High Altitude Plume Chemistry Lab        

BACKGROUND & INTRODUCTION (Pictures Below)                        

The interaction of rocket plumes with the earth's atmosphere is an important area of study for environmental and remote sensing considerations. Little is known of the detailed chemistry in the trail of a rocket plume, especially in the upper atmosphere. Computational fluid-hydrodynamic models of plume flowfield chemistry must be constructed and validated with laboratory data obtained at the same pressures, temperatures and chemical environments expected at high altitudes in order to allow evaluation of existing and future rocket systems. Such experiments are carried out in the High Altitude Plume Chemistry Lab at The Aerospace Corporation.

Rocket plume chemistry studies in this Lab have centered around several issues, including:

(1) What are the effects of chlorine (from perchlorates) released by rocket motors, and what chemical reactions occur between the chlorine-containing rocket plume and the ambient atmosphere? Since the ambient atmosphere at high altitudes has an abundance of dissociated ground-state oxygen atoms and other radicals, there is a large potential (which was confirmed in the laboratory) for chlorine-containing compounds to "afterburn" into Cl and ClO, which are ozone active substances and may deplete the stratospheric ozone locally.

(2) Unburned fuel in rocket plumes can react with atomic oxygen at high altitudes and yield bright chemiluminescent emissions. These emissions are a significant source of clutter for remote sensing instruments. We have been active in measuring chemical kinetic data on the reactions of fuel molecules with oxygen atoms at low pressures to simulate the chemistry of a rocket plume in the upper atmosphere.

(3) What are the effects of soot (and other particulates) on the upper atmosphere?  In particular, how is soot produced/consummed in rocket plumes at high altitudes?

These experiments are carried out primarily in two high-altitude (low pressure) flame simulation experiments. The Low Pressure Combustion Chamber is a stainless steel vacuum flowtube with sapphire windows and a hydrogen - oxygen burner to simulate high altitude plume afterburning. In addition to being able to perform spectroscopic observations in the UV - visible - IR regions of the spectrum, it is attached to a high-Q quadrupole Mass Spectrometer for quantifying stable chemical species in the flame. The second apparatus is a Fast Flow Discharge System, traditionally used to measure chemical kinetic data for specific reactions. It is ideally suited to studying the reactions between fuel molecules (acetylene, methane, ethylene, kerosene, etc.) and oxygen atoms or other relatively stable atomic species.

Several novel measurements have been made, including the quantitative attribution of CO (a -> X) Cameron Bands (at about 200nm wavelength) to the reaction C2O + O -> CO* + CO. We have also shown that the production of C2O from C3O2 is highly temperature dependent, but that enough energy is liberated in the reaction C2H2 + O -> (products) to produce significant C2O at all temperatures.

Current efforts include the characterization of IR emissions from various fuels reacting with O atoms, and studying the fates of various pollutant species, including CO and NOx and soot particles, in a rocket plume afterburning environment. The latter is particularly important from an environmental standpoint since it is very difficult to measure high altitude plumes in-situ and current rocket plume chemical kinetic computer models do not accurately predict the chemistry of minority species, such as pollutants.
 
 


 


 

  • Low Pressure Combustion Chamber for High-Altitude Rocket Plume Chemistry Studies at Pressures Corresponding to the mid-Troposphere to Above the Stratosphere.

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  • Quadrupole Mass Spectrometer for Detection and Measurement of Gaseous Molecular Species in Combustion Products: Used in Conjunction with the Low Pressure Combustion Chamber.

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  • Low pressure flame with soot particles present - simulates what rockets do to the chemistry of the earth's stratosphere.  (The probe for the mass spectrometer is entering the flame from the top.)

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