4 results found
Levis E, Pleho F, Hedges J, 2020, Viability of joined flight for small unmanned aerial vehicles, The Aeronautical Journal, Vol: 124, Pages: 297-322, ISSN: 0001-9240
The range of small, electrically powered UAVs is still limited by the mass specific energy of batteries. This paper investigates the idea that, in cases where multiple aircraft must transit to the same location, savings in mass or an extension of achievable range are possible when they join wingtip-to-wingtip. The viability of joined flight is investigated by quantifying the relative magnitude of savings resulting from increased aerodynamic efficiency and that of penalties due to the increased structural and component weights. Through a parametric analysis the level of savings achievable is found to be greatly dependent on the proportion of the flight spent in a joined configuration and aircraft design parameters such as wing loading, aspect ratio and the added weight of the joining mechanism. A custom, multidisciplinary UAV sizing algorithm is presented and utilised to design several sample aircraft, featuring two different joining mechanism architectures. The results verify the findings of the parametric study and indicate that mass savings are possible only for moderate to low aspect ratios, with semi-permanent magnetic joining mechanism performing better than rigid structural ones, even when the joined fight segment accounts for only 30% of the total airborne time.
England G, Levis E, 2017, An Investigation into All Electric and Hybrid Aircraft, Aerospace Europe 6th CEAS Conference, Publisher: CEAS
Braun M, Bruce P, Levis E, 2017, Strategies to utilize advanced heat shield technology for high-payload mars atmospheric entry missions, Acta Astronautica, Vol: 136, Pages: 22-33, ISSN: 0094-5765
Present Entry, Descent and Landing (EDL) technology for interplanetary missions does not have the capabilities to meet the demanding requirements that come with future missions. A popular target for such missions is Mars and today efforts are made to send manned as well as sophisticated robotic probes to the Martian surface. Because present EDL technology has reached its limits, fundamentally new approaches are needed to significantly extend capabilities. Systematic evaluation of novel EDL technologies and optimization of EDL strategies are crucial needs for conceptual design. A computational framework will be presented tailored to enable systematic EDL analysis with special regards to novel EDL technology and event strategies. The benefits of flexible heat shield concepts that come with liberties in the choice of the ballistic coefficient will be shown in comparison with solid shield alternatives for payload classes of 2, 25 and 40 tonnes to show potential for manned and robotic missions. Furthermore, benefits of the new methodology for novel EDL event strategies are presented and discussed. The introduced methodology will help designers exploit new directions for conceptual design regarding EDL systems in terms of entry mass optimization and mission capabilities.
Levis E, Serghides VC, 2014, The Potential of Seaplanes as Future Large Airliners, Advanced Aero Concepts, Design and Operations, Publisher: Royal Aeronautical Society, Pages: 1-12
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