Unmanned Aerial Vehicle Technology

As manned aircraft missions become increasingly expensive and difficult to perform, alternative approaches are crucial to industry, government agencies, and the military. To answer these needs, Southwest Research Institute (SwRI) is developing new unmanned aerial vehicle (UAV) technologies to perform missions requiring long endurance and low observability and that entail extreme environmental exposure and high risk.

The Institute is a recognized leader in developing innovative aerial vehicles that successfully meet today's stringent requirements, including:

• Low program cost
  
• Minimal personnel risk
  
• Extremely high altitude
  
• Ultralight weight
  
• High maneuverability

SwRI's success in UAV technology is based on a multidisciplinary approach to problem solving. Comprehensive expertise in design, modeling, simulation, and prototyping enables the Institute to address UAV needs in:

• Vehicle design and development
  
• Propulsion systems
  
• Avionics & control system design
  
• Payload development
  
• Systems support

Vehicle Design and Development

Using state-of-the-art modeling capabilities and advanced computer-aided design techniques, SwRI engineers and scientists have developed a wide range of vehicle systems that meet the most demanding mission requirements. Institute engineers have successfully designed, integrated, and tested aircraft components and structures for UAV systems with capabilities that include:

Fixed-wing aircraft

• Short takeoff and landing requirements
  
• Extended mission duration
  
• Low-profile visibility
  
• Payload transport
  
• Servo modeling

As part of a team led by Alliant Techsystems, Inc., SwRI is participating in the development of the Outrider™ tactical UAV. The Institute is providing avionics, flight sensors, and autopilot software for the small, low-cost reconnaissance vehicle.

Powered parafoil

• Fully autonomous take-off and landing
  
• Global positioning system (GPS) waypoint-guided flight
  
• Extremely short takeoff and landing requirements
  
• Commercial off-the-shelf (COTS) components
  
• Low-cost operation
  
• Increased payload capacity for high-endurance missions
  
• Low-speed flight for high-resolution imaging
  
• Minimal noise

Lighter-than-air airship

SwRI developed this lighter-than-air airship to provide ultrahigh telecommunications relay support.

• Autonomous operation
  
• Extremely high altitude capabilities
  
• Long endurance
  
• Radio footprint with radius of approximately 300 miles
  
• Low observability
  
• Minimal mission support requirements

Propulsion Systems

SwRI engineers are developing lightweight, heavy-fuel engines for UAVs and other military applications. This engine, jointly developed with Evan Guy Enterprises, powers the Mission Technologies UAV shown in the inset.

Unmanned aerial vehicles require lightweight, low-maintenance, and reliable propulsion systems. To meet these challenging objectives, SwRI engineers have developed innovative engine and solar electric technologies. The Institute provides a full complement of propulsion and solar electric design and development facilities and expertise, enabling successful development of propulsion systems that include:

Internal Combustion Engines

• Wide range of fuels
  
  • Gasoline
    
  • Diesel
    
  • JP-8
    
• Various fuel systems
  
• COTS components
  
• Air-assisted in-cylinder technology
  
• Combustion systems
  
  • Diesel indirect injection
    
  • Spark-ignited gasoline
    
  • Spark-assisted diesel cycle
    
• Two-stroke, air-cooled configurations
  
• One-, two-, and four-cylinder engines
  
• Weight target of 1.5 kilowatts per kilogram

Solar Electric

This SwRI-developed solar panel provides the power for an electric motor-driven propeller during daylight hours. After dark, rechargeable batteries power the airship.

• Lightweight solar-electric power generation arrays
  
• Sun-tracking solar array pointing system
  
• Power and propulsion management controls
  
• Electric motor-driven propeller
  
• Thrust-vectored steering system

Avionics & Control System Design

Institute engineers have extensive experience in designing and building robust, lightweight flight control computers and communications systems for aerospace applications. By incorporating proven COTS technology into the UAV avionics and control systems, SwRI minimizes program costs, reduces maintenance requirements, and ensures on-time delivery. SwRI has successfully designed UAV avionics and control systems that include:

• Autopilot
  
• Payload data processor
  
• Emergency remote pilot
  
• Engine monitor
  
• Parachute control (steering)
  
• Payload release

SwRI engineers designed the Outrider™ avionics and control systems to use COTS PC104 circuits to allow the systems to operate under extreme environmental conditions (-40° to 70° C) without military specification components.

At higher atmospheric altitudes, environmental extremes require avionics that meet a broad range of temperatures and pressures. For a typical lighter-than-air airship, SwRI engineers design or procure avionics that include:

• Flight control processor
  
• Global positioning system
  
• Electronic compass
  
• Command and control communications
  
• Payload control and communications

SwRI has broad experience in using radio-frequency communications for command, control, and telemetry links.

Payload Development

Using SwRI's extensive and well-equipped laboratories, engineers developed and assembled this control and payload system as part of a concept assessment demonstration for the U.S. Marine Corps.

With more than 40 years of experience in electronic technology, SwRI designs and builds lightweight instruments that meet a wide range of commercial, military, and government mission requirements including:

Surveillance

• Infrared detectors
  
• Thermal imagers
  
• Visual cameras
  
• Communication intercept

Communications

• Cellular communications relay
  
• Radio relay
  
• Emergency communications link
  
• Optical communications
  
• Internet node
  
• Signal jammer

Scientific studies

• Mass spectrometer
  
• Gas analysis
  
• Telescopes
  
• Infrared and ultraviolet sensors
  
• Magnetometer
  
• Electromagnetic sensors

SwRI's rapidly deployable communications intelligence payloads address the challenges presented by the airborne UAV platform and airborne signal environment through the Institute's experience in:

• Broadband, high dynamic-range surveillance systems
  
• Multipolarization direction-finding (DF) algorithms for cluttered sites and multiple targets
  
• VHF/UHF payloads with COTS PC104 module-based hardware and software
  
  • VHF/UHF signal intercept
    
  • Frequency scan and search
    
  • Automatic signal recognition
    
  • DF and homing
    
  • Narrowband signal recording
    
  • Demodulated signal downlink
    
• Compact, rugged antennas and processing equipment development
  
• DF networks
  
• Full-scale and scale-model calibration
  
• Electromagnetic modeling
  
• Propagation studies

Systems Support

The Institute provides integrated logistic support and configuration management services to meet military standards and specific client requirements. These services include:

• Flight planning and operations
  
• Data analysis
  
• Regulatory compliance
  
• Maintenance and operational training
  
• Technical publications
  
• Drawings to customer specifications
  
• Spares provisioning

The ground station equipment for the lighter-than-air vehicle, consisting of a laptop computer, radio modem, and whip antenna, enable operating personnel to establish an off-site control center with minimal support equipment. An additional portable computer can be added to run a COTS mapping program.

To provide training support, SwRI staff members developed a real-time computer program simulator for fixed-wing aircraft that:

• Provides full six-degree-of-freedom movement
  
• Operates in software mode only or as hardware-in-loop
  
• Includes models such as:
  
  • Aerodynamics
    
  • Mass properties
    
  • Internal combustion engines
    
  • Propellers
    
  • Atmospheric conditions
    
  • Landing gear, servomotors, and sensors

This brochure was published in February 1999. For more information about unmanned aerial vehicle technology, contact Mike Ladika, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Phone (210) 522-2122, Fax (210) 522-3496.

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