## 4 Specific to UAS Technology  
It is clear that an understanding of which research problems are specific to a class of UAS is required to determine how research resources should be invested and on which Groups research goals should be pursued in order to yield advances in the field. It is also apparent that a class of UAS may improve because it relies on technology that is being improved by other fields but not driven by the UAS industry or academia. We will attempt to determine which technology areas are likely to need research and development targeted only at UAS. Table 2 shows that the specific UAS problems are primarily in the domains of the micro UAS/Group 1, XA and UCAV. The group with the largest number of unique research issues is micro UAS. Many of the systems must be smaller than available COTS systems, and some components might require advances in basic technologies such as materials and actuators. Burgeoning issues like flapping wing flight will need to be addressed as UAS approach the size and mass of insects, in which even the conceptual framework for design is the topic of research and debate. Many of these issues have no correlate to non UAS systems, and are not relevant to any other group of UAS. The operational demands for autonomy of small UAS appears to be higher than for autonomy in larger UAS. Collision avoidance, flight inside buildings and swarming are enduring concepts amongst funding agencies for over 15 years [12, 42]. Groups 1 to 4 have few unique pressing aeronautical concerns that would be aided by research. Most of the subsystems that are critical to performance are driven as much by the manned aircraft industry, hobby industry or mass-market appliances. Much of the work will be normal product engineering. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Subsystem** & **Micro UAS** & **Tier 1** & **Groups 2–3** & **Groups 3–5** & **XA** & **UCAV** \\ \hline GCS & & & & & & & \\ Data Links & & & & & & & \\ Air Vehicle & & & & & & & \\ Propulsion & & & & & & & \\ Payload & & & & & & & \\ Control & & & & & & & \\ Autonomy & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: \(\bullet\) indicates that Research will significantly enhance a technology in a class of Unmanned Aerial Systems (UAS), \(\blacklozenge\) indicates that some specific research is required, \(\bigcirc\) indicates that Research will have little real impact. Group 1 has some overlap with micro UAS in needing acceptable payloads that challenge the size of consumer equipment, while not benefiting from manned aircraft ISR technology. Most payload issues are not within the narrow definition of aeronautics. Group 1 shares with micro UAS some of the problems of environmental hazards near the ground. XA systems require substantial research to become practical. Improvement in bearings, actuators, structures and autonomous health monitoring for reliability and efficiency may need to be achieved. This class faces aerodynamic and structural challenges that generally also become control system problems due to the flexibility of the craft, such as the products of the NASA ERAST program [43]. The uncluttered, high altitude environment ensures that the need for advanced autonomy is quite low. UCAV face a number of problems related to the antagonistic environment in which they operate that will inhibit data links and ISR functions and probably place additional reliance on autonomy. Robust control of unusually shaped aircraft remains an active area of scientific research. Although not generally publicized it seems safe to assume that advances in manned fighters and bombers are significant contributors to advances in UCAVs. This research is removed from the mainstream of academic and industry research. This assessment of current UCAV research needs is speculative at best. A further consideration of micro UAS is necessary due to their apparently strong benefit from research. The primary driver of technology must be considered.