Despite the high cost of powering cargo freighters, it doesn't look like viable alternatives are appearing anytime soon. Instead, the enormous ships  are increasingly turning to innovative ways of lessening fuel consumption. One promising possibility is massive sails—kites really—that can be retrofitted onto ships and aid in propelling them across the ocean. Earlier this month, Beluga Shipping christened its  MV "Beluga SkySails"—a cargo ship with a 520 square foot propulsion kite; the first to utilize the system. A transoceanic voyage  is imminent, but  unfortunately for PPX buyers, the  date has been pushed from mid-December to January.  Most traders guessed correctly, however: The SKYSAIL stock (Will the sail-assisted Beluga freighter depart by December 20, 2007?) was halted at $35.75 and closed at $0.—Abby Seiff

In PopSci's May 2006 feature "Welcome to the New Age of Sail," we present three novel designs for systems capable of reducing the amount of fuel used by big ships by up to 35 percent. One of these is the SkySail, a huge kite that can be retrofitted to existing ships to help pull them across bodies of watersort of an environmentally savvy version of the tugboat.

Click here to see a video of the SkySail system in action (Windows Media Player required).