Bartlett, James E. | Engineering Papers

NASA NTRS2000

Pegasus(Registered trademark) Wing-Glove Experiment to Document Hypersonic Crossflow Transition: Measurement System and Selected Flight Results

In a recent flight experiment to study hypersonic crossflow transition, boundary layer characteristics were documented. A smooth steel glove was mounted on the first stage delta wing of Orbital Sciences Corporation's Pegasus (R) launch vehicle and was flown at speeds of up to Mach 8 and altitudes of up to 250,000 ft. The wing-glove experiment was flown as a secondary payload off the coast of Florida in October 1998. This paper describes the measurement system developed. Samples of the results obtained for different parts of the trajectory are included to show the characteristics and quality of the data. Thermocouples and pressure sensors (including Preston tubes, Stanton tubes, and a "probeless" pressure rake showing boundary layer profiles) measured the time-averaged flow. Surface hot-films and high-frequency pressure transducers measured flow dynamics. Because the vehicle was not recoverable, it was necessary to design a system for real-time onboard processing and transmission. Onboard processing included spectral averaging. The quality and consistency of data obtained was good and met the experiment requirements.

Bertelrud, Arild↗

NASA NTRS2000

An Integrated MEMS Sensor Cluster System for Aerospace Applications

Efforts to reduce viscous drag on airfoils could results in a considerable saving for the operation of flight vehicles including those of space transportation. This reduction of viscous drag effort requires measurement and active control of boundary layer flow property on an airfoil. Measurement of viscous drag of the boundary layer flow over an airfoil with minimal flow disturbance is achievable with newly developed MEMS sensor clusters. These sensor clusters provide information that can be used to actively control actuators to obtain desired flow properties or design a vehicle to satisfy particular boundary layer flow criteria. A series of MEMS sensor clusters has been developed with a data acquisition and control module for local measurements of shear stress, pressure, and temperature on an airfoil. The sensor cluster consists of two shear stress sensors, two pressure sensors, and two temperature sensors on a surface area of 1.24 mm x 1.86 mm. Each sensor is 300 microns square and is placed on a flexible polyimide sheet. The shear stress sensor is a polysilicon hot-film resistor, which is insulated by a vacuum cavity of 200 x 200 x 2 microns. The pressure sensors are silicon piezoresistive type, and the temperature sensors are also hot film polysilicon resistors. The total size of the cluster including sensors and electrical leads is 1 Omm x 1 Omm x 0.1 mm. A typical sensitivity of shear stress sensor is 150 mV/Pascal, the pressure sensors are an absolute type with a measurement range from 9 to 36 psia with 0.8mV/V/psi sensitivity, and the temperature sensors have a measurement resolution of 0.1 degree C. The sensor clusters are interfaced to a data acquisition and control module that consists of two custom ASICs (Application Specific Integrated Circuits) and a micro-controller. The data acquisition and control module transfers data to a host PC that configures and controls a total of three sensor clusters. Functionality of the entire system has been tested in the laboratory, and preliminary test results are presented.

Kahng, Seun↗

NASA NTRS1995

Microsensor Hot-Film Anemometer

Improved hot-film anemometer developed for making high-bandwidth turbulence measurements in moderate-enthalpy supersonic and hypersonic flows (e.g., NASP inlets and control surfaces, HSCT jet exhaust). Features include low thermal inertia, ruggedness, and reduced perturbation of flow.

Mcginley, Catherine B.↗