Redesign to Reduce Mass: Wallops Arc-Second Pointer (WASP)

Open Access
Author:
Gibbons, Caitlin Elizabeth
Area of Honors:
Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Sean N Brennan, Thesis Supervisor
  • Zoubeida Ounaies, Honors Advisor
Keywords:
  • Mechanical Engineering
  • Design
  • Autodesk Inventor
  • Abaqus
  • FEA
  • Balloon
  • Platform
  • Telescope
  • Pointing System
  • NASA
  • Structure
Abstract:
Scientists have used balloons to study earth for a long time now; however, the Wallops Arc-Second Pointer (WASP) is a significant advancement to present pointing apparatuses for planetary scientists in particular because they require a highly stable pointing system to accurately track planetary targets as they move in the solar system. Additional examples of objectives include exoplanets and X-ray sources outside the solar system. WASP is an innovative and standardized system that can accurately point a balloon payload within a sub arc-second; 70o in the pitch direction and 15o in the yaw direction. WASP has successfully completed three test flights, in 2011, 2012 and 2013. WASP is already a completely functional and operating system, however the Balloon Program Office (Code 820) and the Mechanical Systems Branch (Code 548) at the National Aeronautics Space Administration (NASA) Wallops Flight Facility (WFF) would like to improve upon the original structure. The current version of WASP weighs approximately 600 lbm. NASA WFF intends to reduce the weight the pointing system by at least a 100 lbm, while maintaining the original strength and stiffness. Reductions in weight will allow project scientists to incorporate additional instruments to a payload, or by flight operations for a longer duration flight. The end goal of redesigning WASP is to create a system that will be included in a standardized balloon platform for earth science, planetary science, and for proposals such as the Gondola for High Altitude Planetary Science (GHAPS) project. The thesis details the research conducted, redesign decisions for WASP, a suggested assembly procedure for the inner frame of the WASP, finite element analysis (FEA) conducted on the inner frame, and recommendations for moving forward. The redesigned version of WASP is 161 lbm, or 31% lighter than the original design. The redesigned WASP inner frame utilized standard off-the-shelf extrusions to maintain cost-effectiveness. FEA was conducted using Autodesk Inventor Pro and Abaqus. The stress analysis tested the redesigned version under an applied load of 1,500 lbf loading with a factor of safety of 10 (15,000 lbf load), to ensure that the structure would not experience ultimate failure. The analysis using Inventor demonstrated that there was a 13.5% difference between simplified hand calculations and the FEA. The percent difference between the Abaqus FEA and the hand calculation was approximately 2.4%. The redesigned WASP met all the project requirements, and was approved for manufacture by the NASA WFF Mechanical Systems Branch engineers and technician.