AEDC lab creates and installs sensors for aerothermal measurement during tests

  • Published
  • By Deidre Ortiz
  • AEDC/PA
ARNOLD AIR FORCE BASE, TENN. --  The AEDC Aero-thermal Measurements Lab (ATML), known as the Heat Lab, is tasked with fabricating and installing temperature-related sensors and small transducers on test models.

The lab supports AEDC test facilities by providing methods of measuring the heat flux or heat transfer per unit area, per unit time. It benefits testing of thermal protection systems, material sample ablation, boundary layer transition and roughness effects, and protuberance heating.

Heat transfer testing is not a new concept and was widely used in the 1970s and 1980s for testing the space shuttle and the shuttle's external tank foam material, performing boundary layer transition studies and other programs. There is a renewed interest in heat transfer measurements with the development of new hypersonic vehicles.

According to Stuart Coulter, ATA lab engineer, the lab was first formed at AEDC in the 1970s to serve the von Kármán Gas Dynamic Facility by supporting aerothermal measurements.

"We do heat flux sensor design and development and support the tests as needed," Coulter said.

"We also assist in model planning and choice of sensor, the sensor fabrication and then installation in the wind tunnel model," he added. "Many times we come up with custom configurations of sensors and instrument the model and cable it."

The ATML staff at AEDC is a small team, consisting of instrument technicians Brian Anderson, Randall Moon and Annette Painter and engineers Stuart Coulter and David Woods.

"Annette, Randall and Brian do a great job assembling the tiny components into  sensors using wire as small as 0.001 inches in diameter and sensor parts no larger than the letter i in this article," Coulter said. "A steady hand, tiny tweezers, and a microscope are required."

Once a test has started, the ATML folks are sometimes needed to help with troubleshooting and other tasks.

The testing in VKF keeps the lab busy, but most facilities on base benefit from the capabilities.

For example, it serves Tunnel 9 by building sensors and installing them. In the AEDC arc heater facility, sensors are placed in the nose cones for testing to measure arc jet enthalpy. Probes and other specialty thermocouples are built up for use in the Aerodynamic and Propulsion Test Unit (APTU) and Propulsion Research Facility. ATML personnel measure emissivity, an efficiency in which a surface emits thermal energy. Emissivity measurements are needed by the Heatlab staff and by the space chamber staff.

As for the Propulsion Wind Tunnel, ATML team members have in the past installed dynamic pressure transducers, with sensors that can be 1/16 an inch or smaller.

"We also have performed special calibrations for various customers, to help answer data anomalies," Coulter said.

Some of the national programs the ATML has assisted with include the Space Shuttle Return to Flight, NASA Ares Launch Vehicles, the Japanese Hope, Navy Standard Missile, various tests under the Conventional Prompt Global Strike (CPGS) program and Boundary Layer Transition tests.

In the past, work was done on hot-wire anemometry, which uses microscopic wires positioned in boundary layers to measure mass flux, to aid the development of boundary layer theory.

Coulter notes that Joe Donaldson, Frank Kafka and Charles Nelson were AEDC pioneers of this type of work for Wright Patterson sponsored tests.

"Two AEDC fellows, Carl Kidd and William Scott, also came out of the lab [and are recognized] for their heat flux sensor innovations" he said.