Conquering Gravity and Space Vehicles - Essay Example

Space Vehicles Introduction Flying had always been a long time dream of man and research had been carried out in order to conquer gravity. Many of the attempts were partially successful whereas many were not. However, the 1890’s provided a wide open field for the study of aviation, which encouraged endless possibilities to explore and investigate. Two geniuses Orville and Wilbur Wright had a real passion to fly and spent years of laborious work of aeronautical research and experimentation. They soon tasted the fruits of their hard labor in 1903, when they constructed their first successful powered airplane. They used a very unique strategy and approach to create the flight of their dreams. The method they followed was evaluating the data they had gathered by testing their aircraft in flight and then fine – tuning or refining the design based on their results. The construction of aircraft has traveled a long way since then, but still all successful airplanes incorporate the basic elements of the 1903 Wright Flyer design. *The Wright brothers gave us a tool, but it was up to individuals and nations to put it to use, and use it we have. Robert Goddard (1882-1945) The American scientist, Doctor Robert Hutchings Goddard is considered as one of the three most prominent and famous pioneers in the field of rocketry and spaceflight theory. In fact he is better known as the “Father of Modern Rocket Propulsion. In 1909, he seriously worked on rocket development and was credited with launching the first liquid propellant in the world in 1926. During World War I, Goddard built many small military rockets that were used as weapons. Goddard used double- base powder (40 percent nitroglycerin, 60 percent nitrocellulose) instead of black powder (gun powder) and thereby invented a much greater and potent propulsion charge that he used for his rockets. .In fact Goddard’s rocket served to be the forerunner of the bazooka that was created in World War II. Many of the technologies that he had developed and patented were used later on bigger rockets and missiles that included gyroscopically controlled vanes, (1932, New Mexico); a variable-thrust rocket motor, and film cooling. In all over 70 patents were granted to him. On May 1st 1959, the NASA's Goddard Space Flight Center, Greenbelt, Md., was established, in the honor and memory of the brilliant and genius scientist. *Wernher von Braun (1912–1977) One of the greatest champions of space explorations and rocket developers during the period between the 1930s and the 1970s was Wernher von Braun (1912 – 1977) From a very young age he was exposed to the science fiction writings of Jules Verne and H.G Wells and the science fact writings of Hermann Oberth and hence he became increasingly interested in the physics of rocketry. Because of his keen interest in space flight, he involved himself in the German Rocket Society called the Verein fur Raumschiffarht (VfR) in 1929. Von Braun became the brain child and leader of the “rocket team” which had built the V–2 ballistic missile for the German Nazis which they used in World War II. The V – 2 was a liquid propellant missile, 46 feet in length and weighed around 27,000 pounds. This missile flew at a speed exceeding 3,500 miles per hour and directed a 2,200 pound warhead at a target that was about 500 miles away. When it became obvious to Von Braun that Germany could not win the war, he together with 500 of his top rocket scientists surrendered themselves along with all their plans and test vehicles to the side of the Americans. Braun and his team worked for the American army for 15 years developing ballistic missiles for them. Braun became the director of NASA’s Marshall Space Flight Center, but retired in 1972. Spacecraft Structures and Mechanisms: From Concept to Launch The past provides a foundation for the future; this section provides a glimpse into the past with an eye on the future. The following is an example of early Engineering preparation - From early aircraft design, to reusable rocket boosters. Even though many universities can boast of making contributions to the field of aeronautical science, yet very few universities have managed to maintain their focus on aircraft design as the primary goal in the agenda of their curricula. Cal Poly’s aeronautics education has a constant thread running from its inception in 1927 to the present teaching students with a “learn by doing” philosophy, applying knowledge through hands-on laboratory instruction and realworld design projects. Aeronautics students graduating from Cal Poly have already experienced the rigors and excitement of designing, building, and often flying their concepts long before they begin their careers in the aerospace industry. While this approach to education is not for everyone, it has stood the test of time and has produced notable leaders in the aerospace industry. The Present and the Future The Aeronautical Engineering Department was renamed the Aerospace Engineering Department in the late 1990s in response to a growing need for engineers with experience in space-related subjects. Many programs had renamed themselves “aerospace” in the 1960s and 1970s, but the change was often “in name” only. Cal Poly resisted such a change until the facilities and faculty were in place to offer students a true astronautics experience for an all round education. The all round development came about by helping the students not only in the field of aerospace but a good number of other related subjects. Aerospace Engineering Development - Learn by Doing There are many universities that could boast of contributing to the development of aeronautical science, but few universities have maintained their focus on aircraft design as the key feature of their curricula. Cal Poly, a very reputed and well known aeronautics educational establishment was founded in the year 1927. Ever since it’s inception, they have adopted a teaching method that incorporates a “learn by doing” philosophy. Students are taught how to apply their knowledge by making use of hands – on- work and training gained through laboratory instruction that help to expose them to real world designing. Much before they even begin their careers in the aerospace industry, Cal Poly students have experienced the excitement as well as the hard rigors of not only designing and building, but also flying some of their own concepts. Though the education at Cal Poly does not suit everyone, yet it has remarkably stood the test of time by producing some of the most notable leaders ever in the aerospace industry. The Cal Poly philosophy of “learning by doing” has proved extremely beneficial for students learning various subjects like music, architecture, engineering or agriculture. It was a person named Myron Angel, a young drop – out from West Point, who had come to San Francisco during the period of the gold rush in 1849 and was the driving force behind the Cal Poly Foundation. Angel’s philosophy was that the institution that he envisioned would “teach the hand as well as the head, so that no young man or young woman will be sent off in the world to earn their living as poorly equipped for the task as I when I landed in San Francisco in 1849.” (Cal Poly, 2001) In 1933, Cal Poly came under the guidance and leadership of Julian A. McPhee who was the Chief of California’s Bureau of Agricultural Education and over the next 33 years, he transformed Cal Poly into a polytechnic institution to be reckoned with and which culminated into the first baccalaureate exercises that were held in 1942. McPhee’s greatest contribution to Cal Poly was it’s “upside down curriculum.” He strongly believed that the student’s learned best, when they were educated within the frame work of their chosen major or profession. This concept had a great influence on the Department of Aerospace Engineering. Cal Poly’s aeronautical program became well established by the year 1927, which centered its energy on the development of aeronautical science which included aerodynamic theory and performance analysis. In the same year Cal Poly initiated other programs in Engineering Mechanics and Aeronautics to boost or enhance their already existing programs such as business, home economics, printing and others. Cal Poly insisted on educating their students with hands - - training by encouraging them to design and build aircrafts and thereby learn the subject of aeronautics. Each year, one or two aircraft are made by the students themselves and all the students are practically trained to carry out repairs and overhauling of different types of engines. (The California Polytechnic Catalogue, 1928) The history of the designing section of the department was kick- started with the wonderful Glenmont Aircraft that was constructed by twenty enthusiastic students. They had named the aircraft after two of their instructors, Glen Warren and Monty Montijo. Describing the aircraft an article states - the excellency of workmanship and the interesting new features of safety and convenience caused much comment.” A two place biplane that was powered by a Kinner engine was designed in 1930 and in 1931, a three – place high wing monoplane called “Marty’s cabin Monoplane” was built and which was very much in appearance to the Curtiss Robin. (Dave Hoover, 1996) Though the students were not allowed to officially fly their creations, but many accounts show that there were “unofficial” flights carried out by the Cal Poly students. Cal Poly expanded its curriculum by including a variety of courses that included aerodynamic laboratories, fabrication departments and facilities for propulsion. The three year course prepared the students to gain a reputed degree and become engineers in the aeronautical industry. Cal Poly was so famous that the well known aviatrix Amelia Earhart flew down her Lockheed Electra to San Luis Obispo for repairs to be carried out by students of Cal Poly. By the year 1942, Cal Poly had helped to graduate about 118 pilots. In 1943, Cal Poly was designated as a Naval Flight Preparatory School by the U.S Navy during the WWII and after the war it became apparent that Cal Poly had to upgrade itself into a full – fledged university. By the 1960’s other courses such as fluid mechanics, chemistry, engineering, stress analysis, electrical engineering, gas dynamics, rocket propulsion and Senior Thesis was added to the curriculum. What made Cal Poly unique was that despite so many changes in the curriculum, still emphasis was laid on construction and designing of aircraft. One more vital aspect of education at Cal Poly was that it encouraged its students towards cooperative education as well as other extra- curricular projects making it a wholesome and enriching experience. During the 80’s and 90’s a large number of students were involved in the Da Vinci project because Cal Poly aimed at winning the Sikorsky Prize that was being given by the American Helicopter Society encouraging the construction of human-powered helicopters. The Present and the Future: In the 1990’s, Cal Poly renamed the Aeronautical Engineering Department as Aerospace Engineering Department. One of the most striking observations of Cal Poly was that even though it had all the modern day state – of – the – art facilities, yet they never lost sight of their goal, which was “learn by doing”. Cal Poly also took part in NASA’s Aeronautics Multidisciplinary Design and Fellowship (AMDAF) program which involved computer based tools that helped design students to take their work to another level that was beyond their reach of their analytical background. For many years, Cal Poly has participated in the AIAA Team Aircraft Design Competition and has won many prizes and accolades. In recent years, it has become a pioneer in the teaching of aircraft design to sophomores. R. M. Cummings and D. Hall (2002) Though Cal Poly has traveled a long way, yet it has never forgotten its roots and the philosophy of “learn by doing” envisioned by Julian McPhee a hundred years ago. Military Aircraft Structures Much of what we have today in commercial aviation and space technology has been the result of military developments. The accelerated knowledge base and demand for bigger, faster, more reliable products have and continue to be realized in times conflict. Modern aircraft designing has to a great extent been influenced by the advancement in Science and Technology. It is these design concepts that act as a driving force for the Military, Air Force and the Navy airframes. The current focus of our research is directed towards the design concept, development of key materials and structures technologies applied to Military aircraft while having a broad outlook on future progress. Historically speaking, though there are claims about the revolutionary design of the military airframe, yet it continues to evolve by using a blend of traditional design along with the latest emerging technology. Military structures adopt or incorporate new technology for the very fact that it has the capacity for potentially improving airframe weight, cost, performance and survivability. Military aircraft have undergone a progressive transition since the 1930’s when they had aluminum alloy stressed skin semimonocoque when they constructed the C-47 (DC-3) Ever since then, military aircraft structures have traveled a long way evolving and reinventing itself. Hoff N (1984) takes us back to 1927 in the United States, when Lockheed constructed the Vega using semimonocoque composite (wood) fuselage with Northrop as its chief designer. However, the structure was said to be too stiff. But in 1930, Wiley Post had won Los Angeles to Chicago National Air Race and opted to make his first solo flight in a Vega. Amelia Earhart was the very first woman to fly solo across the Atlantic in a Vega in 1932. The monocoque (Greek- monos meaning single and French coque meaning shell) Hoff, N.,(1984) was built by a Frenchman called Louis B`echereau in 1912. He constructed the fuselage of the monoplane Le Monocoque Deperdussin by gluing together a mold consisting of three layers of tulip wood, each about 0.06 in. thick. During WWII and right through the post war years, De Havill made use of wood fuselage such as balsa and spruce. However, in 1920 the concept of using the stressed-skin wing structure was credited to Adolph Rohrbach of Rohrbach Metallflugzeugbau, GmBH. Northrop was the first to introduce the riveted aluminum design for the Alpha aircraft. He designed the wing covers in such a way that it reacted to bending, compression and tension loads. This design was also used for the Northrop Delta and Gamma aircraft. Douglas made slight modifications and used it for his DC-1, DC-2, and DC-3. Even today around 1000 DC-3/C-47 produced between 1935 and 1946 are still in use and is now the much preferred design concept. The Northrop’s basic structural concept has been put to good use over the past 60 years. Many of the structures and concepts that developed have been incorporated into the basic Northrop skin/frame structural arrangement. However, one of the most noteworthy exceptions to the rule was the geodetic aircraft that was employed by Vickers Armstrong, Ltd. which was made primarily of Duralumin. This Geodetic structure was described as “immensely strong and could take any amount of punishment from flak and return home again.” Thetford, O (1958) Aircraft structural designing is evolutionary and not revolutionary because there is no one specific technology that has had any significant impact on structures created in the past. Moreover, it is too early in the day to speak of the present developments taking place in the aeronautical field, to say that it would have a profound impact in the future. However, among the present developments, three areas that claim to have great potential for making a revolutionary change to aerospace structures. These include – Multi-functional structures. Simulation -based prototyping. Affordable composite structures. Multi- functional Structures: Multi- functional Structures are still in its infant stage of development and improvements show that it has reduced life-cycle cost and reduced direct operating cost. These Multi-functional structures might possess actuators and sensors which would allow them to alter their mechanical state (position or velocity) and or mechanical characteristics such as stiffness or damping. They are so designed so as to increase aero- and thermal efficiency survivability, lethality, and survivability, in addition to reducing manufacturing cost while maintaining and improving reliability, supportability, and scope for carrying out repairs. Affordable Composite Structures: These are highly advanced and composite structures that facilitate a great degree of integration because their properties such as mechanical, electro- magnetic and thermal are tailorable to suit their actuators, sensors and sub- systems. They are also cost- effective and the use of textile composites can be easily reinforced. The use of textile technology would help to eliminate the problems faced with the skin-to-core adhesive bond. The thickness fibers serve to minimize impact damage. Though tailor- made adaptive structures may not be the future buzz- words, yet it would pave the path for more efficient and affordable airframes in the future. As Wilbur Wright puts it - “It is possible to fly without motors, but not without knowledge and skill. This I conceive to be fortunate, for man, by reason of his greater intellect, can more reasonably hope to equal birds in knowledge, than to equal nature in the perfection of her machinery.” (At the 15th National Space Symposium) Structures: 24/7 Commercial aircraft manufactures rely on support mechanisms to assist airline operators in the day to day operating environment. One example of such a mechanism is Service Engineering, i.e. Structures, Systems and Parts support. Operators of Commercial aircraft (airlines) rely greatly on Original Equipment Manufactures (OEM’s), for all kinds of repair solutions of damage of the aircraft that is much beyond the scope of Structural Repair Manuals. Structures Engineering is staffed to provide repair solutions, usually due to damage sustained by an aircraft structure during standard operations and assist the operator in returning the aircraft once again into service. In most cases these types of repairs are outside the scope of the Structural Repair Manual supplied by the manufacture and in most cases beyond the operator’s engineering expertise. The methodology employed in Spacecraft Structures varies little from the day to day methodology of structures repair requirements. The mechanics of Materials and how these materials are used, the calculated stresses and subsequent interaction associated with bending, torsion, and deflections are taken into account. Smart Structures: Compliant Mechanisms A smart structure may be defined or described as “a non-biological physical structure having a definite purpose, means and imperative to achieve that purpose, and a biological pattern of functioning.” (Spillman, W. B., Jr., Sirkis, J. S., and Gardiner, P. T., (1996) Smart structures are especially used in space, aircraft, and automotive engineering and also for a wide variety of many other different applications. Another very important application of smart structures is shape control directed towards positioning and alignment. For example, they are used in antenna reflectors “to maintain the precise shape of a structure by effecting high-precision corrections to any deviations from the primary configuration of the structure.” Kashiwase, T., Tabata, M., Tsuchiya, K., and Akishita, S., (1991) and Balas, M. J., (1985) A new and novel approach has been introduced, involving static shape control of smart structures. A unique and special category of mechanisms called compliant mechanisms that are powered by a single input actuator is used in this novel approach. The highlight of this key design issue is the synthesis of a significant and suitable compliant mechanism to carry out this task. The approach comprises of a systematic procedure which is presented with the theorist principles of mechanics and kinematics utilizing a structural optimization scheme for the synthesis of such compliant mechanisms. The procedure entails a novel approach in effecting a smooth shape change in the camber of an idealized airfoil structure by making use of a specially synthesized compliant mechanism that is actuated only by a single torque input. These compliant mechanisms have links or joints that are extremely flexible, unlike the traditional mechanisms that are rigidly designed. The aim of this discussion would center around the scope and benefits relating to the proposed approach, where viable simple solutions involving real-scale static shape control applications are provided. The introduction of this novel approach was developed in order to achieve a systematic synthesis by making use of such mechanisms. An example of this would be to achieve desired shape changes in curved beam segments making use of compliant mechanisms. An illustration of this synthesis procedure is shown through an example involving camber shaping of an idealized airfoil. The essential highlight of the proposed approach is that it operates by making use of a simple system that comprises only of an elastic structural frame with only a single input actuator. Any torque generating device could be an input actuator including a conventional electric servomotor. However, this approach is not affected by the stroke limitation involving smart materials as it is in the embedded actuation schemes. Another significant factor in this approach is that it simplifies the necessary control system by bringing down the number of input actuators to just one. In addition to this, since the actuator can be located away from the structure, both the actuators as well as the compliant mechanism can be safeguarded from effects that are undesirable, such as an unstructured environment and exposure to stress concentrations as in the case of embedded actuation schemes. This approach is essentially useful for the camber shaping of wing structures, where it is necessary to enclose the system of actuation completely within the contour of the airfoil, while ensuring that the external surface is smooth for a drag-free performance. Furthermore, by sheer virtue of such compliant mechanisms, this approach inherently remains friction-free, noise free, as well as backlash-free. But there is one nagging shortcoming in this particular approach, and that is that achievable shape changes are only approximations of the exact shape changes that are desired. However, by choosing approximately the design constraints in the optimization, the accuracy of the approximations can still be suitably monitored. In conclusion, I would say, that leaving aside the limitations involved in other approaches, the results of this particular approach proves that it is both suitable and viable for real-scale practical applications. However, to give validation to the proposed approach, before extending it to real-scale applications such as the adaptive VCW, what is required is a much more comprehensive experimental study and analysis on dynamically scaled models. On the Horizon - Morphing Aircraft Structures The following studies provide us with an insight into the process of aircraft designing, in addition to flight criteria specification for morphing aircraft structures. Lockheed Martin through DARPA’s Morphing Aircraft Structures (MAS) program is engaged in developing enabling technologies for expanding the design space and associating flight envelope by making in-flight radical shape changes for various aircraft. An aircraft has the capacity of becoming an in-situ optimized multi-role vehicle through the process of morphing. Lockheed Martin has endeavored to establish various constitutive elements for morphing technology, by using an integrated building block design approach that would help to identify and solve technological issues that may arise. A morphing aircraft is one that is able to utilize innovative actuators, effectors or mechanisms to adapt its state “substantially.” Its purpose is to enhance behavior and performance in addressing multiple environments.” McGowan, A.R., et al., (2002) Prock, Brian C., Weisshaar, Terrence A., and Crossley, William A.,(2002) The Lockhead Martin configuration is a combat vehicle that is unmanned and gives space for evaluating the technologies using the concept of morphing. The concept of morphing comprises of three distinct actuation criteria, each having different requirements, such as given below:- 1. Stream-wise wing folds: This is the first actuation system, the requirements of which are capability of large moment handling with an angular rotation of approximately 130 degrees and also low bandwidth. 2. Drag Reduction: The second actuation takes place when the fold has occurred and the leading edge of the inboard wing section needs to conform with the fuselage in order to reduce drag. 3. Aerodynamic Controls: The third system of actuation involves aerodynamic controls. Both inboard and outboard flaps are required for maneuvering and pitch/yaw stability. Smart actuation technologies have been selected for integrated design development and these technologies are being matured through subcomponent, integrated bench-top, and wind tunnel demonstrations in conjunction with full-scale design studies. Design criteria trade studies have been conducted by using structural finite element based design optimization. These research findings indicate that the specification for critical loads using the concept of morphing is indispensable as it is critical for the folded configuration. Studies conducted on the increased structural design speed and load factor indicate the greatest impact it has on fuselage weight. However, it was discovered that flutter behavior was highly sensitive to actuator stiffness at the folds, and on structural design speeds. Therefore, presupposition of unique criteria for morphed and unmorphed configurations may be indicated more by actuator stiffness than by load capacity. Conclusion The field of aeronautics has undergone drastic changes ever since our forefathers dreamed of flying. In fact, we are enjoying the fruits of their labor. If they were present to see the dramatic changes that have passed the test of time and have given us the opportunity to take wing, they would be proud indeed. From concept to launch provides us the big picture of designing, analyzing, and testing flight structures for space missions. The objectives of learning all about structures help us not only to improve our understanding of how structures behave, but how to design them to be efficient and dependable for space missions, and how to build confidence through good analysis and testing. On the flip side it also teaches how they fail by breaking down and gives us remedies to improve and take it to another level. Emphasis throughout is on understanding the problem and finding good solutions. This particular course is highly interactive and students learn by doing as it is not based essentially only on theory, but focuses more on the practical. Numerous examples, case histories from the instructor’s experience, and class problems drive home the key points and makes learning an exceptionally satisfying experience. The course is aimed at mechanical design engineers, stress analysts, dynamics and loads engineers, test engineers, mechanical systems engineers, and others interested in flying and its related subjects. Bibliography Balas, M. J., (1985) “Optimal Quasi-Static Shape Control for Large Aerospace Antennae,” Journal of Optimization Theory and Applications, Vol. 46, No. 2, pp. 153–170. Cal Poly: (2001) The First Hundred Years, California Polytechnic State University, San Luis Obispo, CA. Cummings R.M and Hall D.,( 2002). “Aircraft Design for sophomores,” AIAA Paper 2002-0958. Dave Hoover, (1996). “More Alumni Memories,” Cal Poly Aeronautical Engineering Newsletter, Spring. Hoff, N., (1984). “Innovationin Aircraft Structures: FiftyYears Ago and Today,” AIAA Paper 84-0840. : Kashiwase, T., Tabata, M., Tsuchiya, K., and Akishita, S., (1991) “Shape Control of Flexible Structures,” Journal of Intelligent Material Systems and Structures, Vol. 2, No. 1, pp. 110–125. Laxminarayana Saggere¤ and Sridhar Kota† (May 1999) Static Shape Control of Smart Structures Using Compliant Mechanisms AIAA JOURNAL Vol. 37, No. 5, University of Michigan, Ann Arbor, Michigan 48109 Love*M.H Zink†, P.S., Stroud R.L. ‡, Bye§ D.R, Chase C., Impact of Actuation Concepts on Morphing Aircraft Structures. Lockheed Martin Aeronautics Company, Ft. Worth, TX-Palmdale, CA McGowan, A.R., et al. (2002) “Recent Results from NASA’s Morphing Project,” SPIE Paper No. 4698-11, 9th International Symposium on Smart Structures and Materials, March 17-21, San Diego, CA. Paul, D¤ Kelly L,† and Venkayya V‡ Evolution of U.S. Military Aircraft Structures Technology, U.S. Air Force Research Laboratory, Wright–Patterson Air Force Base, Ohio 45433-7542 And Thomas Hess§ U.S. Naval Air Systems Command, Patuxent River, MD 20670-1906 Prock, Brian C., Weisshaar, Terrence A., and Crossley, William A., (September 2002), “Morphing Airfoil Shape Change Optimization with Minimum Acutator Energy as an Objective, 9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, 4-6 September 2002, Atlanta, GA. Robert Goddard www.inventors.about.com/od/gstartinventors/a/Robert_Goddard.htm Russell M. Cummings* From Biplanes to Reusable Launch Vehicles: 75 Years of Aircraft Design at Cal Poly, Aerospace Engineering Department California Polytechnic State University San Luis Obispo, CA 93407 Thetford, O (1958) Aircraft of the Royal Air Force 1918–58, Putnam, London, p. 436. The California Polytechnic Catalogue, 1928-1929, California Polytechnic, San Luis Obispo, CA, 1928, p. 22. Werner von Braun www.history.msfc.nasa.gov/vonbraun Read More