60 Worked Examples: Introductory

Sending humans back to the moon, Mars, and into deep space is a highly ambitious goal that requires overcoming a range of technical and other challenges, including radiation exposure, life support, and the need for food, propulsion systems, habitat, and resource utilization, human performance and health, cost and funding, technological advancements, and mission design and operations. Here is a list of some of the technical and other challenges in sending humans back to the moon, Mars, and into deep space:

• Radiation exposure: Space travel exposes astronauts to high radiation levels, which can cause various health problems, including increased cancer risk, cognitive decline, and cardiovascular disease.
• Life support systems: Providing astronauts with a sustainable, life-supporting environment is a significant challenge, especially during long-duration missions to the moon and Mars.
• Propulsion systems: A significant challenge is to develop reliable, efficient, and safe propulsion systems capable of transporting astronauts and their equipment over large distances.
• Habitat and resource utilization: Providing a suitable habitat for astronauts and utilizing local resources, such as water and minerals, will be critical for long-duration missions.
• Human performance and health: Ensuring the physical and psychological well-being of the astronauts during long-duration missions is a significant challenge.
• Cost and funding: Sending humans back to the moon, Mars, and deep space is costly and resource-intensive, requiring significant funding and political support.
• Technological advancements: Significant technological advancements, including propulsion systems, life support, habitat design, and materials science, will be required to make human space exploration possible.
• Mission design and operations: Planning, designing, and executing complex missions to the moon, Mars, and beyond requires significant expertise and experience in mission operations and logistics.

Why might someone want to apply for a patent? Some people have argued that the process of patenting nearly every development in aviation technology at the beginning of the 20th century, including by the Wright brothers, hindered the advancement of aviation and aeronautical technology worldwide. Discuss this viewpoint.

• A patent is a form of intellectual property that gives the holder exclusive rights to prevent others from making, using, selling, and importing an invention for a specified period, typically 20 years from the filing date. A patent can cover a new product, process, machine, or improvement. Someone might want to apply for a patent to protect their invention and prevent others from using or profiting from it without permission. A patent can also provide the inventor with leverage in negotiations and licensing agreements. Additionally, the holder of a valid patent can bring legal action against anyone who infringes their patent rights.
• The argument that the process of patenting nearly every development in aviation technology at the beginning of the 20th century, including by the Wright brothers, hindered the advancement of aviation and aeronautical technology worldwide is based on the idea that patents can restrict the flow of information and limit the sharing of ideas and innovations. This can slow down technological progress and hinder the development of new and better products. Some argue that this was the case in the early days of aviation, where the pursuit of patents and legal battles between patent holders slowed down the development of the industry.
• However, others argue that patents are necessary to protect inventors’ investment and hard work and that with the protection offered by patents, there would be more incentive for people to pursue innovations. Additionally, the revenue generated by licensing patents can help fund further research and development. The proper balance between protecting intellectual property rights and promoting technological progress is an ongoing discussion.

The development of engine technology was an enabling factor in the development of aviation. However, success depended on the availability of a suitably formulated fuel, i.e., gasoline. Could you discuss this viewpoint?

• In the early days of aviation, aircraft engines relied on low compression ratios and fuel with low octane ratings. These engines used a simple carburetor system that mixed fuel with air before entering the cylinders for combustion. As aviation technology progressed and aircraft engines became more powerful, higher compression ratios were desired to increase efficiency and power output. However, this led to a problem known as detonation, also called knocking or pinging. Detonation occurs when the air-fuel mixture in the combustion chamber ignites too rapidly and unevenly, producing multiple flame fronts that collide and create high-pressure shock waves. This can cause engine damage and a loss of power. As compression ratios increased, the likelihood of detonation also increased.
• To address this issue, researchers focused on developing fuel additives and optimizing fuel chemistry to increase the octane rating. The octane number is a measure of a fuel’s resistance to detonation. The higher the octane number, the more resistant the fuel is to detonation under high compression. One of the earliest solutions to improve gasoline’s octane rating was adding tetraethyl lead, known as lead-tetraethyl or TEL. Lead compounds effectively reduced detonation, allowing for higher compression ratios and increased power output. TEL became widely used as an anti-knock agent in gasoline during the early to mid-20th century.
• However, leaded gasoline raised concerns because of its toxicity and harmful effects on human health and the environment. Over time, regulations were introduced to limit or phase out the use of lead in automotive and aviation fuels. By the late 20th century, most aviation gasoline was produced with reduced lead content or as “low-lead” formulations. In recent years, efforts have been made to reduce or eliminate lead from aviation gasoline. Alternative fuels and additives have been explored, such as unleaded aviation gasoline (UL AVGAS) and alternative hydrocarbon fuels. These fuels are designed to provide high octane ratings without lead or other toxic additives.
• The development of fuel chemistry and the pursuit of higher octane ratings continue to be important in the aviation industry. Advancements in engine technology, including turbocharging and direct fuel injection, have also contributed to improved efficiency and reduced detonation issues. These advancements and ongoing research into alternative fuels aim to address the challenges associated with combustion and compression ratios in aircraft piston engines.

Goal setting is essential to professional development. Write down some of your goals as a future aerospace/aeronautical/astronautical engineer and where you might want to position yourself in the workplace in shorter and longer terms. Consider also the relative advantages to your career in obtaining an advanced degree.

An aerospace/aeronautical/astronautical engineer’s career goals might look like:

Short-term goals:

1. Gain hands-on experience in the aerospace industry by working as an engineer at a large aerospace company or a startup.
2. Develop expertise in a specific area of aerospace engineering, such as propulsion systems or spacecraft design.
3. Attend industry conferences and events to network with other engineers and stay up-to-date on the latest developments in the field.
4. Participate in continuing education courses to expand knowledge and stay current with new technologies and best practices.

Long-term goals:

1. Obtain an advanced degree in aerospace engineering, such as a Master’s or Ph.D., to increase expertise and improve career opportunities.
2. Work on high-profile aerospace projects, such as human spaceflight missions or developing new aircraft technologies.
3. Take a leadership role in an aerospace company, such as a project manager or department head.
4. Contribute to developing new technologies and advancements by conducting research and publishing papers.

Obtaining an advanced degree in aerospace engineering can offer significant advantages to an engineer’s career, including increased expertise, improved job opportunities, and the ability to take on more challenging and high-profile projects. Additionally, advanced degrees can open up opportunities for leadership and research positions, allowing engineers to contribute to the advancement of the field and shape its future.

After WWII, NASA, the US Navy, USAF, and DARPA contributed to developing nearly 60 “X-planes.” Discuss one X-plane of your choice that you think is a milestone in aviation history, and list the contributions it made to aeronautics and/or astronautics.

One X-plane considered a milestone in aviation history is the X-15. The X-15 was a hypersonic rocket-powered aircraft developed in the 1950s by the National Aeronautics and Space Administration (NASA) and the United States Air Force (USAF). Contributions to aeronautics and astronautics made by the X-15 include:

• Development of hypersonic technology: The X-15 was the first aircraft capable of reaching Mach 6 and was a significant step forward in developing hypersonic flight technology.
• Advancement of materials science: The X-15 was one of the first aircraft to use titanium alloys, which paved the way for the development of future aircraft like the SR-71.
• Pioneering of space flight: The X-15 was the first aircraft to reach the edge of space, paving the way for the development of space flight and the space program.
• Advancement of flight control systems: The X-15 was one of the first aircraft to use a fly-by-wire flight control system, a significant step forward.

Engineers often make decisions involving trade-offs between capabilities and cost, although safety is always paramount. But bad things will always happen when decisions are made in an organizational culture emphasizing profits over safety. Discuss this scenario.

• When decisions in an organizational culture prioritize profits over safety, engineers may face pressure to compromise on safety standards to reduce costs or meet deadlines. This situation can lead to inadequate testing, insufficient resources devoted to safety and quality assurance, or the use of subpar materials. In such a scenario, corners may be cut, and critical safety features may be overlooked, leading to increased risks to passengers, crew, and others.
• Moreover, in such a culture, engineers may feel uncomfortable raising safety concerns or may have those concerns ignored, leading to a disregard for potential dangers. Additionally, safety incidents may be covered up or minimized, leading to a false sense of security and an increased risk of future accidents.
• Ultimately, when safety is not prioritized, it can have disastrous consequences. Airline accidents, for example, can result in loss of life, property damage, and significant financial losses. Furthermore, incidents involving commercial aircraft can also have a long-lasting impact on public trust in aviation, which can be challenging to restore.
• Therefore, aerospace organizations need to foster a culture of safety where safety is given the highest priority, and engineers are encouraged to discuss and address safety concerns openly. This better approach includes providing adequate resources, investing in safety research, and promoting transparency and accountability in decision-making processes.

• Improved aerodynamics: Advancements in computational fluid dynamics and aerodynamics continue to lead to more efficient wings and aircraft designs. Transonic wing shapes, for example, continue to be refined and optimized to increase the cruise Mach numbers of commercial jet airliners. Winglets, which have seen many incarnations, reduce drag and improve fuel efficiency, although it is still being determined how much more winglets can be aerodynamically refined. Laminar flow and morphing wings continue to be more ambitious goals for production aircraft but are worthy of foundational research.
• Advanced composite materials: These materials, such as glass and carbon fiber reinforced composites, have led to lighter and more fuel-efficient aircraft. For example, Boeing’s 787 Dreamliner and the Airbus A350 have airframes made primarily of composite materials. Such materials have a higher strength-to-weight ratio, reducing empty airframe weight, increasing overall aerodynamic and fuel efficiency, increasing useful load (fuel, cargo, and passengers), and lowering operating costs.
• 3D printing: Additive manufacturing or “3D printing” continues to create complex aerospace components that would otherwise be difficult or impossible to manufacture using traditional tooling and methods. 3D printing technology has seen limited use for production (i.e., FAA/PMA certified) parts. However, further developments in techniques and materials will reduce production time while allowing innovative designs to improve efficiency and reduce costs.
• Reusable launch systems: The development of reusable space vehicle technology, such as SpaceX’s Falcon 9 and Falcon Heavy, has significantly reduced the cost of launching payloads into space. Reusing the first stage of a rocket, for example, reuses the stage itself and the rocket engines and can cut at least 10% off the cost of a launch.
• Autonomous systems: Integrating autonomous systems and artificial intelligence in aerospace has improved safety and efficiency in commercial and military applications. Uncrewed aerial vehicles (UAVs) are just one example.
• Electric propulsion: Electric and hybrid-electric propulsion systems continue to gain attention from the aerospace industry. NASA and Boeing have been working on electric aircraft, and many startup companies have developed electric vertical takeoff and landing (eVTOL) aircraft for applications such as urban aerial mobility (UAM). The use of electric propulsion systems for aircraft other than small drones continues to be hindered by the relatively low energy density that can be stored in batteries.
• “Green” aviation: The aerospace industry continues to invest in research to reduce its environmental footprint, especially in Europe. This work includes developing fuel-efficient engines, exploring alternative fuels, and improving air traffic management to give more direct routings and reduce landing delays, which can significantly reduce emissions.
• Space exploration: Recent spacecraft and space exploration technology developments, such as the Mars rovers and the James Webb Space Telescope, have expanded our understanding of the universe. While space telescopes tell us much about the universe, they also reaffirm Earth’s small place in the vast cosmic arena and the enormous distances between planets, solar systems, and galaxies.

List some key considerations in designing, building, and fielding uncrewed aerial vehicles (UAVs) for various civil and military applications, including surveillance, delivery, and scientific research.

Considerations may include:

• Mission objectives: Clearly define the mission objectives, whether surveillance, scientific research, or another purpose, and ensure that the UAV design aligns with these goals.
• Payload requirements: Determine the capacity and type of UAV (or drone) needed for the specific mission, such as cameras, sensors, cargo, or scientific instruments.
• Endurance and/or range: Assess the required flight endurance and operational range to meet mission objectives. Longer endurance will require more fuel or battery capacity, so prepare to reduce the payload capacity.
• Size & weight: Consider size and weight constraints, especially for applications like delivery drones where compactness and weight limitations are critical.
• Propulsion system: Based on the UAV’s mission profile and estimated energy requirements, choose an appropriate propulsion system, such as electric motors, internal combustion engines, or hybrid systems.
• Autonomous operation: Implement robust autonomous navigation and control systems to ensure safe and reliable UAV operation, even in complex environments.
• Redundancy & safety features: Include redundancy in critical systems and safety features like fail-safes, emergency landing capabilities, and collision avoidance systems.
• Regulatory compliance: Ensure compliance with relevant civil aviation or military regulations, including airspace restrictions, licensing, and registration requirements.
• Security: Implement security measures to protect the UAV from unauthorized access, hacking, and data breaches, especially in military applications.
• Environmental considerations: Evaluate the environmental impact of UAV operations, including noise pollution and emissions, and take steps to minimize these effects.
• Payload integration: Ensure the payload is integrated securely and can operate effectively without interfering with the UAV’s flight characteristics.
• Maintenance & reliability: Plan routine maintenance and ensure the UAV is designed for reliability and ease of repair to minimize downtime.
• Integration with existing systems: Ensure the UAV can integrate with existing infrastructure and systems, such as ground control stations or logistics networks for delivery drones.
• Regulatory considerations: Be aware of the regulatory use of UAVs in different civil applications.
• Risk assessment & mitigation: Conduct thorough risk assessments and develop mitigation strategies to address potential hazards and operational risks associated with UAV missions.

What are the critical environmental considerations in the field of aerospace engineering? How might the industry work to reduce its long-term impact on the environment?

The aerospace industry has made some progress in addressing these environmental concerns. However, further effort is necessary to mitigate its long-term environmental impact while meeting the growing aviation and space flight demand.

• Sustainability: Sustainable aerospace engineering practices are critical to ensuring a more “eco-friendly” future for the industry.
• Emissions: Aircraft engines emit greenhouse gases (GHGs), including carbon dioxide (CO₂) and nitrogen oxides (NO_x), which contribute to climate change and air pollution.
• Noise pollution: Aircraft noise can disrupt communities near airports and affect residents’ health and well-being. People are generally very intolerant of aircraft noise.
• Resources: Aerospace manufacturing and operations require significant energy, materials, and water resources. Renewable energy resources such as solar and wind are becoming increasingly essential.
• Waste: The aerospace industry generates a lot of waste, including manufacturing waste and end-of-life aircraft components. While metals can be recycled, some materials, especially composite materials, and their associated resins and other chemicals, can be challenging to dispose of sustainably.

To reduce the long-term environmental impact of aerospace manufacturing, the industry may be able to take several actions, including:

• Research & development: Invest in research and development of more fuel-efficient aircraft designs, propulsion technologies (e.g., electric or hybrid propulsion), and lightweight materials to reduce emissions and resource use.
• Alternative fuels: To lower GHG emissions, develop sustainable aviation fuels (SAFs) from renewable sources like biomass or synthetic processes.
• Advanced aerodynamics: Optimize aircraft aerodynamics to reduce drag and improve fuel efficiency. Technologies such as winglets and laminar flow control can help achieve this goal.
• Noise reduction: Innovate to reduce aircraft noise through quieter engine designs, better aerodynamics, and flight procedures. Implement noise abatement measures near airports.
• Improved air traffic management: Develop and deploy advanced air traffic management systems to optimize flight paths and reduce fuel consumption.
• Eco-friendly manufacturing: Adopt sustainable manufacturing practices, including recycling and reusing materials, and minimize waste generation during production.
• End-of-life recycling: Implement recycling and disposal strategies for aircraft components at the end of their operational lives.
• Regulatory compliance: Ensure compliance with environmental regulations and work with regulatory authorities to establish and enforce emissions and noise standards.
• Investments in green technologies: Make investments in “green” aviation technologies and sustainable practices. Foster collaboration among research institutions and government agencies to accelerate the development and adoption of eco-friendly technologies.
• Environmental certification: Strive for environmental certifications of aerospace facilities to ensure a commitment to sustainability.