High-Altitude Long Endurance

High-Altitude Long Endurance (HALE) is the description of an air-bourne vehicle which functions optimally at high-altitude and is capable of flights which last for considerable periods of time without recourse to landing.

The Tropopause represents high-altitude.

The idea of HALE was acknowledged in technical papers as early as 1983, with A preliminary study of solar powered aircraft and associated power trains written by D.W. Hall, C.D. Fortenbach, E.V. Dimiceli and R.W. Parks (NASA CR-3699), the actual state of affairs within technology of a time during the 1970s, allowed for scientists to later consider the possibility of Long endurance flight as a conceivable inclusion to aviation of suborbital spacecraft. One of the first papers to explicitly mention Long Enduarnce is J.W.Youngblood, T.A. Talay & R.J. Pegg Design of Long Endurance Unmanned Airplanes Incorporating Solar and fuel cell propulsion, published 1984. An early paper which incorporates both high-altitude and long-endurance as the area of investigation, is M.D. Maughmer (University Pennsylvania State) and D.M. Somers (NASA Langley) Design and experimental results for a high-altitude, long-endurance airfoil. The authors state interest in development of such a craft lay in the need to fulfill communication relay missions, weather monitoring, and to obtain information for the targeting of cruise missiles. This paper had a publication within the year 1989.

The research paper, 2025, written by B.W. Carmichael (Colonel), and Majors, T.E. DeVine, R.J. Kaufman, P.E. Pence and R.E. Wilcox, and presented July 1996, foresaw routine HALE-UAV operations happening within the early 21st century. In contemplation of a future of the military, projected to 2025, the authors thought a HALE in flight for 24 hours. Long endurance ("long-loiter") is held synonymous with the concept of maintaining air occupation, "the ability to hold an adversary continuously at risk from lethal and non-lethal effects from the air".

The Defense Airborne Reconnaissance Office at some time made demonstrations of long-endurance UAV craft.

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