Keeping an army provisioned in the desert is a ballet of logistics, particularly when it comes to supplying two vital liquids: diesel fuel and water. Now, using technologies developed for the space program, the U.S. Army is conducting an experiment that could convert the exhaust pipes of military vehicles into water fountains. Later this month, United Technologies Corp.'s Hamilton Sundstrand unit will deliver two military Humvees to the Army for three months of testing at the Aberdeen Proving Ground outside Baltimore. Built into each vehicle's truck bed is a complex system that can recover water from engine exhaust, purifying as...