Course: Advanced Aerodynamics
Abstract
Hypersonic aircraft are the future of aviation. But their development present challenges for which aircraft engineers and regulatory agencies have yet to establish solutions. Noise pollution and gas polluants emissions represent a substantial environmental problem. Heat build-up due to skin friction and excessive structural loads are significant problems for structural and materials engineer for an aircraft that must be kept at the minimum possible overall weight. Current aircraft technologies and designs must be reviewed, optimized, and re-engineered to meet physical, functional, technological, and other requirements for hypersonic commercial aircraft.
The successful development of hypersonic commercial aircraft shall lead to considerable decreases in total flight durations. Global air traffic controllers shall see a tremendous increase in the total number of flights to monitor as well as the total number of flight paths to compute. It is imperative that the global aviation system regulatory agencies measure the impact of such increased workload on global air traffic controllers.
Introduction
The philosophical concept of evolution revolves around the general idea that the world and all natural organisms progress from a very basic form to a complex form with continuously evolving abilities and capabilities throughout the process. This concept is particularly true in the field of aircraft design and manufacturing. Aircraft are defined by NASA as transportation devices which are designed to move people and cargo from one place to another (NASA, 2015). Historical records indicate that the first witnessed genuine powered flight of a heavier than-air machine occurred during a cold winter on the 17th of December 1903 in Kitty Hawk, North Carolina (Anderson, 2016, P 1-3). This fostered an engineering and manufacturing revolution for the design of flying vehicles. Humans’ need for faster travel has driven aircraft engineers to continuously conquer the limits of aeronautics. Throughout the years, aircraft development has experienced tremendous growth and technological advancement on a global scale. A testimony to the advancement in aircraft design is NASA’s record-breaking X-43A hypersonic research aircraft. Hypersonic aircraft are the future of aviation. What are the challenges to successfully developing and sustaining commercial hypersonic aircraft?
Multiple organizations, researchers and aircraft manufacturers have completed studies focused on developing hypersonic aircraft. Evaluating the challenges to developing and sustaining hypersonic commercial aircraft requires a system approach. In their research titled “A Review of Design Issues Specific to Hypersonic Flight”, Sziroczak and Smith reports that Noise pollution and gas pollutants emissions represent significant environmental challenges. The aerospace industry contributes 2% of all anthropogenic carbon dioxide emissions (Sziroczak & Smith, 2016). This is also supported by a research study titled “Impact of Hydrogen Fueled Airliners on the O3 Layer Depletion” and written by Ingenito. He reports that hydrogen fueled airliners emissions have a detrimental effect on the ozone layer over the polar region. He also reports that the rate of increase of water vapor is also significant enough to generate a substantial increase of temperature overtime if large number of hypersonic aircraft was to be in service. Other research studies took a more technological approach when reviewing the development of hypersonic aircraft.
In the Textbook “Basics of Aerothermodynamics”, Hirschel compares commercial hypersonic vehicles with spacecraft re-entry vehicles. His work presents the technical distinction between hypersonic vehicles and spacecraft vehicle and demonstrates that hypersonic commercial aircraft can be developed based on the technologies and structures of re-entry vehicles. In the research study titled: “Ramjet Nozzle Analysis for Transport Aircraft Configuration for Sustained Hypersonic Flight”, Baidya and Cooper conclude that a dual bell nozzle was suitable for engine integration in the combined cycle hypersonic propulsion architecture. In the research study titled “Sizing of a Fully Integrated Commercial Airliner”, Ingenito et al. present structural and geometrical configurations as well as aircraft performance characteristic required for a hypersonic aircraft that is capable of reaching Mach 8. It is also important to mention the research of Feir that is titled: “ Evaluation of Routing and Scheduling Considerations for Possible Future Commercial Hypersonic Transport Aircraft”. In the year 1974, he notably presented a forecast into the year 2000 of the global air transportation system's needs and requirements including elements such as aircraft fuel cost, crew cost and maintenance costs. Finally, a system approach is taken by Sziroczak and Smith in their research study titled: “A Review of Design Issues Specific to Hypersonic Flight”. It is a thorough analysis that includes challenges pertaining to the following areas: aviation business and aviation markets, environmental requirements and impacts, aerodynamics characteristics and requirements as well as propulsion systems characteristics and requirements. This research notably discusses hypersonic aircraft not requiring lift forces to balance weight in order to sustain flight. Hypersonic aircraft can rely solely on thrust generated by their engines (Sziroczak & Smith, 2016)
Methodology
Researching the challenges and benefits of developing and sustaining commercial hypersonic aircraft was completed through documentation analysis. The first step was to research relevant textbooks that discuss structural, aerodynamics and propulsion challenges to the development of hypersonic aircraft. The second step was to select a legitimate source of documented research. The third step was to define the criteria for material to be selected. Such criteria were environmental impact, optimization of existing aeronautical and astronautical technologies, optimization of global air transportation systems infrastructures and elements and an evaluation that pertains to the fields of structures, aero-thermodynamics, and propulsion. Per the specified criteria, the following materials were selected: the textbook “Basics of Aerothermodynamics by Hirschel, the research study titled: “ A Review of Design Issues Specific to Hypersonic Flight Vehicles” written by Sziroczak and Smith, the research study titled; “ Impact of Hydrogen Fueled Hypersonic Airliners on the O3 layer depletion” written by Ingenito, the research study titled: “ Ramjet Nozzle Analysis for Transport Aircraft” written by Baidya, Pesyridis and cooper, the research study titled: “ Sizing of a Fully Integrated Hypersonic Commercial Airliner” written Ingenito, Gulli, Bruno, Colemann,Chudoba and Czysz, and the research study titled; “ Evaluation of routing and scheduling considerations for possible future commercial hypersonic transport aircraft” written by Feir.
Determining the effect of commercial hypersonic aircraft on the global environment required an understanding of their impact on the ozone layer.
Determining whether a dual bell nozzle was suitable for use on hypersonic aircraft required a computational fluid dynamics analysis.
Determining physical specifications for a suitable geometry for hypersonic aircraft required a definition of a specific set of criteria which include sizing parameters, mass budget and size breakdown.
Results and Findings
Important results and findings based on the research methodology are displayed below.
Evaluation and Discussion
Evaluating the challenges to a successful development and sustainment of hypersonic commercial aircraft requires a system approach. Noise pollution and gas pollutants emissions represent significant environmental challenges. Table 1 and Table 5 indicate that a small set of just two hundred hypersonic aircraft can deplete the ozone layer by 0.0036% over a period of just a year. At this rate, a successful development of commercial hypersonic aircraft will contribute to accelerating the degradation of the earth ozone layer and global warming. This is supported by Sziroczak and Smith who report that the aerospace industry contributes to 2% of all anthropogenic carbon dioxide emissions (Sziroczak & Smith, 2016). Noise pollution is also reported as one of the most negative environmental impact of aviation. It is a source of community annoyance and sleep disruption. According to the Noise & Health article written in 2017 on aviation noise impact, it even affects children academic performance and increases the risk of cardiovascular diseases for people in communities neighboring airports (Basner, 2017). Aircraft engineers, environmental engineers and the global air transportation system’s regulatory agencies must design methods to eradicate environmental risks presented by the use of hypersonic commercial aircraft.
Current aircraft and spacecraft technologies must be optimized for the development of hypersonic commercial aircraft. Figure 2 and figure 3 show that engine and propulsion systems’ challenges can be overcome by starting with determined elements of supersonic aircraft engine that may be suitable or re-designed for hypersonic flight applications. One of the main challenges with hypersonic commercial aircraft propulsion system is the high amount of power and thrust required to attain such high speed. In fact, Sziroczak and Smith report that hypersonic aircraft do not require lift forces to balance weight in order to sustain flight. Hypersonic aircraft can rely solely on thrust generated by their engines (Sziroczak & Smith, 2016). The power and thrust requirement represent a source for significant vibration forces generated by the engine. These vibration forces may damage the structure of the aircraft and other aircraft subsystems.
Heat build-up due to skin friction and excessive structural loads are a significant problem for structural and material engineers for an aircraft that must be kept at the minimum possible overall weight in order to attain the defined performance characteristics of hypersonic speed. This is supported by Sziroczak and Smith’s research study. In fact, they report in their study that it is vital to keep the vehicle total mass as low as possible (Sziroczak & Smith, 2016). This is a contrast with the need for materials capable of withstanding extremely high heat and resistant to deformation since such materials are often of greater weight than the commonly used aluminum and titanium alloys. Although the progress in the field of composite materials may alleviate some of the challenges faced by hypersonic aircraft engineers, structural designers and aerothermal engineers must overcome a significant challenge in developing a cost effective material capable of withstanding heat that may reach and exceed 3000 degree Celsius based on the defined aircraft performance characteristics. Engineers may opt to start by optimizing heat shield and structural materials of re-entry vehicles but development cost may render this solution obsolete. Figure 4 is an illustration of the structural, geometrical, and sizing challenges that must be met by hypersonic aircraft engineers.
The challenges presented by the development of hypersonic aircraft routes and the impact of hypersonic commercial aircraft on the global air transportation system is better discussed through a research proposal. Decreased flights durations will translate to an increase in the total number of flights that must be monitored and flight paths that must be computed by global air traffic controllers. A within-subjects experimental research design shall be conducted to measure the mental workload or level of fatigue and stress added by hypersonic commercial flights on air traffic controllers. The target population shall be defined as a selected group of three hundred air traffic controllers composed of three to six air traffic controllers from each state. The minimum years of experience of each participant shall be set to three years. One hundred participants shall be selected from each of the following level of experience category : Three to ten years, eleven to twenty years, and twenty-one years to thirty-six years. Two research participants groups shall be created for this study. The first group will complete simulated air traffic control tasks using only typical commercial aircraft flight paths data. The second group will complete simulated air traffic control tasks using both hypersonic commercial aircraft and current commercial aircraft flight path data. The duration of each test shall be set to two hours. Nine hundred aircraft flight paths data shall be available for the first test. It shall be a mixture of short distance flight and long-distance flights. Participants for each group shall be selected randomly from each experience category. An electroencephalogram device shall be used to measure and record brain activity data for each participant during each test. A computerized system which include a duration and quantity measurement software shall be used to measure the following variables for each participant during each test: number of current commercial aircraft and hypersonic flight paths computed, number of current commercial aircraft and hypersonic flight path computed for each flight length category and task completion duration. Group means shall be the research data used to compare differences between each measured group datasets. This type of research will be provided to global regulatory agencies with an estimate of the challenges that an increased number of computed flight paths and air traffic control activities will present to their agencies. This will allow the global air transportation system’ regulatory agencies to design a solution for the air traffic control challenge curve to be flattened.
Conclusion
Engineering commercial aircraft that are capable of reaching hypersonic speed is achievable. An evaluation of the challenges to meeting such an objective requires a system approach. Environmental challenges such as pollutant emissions and noise pollution represent a significant hurdle. Hypersonic aircraft structures also face the challenge of withstanding extreme temperature due to such high speed and skin friction. Sziroczak and Smith report the intriguing concept that hypersonic aircraft do not require lift forces to balance weight in order to sustain flight. Hypersonic aircraft can rely solely on thrust generated by their engines (Sziroczak & Smith, 2016). This means that the power and thrust generation requirement for hypersonic aircraft engines must be balanced between the aircraft needs to sustain flight and the potential damages that vibrations they generate can cause to the structure. The successful development of hypersonic commercial aircraft may also lead to an increase in the workload of global air traffic controllers. It is imperative that the global aviation system regulatory agencies measure the impact of such increased workload on global air traffic controllers.
References
NASA. (2015). Airplane parts and function. Retrieved from https://www.grc.nasa.gov/www/k-
Hirschel, E. (2004). Basics of aerothermodynamics. Retrieved from
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Ingenito, A. (2018). Impact of hydrogen fueled hypersonic airliners on the O3 layer
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Baidya, R., Pesyridis, A., & Cooper, M. (2018). Ramjet nozzle analysis for transport aircraft
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Ingenito, A., Gulli, S., Bruno, C., Colemann, G., Chudoba, B., & Czysz, P. A. (2011). Sizing of a
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