Lockheed Martin to develop stratospheric airship fabric

required 500 miles of new roads to be built and further 500 miles of roads to be repaired so supplies could reach the pipeline. The design principle of airships makes them ideal for carrying heavy loads. Doubling the length of an airship increases the surface area — and the weight — of the ship by a factor of four, but the volume, and hence, the lifting capacity, increase by a factor of eight.

These design principles have not always been easy to implement. A German company called CargoLifter closed its doors in 2002 after it failed to develop a heavy-lifting airship which would be commercially viable. In April 2004 DARPA initiated a program to develop a heavier-than-air, intercontinental airship capable of rapidly transporting military men and equipment to a war zone. The plan, designated Walrus, was launched with a $6.3 initial funding and called for a fleet of airships capable of transporting upward of 500 tons of cargo 12,000 nautical miles (about 10,000 miles) in 4 days (by way of comparison: A standard C-130 cargo plane can carry about 22 tons). The airships are called by the plan to be able to carry sufficient supplies to sustain the force for at least seventy-two hours.

The Walrus would be of a hybrid design and resemble a flat, lozenge-like lifting body. The design would allow the Walrus to not only derive lift from the helium gas, but from the aerodynamic forces generated as it moves through the air. The Walrus will be powered through the use of thrust wings (TW), which are articulated lifting surfaces with internal thrust producing engines. The TW would be grouped in pairs, fore and aft, and would consist of several independent modules arranged on a single axis. The TW modules can be rotated along this axis to provide 360o of vectored thrust. This would enable some of the TWs to be angled vertically to provide for thrust-based lift, and some of them to be angled horizontally to provide aerodynamic lift. Once the Walrus reaches cruising altitude, the TWs could all be aligned horizontally to provide forward motion and aerodynamic lift. The thrust wings would also eliminate the need for the Walrus to take on ballast to compensate for static gas lift when clearing the landing zone, or when “deadheading” back for additional cargo.

Some analysts say that the Pentagon’s goals for the Walrus are too ambitious, and that the ability to carry 75 tons and travel up to 500 miles would be more realistic. Philippe Lopes of Arlington, Virginia-based BMT Syntek says that these more modest airships would cost about $50 million each. In any event, the Walrus’s future is in doubt. The mounting cost of the war in Iraq moved DARPA in April to suspend further spending for the program. When, in August, the preliminary studies for the program were completed, Walrus shut down.

-see this DARPA document; Aeros Web site]; this Military.com ; this Military.com discussion

The Dynalifter
Talking of a hybrid design, we should note the interesting design work of Brian Martin and Robert Rist. They have designed and produced a prototype of the Dynalifter, a 117-ft long hybrid which has been taken on several test flights. The Dynalifter’s main wings provide about half the lift, with eight Pratt & Witney 127 turboprop engines; small wing surfaces near the nose provide additional lift and maneuverability. The most innovative feature of the Dynalifter, and what distinguishes it from more traditional designs, is an internal structure resembling a cable-stayed bridge. Most rigid airships rely on a lattice of aluminum girders, but the Dynalifter has a neutral beam running the length of the ship. The beam is made of composite materials and is supported by cables strung from three mid-ship towers. The towers rise from the central part of the neutral beam and support the cargo bay, wings, and landing gear.

-read more in Jeff Wise’s Popular Mechanic article

Aeros Walrus early concept design