Spy Blimps Revisited: A Performance Comparison between Two Competing Approaches

摘要

While operational airships globally number in the low dozens, interest in buoyant or semi-buoyant platforms continues to arouse imaginations of commercial and military planners and developers alike. The airship-as-advertisement business model is the only model that has proven sustainable on any scale since the crash of the initially successful LZ-128 Hindenburg effectively ended regular passenger and cargo transport by airship, and the 1962 termination of the US Naval airship program terminated regular large-scale surveillance from airships. Efforts in the US and Japan during the 2000's to have a self-sustaining sight-seeing business model using the modern semi-rigid Zeppelin NT both failed. In theory, the buoyant nature of airships provides compelling endurance and cost-per-ton-mile capability which fills a niche arguably not currently occupied by other modes of transportation. The potential endurance capability motivated the US Military to fund two nearly-simultaneous airship surveillance programs in 2010. Having similar missions, the primary differentiator between the two programs had to do with choice of basic hull form. The Army's Long endurance Multi-Intelligence vehicle was to be a lifting-body semi-buoyant “hybrid” vehicle. The Air Force's Blue Devil Block 2 was to be a conventional ellipsoidal airship. The author's pre-contract-award 2010 paper compared the loitering performance of the two platforms using a basic mission simulation, giving the nod to the conventional ship. This study revisits the basic assumptions of the simulation in view of new publicly available aerodynamic information, and revises the results, finding the hybrid to be the superior option.