I am trying to design a hyper sonic aircraft in line with X-15 for my Aircraft design project. This requires me to figure out the preferred airfoil shape for the wing.
At hypersonic speed the local drag grows with the inclination of the local surface against the free stream. Thus, the best shape is a thin wedge. Drag will scale with the cube of the thickness ratio of the wedge.
Depending on the maximum tolerable heat load, you should choose a pointed leading edge (highest heat load, smallest drag) or a blunt leading edge, where the separated shock will reduce local heat loads, albeit at the price of much higher drag.
Ideally, past its maximum thickness the airfoil tapers down towards a thin trailing edge, and again a wedge shape will cause the least amount of drag.
In the picture below (source) you can barely see the tip airfoil of the X-15:
It used a simple, blunt wedge at the vertical tails because the vacuum at the rear face provided additional directional stability. However, for lowest drag, a double wedge of the smallest thickness possible should be used.