CRM has an experienced structural dynamics staff currently on contract to perform all internal acoustic and vibro-acoustic predictions for the adapter section of the Space Launch System which connects the core stage to the upper stage. Additionally, structural dynamics responsibilities include creation of a coupled loads model for the stage adapter.

Vibroacoustics

During liftoff and ascent phases, launch vehicle structures experience acoustic excitation that drive the random vibration of the primary structure and any attached secondary structures. CRM Solutions has the expertise and capability to predict random vibration environments using NASTRAN finite element modeling to characterize the structure and VA-One to model the fluid-structure interaction. In addition to finite element modeling, techniques are used by CRM to levy legacy flight data and scale measured random vibration levels to predicted levels for a new design.

CRM has expertise accurately modeling today’s complex launch vehicle designs using FEA and SEA capturing the transmission loss characteristics of the primary structure. CRM has successfully validated VA-One’s hybrid transmission loss capability by comparing analysis results to measured data for isogrid panels leveraging periodic modeling techniques. See the link below for a presentation given by CRM at the 2016 Spacecraft and Launch Vehicle Environments workshop.

http://aerospace.wpengine.netdna-cdn.com/wp-content/uploads/conferences/SCLV2016/Harrison_Justin.pdf

CRM solely produced estimated random vibration levels for the Launch Vehicle Stage Adapter (LVSA) for the NASA Space Launch System (SLS) rocket (Figure 1). Along with general random vibration environment predictions, our expertise teamed with designers to tailor individual component hardware so not exceed certain random vibration levels during all phases of flight. Furthermore, CRM works with the stress team in determining dynamic load factors for secondary structure stress analysis.

Finite Element Model

NASA SLS Launch Vehicle Stage Adapter VA-One Model

Skin Mounted Component Mode Shape

CRM Solutions leads the analysis on the NASA SLS launch vehicle stage adapter (LVSA) for internal acoustics and random vibration.

Internal Acoustics

CRM Solutions, Inc. is experienced in internal acoustic environment predictions for launch vehicles. CRM utilizes VA-One along with company developed tools to predict the reduction of sound pressure levels through vehicle primary structure as well as acoustic blankets. Below is an illustration of the ability of VA-One to accurately predict the transmission loss of an isogrid aluminum structure. The VA-One transmission loss predictions were compared to results published by D.R. Lorch in 1980.

Lorch vs VA-One Transmission Loss Comparison

Random Vibration

Modeling of Coupled Fluid-Structure Systems
CRM Solutions is experienced with the generation and use of analytical models to predict the random vibration environments for launch vehicle’s primary and secondary structures. Modeling capabilities currently utilized by CRM are statistical energy analysis (SEA), the boundary element method (BEM), the finite element method (FEM), and hybrid methods which can combine the three methods in order to take advantages of each methods strengths.
CRM Solutions can predict random vibration environments for both liftoff and ascent aeroacoustics environments.

LVSA Low Frequency Regime Finite Element Model