6 minute read
How COTS and RHBD are democratizing space exploration
The space industry has been rather conservative over the past decades, but a revolution is coming. New components are making space exploration more accessible. So-called COTS semiconductor devices unlock entirely novel applications and help make technology more reliable, bringing space exploration to a new era.
Wei Shu, PhD, CTO of Zero Error Systems
For decades, the space industry, predominantly governed by governments and space agencies, has maintained an unwavering conservatism, placing heavy reliance on space-grade semiconductor components known for their exceptional reliability. However, these components come at a steep cost, exhibit dated performance characteristics, and are often challenging to procure. These Radiation Hardening by Process (RHBP) semiconductor solutions are manufactured with special materials and proprietary foundry processes with stringent qualification test criteria that ensure zero defects under radiation.
Such manufacturing facilities can easily cost billions of dollars. The return on investment (ROI) has traditionally been lengthy, due to the fact that there were relatively few satellite launches in the past. Only big semiconductor manufacturers were able to afford such expensive manufacturing facilities. The result was fewer space-grade semiconductor options for satellite companies along with higher price tags for such space-grade components.
Low Earth Orbit (LEO) satellites that provide communication, data access, earth observation, and surveillance services are not able to afford such expensive space-grade components due to constant pressure by their end customers (e.g. service providers) to keep the system delivery price down. Hence, many satellite companies now build their satellite electronics systems with Commercial-Off-the-Shelf (COTS) semiconductor devices to meet the lower cost requirement and to attain higher processing capability to support the sophisticated space missions.
The Rise Of New Space Players And Cots Components
State-of-the-art COTS semiconductor components play a pivotal role in the emergence of new space movements. New space players are non-traditional satellite subsystem or space electronics manufacturers that want to apply niche computing, imaging, or AI capabilities in space applications. Due to the availability of low-cost satellite building kits and associated COTS semiconductor solutions via the Internet, small teams have begun to build their own satellites and develop applications on them. COTS semiconductor devices unlock entirely novel applications that were once deemed impossible, such as AI deployment and data centers in space.
However, the widespread adoption of cutting-edge COTS components in space faces a significant obstacle: radiation in the extraterrestrial environment. These COTS devices are not meant to thrive in high-radiation environment. Heavy ions in space can cause single event effects such as single event latch-up (SEL) which is a type of short circuit that results in mission failure. It can also cause a single event upset (SEU) that causes bit flip. For example, ‘0’ becomes ‘1’ and vice versa, which corrupts the data. Service providers that launch these satellites suffer major losses when the system fails in space as a satellite can easily cost hundreds of millions of dollars. These failed satellites also become space debris.
According to ESA’s space debris office, it is estimated there are 36,500 objects larger than 10cm; one million objects between 1 and 10cm; and 130 million objects between 1mm and 1cm in orbit. While only a few collisions have been documented so far, each one creates more debris. The more debris, the likelier further collisions become.
RADIATION ISSUES AND SHORTENED LIFESPANS
Commercial satellites, which often serve critical functions, demand a minimum operational lifetime of five to seven years but with COTS, the lifespan is significantly lower due to single event effects. Radiation protection for COTS components is a multifaceted challenge. While passive shielding using thin aluminum films effectively mitigates accumulated radiation effects, it cannot address single event effects, as energetic particles can easily penetrate through shielding and cause damage to semiconductors. In essence, effective protection against single event effects requires active electrical measures. This gives rise to Radiation Hardening by Design (RHBD) semiconductor solutions.
WHY RHBD IS A GAME CHANGER
RHBD at the silicon level is probably the most challenging but effective approach. It is challenging because it achieves radiation hardening by solely relying on integrated circuit designs based on standard complementary metal-oxidesemiconductor (CMOS) processes, which are readily available in all semiconductor foundries. Unlike Radiation Hardened by Process (RHBP) devices, no proprietary process is involved. It is effective because it fundamentally resolves the weakness of standard CMOS processes and hardens it at the circuit level. RHBD at the component level is arguably the most optimized approach as it achieves radiation hardening with minimum overhead and effort by directly hardening COTS components against radiation. Figure 1 depicts one comprehensive approach of RHBD hardening for a COTS component such as Field Programmable Gate Array (FPGA), micro-Controller (µC) and micro-Processor (µP). This approach serves to improve power reliability and data integrity of the COTS component.
POWER RELIABILITY AND DATA INTEGRITY
Specifically, power reliability is deemed one of the most critical vulnerabilities. Enhancing power reliability is twofold. First, the direct current (DC) power regulator must be reliable so as to provide a robust and constant output voltage. It is already challenging for state-of-the-art COTS on earth, and radiation in orbit makes it even harder. Second, as COTS suffer from micro-SEL, the short circuit effect in the long run will severely shorten the lifetime of COTS components, hence the lifetime of satellites.
Data integrity, on the other hand, is critical for dataintensive digital applications, and is often quantified by soft error rate. It is generally very challenging to reduce soft error rate, particularly for COTS memory devices. Triple Modular Redundancy (TMR) is a common approach to ascertain data integrity.
THE FUTURE OF SPACE EXPLORATION: COTS AND RHBD WORKING TOGETHER
In short, RHBD at the component level is probably the most efficient approach for space applications, as it enables virtually all COTS components to function in space at substantially lower cost and minimum overhead.
The space industry is currently at the cusp of a revolution, and it is becoming increasingly evident that this transformation will significantly hinge upon the adoption of advanced COTS semiconductor components combined with effective RHBD approaches. Depending on the risk tolerance and budget constraints of each project, one of the RHBD methods mentioned would be a suitable choice. In short, the convergence of cutting-edge COTS technology and robust RHBD strategies holds immense promise for shaping the future of space exploration and satellite missions.
