Uninhabited Air Vehicles: Enabling Science for Military Systems (2000)

Part II identifies technical needs and opportunities for research and development for major UAV subsystem technologies. The committee considered five areas in its analysis of air vehicle technologies: aerodynamics (and vehicle configuration), airframe (with a focus on materials and structures), propulsion systems, power and related technologies, and controls.

The committee used “notional vehicle types” as a way of identifying technical needs for applications ranging from replacing manned aircraft to performing unique missions. The committee identified three notional vehicle types as indicative of the range of technologies that would support general advances in the USAF’s capability of designing, producing, and fielding generation-after-next UAVs. The notional vehicle types were: (1) HALE (high-altitude, long-endurance) vehicles; (2) HSM (high-speed, maneuverable) vehicles; and (3) very low-cost vehicles.

Each notional vehicle type represents a class of vehicles, not a conceptual aircraft design suited to a particular mission. For example, the HALE class could include a reconnaissance air vehicle with an endurance of several days, as well as a very different vehicle with indefinite endurance.

The HALE vehicle type provided a focus on long-term technical advances for generation-after-next reconnaissance and surveillance aircraft. The key attributes of HALE vehicles will be operation at very high altitudes (> 65,000 feet) and long endurance (from days to “indefinite” duration). The committee believes that future aircraft intended to operate at altitudes above 65,000 feet will be

uninhabited, so the issues associated with the design and operation of these aircraft should be considered UAV-unique. The committee focused on high-altitude technologies, especially aerodynamics/vehicle configuration and propulsion systems. HALE vehicles would generally be flight configured, with an emphasis on structural efficiency (light weight) to provide endurance. Because of the lightweight structures and large wingspans typical of HALE vehicles, aeroelasticity is an important factor. HALE vehicles would be generally autonomous and programmable because a key reason for using UAVs for long-duration missions is to avoid operator fatigue and reduced vigilance due to monotony.

The HSM vehicle type provided a focus on potential second-generation UCAVs. The goal for HSM vehicles will be to conduct high-risk combat operations at a significantly lower cost than inhabited systems. Because the key consideration for HSM vehicles will be survivability, design trade-offs will include stealth and maneuverability versus speed, maximum altitude, and damage tolerance. HSM vehicles will generally operate in concert with other vehicles (inhabited and uninhabited) and will be responsive to changes in mission at the direction of a remote human operator. The cost of operations and logistics will be critical for the HSM vehicle type.

The very low-cost vehicle type was chosen to focus attention on trade-offs between cost and performance. Low-cost vehicles will be small, autonomous, and inexpensive. Operating in concert with other vehicles as a single distributed system, individual low-cost vehicles will not carry high-value payloads, and the loss of an individual vehicle would present a small threat of mission failure or collateral damage. Important attributes of low-cost vehicles will be vehicle configuration, which will depend on payload, structural design criteria, reliability after long-term storage, and low-cost manufacturing.