SHUTTLE UPPER-ATMOSPHERE MASS-SPECTROMETER EXPERIMENTAL FLIGHT RESULTS

Calibrated pressure measurements for species with mass-to-charge ratio s up to 50 amu/e- were obtained from the shuttle upper atmosphere mass spectrometer experiment during re-entry on the STS-35 mission. The pr incipal experimental objective is to obtain measurements of freestream density in the hypersonic rarefield flow flight regime. Data were col lected from 180 to about 87 km. However, data above 115 km were contam inated from a source of gas emanating from pressure transducers connec ted in parallel to the mass spectrometer. At lower altitudes, the pres sure transducer data are compared to the mass spectrometer total press ure with excellent agreement. Near the orifice entrance, a significant amount of CO2 was generated from chemical reactions. The freestream d ensity in the rarefield flow flight regime is calculated using an orif ice pressure coefficient model based upon direct simulation Monte Carl o results. This density, when compared with the 1976 U.S. Standard Atm osphere model, exhibits the wavelike nature seen on previous flights u sing accelerometry. Selected spectra are presented at higher altitudes (320 km) showing the effects of the ingestion of gases from a forward fuselage fuel dump.