Rugged, wearable computers tailored for the warfighter
Designers of rugged mobile computers – tablets, handhelds, and so on – find adaptability and scalability for missions to be as important a requirement as lowering Size, Weight, Power, and Cost (SWaP-C). Meanwhile, embedded engineers continue to look for ways to get rid of the heat generated by high-performance processors.
Whether we’re talking about desktops, laptops, tablets, wearable systems, or handheld smartphones, military rugged computing platforms face continued requirements for lower Size, Weight, Power, and Cost (SWaP-C). Market and procurement pressures are also pushing for more Commercial Off-the-Shelf (COTS) designs that leverage commercial technology.
“In the rugged tablet world, SWaP-C is still important as customers want to manage weight and power with as much processing and memory as they can get,” says Steve Motter, Vice President of Business Development for IEE in Van Nuys, CA. “They are also looking for iPad-like or commercial tablet-like features in terms of touch screen, multi touch screens, swing bezels, and low weight. There is demand for lots of embedded peripherals and connectivity balanced with desire to support drop-in-puddle, submergible requirements. We are also seeing continued requirements for resistive touch or resistive multi touch for operators to be able to use tablets with a gloved hand. Tablets are growing fast, as people want to move the applications they would typically use in a desktop PC display to a mobile device. We need to ensure that the display is large enough (8 to 10 inches) to provide more information such as weather maps, video, and other interactive applications.”
“Generally in the mainstay computing world, we are seeing the push for the latest Xeon Sandy Bridge and Ivy Bridge series Intel platforms,” says Jim Shaw, Vice President of Engineering at Crystal Group in Hiawatha, IA. “In the embedded and wearable space, we are seeing a huge demand for lightweight but powerful systems. These are being applied to both the wearable computers and the Unmanned Aerial Vehicle (UAV) applications. Our most recent product offering in this market is an i7-3770S desktop quad-core plus hyperthreading CPU with 16 GB DDR3 in a 4 lb. computer for UAVs.”
Black Diamond Advanced Technology engineers in Tempe, AZ incorporated a power management capability into their wearable Modular Tactical System (MTS) for warfighters that can handle a wide voltage range, and “we utilize that in the computing element of the system,” says Norman Lange at Black Diamond Advanced Technology. “The system runs three boxes on one battery. We developed the power management system to get rid of extra batteries and use a single battery to pull in, regulate, and distribute power to multiple systems. Much like commercial smartphones, it reduces power consumption when certain functions are not in use or if the device is turned off.”
“The handheld device a lot of times tends to be an application-specific product, so it’s easier to scale processor and memory to the application with a margin for reserve or growth,” Motter says. “They do not need the fastest processor and most memory to do the job today, but want the ability to support future apps and customization. One thing about handhelds and ruggedization is that [they] will only have to handle what a human can handle as it is inhabited in the area end of a warfighter’s hand. It will not need to meet temperature ranges very far beyond that which a human cannot survive. Batteries and the dimensions of the unit are dictated by size of the display; for small displays (3.5-inch), the packaging is challenging; at a 7-inch size there’s more room for additional batteries and peripheral functionality.”
Warfighters also want computing tools they can scale and adapt based on their different missions. Each mission might also call for different SWaP requirements as well as different ruggedization needs. Therefore, rugged and wearable computer designers are designing modular systems that are flexible enough to meet a variety of mission and human factor requirements (Figure 1).
“The fastest growing form factor is not really a form factor. It is delivering the optimal size, weight, and power needed for the job,” says Mike Stelmat, Chief Technology Officer, Worldwide Product Sales, at General Dynamics C4 Systems in West Palm Beach, FL. “The smaller, the lighter, the more power efficient the computer, the better. Where I do see change is the need to mix and match options to deliver the right balance of ruggedness and functionality at the most competitive cost. That way, customers only pay for what they need to get the job done. Dismounted soldiers who need to text, chat, and maintain situational awareness during a mission need a lightweight, rugged computer that performs much like a smartphone, such as the GD300.” GD also provides rugged computers for intelligence analysts in mobile command posts who need full levels of processing power, memory, and information security, Stelmat adds. Earlier this year, the Army 75th Ranger Regiment in Afghanistan worked the GD300 and feedback was positive, he says.
The MTS is a completely modular approach to wearable computing, Lange says. “It is a modular wearable electronics platform that is optimized for dismounted precision targeting, command and control, C4ISR, Explosive Ordnance Disposal (EOD), and other dismounted missions that require a computing function. Black Diamond doesn’t really build computers; we build weapon systems, and our design staff consists of prior missile system engineers. We spent more money on human factors than any other design attribute of our system. Empirical end-user feedback was given directly to [the] designer. Unlike a traditional system where the designer writes a specification, then gets with [the] end user, we shortened that process by embedding our designer with Special Forces operators. They lived with the operator to get raw feedback, learning rapidly how the system needs to work in all conditions – rain, sleet, and mud – and with other equipment.”
MTS is super scalable, and users can adapt the system based on mission needs, Lange continues. “If an operator does need to call in airstrikes, he can scale it down to just have navigation and command and control functionality. The system has different elements such as a rugged monitor, a GPS module, and a tactical expansion hub. The tactical mission controller – worn on upper-rear vest panel or integrated with an assault/carry pack – contains the tactical computing core, system power manager, and peripheral controller, and can be integrated with a helmet-mounted display. A variety of Department of Defense (DoD) Special Operations Command (SOCOM) elements in the Air Force, Army, Navy, and Marines use MTS. Most have been Joint Terminal Attack Controllers (JTACs), EOD personnel, or operators controlling UAVs and Unmanned Ground Vehicles (UGVs). MTS is the Air Force Special Operations Command Battlefield Airman Program of Record.”
Getting rid of the heat
Dissipating the heat from today’s modern processors continues to be a challenge for military system designers. This task becomes more difficult as the military wants products in smaller and smaller packages, creating less room to move heat off the card or board.
“Getting the heat out of the latest embedded processors has always been a challenge for engineers,” says Rob Scidmore, President and CEO of Extreme Engineering Solutions (X-ES) in Madison, WI. “It is especially true for Intel processors and is proving to be a challenge with the latest Intel Core i7 processors. For the latest Intel Core i7 processors, we have [integrated] a new thermal technology that improves the heat transfer from the processor to the heat frame, and to the sidewalls of the chassis; this enables us to continue to support conduction-cooled applications up to and even beyond +85 °C rail within a 0.8-inch pitch slot while still supporting an XMC/PMC module on the single board computer.”
The credit-card sized Falcon rugged computer from Versalogic in Eugene, OR, uses a low-power Atom E6x0T processor, but still has thermal management built in to dissipate heat, says Gary Schultz, Director of Marketing at Versalogic. “After thermal modeling, much testing is done to ensure that the heat is going where it needs to go, at a fast enough rate, to keep the board functioning. Very specialized Thermal Interface Material (TIM), machined heat slugs, or heat plates (to maintain the flatness to match up exactly with the top of the processor and support chip) and spacers make sure it sits at exactly the right height (without crushing the CPU die); these are all combined to make what appears to be a very simple thermal solution.”
“We have been pushing the limits with our water-cooled systems for the GPGPU and high-power CPUs,” Crystal Group’s Shaw says. “Crystal has a water block assembly that cools five C2075 NVIDIA GPGPUs. Each GPGPU can dissipate around 200 W; however, we have increased the density from each GPGPU taking up two slots to requiring only a single slot.“
Liquid cooling is continuing to grow in popularity among military system designers. “The industry has been on the verge of embracing liquid cooling for a number of years at the box level (Figure 2),” says Michael Humphrey, Key Account Manager for Parker Aerospace. “Many have been reluctant to embrace a liquid approach and have tried to do as much as they could with air before moving to a liquid-cooling architecture. Companies will typically push the use of air as far as possible before switching over. Operating in harsh environments where shock and vibration as well as sand and dust are prevalent definitely adds to the challenge where fans are the critical component.”
“Once a customer has exhausted all the possibilities with air, many of them are entering new ground,” says Dan Kinney, Business Development Manager for Parker Aerospace. “There are two important characteristics that liquid cooling can enhance: heat density watts per centimeter squared and total density. Liquid cooling really helps customers deal with higher heat densities (that is, W/cm2) as well as total heat load (for example, taking a box from 600 W and now making it over 1 kW).
Parker Aerospace has developed a thermal approach called two-phase cooling that “takes advantage of the transition of a liquid to a vapor – latent heat of vaporization,” Humphrey says. “The energy – heat – consumed by this transition is carried away by the vapor to the heat exchanger where the heat is dissipated and the vapor returns to a liquid. Parker’s SprayCool chassis and two-phase cooling technology are being used by Sierra Nevada for the Army’s Helicopter Autonomous Landing System (HALS).”
“Two phase is an efficient way to pull heat off electronics,” Kinney says. “In very simple terms: When liquid becomes a vapor like boiling water on a stove, it can create good consistent temperatures. This method is ideal for radar applications for a couple reasons. When it comes to the thermal management system itself, the capacity of heat removal of a two-phase system translates into lower flow rates and smaller reservoir volumes, thus yielding a lower-weight solution when compared to traditional single-phase systems. Secondly, the electronics packages benefit from lower and more uniform temperatures, thus improving reliability – higher Mean Time Between Failure (MTBF) – and allowing the user to maximize performance. We’ve reached the waypoint in the system where primes are starting to look beyond the embedded box when it comes to designing a cooling architecture. It is the whole system, not just the compute engine, that needs to be cooled. It’s no longer about what is in the sealed system; the antenna and the sensor suite need to be cooled as well. Airframe designers understand this and see a proper thermal management system throughout the aircraft as a way to reduce weight, thereby reducing fuel costs.” (See the following list of rugged computing companies.)