Quantitative Spectral Radiance Measurements in the HYMETS Arc Jet

Abstract

Calibrated spectral radiance measurements of gaseous emission spectra have been obtained from the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. A fiber-optic coupled spectrometer collected natural luminosity from the flow. Spectral radiance measurements are reported between 340 and 1000 nm. Both Silicon Carbide (SiC) and Phenolic Impregnated Carbon Ablator (PICA) samples were placed in the flow. Test gases studied included a mostly-N 2 atmosphere (95% nitrogen, 5% argon), a simulated Earth Air atmosphere (75% nitrogen, 20% oxygen, 5% argon) and a simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon). The bulk enthalpy of the flow was varied as was the location of the measurement. For the intermediate flow enthalpy tested (20 MJ/kg), emission from the Mars simulant gas was about 10 times higher than the Air flow and 15 times higher than the mostly-N 2 atmosphere. Shock standoff distances were estimated from the spectral radiance measurements. Within-run, run-to-run and day-to-day repeatability of the emission were studied, with significant variations (15-100%) noted.

Application of FLEET Velocimetry in the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel

“…Figure 1 shows two spectralresponse-calibrated, temporally-integrated FLEET spectra taken at ambient temperature and a reduced temperature (collected and calibrated in a manner consistent with Ref. 35). The peak intensity of the emission band in the UV portion of the spectrum is found to remain largely unchanged as a consequence of the temperature difference.…”

Synthesis of Fluorophore-Doped Polystyrene Microspheres: Seed Material for Airflow Sensing

“…DOE Response Parameters and Goals response goal mean particle diameter 1 μm particle size distribution (i.e., magnitude of standard deviation (σ)) minimize σ (≤25%) fluorescent emission maximize dye retention (ret%) maximize leach solution absorbance at 400 nm minimize the background intensity and correcting for the relative spectral response of the detection system. 35 Several additional factors were involved in order to enable accurate comparison of the spectral data. The thickness of the sample plays a large role in signal strength.…”

High-Speed Imaging Optical Pyrometry for Study of Boron Nitride Nanotube Generation

“…This spectrometer had been used previously for visible emission spectroscopy in arc-jet flowfields and was adapted to the current work. 8 A spherical lens directed light from the test section onto the optical fiber. The spectrometer was set up with nearly 1:1 imaging, using a 200 micron diameter fiber, resulting in a measurement area of slightly less than 200 micron diameter.…”