Additively Manufactured Wind Tunnel Balance Cooling Shields

Hypersonic wind tunnel testing produces high model surface temperatures that conduct heat to the internal force balance, and the thermal environment produces force measurement accuracy challenges. At NASA Langley Research Center, water circulating cooling shields are used to prevent aerothermal effects from affecting balance accuracy. The current manufacturing process for all existing NASA Langley cooling shields utilizes brazing for final assembly. This process has been used for decades; however, it is time consuming and highly subject to human error. Unsuccessful brazing leads to cooling shield leaks, and may require repeat attempts to complete assembly. In this paper, Additive Manufacturing (AM) is investigated to improve the manufacturing process of cooling shields. AM technology eliminates the need for brazing, allowing for the fabrication of a cooling shield with less time and money spent. AM also permits enhanced design flexibility, including the smoothing of the liquid flow path. Several challenges were encountered including the definition of water channel design requirements and flow obstruction mitigation. These challenges were overcome and led to the successful manufacture of several additive cooling shields from 17-4PH steel. Laboratory validation of build integrity utilizing CT scans and witness coupons was performed, and flow rate was compared to a conventionally fabricated cooling shield. This investigation suggests that AM cooling shields are a suitable replacement for conventionally manufactured cooling shields in NASA Langley wind tunnel facilities.