Small satellites are becoming increasingly popular tools for Earth-imaging, communications, and other applications. But they have major control issues: Once in space, they can’t accurately point cameras or change orbit, and they usually crash and burn within a few months.
What these satellites lack is a viable propulsion system.
Accion Systems has developed a commercial electrospray propulsion system — their first is about the size of a pack of gum — made of tiny chips that provide thrust for small satellites. Among other advantages, Accion’s module can be manufactured for significantly less than today’s alternatives.
This technology could enable low-cost satellites, such as those known as “CubeSats,” to become more viable for various commercial and research applications, including advanced imaging and communications, where numerous satellites could provide global coverage.
Electric propulsion (EP) provides momentum for propelling spacecraft (in space, not for launch) by converting electrical energy into kinetic energy. Charged particles are electromagnetically accelerated within the propulsion device, and the opposite momentum reaction forces the spacecraft in the other direction. This is in contrast to chemical propulsion, which utilizes the exchange from chemical energy to kinetic.
Highly efficient use of propellant. EP systems provide more thrust per unit propellant compared to chemical systems. For the same mission, an EP system can use up to 1000 times less propellant by mass.
In January, Accion tested a miniature version of MAX-1, called MIN-0, inside a vacuum chamber at MIT. The team measured the emitted current of the released ions after applying certain levels of voltage. From that experiment, and others, they conclude the MAX-1 can provide about 100 micronewtons of force per square meter.
This is enough thrust, for example, to stabilize a CubeSat launched from the International Space Station, and to compensate for atmospheric drag, “which is the force that pulls [small satellites] into the atmosphere prematurely, where they burn up,” Brikner says.
However, with dozens of small satellites being launched annually, Lozano adds, the system could also help control how long they stay in space, so they don’t become floating space junk.
With that novel propellant, and a simple design, Accion can batch-manufacture modules — much like computer chips — in quantities of around 200 at once. According to Brikner, this costs about one-tenth as much as other electric-propulsion systems.
Schematic of Accion thruster chip. Propellant is supplied from the tank to the emitter tips. Ions are extracted by the strong electric field applied between the tips and the extractor.
Max-1 thruster chip for cubesats is the first configuration and first product. Accion’s first commercial system is MAX-1, a module comprising eight chips — each about 1 square centimeter, and 2 millimeters thick — that can be applied anywhere on a satellite.
Similar to traditional ion engines, our systems produce thrust using electric fields to accelerate ions. Ions leave the thrusters through small holes in the extractor grids over each chip, and propel the spacecraft in the opposite direction.
Rheir thrust-producing ions are supplied from our ionic liquid propellant—a safe, non-toxic liquid salt that we store in passive plastic tanks. This novel source of ions is referred to as an ionic liquid ion source, and allows us to get rid of big ionization chambers, pressurized tanks, bulky valves, and external cathodes for neutralization. The result? Higher thrust-to-mass, higher thrust-to-volume, and lower power than today’s ion engines, not to mention the ability to qualify for rideshare launches.
Their systems comprise individual thruster chips that can be positioned anywhere, in any number on the satellite. We can accommodate any shape or propulsion requirement.
But perhaps the biggest difference is in our manufacturing process. They use low-cost, hands-off batch manufacturing processes. If space is truly going to be accessible to everyone, they can’t keep manufacturing propulsion systems like jewelry. Today, they make 44 thruster chips in one run.
SOURCES- Accion systems, MIT Technology Review