## 4 Discussion
This is caused by the fact that higher degrees of freedom allow the control mechanism, whether discrete or continuous, to approach the optimal solution. The dependence of the performance of an aircraft on drag is complex. Therefore, a blanket statement about how a reduction in drag would affect the overall performance of aircraft is difficult to make. However, it is insightful that a 5% reduction in induced drag can roughly be correlated with a 2.5% reduction in thrust, if induced drag was originally 50% of the total drag. This could translate to about a 2.5% reduction in fuel required, which would lower the weight of the aircraft and reciprocally result in further drag reduction. Continuous control surfaces, in general, have greater aerodynamic efficiency capabilities than discrete control surfaces. However, the ideal aerodynamic benefits for induced drag shown in this study are small. It should be noted that lifting-line theory used here to determine the ideal aerodynamics does not take into account any flow spillage that may occur across the gap created by two adjacent discrete control surfaces that have different deflections. Accounting for this would likely cause the discrete control surfaces to have more drag than shown here. Future work could include comparing efficiencies of spanwise discrete and continuous control surfaces while taking into account parasitic drag and the discrete control surface flow spillage effect. As a final note, the present manuscript includes two main contributions. The first is simply a method for comparing the effectiveness of discrete control surfaces to continuous. The method followed here could be repeated using wind-tunnel experiments, computational fluid dynamics, or higher-fidelity aerodynamic prediction methods. The second contribution is the presentation of results of this method based on lifting-line theory. The limitations of lifting-line theory are well documented in the literature. As a reminder, the results shown here neglect influence of viscosity, and should not be expected to be accurate for wings with aspect ratios less than about 4. Additionally, compressibility effects have been neglected. Nevertheless, the trends obtained from these results are insightful and can guide the discussion and development of future morphing-wing controls. Conceptualization, Z.S.M. and D.F.H. ; methodology, Z.S.M. and D.F.H. ; software, Z.S.M. ; validation, Z.S.M. ; formal analysis, Z.S.M. ; investigation, Z.S.M. ; resources, D.F.H. ; data curation, Z.S.M. ; writing--original draft preparation, Z.S.M. ; writing--review and editing, Z.S.M. and D.F.H. ; visualization, Z.S.M. ; supervision, D.F.H. and J.J.J. ; project administration, D.F.H. and J.J.J. ; funding acquisition, D.F.H. and J.J.J. All authors have read and agreed to the published version of the manuscript. This work was funded by the Air Force Office of Scientific Research (AFOSR) Lab Task 17 RQCOR394 with Dr. [PERSON] as the program manager and by the U.S. Office of Naval Research Sea-Based Aviation program (Grant No. N00014-18-1-2502) with [PERSON] as the program officer. This paper has been cleared for public release, Case Number: 88 ABW-2020-2554. The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author. The contents of this article were originally presented as part of paper 2020-2008 at the AIAA SciTech 2020 Forum, Orlando, Florida, 6-10 January 2020 [37]. The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.