Assessing Damage Effects at Reentry
NASA Langley is using hypersonic wind tunnels in combination with advanced state-of-the-art computational fluid dynamics codes to assess the effects of damage to the Shuttle's TPS. The TPS is designed to protect the vehicle from the extremely high temperatures encountered during reentry into the Earth's atmosphere.
Image above: A bit of precisely sized and shaped tape is placed on the surface of a wind tunnel model for studies of aerodynamic heating during Shuttle reentry, simulating the effects of an on-orbit "plug" repair. Credit: NASA
Studying the effects of TPS damage includes assessing the localized heating environment directly around the damage site and determining the impact the local damage will have on the global heating environment over the Shuttle's entire TPS.
Even if a damage site produces a localized heating environment that is within the TPS design limitations, the site may still disturb the airflow passing over it to the point that it results in elevated heating levels over a large portion of the vehicle surface downstream of the damage site.
Researchers are developing a database to evaluate possible changes in the shape of the Shuttle surface due to TPS damage and their effects on re-entry heating the vehicle will encounter. This database, developed through extensive wind tunnel testing and computational analyses, includes a close look at both vehicle surface cavities and surface bumps. It will be instrumental in helping to determine if TPS damage sustained during ascent or while in orbit requires repair prior to the Shuttle returning to Earth.
If a decision is made to repair, the database will also be used to determine what impact this has on the airflow characteristics and heating during reentry.