Permanent-Change Thermal Paints for Hypersonic Flight-Test

摘要

This report describes the ongoing work performed over the last 18 months on the investigation of the use of permanent-change thermal paints for mapping structural heating during hypersonic flight tests. This technique has a number of practical advantages of other established thermal mapping methods including the low cost and overhead associated with the application of these coatings to a flight vehicle and the ease of good spatial coverage. Techniques to identify the components and analyze the chemical behavior of these paints analyze and have been established and demonstrated and these are reported in detail. An investigation of the pressure dependence of the paint response is described but has to date been inconclusive and is ongoing. Numerically based techniques have been established and demonstrated to model the full transient heating of the vehicle across its trajectory. These methods can account for the fluid-thermal-structural interactions associated with the aerothermodynamics heating of the vehicle and its structural response. These simulations have successfully been applied to the critical portion of the atmospheric descent of the HIFiRE-0 payload. The numerical techniques and initial simulations are described. A practical laboratory-based method of reproducing the transient heating histories representative of flight has been developed and demonstrated. This incorporates a computer-controlled high-power TIG welder to heat the sample via an electric arc. This heating method can be applied to non-metallic samples via the use of a target heat sink placed in thermal contact with sample and this has been successfully demonstrated. Thermal paint coatings have been successfully applied to HIFiRE-0 vehicle and flown. Clear color change was evident in regions of high heating and this conforms well to initial estimates. This initial analysis of color change on the recently recovered HIFiRE-0 payload is described although this work is still at an early stage.