Hypersonic Technologies Race: Overcoming Gaps, Obstacles, and Technological Challenges in the Pursuit of Hypersonic Weapons

Rajesh Uppal May 10, 2024 Air Force, Space, Weapons Comments Off on Hypersonic Technologies Race: Overcoming Gaps, Obstacles, and Technological Challenges in the Pursuit of Hypersonic Weapons 1,635 Views

Introduction:

The era of hypersonic flight has dawned upon us, ushering in a new age of aerospace technology. Hypersonic refers to aircraft, missiles, rockets, and spacecraft that can reach speeds through the atmosphere faster than Mach 5, which is nearly 4,000 miles per hour.

This paradigm shift in aviation has sparked a global race, driven by the pursuit of faster space access and revolutionary military capabilities. However, with these aspirations come formidable challenges—challenges that demand innovative solutions to propel us into the future of hypersonic travel and defense. Hypersonic weapons, capable of flying at speeds greater than five times the speed of sound, present a paradigm shift in military capabilities.

But this isn’t just about who has the fastest weapon – the stakes hold the potential to reshape warfare, transportation, and even space exploration. As nations endeavor to harness the potential of hypersonic technologies, they face numerous gaps, obstacles, and technological challenges that must be overcome to achieve success in this high-stakes competition.

Hypersonic technologies unleashed

Hypersonic flight encompasses a spectrum of vehicles, from missiles and rockets to spacecraft and aircraft, hurtling through the atmosphere at speeds exceeding 4,000 miles per hour. The primary impetus behind hypersonic research lies in the quest for cost-effective space travel and rapid global transportation.

The large driving force behind hypersonic research emerges from the need to reduce cost to space and faster global transportation for both military and civilian purposes. Envision a future where intercontinental journeys from the UK to Australia take a mere two hours, thanks to hypersonic spaceplanes currently in development.

Military applications of hypersonic technologies are equally compelling, promising game-changing capabilities such as prompt global strike, launch on demand, satellite servicing, and antisatellite missions. Systems that operate at hypersonic speeds—five times the speed of sound (Mach 5) and beyond—offer the potential for military operations from longer ranges with shorter response times and enhanced effectiveness compared to current military systems.

Nations like the United States, Russia, and China are not only developing sixth-generation fighters capable of achieving hypersonic speeds but are also locked in a fierce global race to deploy hypersonic missiles.

Hypersonic flight involves achieving speeds exceeding Mach 5 (five times the speed of sound) and requires overcoming complex aerodynamic, thermal, and material science challenges.

Unmatched speed: Intercepting hypersonic missiles is like trying to catch a bullet with a tennis racket. Their sheer velocity renders existing missile defenses largely obsolete, providing attackers with a potentially decisive edge.
Elusive maneuverability: Unlike traditional ballistic missiles, hypersonic vehicles can glide and change course during flight, making them even harder to track and neutralize.
Global reach: The ability to strike targets anywhere on the planet within minutes creates a new level of strategic deterrence and offensive capability.

No wonder nations like the United States, China, Russia, and India are investing heavily in hypersonic research and development. The potential rewards are too great to ignore, even with the technological hurdles so high.

Types of Hypersonic Weapons:

Hypersonic speed, defined as anything above Mach 5, gives rise to two main types of weapons: hypersonic cruise missiles and hypersonic glide vehicles. The former employs an advanced SCRAMJET propulsion system, offering incredible speeds between Mach 5 and Mach 15. These missiles can strike their targets within a mere six minutes of launch. However, maintaining sustained hypersonic flight necessitates overcoming extreme temperatures, requiring the development of ultra-high-temperature materials.

On the other hand, hypersonic glide vehicles, propelled by boosters to reach the appropriate speed and altitude, glide back down unpowered. Functioning like a plane without an engine, these vehicles leverage aerodynamic forces for stability, secrecy, and maneuverability, making them formidable and unpredictable.

Hypersonic cruise missiles can fly at altitudes up to 100,000 feet whereas hypersonic glide vehicles can fly above 100,000 feet. An “air-breathing” hypersonic vehicle approach allows less range than boost-glide but greater maneuverability. Air-breathers can also be significantly smaller. A rocket has to carry large amounts of oxidizer to burn its fuel. A jet just sucks in oxygen from the atmosphere. But normal jets don’t have to suck in air moving at Mach 5-plus. A jet that works at hypersonic speeds will require some breakthroughs — and, again, 3D printing can help grow the exotic components.

Bridging the Gap: Overcoming Gaps and the Obstacles

Embarking on the journey of hypersonic technology introduces multifaceted engineering challenges. Two hurdles that essentially link into a co-hurdle are the extreme hypersonic flight conditions and hypersonic mission objectives.

Hypersonic flight realm traverses a complex environment as, “ranging from high in the stratosphere to operations into and cross the demarcation of spaceflight, where the laws of aerodynamics cease to apply and the laws of ballistic, Keplerian trajectories, and Hohmann transfers take over.” Hypersonic revolution blends the twin stream of space and aeronautics research into a confluence.

For example, mission objectives include space access and global transportation. Space access not only requires the attainment of very high vehicle velocities but also must traverse the varying atmospheric layers to reach an orbital path. Global access missions also benefit from hypersonic speeds but do not require the large orbital altitudes. Therefore, HV systems provide the desired speeds but demand complexity.

University of Queensland, Australia claims that flight beyond Mach 14 is difficult to sustain, and it becomes hard to burn fuel and the drag becomes too high. Aerodynamic drag roughly scales with the square of airspeed; double the speed, and the drag goes up four times. Streamlined shapes have partly overcome this problem, but the solution then, as it is now, is more thrust. However, hypersonic speeds are frequently limited not by available thrust or drag, but by the heat buildup caused by atmospheric friction.

One of the primary hurdles is contending with the extreme conditions of hypersonic flight, spanning high turbulence, pressure, temperature, and density. The air and gases react differently than at subsonic speed; materials are put under extreme temperatures and pressure; and there is the added challenge of guidance mechanisms also needing to withstand those pressures.

Unlike traditional ballistic missiles or aircraft, hypersonic vehicles operate in an environment where the air resistance generates immense heat, necessitating advanced thermal protection systems. Turbulence can make things worse. At hypersonic speeds, the boundary layer around the vehicle thickens, and a smooth, laminar flow can suddenly break up into eddies and swirls that cause temperature spikes on the vehicle’s skin.

Today active research and development is in progress on all aspects of hypersonic flight, from materials to withstand high temperatures generated in the atmosphere, to more efficient propulsion systems, to size, weight and power (SWaP)-constrained enhanced electronics for sensors, guidance, communications, and other harsh-environment applications.

Technologies of interest include:

Advanced air vehicle configurations capable of efficient hypersonic flight
Hydrocarbon scramjet-powered propulsion to enable sustained hypersonic cruise
Approaches to managing the thermal stresses of high-temperature cruise
Affordable system designs and manufacturing approaches

Heat management: At hypersonic speeds, friction turns air into plasma, reaching temperatures exceeding 2,000 degrees Celsius. Finding materials that can withstand this inferno without melting or losing their structural integrity is crucial. The structural problems are primarily caused by processes called oxidation and ablation. This is the when extremely hot air and gas remove surface layers from the metallic materials of the aircraft or object traveling at such high speeds.

Innovative Materials: The development of materials capable of withstanding extreme heat and speed is paramount. Materials must withstand oxidation and ablation, and the complex physics involved demand innovative solutions.

Developing materials that can withstand extreme heat while remaining lightweight is crucial for the success of hypersonic vehicles.

Ultrahigh-temperature materials are essential for protecting hypersonic airframes, ensuring structural integrity.

There is growing interest in developing ultrahigh temperature materials (UHTM). These are materials with temperature capability greater than 1650 °C and able to withstand extreme erosive / corrosive environments. UHTM should possess high strength at high temperatures, oxidation resistance, ablation resistance, thermal shock resistance.

These materials will be required for hypersonic air breathing vehicles, hyper speed cruise missile, hypersonic aircrafts, re-usable launch vehicles to protect leading edges and nose cones that experience very high temperatures (> 2000 °C). Refractory diboride composites like ZrB2, HfB2 etc and multilayer coatings of HfC, SiC on C-C composites are most promising UHTM candidates.

Chinese scientists have achieved a significant breakthrough in hypersonic missile technology by developing a special surface material for “waverider” aircraft.

This material, tested by the China Academy of Aerospace Aerodynamics (CAAA), can rapidly absorb heat, marking a major advancement in thermal protection technology. The success of the test positions China ahead of the U.S. in hypersonic capabilities. The newly developed technology not only enhances hypersonic missile performance but also has broader implications for fast aircraft traveling at hypersonic speeds. It opens the door to the development of reusable hypersonic missiles, vehicles, and aircraft with longer ranges and faster speeds, potentially ushering in a new era of stealth military aircraft capable of global operations within hours. The breakthrough reflects a shift in the hypersonic technology race, presenting new opportunities for China in the realm of advanced aerospace capabilities.

Propulsion: Current rocket engines struggle to maintain sustained hypersonic speeds. Achieving and sustaining hypersonic speeds necessitate innovative propulsion systems.

Solid, liquid, and hybrid rockets, in conjunction with turbine, ramjet, and scramjet engines, embody some of the available propulsion concepts that are capable of hypersonic flight. Two branches emerge as the dominant hypersonic engine mechanisms, the rocket motor and the air-breather. Ramjets become less efficient at higher Mach numbers due to the ramjet’s subsonic combustion.

Scramjets potentially hold the capability to realize the objective of a long range airliner at hypersonic speeds and, complement the traditional rocket in space launchers. In this type of vehicle, the engine gets the oxygen it needs for combustion from the atmosphere passing through the vehicle, instead of from a tank onboard. This eliminates the need for heavy reservoir oxygen tanks, and makes the vehicle far smaller, lighter, and faster than a conventional rocket.

Scramjet engines, which rely on supersonic combustion, are one of the leading candidates for hypersonic vehicles. However, optimizing their performance across a range of speeds poses a significant technological challenge. At hypersonic speeds, air molecules spend milliseconds in the engine tube—scant time for fuel and air to mix properly. And when a vehicle pitches and yaws, airflow into the engine changes, which can result in uneven combustion and thrust. Tweaks to get a better burn have ramifications for, say, how the aircraft withstands shock waves.

Maneuverability: Hypersonic systems must exhibit precise maneuverability to operate in contested environments. This necessitates advanced control systems and aerodynamic designs. The need to operate in several flight regimes can lead to unforeseen aerodynamic conditions, especially in air-breathing propulsion systems. While a certain shape or lift-to-drag (L/D) configuration may be efficient at low hypersonic Mach numbers (say 4-8), it may exhibit a severe degradation in aerodynamic performance outside this envelope. This would be the case, for example, during the takeoff and landing phases of a space plane.

Guidance and control: The need to transition through various atmospheric layers further complicates the aerodynamic conditions, particularly for air-breathing propulsion systems. Precise maneuvering becomes a delicate act at hypersonic speeds. Developing algorithms and sensors capable of making split-second decisions to navigate the vehicle through dynamic flight conditions is an ongoing technological challenge. Advanced sensors and control systems are required to navigate the turbulent airflow and ensure accurate targeting.

Other relevant areas that fall under this category consist of control surfaces such as fins, elevons, tailerons, flaperons, etc. The technological factors associated with these control surfaces include:

The requirement to employ thin structures that reduce drag.
The need to overcome the thermal protection barriers imposed by the thin surface requirement
The need to design for longer life cycles and mitigate oxidation.
The need to integrate both hot and cold structures (e.g., in actuators).

Designing a hypersonic vehicle requires a delicate balance, considering factors ranging from thin shock layers and viscous interactions to changes in stability and control.

Four primary functions embedded electronics that will need to perform for deployable hypersonic platforms:

Mission computing, focused on responding to commands, adjusting to changing conditions and ensuring that all subsystems work in concert to accomplish a platform’s mission;
Flight computing, controlling the path of the platform, monitoring the outputs of sensors and controlling the operational employment of sensors;
Real-time signal processing for radar, electro-optical sensors, and electronic warfare (EW); and
flawless and secure communications with command and control networks.

Communications: Maintaining connectivity during hypersonic flight requires robust global communication and sensor systems. Operating at incredible speeds demands an unparalleled degree of precision and reliability.’

Sensors and electronics must also be hardened to withstand extreme conditions.

Hypersonics represent a variety of technological challenges, particularly for electronics and electro-optics manufacturers, to protect against chock, vibration, and extremes in electronics cooling and thermal management that non-hypersonic weapons rarely face. While a bullet shot from a gun, for example, travels at about 1700 miles per hour, or Mach 2.2, the hypersonic weapons with speed more than twice are expected to give higher acceleration and shock to ruggedized electronics to deal with.

“Traveling at those speeds, the vibration profiles will evolve beyond what typical standards currently call for, so you have a lot of work to do on printed circuit boards, all the separable connector failure points and mitigating the effects of those so you don’t have failures, either right away or fatigue failures, which are worse,” says Ivan Straznicky, chief technology officer for advanced packaging at Curtiss-Wright Defense Solutions. You need electronics that can survive above typical temperature ranges, which may require unique solutions, such as vapor chambers or perhaps some type of liquid cooling.

“Uncontrolled energies at resonant frequencies can rapidly destroy components and connections throughout an embedded computing system. Some hypersonic platform designs further complicate the mechanical vibration challenge by using an engine that varies its combustion behavior based on altitude,” says Abaco’s Graves. “This innovative propulsion solution also means that the engine vibration characteristics will vary, further complicating embedded electronics designs,” Graves says. “Other environment considerations are not related to hypersonic speeds, but must still be accounted for, based on a given platform’s mission profile.”

“Vibration effects, as well as acceleration G forces and pyrotechnic shock, can all be mitigated by using damping materials at physical connection points, both within a system chassis and where the chassis is attached to the airframe,” according to Graves. But the extremes to which hypersonic flight pushes all environmental requirements — especially at speeds in the Mach 20 to Mach 30 range envisioned for hypersonic missiles — means there must be significant advances in every component and every method used to defeat those challenges.

Simulations are used to identify potential weaknesses in COTS components used in the design, then those are strengthened and secured to ensure they can withstand the hypersonic environment before they ever go on a flight test vehicle.

Solving these problems demands not just financial muscle, but also scientific ingenuity and international collaboration. Universities, private companies, and government agencies are working together to push the boundaries of hypersonic technology, fueled by a sense of urgency and the potential for groundbreaking breakthroughs.

3D printing: The escalating hypersonic arms race is witnessing the transformative impact of 3D printing on the future of high-speed warfare. Going beyond speed, 3D printing is positioned as a crucial contributor, promising unparalleled design freedom, heightened efficiency, and expanded possibilities in the realm of hypersonic vehicles. One key advantage lies in the ability of 3D printing to address the intricate internal channels and unconventional geometries essential for efficient hypersonic cooling systems. By “growing” components with built-in cooling channels of optimal shapes, such as spirals or helices, 3D printing enhances heat dissipation and prolongs component lifespan. This innovation not only reduces weight but also liberates space, enabling the creation of smaller, faster, and more maneuverable hypersonic vehicles.

The versatility of 3D printing shines through in its application to both Boost-Glide and Air-Breathing approaches in hypersonic technology. For Boost-Glide, 3D printing facilitates the creation of precise control surfaces and lightweight structures, addressing complex aerodynamics, stability, and control needs. In the Air-Breathing approach, 3D printing’s capability to handle high-temperature materials and intricate geometries allows the production of detailed and accurate components, crucial for sustaining hypersonic combustion at speeds exceeding Mach 5. Recent breakthroughs, such as Orbital ATK and NASA’s successful test of a 3D-printed scramjet combustor, underscore the viability of 3D printing for core hypersonic engine parts, while Raytheon’s focus on 3D-printed cooling systems emphasizes the efficiency gains and design flexibility offered by this technology, leading to the development of smaller, lighter, and longer-range hypersonic weapons. Beyond military applications, the potential of 3D printing extends to revolutionizing hypersonic commercial flights and reusable space launch vehicles, ushering in an era defined by faster, more affordable travel and accessible space exploration. However, challenges persist, including the ongoing development of high-temperature alloys and exotic materials suitable for hypersonic environments, as well as the need for continued innovation to address the cost and scalability limitations of 3D printing for large, complex components. Despite these challenges, 3D printing stands as a catalyst for hypersonic innovation, poised to redefine the boundaries of what is achievable in terms of speed, efficiency, and design freedom.

Testing Infrastructure: Establishing robust testing infrastructure for hypersonic technologies is critical. Wind tunnels and testing facilities capable of replicating hypersonic conditions are essential for validating design concepts and ensuring the reliability of hypersonic vehicles.

The hypersonic wind tunnel is used to test flight characteristics in a hypersonic region of Mach number 5 or more. For example, in March 2018, China’s state media announced construction on an 870-foot wind tunnel capable of simulating conditions from Mach 10 to Mach 25. Scheduled for completion in 2020, it will join existing wind tunnels able to simulate environments from Mach 5 to Mach 9.

US Hypersonic Wind Tunnels:

The U.S., by comparison, has Mach 5 to Mach 9 wind tunnels, but they are smaller than the Chinese tunnels, and capable of tests lasting only a few seconds.

National Hypersonic Research Initiative (NHRI): Established in 2023, this initiative boasts two state-of-the-art hypersonic wind tunnels:
- Mach 7 Tunnel: Operates at Mach 7 for extended durations, offering unparalleled testing capabilities for hypersonic vehicles and materials.
- Mach 15 Tunnel: Capable of simulating Mach 15 conditions for brief periods, pushing the boundaries of hypersonic research and development.
Increased Testing Capacity: These facilities complement existing US hypersonic wind tunnels (like the High-Speed Wind Tunnel at AEDC) and significantly increase testing capacity, duration, and Mach range.

Hypersonic Demonstrations

1. Hypersonic “Cruise-Missile Revolution”: The U.S. Air Force is no longer just chasing hypersonic glide vehicles. Their Air-Launched Rapid Response Weapon (ARRW) program successfully completed its first live-fire test launch in December 2023, paving the way for a new generation of air-launched, scramjet-powered hypersonic cruise missiles. Imagine ultra-fast, maneuverable projectiles deployed from fighter jets, blurring the lines between traditional air warfare and hypersonic warfare.

2. “Hypersonic Wave” Over the Pacific: China’s latest test of its “Starry Sky-2” hypersonic missile reportedly utilized a new “wave-riding” design, allowing for longer and more stable flights thanks to its unique shape. This advancement hints at potential improvements in range and accuracy, raising concerns about the evolving capabilities of Chinese hypersonic technology.

3. AI Takes the Controls: From Autopilot to Hypersonic Pilot: Artificial intelligence is stepping into the cockpit of hypersonic vehicles. Researchers are developing AI-powered guidance systems that can navigate the turbulent, unpredictable airflows at Mach 5 and beyond, allowing for autonomous hypersonic flight and potentially improving the overall efficiency and effectiveness of these complex machines.

4. Hypersonic Wind Tunnels: Simulating the Unspeakable: Testing hypersonic vehicles is like throwing a pebble into a supernova – incredibly hard and potentially catastrophic. That’s why hypersonic wind tunnels are crucial. The US Air Force recently unveiled its “National Hypersonic Research Initiative” (NHRI), featuring two state-of-the-art facilities to simulate the blistering conditions hypersonic vehicles face, accelerating testing and development.

Beyond the Boom:

The hypersonic race isn’t just about military dominance. The potential civilian applications are mind-boggling:

Hypersonic travel: Imagine zipping from New York to Tokyo in under an hour or exploring the Earth’s atmosphere with unmatched speed. Hypersonic aircraft could revolutionize travel and tourism.
Space Access: Faster, cheaper, and more reusable hypersonic vehicles could be the key to unlocking affordable space transportation, opening up a new era of space exploration and commercialization.
Scientific Breakthroughs: Studying hypersonic phenomena could lead to advancements in materials science, energy generation, and other fields, fueling innovation across diverse industries.

Challenges Remain:

While the future is bright, several hurdles persist:

Cost and complexity: Hypersonic technology is expensive and requires cutting-edge materials and engineering expertise, making it a niche field for now.
Arms race concerns: The rapid development of hypersonic weapons raises fears of an escalating arms race and destabilized international relations.
Safety and environmental impact: Hypersonic testing and deployment need careful management to ensure safety and minimize environmental damage.

The Path Forward:

As nations strive to overcome these gaps, obstacles, and technological challenges, collaboration and knowledge-sharing among scientists, engineers, and policymakers become vital. International cooperation can foster the development of standardized testing procedures, accelerate technological advancements, and facilitate the responsible use of hypersonic technologies.

The pursuit of hypersonic weapons is not merely a technological competition; it raises ethical, geopolitical, and strategic considerations. Transparency in the development and deployment of hypersonic capabilities can contribute to global stability and foster dialogue among nations.

Conclusion:

The hypersonic technologies race is a testament to the evolving landscape of defense capabilities and the quest for strategic superiority. The pursuit of hypersonic flight heralds a new era in aerospace technology, offering the promise of rapid global transportation and unparalleled military capabilities. However, the path to realizing this potential is laden with formidable challenges, from material science to aerodynamics and electronics.

Collaborative efforts, international partnerships, and relentless research and development are imperative to overcome these hurdles and navigate the complexities of hypersonic flight. The path forward requires a delicate balance between national security imperatives, international collaboration, and ethical considerations to ensure a future where hypersonic technologies contribute to global stability rather than instability.

As nations race to unlock the full potential of hypersonic technologies, the integration of breakthroughs in heat management, materials science, propulsion systems, and electronics will determine the winners of this high-stakes technological odyssey. Hypersonic flight isn’t just a race; it’s a testament to human ingenuity, pushing the boundaries of what’s possible and reshaping the future of aviation and defense.