Dennis L. Kern

Implementation of a Whole Spacecraft Isolation System for the OSTM/Jason 2 Mission

The OSTM/Jason 2 mission will be the lightest payload to ever launch on a 2-stage Delta II 7320-10 launch vehicle. The moment-based lateral loads predicted for this launch configuration significantly exceed the qualification history of the inherited spacecraft bus. Additionally, payload sine vibration requirements for this launch configuration exceed the OSTM/Jason 2 spacecraft and equipment sine vibration qualification heritage. It was not possible to appreciably enhance the structural capability of the Jason 2 spacecraft, therefore a feasibility study of various potential approaches for mitigating the launch loads was conducted. A CSA Engineering, Inc., SoftRide whole spacecraft isolation system was chosen for implementation on the OSTM/Jason 2 mission based on probability of meeting the load mitigation criteria and cost and schedule considerations. This paper provides a) an overview of the study that resulted in selection of the SoftRide system, b) the design, analysis, and test process for the SoftRide system, along with some of the design issues and their solutions, and c) a summary of a KSC/JPL independent evaluation of the risks associated with the SoftRide program. The SoftRide solution for OSTM/Jason 2 allowed demonstration of the adequacy of the heritage qualification for the launch configuration.

Vibro‐acoustic analysis of aerospace structures and issues with the available commercial prediction tools.

The results of vibro‐acoustic modeling using the boundary element method (BEM) that predicts the acceleration responses at critical locations and at the interfaces of selected test articles are discussed. High fidelity acoustic tests were performed in a couple of cases and the results are used to validate the BEM predictions. The accuracy of the BEM and its ability to correctly predict the acceleration responses of lightweight structures are discussed in some detail. Also a combined system level BEM, consisting of structures very responsive to acoustic pressures, and force‐limited base shake random vibration analysis was performed. We will discuss how these results may be used to derive random vibration specifications for the purpose of qualifying large and lightweight structures for flight. In this paper, we also discuss the commercially available vibro‐acoustic tools that are used to predict the acoustic transmission losses and vibration responses of flight structures for lift‐off (assumed to be diffuse...

Noise Environment Reduction Foam Spheres in Space

The advent of lightweight fairings for new spacecraft and the increased thrust of new launch vehicles have intensified the need for better techniques for predicting and for reducing the low frequency noise environment of spacecraft at liftoff. This paper presents a VAPEPS (VibroAcoustic Payload Environment Prediction System) parametrical analysis of the noise reduction of spacecraft fairings and explores a novel technique for increasing the low frequency noise reduction of lightweight fairing by approximately 10 dB.