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Project Final Report – CUDBF April 30 th , 2009 ASEN 4028: Aerospace Senior Projects 13.0 Verification and Validation Author: Ben Kemper Co-Author: Ross Defranco 13.1 Subsystem Verification and Validation 13.1.1 Missions Subsystem Verification and Validation 13.1.1.1 Release Mechanism Testing Both the wing stores and the centerline store needed to be tested for 95% deployment reliability. Payload release testing consisted of loading the rockets and releasing the rockets remotely repeatedly. Each individual release mechanism was fully tested as a subsystem before it was integrated into the Buff-2B and Buff-2C models. Further testing was done to ensure release reliability for both store types by loading them rapidly and then releasing them with only the powered servos, PIC, and transmitter. Both types released reliably on 25 out of 25 attempts after construction, validating the 95% release rate. After further wear and testing, the Kevlar string connecting the servo on the left outboard wing release mechanism broke. This required cutting into the aircraft for repair. After further testing and analysis, it was determined the CA used to secure the string to the metal pin made the single strand of Kevlar brittle and more likely to snap. This was redesigned on the Buff-2C model by using a screw so that CA was not required and braiding 3 strands of Kevlar together. Strings were seen to stretch initially after use on the Buff- 2C model (one requiring tightening), but broken strings never again occurred. It was also important to ensure that the stores would remain fixed to the aircraft during flight. This was first tested on the ground by performing shake tests on both the aircraft and stores and 130
Project Final Report – CUDBF April 30 th , 2009 ASEN 4028: Aerospace Senior Projects pulling/pushing on the store in each of the 6 coordinate directions. When properly loaded, the final payloads remained fixed to the aircraft throughout all of these conditions. The centerline store offered slightly more free-play than the wing mounted stores, but was determined to be safe and acceptable for flight on the C model. The centerline store on the B model had added foam inserts to prevent possible free-play during flight. In all, the final integrated release system proved reliable for release and attachment. 13.1.1.2 Aircraft Container Drop Testing Both the foam box and balsa isogrid box were dropped multiple times in order to verify the 6 inch drop requirement. Both boxes were loaded with all contents, lifted such that no part of the box was below 6 inches, and released. Following each test, both boxes were inspected for structural damage and the contents were checked to make sure nothing shifted during the drop. Both boxes were dropped 7 times over the course of the project and at least once on each side. For the foam box, the only visible damage to the box was foam compression on the surface. This damage was superficial and not structural. Similarly, the balsa only experienced surface scratching due to the concrete surface the box was being dropped on. Again, the box did not sustain damage and its contents did not shift. An inspection of the container’s corner can be seen in Figure 111. Figure 111: Inspect of the Isogrid Box Structural Corner after Drop Test 13.1.2 Propulsion Subsystem Verification and Validation 13.1.2.1 Static Thrust Testing Static thrust testing was conducted in order to ensure the aircraft had sufficient power to make the 100ft takeoff with the heaviest payload. No values were predicted before this test because of the known inaccuracy in the program Electricalc (the program used to determine the static thrust). Instead, the purpose of this test was to experimentally measure static thrust as a function of power draw for different diameter and pitch propeller sizes. No propellers less than 12” in diameter were tested because the ground clearance provided for the water bottle allowed for a 131
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University of Colorado Design/Build
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PFR - Aerospace Engineering Sciences Senior Design Projects ...

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