DISPERSION OF TOXIC EXHAUSTS FROM LIQUID ROCKET PROPELLANT COMBUSTION

Integrated Test Range, Chandipur, Orissa, 756 025, India

Fakir Mohan University, Balasore, Orissa, 756 019, India

*Corresponding Author:

R.B. Panda
Fakir Mohan University, Balasore, Orissa, 756 019, India,
E-mail: rb_panda07@rediffmail.com

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Abstract

Environmental impact assessment of liquid rocket motor exhaust obtained due to mainly liquid propellant combustion have been highlighted. Exhaust product analysis has been carried out theoretically by computer software NASA CEC -71 to identify toxic emissions of rocket combustion. In the present study a high volume Air Samplers (APM-430) was deployed at predetermined locations near launch pad for collection of toxic exhausts using liquid absorbents during actual missile launch. The collected samples were analyzed subsequently for quantitative estimation of suspended particulate matter (SPM), oxides of nitrogen (NOX) and oxides of sulphur (SOX) etc. with the help of a spectrophotometer. The dispersion pattern of the various toxic gases verses time and distance has also been monitored.

Keywords

Air sampler, Suspended particulate matter, Exhaust product analysis, Ambient air quality

Introduction

Rocket is a device or engine that converts chemical energy into mechanical motion. Hot gases are produced in combustion chambers of jets and rockets by burning a fuel with oxygen or an oxidizer. The satellite launch vehicle programs use hydrazine, unsymmetrical dimethyl hydrazine (UDMH) and monomethyl hydrazine (MMH) as fuel along with red fuming nitric acid (RFNA), dinitrogen tetroxide and liquid oxygen as oxidizer. A typical liquid propellant consists of G-fuel (equal mixture of xylidene and triethylamine) and red fuming nitric acid is used by missiles. These hypergolic propellants are the most energetic propellants being used the liquid rocket motors all over the world. G-fuel which contains triethylamine with very high vapour pressure is a big fire hazard. Xylidene is toxic whereas triethylamine is a strong irritant. UDMH is known to be carcinogenic. Thus launching of rockets & missiles from a test range produce a lot of toxic gaseous exhausts and pollutants to the local atmosphere. To ascertain environmental safety of these toxic exhaust products there is a need to have study of nature of the combustion products and their quantitative estimation.

Experimental Methods

Theoretical combustion products analysis was carried out for liquid propellant (G-fuel and RFNA) using a computer software NASA-CEC-71.3 Ideal gas equation was used in the theoretical calculations at an operating pressure of 0.1 MPa. Elemental compositions used for theoretical exhaust product analysis were C (21.92930 mol/kg), H (52.1416 mol/kg), N (13.4889 mol/kg) and O (30.9461 mol/kg) with a heat of formation value of ΔH_f : -2189.62 kJ/kg. A high volume Air sampler (APM-430) using glass fibre micro filter paper (GF/4) was employed for collection of suspended particular matter (SPM) as shown in Fig.1. The detailed experimental procedure has been described elsewhere.4 Quantitative estimation of SPM is normally expressed in μg/m³. However, for collection of toxic combustion gases like oxides of sulphur, SOx and oxides of nitrogen, NOx etc. liquid absorbents were used. The collected samples were analyzed subsequently for quantitative estimation with the help of a UV-visible spectrophotometer. This experiment is repeatedly being carried out before, during and after actual rocket launch.

Fig. 1 Collection of gaseous exhaust with the help of Air Samplers

Table 1. Theoretical exhaust product analysis for liquid propellants

Table 2. Exhaust product analysis during experimental flights for liquid propellants

Result and Discussion

Air pollution may be described as the presence of air pollutants in the atmosphere to such an extent that they cause deterious effects. Primary air pollutants are emitted directly into the atmosphere and secondary air pollutants are formed in the atmosphere by reactions among two or more pollutants. The concentration of air pollutants depends not only on the quantities that are emitted directly from air pollution sources but also on the ability of the atmosphere to either absorb or disperse these emissions along with the various physical and chemical dissipation processes liable to remove pollutants through self purification processes (Garg, 1998). Vehicular transportation vitiated the environment by emanating obnoxious and toxic pollutants like oxides of nitrogen, (NOx), carbon monoxide (CO), hydrocarbon (HC) and particulate matter to the surrounding atmosphere, which results in serious health hazard to community. Similarly fly ash, oxides of sulphur, (SOx), oxides of nitrogen, (NOx) and CO₂ emerges to be four major pollutants of concern in thermal power plant emissions (Dash, 2004). In the wake of industrialization consequent rapid urbanization, economic development and ever increasing population over last few decades, ambient air pollution problems has increased by several folds (Kudisia, 2003).

The impact of air pollution on human beings has been the major force motivating efforts to control it. toxic emissions are very fast thereby reducing any adverse effect to the environment.

Acknowledgement

Authors are grateful to Shri S P Dash, Scientist, ‘H’, Director, ITR for sanction of a CARS project. Thanks are due to Shri R S Palliah, Sc ‘D’ HEMRL, Pune for help in carrying out theoretical exhaust product analysis.

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