Micro and nano scale devices for space applications not only have to endure extreme temperature and thermal cycles but also encounter extreme shock, vibration and radiation ambient. Although these systems are inherently more resilient to shock due to their small mass; shock and vibration during lift-off and other satellite manoeuvres do present an opportunity for failure such as nucleation of a micro-crack in a stressed microstructure or breakage of a package interconnect. Radiation can impact MEMS devices in three ways: (i) breakdown of board analog and digital microelectronics components for micromachined transducers, (ii) detrimentally effect the transduction mechanism, and (iii) cause a catastrophic failure of the mechanical components of MEMS.
Current Qualification Strategies for Components for Space Applications
The second part of the concept paper reviews the current qualification strategies for critical structural components used in space applications. Interagency missions such as the international space station (ISS) and established flight programs (e.g. NASA shuttle program) have established testing methodologies, design and analysis requirements, accepted materials systems, and reporting requirements for hardware for both manned and unmanned missions. Both electronic and structural systems are rigorously designed, analyzed, and qualified before placed into service.
Integrated circuits are based on a well-defined unit, the transistor. By understanding the performance of an individual transistor and the physics associated with its failure, it is possible to institute testing methodologies that screen for defective parts. In many cases, such testing programs utilize “burn-in” strategies that subject components to severe conditions intended to facilitate the identification of inferior components.
Methodologies for the design, qualification, and verification of critical structural components in space flight hardware have been established. A vast array of standard handbooks and documents outline general good practice, factors of safety, and other crucial details for insuring reliable structural components. Additionally, general statistical techniques, finite element methods, and other software and analytical tools have been codified.
The current qualification strategies show that notable progress has been made in engineering fracture mechanics, structural and electronic design, and other key aspects of engineering. However, it is difficult, if not impossible, to extend these testing methodologies directly to MNT. The development of increasingly complex micro- and nanosystems make the analysis, testing, qualification, and verification of every subsystem intractable. An alternative approach must be established if MNT can play a critical role in future space missions.
