Sydney researcher 3D prints hypersonic aircraft models for low-speed wind tunnel testing

Tamas Bykerk, a graduate student at the University of Sydney in Australia, has used 3D printing technology to create hypersonic aircraft models for low-speed wind tunnel testing. 3D printers have greatly reduced the time it takes to create a working prototype. It also enable him to efficiently explore multiple options by printing various iterations of a part to test and gather feedback on.

Bykerk is pursuing a Ph.D. in Aerospace Engineering, supervised by Dr. Dries Verstraete. Both of them are part of the Hexafly-International project where they partner with the European Space Agency (ESA) and Italian Aerospace Research Centre (CIRA) to evaluate the feasibility of commercial hypersonic air travel.

In aerodynamics, hypersonic speed is defined as the point where individual physical changes in the airflow (like dissociation and ionization) occur. A hypersonic speed has generally referred to speeds of Mach 5 and above. For decades, atmospheric escape and return vehicles such as NASA’s space shuttles and rocket-propelled research planes have flown at such speeds for short durations. However, commercial hypersonic airliners which require sustained hypersonic flight are still in the concept phase.

“Currently, the overwhelming bulk of research focuses on the high-speed design point – mainly the aero-structural issues which accompany airframe heating. My research looks at whether these aircraft can take off and land safely,” says Bykerk. “The main goal is to evaluate performance and stability during those two most critical phases of the flight.”

All fixed-wing aircraft designs must balance two opposing goals – optimal efficiency at cruising speed versus stable, controllable flight at takeoff and landing speed. The faster the desired cruising speed, the more pronounced the compromise becomes. In layman’s terms, super-fast airplanes are not built to fly slowly.

When a plane takes off, and while it is attempting to land, it approaches what is known to pilots as minimum controllable airspeed – the point at which flying any slower will discontinue the ability to maintain stable flight. It is at this speed where flying becomes most dangerous because a reduction in airspeed will cause the aircraft to stall, pitching into a dive or spin to regain airflow over its wings. There is no time to recover when it happens close to the ground.

Barely-existent aerodynamic issues at higher altitudes and velocities become significant risk factors during slower flight near the earth. A crosswind can require the plane to be flown at an awkward angle on its vertical axis to maintain its flight path, altering the way air flows over its wings and control surfaces. Bykerk is tasked with studying these slow-flight considerations in aircraft designs capable of flying at multiple times the speed of sound.

The Faculty of Engineering & Information Technologies at University of Sydney has 16 Tiertime 3D printers, four of which are in its fab lab, housed within the School of Aerospace, Mechanical and Mechatronic Engineering. Bykerk uses these 3D printers in the construction of hypersonic aircraft models for testing in a low speed wind tunnel. Larger models are 3D printed in ABS parts, then assembled and post-processed to ensure continuity between the original design and the model. Techniques include sanding, gap-filling, sanding again, resin-coating and painting.

The final product is placed in a wind tunnel where crucial data can be obtained.