The Space Shuttle uses one type of propulsion system -- rocket propulsion. This is a basic type of propulsion that relies on the exhaust emitted from the engines. The higher speeds of the rocket, reducing the mass of propellant, the less power is needed to boost the ship and payload. “It works exclusively on the principle of conservation of momentum, which manifests itself in Newton’s well known third law [if a body (A) exerts a force on body (B), then body (A) will exert a force on body (B) ]” (Mallove 37). The measurement of a rocket’s efficiency is called specific impulse-- the thrust of a rocket’s exhaust multiplied by time.
The Space Shuttle has two types of rockets that bring it to orbit around the earth. The main engines use cryogenic fuel, a liquid state of gas. Liquid hydrogen and liquid oxygen are used and stored in a large, non-reusable tank which is mounted on the bottom of the Shuttle. Hydrogen is the fuel, and the oxygen serves as the oxidizer which supports the combustion of the fuel. There are three main engines that are powered by this efficient fuel. “Hydrogen has about forty percent more ‘bounce to the ounce’ than other rocket fuels, and is very light, weighing about one -half pound per gallon” (“Propellants”). These engines give the Shuttle the bulk of its thrust, about 455 seconds of specific impulse. The second engine that powers the Shuttle is fueled by solid propellants. This form is a much easier and simpler way of thrust. The two solid rocket boosters are completely self-contained and are reusable after a launch. The fuel is housed in a steel casing of the rocket and burns from the inside out. Once the fuel is ignited, the process cannot be reversed, unlike the hydrogen- oxygen engine, which can, if needed. Each case holds about 1.1 million pounds of solid chemicals: aluminum powder (fuel), ammonium perchlorate (oxidizer), iron oxidized powder (catalyst), polybutadiene acrylic acid acrylonitrile (binder), and epoxy-curing agent. All of these chemicals give the Shuttle an added 242 seconds of specific impulse, for a total of 6,610,000 pounds of thrust.
With all the chemicals that make up the propellants for the boosters, it is obvious that the exhaust has massive effects on the ozone and surrounding environment. When the Shuttle launches off from Kennedy Space Center in Florida, to some people, it is a beautiful sight to witness. All the billowing thick white clouds spread out as the Shuttle lifts off into orbit. It is these fluffy, white clouds from the rocket boosters that researchers think contribute to ozone depletion and other harmful environmental effects. “NASA tells visitors attending Shuttle launches. . . that a powdery residue from the exhaust plumes could be deposited up to 10 kilometers from the launch pad . . . can irritate eyes and respiratory tracks . . . even damage the finish on your car” (Aftergood 34). Studies have been conducted by NASA and other scientists that show different views on this exhaust.
Reports have been made by NASA in the years 1978 and 1990. In the 1978 Environmental Impact Statement, NASA estimated the exhaust emissions of the Shuttle launches and concluded that hydrogen chloride, chlorine, nitric oxide carbon monoxide, carbon dioxide, water, and aluminum oxide were all byproducts of the Shuttle launches. During the study, it also was noticed that nitric oxide and carbon dioxide were a result when exhaust was reacting to the atmosphere. The statement also determined how much of each product was emitted at what layers in the atmosphere. From this information, the exhaust which interacts with the ozone layer, stratosphere (8 to 15 kilometers), and poses the threat of its depletion, is about 57,700 kilograms of hydrogen chloride. This interacts with hydroxyl radicals, natural elements in the atmosphere, and causes a release of chlorine. “The chlorine acts as a catalyst in the break down of ozone and, as a catalyst, it is not consumed by the reaction. It becomes part of a continuous cycle of destructive reactions that are still not fully under stood” (Aftergood 35).
In contrast, the 1990 version of the Environmental Impact Statement reported to Congress minimized its findings and acknowledged only the release of chlorine into the atmosphere. The report was based on nine launch simulations from both the Space Shuttle and Titan IV and combined estimated results of chemicals annually released in the stratosphere. “. . . Space Shuttle launches at the current rate pose no significant threat to the ozone layer and will have no lasting effects on the atmosphere” (“NASA”). The report said the plume chlorine release was about .25 percent of the total chlorine released world wide. In reality, exhaust from the rocket boosters is dangerous, and according to Paul Laviolette, from Navy’s Ocean and Atmospheric Laboratory, Mississippi, the testing of rocket boosters on the ground, in 1992, burned the equivalent of 10,000 tires. Environmentalists have concluded that the burning of tires releases green house gases which, in turn, cause the ozone layer to break down. In addition, the Environmental Protection Agency has concluded that detection of ozone depletion over the U.S. is greater than what was speculated. Though NASA has researched two reports, they seem to stand behind the 1990 report to Congress.
Not only do the plumes effect the atmosphere, they also have noticeable local effects around the launch pad. At the launch site in Florida, the exhaust that is first emitted when the engines are turned on is sprayed with water. This reduces the noise level and vibrations and is even said to dampen the released exhaust. After contact with the plume, the water is high in acid. Near by the launch, bushes up to 5 kilometers in distance have been detected to be coated with the powdery residue that NASA officials warn visitors about. This dust interferes with the plants’ natural process of photosynthesis and even changes the color of the leaves. A much more drastic local effect occurs in the nearby lagoons. After each launch of the Shuttle, the water becomes polluted with the powder: “. . . the rapid increase in acidity severely damages the gills of the fish, suffocating as many as 1000 per launch” (Aftergood 35). According to Environmental officials of the U.S. Air Force, “at least they die for a greater good.” The U.S. Air force goes on the say that the effected animals should “be considered dedicated in the interest of the mission” (Aftergood 35). Converse to the dramatic environmental findings, NASA Magazine, Spring 1992, an article proclaims the land around the Florida launch pad as being one of the last places humans have not touched. Included in the 140,000 acres of land is a National Park Service and Fish and Wild Life Service:
NASA and the U.S. Air Force are working together to improve future trips of orbit, however, their motives are strictly money based. “To realize the potential for research and commerce in space, America must achieve one imperative, overarching goal-- arrordable access to space” (Aeronautics 6)Though most of the technology studied and tested is not directly related to the environment, there are direct changes towards more efficient fuel. For example, the cleanest and most efficient fuel is liquid oxygen and liquid hydrogen. The exhaust from these types of systems mainly consists of 95 percent water vapor with a 5 percent release of molecular hydrogen. Attempts to achieve cleaner fuel in rockets can be done by replacing original contaminating chemicals with chemicals that are less pollutant when released into the atmosphere. Scientists have come up with a way to replace ammonium perchlorate, oxidizer, with ammonium nitrate. The end result will be less of the hydrogen chloride release into the atmosphere, which damages the ozone. Although this example does not totally eliminate the dangerous toxins present in exhaust plumes, it is certainly a step in the right direction.
Future ships which would include the hydrogen, oxygen liquid fuel and other possible ways of propulsion are currently under study. NASA has developed the Delta Clipper, DC-X, Experimental Rocket. This rocket stores its fuel inside the rocket itself and requires no external tank or boosters. The designs are being drawn with the weight in mind to lower the amount of fuel consumed by the four engines. “New lightweight materials promise to keep the structure proportion of a rockets take off weight low enough so that the craft may be able to lift a payload with only a single stage” (Brown 52). A major issue that NASA mentions with this design is its cut back in the cost of launch-- from $10,000 to $1,000 per pound; currently it cost $10,000/ lb. to launch satellites or experiments. Other technologies of propulsion have been found by long forgotten scientists which may open the doors to superior fuels and systems of engines, such as the German scientist, Eugine Sauger, who, in 1950, developed the matter-antimatter propulsion that is so loved on the Star Trek series and movies. This thought is not all fantasy, but it contains real scientific theories that can theoretically be carried out.
Many other countries use the liquid hydrogen/liquid oxygen as the main fuel and have no reported problems with lack of boost. For now, this seems the best way to propel the latest spy and communication satellites into low earth orbit. As technologies advance and cost of space flight is reduced, this just might be attractive enough for the government to invest money into and support a mission that will have almost no harmful environmental effect on Earth. Unfortunately, until the offer is enticing enough for the government to accept, the natural habitat around Kennedy Space Center has to put up the mutation, destruction and death that the innocent looking, thick, white clouds envelope it with.
Mallove, Eugene, and Matloff, Gregory. The Starflight Handbook: A Pioneer’s Guide to Interstellar Travel. New York : Stephen Kippur, 1989.
“NASA Statement Concerning Space Shuttle SRB Exhaust Effects On Ozone” http://spacelink.msfc.gov/NASA.News Releases/93-11-01: n. pag. Online. Internet. 3 April 1997
“Propellants” http://space link.msfc. nasa.gov: N. page. Online. Internet. 22 March 1997
United States. National Aeronautics and Space Adminstration. Aeronautics and Space Transportation Technology: Three Pillars for Sucess. Washington: 1997
Varnes, Mitch, “A Walk on the Beach at KSC.” NASA Magazine Spring (1992) : 26-29
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