Smarter Missiles

Since its inception in 1992, ORI has been involved in a number of research programsfunded by the U.S. Army, Air Force, the government’s Defense Advanced ResearchProject Agency (DARPA), and the Special Operations Command (SOCOM). The 26-personcompany has also collaborated on research and development programs with a numberof large defense contractors, including Lockheed Martin and General Dynamics.

A comparison of projectile shock structures with different fin designs visualizedwith Tecplot. Far left: A projectile with planar fins shows a higher shock structureconcentration than the projectile shown near left, which has swept fins. Due tolower shock-fin interactions, the swept-fin design generates less supersonic dragand therefore allows the projectile to fly greater distances.

Among the Aerodynamics Group’s most successful RandD programs is Smart SkinSolutions for Missile Control. Working closely with Air Force Research Labs andthe Army’s Tank, Automotive and Armaments Command, ORI has developed a uniquemissile control system using novel flow control actuators and advanced controlalgorithms. These systems are custom-engineered to improve the achievable range,control, and final maneuverability of missiles as well as other weapons flyingat both subsonic and supersonic speeds.

While working on a program to improve the efficiency of missiles and projectiles,Patel’s group discovered that traditional hinged control surfaces impose significantlimitations on the range, payload, and aerodynamic performance of slender bodies.Hingeless control surfaces integrated with miniature control actuators, on theother hand, expand the overall range and payload of the missile—shaving considerableweight by eliminating large-volume servo motors traditionally used to deflectthe fin surfaces, while providing faster and better control and maneuverability.The researchers demonstrated that flow control technology presents innovativelow-cost alternatives for maneuvering missiles by using a smart, integrated systemof sensors, actuators, and controllers.

The company is developing a smart skin technology where the aerodynamic surfacecontains an embedded system of miniature sensors on the outer surface, controlactuators, and a real-time feedback controller just below the surface, all ofwhich are unseen from the exterior. The outer layer of skin is perforated withminiature slits and holes at specific locations. Inducing small perturbationsat these locations on the fins using MEMS-enabled actuators creates a large effecton the flowfield around that region is created. This forces an overall changein the pressure distribution around a significant portion of the surface, andpitch, roll, or yaw adjustments can be made in real time. The control system canbe transparent to the missile guidance, navigation, and control (GNC) system andcan be operated autonomously by a ground- or air-based pilot, or can be integratedto be operated by the onboard GNC system.

To validate its research findings and test active flow control system prototypes,ORI’s Aerodynamics Group relies on low- and high-speed wind tunnel tests and CFDsimulations. “By combining CFD analysis with wind tunnel experiments,” Patel explained,“we are able to reduce the total turnaround time for feasibility studies as wellas systems development.”

For computational studies, Patel’s group uses WIND code, a solver developed bythe merger of three CFD codes (NASTD, NPARC, and NXAIR). But because his groupleans so heavily on CFD simulations, Patel turned to Tecplot for a CFD postprocessingtool. He purchased a single floating network license of the technical plottingand data visualization software package in February of 2003. When coupled withan add-on product called the CFD Analyzer, also developed by Tecplot, Patel saidhe has found the perfect solution.

“I was looking for an extensive, yet not too expensive, data plotting softwarepackage,” Patel says. “After learning more about the capabilities of Tecplot andits add-on tool, the CFD Analyzer, which lets the user calculate variables andextract critical information from the dataset, it seemed an obvious pick for ourdata processing needs.”

Tecplot, through its 2D and 3D plotting capabilities, helped ORI visualize andquantify how airflow is affected by the virtual shaping in the smart skin andhow force is being created for pitch, roll, and yaw control. Tecplot’s supportteam helped simplify the two million grid point geometry of the 3D missile model,and analyze data in regions around the missile body where the flow interactionis most interesting to observe.

“It allows me to work on a specific group of zones ]by turning off other zones]to achieve a high-level of resolution in analyzing complex data in a small regionof the entire computational domain,” says Patel. “Furthermore, it enables a comprehensivedata analysis and flow visualization of the entire dataset using an easy accessmacro and panel in a 2D or a 3D format.”

By creating animations, which were then correlated to the wind tunnel resultsthat ORI had gathered, Tecplot provided insight into the flow physics around themissile body and flow interaction with fins, which helped ORI optimize the actuatorparameters for improved aerodynamic performance.

Patel typically uses 2D slices, contour plotting, streamtraces, and the CFD Analyzer.“These features are important to anyone doing CFD postprocessing, and I find myselfcalling upon them on a daily basis,” he explains.

Although he’s only been using Tecplot for a little more than one year, Patelis already able to define its return-on-investment to his organization. “Mostsignificantly, we have seen a major reduction in CFD postprocessing time,” hesaid. “This means that more resources can be devoted to running CFD simulationsand analysis rather than struggling with data plotting issues. In addition, theresults of our experiments and simulations are clear and well-documented. Thecombination of 2D and 3D images and a few relevant animations…helps us communicateresults to our customers in a very clear and concise manner, conveying our technologyefficiently.”

As a result of the simulations and testing, ORI has shown that by incorporatingcompact sensors, actuators, and a controller inside the missile fin surface, itsnew missiles can fly faster for longer distances. And, since the response ratesof these actuators are high compared to traditional fin deflection devices, theyprovide “end-game maneuverability” to missiles, which is essential for high precision.

The military is currently evaluating this new control technology to enhance theaccuracy of these next-generation weapons.

Peter Masi is a freelanc writer and the founder of Masi PR. He specializes in high-technologytrades as well as mainstream business. To contact him about this article, e-mailhim at Desktop Engineering Feedback.