Original Authors: Matthew Del Giorno, Rafiq Madarshah, Andy Miller, Taylor Presley, Christopher Rose, Andrew Shields, Dhruv Vasant
The following is a hypothetical scenario.
The Petroleum Pipeline Consortium is seeking to deploy an unmanned aircraft to monitor and inspect a 100-mile stretch of pipeline over rural South Dakota. The system will utilize a TASE 400 gimballed camera to collect aerial imagery of the pipeline to inspect the system.
Using a small UAS (< 55 lbs gross takeoff weight), data will be collected at 3,000 ft AGL at a true airspeed of 50 KTAS. The Consortium is open to either a reciprocating engine or electric propulsion, but it must have sufficient range and endurance to complete the mission (200 miles round trip) with a single flight.
The system should utilize a vehicle-based launcher for takeoff and conventional landing gear for landing from an airport runway. The runway is 3,300 ft in length and 60 ft wide. Its local elevation is 850 ft. Also note, the elevation change along the pipeline is negligible.
Please note: this location is simply conceptual; there is no suitable airport near the end-points of the flight path as shown.
It is my intent to create a preliminary design of the airframe and the propulsion system based upon the specifications included above.
System Overview
The system designed for the Pipeline Consortium is a small UAS with a gross take-off weight of less than 55lbs. This will carry the TASE 400 camera to inspect the pipeline per the Pipeline Consortium’s requirements. The UAS will use a flight controller to ensure autonomous operation, reducing the workload for Pipeline Consortium’s employees. The system will also use electric propulsion to complete the mission and power the camera and onboard systems.
Requirements
For this aircraft, the client has specified the following requirements:
- The UAS shall have a gross takeoff weight of less than 55 lbs.
- The UAS shall be equipped with a TASE 400 gimballed camera.
- The UAS shall be capable of flying at an altitude of 3,850 ft above MSL.
- The UAS shall be able to fly at a true airspeed of 50 KTAS.
- The UAS shall be powered by either a reciprocating engine or electric propulsion system.
- The UAS shall have a range of at least 200 miles in a single flight.
- The UAS shall be able to take off from a vehicle-based launcher.
- The UAS shall be capable of landing using conventional landing gear on an airport runway that is 3,300 ft long and 60 ft wide.
UAS Trade Study
The AeroVironment Puma 3 AE and the Applied Aeronautics Albatross are two small commercial UAS aircraft studied to determine their compatibility with the client requirements.
The AeroVironment Puma 3 AE is a small, lightweight UAS that uses a small electric motor for propulsion. It is light weight at 15 lbs and would allow it to carry payloads such as the TASE 400 gimballed camera without exceeding the 55 lbs weight limit for the first requirement. The Puma 3 AE can fly at altitudes of up to 10,500 ft above sea level and reach speeds up to 40 knots. Its endurance is up to 2.5 hours, the limiting factor for the required 200-mile mission. However, with battery upgrades, potentially as a third party component in the transit bay, its endurance could potentially be extended to meet the mission requirements.
The Applied Aeronautics Albatross is a high-performance electric UAS with impressive endurance and range capabilities, making it a potential fit for the Pipeline Consortium’s requirements. It has an electric motor and boasts an endurance of up to 4 hours and a range of up to 250 km on a single battery charge. It features a modular design for easy payload integration, such as the TASE 400 gimballed camera, and its gross takeoff weight (10+ kg) is under 55 lbs, fitting the requirement. The Albatross’ cruise speed of 30–40 KTAS (68 km/hr) falls within the Consortium’s requirements however, the rated operating altitude could not be found. It boasts a max speed of 70 KTAS (129 km/hr). The albatross can takeoff and land within the Consortium’s requirements. Its 3 m wingspan and 30:1 ratio make it very efficient for this mission.
Considering the requirements specified by the Petroleum Pipeline Consortium, the Applied Aeronautics Albatross is the most suitable option for several reasons:
- Endurance and Range: The Albatross has the highest endurance among the 2 UAS (up to 4 hours), which is crucial for covering the 200-mile round trip distance. Its specified range is the highest among the options and could potentially be extended with additional batteries or efficiency improvements.
- Gross Takeoff Weight and Payload Capacity: The Albatross has a gross takeoff weight under 55 lbs, meeting the requirement. It also has a high payload capacity which could accommodate the TASE 400 gimballed camera with ease.
- Cruise Speed and Maximum Speed: With a cruise speed between 30 and 60 KTAS, the Albatross can meet the requirement of 50 KTAS and still adjust its speed as necessary during the operation.
- Operational Altitude: The Albatross may or may not be able to operate at the required 3,000 ft AGL. However, this might be a constraint that can be overcome through further discussions with the manufacturer or operational adjustments.
Despite the slight mismatch in operational altitude and the need for an extended range, the Albatross, with potential modifications, is well-suited to meet the mission requirements of monitoring and inspecting a 100-mile stretch of pipeline. Its electric propulsion system, impressive endurance, speed capabilities, and payload capacity make it the best choice among the UAS aircraft considered.
Design specifications of both the Puma 3 AE and the Albatross are given in Table 1. Please note the assumed and estimated values are based on general design characteristics and limited available data.
Airframe Design and Performance
Based on the information obtained from the trade study, it has been determined that a high aspect ratio and long wingspan will provide this aircraft with sufficient aerodynamic performance required to carry the TASE 400 at an altitude of 3850 ft MSL. Because this aircraft must be launched from a launcher, an aspect ratio of 9 was chosen. This aspect ratio should make the wing robust enough to survive the forces involved in repeated launching, yet still efficient enough to complete the mission.
With this planform design and the following assumed constants, the aerodynamic characteristics (lift, drag, and stall speed) have been analyzed at altitudes ranging from 0 ft to 5000 ft.
Using the drag numbers provided, as well as assuming an additional factor of 1.4 on the thrust needed, the propulsion system can be sized. The first step was to use the actuator disk model to get an estimated size of the motor in horsepower and watts, as well as the power required at Sea Level.
To provide the required thrust, the team elected to use an electric propulsion system for simplicity and due to the similar UAS aircrafts discussed above also utilizing electric propulsion. Due to the large remote control aircraft hobby, there are a number of available motors that meet these power needs, the specifications for a few are listed below in Table 6: Motor Candidates.
Once the candidate motors had been found, matched propellers for them were selected. The selected motor was the Scorpion SII-3032–880, with an APC 10 x 9 propeller and the Pixhawk 4 autopilot flight controller.
The next step was to evaluate the battery requirements for the UAS. Using the Scorpion SII-3032–880 capacity of a 4s Lithium-Polymer Battery (Lipo), a voltage of 16.8 volts can be used. Per the motor’s data sheet, power draw is approximately 40 amps at the RPM desired. To meet the mission requirements of a 240 nmi flight (200 nmi mission plus 20% reserve), and a 4.8 hour endurance 3 Maxxamps 62000 milliamp-hour 4s batteries will be used. These will be wired in series, to give a maximum range of 310 nmi, and an endurance of 6.2 hours. If only one battery is used, the range is 103 nmi, with a 2 hour endurance. The total weight of the battery is 29.6 pounds.
Final Design Specifications
Final design of the proposed aircraft will utilize an electric propulsion system and takes key notes from the UAS aircraft studied in the UAS Trade Study section above. The proposed UAS meets all Pipeline Consortium requirements with a range of 240 nmi, endurance of 6.2 hours, and autonomous abilities with the Pixhawk 4 flight controller. The final specifications for the Pipeline Consortium’s aircraft are shown in Table 7: Final Design Specifications.
