MadSci Network: Earth Sciences

Re: How much pollution does each space launch produce?

Date: Tue Oct 31 09:51:58 2000
Posted By: George Adams, , Chemical Engineering graduate, none
Area of science: Earth Sciences
ID: 971784229.Es

Pollution caused by space launches:

The magnitude of space launch combustion products can be illustrated by a 
comparison of the amount of fuel consumed by a  space shuttle launch with 
the amount of gasoline consumed in the United States in one day:

Space shuttle fuel consumed in a launch:  3.5 million pounds
Gasoline consumed in one day in the US - 2,500 million pounds
In other words, one space shuttle launch is equivalent to about two minutes 
of gasoline consumption in the United States.

There were 78 space launches worldwide in 1999, almost all much smaller 
than the space shuttle.

The pollution caused by space launches depends not only on the total 
quantity of the fuels used, but on their chemical composition..

 Propellants used for powering space launches are of four types:

1. Solid  - Propellants that are a mixture of solid chemicals - a fuel and 
an oxidizer - that burn at a rapid rate when ignited, expelling hot gasses 
from a nozzle to achieve thrust. Fireworks are an example of the use of 
this kind of propellant. The combustion products depend on the chemicals 
used. The space shuttle uses potassium perchlorate (KClO4) and powdered 
aluminum. The combustion products are  potassium chloride and aluminum 

2. Cryogenic - In space propellants, this refers to liquid hydrogen (LH) 
and liquid oxygen (LOX), which burn when mixed and ignited. LOX is a liquid 
below -298 degrees F and LH is a liquid below  -423 degrees F. They are 
stored in the space vehicle in insulated tanks and pumped into the rocket 
engines where they burn to expel hot gases.  The LOX/LH combination is by 
far the most efficient in the amount of thrust per pound of fuel.  The 
combustion product is water vapor.

3. Petroleum - Instead of liquid hydrogen, a purified kerosene is used as 
the fuel and is mixed with liquid oxygen and burned in the engine. The 
combustion products are carbon dioxide and water vapor. This fuel system is 
usually used in launches of smaller rockets where the complications of 
handling liquid hydrogen are not justified. 

4. Hypergolic - fuels and oxidants that ignite on contact without an 
ignition source.  These are generally used for maneuvering after the soak 
vehicle has reached orbit. The combustion products depend on the chemicals 
used.  The space shuttle uses monomethyl hydrazine (N2CH6) and nitrogen 
tetroxide (N2O4).  The combustion products are nitrogen, water vapor and 
carbon dioxide.

The pollution effects of the four types of fuels are:

Solid fuel - The major combustion products of potassium chloride and 
aluminum oxide and relatively innocuous.  Potassium chloride is used as a 
fertilizer and has medicinal uses.  Aluminum oxide is an unreactive 
compound and is used as an abrasive.

Cryogenic - The only combustion product of LH/LOX is water.

Petroleum - The combustion products of water and carbon dioxide are 
harmless except of any possible contribution of carbon dioxide to global 
warming, but the carbon dioxide from this source  would be infinitesimal 
compared to the energy produced by burning  coal and petroleum

Hypergolic - The combustion products of this kind of fuel are not a 
pollution problem. In any event this fuel is used only in small quantities 
for maneuvering.

The space shuttle uses about 2.3 million pounds of solid propellant in the 
launch boosters and about 1.2 million pounds of LH/LOX in the main engines. 
A relatively small amount of hypergolic fuel is used for controlling the 
shuttle once in orbit. Kerosene/LOX propellant is not used.

With regard to possible effect on the ozone layer, the only combustion 
product that would be suspect is the chloride ion of potassium chloride. 
Studies have shown that in contrast to organic chlorine (as in banned 
refrigerants) inorganic chloride does not persist in the altitudes of the 
ozone layer and is not a factor in ozone depletion.

Ozone Depletion FAQ Part II:  Stratospheric Chlorine and Bromine

1999 Space launch report

Space Shuttle Solid Rocket Boosters


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