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First-Order Sizing Study to Support the DARPA Proposal for High-Altitude,
Large-Aperture Antenna Vehicle, 15-9505

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Principal Investigators
Steve Smith Jr.
Tommy Lew
William Perry

Inclusive Dates:  09/27/04 – 01/27/05

Background - There has been a resurgence of interest concerning stratospheric balloons and airships by both commercial and government sectors since the September 11th attack on the United States Requirement drivers are for "persistence," field of view of observational assets and the ability to remotely sense, detect, and correctly identify information from various concealed or camouflaged aerial, surface, and subsurface assets. Observation of assets of interest (i.e., weapons caches, underground facilities, and so on) is often difficult because the assets are: 1) transitory in nature, 2) cleverly disguised from observation by some type of cover, 3) hidden temporally from our often-transitory or predictable observational assets, or 4) undetectable by our orbital assets because of their very weak signal strengths. A platform was desired that has persistence, large field of view, and the ability to penetrate cover.

Approach - The technical approach for the High-Altitude, Large-Aperture Antenna Vehicle (HALAAV) was to develop first-order structural, thermodynamic, propulsion and an atypical, ground-penetrating radar, using a high-gain antenna hull configuration. The models were then integrated into a general-system model that included the flight vehicle, support systems, and antenna section. The HALAAV was scaled for varying aperture sizes for a 100-kilogram payload section and a flight altitude of 22 kilometers.

Accomplishments - A first-order HALAAV sizing tool has been developed. The HALAAV structure consists of: 1) a saucer-shaped antenna hull with the upper half serving as an inflated metallized membrane antenna reflector and 2) an inflated, composite membrane toroid. Three HALAAV design cases were run based on saucer and aperture diameters of 40, 60, and 80 meters with a 100-kilogram payload floating at a cruise altitude of 22 kilometers. Our research and preliminary analysis yields HALAAV designs that appear realistic in size, with acceptable antenna hull surface tolerances, and performance characteristics. The designs appear technically feasible within the next several years, leveraging on currently available and extrapolated materials and inflatable structures technology.

Conceptual illustration of HALAAV GPR

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