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Flight in the hypersonic regime, approximately five times the speed of sound, has been of interest to militaries and commercial aviation enthusiasts for many years. Hypersonic airbreathing vehicles are desired for efficient long range cruise missiles, global reconnaissance, and access to space as they promise higher efficiency than current technology. Although there have been a few recent successes with government funded hypersonic programs, many technology gaps still exist and must be investigated before further progress can be accomplished for hypersonic vehicles. One of the limiting factors in the robustness of a hypersonic airbreathing engine involves starting inlets. In order to achieve sufficient combustion during flight, a vehicle must have a started inlet, an inlet in which there is no strong bow shock, no flow separation, and flow is not significantly disrupted by turbulent forces. There have been many techniques implemented to start an inlet such as retractable doors, variable inlet geometries, and mass extraction through perforations. Although the aforementioned techniques are all viable solutions, permanent perforations for excess air removal are arguably most beneficial due to ease in manufacturing and weight reduction of the overall inlet. This project analyzes the Molder Theory, a technique for developing bleed holes for excess air removal using necessary spillage area per unit length and the Kantrowitz Limit for hole spacing. To test the theory Computation Fluid Dynamics was completed on a simple axisymmetric Busemann inlet with various bleed hole configurations. Hypersonic wind tunnel tests are to be completed with a GoHypersonic Inc. axisymmetric Busemann scramjet inlet using the Kantrowitz Limit and Molder Theory for bleed hole configuration design. Experimental results will be obtained for validation of the Molder Theory for perforation location and sizing.

Publication Date


Project Designation

Honors Thesis

Primary Advisor

Aaron Altman

Primary Advisor's Department

Mechanical and Aerospace Engineering


Stander Symposium poster

Bleed Hole Location, Sizing, and Configuration for Use in Hypersonic Inlets