The Space Shuttle: Roles, Missions, and Accomplishments - Essay Example

Space Shuttle Introduction: The space shuttles are true aerospace vehicles. They exit earth and its atmosphere under rocket power provided which has three liquid-fueled main engines and two solid-fuel boosters attached to an external liquid fuel tank. After their missions in orbit end, the shuttles streak back through the atmosphere and are maneuvered to land like an airplane. But the shuttles without power are more likely to land like a glide on runways. Unlike other rockets which can place heavy payloads into space only once, these space shuttles are designed to be used 100 times. 2. History: In October 1968 NASA had already had began its initial study of space shuttle which is before the Apollo landing the moon in 1969. So in 1969 the Space Task Group was formed by President Richard M. Nixon and vice president Spiro T. Agnew. They presented their objective after evaluating the previous studies related to shuttle science. First, to have a national space strategy and second, to build a space shuttle. The big question took place while the earliest development of space shuttle, the debate was about the optimal shuttle design with the purpose of best balanced capability, development cost and operating cost. Eventually the already existing design was selected, using a reusable winged orbiter, solid rocket boosters, and expendable external tank. The Shuttle program was officially commenced on January 5, 1972, just after the announcement that NASA would precede with the development of a reusable Space Shuttle system by President Nixon. The final design was less pricey to manufacture and less technically striving as compared to the earlier fully reusable designs. When the Apollo space program was about to finish, NASA officials were looking at the big picture of the American space program. They used one-shot, disposable rockets. All they wanted is a cost effective, reliable rocket and something which is reusable. This main idea of space shuttle being reusable was that it could launch like a real rocket but land like an airplane which would be considered as one of the greatest technical achievement. 3. NASA Research: As soon as NASA began to study the designing, expenditure and engineering of a space shuttle there were many aero spaces companies which also started to explore these concepts. President Nixon in 1972 announced that NASA would develop a reusable space shuttle or space transportation system (STS). Later it was decided that the shuttle would consist of an orbiter directly attached to the solid rocket boosters and also an external fuel tank. It was awarded the prime contract to Rockwell International. Then, spacecraft which were made used ablative heat shields that would burn away as the spacecraft re-entered the Earth's atmosphere. Where as, if the rocket is to be reusable it has to use the different strategy. So the designers and manufacturer of the space shuttle suggested an idea which was to use many insulating ceramic tiles to cover the space shuttle which could absorb the heat of re-entering without hurting the astronauts. As the shuttle was to fly like a plane (more like a glider), while landing. So a working orbiter was also built up for testing the aerodynamic design, but it won't go into the outer space. This orbiter was named the Enterprise afterwards it was known as the "Star Trek" starship. So this required test flights which Enterprise took care of the numerous test flights and landings, where it was launched from a Boeing 747 and glided to a landing at Edwards Air Force Base in California. At last, after many years of constructing and testing of orbiters, main engines, external fuel tanks and solid rocket boosters, the shuttle was ready to fly. There were total four shuttles made - Columbia, Discovery, Atlantis and Challenger. The first flight was of Columbia Space Shuttle in 1981, piloted by astronauts John Young and Robert Crippen. It was the successful flight which Columbia performed and later other shuttles made several successful flights. But there was a mishap in 1986, the shuttle Challenger exploded inside the flight and the entire crew was lost. After this incident NASA suspended the shuttle program for many years, while the reasons for the disaster were investigated thoroughly and corrected. So after several years, the new improved space shuttle flew again and a new shuttle, Endeavour, was built to replace Challenger in the shuttle fleet. Later in 2003, when the shuttle was re-entering the Earth's atmosphere, the shuttle Columbia was break over the United States. NASA again shut down the space shuttle program after this accident and worked feverishly in making changes and returning the shuttles to the flights. Again in 2006, the shuttle Discovery faced lost foam from in its external fuel tank. The program was again grounded and scientists struggled to solve this problem. In 2006 the Discovery was launched twice, in July and again in December. According to NASA, the July 2006 launch was the most photographed shuttle mission in the history. The Atlantis launched in September 2006, after delays due to weather, a problem with the fuel cell and a faulty sensor reading. While the space shuttles are known as the great technological advancement, they are limited to the payload they can take into orbit. These shuttles are not the heavy lift vehicles as compared to the Saturn V or the Delta rockets. The shuttles are not able to go to high altitudes orbits or escape the Earth's gravitational field to travel to the Moon or Mars. So now NASA is currently working to explore new concepts for launching new vehicles that are capable of going to the Moon and Mars. 4. Advantages and disadvantage of Space Shuttles: The foremost advantage of space shuttle is that we are broadening the horizon of space science, while one major disadvantage is the use of enormous amount of resources, energy and money which are used to travel in the space. To make sure that the operating system is able to handle extreme conditions in routine is another difficult thing as there is only a thin thread which holds the astronaut away from death. For example Apollo 13 was the shakiest survival in the space also showing the will of human and ingenuity to overcome all the challenges. 4.1 Shuttle Launch Systems Problems In Terms Of Safety: i. Positioning: the position of the spacecraft was lateral, beside the main LOX/LH2 tank and solid rocket boosters. In the case of any major explosion in the tank or booster, the Shuttle crew practically had no chance of survival. This had actually caused the loss of life in 1986 Challenger. ii. Engine Installation: Thethree main LOX/LH2 SSME engines were directly installed into the Shuttle which had the possibility of a fatal disaster in both the cases, the engine or fuel turbine explosion. In addition to this particular configuration the result was tremendous vibrations in the working engines which were directly transferred to the structure of the Shuttle, its systems and crew compartment. These vibrations greatly contribute to material fatigue of the structure and increase the possibility of the loss of some of its crucial belly tiles. Moreover, if the main engines are operating at chamber temperatures of thousands of degrees centigrade for about 480 seconds, while the feed pipes supplying LOX/LH2 to the engines it does have extremely low negative temperature. This means that the Shuttle must be able to survive the major temperature stress to its structure and systems with potentially negative consequences. iii. The three SSMEengines: they have a combined thrust of almost 700,000 kgf (7 times higher than the weight of the Shuttle). This thrust must be transmitted through the Shuttle structure to the LOX/LH2 tank, because from a mechanical point of view, the Shuttle is carrying a huge fuel tank on its belly and not vice versa. It means that immense stress on the Shuttle structure from the SSME engines during launch creates elastic deformations including deformation of its belly, again increasing the possibility of tile detachment. It also means that the structure of the Shuttle must be much more rigid and heavy than if the launch system was carrying the Shuttle. This weight factor, combined with the mass of three SSME engines enhances the stress to the structure during re-entry. Nevertheless, the main problems during re-entry could well be caused by the immense load on the Shuttle structure that occurs during its launch into orbit. 1. The lateral positionof the Shuttle during launch enables pieces of debris or ice from the external tank to impact the Shuttle, possibly with very serious consequences. 2. It is difficultto stop solid rocket boosters after ignition and therefore it is difficult to affect launch abort in the critical phase after ignition of engines and before liftoff. As this shuttle program has been the most costly program in the history of space. In spite of huge investments for the improvements and up gradation for the safety, it is still the most dangerous and also ineffective for the intended missions - named as space science and construction of the Space Station - is now on hold. It also has had its successes - which includes all the Hubble repairs in 1993, 1997 and 1999 and also the dozens of successful placements of important military and communications satellites. In 2003 NASA had also stopped defending the shuttle as nobody was convinced to pay more on this multi millionaire mission and on an antique vehicle. First Challenger and then Columbia accidents have placed a dark shadow on the whole program. 4. Conditions and Fuel System of Space Shuttle: Following are the description of five space shuttles, their history and their modifications. The condition of every shuttle while entering and exiting the space orbital and the fuel system is also discussed. i. Enterprise (OV-101) Background Enterprise, the first Space Shuttle Orbiter, was originally to be named Constitution (in honor of the U.S. Constitution's Bicentennial). Designated, OV-101, the vehicle was rolled out of Rockwell's Air Force Plant 42, Site 1 Palmdale California assembly facility on Sept. 17, 1976. On Jan. 31, 1977, it was transported 36 miles overland from Rockwell's assembly facility to NASA's Dryden Flight Research Facility at Edwards Air Force Base for the approach and landing test program. The nine-month-long ALT program was conducted and demonstrated that the orbiter could fly in the atmosphere and land like an airplane, except without power-gliding flight. The ALT program involved ground tests and flight tests. A ground test of orbiter systems followed the unmanned captive tests. All orbiter systems were activated as they would be in atmospheric flight. This was the final preparation for the manned captive flight phase. The Enterprise was built as a test vehicle and is not equipped for space flight. On Nov. 18, 1985, Enterprise was ferried from the Kennedy Space Center to Dulles Airport, Washington, D.C., and became the property of the Smithsonian Institution. In the day-to-day world of Shuttle operations and processing, Space Shuttle orbiters go by a more prosaic designation. Enterprise is commonly refered to as OV-101, for Orbiter Vehicle-101. Following in the Enterprise's, the orbiter Columbia was created and it became the first Space Shuttle to fly into Earth orbit in 1981. Four sister ships joined the fleet over the next 10 years: Challenger, arriving in 1982 but destroyed four years later; Discovery, 1983; Atlantis, 1985; and Endeavour, built as a replacement for Challenger, 1991. ii. Columbia (OV-102) Background Columbia, the oldest orbiter in the Shuttle fleet, is named after the Boston, Massachusetts based sloop captained by American Robert Gray. On May 11, 1792, Gray and his crew maneuvered the Columbia past the dangerous sandbar at the mouth of a river extending more than 1,000 miles through what is today south-eastern British Columbia, Canada, and the Washington-Oregon border. Gray also led Columbia and its crew on the first American circumnavigation of the globe, carrying a cargo of otter skins to Canton, China, and then returning to Boston. The spaceship Columbia is the first Space Shuttle to fly into Earth orbit in 1981. A test vehicle, the Enterprise, was used for suborbital approach and landing tests and did not fly in space. In the day-to-day world of Shuttle operations and processing, Space Shuttle orbiters go by a more prosaic designation. Columbia is commonly refered to as OV-102, for Orbiter Vehicle-102. Empty Weight was 158,289 lbs at rollout and 178,000 lbs with main engines installed. Upgrades and Features Columbia was the first on-line orbiter to undergo the scheduled inspection and retrofit program. It was transported August 10, 1991, after its completion of mission STS-40, to prime Shuttle contractor Rockwell International's Palmdale, California assembly plant. The oldest orbiter in the fleet underwent approximately 50 modifications, including the addition of carbon brakes, drag chute, improved nose wheel steering, removal of development flight instrumentation and an enhancement of its thermal protection system. The orbiter returned to KSC February 9, 1992 to begin processing for mission STS-50 in June of that year. iii. Discovery (OV-103) Background Discovery, the third orbiter to become operational at Kennedy Space Center, was named after one of two ships that were used by the British explorer James Cook in the 1770s during voyages in the South Pacific that led to the discovery of the Hawaiian Islands. Cook also used Discovery to explore the coasts of southern Alaska and northwestern Canada. During the American Revolutionary War, Benjamin Franklin made a safe conduct request for the British vessel because of the scientific importance of its research. In the day-to-day world of Shuttle operations and processing, Space Shuttle orbiters go by a more prosaic designation. Discovery is commonly refered to as OV-103, for Orbiter Vehicle-103. Empty Weight was 151,419 lbs at rollout and 171,000 lbs with main engines installed. Upgrades and Features Discovery benefited from lessons learned in the construction and testing of Enterprise, Columbia and Challenger. At rollout, its weight was some 6,870 pounds less than Columbia. Two orbiters, Challenger and Discovery, were modified at KSC to enable them to carry the Centaur upper stage in the payload bay. These modifications included extra plumbing to load and vent Centaur's cryogenic (L02/LH2) propellants (other IUS/PAM upper stages use solid propellants), and controls on the aft flight deck for loading and monitoring the Centaur stage. No Centaur flight was ever flown and after the loss of Challenger it was decided that the risk was too great to launch a shuttle with a fueled Centaur upper stage in the payload bay. iv. Atlantis (OV-104) Background Atlantis, the fourth orbiter to become operational at Kennedy Space Center, was named after the primary research vessel for the Woods Hole Oceanographic Institute in Massachusetts from 1930 to 1966. The two-masted, 460-ton ketch was the first U.S. vessel to be used for oceanographic research. Such research was considered to be one of the last bastions of the sailing vessel as stream-and-diesel-powered vessels dominated the waterways. The steel-hulled ocean research ship was approximately 140 feet long and 29 feet wide to add to her stability. The research personnel worked in two onboard laboratories, examining water samples and marine life brought to the surface by two large winches. The water samples taken at different depths varied in temperature, providing clues to the flow of ocean currents. The crew also used the first electronic sounding devices to map the ocean floor. In the day-to-day world of Shuttle operations and processing, Space Shuttle orbiters go by a more prosaic designation. Atlantis is commonly referred to as OV-104, for Orbiter Vehicle-104. Empty Weight was 151,315 lbs at rollout and 171,000 lbs with main engines installed. Upgrades and Features Atlantis benefited from lessons learned previously and at rollout, its weight was some 6,974 pounds less than Columbia. The experience gained during the Orbiter assembly process also enabled Atlantis to be completed with a 49.5 percent reduction in man hours (compared to Columbia). Much of this decrease can be attributed to the greater use of thermal protection blankets on the upper orbiter body instead of tiles. During the construction of Discovery and Atlantis, NASA opted to have the various contractors to manufacture a set of 'structural spares' to facilitate the repair of an Orbiter if one was damaged during an accident. This contract was valued at $389 million and consisted of a spare aft-fuselage, mid-fuselage, forward fuselage halves, vertical tail and rudder, wings, elevons and a body flap. The modifications include a drag chute, new plumbing lines that configure the orbiter for extended duration, more than 800 new heat protection tiles and blankets and new insulation for the main landing gear doors, structural mods to the Atlantis airframe. Altogether, 165 modifications were made to Atlantis over the 20 months it spent in Palmdale, California. v. Challenger (STA-099, OV-99) Background Challenger, the second orbiter to become operational at Kennedy Space Center, was named after an American Naval research vessel that sailed the Atlantic and Pacific oceans during the 1870's. Challenger joined NASA fleet of reusable winged spaceships in July 1982. It flew nine successful Space Shuttle missions. On January 28, 1986, the Challenger and its seven-member crew were lost 73 seconds after launch when a booster failure resulted in the breakup of the vehicle. Challenger started out as a high-fidelity structural test article (STA-099). The orbiter structure had evolved under such weight-saving pressure that virtually all components of the air frame were required to handle significant structural stress. With such an optimized design, the only safe approach was to submit the structural test article to intensive testing and analysis. STA-099 underwent 11 months of intensive vibration testing in a 43 ton steel rig built especially for the Space Shuttle Test Program. The rig consisted of 256 hydraulic jacks, distributed over 836 load application points. Under computer control, it was possible to simulate the expected stress levels of launch, ascent, on-orbit, reentry and landing. Three 1 million pound-force hydraulic cylinders were used to simulate the thrust from the Space Shuttle Main Engines. Heating and thermal simulations were also done. STA-099 was returned to Rockwell on 11/7/79 and it's conversion into a fully rated Orbiter Vehicle was started but it still involved a major disassembly of the vehicle. Challenger had been built with a simulated crew module and the forward fuselage halves had to be separated to gain access to the crew module. Additionally, the wings were modified and reinforced to incorporate the results of structural testing and two heads-up displays (HUD's) were installed in the cockpit. Empty Weight was 155,400 lbs at rollout and 175,111 lbs with main engines installed. This was about 2,889 pounds lighter than Columbia. Upgrades and Features Two orbiters, Challenger and Discovery, were modified at KSC to enable them to carry the Centaur upper stage in the payload bay. These modifications included extra plumbing to load and vent Centaur's cryogenic (L02/LH2) propellants (other IUS/PAM upper stages use solid propellants), and controls on the aft flight deck for loading and monitoring the Centaur stage. No Centaur flight was ever flown and after the loss of Challenger it was decided that the risk was too great to launch a shuttle with a fueled Centaur upper stage in the payload bay. 5. Recent Modification and Future of Space Shuttle NASA is continuously working on the up gradation of space shuttle whether the program is grounded or not. Recently it has tried lifting a freeze on improving the design of its four operating space shuttles, earmarkingabout hundred million dollars each year for making minor modifications and studying large-scale changes that might be needed in the future. Under NASA's plans, design changes that improve shuttle safety and provide support for missions to the international space station are the highest priority. Modifications that would replace obsolete shuttle systems would be undertaken next, followed by changes to enhance capabilities if the vehicles are needed for future missions. The committee was asked to evaluate several of NASA's proposed design changes for updating parts and enhancing shuttle capabilities, including some that only would be needed if shuttle use is extended beyond 2012. Examples are: i. Substituting hydraulic power units with modern electrical systems.NASA is studying ways to replace auxiliary power units, which use toxic propellants, with electrical systems that would be safer and easier to maintain. ii. Developing long-lasting fuel cells.Shuttle fuel cells provide electricity and water for the crew. NASA is considering replacing alkaline fuel cells with proton exchange membrane cells, which last longer and are more powerful and less toxic to the environment. However, developing these fuel cells will be expensive. iii. Modifying shuttle radiators and wings to strengthen protection against tiny meteoroids and orbital debris.Although these upgrades will be completed next year, the shuttles still will continue to be at risk from damage by space debris. Small pieces can cause major harm because they collide with the shuttles at such high speeds. iv. Replacing or updating solid rocket boosters.NASA is considering using either bigger, improved solid rocket boosters or new liquid fly-back boosters designed to return to the launch site for reuse after they separate from the shuttles. Both types of boosters could reduce operational costs and improve performance and long-term safety. However, the costs involved in upgrading solid rocket boosters could exceed $1 billion, and developing liquid fly-back boosters would cost at least $5 billion. 6. Conclusion: There are many missions which are lined up in the year 2009 for example like STS-119 to Launch March 11, Kepler and Expedition 18. STS-119 is the 28th shuttle mission to the International Space Station. Discovery also will carry the S6 truss segment to the orbital outpost. The STS-119 mission will deliver to the station the final set of solar arrays needed to complete the station's complement of electricity-generating solar panels, and through them support the station's expanded crew of six in 2009. Officially NASA says it plans to complete the international space station as close to 2010 as possible and then stop flying the shuttle. Finishing the space station, NASA officials have said, will require 28 shuttle flights spread over six years.The [international space station] was designed to be carried into space and assembled using the space shuttle. The components have already been built, tested and most of them have been integrated and are awaiting launch at Kennedy Space Center. References: Amato, William. The Space Shuttle: Space Shut.The Rosen Publishing Group, 2002 Baker, David & L.B. Taylor, Jr. Space Shuttle. Crown Publishing Group Staff, 1979. Harland, M, David. The Space Shuttle: Roles, Missions, and Accomplishments. London. John Wiley & Sons In., 1998. Harrington,S.Philip & Ressmeyer, Roger. The Space Shuttle: A Photographic History. Browntrout Publishers, 2003. Michael Jay, Michael. Space Shuttle. Hachette Children's Books, 1984 Zuehlke Jeffrey. The Space Shuttle. Lerner Publications, 2007 Upgrading the Space Shuttle. 1999. Aeronautics and Space Engineering Board. National Academy Press. 10th March 2009. http://books.nap.edu/openbook.phprecord_id=6384&page=R1> The space shuttle. 2006.History and components. 10th March 2009.http://www.angelfire.com/nc3/faa2001/shuttle/shuttle.html> The National Academies. 1999. The design modification in the space shuttle. 10th March 2009. Read More