Radiation Hardness Assurance: VPT’s Approach to NewSpace DC-DC Converter Reliability
The VSC Series: Balancing Affordability and Performance
In recent years, there has been an increasing trend toward the use of commercial off-the-shelf (COTS) electronics in space; the motivations are simple. Compared to their space-qualified counterparts, COTS components can dramatically reduce cost and lead-time. For example, a voltage reference qualified to MIL-PRF-38535 Class V may cost on the order of $400 each and have a lead time of several months. Meanwhile, the equivalent part can be ordered and received from a distributor in less than a week for $1 each. Furthermore, modern COTS electronics often offer increased integration and improved performance in smaller and lighter packaging, ultimately enabling smaller satellites with reduced launch cost.
On the other hand, neither cost nor schedule are improved if the COTS electronics fail a week after launch or even 1 or 2 years into a 3, 5, or 10 year mission. The space environment is extremely harsh, especially due to its natural radiation environment. Manufacturers of space-qualified electronics implement thorough radiation hardness assurance (RHA) plans to guarantee their parts will survive. They sacrifice cost and lead time to eliminate risk and bring a highly reliable solution to the market with guaranteed by design and radiation performance. COTS electronics are more affordable, but offer no radiation guarantees. Using COTS implies accepting risk.
At the interface between risk elimination and risk acceptance is a relatively new paradigm often termed NewSpace. NewSpace applications attempt to balance risk against cost and schedule. Manufacturers and designers offering products to this emerging market will succeed or fail based on how well they strike that balance and how well they communicate their risk mitigation strategies to their customers.
Given that radiation is a paramount risk factor, it is crucial for anyone entering the NewSpace market to quickly develop a thorough and cost-effective RHA plan. For those new to radiation tolerant applications, this will be a daunting task and examples will be instructive. To this end, this white paper summarizes key portions of VPT’s RHA plan for its VSC Series of NewSpace DC-DC converters. While the examples pull from the VSC Series, the ideas and methods are broadly applicable to other types of components and circuits. Section II provides a high-level overview of the RHA plan. Section III demonstrates our methods for radiation lot acceptance testing (RLAT). Sections IV and V share our approaches to module-level total-ionizing dose (TID) and single-event effect (SEE) testing, respectively.