The Boundary Layer Transition (BOLT) Flight Experiment

Abstract

The Boundary Layer Transition (BOLT) flight experiment, a unique collaboration spanning academia, government, and industry, sought to obtain flight data on a critical phenomenon affecting hypersonic vehicle design. The project aimed to further understanding of the physics of boundary-layer laminar-turbulent transition on a complex geometry, a process that can significantly increase heating and can affect hypersonic vehicle drag, controllability, and engine performance. The Johns Hopkins University Applied Physics Laboratory (APL), the project’s principal investigator, led a large team of external collaborators to design a sounding rocket flight experiment over an 18-month period, while conducting an extensive campaign of wind-tunnel experiments and computational simulations to predict the flow physics on the BOLT geometry. The final flight experiment was built and instrumented at APL using Laboratory expertise in designing and prototyping hardware for extreme environments. The BOLT experiment was delivered to the US Air Force for the flight experiment, designed to gather critical validation data on BOLT’s boundary-layer transition from over 340 sensors in the hypersonic flight regime. Although the flight test ultimately did not achieve the desired experimental conditions, the BOLT research resulted in new experimental databases, new computational tool development for complicated hypersonic flows, and significant new workforce development through the inclusion of students in the program. APL’s efforts to develop BOLT led to a follow-on flight experiment focused on turbulence (BOLT2: The Holden Mission), which flew successfully in March 2022.