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Activity title

Development of a validation model of a stealth UCAV

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Sensors & Electronics Technology

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design, radar absorbing coatings and structures, RCS prediction, SET, stealth


In the past, the task group SET-138 on “Electromagnetic scattering analysis of jet engine inlets for aircraft NCTI purposes”, was formed with participating nations DEU, ESP, FRA, GBR, GRC (chair), NLD and SWE. The members have performed simulation exercises for realistic inlet cavities (both military and civilian) as one of the important contributors to the aircraft’s signature. The group worked closely with SET-112 which developed NCTI for fighter aircraft. Although the cooperation was fruitful, the computational demands of rigorous methods make it difficult to obtain a comprehensive dataset for NCTI purposes of fighter aircraft. Also, the simulations were restricted to perfectly reflective aircraft. Recognising the need for the simulation of radar absorbing coatings or materials, a new task group was formed: SET-200 “Electromagnetic scattering prediction of small complex aerial platforms for NCTI purposes” with participating nations DEU, ESP (chair), FRA, ITA, NLD and SWE. Given the smaller size of UAV’s, in principle simulations of the complete aircraft are possible. The task group worked closely together with SET-180 (the successor of SET-112), which considered (and measured) various UAV’s. The objective of SET-200 was to model and simulate the same UAV’s, but it quickly turned out that this was complicated by the lack of 1) the geometry description of the aircraft (for transparent object the internal geometry is also required); 2) the electromagnetic properties of the materials in the aircraft. The group succeeded in obtaining this information for one UAV, the SCRAB-II, but only in the last year of the group. Meanwhile, a generic on-paper-only UAV was considered by the group, which allowed important cross-comparison between the different methods applied by the group. As no physical counterpart exists for this UAV, the much-needed validation for transparent and/or stealth objects could not be performed. The group finished its activities in December 2016 and has just released its final report, where more detailed information about this work can be found. The group performed successful validation for PEC scatterers and successful cross-comparison for stealth geometries (including RAM coatings), but the lack of validation of the computational methods for the latter reduces their relevance. Parallel to the developments described above, the AVT panel has installed the task group AVT-251, which evaluates design tools for the design of an agile UCAV, taking into account different disciplines such as aerodynamics, structural dynamics, and flight control. Although the group recognizes the need for also considering signatures, the group misses expertise in the electromagnetic design of stealth aircraft. Bearing in mind the aforementioned discussion, the formation of a new STO task group is proposed herein, of which the main purpose will be to continue the already successful work of SET-200 (and predecessors), closely cooperating with AVT-251 and SET-245 (successor of SET-180). Joining efforts with AVT-251 will allow the new task group to apply their methods for the stealth design of the UCAV and at the same time develop a validation model for their methods. The major objectives of the new group will be summarized below.


The main objective of the group is to develop and manufacture a validation model of a stealth UCAV. The model will be based on the UCAV considered in AVT-251 which is designed for a specific mission. The development will be supported by radar signature predictions and threat analysis of the mission. The shape of the UCAV will be fixed by AVT-251, so the stealth design will focus on materials. The aircraft will mostly consist of PEC surfaces, but, to reduce the radar signature, hot spots such as engine inlets, wing edges, control surfaces and cavity edges must be treated with either radar-absorbing coatings or materials. There exist various methodologies to model such aircraft, but the methodologies have not been validated for complex platforms.


The specific topics are presented below: 1. Support AVT-251 in the design of the UCAV from the viewpoint of stealth technology. 2. Determination of design constraints on the radar signature of the UCAV. 3. Development of CAD models for the UCAV. 4. Simulations to determine the hot spots on the UCAV. 5. Assess different treatments (with realistic coatings and materials) of the hot spots with prediction tools. 6. Optimization of the already existing mathematical methods and / or development of new ones. 7. Continuation of the SET-200 activities on the SCRAB-II (including collaboration with SET-245) and the Generic UAV. 8. Design and manufacture of an RCS validation model based on the UCAV design.

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