engine and power processing unit. In addition to DART, additional NEXT-C units may be launched on future NASA planetary missions.
NASA’s Evolutionary Xenon Thruster-Commercial (NEXT-C) was developed by NASA and is being commercialized by Aerojet Rocketdyne. NEXT-C has 7kW of maximum power and greater than 4100s specific impulse (Isp). Its high Isp and flexible operational capabilities make NEXT ideal for scientific space missions.
NASA is leading the next steps into deep space near the moon, where astronauts will build and begin testing the systems needed for challenging missions to deep space destinations including Mars. Under a program dubbed Deep Space Gateway, agency officials said they still plan to use the lunar orbit as a staging platform to build and test the infrastructure and the systems needed to send astronauts to Mars. But instead of breaking off a chunk of asteroid and dragging it to the moon, NASA’s new plan calls for building an orbiting spaceport that could have even more uses.
Aerojet Rocketdyne will oversee the development and delivery of an integrated electric propulsion system consisting of a thruster, power processing unit (PPU), low-pressure xenon flow controller, and electrical harness. NASA has developed and tested a prototype thruster and PPU that the company can use as a reference design. The company will construct, test and deliver an engineering development unit for testing and evaluation in preparation for producing the follow-on flight units. During the option period of the contract, if exercised, the company will develop, verify and deliver four integrated flight units – the electric propulsion units that will fly in space.
This spacecraft would be a reusable vehicle that uses electric and chemical propulsion and would be specifically designed for crewed missions to destinations such as Mars. The transport would take crew out to their destination, return them back to the gateway, where it can be serviced and sent out again. The transport would take full advantage of the large volumes and mass that can be launched by the SLS rocket, as well as advanced exploration technologies being developed now and demonstrated on the ground and aboard the International Space Station.
In October 2019, Accion was awarded a USD 3.9 million as part of the Moon to Mars technology program. As per the contract, Accion will work with NASA’s Jet Propulsion Laboratory (JPL) to replace the cold gas propulsion system that was used on the MarCO CubeSats with a more efficient ion electrospray propulsion system. The program is scheduled to initiate in March 2020, and a potential space launch is expected in the first half of 2021.
NASA Small spacecraft Electric Propulsion (SSEP)
However, over the last five years, the Small Spacecraft Electric Propulsion (SSEP) project at NASA Glenn has been advancing high-performance sub-kilowatt (<1-kW) Hall-effect thruster and power processing technologies to enable smaller spacecraft. By utilizing smaller craft – those that could fit inside the trunk of your car versus being the size of your car – the agency opens more opportunities to conduct ambitious deep space missions at a fraction of the cost.
In collaboration with U.S. industry, SSEP has developed a lightweight thruster capable of propelling a small spacecraft from Earth to the Moon, Mars, and beyond – a step up from most existing low-power electric propulsion systems produced commercially for low-Earth orbit operations.
“Scaling down the size and power of Hall-effect thruster technologies, while retaining exceptional propulsive performance, has been a challenge,” says Gabriel Benavides, the lead engineer with the SSEP project at NASA Glenn. “It’s like asking a toy-sized car to drive across country with the same range and functionality of a full-sized passenger vehicle.”
Glenn researchers have been able to miniaturize key technologies to create the new thrusters. For example, the SSEP propulsion systems use an optimized magnetic field topology and center-mounted cathode, which were originally developed for advanced medium and high-power applications. Such technologies are key to achieving the performance, very long life, and fuel efficiency required for planetary missions.
Mission developers envision deploying small spacecraft for everything from a cluster of small, orbiting lunar communication satellites to relay data from Moon rovers and astronauts back to Earth, to deep space science missions to Venus, Mars, asteroids, and even the outer planets.
“Dozens of small spacecraft can fit inside the payload fairing of a single large chemical rocket launched into space,” explains Benavides. “Once deployed, they can each be self-propelled to different destinations of interest.”
While NASA looks to SSEP to self-propel small spacecraft into deep space, these technologies could be used for commercial needs closer to Earth. Commercial space-related applications include adjusting spacecraft in orbit, spacecraft servicing, and missions beyond low-Earth orbit to geosynchronous orbit or even the Moon.
Under a research license with Glenn, Northrop Grumman is using NASA’s design drawings, materials specifications, and test data to develop selected electric propulsion technologies for their customer satellite systems.
The company is currently testing their own variant of the SSEP system in Glenn’s Electric Power and Propulsion Laboratory vacuum chambers over the next two years and hope to launch their first mission using this technology in 2024. The SSEP project is jointly sponsored by Northrup Grumman, NASA’s Space Operations Mission Directorate, Space Technology Mission Directorate, and the Science Mission Directorate.
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.
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.
The increasing demand for miniaturized satellites for feeding information about fertile land, rainfall pattern, and water distribution to the farmers will significantly influence electric propulsion satellite market growth in this region. 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:
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 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. 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.