Modeling RLV Conceptual Designs

It should come as no surprise that I am interested in Reusable Launch Vehicles (RLVs), specifically their design.  Since founding Mach 30, I have come to believe that the key to successfully developing the first true RLV is to follow the example of the Wrights and other successful innovators, and start with much more modest requirements than in the past. But developing improved requirements is only the first step of many.  The next step is to develop and analyze concepts for systems which can meet these requirements.  And, while I do have some ideas for some concepts, there is still the problem of analyzing these concepts.  As a Phoenix Integration employee, and someone with a good deal of experience with their tools, my first tool of choice for approaching this kind of work is ModelCenter.  ModelCenter’s role in this kind of analysis is to bring a variety of specialty tools together and facilitate their interconnection into a system level model.  For any given modeling scenario, the next question is then how to develop the interconnected analyses, and what tools are best used in their development. Unfortunately, I have not built a model of an RLV like this before, so I don’t have a ready answer to this latest question.  But I have been researching RLV modeling and found some options.  The first set of options comes from a webinar conducted by Phoenix Integration in 2010, and the second from Walter Hammond’s Design Methodologies for Space Transportation Systems. In the Phoenix Integration webinar, a SpaceWorks Engineering presenter made the following selections.

  • Geometry – AeroSurface Sizer
  • Aerodynamics – Missile Datcom
  • Propulsion – REDTOP-Lite
  • Cost – Custom Excel Spreadsheet

Hammond recommends a different set of tools, covering a wider set of disciplines.

  • Geometry – Solid Modeling Aerospace Research Tool (SMART) Note, this no longer appears in many places online.  Vehicle Sketch Pad (VSP) may be a suitable replacement.
  • Aerodynamics – Aerodynamic Preliminary Analysis System (APAS) [google docs view] Hammond notes APAS does not perform well in the transonic regime, and that some users use Airplane and Missile Datcom instead.
  • Trajectory – Program to Optimize Simulated Trajectories (POST)
  • Weights and Sizing – CONSIZ (a NASA Langley code) Hammond notes there is usually a convergence loop which iteratively runs the Geometry, Aerodynamics, Trajectory, and Weights and Sizing analyses to reach a properly scaled design for the concept being modeled
  • Heating – MINIVER
  • Structural Analysis – conducted by mapping Aerodynamic loads onto Finite Element Model(s) of the vehicle (based on the Geometry) to calculate stresses, the results of which can be sent to EZDESIT to determine the required thickness for the skin panels
  • Operations – Reliability, Maintainability Analysis Tool (RMAT), developed at the University of Dayton
  • Full Mission Simulation – Simulated Language for Alternative Modeling (SLAM)

It is interesting to note the similarities and differences between the two lists.  Both lists include geometry and aerodynamic analyses.  However, only the first list includes a propulsion analysis, and the second list includes a number of additional analyses such as heating, structures, and operations.  The commonality in the approaches appears to be generating geometry, determining the vehicle’s performance, and converging the size of the vehicle to bring the performance up to the requirements. It should also be noted that many of the tools across the lists did not turn up on internet searches, and of those that did, not all of them have dedicated public web sites.  This lack of public data about the tools makes it difficult for Mach 30 to utilize the tools in analyses.  Another presentation by SpaceWorks Engineering includes a list of alternative tools by analysis type.  I plan to review this presentation to see if there are tools which have more publicly available supporting documentation.  If there are not suitable tools, another option would be to develop new tools based on published materials, such as this book that presents a unified model for atmospheric and space flight dynamics. If you have experience with any of these tools or suggestions for alternatives, please leave a comment below.   And please leave a comment if you would like to help develop any of the underlying analyses. ad astra per civitas

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