Observations of the optical emissions from the space shuttle's thrusters have been examined. Particular attention has been paid to the interaction of the thruster plume with the atmosphere. Emissions from CN, CH, C2, HNO, and NO 2 have been observed near the nozzle of the thruster in the vacuum core region of the plume, but these emissions are the direct result of the combustion process. Other emissions including OI and NH have been observed in the downstream region of the plume, where the plume effluents interact with the atmosphere. The NH emission is one of the most dominant UV/ visible wavelength emissions observed in the plumes. This emission was observed to extend several thousand meters from the shuttle, and detailed analysis shows that the total intensity of the emission depends on the ram angle (angle in the shuttle reference frame between the plume effluents and the ramming atmosphere) and altitude, indicating an interaction process with the atmosphere. Data from two observational experiments are presented. The Air Force Maui Optical Site (AMOS) experiment includes ground-based spectral and spatial measurements of the shuttle plumes as the thrusters were fired over the AMOS site on top of Haliakala Volcano on the island of Maui in the mid-Pacific. The GLO experiment was flown in the payload bay of the space shuttle and also includes spectral and spatial measurements of the shuttle plumes. During both of these experiments, the primary reaction control system (PRCS) engines (870 lb (394 kgf) thrust) and Vernier reaction control system (VRCS) engines (25 lb (11 kgf) thrust) were fired at various angles relative to the ram, thus providing a range of collision velocities (4.5-11 km/s) between the thruster plume and the atmosphere. In this report the dependence of the NH emission on ram angle, thruster size, and distance from the shuttle is presented and analyzed using a three-dimensional Monte Carlo simulation of the plume-atmosphere interactions called spacecraft/orbiter contamination representation accounting for transiently emitted species (SOCRATES). The chemical reactions deemed most likely involve collisions of the plume products HNC, HNCO, and CH2NH with atmospheric O, and all of these processes are examined. The ram-angle dependence is used to determine a threshold energy required for the reaction that leads to the NH emission and to conclude that the most likely reaction involves CH2NH collisions with O. orbit (-200-500 km) undergo complex interactions with the atmosphere because of the rarefied and reactive nature of the atmosphere at these altitudes. These interactions lead to the generation of local atmospheres that are quite different from the ambient atmosphere. The rarefied atmosphere and the relatively high orbit velocity also produce a unique opportunity to study high-velocity one-step and twostep chemical processes. The large scale lengths provide an environment where it is possible to study extremely long lived metastable species. The state of the local spacecraft environ-Paper number 95JA...
We present in this paper results of a predictive code (SOCRATES: spacecraft/orbiter contamination representation accounting for transiently emitted species) which has been developed to assess the effects of contamination on measurements aboard spacecraft in low Earth orbit. SOCRATES is a Monte Carlo code which includes in its present version scattering, collisions leading to kinetic‐to‐vibrational energy transfer, and reactive collisions. The application of this code to actual measurements aboard spacecraft in low Earth orbit makes it possible to evaluate data obtained on these platforms with a view toward extracting the data of interest from contaminated signals. Molecules considered in the present study include CO2, H2O, OH, H2, and CO.
Recent broad band‐pass infrared (2.3–3.6 μm) observations of the interaction of the exhaust plumes from space shuttle ram firing dual primary reaction control system (PRCS) engines with atmospheric atomic oxygen, O(3P), are analyzed. The results from previous laboratory and space‐based experiments that observed the IR emissions from the high‐velocity interaction of O(3P) and H2O are reexamined. Specifically, emission in the 2.7‐μm region is reinterpreted in terms of the reactive process O(3P) + H2O → OH(ν) + OH rather than the collisional excitation mechanism O(3P) + H2O → H2O (ν1 and ν3) + O(3P), which was the focus of the previous analyses. A spectral analysis is presented of a previously reported molecular beam experiment that obtained spectrally resolved emission measurements for a relative collision velocity of 8 km/s between O(3P) and H2O and that shows that OH(ν) is the dominant source of emission in the 1 to 5‐μm region. The effect of rotational radiative relaxation is discussed, and it is shown that for highly rotationally excited molecules the timescale for this process can be much faster than vibrational radiative decay, thus resulting in much narrower spectral distributions than might ordinarily be expected.
Radiation resulting from interaction between the effluent cloud of a space shuttle thruster and the ambient atmosphere was observed with a spectrograph aboard the shuttle. The spectral measurements were made between 400 and 800 nm with a resolution of 3 nm. The primary emissions are identified as NO2, HNO, O(•D), and O(•S). These are the first observations of O(•S) emission in the shuttle plume. These data are compared with previous measurements, and possible excitation mechanisms are discussed. The results are also compared with a Monte Carlo simulation of thruster plume-atmosphere interaction radiation. 5819 5820 VIERECK ET AL.: OXYGEN EMISSIONS IN SHUTTLE THRUSTER PLUMES
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.