Effects of chemical releases by the STS 3 Orbiter on the ionosphere

Abstract

The Plasma Diagnostics Package, which was flown aboard STS-3 as part of the Office of Space Science first Shuttle payload (OSS-1), recorded the effects of various chemical releases from the Orbiter. Changes in the plasma environment were observed to occur during flash evaporator system releases, water dumps and maneuvering thruster operations. During flash evaporator operations, broadband Orbiter-generated electrostatic noise was enhanced and plasma density irregularities (AN/N) were observed to increase by 3 to 30 times with a spectrum which rose steeply and peaked below 6 Hz. Ions with energies up to several hundred eV were also observed during one flash evaporator operation. In the case of water dumps, background electrostatic noise was enhanced at frequencies below about 3 kHz and suppressed at frequencies above 3 kHz during the dump, and AN/N was also seen to increase by 5 to 6 times. Various changes in the plasma environment were effected by primary and vernier thruster operations, including increases in electron density by as much as 3 orders of magnitude, neutral pressure increases to as high as 10" 1 * torr from the nominal 10 torr, and perturbations in the spacecraft potential by several volts, particularly when measured relative to the plasma potential in the wake. Thruster activity also stimulated electrostatic noise with a spectrum which peaked at approximately 0.5 kHz. In addition, ions with energies up to 1 keV were seen during some thruster events.

Analysis of Space Shuttle Primary Reaction-Control Engine-Exhaust Transients

“…where v e 3:5 km s 1 is the far-field exhaust velocity, and NR e is the Brook number density at the axial distance R e [9,10].…”

Advanced Power Sources for Space Missions

“…The velocity u = 3.5 km/s corresponds to an average kinetic temperature of 22000°K for the PRCS exhaust (Murphy et al, 1983;Pickett et al, 1985). Using this correspondence, and taking T = 250°K for the thermalized exhaust, yields Pthermal = 1.8 x ~o -~t o r r .…”

“…An upper limit on the pressure can be obtained by assuming that t = u; that is, there is no cooling of the effluent. Making this assumption, and using u = 3.5 km/s (Pickett et al, 1985) yields, for the Shuttle case above, pmax(Ro) a 2.1 nt/m2 a 1.6 x 10-2torr.…”

Far-Field Spectral Analysis of a Space Shuttle Vernier Reaction Control System Firing

“…An axial exhaust velocity of 3.5 x 10' m s-' was the laboratory [10] and was found to not produce observable assumed, which originates from the exit velocity of 3 x 103 m s-I NH(A-X) radiance at pertinent collision energies. A difficulty with plus an additional 0.5 x 103 m s' attained in the vacuum expansion the remaining candidates is their low stability, which makes it hard to [8,9]. Thus, the overall plume-atmosphere collision velocity along …”

“…Depending on the type of engine, the OH mole [12]. fraction may reach values as high as 4 x l0-3 [7][8][9]. Because the The higher quality OH(A-X) spectrum for the VRCS engine also energy disposed in OH(A) is significantly different in processes 1-3, allowed resolution of a puzzling aspect of the previous analysis of the the observed OH(A-X) spectrum will depend significantly on STS-63 spectrum for a PRCS engine [6].…”