Advanced Methods

ASD engineers have pioneered/developed major advancements in linear and nonlinear structural dynamics that have been adopted by NASA, DoD, major contractors, and commercial finite element programs. These advancements include:

• Pioneered Improved Launch Vehicle/Launch Pad Separation Analysis:

  The highly utilized Henkel-Mar pad separation (see ASD Journal Publications) method is a multibody method capable of accurate predictions of launch vehicle/launch pad separation transient force time-histories.
  • Utilized by major launch vehicle programs including the Space Shuttle, Titan, Atlas, Delta, and new programs such as the Space-X Falcon
  • Incorporates launch vehicle/launch pad lateral force decay to longitudinal separation force decay with the Majed-Henkel extension (see ASD Papers)

• Pioneered Nonlinear Trunnion Friction Transient Coupled Loads Analysis:

  This nonlinear analysis method incorporates sliding component interface surface stick/slip transients affects due to sliding and static friction forces (see ASD Journal Publications).
  • Utilized on mission critical Verification Loads Cycles for Air Force payloads manifested on the Space Shuttle

• Pioneered Significantly Improved Transient Deadband Coupled Loads Analysis:

  This nonlinear analysis method was developed to account for component interface deadbands (or rattle space). Such interface deadbands are common on spacecraft components involving mechanical coupling systems, e.g., robotic deployment systems. Typical deadband size in these systems have proven to be a significant contributor to the components’ transient launch environments.
  • ASD’s nonlinear deadband CLA capability selected by NASA and Lockheed Martin for Space Shuttle/International Space Station mission critical coupled loads analyses
    • Other commercially available methods resulted in “unrealistic” transient time-histories
  • Implemented within ASD’s software tool, ASD/CLAS
  • Commercial Orbital Transport Services (COTS) expected to utilize similar deadband component interfaces as the Space Shuttle/International Space Station systems

• Pioneered Residual Flexibility Mixed Boundary Component Dynamic Math Model Reduction Method:

  The RFMB method (see ASD Journal Publications) exactly reduces to Hurty/Craig-Bampton for the all-fixed boundary case, to Rubin’s method for the all-free boundary case, and handles all mixed boundary cases with extreme efficiency, rapid convergence and accuracy.
  • Adopted by NASA and major contractors and utilized on Shuttle linear and nonlinear verification loads cycles
  • Adopted by major finite element programs including MSC/NASTRAN as default

• Developed Generalized Random Vibration Mass Attenuation Method (see ASD Papers):

  A rational and formalized approach to random vibration mass attenuation has risen to a level of urgency within the NASA’s Constellation Program. The NASA Engineering and Safety Council (NESC) has undertaken the task of developing improved mass attenuation methodologies. The ASD generalized mass attenuation approach simultaneously accounts for all component interface degrees of freedom, with specified correlations, and produces attenuated accelerations at each component interface degree of freedom along with the resulting cross-correlations. This ASD method reduces to Barrett’s for the rigid component case and Norton-Thevenin method for single drive degree of freedom case.
  • Produces highly physically realizable results even for the most complex analytical cases
  • Future correlation to involve comparison of analytical results to NASA/JPL acoustic test
  • Method and results to be made available by the NESC
    • ASD is team member on the NESC Loads & Dynamic Technical Discipline Team and a member of the NESC Vibroacoustic Best Practices Group that is leading this effort