May 10, 2011

Pentagon funded Aeros working on Rigid Aeroshell Cargo Airship

In 2012-13, Aeros plans to fly the Pelican, a 230-ft.-long, 600,000-cu.-ft. demonstrator for its rigid-aeroshell, variable-buoyancy (RAVB) technology. Inside the shell, comprising a load-bearing frame of carbon-fiber trusses covered by thin-gauge rigid panels, will be a membrane to contain the helium lifting gas. Inside that membrane will be pressurized pump-fed tanks. More helium under pressure in the tanks makes the vehicle heavier, and less makes it lighter.

UPDATE - the Pelican is in the final stages of assembly as of October, 2012.

Aeros of Montebello, Calif., founded by Russian-born Igor Pasternak, is now the sole-source supplier for a project called Pelican, funded via the Pentagon’s Rapid Reaction Technology Office

VTOL/Hover                       Yes
Payload                          60 tons
Speed Max                        120 knots
Speed Cruise                     100 knots
Operating Altitude               12,000 ft
Range at Maximum Payload         3,100 nm
Ton-Mile per Gallon of Fuel      23

The airship will be over three times as efficient as a C17 cargo ship but three times less efficient than a truck. It will be about three times faster than a truck (especially being able to fly in a straight line and over rough terrain).

C17 plane ton-mile per gallon                         7
Aeros Airship Ton-Mile per Gallon of Fuel            23
Rail fuel efficiency (Ton-mile per gallon)    156 to 512
Trucks                                         68 to 133

A C17 cargo ship can move 77 tons with a ton-mile per gallon of about 7

A 156 page of study of Rail and Truck Fuel Efficiency

Rail fuel efficiency has a much wider range, varying from 156 to 512 ton-miles/gallon, while truck fuel efficiency ranges from 68 to 133 ton-miles/gallon.

The initial Pelican is not designed to have a payload, but to demonstrate the aeroshell, the variable-buoyancy system (a test rig has been built under a Darpa contract) and a flight-control system that integrates aerodynamic, buoyant and thrust-vectoring effects to allow the craft to take off and land vertically and to hover. In later and larger versions, the variable-buoyancy system will allow the craft to load and discharge cargo without venting gas or needing external water ballast, while remaining heavier than air for stability on the ground.

The variable buoyancy system is expected to be more responsive than the air-filled ballonets that are used to adjust lift on non-rigid airships, which have to maintain forward speed or be moored at all times.

Some technologies needed for very large vehicles would be left to the second-generation RAVB test aircraft, a 440-ft.-long, 3.8-million-cu.-ft. vehicle with a 60-ton payload. Those features would include a combined diesel and gas propulsion system and the ability to superheat helium for takeoff. After takeoff, the helium would cool to ambient temperature and the vehicle would use aerodynamic and buoyant lift to cruise—80-100 kt. at up to 10,000 ft. Aeros has also experimented with techniques for extracting water from the engine exhaust to compensate for fuel use. (Superheating and water extraction were tried in the 1920s and 1930s but have not been used since.)

The 60-ton vehicle is unfunded, and a 200-ton, or even a 500-ton version is further in the future. Aeros says its vehicles will be able to transfer loads on and off ships and discharge without landing. The company argues that survivability may be better than some expect: The underside of the gas membrane is under no pressure, so will not leak much if punctured, and the hull structure is redundant and lightly loaded. Nobody expects these aircraft to fly into hot landing zones

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