There is no stopping the exponential growth of the small satellite market. From 2012 to 2016, the average satellite weight went down by almost 80 %. Since then, the number of small satellites launched in orbit has risen by 300 %. Yet, as the segment gets propelled by rising demand and new technology, actual satellite propulsion systems are falling behind. You could sum up their shortcomings in two words: hazardous and expensive. And whilst alternatives do exist, their performance generally disappoints.
First of its kind
There is one exception though. “EPSS is a first-of-its-kind high-performance satellite propulsion system. It uses a non-toxic green chemical monopropellant (ammonium dinitramide), is 10 times cheaper than alternatives, and is 30 % more effective than its closest competitors,” says Vytenis Buzas, CEO of NanoAvionics. The EPSS 2 (Enabling Chemical Propulsion System for the Growing Small Satellite Market) venture started in 2016 with the objective of developing and piloting low-cost, high-performance propulsion systems using an environment-friendly propellant for satellites weighing less than 150 kg. “The need for such a propulsion system was significant,” Buzas recalls. “Propulsion systems enable satellites to perform complex tasks which are critical to delivering high-value services. These include precision flight in constellations, orbital manoeuvring, avoiding space debris, synchronisation and positioning of communication equipment and payload instruments, atmospheric drag compensation and subsequent lifetime extension, as well as de-orbiting at mission end.” A propulsion system basically enables small satellites to provide contemporary satellite services: remote sensing, radio and optical astronomy, space exploration for governmental and private science missions, atmospheric studies and weather forecasting, communications and broadcasting, navigation, security, search and rescue, and the Internet of Things (IoT). With EPSS, such missions benefit not only from a green label and reduced cost, but also from significant thrust and burn duration.
A simple yet reliable architecture
So how does it work exactly? “The EPSS inherits a relatively simple yet reliable architecture – consisting of a propellant tank, flow control block and a thruster – and utilises a monopropellant blend,” explains Erikas Kneižys, CDO of NanoAvionics. “The propellant tank features an active thermal management system and uses a blow-down configuration with an elastomeric membrane separating pressurant and propellant. The flow control block, on the other hand, consists of a latching valve, pressure sensor, system filter and two isolation valves in series acting as flight control valves. Finally, the thruster chamber features a catalyst as well as heaters. Firing of the thruster occurs when the Engine Control Unit (ECU) actuates the solenoid valves, thereby opening a flowpath of propellant. As the propellant flows to the decomposition chamber and is injected onto a pre-heated catalyst bed located inside the thruster decomposition chamber, the decomposition reaction begins and energy is released, generating thrust promptly.” Reductions in manufacturing costs arise from the use of in-house optimised instrumentation and components, but also and most importantly from the catalytic system located in the decomposition chamber of the thruster. Phase 2 of the SME Instrument-supported project was completed in September 2019. The system has already been brought to TRL 9 through orbital demonstration, and integration and flight with commercial customers’ satellites has begun. These customers can now benefit from the likes of longer mission lifetime, more efficient orbital control and shorter constellation deployment time.
EPSS 2, small satellite, propulsion, propellant, ammonium dinitramide