GPS bringing COTS to the guidance busines

Jan. 1, 1998
The Global Positioning System is creating a revolution in the way engineers develop guidance systems for missiles and other so-called "smart munitions," which is adding to the momentum of GPS in military and civil navigational applications.

GPS bringing COTS to the guidance business

The Global Positioning System is creating a revolution in the way engineers develop guidance systems for missiles and other so-called "smart munitions," which is adding to the momentum of GPS in military and civil navigational applications.

By John Rhea

Given their uniquely military character, embedded guidance systems for missiles and other smart munitions would seem to be among the least likely candidates for dual-use and commercial off-the-shelf (COTS) technology insertion. Yet one increasingly pervasive technology is changing that picture: the satellite navigation system known as the Global Positioning System, or GPS.

Experts in the U.S. military services originally conceived the GPS to move and track their deployed forces quickly and efficiently. A variety of commercial industries, however, were quick to exploit this new navigation and positioning technology, which also can track speed and altitude.

GPS is changing how fighting forces in the field will guide weapons to their targets in the future. The list of applications, by no means all-inclusive, embraces precision-guided munitions, missiles of all kinds, torpedoes, and even unmanned vehicles.

GPS alone cannot do the whole job, and this is where COTS comes in. Military leaders demand a high probability of mission success, so GPS must team with inertial measurement units (IMUs) to enhance accuracy in all operating environments. COTS offers the electronic systems designer tremendous advantages in cost savings and reliability - initially at the integrated circuit level, and ultimately at the printed circuit board level.

The good news is that GPS chipsets are becoming ever-more-proven technology - particularly with the growing number of civil GPS applications - pushed by swelling sales volume and the resulting economies of scale. In fact, GPS chipsets are being routinely fabricated by what one observer calls "the plain vanilla CMOS [complementary metal oxide semiconductor] process." Despite their military heritage, these are the ultimate COTS parts, and they are universally available from a large number of merchant suppliers at prices approaching those of the electronic innards of digital watches.

The IMU part - which historically has consisted of a spinning-mass, laser, or fiber-optic gyro - is rapidly catching up, thanks in large measure to the micro-electromechanical systems (MEMS) development program that has sponsorship from the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va.

DARPA`s MEMs program, which is driving the technology of micromachined components, enables systems to perform such traditionally electromechanical tasks as motion sensing with silicon rather than by cumbersome moving components. Motion sensing traditionally has been the domain of accelerometers.

Scientists working with the British army, for example, are developing a guided mortar round that senses motion with two accelerometers integrated on a chip with a few moving parts. The chips cost about $15 apiece and replace $500 to $1,000 worth of electromechanical parts.

Even better news for military and aerospace systems designers is the growing demand for accelerometers on a chip within the U.S. automotive industry. Automotive electronics designers are no strangers to building and specifying ruggedized parts for demanding operating environments, and are voracious customers for on-chip accelerometers for such applications as air bag deployment and anti-skid braking systems. On-chip accelerometers for these uses are running about five dollars each.

Where is all this leading? James Doscher, marketing manager for micromachined products at Analog Devices Inc. of Wilmington, Mass., says he expects this trend to sweep the aerospace industry over the next three to five years.

Doscher says he expects IMU chips teamed with GPS chipsets to replace moving parts in a growing number of systems designs, which will include the necessary digital signal processors (DSPs). However, he cautions that these will be "separate chips, now and in the future ... because they use different semiconductor processes."

The ultimate goal - "the holy grail for the mil-aero business," as he puts it - is six degrees of freedom on a chip. "We`re heading in that direction, but it`s five to 10 years away, closer to 10." Doscher`s business card identifies him as a "Micromachining Evangelist."

In the meantime, military systems designers are moving cautiously toward the guidance system of the future by reconfiguring existing systems with the best legacy components. Russ Adamchak, Navy and intelligence sector manager for the Mercury Computer Systems office in Vienna, Va., cites the Navy`s Lightweight Hybrid Torpedo (LHT) program, where the idea is to create a common guidance system for the Mk 46, 50, and 48 ADCAP torpedoes using the readily available Texas Instruments 320C40 DSP plus some new "glue code" software and algorithms for shallow-water operations.

LHT illustrates Adamchak`s differentiation between COTS at the chip level and at the board level. COTS at the chip level, he says, is readily available from merchant suppliers in non-proprietary parts, including those meeting military specifications. COTS at the board level, on the other hand, is still constrained by form factors and environmental considerations, he says. LHT is "above the dual-use line" - and therefore not truly COTS - because of its requirement for conductive cooling, Adamchak claims.

"This area is just starting to emerge as a business opportunity," he says. "ASIC [applications-specific integrated circuits] technology development has done a lot to facilitate that."

Engineers at Raytheon TI Systems (formerly Texas Instruments Defense Systems & Electronics) in Lewisville, Texas, who are in the engineering and manufacturing development phase of the Navy`s EX171 Extended Range Guided Munition (ERGM) program, seek to apply the technology to a new class of guided projectiles that would replace missiles entirely.

At a recent company-sponsored technology briefing, Raytheon TI Systems experts claimed that in the future almost any mission assigned to missiles could be accomplished with a guided projectile. In support of this claim, company experts list six supporting technology trends:

(1) target-looking autonomous seekers using non-cryogenic imaging infrared seekers, solid-state millimeter wave radar, and LADAR technologies;

(2) hypersonic apertures for imaging seekers;

(3) air-breathing propulsion for extended cruise at high supersonic velocities and extended ranges;

(4) flexible weapon configurations that mate segments together in the gun tube via snap joints, allowing "mix and match" configurations to tailor projectiles on a mission-to-mission basis;

(5) flexible payload configurations that minimize the time and expense to develop new versions of a guided projectile; and

(6) lower unit costs as commercial markets drive the cost of GPS receivers and micromachined silicon inertial sensor components to ever lower costs.

Specifically, Raytheon TI Systems officials maintain that guided projectiles can be priced as low as $5,000 to $20,000 (plus the cost of the warhead) and that military leaders can deploy more of them where they are needed. Although in the case of the ERGM, range is limited to 63 nautical miles, Raytheon TI officials cite studies for the Next Generation Naval Gun project that show that 500 to 700 guided projectiles and a complete gun system would take up the same space on board a ship as 64 vertical missile launchers.

Another growing application is helicopters, which pose particularly stringent guidance requirements. An immediate problem is their mode of operation, which produces high vibration levels that can literally shake the electronics equipment to pieces. This demands a ruggedized chassis to protect the signal processors in the so-called armadillo approach, where rugged enclosures sufficiently protect non-ruggedized components from vibration and shock.

Mission requirements pose additional constraints. Since the purpose of helicopters in tactical operations is to fly a nap-of-the-earth profile to avoid enemy detection, using radar-based navigation systems can be not only self defeating, but also inaccurate.

Enemy surveillance equipment often can easily detect radar signals, and the need for helicopters to dart in and out of valleys during nap-of-the-earth operations can limit their ranges of operations when terrain blocks the radar signals.

For the U.S. Army Sikorsky UH-60 Blackhawk helicopter, designers at Systran Corp. in Dayton, Ohio, developed a COTS computer-based guidance system that blends GPS and IMU subsystems with an existing military digitally mapped terrain database in combination with a guidance algorithm to keep the pilot on a safe flight path.

The system combines a virtual reality-inspired pilot headset, Silicon Graphics workstation for visual display, and a Motorola 68020-based multiprocessor with a VME backplane for number crunching on the digital database. A 1-inch monocle display in the pilot`s headset shows a computer-generated safe course.

Systran experts got involved in the project to develop a network within the computer that could meet the Army`s requirement to update the computer- generated flight path 20 times a second for the pilot`s monocle. Army officials originally tried an Ethernet network, but that was not fast enough and they turned to Systran`s SCRAMNet.

Another problem was the UNIX operating system for the VME database computer. This was a master/slave configuration with the master using UNIX and the slaves running in real time. The UNIX system could not keep up with the real-time processors, so Systran engineers redesigned the network so that all nodes have identical computer-addressable memories. Changes at one node are repeated at all nodes in microseconds so that the entire network appears as a single "virtual computer."

Designers at Vista Controls Corp. of Santa Clarita, Calif., are also combining GPS and IMU in a two-slot VME configuration. Richard Copra, vice president for marketing at Vista, says he is convinced this is the way the industry is going. "The magic of GPS has changed the way navigation systems are designed forever," he proclaims.

Vista`s VME unit is called Navigator. It is part of the company`s Score series of RISC-based embedded controllers, aimed at retrofit and upgrade programs where "putting navigation requirements in the box" enhances system performance, Vista officials say. It uses the AMD 29050 RISC processor and comes in three models: 0-55 degrees Celsius for developmental work and in two -40 to 75 C versions for operational applications, one with forced-air and the other with conductive cooling.

This is typical of the new breed of GPS/IMU guidance and navigation systems that provide either the standard accuracy of 16 meters for non-military applications or 1-meter accuracy using differential GPS.

There is a storm cloud on the horizon, however - the accuracy issue. If this new generation of guidance systems is to achieve true dual-use technology status, designers must find a way to get more participation by commercial and general aviation and thus create a viable customer base.

To quote a saying from the advertising industry, the dogs aren`t eating the dog food. Dave Steigman, senior analyst at the Teal Group, a consultancy based in Fairfax, Va., points out that leaders of the commercial airlines (including the air freight industry) are upset about not being able to receive the more accurate differential GPS signals. "Ten meters is not good enough for safety, particularly for landings," he says.

In fact, officials of the commercial aviation industry want the benefit of spinoff military technology, Steigman adds, and he cites the growing acceptance of "glass cockpit" technology based on head-up displays originally developed by the military.

Leaders of Alitalia and Delta Airlines have already approved this concept for all their new aircraft, and subsidiaries of Lufthansa and British Airways are considering this upgrade. Aircraft builders are also planning to make glass cockpits optional equipment on their new models, Boeing on the 777 and Airbus on the A-320 and A-330.

Kim Fowler, technical marketing manager at Ixthos Inc. in Leesburg, Va., says leaders of his company looked into guidance systems for general aviation a couple years ago, but decided the market was not sufficiently developed. Based on work done by scientists at the Applied Physics Laboratory of Johns Hopkins University in Baltimore, Ixthos officials did preliminary design on a battery-powered system using a single DSP in a small box that could serve as a backup to the primary guidance and navigation system.

A far more promising market, according to Fowler, is the emerging use of unmanned aerial vehicles (UAVs) for military applications that are still being defined. These are likely to be more complex than those of current weapons platforms and will rely on distributed sensor suites that require more multiprocessing DSP power, the company`s specialty.

Fowler cites synthetic aperture radar and video data, plus terrain mapping to correlate military operations with positions. On top of these already demanding applications Fowler says he sees even greater DSP needs generated by sonar and medical imaging, which he says will need hundreds of processors working on the data.

The situation today is not exactly one DSP per sensor, but rather several streams of data pouring into a DSP, Fowler says, but the flow rate is bound to increase, which means the DSPs will have to keep pace. In the case of the demands experts say UAVs will create, he says it is time to prepare for requirements three to five years down the road.

In addition to guidance and control applications, designers who are developing the new technology are applying it to the safing and arming function of munitions. Army officials, for example, are working on a way to assure that Hellfire missiles do not arm until they are at least 1,000 yards away from the launching aircraft. This is to prevent a premature explosion of the warhead that could kill the aircraft crew.

With all the potential military and non-military applications coming on line, there should be something in the technology base for all the users, depending on their needs for accuracy, says John Hartman, defense business development manager at Analog Devices. It is simply a matter of how much new users are willing to pay. A rule of thumb is that the span is about an order of magnitude in both cost and accuracy from the "bleeding edge" technology of precision-guided weapons to their commercial equivalents.

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Solid-state inertial measurement units such as the accelerometer pictured above from Analog Devices Inc. of Wilmington, Mass., are expected to decrease electronics size and weight while enhancing the accuracy of future precision-guided munitions.

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Designers at Systran Corp. in Dayton, Ohio, developed a COTS computer-based guidance system that blends GPS and IMU subsystems with an existing military digitally mapped terrain database in combination with a guidance algorithm to keep pilots of the U.S. Army UH-60 Black Hawk helicopter on safe flight paths. Pictured above is the U.S. Navy version of the aircraft, the twin-engine SH-60 Seahawk.

The case for precision-guided weapons

Engineers from Raytheon TI Systems in Lewisville, Texas, assessed the overall political climate in making their case for the Extended Range Guided Munition projectile they are developing for the U.S. Navy, and concluded that a shift away from traditional tactical operations - made possible by the emerging electronics technologies - would be required in the new international climate. Company leaders make four points in support of their position.

1) Smaller and lighter forces: Although the U.S. armed forces are shrinking, their mission responsibilities continue to increase. This is true not only for conventional warfare, but also for contingency operations and what are becoming known as "operations other than war."

Lighter forces that are quickly deployable, flexible, and can tailor their response to the particular situation are essential elements of the future military force. In the case of guided projectiles, they can strengthen the punch and increase the flexibility of artillery forces ranging from ships supporting land operations to helicopter-deployable toed howitzers.

(2) Faster operational tempo: Modern combat theories include forcing a fast operational tempo while simultaneously denying the adversary the information and communications channels he needs to respond to that tempo. The idea is to turn inside an adversary`s decision loop to give allied forces a decisive advantage. Because precision weapons offer military leaders a greater selection of targets than they have today, a given number of warheads can produce more target kills in a given time than the same force armed with conventional weapons.

(3) Expectations of lower combat losses: The success of the coalition forces in the Persian Gulf War contributed to the shaping of current public opinion that demands low casualty levels in future engagements. Guided projectiles can meet this requirement. Since they fly non-ballistic trajectories, they make it difficult for counter-battery radars to backtrack and thus locate the firing point. also, because they are more accurate than unguided projectiles, they reduce the fratricide rate.

(4) Lower tolerance for collateral damage: Collateral damage, either in terms of dead civilians or non-military property damage, is no longer tolerable, particularly in contingency operations and operations other than war. The accuracy of precision weapons and the ability to tailor their trajectories allow specific targets to be attacked even in highly populated areas with reduced risk of collateral damage. -J.R.

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Future guided smart munitions such as the Navy EX171 Extended Range Guided Munition program from Raytheon TI Systems is to blend a variety of navigational sensors to increase precision and lethality.

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