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M A Y 2 0 1 4 | 4 1 WORK IN PROGRESS envelope to provide lift, but need ground crews and tethers to stabilize the craft. Newer "hybrid" helium airships feature aerodynamic lifting surfaces and require a runway for takeoffs and landings. But when either type is used to carry cargo, the load has to be compensated for during offoading by ballast, typically sandbags or sometimes water, to com- bat the static lift of the gas. Ballast ex- change management is diffcult and is the reason that large airships have never been successful cargo carriers. Paster- nak and his design team envisioned, instead, a rigid, variable-buoyancy air- ship, equipped with short side fns, ver- tical stabilizers and vertical takeoff and landing ability that requires no ballast. Although the DARPA military program ultimately ended, Aeros is endeavoring to build a feet of what are now called Aeroscraft for commercial cargo roles. Its half-scale prototype, Dragon Dream, has successfully passed several tests and lift- off demonstrations. Control of static heaviness Aeros thinks big: Even the Dragon Dream prototype is 266 ft/82m long with a wing- span of 110 ft/34m, and more than 50 ft/15.4m tall. But two mammoth cargo craft have been designed: One 550 ft/169m long with a wingspan of 177 ft/54.5m and height of 120 ft/37m, will carry 132,000 lb (59.9 metric tonnes) of cargo, and a second, larger craft that will haul 500,000 lb (226.8 metric tonnes). So what makes this concept, recog- nized by the U.S. Department of Defense and the U.S. Congress as worthy of fur- ther study, viable? That would be the cen- tral design element, Aeros' patent-pend- ing "control of static heaviness (COSH)" system. Similar to a submarine's buoy- ancy system, says Tim Kenny, Aeros' engineering department director, it fea- tures a pumping system that can capture the helium within the vessel's envelope and compress it inside numerous hold- ing tanks. When compressed, the gas becomes much heavier, and its contain- ment creates a partial vacuum inside the airship envelope. Air is permitted to enter that void and infate four large "expansion bladders" positioned along the vessel sides. The air inside the blad- ders plus the weight of the compressed helium causes a decrease in buoyancy, and the craft descends. When the helium is released back into the envelope, forc- ing the air bladders to empty, the airship ascends. Airship elevation is maintained and rate of ascent/descent is con- Trust in a trussed frame The airship's lightweight internal trusswork, shown here fully assembled, must support the airship's helium-management equipment, its cockpit, cargo, and cargo containment structures. Carbon fiber/epoxy tubes in a range of sizes are combined with aluminum tubing (future airships will incorporate all-carbon tubing). Tubes are connected with aluminum joints, and adhesive bondlines prevent galvanic corrosion. Aeros thinks BIG This artist's rendering shows a future, full-scale Aeroscraft offloading its cargo. The largest airship that the company has designed, thus far, could reportedly airlift a payload of up to 500,000 lb (226.8 metric tonnes). Source: Worldwide Aeros Corp. Source: Worldwide Aeros Corp. Source: Worldwide Aeros Corp. Dragon Dream Designed and built by Worldwide Aeros Corp. (Aeros, Montbello, Calif.), this half-scale Aeroscraft prototype features a unique helium management system that enables vertical takeoff and landing operations without ballast. The company envisions a fleet of cargo airships for commercial flights to locations inhospitable to conventional aircraft. 0514HPC WIP-OK.indd 41 4/22/2014 3:11:47 PM