Critical Contributions to the Space Shuttle Return-to-Flight Effort Made by Glenn’s Ballistic Impact Team

External tank structural impact tests being conducted in the Ballistic Impact Laboratory.
Long description of figure 1.

Following the Space Shuttle Columbia accident investigation, NASA initiated the Return to Flight program, which established numerous technical issues requiring resolution prior to the launch of STS-114. NASA Glenn Research Center’s Ballistic Impact Team was given the task of conducting numerous critical ballistic impact testing and analysis programs to investigate and quantify the physics of debris impact on the reinforced carbon/carbon wing leading edges, nose caps, orbiter windows, and external tank structures. The test programs ranged from fundamental material characterization tests to full-scale tests of the orbiter wing leading edge and nose cap, which identified critical impact damage threats to various shuttle components. Glenn researchers examined damage threats from potential impactors, including shuttle thermal-protection foams and ablators as well as ice formed on the shuttle’s external tank. The analysis effort at Glenn encompassed the development of high-fidelity material models for implementation into the explicit finite-element impact-analysis code LS DYNA. The analysis method is now being used to analyze impact events on the shuttle system.

Glenn’s Ballistic Impact Team addressed six elements that were critical to the success of the Return to Flight program:

1. Extensive impact testing and characterization of six shuttle thermal-protection debris materials as
2. well as ice (Glenn’s fatigue laboratory provided static materials testing for this effort as needed.)
External tank foam and booster separation motor aluminum-oxide particle debris impact testing on full-scale orbiter windows
3. Ice and foam impact testing on the external tank structure to assess resulting secondary debris threats and potential degradation of the external tank thermal-protection system
4. Over 100 impact tests on flat reinforced carbon/carbon panels to establish critical impact damage thresholds for the material as well as to validate material models developed for LS DYNA
5. Material model development and support of production analysis runs for the Shuttle Program Impact Analysis Team
6. Analysis and testing support at Southwest Research Institute for full-scale tests of the wing leading edge and nose cap

High-speed digital photography captures the behavior of external tank foam undergoing an impact event.
Long description of figure 2.

Each element was successfully completed on time, leading to the successful launch of STS-114 in July 2005. As a result of Glenn’s testing, the design of the orbiter windows was changed, the external tank was cleared as safe to fly, and a previously unavailable physics-based impact analysis capability was established for the shuttle program. As a consequence of Glenn Ballistic Impact Team contributions, mission safety for future shuttle operations increased dramatically.

Material models developed by Glenn’s Ballistic Impact Team were implemented into the LS DYNA impact analysis code and used to predict impact damage for future shuttle missions.
Long description of figure 3.

Bibliography

Melis, Matthew, et al.: A Summary of the Space Shuttle Columbia Tragedy and the Use of LS-DYNA in the Accident Investigation and Return to Flight Efforts. Prepared for the 8th International LS-DYNA Users Conference, Dearborn, MI, 2004.

Melis, M.E., et al.: A Summary of the NASA Glenn Ballistic Impact Lab Contributions to the Columbia Accident Investigation. 2005 Proceedings of the Annual Reliability and Maintainability Symposium, Alexandria, VA, 2005, pp. 284-290.

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Materials and Structures

Last updated: October 10, 2006

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