WASHINGTON (Army News Service) -- The Army's next-generation combat vehicle will probably run on alternative energy sources and feature directed-energy weapons, advanced-composite armor and an active protection system, experts said Tuesday."There's a solid four years of analysis that has to occur" before decisions are made on procurement requirements, said Col. William T. Nuckols, director of the Mounted Requirements Division at the Maneuver Center of Excellence. Nuckols chaired a panel at the Association of the U.S. Army's Institute of Land Warfare "Hot Topic" forum focusing on Army ground combat platforms."This is not a short-term endeavor," Nuckols said. "This is a multi-decade effort to get us to the first unit equipped in 2035."But fielding the next-generation combat vehicle by then means major decisions must be made by 2025, he said, just eight years from now."We've got to provide some focus for our science and technology partners," he said, three of whom were also on the panel.SHAPED BY THREATSDr. John Gordon IV, a senior policy researcher for RAND Corp., said the threats facing combat vehicles in the future will shape the next-generation combat vehicle.The biggest threats to combat vehicles now are rocket-propelled grenades, armor-piercing-guided munitions known as APGMs, and improvised explosive devices or mines, he said."Non-state actors are heavily armed with these systems, as well as state-level opponents," he said.The penetrating power of shape-charged weapons have "increased dramatically," he said. Many now have tandem warheads to deal with things like explosive-reactive armor."Modern APGMs can go through a meter of armor plate after they blast through an explosive-reactive armor array," Gordon said. "That's pretty difficult to cope with."Cyber disruption and electronic warfare also pose significant threats, he said, adding that tactical nuclear weapons should not be ruled out either."The unfortunate reality is that, as we consider the middle-tier opponents, ... we can't ignore the possibility that nuclear weapons can be used," Gordon said.The Russians, especially, talk a lot about tactical nukes, Gordon said. He recommended that the military consider hardening future vehicles against electromagnetic pulse and biochemical threats.ALTERNATIVE ENERGY SOURCESThere are five major renewable energy sources, said John Paulson, senior director of engineering and project management for General Dynamics Land Systems."Wind, geothermal -- and, for the most part, solar -- really aren't practical in the combat vehicle role," Paulson said.That leaves biomass and hydropower as possibilities, he said.Biofuels offer a cheaper and readily available alternative to diesel or gas, he said. The Defense Advanced Research Projects Agency is currently experimenting with algae to produce biofuels.Hydrogen fuel-cell technology is available now, he said, but it's dense. Hydrogen fuel cells today would need to be two or three times the size of diesel fuel tanks."Fuel cells coupled with other technology, like high-capacity batteries" might be able to energize weapons like lasers, he said.Fuel cells can also be coupled with diesel to save money on fuel and decrease the logistics footprint on the battlefield, he said. And electric energy from braking can also be stored in capacitors and re-used.A turbocharger can also recover waste energy from the exhaust system, he said. This technology is currently being used in Formula One racing cars. Electricity can be generated from the expanding exhaust fumes, and heat loss from vehicles can also be converted to energy."The big advantage of electric drives," Paulson said, "is we'll be able to supply more power to combat vehicles to support future weapons like high-intensity lasers, rail guns, or active protection systems and improved situational awareness electronics."360-DEGREE PROTECTIONWhile laser technology is emerging for weapons, Dr. Bryan Cheeseman said more research must be conducted on using directed-energy for vehicle protection. Cheeseman is the team leader of the Material Manufacturing and Technology Branch, Army Research Laboratory.Vehicles of the future will need 360-degree protection, he said. Threats from above could come in the form of unmanned aircraft; threats on the side from conventional weapons; and threats underneath from IEDs.Active protection systems could detect and destroy incoming rounds, he said. Additionally, more science and technology focus should be aimed at using directed energy as force-field-type protection.Many advanced-composite materials are being looked at for armor protection, he said, adding that nanotechnology and nano-grain metals are also possibilities.External suspension is another technology that can help protect against underbelly blasts, he said. Hydro-mechanical and hydro-pneumatic suspension are among them."From an underbody perspective, we can say we can mitigate a large portion of the threats that are out there," Cheesman said. But that comes with more weight and cost.THE WAY AHEADWhile specific details are still being developed for the next-generation combat vehicle, panel moderator retired Brig. Gen. Thomas Goedkoop, vice president of Booz Allen Hamilton, expressed hope that the panel had shed light on what the future could hold."What is the next-generation combat vehicle?" Nuckols had asked, up front.The next-generation combat vehicle could be a single combat vehicle that replaces the Abrams tank, the Bradley and even the Stryker, he said. "We don't know yet." It could be a family of vehicles similar to the original Future Combat Systems program.Future Combat Systems was the Army's primary modernization program from 2003 until May 2009, when the vehicle-development portion of the program was dropped and the network portion became part of the Army Brigade Combat Team Modernization Program."We're trying diligently to pay attention to [Future Combat Systems] and the lessons learned from that," Nuckols said.