• Mr. Eric Gustafson
  • Structural Design and Analysis, Inc.
  • Holden Auditorium (Room 112)
  • 4:00 p.m.
  • Faculty Host: Dr. Robert Canfield

The heatshield carrier is a vital component of the Orion Multipurpose Crew Vehicle (MPCV) and is instrumental in protecting both the vehicle and its crew. The heatshield carrier must provide a sturdy foundation for the outer ablative layer, resist the effects of atmospheric reentry, and bear the impact of a water landing without becoming an excessive mass burden on the Orion spacecraft. Because of this, Structures.Aero worked with the NASA National Engineering Safety Center (NESC) to design an alternate heat shield with the goal of a 25% reduction in system mass over the baseline Titanium stringer-composite skin design. This would require an innovative strategy to develop a design and analysis process that utilized multiple simulation codes to deliver a final lightweight design.

Traditional modeling practices use “loads” and “stress” finite element models (FEMs), with the former suitable for initial sizing and the latter serving to verify prior conclusions about model behavior. Analogous to the standard two-model system, two independent FEM types were developed and maintained for this project. The first FEM type used in preliminary sizing and trade studies utilized “smeared” properties that simulated the strengths and stiffnesses of open panels supported around their perimeter. These models were simpler, faster to iterate, and permitted the generation of a multitude of trade concepts in Hypersizer that could save mass. The second FEM type was a detailed representation of geometric features of the chosen concept. Referred to as the “explicit” model, it enabled final detailed analysis of a chosen concept’s structural features.

Trades were evaluated and a Titanium orthogrid was ultimately down-selected. A practical orthogrid sizing process was developed that first used linear analysis on the smeared FEM for the rough design, then allowed for localized yielding through nonlinear assessments of stiffness, strength, and stability in the explicit FEM. Iterating the design with LS-DYNA took advantage of the inherent damage tolerance of the orthogrid concept by permitting loads to redistribute in a non-detrimental manner. This approach effectively used material plasticity to save mass, but was initially challenging to incorporate in the design cycle due to the arduous nature of verifying congruency between translated models.

The design and analysis approach was validated by drop-testing a 20” diameter subscale titanium orthogrid test article. This test article was first designed and modeled with the developed approach for purposes of validation. Test predictions were also part of the verification process to corroborate the results of Nastran’s implicit nonlinear transient solutions and explicit solutions from LS-DYNA. Dynamic drop tests were completed and compared to the converged predictions. The methods were validated by the dynamic tests. A lighter-mass structural concept was uncovered by a trade analysis which led to a new set of design and analysis procedures undertaken on the down-selected design. The new process for design and analysis of the orthogrid structure smoothed the workflow between numerous analysis codes, and the streamlined design cycle netted a nearly 50% mass reduction on the baseline design. This far exceeded the original goals of the project by delivering a significant potential mass savings to the Orion program.


Mr. Gustafson is an aerospace structural engineer for Structural Design and Analysis, Inc. He holds both B.S. and M.S. degrees in mechanical engineering from Virginia Tech. He has accrued years of experience on projects working the primary structure of various small, medium, and large UAVs in addition to the current NASA Orion spacecraft program. Eric's past experience has spanned design, analysis, and manufacturing. His structural focus has been in finite element analysis and applications of composites in primary structure. Eric is also the author of the new book, "Learning Femap".