The Future of Naval Warfare: Supersonic Submarines

Chinese_subsResearchers in China are reporting that they’ve taken a big step towards creating a truly revolutionary submarine. For years, the nation has been dedicated to the expansion of the People’s Liberation Army Navy (PLAN) Submarine Force. That latest announcement in this plan is the intended development of supersonic submarines. And if feasible, it could a sub to travel from Shanghai to San Francisco a distance of about 9650 km (6,000 miles) – in just 100 minutes.

The research behind this proposed development comes from the Harbin Institute of Technology’s Complex Flow and Heat Transfer Lab, where researchers are applying a concept known as supercavitation. Originally conceived by the Soviets in the ’60s to create high-speed torpedoes, the Harbin researchers are looking to take things to the next level by applying it to a much larger sea-faring vessel. is commonly known, objects moving through water have a harder time than those moving through air. While automobiles are only able to travel so fast before succumbing to wind resistance (aka. drag), surface ships and submarines must content with fluid-dynamics, which are much more tricky. Compared to air, water is far more dense and viscous, which means more energy is required to get up to a certain speed.

Even the most modern and advanced nuclear submarine cannot travel much faster than 40 knots (74 kph/46 mph), and the same applies to torpedoes. Higher speeds are possible, but would require so much power to make it impractical. That’s where supercavitation comes into play, a technique devised with the explicit purpose of creating high-speed torpedoes during the Cold War.

Shkval_headThis technique gets around the drag of water by creating a bubble of gas for the object to travel through. In the hands of the Soviet’s, the research resulted in the Shkval torpedo, which uses a special nose cone to create the supercavitation envelope that allows it to travel through the water at speeds of up to 200 knots (370 kph/230 mph) – much, much faster than the standard torpedoes fielded by the US.

The only other countries with supercavitational weapons are Iran – which most likely reverse-engineered the Russian Shkval – and Germany, the creators of the Superkavitierender Unterwasserlaufkörper (“supercavitating underwater running body”). The US is researching its own supercavitational torpedo, but there’s very little public information available. Meanwhile, China is not only looking to create supercavitating torpedoes, but an underwater vessel.

supercavitational-torpedo-techUnlike previous designs, which had to be launched at speeds of 95 km (60 mph) to create a supercavitation bubble, the method described by the Harbin researchers uses a “special liquid membrane” to reduce friction at low speeds. This liquid is showered over the object to replenish the membrane as it’s worn off by the passage of water, and once the object gets up to speed, it would theoretically use the same nose-cone technique to achieve supercavitation.

In theory, supercavitation could allow for speeds up to the speed of sound — which underwater is 5343 kph (3,320 mph) – which would allow a sub to go from Shanghai to San Francisco in well under two hours. For any nation with a nuclear arsenal – i.e. China, Russia, France, the UK, the US – the ability to deploy nuclear missile subs speedily around the world is certainly desirable. of course, there are some challenges posed by the concept and any ship that is equipped to run on it. For one, it is very difficult to steer a supercavitating vessel and conventional methods (like rudders) don’t work without water contact. Second, developing an underwater engine that’s capable of high velocity over long distances is very difficult. Jet engines do not work underwater and generally, rockets only have enough fuel to burn for a few minutes.

Nuclear power might be a possibility as far as supersonic submarines go, but that’s strictly academic at this point. Li Fengchen, a professor at the Harbin Institute, says their technology isn’t limited to military use. While supersonic submarines and torpedoes are at top of the list, the same technology could also boost civilian transport, or even boost the speed of swimmers. As Li put it:

If a swimsuit can create and hold many tiny bubbles in water, it can significantly reduce the water drag; swimming in water could be as effortless as flying in the sky. always with such advanced (and potentially weaponized) technology, it’s hard to say how far away it is from real-world application. Given that this is primarily a military research project within China, one can expect that it will remain shrouded in secrecy until it is ready. And if civilian researchers are making good progress, then it’s a fairly safe bet that the military is even further along.

While the future of transit is already exciting – what with hyperloops, aerospace travel, robotaxis and robot cars – the idea that people could travel under the waves as fast as on they could on the Concorde is pretty cool! At the same time, the idea that subs equipped with nuclear missiles could reach our shores within two hours is pretty scary. But futuristic military technology has never been known to inspire warm and fuzzy feelings, has it?


The Future of Flight: Morphing Wings

morphing-wingsSince the Wright Brothers developed the world’s first airplane, scientists and aerospace engineers have understood how important airflaps and wing design are to ensuring that a plane is able to achieve lift and land safely. During and after World War II, additional lessons were learned, where the sweep of a wing was found to be central to a plane achieving higher service ceilings and air speed velocities.

Since that time, many notable improvements have been made, but some strictures have remained the same. For example, conventional wings suffer from the problem of being fixed in a single position, which makes some aspects of performance possible but other things extremely difficult. In addition, flaps have remained virtually unchanged over the years, relying on hinged joints that are limited and vulnerable.

flexfoilIn both cases, the answer may lie in flexible and seamless materials, leading to wings that can change shape as needed. Such technology could not only enable better performance, but remove the need for hinges and gears. Towards this end, Michigan-based FlexSys has developed a way to optimize wing aerodynamics with FlexFoil, a seamless variable geometry airfoil system.

In development since 2001, FlexFoil is made from what is described only as “aerospace materials,” and is seamlessly integrated into the trailing edge of the wing. Based on a technology known as “distributed compliance,” the morphing structure integrates actuators and sensors that, according to Flexsys, results in “large deformations in shape morphing with very small strains.”

flexfoil1According to a 2006 paper co-written by mechanical engineer Dr. Sridhar Kota (the FlexFoil’s inventor), the foils are:

optimized to resist deflection under significant external aerodynamic loading and are just as stiff and strong as a conventional flap.

What this translates to in real terms is a tolerance of over 4500 kg (10,000 lbs) in air loads and the ability to distribute pressure more evenly throughout the wing, resulting in less strain in any one area. It is also said to reduce wind noise by up to 40 percent on landing, and to lessen build-up of both ice and debris. But the biggest benefit comes in terms of fuel economy.

flexfoil2When retrofitted onto a wing, FlexFoil can reduce fuel consumption by a claimed 4 to 8 percent, with that number climbing to 12 percent for those wings that are built are the system. What’s more, the technology could be applied to anything that moves relative to a fluid medium, including things like helicopter rotor blades, wind turbine blades, boat rudders, or pump impellers.

FlexFoil was officially introduced to the public this week at the AIAA (American Institute of Aeronautics and Astronautics) SciTech exposition in Washington, DC. Plans call for flight tests to be performed this July at NASA’s Dryden Flight Research Center, where the flaps of a Gulfstream business jet will be replaced with the foils.

Check out this video of the airwing design and what it does here:

morphing-wings1To be fair, this is not the only case of flexible, morphing aircraft in development right now. In fact, NASA has been looking to create a morphing aircraft concept ever since 2001. So far, this has included collaborating with Boeing and the U.S. Air Force to create the Active Aeroelastic Wing (AAW) which was fitted to the F/A-18 Hornet, a multirole combat jet in use with the USAF.

But looking long-term, NASA hopes to create a design for a morphing airplane (pictured above). Known as the 21st Century Aerospace Vehicle, and sometimes nicknamed the Morphing Airplane, the concept includes a variety of smart technologies that could enable inflight configuration changes for optimum flight characteristics, and is an example of biomimetic technology.

morphing-wings2In this case, the biological design being mimicked is that of a bird. Through the use of smart materials that are flexible and can change their shape on command, the 21st Century Aerospace Vehicle is able to shape its wings by extending the tips out and slightly upward to give it optimal lift capability. In this configuration, the inspiration for the aircraft’s wings is most clear (pictured above).

But once airborne, the aircraft needs a wing that is capable of producing less wind resistance while still maintaining lift. This is why the wings, upon reaching and service ceilings in excess of 3000 meters (10,000 feet), the wings then contract inward and sweep back to minimize drag and increase airspeed velocity.
Though this program has yet to bear fruit, it is an exciting proposal, and provides a glimpse of the future.

Be sure to check out NASA’s video of the CAV too, and keep your eyes on the skies. Chances are, jets that utilize smart, morphing surfaces are going to be there soon!