What are the different hypersonic propulsion technologies (e.g. Ramjet vs. Scramjet vs. Rotating Detonation vs. rockets)

• The University of Central Florida researchers are building on their technology that could pave the way for hypersonic flight, such as travel from New York to Los Angeles in under 30 minutes.
• The researchers discovered a way to stabilize the detonation needed for hypersonic propulsion by creating a special hypersonic reaction chamber for jet engines.
• They published their latest research in the journal Proceedings of the National Academy of Sciences.
• Hypersonic flight is defined as travel at speeds exceeding Mach 5.
• The system could allow for air travel at speeds of Mach 6 to 17, which is more than 4,600 to 13,000 miles per hour.
• The technology harnesses the power of an oblique detonation wave, which they formed by using an angled ramp inside the reaction chamber to create a detonation-inducing shock wave for propulsion.
• Unlike rotating detonation waves that spin, oblique detonation waves are stationary and stabilized.
• The technology improves jet propulsion engine efficiency so that more power is generated while using less fuel than traditional propulsion engines, thus lightening the fuel load and reducing costs and emissions.
• In addition to faster air travel, the technology could also be used in rockets for space missions to make them lighter by requiring less fuel, travel farther and burn more cleanly.
• Detonation propulsion systems have been studied for more than half a century but had not been successful due to the chemical propellants used or the ways they were mixed.
• Previous work by Ahmed’s group overcame this problem by carefully balancing the rate of the propellants hydrogen and oxygen released into the engine to create the first experimental evidence of a rotating detonation.
• However, the short duration of the detonation, often occurring for only micro or milliseconds, makes them difficult to study and impractical for use.
• UCF researchers were able to sustain the duration of a detonation wave for three seconds by creating a new hypersonic reaction chamber, known as a hypersonic high-enthalpy reaction, or HyperREACT, facility.
• The facility contains a chamber with a 30-degree angle ramp near the propellent mixing chamber that stabilizes the oblique detonation wave.
• This is the first time a detonation has been shown to be stabilized experimentally.
• Gabriel Goodwin, an aerospace engineer with the Naval Research Laboratory’s Naval Center for Space Technology and study co-author, says their research is helping to answer many of the fundamental questions that surround oblique detonation wave engines.
• Studies such as this one are crucial to advancing

• The Cheetah Hypersonic Missile is a scramjet powered maneuvering anti-ship hypersonic cruise missile that can be launched by land, air, and sea.
• Similar to the Zircon Missile, the Cheetah is capable of reaching speeds of Mach 8 and has a range of 700 km with an estimated cost of $1.1 million per missile.
• The engine used is Scramjet and the propellant is liquid.
• The missile’s operational range is 700 km and its flight altitude is 28 km (17 mi).
• Developed by the Ukrainian defense industry, the project is a massive undertaking and is only just being finalized by the military powerhouses of the world.
• The Ukrainian Ministry of Defense is coordinating with five local companies, namely Ivchenko Progress, Yuzhnoye Design Office, A.M. Makarov, Pivdenne Design, and Artem Holding Company, to maximize expertise.
• The Ministry of Defense is also looking for trustworthy partners abroad, such as Poland and the United States, for the project, to ease technological obstacles and speed up its development.
• The project may result in the missile’s entry into serial production in 2032 if developed alone. This timeline could be moved up to 2029 if assisted by foreign partners.
• A comment on the page asks the extent of US involvement in the project, particularly in developing hypersonic propulsion capabilities and advanced systems needed for a maneuverable rocket that are not currently within Ukraine’s grasp.
• A response to the comment suggests that Northrop Grumman could lead the development of hypersonic propulsion capabilities, with support provided by Ukrainian companies such as Ivchenko, and that Raytheon could assist in developing guidance and targeting systems for the platform. The comment also asks for assistance in manufacturing and designing the platform’s advanced material solutions and thermal management.
• Finland expresses its willingness to participate in the project, with a possibility of investing upwards of a hundred million.

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• Hypersonic flight requires speeds above Mach 5, for military threats, global travel, and achieving Earth’s orbit.

• The thermal boundary and thermodynamic and chemical nature changes of air passing over hypersonic vehicles is discussed.

• The rocket propulsion’s practical use for long-distance vehicles is limited considering the large fraction of propellant they carry. Contrarily, air-breathing engines, such as ramjet and scramjet, increase fuel efficiency compared to rockets regarding engine thrust divided by propellant weight flow rate.

• Scramjets are more complex and challenging to design and operate than ramjets, and they slow and compress air through the action of shock waves and mix and burn fuel in a supersonic airstream.

• The multiple engines’ importance for hypersonic flight (rockets, turbofans, ramjets and scramjets) or integrated combined cycles to enable hypersonic flight is emphasized.

• Travelling speed above Mach 5 has a significant impact until Mach 5; the time-saving asymptotic behavior increasing cruise speed increasingly reduces the time spent cruising.

• Some airlines and companies are exploring design concepts for hypersonic passenger airplanes, including Aerion, Boom, Boeing, Hermeus.

• Carbon- and ceramic-based composite materials are used to build vehicles that fly above Mach 6.

• The technological advances over the past 60 years are discussed, such as computer-based modeling and simulation capabilities for aerodynamics, propulsion, materials, structures, and flight controls.

• Sophisticated optimization using a process called multidisciplinary design optimization is possible.

• Advances in metallic, ceramic, and composite materials are described, as well as engine structures to be lighter and more durable, with higher temperature capability.

• The demand for premium air travel will increase in proportion to overall air travel demand, and the total cost of travel in terms of money, time, and experience.

• Dual-Mode Scramjet technology’s maturation through ground and flight testing is discussed, with the 2004 X-43a flight experiment spin-off from the NASP program that integrated a hydrogen-fueled scramjet on a lifting body airframe. The X-43A successfully operated, generating thrust greater than drag at Mach 7 and approximately equal to drag at Mach 10, and verifying scramjets’ propulsion efficiency potential.

• The Scramjet Engine Demonstrator (X-51A) operated on dual-mode scramjet power for 209 seconds before running out of fuel, accelerating from Mach 4.8 to 5

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• “How to get scientific journals free and bypass paywalls” is a Reddit post from five years ago on r/Nootropics, explaining how to access scientific journals for free.

• The post lists different methods for accessing free journal articles that are otherwise behind a paywall and could be helpful in finding information related to hypersonic propulsion technology.

• Google Scholar is suggested as a resource for searching for articles by title, author, publications and by publication date.

• Free JSTOR account provides access to three articles a month for free, but it is recommended to use it as a last resort due to copyright and legal issues.

• Reddit Scholar is a subreddit where users can ask others to help them find articles, but the post suggests learning to search for articles on your own.

• Libgen is a free resource where users can search for a subject and download free PDFs, sometimes without even knowing the author or proper title. The post recommends using this website because of its vast collection of articles.

• Sci-Hub is a website that stores over 62 million academic papers and articles for direct download. It bypasses publisher paywalls by allowing access through educational institution proxies. The library also stores papers downloaded by Sci-Hub in Library Genesis (LibGen).

• BooksSC is a website alternative to Libgen which is similar but allows for more downloads and access.

• Be cautious to look for review articles when new to a topic, instead of drawing conclusions from one study.

• Review articles provide an overview of a subject and are a good starting point for research, while sci-hub and libgen should be used to find original research studies.

• Reading broadly instead of deeply is recommended when there is limited time for research. Abstracts can often provide enough information for people to make decisions.

• Publish or Perish will search the literature for relevant information and provide useful meta-information, like the impact of the paper and authors.

• SJR is also recommended for journal rankings to determine the quality and relevance of the articles being researched.

• Open-access journals like Frontiers and PLOS are also recommended as resources for finding articles.

• Pre-print archives like bioRxiv are suggested for finding newer articles.

• Sci-Hub and Library Genesis are controversial due to copyright issues, and users are encouraged to donate to these websites.

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• The Hypersonic Technology (HT) project is a NASA research and development program that aims to enable new capabilities for aeronautics and space applications by developing and demonstrating highly efficient, high-speed propulsion technologies.
• Hypersonic flight is typically defined as flight exceeding Mach 5 (five times the speed of sound) and up to Mach 15 (fifteen times the speed of sound).
• Hypersonic vehicles can offer reduced travel times, increased payload capabilities, and improved launch systems for space access.
• The HT project is focused on developing and testing hypersonic propulsion technologies, including air-breathing engines (Ramjet, Scramjet, Rotating Detonation Engines) and rocket engines.
• Ramjet engines compress incoming air to subsonic speeds and use it to combust fuel, allowing for speeds up to Mach 6.
• Scramjet engines use the forward motion of the aircraft to compress incoming air to supersonic speeds and then combust fuel, allowing for speeds up to Mach 14.
• Rotating Detonation Engines (RDE) are a type of rocket engine that uses spinning detonation waves to combust fuel, potentially offering more efficient propulsion than traditional rocket engines.
• Rocket engines use stored propellant and oxidizer to produce thrust, but are typically less efficient than air-breathing engines for hypersonic flight.
• The HT project has a number of past and ongoing test projects to develop and demonstrate hypersonic technologies, including the X-43A, X-51A, and the Hypersonic Inflatable Aerodynamic Decelerator (HIAD).
• The X-43A was a hypersonic aircraft that set the world speed record for air-breathing flight of Mach 9.6 in 2004 using a Scramjet engine.
• The X-51A is an unmanned hypersonic aircraft that has completed multiple flight tests, including a flight of 240 seconds at speeds up to Mach 5.1 in 2013 using a Scramjet engine.
• The HIAD is a heat shield system that can be used to protect spacecraft during atmospheric re-entry, and has been tested at hypersonic speeds up to Mach 7.
• The HT project is part of NASA’s larger Aeronautics Research Mission Directorate (ARMD), which aims to advance aeronautics technology to meet future challenges and support national priorities.

• NASA has been conducting research in hypersonic technologies to enable high-speed air travel, technological and scientific advancements, which includes the development of hypersonic propulsion systems and vehicles.
• Hypersonic flight is defined as flight at speeds above Mach 5 (i.e., five times the speed of sound) in the atmosphere and above Mach 25 outside the atmosphere.
• Hypersonic propulsion systems generally comprise Ramjet, Scramjet, and Rocket engines.
• Ramjet engines use the speed of the vehicle to compress the incoming air before combustion. They can operate up to about Mach 6 and depend on the vehicle’s speed to get started.
• Scramjet engines use a simpler design than Ramjet, while they supersonically compress air by using shock waves, rather than subsonically, and then combustion occurs. The vehicle must be moving at Mach 5 or more before the engine can work, and the compression process is only possible at very high speeds.
• Rocket engines are capable of powering a vehicle in space and producing thrust even when there is no air. However, they require a lot of fuel, making them less practical for flights within the Earth’s atmosphere.
• NASA has conducted many tests to develop and improve hypersonic propulsion technologies, especially Scramjet. Researchers have achieved speeds up to Mach 9.6 using a Scramjet-powered vehicle.
• NASA is also exploring other hypersonic propulsion technologies like the Rotating Detonation Engine (RDE), which NASA believes may have advantages over traditional engines in terms of efficiency and the ability to run on unconventional fuels.
• To test these various hypersonic propulsion technologies, NASA has developed a range of testing facilities such as the Hypersonic Air-Breathing Propulsion Laboratory (HAPL) and the X-43 Hyper-X Program.
• The HAPL is a ground-based facility that simulates hypersonic flight and performs experiments to validate computational models of aerospace vehicles. It has a Mach 5 wind tunnel and uses a “Freejet” combustion chamber to simulate high-altitude flight at Mach 7 or more.
• The X-43 Hyper-X Program was one of NASA’s most ambitious programs to date and was designed to develop and test hypersonic vehicles with Scramjet engines. The program achieved its goal of reaching Mach 10, more than 7 miles per second.
• Thermal protection is crucial for hypersonic vehicles. NASA has developed various materials and coatings for thermal protection on the structures of hypersonics vehicles, including the X-43.

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Here are my notes:

• The paper is titled “Analysis and Design of a Hypersonic Scramjet Engine with a Transition Mach Number of 4.00.”
• The authors are Kristen N. Roberts and Donald R. Wilson from the University of Texas at Arlington.
• A scramjet (supersonic combustion ramjet) is used in place of a ramjet when pressures and temperatures become so high that it is no longer efficient to slow the oncoming flow to subsonic speeds for combustion.
• The focus of the project discussed in the paper is to lower the starting Mach number of a scramjet engine to enable takeoff to hypersonic flight using only a turbojet and a scramjet, with no ramjet cycle in between.
• Currently, the transition to supersonic combustion generally occurs at a freestream Mach number around 5.0 to 6.0.
• The specific goal of the project is to determine whether the scramjet starting Mach number could be lowered to Mach 3.50 and, if not, what the constraints are that prohibit it and what the lowest possible starting Mach number for a scramjet is with today’s technology.
• Analysis was completed towards extending scramjet operability to lower Mach numbers, while maintaining performance at higher Mach numbers within the same flowpath as detailed in the Air Force solicitation AF073-058.
• The paper explains that a scramjet with a starting Mach number of 3.50 is not currently possible with the fuels researched unless fuel additives or other modifications to the system are used. However, a scramjet with a starting Mach number of 4.00 is possible with today’s existing technology.
• The paper details engine flowpath design and specifications for a scramjet with a starting Mach number of 4.00.
• The paper provides a nomenclature list explaining the variables and abbreviations used in the analysis.
• The engine performance analysis inputs include data such as Mach Number, Stagnation Temperature of Freestream Air, Specific Heat, Specific Fuel Consumption, fuel-to-air ratio, burner efficiency among others.
• The analysis was done using a one-dimensional flow approach that assumes that the fluid properties remain constant across the flow and thus only depend on the axial dimension coordinate.
• A control volume definition of the scramjet engine was used to analyze the engine performance.
• The paper does not provide information on other hypersonic propulsion technologies such as Ramjet, Rotating detonation, and Rockets.

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💭  Looking into

Explanation of hypersonic propulsion technologies generally

💭  Looking into

Comparison between Ramjet and Scramjet technologies