The BLT Prediction Tool ("BLT" signifies "Boundary Layer Transition") is provided as part of the Damage Assessment Team analysis package, which is utilized for analyzing local aerothermodynamics environments of damaged or repaired space-shuttle thermal protection tiles. Such analyses are helpful in deciding whether to repair launch-induced damage before re-entering the terrestrial atmosphere. Given inputs that include re-entry trajectory and attitude parameters, air density, air temperature, and details of each damage or repair site, the BLT Prediction Tool calculates expected times of laminar-to-turbulent transition onset of the boundary-layer flow during re-entry. (These times help to define the proper aerothermodynamic environment to use in subsequent thermal and stress analyses of local structural components.)
The BLT Prediction Tool includes a database of computed boundary-layer parameters that cover a range of nominal re-entry trajectories and uses an interpolation program for estimating local boundary-layer properties during flight along a specific trajectory. Boundary-layer-transition criteria used in the BLT Pre diction Tool were developed from ground-based measurements to account for effects of both protuberances and cavities, and have been calibrated against flight data. Version 1 of this BLT prediction tool was developed in time for the first Return-to-Flight mission STS-114.
This work was done by Scott Berry, Tom Horvath, Ron Merski, Derek Liechty, Frank Greene, Karen Bibb, and Greg Buck of Langley Research Center; Harris Hamilton and Jim Weilmuenster, Contractors with Langley Research Center; Chuck Campbell, Stan Bouslog, Ben Kirk, Garry Bourland, Amy Cassady, and Brian Anderson of Johnson Space Center; Dan Reda and James Reuther of Ames Research Center; Gerry Kinder, Dennis Chao, Jay Hyatt, Maria Barnwell, and K. C. Wang of The Boeing Co.; and Steve Schneider of Purdue University. For more information, contact the Langley Innovative Partnerships office at (757) 864-4015. LAR-17337-1