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1.1 Overview
Unmanned Aerial Vehicles have become the epicenter of the aerospace industry in the past few decades. This is because of the yields they provide over the manned aircrafts. This class of aircrafts have shown their diversity of applications in military as well as private sectors. In that the current focus is on High Altitude, Long Endurance UAVs.
HALE systems can be lighter-than-air (LTA) vehicles such as balloons or heavier-than-air (HTA) such as UAVs. In order to focus the research of this project, this thesis will be only centered on UAVs.
HALE UAVs are aimed to endure long periods of time in flight i.e endurance, some systems can reach up to 14 days of continuous operations. These systems also have the ability to fly at high altitudes which enables them to cruise above the commercial airliners, thus, giving it the satellite like endurance, and a greater perspective of large areas of the earth surface. Moreover, these systems can be landed. This feature enables users to promptly introduce innovation and refurbishments when needed.
This capability allows UAV to have a more responsive prospect than satellites, as they can be dispatched and landed in much shorter periods of time.
As explained previously, there are two basic characteristics that an UAV has to comply with in order to be fit for military operational environment. These are long flight endurance, high altitudes, and low cruise speeds. Systems complying with these criteria are presented in subsequent paragraphs.
1.2 A Review of Existing HALE Systems
The Zephyr 7 from Airbus Defense and Space is a solar-electric aircraft. It set a duration record for UAVs with a continuous flight of 14 days. It flies exclusively on solar power, and its able to fly autonomously for months at 19000m. Currently, the payload capabilities are small but the next generation is expected to have increased payload mass. Its specifications are mentioned below.
o Payload mass: 5kg;
o Endurance: 14 days;
o Max altitude: 21 562m
The Global Observer from AeroVironment is a HALE unmanned aircraft system (UAS) capable of combining satellite-like capabilities with the advantages of aircrafts. It is expected to be used for the following missions, communications relay, disaster response, maritime operations.
Its specification are the following
o Payload mass: 181.5kg;
o Endurance: 4-6 days;
o Max altitude: 16 764m
1.3 Need of HALEs in Military Environment
Greater area footprint. The foremost advantage of being flying at high altitude of 20km range is gaining access to a larger area footprint. Which means surveillance and intelligence generation of a larger area can be achieved in a shorter span of time, without physically flying UAV over all places of interest.
Safe from enemy radar and Air Defense System. With flight regimes at such high altitudes the detection probability of UAV from enemy radars and targeting ability using air defense systems reduces significantly. Even these altitudes make these UAVs safe from hostile fighters. Fighter aircraft cannot operate sustainably at these altitudes in order to engage HALE UAVs.
In contemporary changing military operation environment satellites are prone to hostile activities. Those could be passive as well as physical destruction of satellites to make a loss to nation. In such scenario these HALE systems can act as active back up systems for satellites for restoring communication, remote sensing etc.
Add ons— masala from haps
—- disadvantes of high alti flying
