Boundary Layer Transition, Detailed Test Objective 854 (BLT) - 12.06.17

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
The Boundary Layer Transition (BLT) experiment involves the use of ten modified tiles, equipped with thermocouples (indicate a temperature change based on voltage between a junction of two different metals), placed on the bottom of Space Shuttle Discovery’s left wing. One tile is also equipped with a protuberance (specially modified speed bump) to study the characteristics of how the airflow is tripped from laminar (smooth) to turbulent (rough) during re-entry. This experiment will improve understanding of the parameters associated with re-entering the atmosphere and including the significant heat increase caused by turbulent boundary layer flow.
Science Results for Everyone
Space vehicles feel the heat. When airflow changes from smooth to turbulent along the surface of a vessel re-entering Earth’s atmosphere, temperatures rise several 100 degrees. Using tiles with built-in thermometers and one with a small speed bump on the bottom of Space Shuttle Discovery, this experiment measured those airflow and temperature changes during re-entry in order to better understand the phenomenon. Investigators obtained temperature data near Mach 16 (nearly 12,000 mph) and after Mach 16 downstream of the craft’s port landing gear door. These data will support modeling and design of next-generation spacecraft.

The following content was provided by Charles H. Campbell, Gerald Kinder, and is maintained in a database by the ISS Program Science Office.
Experiment Details


Principal Investigator(s)
Charles H. Campbell, Johnson Space Center, Houston, TX, United States
Gerald Kinder, The Boeing Company, Huntington Beach, CA, United States

Karen Berger, Langley Research Center, Hampton, VA, United States

Langley Research Center, Hampton, VA, United States
Jacobs Engineering, Houston, TX, United States
United Space Alliance, Cape Canaveral, FL, United States
NASA Kennedy Space Center, Cape Canaveral, FL, United States
NASA Ames Research Center, Moffett Field, CA, United States
Boeing, Huntington Beach, CA, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)

Research Benefits
Information Pending

ISS Expedition Duration
October 2008 - October 2009

Expeditions Assigned

Previous Missions
The Boundary Layer Transition (BLT) experiment was first introduced on ISS Expedition 18.

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Experiment Description

Research Overview

  • The goals of the Boundary Layer Transition Flight (BLT) focus on developing a better understanding of entry environments associated with boundary layer transition and turbulent heating. Boundary layer transition occurs when the smooth, laminar airflow changes to a disturbed, turbulent flow that causes downstream surface temperatures to climb several hundred degrees Fahrenheit. This change from a smooth, laminar boundary layer to a turbulent boundary layer has significant implications for vehicle design, entry performance capability and aerodynamics, both of the Orbiter and other potential manned entry vehicles.

  • The data gathered from this experiment will be utilized to support analytical computer modeling and design efforts for the Space Shuttle and NASA’s next generation spacecraft. Research activities that are motivated in part by this flight experiment are also being sponsored by the Aeronautics Research Mission Directorate Fundamental Aeronautics Program - Hypersonics Project, and by the Air Force Office of Scientific Research.

  • Collaborative efforts by the NASA Hypersonic Thermodynamic IR Measurement (HYTHIRM) Project are also being performed. These efforts have successfully acquired hypersonic infra-red images of the Orbiter during the STS-119, STS-125 and STS-128 entries.

Two Shuttle missions have included the BLT implementation. During STS-119, a 0.25 inch (6.4 mm) speed bump was installed on Discovery. During STS-128, a 0.35 inch (9.6 mm) speed bump was installed on Discovery. Flight measurements indicated that boundary layer transition occurred near Mach 15 and 17.5 during STS-119 and STS-128, respectively. Downstream turbulent temperature increases of several hundred degrees Fahrenheit were recorded during the turbulent heating duration of the entry. As part of efforts to provide technical documentation of results and studies related to the collaborative NASA and Air Force efforts on boundary layer transition, twenty three technical publications were presented at the January 2010 AIAA Aerospace Sciences Meeting.

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Space Applications
The data gathered from the BLT experiment will be utilized to support analytical computer modeling and design efforts for the Space Shuttle and NASA’s next generation spacecraft.

Earth Applications
The BLT investigation provides scientists and engineers with the incredible opportunity to demonstrate how NASA is working to understand spaceflight better and an opportunity to successfully apply what has been learned to improve space vehicles.

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Operational Requirements and Protocols
The Boundary Layer Transition DTO will involve the use of ‘integrated TPS and MADS instrumentation (designed) to fly with a fixed protuberance tile with a height of 0.25” to initiate BLT.
Ten modified tiles are part of the flight experiment, including a tile with a raised surface known as the protuberance tile. All ten tiles have a thermocouple built in, which acts like a thermometer. The temperature data during Orbiter entry is collected by these ten thermocouples. One of the tiles with a thermocouple is mounted in front of the protuberance tile to measure the normal temperature in the regular airflow.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

The STS-119 Boundary Layer Transition (BLT) Flight Experiment was successful in obtaining BLT onset data near Mach 16 and turbulent heating data after Mach 16 with a 0.25" tile protuberance downstream of the port landing gear door. Flight hardware performance and thermocouple data was excellent and no anomalies were identified. Initial flight data reviews indicated high confidence for implementing a larger protuberance height on STS-128.

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Related Websites
NASA EDGE HYTHIRM/Cast Glance Overview --NE@Shuttle IR Imaging
NASA - STS-119 BLT test a success, gains a greater understanding of reentry
Spaceflight Now -- Tripping the boundary layer: shuttle experiment for entry

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image Image of BLT in processing. Image courtesy of NASA.
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image STS-119 Post-flight image of BLT. Image courtesy of NASA.
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image Close-up image of BLT. Image courtesy of NASA.
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