ASCI 530 Blog Post 2: Weeding Out a Solution

     A hypothetical UAS has been designed for precision aerial application of fertilizer, however it is overweight. The offending subsystems are Guidance, Navigation, & Control (GNC) and the payload delivery system. In the current state, the vehicle will not be able to meet the advertised performance without using fuel reserves.

Solution

     The first step to solving the problem should be a relatively quick assessment of the GNC and payload systems to find obvious weight penalties associated with the off-the-shelf hardware. This could be as simple as a lighter enclosure for GNC avionics or removing excessive hardware or material from the spray system. Assuming there are no simple solutions, the systems engineer (SE) should take a holistic approach. While GNC and payload may have exceeded their estimated weights, the solution should not necessarily be limited to those areas as they might currently be the most economic designs. Each subsystem team should be directed to identify at least two ways to save weight, the associated cost, and any negative effects. For example, replacing the landing gear wheels with skids may save weight at a low cost, but pass on higher maintenance costs to the user if the skids wear faster than tires. The SE should evaluate the compiled list of ideas and select one or a blend of ideas that incur the least cost to the company while minimally impacting the overall vehicle characteristics.

Table 1. Example of total system cost-benefit analysis for reducing vehicle wight.

     In this example scenario the SE analyzes the benefits of the potential solutions. Removing the battery backups appears to have the best cost-benefit ratio, however a loss of control resulting from an engine-out situation may present unacceptable risk to users or fail to meet certification standards. Similarly, removing heat sinks from computer processor boards may impose constraints in hot weather climates. The SE could also select multiple solutions such as the landing gear skids and thin walled fertilizer tank to meet the design goal.

     For future iterations of this UAS the company should implement three additional practices. First, a requirements-based design process should be used, which will ensure traceability of all configuration choices back to a verified need from the customer (Loewen, 2013). This is directly tied to the second practice of gathering operational data from the current UAS and conducting user surveys. The database can be used to determine requirements for follow-on systems, complete cost-benefit analysis as a function of market demand, and make appropriate sacrifices in the event testing reveals deficiencies. Since the payload versus range problem is critical for the aerial application UAS, the company should also construct a payload-range diagram. This will assist marketing personnel and customers in understanding the capabilities of the vehicle (Ackert, 2013).

Figure 1. Example of a Range-Payload diagram. Reprinted from Aircraft Payload‐Range Analysis for Financiers, by S. Ackert, 2013. Copyright 2013.

     If a range-payload diagram had been drawn for the current UAS design, it might have shown that the performance was acceptable under certain situations (consistent with the marketing campaign) or guided better decision making. For example, if the demonstrated range was found to be between Point B and C in Figure 2, and the results of a market survey yielded few users needed ranges greater than Point B, than perhaps fewer, if any, changes could be made.

Conclusion

     This essay has briefly explored the crisis that ensues when testing reveals serious design deficiencies. A typical cost-benefit example was provided to aid configuration change decisions. Additional recommendations were also provided for future projects.

References

Ackert, S. (2013). Aircraft Payload-Range Analysis for Financiers. Retrieved October 30, 2016, from http://www.aircraftmonitor.com/uploads/1/5/9/9/15993320/aircraft_payload_range_analysis_for_financiers_v2.pdf

Loewen, H. (2013). Requirements-based UAV Design Process Explained. Retrieved October 30, 2016, from https://www.micropilot.com/pdf/requirements-based-uav.pdf

ASCI 530 Blog Post 1: A Short Historical UAS Example

Unmanned aerial systems (UAS) have been in development in the U.S. nearly as long as manned aircraft. A main theme is that the vehicles were intended to replace humans to accomplish missions that are dangerous. The following essay will analyze the Ryan Firebee variants and how they evolved over time.

Ryan Firebee

The Teledyne Ryan Firebee UAS includes a variety of jet-powered vehicles built from 1948 to 1982. The first model production model, the Q-2, was designed as an aerial target for the U.S. Air Force, Army, and Navy who needed to train for emerging jet fighter and cruise missile threats (Parsch, 2003). It could be launched from the air via an A-26 or C-130 host aircraft, or static launched from the ground with an expendable solid rocket motor. At the end of the mission, the vehicle would deploy a parachute and recovery trapeze that could be caught in mid-air by a suitably equipped helicopter, or splash down into water for pickup. By 1963 the Firebee had been redesigned the A/BQM-34 series, which included models that performed from 10 to 60,000 feet up to Mach 0.96 (Tarantola, 2013). Beginning in 1953, a supersonic Firebee II (BQM-34E) was developed to simulate high-speed fighter aircraft for anti-aircraft system testing. The typical Firebee endurance was 90 minutes, but most variants could be equipped with external drop tanks. They could be launched on pre-programmed missions or directly controlled using a line-of-sight link with a range of 300 miles, where operators set goals (ex. 7G level turn) and were provided basic vehicle state data.

Expanding Missions

Realizing that the Firebee line was capable of more, the Air Force began developing a reconnaissance version in 1963. Designated the AQM-34, they completed approximately 34,000 missions over the Vietnam conflict zone with optical sensors or electronic warfare packages (Tarantola, 2013). An advanced signals collection version was also deployed over North Korea from 1970-1973 that provided an unprecedented seven hours of loiter time at 75,000 feet.

Recent History

Although the Firebee production line was closed in 1983, the aircraft were the main target decoy until fielding of the BQM-167 in 2002. These later models featured towed flare decoys for heat-seeking missiles and emitters that simulated the radar signatures of a wide variety of threats (Parsch, 2003). Global Positioning System receivers were also installed to increase navigation accuracy. Of nearly 7,000 Firebees built, the remaining 250 were reserved for research, development, and special activities. In 2003, BGM-34Ls were used during the opening air attacks over Iraq, where they were used to dispense radar-spoofing chaff and employ jamming ahead of manned coalition aircraft (Tarantola, 2013). In 2005, Northrop Grumman was awarded a contract to modify the remaining Firebee systems for advanced decoy and payload dispensing operations (Morris, 2005).

Conclusion

This short essay has analyzed the Ryan Firebee, from its inception as a simple aerial target drone to its role as a modern surveillance and electronic attack platform. While the variants shared generally the same airframe and physical performance, the models developed over 5 decades were significantly improved with state-of-the-art technology. Overall, the systems provided an impressive 83% recovery rate and ensured valuable capabilities were available to the U.S. military. The Firebee system represents a success story in the flexibility and capability of UAS.

References

Tarantola, A. (2013, August 27). The Ryan Firebee: Grandfather to the Modern UAV - Gizmodo. Retrieved October 23, 2016, from http://gizmodo.com/the-ryan-firebee-grandfather-to-the-modern-uav-1155938222

Morris, J. (2005, August 18). Firebee target has first flight with modernized avionics. Retrieved October 23, 2016, from http://search.proquest.com

Parsch, A. (2003). Teledyne Ryan AQM/BQM/MQM-34 Firebee. Retrieved October 23, 2016, from http://www.designation-systems.net/dusrm/m-34.html