XCOR Lynx: Aerodynamics–Supersonic wind tunnel tests

LITT TUNNEL

In this image, XCOR engineer Brandon Litt makes final preparations to a Lynx supersonic wind tunnel model before performing a test at the storied NASA Marshall tri-sonic wind tunnel in Huntsville, Alabama.

NASA TUNNEL

Above, a NASA Marshall spaceflight engineer tests a similarly sized supersonic wind tunnel model of the Space Shuttle in the same facility during the early years of the Shuttle program. The results of the Shuttle tunnel tests were critical to the go-forward decision to build and fly the Space Shuttle.

We believe that test pilots and customers alike require confidence that the spacecraft they fly on has been evaluated and tested extensively prior to flight. And in this day and age, many rely on computer simulation to be sure that their aircraft can perform at the level required.

XCOR used Computational Fluid Dynamics (CFD) and other software analysis tools to design the shape of the Lynx aeroshell. However, things really accelerated when we were able to perform a series of seven subsonic and supersonic wind tunnel test campaigns at United States Air Force (USAF) and NASA labs.

Typically, the faster the tunnel, the smaller the available space. Supersonic wind tunnel models are traditionally smaller than their subsonic counterparts due to the available space in supersonic tunnel test sections. The models must not only fit, but have room to change pitch and yaw inside the tunnel without approaching the side walls of the tunnel. If the model is too close to the walls, edge effects from the walls can be picked up in the data, and ruin the test.

Because supersonic wind tunnels are so small, Lynx models themselves must be highly precise to adequately simulate the full scale spacecraft. The models have many pieces that are interchangeable to test different configurations of the vehicle. For example, a model may have 5-10 different nose shapes, 5-10 different permutations of wing aileron settings, and so on. Because of this, the models can become quite expensive, sometimes approaching several hundred thousand dollars.

Because the actual Lynx is so much smaller in real life than the Space Shuttle attached to the solid rocket boosters and center fuel tank, the Lynx model shown above is actually much larger (almost 3-4 times larger) in scale than the Space Shuttle model.

Tomorrow we answer some of the week’s questions and let you know where you can find XCOR on the road in the near future. In particular, we’ll have some updates for future appearances of XCOR team members and the Lynx full scale model.