High Altitude Long Endurance Research Articles

Impact of solar storms on high altitude long endurance unmanned aircraft and airship design and operations

AbstractThis paper applies existing information on solar storms to unmanned aviation; no new research data is presented. The purpose of this paper is to alert the unmanned aviation community to the potential hazards posed by solar storms, to familiarise it with the effects of solar storms and how to mitigate them, and to encourage research on solar storm effects on high altitude long endurance (HALE) aircraft and airship design and operations. As unmanned aircraft and airships move increasingly into high altitude (50,000+ft), endurance (24+ hr) roles, they will become vulnerable to the effects of space weather, specifically that of solar storms. Although solar storms are commonly associated with their impact on satellites, they affect the routing and timing of airline flights flying for six to eight hours at 30,000 to 40,000ft. Operating twice as high and with flight times twice as long (or longer) than those of airliners, HALE aircraft and airships occupy a middle zone of vulnerability, being more so than airliners but less so than satellites. A key difference however is that satellites are designed for space weather, whereas some current HALE vehicles are not. The paper concludes that unmanned HALE aircraft and airships can be one to three orders of magnitude more vulnerable to solar storms than a trans-Pacific airliner.

AIS and Long Range Identification & Tracking

This paper describes the United States Coast Guard's efforts regarding Long Range Identification & Tracking (LRIT) of ships. Among those elements included in the LRIT plan, automatic identification systems (AIS), typically envisioned as a short-range system, may also play a long-range role. AIS vessel tracking may be accomplished through high elevation shore sites allowing reception of AIS signals to nominally 24 nm that loosely puts it in the category of a short-range sensor. Additionally, the US Coast Guard is conducting research and development efforts to determine the feasibility of using AIS receive capability on low earth orbit (LEO) satellites and high altitude, long endurance (HALE) airships or balloons. In parallel with the developing technical capabilities, the US approach with the International Maritime Organization (IMO), and domestic legislation and regulations are also addressed. Finally, a vision for the implementation of LRIT is offered. The paper was presented on 9 November 2004 at Church House, London during the Institute's NAV 04 Conference.

Aerodynamic design assessment of Strato 2C and its potential for unmanned high altitude airborne platforms

Currently, there is a large interest worldwide in the development of High Altitude Long Endurance (HALE) Unmanned Aerial Vehicles (UAVs) for a number of civil and military missions, such as routine weather reconnaissance, surface reconnaissance (forest fires, etc.), earth observation, border patrol and monitoring, fisheries and wildlife refuge management, chemical and biological agent detection, law enforcement, disaster assistance and monitoring, telecommunications relay, movie production, agricultural surveying and control, and provision of targeting information. Passenger and transport airplanes operate at cruising altitudes of maximum 12 000 m where the density is about 25% compared to sea level. HALE-UVAs are foreseen to operate in the stratosphere at altitudes of 24 000 m, twice as high, where the density drops to about 3.6% of the sea level value influencing the lift of the aircraft strongly. The environmental conditions in such altitudes pose strong requirements for the aerodynamic layout and the power plant of an aircraft. In Europe Strato 2C – a manned civil research aircraft – was until nowadays the only aircraft which reached altitudes above 18 000 m. In this paper Strato 2C's aerodynamic design and propulsion layout will be presented and critically reviewed for its suitability for these high altitudes.

Nonlinear Aeroelasticity and Flight Dynamics of High-Altitude Long-Endurance Aircraft

High-Altitude Long-Endurance (HALE) aircraft have wings with high aspect ratios. During operations of these aircraft, the wings can undergo large de∞ections. These large de∞ections can change the natural frequencies of the wing which, in turn, can produce noticeable changes in its aeroelastic behavior. This behavior can be accounted for only by using a rigorous nonlinear aeroelastic analysis. Results are obtained from such an analysis for aeroelastic behavior as well as overall ∞ight dynamic characteristics of a complete aircraft model representative of HALE aircraft. When the nonlinear ∞exibility efiects are taken into account in the calculation of trim and ∞ight dynamics characteristics, the predicted aeroelastic behavior of the complete aircraft turns out to be very difierent from what it would be without such efiects. The overall ∞ight dynamic characteristics of the aircraft also change due to wing ∞exibility. For example, the results show that the trim solution as well as the short-period and phugoid modes are afiected by wing ∞exibility.