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Activity title

Integration of Propulsion, Power, and Thermal Subsystem Models into Air Vehicle Conceptual Design

Activity Reference



Applied Vehicle Technology

Security Classification




Activity type


Start date


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Air Vehicle, Conceptual Design, IPPTS, Multidisciplinary, Power, Propulsion, Subsystems, Thermal


Current common practice in air vehicle design follows the path of largely independent propulsion, power and thermal management subsystem design. Furthermore, the power and thermal management subsystems are not designed until much later in the design process after the outer mold line (OML) has already been fixed. When applied to new air vehicles with embedded propulsion subsystems and demanding power and thermal requirements the traditional design process often fails to return a closed solution. This reality leads to insufficient power or thermal management capacity and results in unwanted forced features on the OML or restrictions on the operational capabilities. The cost to deal with these problems late in the design process is unacceptably expensive. To minimize these difficulties in future air vehicle design, the propulsion, power and thermal management subsystems, and other vehicle systems must all be appropriately coupled together via their interacting physics so as to allow for simultaneous design. IPPTS issues for current and future military air vehicles is a concern for all NATO nations that own and operate these assets. Power requirements for modern and future mission systems’ capabilities, which necessarily directly affect propulsion and thermal requirements, are only growing. The best time in the acquisition timeline to consider these integration challenges is during the earliest stages of conceptual design since the bulk of the life cycle costs of engineered vehicle systems are set during this early design stage.


Bringing IPPTS concerns earlier into the design process is a difficult but necessary challenge for NATO for several reasons. Firstly, the integrated nature of this design problem calls for MDO during the early conceptual design phase. Secondly, the appropriate level of model fidelity must match the physics of the design problem. Thirdly, the short timelines and budget levels normally granted to the earliest design phases has little chance of being lengthened or augmented to accommodate the increase in disciplines needed for IPPTS analysis. These additional disciplines would have to be considered during the conceptual design phase and modelled at the appropriate fidelity level. These three realities point to a need to understand how to accomplish more, early in the design process, without relaxing historical time and cost constraints. If following a traditional design philosophy, the IPPTS issues will not be properly addressed. A new vehicle system level conceptual design process would need to be established to enable a fully integrated vehicle design including the propulsion and all major power and thermal management subsystems. This new process would allow the air vehicle to be modified to concurrently satisfy all the individual and coupled requirements of the propulsion, power and thermal management subsystems. This will produce the following benefits: 1) Improved system-level decision making with less uncertainty concerning salient system capabilities and technology assessment. 2) Reduced number of late defects within the system due to understanding of complex multidisciplinary physical couplings previously undiscovered until detailed design or flight testing in the traditional design process. 3) Enlarged design space to enable novel system-level concepts and otherwise unobtainable capability by leveraging the discipline couplings. This proposed AVT activity will work to support this change in the conceptual design phase by bringing together the collective knowledge and experience of the participating nations and developing a NATO best practice guide for incorporating IPPTS models as part of the conceptual design process. Note that this activity will not transfer intellectual property across organizations or produce a how-to guide. The best practice guide will instead review the different approaches/methods for IPPTS modelling, enable the development of an industry-wide standard for IPPTS modelling, evaluate computational technologies in relation to IPPTS modelling, and characterise available tools to perform IPPTS modelling among others. The best practice guide product will support the efforts of any organization under the NATO umbrella to work this issue to their level of technical proficiency. Thus, the member nations will be encouraged to participate without fear of losing their competitive edge, and all will benefit fairly from the best practice guide. The guide will help accelerate NATO nations’ mastery of this important technology area, which supports our warfighters.


The best practice guide will include many different scientific topics and will capture the state-of-the-art by offering guidance on how to use these topics in IPPTS work. Example topics are listed below. Proper model fidelity level decision process Architecture selection Desired experimental hardware for testing Component size, weight, and power Transient analyses Distributed geographic computing Nonlinear programming Model requirements definition/elaboration approaches Global optimization High Performance Computing (HPC) strategies for MDO with IPPTS

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