voslamber leppich lo space emissions due to rocket launches

8/14/2019 Voslamber Leppich Lo Space Emissions Due to Rocket Launches

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WORLD WIDE EMISSIONS DUE TO ROCKET LAUNCHES

21st General Assembly der Geophysical Society, Den Haag, 9.Mai 1996

M.E. Voslamber (TU Berlin, Institut fr Luft- und Raumfahrt, Marchstrae 12,

10587 Berlin, Germany)

J. A. Leppich and R. E. Lo (TU Berlin, Institut fr Luft- und Raumfahrt,Marchstrae 12, 10587 Berlin, Germany)


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Abstract

Space missions range rather low in the scenario of atmospheric pollution caused by world traffic

activities. However, rocket launches are unique in their emission profile: above the highest aero-nautical traffic lanes rockets are the only sources of pollutants and every launch covers all atmos-

pheric strata. This paper presents an overview of the world wide distribution of gases emitted into

the atmosphere by space launches. Type and amount of emissions have been determined from thebeginning of space flight in 1957 until 1994. Emission data in terms of combustion gas composi-

tion were calculated for the working point of every rocket engine used in that period of time. A

detailed geographical distribution for the year 1991 is presented in tables and graphs. The modelused considers all rockets capable of attaining orbital altitude. The emanations are grouped by gas

type and shown in an atmospheric grid with an accuracy of 5 latitude and 25 longitude. The

altitude grid rests on a meteorological scale based on atmospheric pressure and consists of 47

grid points in the range between sea level up to 150 km. Furthermore some explanations will begiven about the assumptions underlying the calculation model, e.g. concerning trajectories flown

or type of gases emitted.


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1 IntroductionPollutions emitted by rocket launch vehicles play a particular role in determination of atmos-

pheric emissions. They are of great interest, since launchers represent the only transport vehicleto cross all of the atmospheric strata. Furthermore space technology is accessed by an increasing

number of countries around the world, with the effect, that meanwhile emanations due to space

traffic are distributed globaly. The utilization of various propellants and propellant compositionsresults, after their combustion, in a versatile substance catalogue. Thus they have to be considered

and analysed with more precision.

The research of the Aerospace Institute at the Technical University of Berlin concerning the cal-

culation of the absolute mass of the emitted gases rests upon many sources. The history of spaceflight (vehicles launched succesfully into earth orbit) induced emissions starts with Sputniks firstflight in October 1957 and the data used for this investigation ends currently at the 31st of De-

cember 1994. The world wide distribution in longitude, latitude and altitude is much more com-

plex and is now available for the year 1991.

2 Calculation modelThe calculation considers all launchers capable of attaining orbital altitude. This includes e.g. thewhole European "Ariane" family, the Chinese "Long March" family, the Japanese "H series", the

American "Delta" and "Atlas" rocket, the "Shuttle" transportation system, all Russian launchers

not forgetting the Brazilian, Indian and Israelian rockets and many more. All these rockets arestored in a database including their dimensions, masses, used stages and engines. The engines

represent the source of the pollution of any launcher and the propellant mass data of the stages

determines the quantity of substances. The emissions originate in the combustion chamber and

the composition of them is influenced by parameters like propellant mixture ratio, chamber com-bustion pressure and expansion ratio. For further calculation performance data like thrust and

exhaust velocity has to be stored for every engine. All these data is included in the mathematical

model.

A NASA computer code (Gordon et.al. 1976) was used for the calculation of the composition ofemissions.To determine the geographical distribution of the emitted gases and substances the

trajectory of every launcher must be known. For this purpose a computer code was written at the

institute which assumes that all launchers use great circle courses and a gravity-turn manoeuvrewas made for orbit injection. Since this type of flight is the most utilized one, the possible errors

rests in an acceptable range.

The special features of the gravity-turn trajectories used for this calculation are divided into the

following phases: A vertical ascent of an average time of 10 to 12 sec followed by gravity-turn

manoeuver with an initial angle of attack between 2 and 4. With the computer code mentionedabove it is possible to obtain the absolute vectors of the launcher in respect to the time after lift-

off. The accuracy of the calculated geographical vectors suffice entirely to the one chosen for thegeographical grid (5 latitude * 22.5 longitude). The altitude grid is based on a meteorologicalmodel, that considers altitude zones of equal pressure.

3 Emission distributionThe world wide distribution of emitted substances for the year 1991 is shown in Fig 1 to

Fig 7.The masses of the gases and substances are given in kg over the altitude in respect to a

launchsite.

The launchsites used in 1991 are:


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Kourou in French Guyana (5N-53W)

Kennedy Space Center (KSC) at Cape Canaveral in the USA (28.5N-81W)

Plesetsk in the north west of Russia (63N-40E)

Tanegashima Space Center at the south end of Japan (30N-131E)

Tyuratam in mid Russia at (46N-63E)

Vandenberg Air Force Base (VAFB) on the west coast of the USA at (35N-121W)Xichang in the middle of southern China at (28N-102E)

Distribution at Kennedy Space Center

1,0E+03

1,0E+04

1,0E+05

1,0E+06

0 2 0 4 0 6 0 8 0 1 00 1 20 1 40 1 60

Altitude [k m]

CO

CO 2

H2O

N2

Al2O3

HC l

Fig 1 Distribution of different substances over Kennedy Space Center for the year 1991


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Distribution at VAFB

1,0E+02

1,0E+03

1,0E+04

1,0E+05

0 2 0 4 0 6 0 8 0 1 00 1 20 1 40 1 60

Altitude [k m]

C O

C O2

H2O

N2

Al2O3

HC l

Fig 2 Distribution of different substances over Vandenberg Air Force Base for the year 1991


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Distribution at Plesetzk

1,0E+03

1,0E+04

1,0E+05

1,0E+06

0 2 0 4 0 6 0 8 0 1 00 1 20 1 40 1 60

Altitude [km]

CO

CO 2

H2O

N2

Fig 3 Distribution of different substances over Plesetsk for the year 1991


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Distributio n at Turyatam

1,0E+03

1,0E+04

1,0E+05

1,0E+06

0 2 0 4 0 6 0 8 0 1 00 1 20 1 40 1 60

Altitude [k m]

CO

CO2H2 O

N2

Fig 4 Distribution of different substances over Tyuratam for the year 1991


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Distribution at Kourou

1,0E+02

1,0E+03

1,0E+04

1,0E+05

1,0E+06

0 2 0 4 0 6 0 8 0 1 00 1 20 1 40 1 60

Altitude [km]

CO

CO2

H2O

N2

Al2O3

HCl

Fig 5 Distribution of different substances over Kourou for the year 1991


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Distribution at Tanegashima

1,0E+02

1,0E+03

1,0E+04

1,0E+05

0 2 0 4 0 6 0 8 0 1 00 1 20 1 40 1 60

Altitude [km]

CO

CO 2

H2O

N2

Al2O3

HC l

Fig 6 Distribution of different substances over Tanegashima for the year 1991


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Distribution at Xichang

1,0E+02

1,0E+03

1,0E+04

1,0E+05

0 2 0 4 0 6 0 8 0 1 00 1 20 1 40 1 60

Altitude [km]

CO

CO2

H2O

N2

Fig 7 Distribution of different substances over Xichang for the year 1991

The mentioned substances in the plots represent only a selection of the total number of sub-

stances emitted during that year. The following ejections were not mentioned: C2H5, H, H2, NH3,

NO, O, OH, O2, Cl, C, H2O2, CH4, NO2, HO2, AlCl, Fe,FeCl2 and HF. Compared to the ones fig-ured later their masses are relatively small and in some cases zero.

When looking at Fig 1 one can see, that the masses decrease suddenly at an altitude of about60 km. This is a typical progression for a stage cut-off and separation. In this figure it represents

the cut-off and separation of the solid rocket booster of the Space Transportation System (STS =

US Space Shuttle).

The oscillations of the emission data seen in all graphics is due to the fact, that the trajectories usea 1 second time grid which has to be transfered to the altitude grid. The amount of emissions in a

specific altitude range is calculated by multiplying the mass flow rate of the engines with the pe-

riod of time (delta t) corresponding with the altitude grid. Since the altitude grid is not equidistant

and the mass flow rate is constant there is a variation in the calculated amount.

The small acceleration at the beginning of the ascent causes a high amount of emissions in low

altitudes (up to 10 times more than the amount at higher altitudes). Later the acceleration in-

creases because of the constant thrust and the decreasing launcher mass. Moreover with growing

altitude the drag force is reduced because of the sinking atmospheric density. At a certain altitudethe masses reach a minimum. The reason can be found in the features of the gravity-turn trajec-

tory. As explained above the trajectory consists of three phases: vertical ascent, period of forced

inclination and gravity-turn manoeuvre. The local pitch angle (angle between zenit and velocityvector of the rocket) of the launch vehicle increases from 0 to 90. So the hold up time in a spe-


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cific altitude grows with increasing pitch angles. The effect is of cause an increasing ejection of

substance masses for a definite altitude range.

4 Substance behaviourAfter having shown the masses and the geographical location of the emitted gases, some informa-tion has to be given on their properties and behaviour.When exiting the nozzle the gases have a

temperature between 300C and 3000C. In addition there is a high relative velocity between the

jet flow and the surrounding atmosphere. Hence a combustion with the atmosphere has to be ex-pected. The figures show only the composition at nozzle exit.

The exhaust velocity of the gases varies in a range of about 2000 m/s to 4500 m/s. So, when leav-

ing the nozzle the relative velocity rate depends on the speed of the launcher. This speed vector

varies between the maximum exhaust velocity of the substances at the moment of lift-off and the

maximum launcher velocity minus the exhaust velocity of the gas at the moment of injection.Since the launcher attain a speed of more than 7000 m/s, there has to be a point, where the rela-

tive exhaust speed of the gases are zero.

As seen above the main mass of the emitted substance is emitted at low altitude. This is due to

the fact, that nearly 90 % of the propellants is stored in the first and second stage and approxi-mately 60 to 70 % in the first stage. Moreover the relative velocities of the gases at low altitude

cause the substances to sink to ground. But this effect is not considered in the model.

It is obvious that the emission masses are directly proportional to the number of launches and of

course also directly proportional to the propellant mass of the launcher himself. Hence it wouldbe interesting to get a trend of the future launch rates depending e.g. on the development of the

International Space Station Alpha and the demand for satellite launches. Thus a computation of

the emissions considering future launcher technologies (Heavy Lift Launch Vehicles and SingleStage To Orbit using LOX and LH2) and future launch rates would result on relatively exact as-

sumptions on launcher emissions.

5 ReferencesGordon, McBride, Computer Program for Calculation of Complex Chemical Equilibrium Com-

positions, Rocket Performance, Incident and Reflected Shocks, and Chapman-Jouguet Detona-tions, NASA-SP-273, Interim Revision, March 1976

voslamber leppich lo space emissions due to rocket launches

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