Secondary Side Considerations for Boundary Layer Transition Flight Experiment

The Boundary Layer Transition (BOLT) Flight Experiment is to launch soon on a sounding rocket to obtain hypersonic data on a complex geometry with swept leading edges and concave surfaces. BOLT was designed to provide two distinct experimental surfaces on opposite sides of the vehicle. One side of BOLT, referred to as the primary side experiment, was specifically dedicated to boundary-layer transition at hypersonic conditions in the absence of intentionally added surface roughness. The other side, the secondary side experiment, was selected to investigate roughness effects, in the form of rearward-facing steps. Step effects are an important consideration for both sides, as joints near the nose were required to alleviate aerothermodynamic heating. The secondary side joints were made larger than the primary side to provide additional insight into the impact of rearward-facing steps during flight. The secondary side experiment is the focus of the present Paper, which provides details into design decisions made to finalize the geometry and instrumentation for flight.