Nonbuilding Structures and Nonstructural Components

Single Abstract

335870 - Analysis and Design of Flame Duct

Friday, April 20
3:30 PM - 5:00 PM
Location: 201C

This paper will discuss the field investigation and the analytical methodology developed to validate flame ducts at space rocket launch facilities. To be commercially viable, commercial space programs are using relaunchable spacecraft and existing launch complexes. These launch complexes were originally designed for different space craft with different launch characteristics such as launch pressure and temperature time histories. Essential parts of a launch complex are flame ducts that are used to deflect the rocket's exhaust and debris away from the rocket. While these ducts were often designed and constructed to accommodate a range of rockets, it is desired to use existing flame ducts for newer, larger rockets located closer to the inlet of the flame duct. Under such conditions, it is necessary to perform field as well as analytical investigations to validate the adequacy of the existing flame duct.
These structures are typically constructed of reinforced concrete, and are located below the rocket’s launch pad. During the launch process, the flame duct is subjected to intense heat and pressure with magnitude dependent, among other things, on the size and vertical position of the launched rocket.
Conventionally, flame ducts are designed for steady state gas pressure. Considering the dynamic nature of the rocket exhaust, this approach is very conservative especially for existing flame ducts that are required to be used with larger launch vehicles. Transient gas pressures due to various launch scenarios are investigated using Computational Fluid Dynamics (CFD) simulations.
High-Fidelity, Physics-Based (HFPB) three dimensional finite element models are typically generated for the flame duct. These analytical models are subjected to the transient gas pressures calculated during the CFD simulations, and the structural response of the flame duct is analyzed. Based on structural response, various strengthening strategies are developed followed by a cost benefit analysis to identify the most cost effective strategy.
This paper will discuss the field investigation as well as the analytical methodology developed to validate existing flame ducts. Furthermore, various structural hardening strategies are presented and discussed in details with special focus on constructability and cost/benefit aspects.

Yousef Alostaz




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Bunti Patel

Sr. Manager



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Peter H. Feenstra


Dr. Peter Feenstra is a Manager in Exponent’s Buildings and Structures practice. He specializes in computational solid mechanics and has over twenty years of experience in advanced modeling and analysis projects. The technical disciplines in which he works include linear and non¬linear response of structures, foundations, and soil-structure interaction under static and dynamic loads.

Prior to joining Exponent, Dr. Feenstra was a senior engineer in the Specialty Practices Group of AECOM. Before that, he worked for ten years as an academic researcher at Stanford University, at Delft University of Technology, and at Cornell University. He started his career in the computational mechanics group of TNO Building and Construction Research in the Netherlands where he worked on finite element program development, customer support and training, and consultancy.


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335870 - Analysis and Design of Flame Duct

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