Heat wall

SR-71 , use of titanium to cope with heat generation

In aircraft construction , the term the heat wall ( English heat barrier ) for the technical problems that occur due to the strong heating of the aircraft body. The term is analogous to sound barrier , but in contrast to this it does not stand for a fixed flow velocity, but for a speed range.

The solution to the heating problem becomes the determining element in designs for the range above Mach  2 (typically Mach 2.6–2.8). The temperature of the envelope at the respective speed depends essentially on the shape of the missile. The construction measures to overcome the "heat wall" include the use of pressure and heat-resistant materials such as titanium or niobium . Further possibilities are the use of heat-resistant plastics and in particular active cooling, for example through the fuel, as in the case of the SR-71 flying at Mach 3.3 .

In the ideal gas with a constant specific heat capacity , the gas temperature increases by at the inflow point at which the gas is decelerated from the inflow velocity c to adiabatically . The increase in temperature therefore grows with the inflow speed as the square of the damming up on solid contours. At Mach> 3, however, real gas effects occur, with the heat capacity changing. As a result, the temperature increase beyond Mach 3 no longer grows quadratically with the flow velocity. ${\displaystyle c_{p}}$ ${\displaystyle c=0}$ ${\displaystyle {\tfrac {c^{2}}{2c_{p}}}}$ ${\displaystyle c_{p}}$

literature

• Heppenheimer, TA Facing the Heat Barrier: A History of Hypersonics Part 1 (PDF; 1.0 MB) and Part 2. (PDF; 496 kB) NASA History Series, 2006.
• Plane in: Microsoft Encarta

Individual evidence

1. ↑ Wolfgang Kümmel: Technical Fluid Mechanics. Theory and practice. 3rd, revised and expanded edition. Teubner, Wiesbaden 2007, ISBN 978-3-8351-0141-8 , pp. 154-157.