Energy-Efficient Technologies for the Dismounted Soldier (1997)

This chapter summarizes the committee's main conclusions from its study of energy-efficient technologies and the Army's plans for the dismounted soldier. On the basis of each conclusion, the committee makes specific recommendations to meet the power requirements of dismounted soldiers.

Conclusion 1. The power requirements of the Land Warrior system will limit the effectiveness of dismounted soldiers on the digitized battlefield.

This study has shown that the Land Warrior system is far less energy-efficient than it could be. It will fall short of meeting the needs of the digitized battlefield principally because of excessive energy demands for computation and radio transmission. The Land Warrior program is on a course to field subsystems that are heavier, bulkier, and less functional than they would be using state of the art consumer technology. This is because the Army has failed to address energy efficiency in system and subsystem designs. The Land Warrior program provides for the incorporation of advanced technology, but the scope of necessary enhancements will require special funding and command emphasis by the Army.

Army developers of the Land Warrior system and its predecessor systems used energy consumption characteristics to allocate energy and to match energy consumption with battery capabilities. Energy efficiency, however, was not used as a defining requirement for specifying subsystems or for measuring the performance of Army contractors. To meet the requirements of the dismounted soldier, the energy consumption of human-portable systems will have to be stressed at every stage, from the determination of operational requirements to the design of microprocessors and computer and communications architectures.

Commercial equipment is available with the energy efficiencies the dismounted soldier needs. The Army cannot continue to rely primarily on improvements in energy storage, which only mask equipment inefficiencies. A coherent approach to prevent the problem from growing to crisis proportions will require concerted efforts by both the Army Acquisition Executive and the Army Materiel Command.

Recommendation 1a. Army leadership must emphasize the importance of reducing energy demand to achieve energy sufficiency for future dismounted soldiers. Meeting near- and far-term needs will require major changes in Army thinking. Paradigm shifts in energy strategy, system design, and the use of commercial technology are absolutely essential to avert a crisis. The new paradigms must be translated into top-down initiatives. Essential reforms include changes in the following areas:

• Energy Strategy. The Army must focus on energy consuming systems as well as on energy supplying systems.

• System Design for Efficiency. The Army must emphasize system integration at all levels so that the entire system can be optimized for energy efficiency. For example, modular hardware designs with dedicated processors are more energy-efficient than general-purpose computers. And communications architectures must be designed to distribute energy consuming components (sensors and processors) where they can most easily be served by local power sources.

• Use of Commercial Technology. Army systems must be closely coupled to the technologies used in commercial products. The Army must be fully capable of incorporating the most recent data-processing and communications technology into its systems.  

Recommendation 1b. The Army should accelerate the development and insertion of enhancements to the Land Warrior system, focusing on improvements to the computer/radio subsystem, because the estimated power requirements for communications and computing functions in Land Warrior are clearly excessive.

Recommendation 1c. The Army Acquisition Executive should make energy efficiency a priority consideration in evaluating contractor performance in future procurements of electronics for the dismounted soldier.

Conclusion 2. Advanced fueled systems and energy-efficient technologies are both necessary to achieve energy sufficiency for soldiers in the Army After Next time frame.

Dramatic improvements in the energy efficiency of systems for the dismounted soldier are already available as a result of advances in low power electronics and commercial consumer technologies. Reducing energy consumption will mean that available energy sources will be able to support longer missions, using smaller and lighter energy sources, and that new functions can be added to increase the soldier's capabilities. Paying attention to energy consumption through equipment design, as well as increased awareness and enforcement of

power discipline, will also yield ancillary benefits, including lighter components, reduced susceptibility to detection, lower cooling requirements, and simplified logistical support. These dramatic improvements, combined with limited increases in the specific energy of sources and improved storage capabilities afforded by advanced fueled sources, will make energy sufficiency possible for dismounted soldiers in the Army After Next even for the most problematic requirement, microclimate cooling.

Recommendation 2a. To achieve energy sufficiency, the Army should set research objectives that focus on energy-efficient technologies. Energy efficiency is the key to success for the Army After Next.

Recommendation 2b. The Army should support use of computer-aided design tools for systems and integrated circuits specifically optimized for low power performance. If the necessary design tools are not available commercially, the Army should support its own development programs, perhaps in conjunction with related DARPA efforts. Army contractors for electronic systems should be required to use energy-optimizing design tools.

Recommendation 2c. The Army should support the development of mission-specific software for dismounted soldier systems. General-purpose software is wasteful and not energy-efficient.

Recommendation 2d. The Army should support the development and use of low power software, in which each instruction is written or compiled to minimize power requirements. New tools may be required for specific military applications.

Recommendation 2e. The Army should use dedicated electronic circuits wherever possible to minimize power requirements. Application-specific integrated circuit (ASIC) technology can achieve the efficiencies of custom circuits and hardware and still be cost effective.

Recommendation 2f. The Army should establish and enforce standards of awareness and discipline for energy consumption in dismounted soldier operations.

Conclusion 3. Access to commercial technology must be improved.

The Army will not be able to meet the goal of digitizing the battlefield unless it improves its ability to adapt and benefit from commercial consumer technology. Subsystems in the Land Warrior system, for example, will be obsolete compared with commercially available consumer electronics before the system is fielded. Military radios that meet the strict definition of commercial off-the-shelf

equipment in most cases are not built to the same energy efficiency standards as consumer electronics. The fact that Army developers or suppliers of military electronics also develop, produce, and market consumer electronics is no guarantee that advances in consumer electronics will be carried over into military systems. The committee found that the consumer and military business units of large corporations are substantially and deliberately isolated from each other and that technology used in military systems sometimes lags substantially behind the technology in consumer systems produced by the same company.

The Army, through the science and technology insertion component of the Land Warrior program, recognizes the need to build flexibility into the process for acquiring advanced technology. Institutional provisions for experimentation, such as the Advanced Warfighting Experiment at Fort Hood, and spiral developments providing for continuous design feedback, can accelerate the incorporation of applicable technologies.

Recommendation 3a. Army procurement strategy should include provisions for keeping pace with advances in the semiconductor industry. Even if it is fielded in increments, state-of-the-art technology should be fielded in small quantities so that systems can be upgraded frequently. In addition to requiring energy-efficient technologies, Army design and procurement contracts should require contractors to adopt improved technology automatically as it becomes available.

Recommendation 3b. The Army should support efforts to maintain the pace set by the National Technology Roadmap for Semiconductors. The road map is a key means of ensuring continued superiority in electronics technology by defining critical technology areas and research gaps that may stand in the way of needed breakthroughs. The Army should:

• Use the road map to project technology availability in specifying new systems.

• Support research and development in industry and universities in areas identified as critical in the road map.

• Contribute to the road map, either directly, through U.S. Department of Defense representation on the road map committee, or indirectly, through other members, such as representatives of the national laboratories.  

Recommendation 3c. The Army should develop an effective strategy for keeping abreast of state of the art consumer product development and for specifying low power performance criteria in its solicitations. The Army should emphasize participation in consumer-oriented electronics industry activities that focus on low power electronics, such as conferences, symposia, and focus centers, as a way of raising awareness and expectations of energy-efficient performance. Only through participation can the Army keep abreast of technology development and, more important, influence industry priorities.

Recommendation 3d. The Army must experiment continuously to keep pace with the development of commercial equipment. Simulations should be used to determine the value of trade-offs between improvements in energy consumption and less essential equipment characteristics.

Conclusion 4. Wireless transmission will dominate energy demand in future dismounted soldier systems.

If the Army can take advantage of trends in commercial consumer electronics, the power requirements of computers, sensors, and displays for the dismounted soldier will fall to nearly negligible levels. Subsystems that perform these functions could consume less than 1 W of electricity by the year 2015. Energy needed for radio transmission will then dominate the power requirements for successor Land Warrior systems.

The cost of transmitting information, measured in terms of energy, depends largely on the range and frequency of transmissions. Video communications, which are emphasized in the Army's plans for digitizing the battlefield, are particularly demanding in terms of both bandwidth and distance. By adapting commercial communications equipment, the efficiency of DC-to-RF energy conversion can be increased from the range of 20 to 40 percent to the range of 50 to 70 percent in the foreseeable future. Communications architectures and protocols optimized for energy will yield even greater improvements.

Recommendation 4a. The Army should refine its requirements for high-resolution images and video communications to the minimum necessary to meet battlefield needs.

Recommendations 4b. The Army should minimize wireless data transmissions by reducing the time required to convey a given amount of information. Relevant technologies include speech and image compression, database caching, and information science technologies that reduce, eliminate, or automate the energy inefficient natural language (read message) transmissions that are currently used.

Recommendation 4c. The Army should adapt the hierarchical network architecture of cellular telephones to create a ''virtual peer-to-peer" network, which would improve the distribution of computational resources while taking advantage of commercial cellular technologies.

Recommendation 4d. The Army should modify and synchronize operational doctrine with emerging systems to minimize soldier transmissions. For example, data collection and reduction should be performed as close to the data collector as possible, and computational components should be distributed across the network of soldier communicators. The Army should exploit energy saving communications protocols, such as the protocols used to alert radio receivers to incoming

data in pagers and cellular phones. Other commercial techniques should be incorporated doctrinally to reduce or eliminate the operational demands on transmit energy.

Recommendation 4e. The Army should study alternatives for the military network design to optimize power consumption. For example, it should investigate the use of commercial low-orbit satellite systems and unmanned aerial vehicles as relatively energy-efficient alternatives that may also provide high-bandwidth capabilities.

Conclusion 5. Research to improve energy sources must continue.

Improved energy sources, with higher specific energies and better performance characteristics, will be important to the dismounted soldier because the proliferation of new electronics-based systems will continue. Unlike commercial investments in microelectronics and communications technologies, commercial investments in power sources and systems technologies will probably not be sufficient because the military market is small. Therefore, military research and development will still be needed.

In the near term, the dismounted soldier must rely on both nonrechargeable and chargeable batteries for power. But batteries will not suffice for missions that require more than a kilowatt-hour (about 20 hours using the initial Land Warrior system). For high energy (long mission time) requirements, fueled systems (generally, combinations of rechargeable batteries or capacitors charged by fuel cells or other fueled energy sources) can offer specific energy an order of magnitude higher than the best battery at relatively small development risk. Hybrid systems will make it possible to optimize performance for both high power and high energy requirements.

Recommendation 5a. For the near term, the Army should continue to support research and development on rechargeable batteries with specific energy higher than 200 Wh/kg.

Recommendation 5b. The Army should continue research into fueled energy sources and high-performance capacitors for use in hybrid energy supply systems for the dismounted soldier. It should develop prototypes of the most promising ones for field trials within the next decade.

Recommendation 5c. The Army should continue research for the far future across a broad range of technologies, including advanced fuel cells, microturbines, and thermophotovoltaic converters.